Natural compounds: co-delivery strategies with chemotherapeutic agents or nucleic acids using lipid-based nanocarriers

Citation: Teixeira, P.V.; Fernandes, E.; Soares, T.B.; Adega, F.; Lopes, C.M.; Lúcio, M. Natural Compounds: Co-Delivery Strategies with Chemotherapeutic Agents or Nucleic Acids Using Lipid-Based Nanocarriers. Pharmaceutics 2023,15, 1317. https://doi.org/10.3390/ pharmaceutics15041317 Academic Editors: Ayan Kumar Barui and Susheel Kumar Nethi Received: 10 March 2023 Revised: 15 April 2023 Accepted: 20 April 2023 Published: 21 April 2023 Copyright: © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). pharmaceutics Review Natural Compounds: Co-Delivery Strategies with Chemotherapeutic Agents or Nucleic Acids Using Lipid-Based Nanocarriers Patrícia V. Teixeira 1,2,† , Eduarda Fernandes 1,† , Telma B. Soares 1, Filomena Adega 2,3, Carla M. Lopes 4,5,6,* and Marlene Lúcio 1,7,* 1 CF-UM-UP—Centro de Física das Universidades do Minho e Porto, Departamento de Física da Universidade do Minho, 4710-057 Braga, Portugal; [email protected] (P.V.T.); [email protected] (E.F.); [email protected] (T.B.S.) 2CytoGenomics Lab, Department of Genetics and Biotechnology, University of Trás-os-Montes e Alto Douro, 5000-801 Vila Real, Portugal; [email protected] 3BioISI-Biosystems and Integrative Sciences Institute, Faculty of Sciences, University of Lisbon, 1749-016 Lisbon, Portugal 4 FFP-I3ID—Instituto de Investigação, Inovação e Desenvolvimento, FP-BHS—Biomedical and Health Sciences Research Unit, Faculdade de Ciências da Saúde, Universidade Fernando Pessoa, Rua Carlos da Maia 296, 4200-150 Porto, Portugal 5Associate Laboratory i4HB—Institute for Health and Bioeconomy, Faculty of Pharmacy, University of Porto, 4050-313 Porto, Portugal 6 UCIBIO—Applied Molecular Biosciences Unit, MEDTECH—Medicines and Healthcare Products, Laboratory of Pharmaceutical Technology, Department of Drug Sciences, Faculty of Pharmacy, University of Porto, 4050-313 Porto, Portugal 7CBMA—Centro de Biologia Molecular e Ambiental, Departamento de Biologia, Universidade do Minho, 4710-057 Braga, Portugal *Correspondence: [email protected] (C.M.L.); [email protected] (M.L.) † These authors contributed equally to this work. Abstract: Cancer is one of the leading causes of death, and latest predictions indicate that cancerrelated deaths will increase over the next few decades. Despite significant advances in conventional therapies, treatments remain far from ideal due to limitations such as lack of selectivity, non-specific distribution, and multidrug resistance. Current research is focusing on the development of several strategies to improve the efficiency of chemotherapeutic agents and, as a result, overcome the challenges associated with conventional therapies. In this regard, combined therapy with natural compounds and other therapeutic agents, such as chemotherapeutics or nucleic acids, has recently emerged as a new strategy for tackling the drawbacks of conventional therapies. Taking this strategy into consideration, the co-delivery of the above-mentioned agents in lipid-based nanocarriers provides some advantages by improving the potential of the therapeutic agents carried. In this review, we present an analysis of the synergistic anticancer outcomes resulting from the combination of natural compounds and chemotherapeutics or nucleic acids. We also emphasize the importance of these co-delivery strategies when reducing multidrug resistance and adverse toxic effects. Furthermore, the review delves into the challenges and opportunities surrounding the application of these co-delivery strategies towards tangible clinical translation for cancer treatment. Keywords: cancer; conventional therapy; combinedtherapy; lipid-based nanocarriers; naturalcompounds 1. Introduction According to the World Health Organization (WHO), cancer is a serious public health problem around the world, being the leading cause of mortality and causing more than 6 million deaths yearly [ 1 , 2 ]. While the cancer mortality rate has declined in recent years, WHO estimates it will reach 13.1 million cancer-related deaths by 2030 [ 3 , 4 ]. Despite Pharmaceutics 2023,15, 1317. https://doi.org/10.3390/pharmaceutics15041317 https://www.mdpi.com/journal/pharmaceutics Pharmaceutics 2023,15, 1317 2 of 21 extensive development of cytotoxic agents, current therapy approaches for cancer are still ineffective [ 5 ]. There are two major treatment options available: surgical procedures or nonsurgical therapy regimens [ 5 ]. The surgical intervention is limited by the tumor’s size as well as the stage of metastasis in the tissues and organs from the site of origin. Non-surgical treatment options primarily include chemotherapy and radiotherapy, or a combination of these approaches [ 6 , 7 ]. Even though chemotherapeutic agents have evidenced efficacy in killing cancer cells by interfering with the process of cell division [ 5 ], they still face a number of challenges, including low bioavailability and lack of selectivity. Consequently, non-specific body distribution of chemotherapy is a key factor for cancer patient mortality, followed by chemo-resistance of cancer cells, which is another significant barrier that must be overcome in order to provide effective cancer treatment [2,3,7–9]. Several strategies have been employed to improve the performance of chemotherapeutic agents and, as a result, overcome the abovementioned challenges. Among these strategies are chemical modification, the development of new chemotherapeutic agents that are not detected by multidrug resistance (MDR) efflux pumps, and the combination of the cytotoxic agent with a chemosensitizer. Moreover, nanocarriers have been proposed to surpass some of the chemotherapy challenges. In this regard, nanocarriers for drug delivery are designed to reach specific organs and act selectively on the target site, providing advantages over conventional chemotherapeutics [ 1 , 7 , 10 ]. Some of the nanocarriers’ benefits include increased permeability through cell membranes and improved protection of the drugs against physical and chemical degradation. Furthermore, nanocarriers improve the therapeutic potential by optimizing drug properties such as stability, solubility, and bioavailability [1,11]. A common strategy for cancer therapy based on the association of multiple chemotherapeutic agents has been implemented as the standard first-line treatment of various malignancies to improve clinical outcome [ 2 ]. This approach has shown great potential, particularly to solve the issue of MDR in cancer cells [ 12 , 13 ] and improve anticancer efficacy [ 14 – 16 ]. Nonetheless, the administration of multiple drugs is frequently challenging, as different pharmacological agents have distinct pharmacokinetic profiles, resulting in an uncoordinated uptake by the tumor cell, affecting the expected synergistic effect [ 17 , 18 ]. Since nanocarriers can deliver multiple pharmacological agents to the same tumor cell in a single vehicle, the administration of combined drugs utilizing nanocarriers offers the most recent and most efficient therapy for several cancers. The “same time at same place” strategy is appealing since it may increase therapeutic efficacy while minimizing damage to healthy cells through pharmacological synergism, overcoming MDR, and reducing the effective doses [ 2 , 19 ]. Additionally, due to the importance of minimizing harmful side effects to healthy cells, the pharmaceutical market has been more receptive to lipid-based nanocarriers as they are classified by the FDA as generally recognized as safe (GRAS). Lipid-based nanocarriers are also regarded as safe because they are biodegradable and will not accumulate in the body [20]. There is currently a growing interest in the use of natural products in cancer prevention and therapy. Natural compounds and their derivatives have been clinically researched for their capacity to reverse, inhibit, and prevent cancer progression [ 21 ]. Due to their proven efficacy in a wide range of malignant tumors with minimal side effects and toxicity, some authors demonstrated that these agents may be a promising option for combination therapy [ 22 ]. For their prospective therapeutic applications, nucleic acids such as plasmid DNA (pDNA), small interfering RNA (siRNA), and micro-RNA (miRNA) have been developed into potent tools. Since nucleic acids are able, among other effects, to modulate the expression of genes responsible for MDR, associating chemotherapeutics with nucleic acids has been suggested as an appropriate strategy to increase the effect of cancer therapy [ 23 – 26 ]. The combination of natural compounds and nucleic acids is a less well-known strategy that has the potential to be very effective as a therapeutic modality that acts by different mechanisms. This combination can lead to a synergistic improvement of the therapeutic effect, a sensitization of the cancer cells to the anticancer activity of the natural compound, and a synergic effect against MDR that restores the anticancer effect. Pharmaceutics 2023,15, 1317 3 of 21 This review provides a comprehensive overview of lipid-based nanocarriers used for the co-delivery of natural compounds either with chemotherapeutic drugs or with nucleic acids. The utilization of such co-delivery systems offers several benefits, including synergistic/additive/potentiation effects, sensitization of cancer cells, overcoming of MDR, and reduction in adverse effects. Given their promising features, there is an increasing number of reviews exploring the use of natural compounds in cancer treatment (e.g., [ 27 – 33 ]). However, to date, there has been no comprehensive investigation into the use of lipid-based nanocarriers for the co-delivery of natural compounds and nucleic acids, nor have there been any examples provided of the use of lyotropic liquid crystalline nanoassemblies (LLCNs). Recently, advanced lipid mesophase delivery systems have emerged as a promising class of nanocarrier system. These systems have the potential to encapsulate various cargos with a wide range of lipophilicity properties, making them one of the most advantageous co-delivery systems for cancer [ 34 ]. For these reasons, a thorough and up-to-date overview of the studies currently available in the literature is still lacking. Lastly, the review examines the potential opportunities and challenges associated with the implementation of nanocarriers for co-delivery of natural compounds and/or chemotherapeutic drugs and nucleic acids in a clinical context. 2. Natural Compounds: Advantages of Combination Therapy in Cancer Conventional therapy has evident benefits in cancer treatment; however, despite the continuous emergence of new anticancer agents, the majority of chemotherapy-based treatment continues to remain ineffective due to an array of factors, which include chemotherapyinduced toxicity and adverse reactions, insufficient target specificity, and, most importantly, drug resistance during cancer progression (Figure 1) [9]. In this regard, combination therapy has recently become an emerging strategy for tackling the drawbacks of chemotherapy. Simultaneous delivery of two or more therapeutic agents (chemotherapeutic drugs/natural compounds/nucleic acids) can modify different signaling pathways in cancer cells, providing a synergistic response, improving targeting selectivity, optimizing therapeutic effect, and overcoming MDR (Figure 2) [ 2 , 17 , 35 ]. Thus, taking benefit of the minimal side effects promoted by natural compounds, there is a tendency to follow the potential strategy of combination therapy [9]. Pharmaceutics 2023,15, 1317 4 of 21 Pharmaceutics 2023, 15, x FOR PEER REVIEW 4 of 23 Figure 1. Problems associated with the classical single-delivery therapy (i.e., administration of each of the therapeutic agents in their free form). Nucleic acids, if delivered in the free form, would face different pharmacokinetic challenges, including inactivation by nucleases (A), lack of serum stability due to the immune system (B) and serum proteins (C), extravasation difficulties (D), non-specific distribution in target cells (E), difficulties entering the cell (F), and degradation if not able to escape endosomes (G). Chemotherapeutic drugs, when delivered in the free form, have a nonspecific distribution in cancer cells and healthy cells causing serious adverse side effects, commonly affecting hair follicles, the digestive tract, blood cells and nerves. Furthermore, several MDR mechanisms, such as drug efflux by multidrug resistance protein 1 (MRP1), P-glycoprotein (P-gp), and breast cancer resistance protein (BCRP), or inactivation of apoptotic pathways by B cell leukemia protein (Bcl2), can impair their efficiency. Natural compounds, when administered in their free form, exhibit a number of pharmacokinetic issues that affect their biodistribution and efficacy (1–6). In this regard, combination therapy has recently become an emerging strategy for tackling the drawbacks of chemotherapy. Simultaneous delivery of two or more therapeutic agents (chemotherapeutic drugs/natural compounds/nucleic acids) can modify different signaling pathways in cancer cells, providing a synergistic response, improving targeting selectivity, optimizing therapeutic effect, and overcoming MDR (Figure 2) [2,17,35]. Thus, taking benefit of the minimal side effects promoted by natural compounds, there is a tendency to follow the potential strategy of combination therapy [9]. Figure 1. Problems associated with the classical single-delivery therapy (i.e., administration of each of the therapeutic agents in their free form). Nucleic acids, if delivered in the free form, would face different pharmacokinetic challenges, including inactivation by nucleases (A), lack of serum stability due to the immune system (B) and serum proteins (C), extravasation difficulties (D), nonspecific distribution in target cells (E), difficulties entering the cell (F), and degradation if not able to escape endosomes (G). Chemotherapeutic drugs, when delivered in the free form, have a nonspecific distribution in cancer cells and healthy cells causing serious adverse side effects, commonly affecting hair follicles, the digestive tract, blood cells and nerves. Furthermore, several MDR mechanisms, such as drug efflux by multidrug resistance protein 1 (MRP1), P-glycoprotein (P-gp), and breast cancer resistance protein (BCRP), or inactivation of apoptotic pathways by B cell leukemia protein (Bcl2), can impair their efficiency. Natural compounds, when administered in their free form, exhibit a number of pharmacokinetic issues that affect their biodistribution and efficacy (1–6). Pharmaceutics 2023,15, 1317 5 of 21 Pharmaceutics 2023, 15, x FOR PEER REVIEW 5 of 23 Figure 2. Schematic illustration of lipid-based nanocarriers and advantages of their use for the codelivery of natural compounds and chemotherapeutic drugs or nucleic acids. Adapted from [36,37], and from [38,39] with permission from Elsevier. 2.1. Overcoming Multidrug Resistance MDR is a mechanism that emerges after cells’ exposure to chemotherapeutic agents and refers to the capacity of cancer cells to become resistant to the agents’ effect and can result in the development of malignant cell metastases [40,41]. The cellular mechanisms of MDR can be divided into two general classes: (i) those that block the delivery of chemotherapeutic agents to their target sites, and include the abnormal vasculature which results in low oral chemotherapeutic absorption, early renal clearance, poor bioavailability, and lower tumor site accumulation; or (ii) those that emerge in cancer cells primarily as a result of genetic and epigenetic alterations and directly affect the efficacy of chemotherapeutic agents, and include apoptosis deregulation, increased repair of drug-induced DNA damage, and, enhanced efflux of chemotherapeutic agents [40,41]. Although a wide range of different factors can contribute to MDR, drug efflux changes are considered the major cause of classical MDR [42]. Drug efflux is enhanced by the overexpression of human ATP-binding cassette (ABC) membrane transporters. These transporters are accountable for removing chemotherapeutic agents from cancer cells. Figure 2. Schematic illustration of lipid-based nanocarriers and advantages of their use for the codelivery of natural compounds and chemotherapeutic drugs or nucleic acids. Adapted from [ 36 , 37 ], and from [38,39] with permission from Elsevier. 2.1. Overcoming Multidrug Resistance MDR is a mechanism that emerges after cells’ exposure to chemotherapeutic agents and refers to the capacity of cancer cells to become resistant to the agents’ effect and can result in the development of malignant cell metastases [ 40 , 41 ]. The cellular mechanisms of MDR can be divided into two general classes: (i) those that block the delivery of chemotherapeutic agents to their target sites, and include the abnormal vasculature which results in low oral chemotherapeutic absorption, early renal clearance, poor bioavailability, and lower tumor site accumulation; or (ii) those that emerge in cancer cells primarily as a result of genetic and epigenetic alterations and directly affect the efficacy of chemotherapeutic agents, and include apoptosis deregulation, increased repair of drug-induced DNA damage, and, enhanced efflux of chemotherapeutic agents [40,41]. Although a wide range of different factors can contribute to MDR, drug efflux changes are considered the major cause of classical MDR [ 42 ]. Drug efflux is enhanced by the Pharmaceutics 2023,15, 1317 6 of 21 overexpression of human ATP-binding cassette (ABC) membrane transporters. These transporters are accountable for removing chemotherapeutic agents from cancer cells. Among the ABC transporters, the multidrug resistance protein (MRP) P-glycoprotein (P-gp) is an ATP-dependent drug efflux pump also referred to as multidrug resistance protein 1 (MRP1) (Figure 1). P-gp, the best-studied drug efflux pump, is a significant contributor to chemotherapy failure [ 42 , 43 ]. Furthermore, it has been reported that resistant cells have significantly greater levels of P-gp, and their overexpression is linked to a poor prognosis in a variety of cancers [44]. P-gp-mediated MDR affects several classes of chemotherapeutic agents, such as anthracyclines (e.g., daunorubicin and doxorubicin (DOX)), taxanes (e.g., paclitaxel (PTX) and docetaxel (DTX)), epipodophyllotoxins (e.g., etoposide), and camptothecins (e.g., topotecan and methotrexate (MTX)). As a result, strategies to reverse P-gp-mediated MDR have been extensively researched since the early 1980s, and three generations of P-gp inhibitors are currently classified [ 40 , 41 , 45 ]. Despite promising in vitro results, there is not, unfortunately, an irrefutable proof of efficacy for the currently available inhibitors, since various clinical trials have been performed to evaluate their anticancer effect, but no significant improvements have been found [ 21 , 40 ]. The development of an ideal inhibitor is commonly associated with the difficulty of finding compounds with high potency and specificity, and with low intrinsic toxicity. Furthermore, it is difficult to achieve specificity of the inhibitors to the ABC transporters, as well as interactions between chemotherapeutic agents and inhibitors [21]. Consequently, in order to overcome such limitations, researchers have shifted their attention to novel approaches for MDR prevention in cancer. In this regard, natural compounds have emerged as an appealing solution, primarily due to their chemosensitizing capacity [ 46 ]. Chemosensitizers are small molecules that can increase the sensitivity of cancer cells to chemotherapeutic agents, and those that act as ABC membrane transporter inhibitors are particularly effective. The main example is inhibitors obtained from natural sources, also known as fourth-generation inhibitors, which can interact with ATP binding sites or act directly at MRP binding sites. Natural inhibitors have the potential to be considerably more successful since they offer the most diverse and innovative chemical scaffolds [ 21 ]. Moreover, natural compounds with anticancer properties are widely available, as evidenced by the Naturally Occurring Plant-based Anti-Cancer Compound-Activity-Target Database (NPACT) [ 47 ]. The main natural compounds evaluated as chemosensitizing agents are highlighted in Figure 3. Pharmaceutics 2023, 15, x FOR PEER REVIEW 6 of 23 Among the ABC transporters, the multidrug resistance protein (MRP) P-glycoprotein (Pgp) is an ATP-dependent drug efflux pump also referred to as multidrug resistance protein 1 (MRP1) (Figure 1). P-gp, the best-studied drug efflux pump, is a significant contributor to chemotherapy failure [42,43]. Furthermore, it has been reported that resistant cells have significantly greater levels of P-gp, and their overexpression is linked to a poor prognosis in a variety of cancers [44]. P-gp-mediated MDR affects several classes of chemotherapeutic agents, such as anthracyclines (e.g., daunorubicin and doxorubicin (DOX)), taxanes (e.g., paclitaxel (PTX) and docetaxel (DTX)), epipodophyllotoxins (e.g., etoposide), and camptothecins (e.g., topotecan and methotrexate (MTX)). As a result, strategies to reverse P-gp-mediated MDR have been extensively researched since the early 1980s, and three generations of P-gp inhibitors are currently classified [40,41,45]. Despite promising in vitro results, there is not, unfortunately, an irrefutable proof of efficacy for the currently available inhibitors, since various clinical trials have been performed to evaluate their anticancer effect, but no significant improvements have been found [21,40]. The development of an ideal inhibitor is commonly associated with the difficulty of finding compounds with high potency and specificity, and with low intrinsic toxicity. Furthermore, it is difficult to achieve specificity of the inhibitors to the ABC transporters, as well as interactions between chemotherapeutic agents and inhibitors [21]. Consequently, in order to overcome such limitations, researchers have shifted their attention to novel approaches for MDR prevention in cancer. In this regard, natural compounds have emerged as an appealing solution, primarily due to their chemosensitizing capacity [46]. Chemosensitizers are small molecules that can increase the sensitivity of cancer cells to chemotherapeutic agents, and those that act as ABC membrane transporter inhibitors are particularly effective. The main example is inhibitors obtained from natural sources, also known as fourth-generation inhibitors, which can interact with ATP binding sites or act directly at MRP binding sites. Natural inhibitors have the potential to be considerably more successful since they offer the most diverse and innovative chemical scaffolds [21]. Moreover, natural compounds with anticancer properties are widely available, as evidenced by the Naturally Occurring Plant-based Anti-Cancer Compound-ActivityTarget Database (NPACT) [47]. The main natural compounds evaluated as chemosensitizing agents are highlighted in Figure 3. Figure 3. Main natural compounds considered chemosensitizing agents, according to their chemical family [47] . Natural Compounds Flavonoids and Phenolic derivatives Epigallocatechin-3 gallate Genistein Naringenin Myricetin Resveratrol Curcumin Isoxanthohumol Steroids and Terpenoids Cucurbitacin B Withaferin A Ursolic Acid Lupeol ∆9-Tetrahydrocannabinol Alkaloids 3,3’diindolylmethane Noscapine Sinomenine Oxymatrine Saponins Escin Ginsenoside Rg3 Others Thymoquinone Shikonin β-Carotene α-Carotene Figure 3. Main natural compounds considered chemosensitizing agents, according to their chemical family [47]. Pharmaceutics 2023,15, 1317 7 of 21 Although a wide range of natural compounds, such as terpenoids, alkaloids, steroids, and saponins (Figure 3), have recently been employed to overcome MDR [ 46 , 47 ], phenolic derivatives and flavonoids have been the most cited and studied. According to in vitro biochemical and pharmacological studies, the majority of flavonoids could modulate ABC transporters by competitively binding to the substrate-binding sites and, as a result, delaying cellular efflux [ 21 ]. From these chemical families of natural compounds, resveratrol (RSV), curcumin (CUR), and epigallocatechin-3-gallate (EGCG) are the most promising as they can also directly interact with MDR genes [ 47 ]. For example, CUR, a polyphenol found in plants of the genus Curcuma, modulates cancer signaling pathways, primarily by inhibiting the nuclear factor kappa B (NF-kB) pathway, as shown in Figure 4. In more detail, CUR modifies signaling pathways of the apoptosis process, by interfering with Xlinked inhibitor of apoptosis protein (XIAP), cell proliferation (cyclin D1, ciclo-oxigenase-2 (COX-2), C-myc), cellular inhibitor of apoptosis protein-1 (CIAP-1), cell metastasis (C-X-C chemokine receptor type 4 (CXCR4), ICAM-I), cell invasion (matrix metallopeptidase 9 (MMP-9)), and angiogenesis (vascular endothelial growth factor (VEGF)) [ 47 ]. This natural compound also displays P-gp inhibitory activity by downregulating the phosphoinositide 3-kinases (PI3K)/protein kinase B (Akt) [36]. Pharmaceutics 2023, 15, x FOR PEER REVIEW 7 of 23 Although a wide range of natural compounds, such as terpenoids, alkaloids, steroids, and saponins (Figure 3), have recently been employed to overcome MDR [46,47], phenolic derivatives and flavonoids have been the most cited and studied. According to in vitro biochemical and pharmacological studies, the majority of flavonoids could modulate ABC transporters by competitively binding to the substrate-binding sites and, as a result, delaying cellular efflux [21]. From these chemical families of natural compounds, resveratrol (RSV), curcumin (CUR), and epigallocatechin-3-gallate (EGCG) are the most promising as they can also directly interact with MDR genes [47]. For example, CUR, a polyphenol found in plants of the genus Curcuma, modulates cancer signaling pathways, primarily by inhibiting the nuclear factor kappa B (NF-kB) pathway, as shown in Figure 4. In more detail, CUR modifies signaling pathways of the apoptosis process, by interfering with Xlinked inhibitor of apoptosis protein (XIAP), cell proliferation (cyclin D1, ciclo-oxigenase2 (COX-2), C-myc), cellular inhibitor of apoptosis protein-1 (CIAP-1), cell metastasis (CX-C chemokine receptor type 4 (CXCR4), ICAM-I), cell invasion (matrix metallopeptidase 9 (MMP-9)), and angiogenesis (vascular endothelial growth factor (VEGF)) [47]. This natural compound also displays P-gp inhibitory activity by downregulating the phosphoinositide 3-kinases (PI3K)/protein kinase B (Akt) [36]. Figure 4. Potential targets associated with Curcumin anticancer activity. This natural compound induces a reduction in its target genes by inhibiting NF-kβ signaling. Bcl-2-B-cell limphoma-2; COX2-ciclo-oxigenase-2; IL-6-interleukin 6; IL-10-interleukin 10; IL-18-interleukin 18; MMP9-matrix metallopeptidase 9; NF-kβ-nuclear factor kappa B; VEGF-vascular endothelial growth factor; XIAP-Xlinked inhibitor of apoptosis protein. 2.2. Synergistic, Additive, and Potentiation Effects The combination of therapeutic agents can result in the following complementary effects [35,48]: (i) synergistic, when the final effect is greater than the sum of individual agents’ effects, resulting in cooperative targeting of activity regulation but with each agent targeting different sites; (ii) additive, that promotes greater or equal effect to the sum of individual agents’ effect; however, both agents act on the same target or pathway; and, (iii) potentiation, in which one agent can enhance the effect of the other or minimize its side effects by regulating pharmacokinetics and/or pharmacodynamics. Furthermore, when both agents in a combination therapy act on the same pathway or target, an undesirable antagonist effect may occur (i.e., when the resultant therapeutic effect is less than the sum of effects of each agent delivered). 2.3. Reducing the Side Effects Figure 4. Potential targets associated with Curcumin anticancer activity. This natural compound induces a reduction in its target genes by inhibiting NF-k β signaling. Bcl-2-B-cell limphoma-2; COX-2-ciclo-oxigenase-2; IL-6-interleukin 6; IL-10-interleukin 10; IL-18-interleukin 18; MMP9-matrix metallopeptidase 9; NF-k β -nuclear factor kappa B; VEGF-vascular endothelial growth factor; XIAPX-linked inhibitor of apoptosis protein. 2.2. Synergistic, Additive, and Potentiation Effects The combination of therapeutic agents can result in the following complementary effects [ 35 , 48 ]: (i) synergistic, when the final effect is greater than the sum of individual agents’ effects, resulting in cooperative targeting of activity regulation but with each agent targeting different sites; (ii) additive, that promotes greater or equal effect to the sum of individual agents’ effect; however, both agents act on the same target or pathway; and, (iii) potentiation, in which one agent can enhance the effect of the other or minimize its side effects by regulating pharmacokinetics and/or pharmacodynamics. Furthermore, when both agents in a combination therapy act on the same pathway or target, an undesirable antagonist effect may occur (i.e., when the resultant therapeutic effect is less than the sum of effects of each agent delivered). Pharmaceutics 2023,15, 1317 8 of 21 2.3. Reducing the Side Effects Combination therapy may also avoid the toxic side effects that normally affect healthy cells. This could happen if one of the co-delivered agents is antagonistic to the other in terms of cytotoxicity. For example, antioxidant supplementation during anticancer treatment may decrease adverse reactions, primarily due to the prevention of reactive oxygen species (ROS)-mediated injury, without compromising anticancer activity [47]. 2.4. Decreasing the Effective Chemotherapy Dose One significant drawback of chemotherapy is the high dose of cytotoxic drugs required to achieve a therapeutic effect, which causes serious side effects. In this context, combination therapy appears to be a promising alternative, since the combination of a natural compound and a chemotherapeutic drug may promote an increase in the cytotoxic effect (due to previously described synergistic, additive, or potentiation effects), improve chemotherapeutic performance, and reduce the effective dose required to achieve the necessary therapeutic outcomes [47]. 3. Lipid-Based Nanocarriers for the Co-Delivery of Natural Compounds and Other Therapeutic Agents Classic single-delivery therapy (i.e., single administration of the therapeutic agents in their free form) can be challenging due to several drawbacks, including the presence of highly organized physical, physiological, and enzymatic barriers, which make targeting cancer cells with minimal side effects particularly difficult (Figure 1). Furthermore, the varying physiochemical and pharmacodynamic properties of different agents can limit their successful co-delivery [ 49 ]. Thus, as previously stated, nanocarriers are an advantageous option for overcoming these challenges, since they are designed to reach specific organs and act selectively on the target site [ 1 , 7 , 10 ]. In this regard, several nanocarriers have been widely explored for the delivery of anticancer drugs [ 5 ]. Lipid-based nanocarriers present some attractive features such as: non-toxic degradation products, biodegradable matrix, low toxicity, high capacity to incorporate lipophilic and/or hydrophilic compounds, and ability to achieve controlled release of encapsulated therapeutic agent [50,51]. 3.1. Co-Delivery of Natural Compounds and Chemotherapeutics Table 1provides several examples of lipid-based nanocarriers co-encapsulating a chemotherapeutic agent and a natural compound for cancer treatment. Pharmaceutics 2023,15, 1317 9 of 21 Table 1. Examples of lipid-based nanocarriers co-encapsulating a chemotherapeutic agent and a natural compound for cancer treatment. Chemotherapeutic Agent Natural Compound Lipid-Based Nanocarrier Composition Strategy Ref. 5-FU RSV Ultradeformable liposomes PL90G:SC Synergistic effect [52] PEGylated liposomes EPC:DSPE-PEG2000 Synergistic effect [53] DTX CUR SLNs Compritol ® 888 ATO, GMS, Poloxamer 188Functionalization: Folic acid Synergistic effect [54] DOX BCL NLCs SA, SPC, Precirol®ATO5, Cremophor®ELP, DDAB Synergistic effect [55] CUR Liposomes PEG-RGDK-lipopeptide Synergistic effect [56] NLCs Precirol®ATO 5, LabrafacTM lipophile WL 1349, Lipoid S75, Cremophor®RH 40, Glycerin Synergistic effect [39] Liposomes DPPC:DSPE:CHOL:PEG2000 Synergistic effect [9] DHA NLCs Tween®80, Oleic acid, Triethanolamine, Compritol®888 ATO, EDTA Overcome MDR [57] OA Liposomes HSPC:CHOL:DSPE:PEG2000 Synergistic effect [58] PA Liposomes PC:CHOL Synergistic effect [59] QUER Liposomes BIO:DSPE:PEG2000 Overcome MDR [43] Phytosomes Lecithin Synergistic effect [60] TS SLNs Compritol®888 ATO, TPGS, Triethanolamine Synergistic effect [61] BJO LLCNs GMO:P407 Hexagonal phase inducer: Oleic acid Overcome MDR [62] ETP CUR NLCs GMS, SPC, Oleic acid, DDAB Decreasing the effective chemotherapy dose [63] Nanoemulsion SPC, Tween®80 Additive effect [64] GEM BCL NLCs SPC, Precirol®ATO-5, Olive oil, Tween®80, DDAB Synergistic effect [65] ITC CTL Liposomes DPPC:CHOL:DSPE-PEG2000-FA Synergistic effect [66] MTX BCN Lipid–polymer hybrid nanoparticle DSPE-PEG2000:SA:Gelucire®50/13:PLA Synergistic effect [67] Pharmaceutics 2023,15, 1317 16 of 21 vaccines [ 124 ]. However, the clinical applications of gene therapy for cancer treatment are currently limited due to the growing stage of the technology, potential unknown risks, higher costs, and selectivity in treating certain types of cancer [ 97 ]. Therefore, if this technology is not mature enough in a single delivery context, it is even further away from clinical translation when nucleic acid and natural compound co-delivery is considered. Moreover, based on current understanding, there is an academic interest in co-delivery of natural compounds with chemotherapeutics and/or nucleic acids for cancer treatment that does not mirror the lack of ongoing clinical trials pertaining to the subject matter. This may be attributed to the emergence of new challenges as well as the expenses involved in the design and development of such intricate formulations. The bench-tomarket translation of co-delivery-based nanotherapeutics is also severely constrained by the regulatory framework surrounding clinical application. Therefore, it is imperative to address the regulatory and scientific gaps to facilitate the advancement of nanomedicine as a driving force for future biomedical innovation. 4. Conclusions Conventional cancer therapies are still unable to achieve the desired outcomes due to current limitations related with inefficiency and selectivity. As a result, the development of novel therapeutic strategies to overcome these limitations has become critical. Combination therapy has been extensively explored in this context, since co-delivery of natural compounds and chemotherapeutic agents or nucleic acids can achieve stronger anticancer effects through synergistic/additive/potentiation mechanisms, or by improving selectivity, and overcoming MDR either by inhibition of ABC membrane transporters or interaction with MDR genes. However, while this strategy provides new therapeutic results, it also introduces several new challenges, such as the need to clearly identify the mechanism behind the enhanced anticancer activity by comparing the co-delivery effect with co-administration effect. It is also required to better define the concentration-dependent effect of natural compounds, as well as to evaluate the improvement of their pharmacokinetic parameters when delivered by lipid-based nanocarriers. Moreover, despite lipid-based nanocarriers being considered biocompatible, the safety of the loaded cargo has also to be addressed, namely by long-term toxicity assessment and by studying the immunogenicity issues that may arise from the nucleic acid conjugation. Furthermore, as far as we know, no clinical trials with nanocarriers co-delivering natural compounds or other therapeutic agents have been conducted, which may be due to these challenges as well as the costs of designing and developing such complex formulations. Despite the critical points that remain unresolved, the co-delivery strategy of natural compounds and chemotherapeutic agents/nucleic acids is undeniably very promising, especially by further exploring versatile nanocarriers such as LLCNs. We strongly believe that this approach, allied with thorough characterization, rational development, and pre-clinical studies, will fulfill the translation of lipid-based nanocarriers into clinical applications. Author Contributions: Conceptualization C.M.L., M.L. and F.A.; writing—original draft preparation, P.V.T., E.F. and T.B.S.; writing—review and editing, P.V.T., C.M.L., M.L. and F.A.; visualization, M.L. and P.V.T.; supervision, C.M.L., M.L. and F.A.; funding acquisition, M.L. and F.A. All authors have read and agreed to the published version of the manuscript. Funding: This work was supported by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UIDB/04650/2020 and UIDB/04050/2020 (CFUM-UP and CBMA), UIDB/04046/2020 and UIDP/04046/2020 (BioISI), UIDP/04378/2020 and UIDB/04378/2020 (UCIBIO), and LA/P/0140/2020 (i4HB). E.F. thanks FCT for the PhD grant (SFRH/BD/147938/2019). Institutional Review Board Statement: Not applicable. Informed Consent Statement: Not applicable. Pharmaceutics 2023,15, 1317 17 of 21 Data Availability Statement: Data sharing is not applicable to this article as no new data were created or analyzed in this study. Conflicts of Interest: The authors declare no conflict of interest. References 1. Sanchez-Moreno, P.; Ortega-Vinuesa, J.L.; Peula-Garcia, J.M.; Marchal, J.A.; Boulaiz, H. Smart Drug-Delivery Systems for Cancer Nanotherapy. Curr. Drug Targets 2018,19, 339–359. [CrossRef] [PubMed] 2. Meng, J.; Guo, F.; Xu, H.; Liang, W.; Wang, C.; Yang, X.D. Combination Therapy using Co-encapsulated Resveratrol and Paclitaxel in Liposomes for Drug Resistance Reversal in Breast Cancer Cells in vivo. Sci. Rep. 2016,6, 22390. [CrossRef] 3. Mozafari, M.R.; Pardakhty, A.; Azarmi, S.; Jazayeri, J.A.; Nokhodchi, A.; Omri, A. Role of nanocarrier systems in cancer nanotherapy. J. Liposome Res. 2009,19, 310–321. [CrossRef] [PubMed] 4. Boyle, P.; Levin, B. World Cancer Report 2008; IARC Press, International Agency for Research on Cancer: Lyon, France, 2008. 5. Qi, S.S.; Sun, J.H.; Yu, H.H.; Yu, S.Q. Co-delivery nanoparticles of anti-cancer drugs for improving chemotherapy efficacy. Drug Deliv. 2017,24, 1909–1926. [CrossRef] 6. Leng, F.; Liu, F.; Yang, Y.; Wu, Y.; Tian, W. Strategies on Nanodiagnostics and Nanotherapies of the Three Common Cancers. Nanomaterials 2018,8, 202. [CrossRef] [PubMed] 7. Senapati, S.; Mahanta, A.K.; Kumar, S.; Maiti, P. Controlled drug delivery vehicles for cancer treatment and their performance. Signal. Transduct. Target. Ther. 2018,3, 7. [CrossRef] 8. Hofmann, M.; Guschel, M.; Bernd, A.; Bereiter-Hahn, J.; Kaufmann, R.; Tandi, C.; Wiig, H.; Kippenberger, S. Lowering of tumor interstitial fluid pressure reduces tumor cell proliferation in a xenograft tumor model. Neoplasia 2006,8, 89–95. [CrossRef] 9. Tefas, L.R.; Sylvester, B.; Tomuta, I.; Sesarman, A.; Licarete, E.; Banciu, M.; Porfire, A. Development of antiproliferative longcirculating liposomes co-encapsulating doxorubicin and curcumin, through the use of a quality-by-design approach. Drug Des. Devel. Ther. 2017,11, 1605–1621. [CrossRef] 10. Cho, K.; Wang, X.; Nie, S.; Chen, Z.G.; Shin, D.M. Therapeutic nanoparticles for drug delivery in cancer. Clin. Cancer Res. 2008 ,14, 1310–1316. [CrossRef] 11. Jain, T.K.; Morales, M.A.; Sahoo, S.K.; Leslie-Pelecky, D.L.; Labhasetwar, V. Iron oxide nanoparticles for sustained delivery of anticancer agents. Mol. Pharm. 2005,2, 194–205. [CrossRef] 12. Gottesman, M.M. Mechanisms of Cancer Drug Resistance. Annu. Rev. Med. 2002,53, 615–627. [CrossRef] 13. Noguchi, K.; Katayama, K.; Mitsuhashi, J.; Sugimoto, Y. Functions of the breast cancer resistance protein (BCRP/ABCG2) in chemotherapy. Adv. Drug Deliv. Rev. 2009,61, 26–33. [CrossRef] [PubMed] 14. Al-Lazikani, B.; Banerji, U.; Workman, P. Combinatorial drug therapy for cancer in the post-genomic era. Nat. Biotechnol. 2012 ,30, 679–692. [CrossRef] [PubMed] 15. Bahadur, K.C.R.; Xu, P. Multicompartment intracellular self-expanding nanogel for targeted delivery of drug cocktail. Adv. Mater. 2012,24, 6479–6483. [CrossRef] [PubMed] 16. DeVita, V.T., Jr.; Young, R.C.; Canellos, G.P. Combination versus single agent chemotherapy: A review of the basis for selection of drug treatment of cancer. Cancer 1975,35, 98–110. [CrossRef] [PubMed] 17. Hu, C.M.; Zhang, L. Nanoparticle-based combination therapy toward overcoming drug resistance in cancer. Biochem. Pharm. Pharmacol. 2012,83, 1104–1111. [CrossRef] [PubMed] 18. Ma, J.; Waxman, D.J. Combination of antiangiogenesis with chemotherapy for more effective cancer treatment. Mol. Cancer Ther. 2008,7, 3670–3684. [CrossRef] 19. Li, H.; Li, M.; Chen, C.; Fan, A.; Kong, D.; Wang, Z.; Zhao, Y. On-demand combinational delivery of curcumin and doxorubicin via a pH-labile micellar nanocarrier. Int. J. Pharm. 2015,495, 572–578. [CrossRef] 20. Qi, J.; Zhuang, J.; Lu, Y.; Dong, X.; Zhao, W.; Wu, W. In vivo fate of lipid-based nanoparticles. Drug Discov. Today 2017 ,22, 166–172. [CrossRef] 21. Wu, C.-P.; Ohnuma, S.; Ambudkar, S.V. Discovering natural product modulators to overcome multidrug resistance in cancer chemotherapy. Curr. Pharm. Biotechnol. 2011,12, 609–620. [CrossRef] 22. Kallifatidis, G.; Hoy, J.J.; Lokeshwar, B.L. Bioactive natural products for chemoprevention and treatment of castration-resistant prostate cancer. Semin. Cancer Biol. 2016,40–41, 160–169. [CrossRef] [PubMed] 23. Kapse-Mistry, S.; Govender, T.; Srivastava, R.; Yergeri, M. Nanodrug delivery in reversing multidrug resistance in cancer cells. Front. Pharm. Pharmacol. 2014,5, 159. [CrossRef] 24. Creixell, M.; Peppas, N.A. Co-delivery of siRNA and therapeutic agents using nanocarriers to overcome cancer resistance. Nano Today 2012,7, 367–379. [CrossRef] [PubMed] 25. Meng, H.; Mai, W.X.; Zhang, H.; Xue, M.; Xia, T.; Lin, S.; Wang, X.; Zhao, Y.; Ji, Z.; Zink, J.I.; et al. Codelivery of an optimal drug/siRNA combination using mesoporous silica nanoparticles to overcome drug resistance in breast cancer in vitro and in vivo . ACS Nano 2013,7, 994–1005. [CrossRef] 26. Amani, A.; Alizadeh, M.R.; Yaghoubi, H.; Nohtani, M. Novel multi-targeted nanoparticles for targeted co-delivery of nucleic acid and chemotherapeutic agents to breast cancer tissues. Mater. Sci. Eng. C 2021,118, 111494. [CrossRef] Pharmaceutics 2023,15, 1317 18 of 21 27. Ali Abdalla, Y.O.; Subramaniam, B.; Nyamathulla, S.; Shamsuddin, N.; Arshad, N.M.; Mun, K.S.; Awang, K.; Nagoor, N.H. Natural Products for Cancer Therapy: A Review of Their Mechanism of Actions and Toxicity in the Past Decade. J. Trop. Med. 2022,2022, 5794350. [CrossRef] 28. Lin, S.-R.; Chang, C.-H.; Hsu, C.-F.; Tsai, M.-J.; Cheng, H.; Leong, M.K.; Sung, P.-J.; Chen, J.-C.; Weng, C.-F. Natural compounds as potential adjuvants to cancer therapy: Preclinical evidence. Br. J. Pharmacol. 2020,177, 1409–1423. [CrossRef] 29. Hashem, S.; Ali, T.A.; Akhtar, S.; Nisar, S.; Sageena, G.; Ali, S.; Al-Mannai, S.; Therachiyil, L.; Mir, R.; Elfaki, I.; et al. Targeting cancer signaling pathways by natural products: Exploring promising anti-cancer agents. Biomed. Pharmacother. 2022 ,150, 113054. [CrossRef] 30. Cho, Y.; Park, M.N.; Noh, S.; Kang, S.Y.; Kim, B. Review of Natural Compounds for the Management and Prevention of Lymphoma. Processes 2020,8, 1164. [CrossRef] 31. Sauter, E.R. Cancer prevention and treatment using combination therapy with natural compounds. Expert. Rev. Clin. Pharmacol. 2020,13, 265–285. [CrossRef] 32. Gao, Q.; Feng, J.; Liu, W.; Wen, C.; Wu, Y.; Liao, Q.; Zou, L.; Sui, X.; Xie, T.; Zhang, J.; et al. Opportunities and challenges for co-delivery nanomedicines based on combination of phytochemicals with chemotherapeutic drugs in cancer treatment. Adv. Drug Deliv. Rev. 2022,188, 114445. [CrossRef] [PubMed] 33. Ashrafizadeh, M.; Zarrabi, A.; Hushmandi, K.; Hashemi, F.; Rahmani Moghadam, E.; Raei, M.; Kalantari, M.; Tavakol, S.; Mohammadinejad, R.; Najafi, M.; et al. Progress in Natural Compounds/siRNA Co-delivery Employing Nanovehicles for Cancer Therapy. ACS Comb. Sci. 2020,22, 669–700. [CrossRef] [PubMed] 34. Teixeira, P.V.; Adega, F.; Martins-Lopes, P.; Machado, R.; Lopes, C.M.; Lúcio, M. pH-Responsive Hybrid Nanoassemblies for Cancer Treatment: Formulation Development, Optimization, and In Vitro Therapeutic Performance. Pharmaceutics 2023 ,15, 326. [CrossRef] 35. Hu, Q.; Sun, W.; Wang, C.; Gu, Z. Recent advances of cocktail chemotherapy by combination drug delivery systems. Adv. Drug Deliv. Rev. 2016,98, 19–34. [CrossRef] 36. Baek, J.S.; Cho, C.W. A multifunctional lipid nanoparticle for co-delivery of paclitaxel and curcumin for targeted delivery and enhanced cytotoxicity in multidrug resistant breast cancer cells. Oncotarget 2017,8, 30369–30382. [CrossRef] 37. Abdelaziz, H.M.; Elzoghby, A.O.; Helmy, M.W.; Samaha, M.W.; Fang, J.Y.; Freag, M.S. Liquid crystalline assembly for potential combinatorial chemo-herbal drug delivery to lung cancer cells. Int. J. Nanomed. 2019,14, 499–517. [CrossRef] 38. Abtahi, N.A.; Naghib, S.M.; Ghalekohneh, S.J.; Mohammadpour, Z.; Nazari, H.; Mosavi, S.M.; Gheibihayat, S.M.; Haghiralsadat, F.; Reza, J.Z.; Doulabi, B.Z. Multifunctional stimuli-responsive niosomal nanoparticles for co-delivery and co-administration of gene and bioactive compound: In vitro and in vivo studies. Chem. Eng. J. 2022,429, 132090. [CrossRef] 39. Zhao, X.; Chen, Q.; Li, Y.; Tang, H.; Liu, W.; Yang, X. Doxorubicin and curcumin co-delivery by lipid nanoparticles for enhanced treatment of diethylnitrosamine-induced hepatocellular carcinoma in mice. Eur. J. Pharm. Biopharm. 2015,93, 27–36. [CrossRef] 40. Wang, J.; Seebacher, N.; Shi, H.; Kan, Q.; Duan, Z. Novel strategies to prevent the development of multidrug resistance (MDR) in cancer. Oncotarget 2017,8, 84559–84571. [CrossRef] [PubMed] 41. Gottesman, M.M.; Fojo, T.; Bates, S.E. Multidrug resistance in cancer: Role of ATP-dependent transporters. Nat. Rev. Cancer 2002 , 2, 48–58. [CrossRef] 42. Liu, K.; Chen, W.; Yang, T.; Wen, B.; Ding, D.; Keidar, M.; Tang, J.; Zhang, W. Paclitaxel and quercetin nanoparticles co-loaded in microspheres to prolong retention time for pulmonary drug delivery. Int. J. Nanomed. 2017 ,12, 8239–8255. [CrossRef] [PubMed] 43. Zhang, J.; Luo, Y.; Zhao, X.; Li, X.; Li, K.; Chen, D.; Qiao, M.; Hu, H.; Zhao, X. Co-delivery of doxorubicin and the traditional Chinese medicine quercetin using biotin–PEG2000–DSPE modified liposomes for the treatment of multidrug resistant breast cancer. RSC Adv. 2016,6, 113173–113184. [CrossRef] 44. Israel, B.B.; Tilghman, S.L.; Parker-Lemieux, K.; Payton-Stewart, F. Phytochemicals: Current strategies for treating breast cancer. Oncol. Lett. 2018,15, 7471–7478. [CrossRef] [PubMed] 45. Gameiro, M.; Silva, R.; Rocha-Pereira, C.; Carmo, H.; Carvalho, F.; Bastos, M.L.; Remião, F. Cellular Models and In Vitro Assays for the Screening of modulators of P-gp, MRP1 and BCRP. Molecules 2017,22, 600. [CrossRef] 46. Aung, T.N.; Qu, Z.; Kortschak, R.D.; Adelson, D.L. Understanding the Effectiveness of Natural Compound Mixtures in Cancer through Their Molecular Mode of Action. Int. J. Mol. Sci. 2017,18, 656. [CrossRef] 47. de Oliveira Júnior, R.G.; Christiane Adrielly, A.F.; da Silva Almeida, J.R.G.; Grougnet, R.; Thiéry, V.; Picot, L. Sensitization of tumor cells to chemotherapy by natural products: A systematic review of preclinical data and molecular mechanisms. Fitoterapia 2018,129, 383–400. [CrossRef] 48. Jia, J.; Zhu, F.; Ma, X.; Cao, Z.; Cao, Z.W.; Li, Y.; Li, Y.X.; Chen, Y.Z. Mechanisms of drug combinations: Interaction and network perspectives. Nat. Rev. Drug Discov. 2009,8, 111–128. [CrossRef] 49. Xu, M.; Li, G.; Zhang, H.; Chen, X.; Li, Y.; Yao, Q.; Xie, M. Sequential delivery of dual drugs with nanostructured lipid carriers for improving synergistic tumor treatment effect. Drug Deliv. 2020,27, 983–995. [CrossRef] 50. Pardeike, J.; Hommoss, A.; Müller, R.H. Lipid nanoparticles (SLN, NLC) in cosmetic and pharmaceutical dermal products. Int. J. Pharm. 2009,366, 170–184. [CrossRef] 51. Rahman, H.S.; Rasedee, A.; How, C.W.; Abdul, A.B.; Zeenathul, N.A.; Othman, H.H.; Saeed, M.I.; Yeap, S.K. Zerumboneloaded nanostructured lipid carriers: Preparation, characterization, and antileukemic effect. Int. J. Nanomed. 2013 ,8, 2769–2781. [CrossRef] 52. Cosco, D.; Paolino, D.; Maiuolo, J.; Marzio, L.D.; Carafa, M.; Ventura, C.A.; Fresta, M. Ultradeformable liposomes as multidrug carrier of resveratrol and 5-fluorouracil for their topical delivery. Int. J. Pharm. 2015,489, 1–10. [CrossRef] [PubMed] Pharmaceutics 2023,15, 1317 19 of 21 53. Mohan, A.; Narayanan, S.; Sethuraman, S.; Krishnan, U.M. Novel resveratrol and 5-fluorouracil coencapsulated in PEGylated nanoliposomes improve chemotherapeutic efficacy of combination against head and neck squamous cell carcinoma. Biomed. Res. Int. 2014,2014, 424239. [CrossRef] [PubMed] 54. Pawar, H.; Surapaneni, S.K.; Tikoo, K.; Singh, C.; Burman, R.; Gill, M.S.; Suresh, S. Folic acid functionalized long-circulating co-encapsulated docetaxel and curcumin solid lipid nanoparticles: In vitro evaluation, pharmacokinetic and biodistribution in rats. Drug Deliv. 2016,23, 1453–1468. [CrossRef] 55. Liu, Q.; Li, J.; Pu, G.; Zhang, F.; Liu, H.; Zhang, Y. Co-delivery of baicalein and doxorubicin by hyaluronic acid decorated nanostructured lipid carriers for breast cancer therapy. Drug Deliv. 2016,23, 1364–1368. [CrossRef] [PubMed] 56. Barui, S.; Saha, S.; Mondal, G.; Haseena, S.; Chaudhuri, A. Simultaneous delivery of doxorubicin and curcumin encapsulated in liposomes of pegylated RGDK-lipopeptide to tumor vasculature. Biomaterials 2014,35, 1643–1656. [CrossRef] [PubMed] 57. Mussi, S.V.; Sawant, R.; Perche, F.; Oliveira, M.C.; Azevedo, R.B.; Ferreira, L.A.; Torchilin, V.P. Novel nanostructured lipid carrier co-loaded with doxorubicin and docosahexaenoic acid demonstrates enhanced in vitro activity and overcomes drug resistance in MCF-7/Adr cells. Pharm. Res. 2014,31, 1882–1892. [CrossRef] 58. Sarfraz, M.; Afzal, A.; Raza, S.M.; Bashir, S.; Madni, A.; Khan, M.W.; Ma, X.; Xiang, G. Liposomal co-delivered oleanolic acid attenuates doxorubicin-induced multi-organ toxicity in hepatocellular carcinoma. Oncotarget 2017,8, 47136–47153. [CrossRef] 59. Yang, Y.; Lu, X.; Liu, Q.; Dai, Y.; Zhu, X.; Wen, Y.; Xu, J.; Lu, Y.; Zhao, D.; Chen, X.; et al. Palmitoyl ascorbate and doxorubicin co-encapsulated liposome for synergistic anticancer therapy. Eur. J. Pharm. Sci. 2017,105, 219–229. [CrossRef] 60. Minaei, A.; Sabzichi, M.; Ramezani, F.; Hamishehkar, H.; Samadi, N. Co-delivery with nano-quercetin enhances doxorubicinmediated cytotoxicity against MCF-7 cells. Mol. Biol. Rep. 2016,43, 99–105. [CrossRef] 61. Oliveira, M.S.; Aryasomayajula, B.; Pattni, B.; Mussi, S.V.; Ferreira, L.A.M.; Torchilin, V.P. Solid lipid nanoparticles co-loaded with doxorubicin and alpha-tocopherol succinate are effective against drug-resistant cancer cells in monolayer and 3-D spheroid cancer cell models. Int. J. Pharm. 2016,512, 292–300. [CrossRef] 62. Li, Y.; Angelova, A.; Hu, F.; Garamus, V.M.; Peng, C.; Li, N.; Liu, J.; Liu, D.; Zou, A. pH Responsiveness of Hexosomes and Cubosomes for Combined Delivery of Brucea javanica Oil and Doxorubicin. Langmuir 2019,35, 14532–14542. [CrossRef] 63. Jiang, H.; Geng, D.; Liu, H.; Li, Z.; Cao, J. Co-delivery of etoposide and curcumin by lipid nanoparticulate drug delivery system for the treatment of gastric tumors. Drug Deliv. 2016,23, 3665–3673. [CrossRef] 64. Shukla, P.; Mathur, V.; Kumar, A.; Khedgikar, V.; Teja, V.B.; Chaudhary, D.; Kushwaha, P.; Bora, H.K.; Konwar, R.; Trivedi, R.; et al. Nanoemulsion based concomitant delivery of curcumin and etoposide: Impact on cross talk between prostate cancer cells and osteoblast during metastasis. J. Biomed. Nanotechnol. 2014,10, 3381–3391. [CrossRef] 65. Lu, Z.; Su, J.; Li, Z.; Zhan, Y.; Ye, D. Hyaluronic acid-coated, prodrug-based nanostructured lipid carriers for enhanced pancreatic cancer therapy. Drug Dev. Ind. Pharm. 2017,43, 160–170. [CrossRef] 66. Soe, Z.C.; Thapa, R.K.; Ou, W.; Gautam, M.; Nguyen, H.T.; Jin, S.G.; Ku, S.K.; Oh, K.T.; Choi, H.G.; Yong, C.S.; et al. Folate receptor-mediated celastrol and irinotecan combination delivery using liposomes for effective chemotherapy. Colloids Surf. B. Biointerfaces 2018,170, 718–728. [CrossRef] [PubMed] 67. Jain, A.; Sharma, G.; Kushwah, V.; Garg, N.K.; Kesharwani, P.; Ghoshal, G.; Singh, B.; Shivhare, U.S.; Jain, S.; Katare, O.P. Methotrexate and beta-carotene loaded-lipid polymer hybrid nanoparticles: A preclinical study for breast cancer. Nanomedicine 2017,12, 1851–1872. [CrossRef] [PubMed] 68. Meng, L.; Xia, X.; Yang, Y.; Ye, J.; Dong, W.; Ma, P.; Jin, Y.; Liu, Y. Co-encapsulation of paclitaxel and baicalein in nanoemulsions to overcome multidrug resistance via oxidative stress augmentation and P-glycoprotein inhibition. Int. J. Pharm. 2016 ,513, 8–16. [CrossRef] 69. Tang, B.; Fang, G.; Gao, Y.; Liu, Y.; Liu, J.; Zou, M.; Wang, L.; Cheng, G. Lipid-albumin nanoassemblies co-loaded with borneol and paclitaxel for intracellular drug delivery to C6 glioma cells with P-gp inhibition and its tumor targeting. Asian J. Pharm. Sci. 2015,10, 363–371. [CrossRef] 70. Abouzeid, A.H.; Patel, N.R.; Torchilin, V.P. Polyethylene glycol-phosphatidylethanolamine (PEG-PE)/vitamin E micelles for co-delivery of paclitaxel and curcumin to overcome multi-drug resistance in ovarian cancer. Int. J. Pharm. 2014 ,464, 178–184. [CrossRef] [PubMed] 71. Ganta, S.; Amiji, M. Coadministration of Paclitaxel and curcumin in nanoemulsion formulations to overcome multidrug resistance in tumor cells. Mol. Pharm. 2009,6, 928–939. [CrossRef] 72. Sarisozen, C.; Vural, I.; Levchenko, T.; Hincal, A.A.; Torchilin, V.P. PEG-PE-based micelles co-loaded with paclitaxel and cyclosporine A or loaded with paclitaxel and targeted by anticancer antibody overcome drug resistance in cancer cells. Drug Deliv. 2012,19, 169–176. [CrossRef] [PubMed] 73. Sawant, R.R.; Vaze, O.S.; Rockwell, K.; Torchilin, V.P. Palmitoyl ascorbate-modified liposomes as nanoparticle platform for ascorbate-mediated cytotoxicity and paclitaxel co-delivery. Eur. J. Pharm. Biopharm. 2010,75, 321–326. [CrossRef] [PubMed] 74. Gill, K.K.; Kaddoumi, A.; Nazzal, S. Mixed micelles of PEG(2000)-DSPE and vitamin-E TPGS for concurrent delivery of paclitaxel and parthenolide: Enhanced chemosenstization and antitumor efficacy against non-small cell lung cancer (NSCLC) cell lines. Eur. J. Pharm. Sci. Off. J. Eur. Fed. Pharm. Sci. 2012,46, 64–71. 75. Kabary, D.M.; Helmy, M.W.; Elkhodairy, K.A.; Fang, J.Y.; Elzoghby, A.O. Hyaluronate/lactoferrin layer-by-layer-coated lipid nanocarriers for targeted co-delivery of rapamycin and berberine to lung carcinoma. Colloids Surf. B Biointerfaces 2018 ,169, 183–194. [CrossRef] Pharmaceutics 2023,15, 1317 20 of 21 76. Webb, M.S.; Johnstone, S.; Morris, T.J.; Kennedy, A.; Gallagher, R.; Harasym, N.; Harasym, T.; Shew, C.R.; Tardi, P.; Dragowska, W.H.; et al. In vitro and in vivo characterization of a combination chemotherapy formulation consisting of vinorelbine and phosphatidylserine. Eur. J. Pharm. Biopharm. 2007,65, 289–299. [CrossRef] 77. Lúcio, M.; Lopes, C.M.; Oliveira, M.E.C.R. Functional Lipid Nanosystems in Cancer; Jenny Stanford Publishing: New York, NY, USA, 2021. 78. Mohan, P.; Rapoport, N. Doxorubicin as a molecular nanotheranostic agent: Effect of doxorubicin encapsulation in micelles or nanoemulsions on the ultrasound-mediated intracellular delivery and nuclear trafficking. Mol. Pharm. 2010 ,7, 1959–1973. [CrossRef] [PubMed] 79. Sriraman, S.K.; Salzano, G.; Sarisozen, C.; Torchilin, V. Anti-cancer activity of doxorubicin-loaded liposomes co-modified with transferrin and folic acid. Eur. J. Pharm. Biopharm. 2016,105, 40–49. [CrossRef] [PubMed] 80. Štˇerba, M.; Popelová, O.; Vávrová, A.; Jirkovský, E.; Kovaˇríková, P.; Geršl, V.; Šim˚unek, T. Oxidative Stress, Redox Signaling, and Metal Chelation in Anthracycline Cardiotoxicity and Pharmacological Cardioprotection. Antioxid. Redox Signal. 2012 ,18, 899–929. [CrossRef] [PubMed] 81. Nitiss, J.L. Targeting DNA topoisomerase II in cancer chemotherapy. Nat. Rev. Cancer 2009,9, 338. [CrossRef] 82. Sun, J.; Song, Y.; Lu, M.; Lin, X.; Liu, Y.; Zhou, S.; Su, Y.; Deng, Y. Evaluation of the antitumor effect of dexamethasone palmitate and doxorubicin co-loaded liposomes modified with a sialic acid-octadecylamine conjugate. Eur. J. Pharm. Sci. 2016 ,93, 177–183. [CrossRef] 83. Elbialy, N.S.; Mady, M.M. Ehrlich tumor inhibition using doxorubicin containing liposomes. Saudi Pharm. J. 2015 ,23, 182–187. [CrossRef] [PubMed] 84. Misra, R.; Sahoo, S.K. Intracellular trafficking of nuclear localization signal conjugated nanoparticles for cancer therapy. Eur. J. Pharm. Sci. 2010,39, 152–163. [CrossRef] 85. Qiu, L.; Qiao, M.; Chen, Q.; Tian, C.; Long, M.; Wang, M.; Li, Z.; Hu, W.; Li, G.; Cheng, L.; et al. Enhanced effect of pH-sensitive mixed copolymer micelles for overcoming multidrug resistance of doxorubicin. Biomaterials 2014 ,35, 9877–9887. [CrossRef] [PubMed] 86. Chakravarty, G.; Mathur, A.; Mallade, P.; Gerlach, S.; Willis, J.; Datta, A.; Srivastav, S.; Abdel-Mageed, A.B.; Mondal, D. Nelfinavir targets multiple drug resistance mechanisms to increase the efficacy of doxorubicin in MCF-7/Dox breast cancer cells. Biochimie 2016,124, 53–64. [CrossRef] 87. Wu, Y.; Zhang, Y.; Zhang, W.; Sun, C.; Wu, J.; Tang, J. Reversing of multidrug resistance breast cancer by co-delivery of P-gp siRNA and doxorubicin via folic acid-modified core-shell nanomicelles. Colloids Surf. B Biointerfaces 2016 ,138, 60–69. [CrossRef] 88. Shimpo, K.; Nagatsu, T.; Yamada, K.; Sato, T.; Niimi, H.; Shamoto, M.; Takeuchi, T.; Umezawa, H.; Fujita, K. Ascorbic acid and adriamycin toxicity. Am. J. Clin. Nutr. 1991,54, 1298s–1301s. [CrossRef] [PubMed] 89. Borska, S.; Chmielewska, M.; Wysocka, T.; Drag-Zalesinska, M.; Zabel, M.; Dziegiel, P. In vitro effect of quercetin on human gastric carcinoma: Targeting cancer cells death and MDR. Food Chem. Toxicol. 2012,50, 3375–3383. [CrossRef] [PubMed] 90. Kim, M.K.; Park, K.S.; Choo, H.; Chong, Y. Quercetin-POM (pivaloxymethyl) conjugates: Modulatory activity for P-glycoproteinbased multidrug resistance. Phytomedicine 2015,22, 778–785. [CrossRef] 91. Kim, J.H.; Li, Y.; Kim, M.S.; Kang, S.W.; Jeong, J.H.; Lee, D.S. Synthesis and evaluation of biotin-conjugated pH-responsive polymeric micelles as drug carriers. Int. J. Pharm. 2012,427, 435–442. [CrossRef] 92. Oliveira, M.S.; Mussi, S.V.; Gomes, D.A.; Yoshida, M.I.; Frezard, F.; Carregal, V.M.; Ferreira, L.A.M. α -Tocopherol succinate improves encapsulation and anticancer activity of doxorubicin loaded in solid lipid nanoparticles. Colloids Surf. B Biointerfaces 2016,140, 246–253. [CrossRef] [PubMed] 93. Gao, M.; Xu, Y.; Qiu, L. Enhanced combination therapy effect on paclitaxel-resistant carcinoma by chloroquine co-delivery via liposomes. Int. J. Nanomed. 2015,10, 6615–6632. [CrossRef] 94. Jang, S.H.; Wientjes, M.G.; Au, J.L. Kinetics of P-glycoprotein-mediated efflux of paclitaxel. J. Pharm. Pharmacol. Exp. Ther. 2001 , 298, 1236–1242. 95. Quan, F.; Pan, C.; Ma, Q.; Zhang, S.; Yan, L. Reversal effect of resveratrol on multidrug resistance in KBv200 cell line. Biomed. Pharm. Pharmacother. 2008,62, 622–629. [CrossRef] [PubMed] 96. Longley, D.B.; Harkin, D.P.; Johnston, P.G. 5-fluorouracil: Mechanisms of action and clinical strategies. Nat. Rev. Cancer 2003 ,3, 330–338. [CrossRef] [PubMed] 97. Yang, Z.; Gao, D.; Cao, Z.; Zhang, C.; Cheng, D.; Liu, J.; Shuai, X. Drug and gene co-delivery systems for cancer treatment. Biomater. Sci. 2015,3, 1035–1049. [CrossRef] [PubMed] 98. Saraswathy, M.; Gong, S. Recent developments in the co-delivery of siRNA and small molecule anticancer drugs for cancer treatment. Mater. Today 2014,17, 298–306. [CrossRef] 99. Mitchell, M.J.; Billingsley, M.M.; Haley, R.M.; Wechsler, M.E.; Peppas, N.A.; Langer, R. Engineering precision nanoparticles for drug delivery. Nat. Rev. Drug Discov. 2021,20, 101–124. [CrossRef] 100. Fenton, O.S.; Olafson, K.N.; Pillai, P.S.; Mitchell, M.J.; Langer, R. Advances in Biomaterials for Drug Delivery. Adv. Mater. 2018 , 30, 1705328. [CrossRef] 101. Jogdeo, C.M.; Panja, S.; Kanvinde, S.; Kapoor, E.; Siddhanta, K.; Oupický, D. Advances in Lipid-Based Codelivery Systems for Cancer and Inflammatory Diseases. Adv. Healthc. Mater. 2023,12, 2202400. [CrossRef] Pharmaceutics 2023,15, 1317 21 of 21 102. Yu, Q.; Zhang, B.; Zhou, Y.; Ge, Q.; Chang, J.; Chen, Y.; Zhang, K.; Peng, D.; Chen, W. Co-delivery of gambogenic acid and VEGF-siRNA with anionic liposome and polyethylenimine complexes to HepG2 cells. J. Liposome Res. 2019 ,29, 322–331. [CrossRef] 103. Xu, X.; Liu, A.; Bai, Y.; Li, Y.; Zhang, C.; Cui, S.; Piao, Y.; Zhang, S. Co-delivery of resveratrol and p53 gene via peptide cationic liposomal nanocarrier for the synergistic treatment of cervical cancer and breast cancer cells. J. Drug Deliv. Sci. Technol. 2019 ,51, 746–753. [CrossRef] 104. Jose, A.; Labala, S.; Venuganti, V.V.K. Co-delivery of curcumin and STAT3 siRNA using deformable cationic liposomes to treat skin cancer. J. Drug Target. 2017,25, 330–341. [CrossRef] 105. Jose, A.; Labala, S.; Ninave, K.M.; Gade, S.K.; Venuganti, V.V.K. Effective Skin Cancer Treatment by Topical Co-delivery of Curcumin and STAT3 siRNA Using Cationic Liposomes. AAPS PharmSciTech 2018,19, 166–175. [CrossRef] 106. Muddineti, O.S.; Shah, A.; Rompicharla, S.V.K.; Ghosh, B.; Biswas, S. Cholesterol-grafted chitosan micelles as a nanocarrier system for drug-siRNA co-delivery to the lung cancer cells. Int. J. Biol. Macromol. 2018,118, 857–863. [CrossRef] [PubMed] 107. Jia, F.; Li, Y.; Deng, X.; Wang, X.; Cui, X.; Lu, J.; Pan, Z.; Wu, Y. Self-assembled fluorescent hybrid nanoparticles-mediated collaborative lncRNA CCAT1 silencing and curcumin delivery for synchronous colorectal cancer theranostics. J. Nanobiotechnol. 2021,19, 238. [CrossRef] 108. Rana, M.S.; Ediriweera, M.K.; Rajagopalan, U.; Karunaratne, D.N.; Tennekoon, K.H.; Samarakoon, S.R. A new liposomal nanocarrier for co-delivery of gedunin and p-glycoprotein siRNA to target breast cancer stem cells. Nat. Prod. Prod. Res. 2022 ,36, 6389–6392. [CrossRef] 109. Hientz, K.; Mohr, A.; Bhakta-Guha, D.; Efferth, T. The role of p53 in cancer drug resistance and targeted chemotherapy. Oncotarget 2017,8, 8921–8946. [CrossRef] [PubMed] 110. Eftekhari, R.B.; Maghsoudnia, N.; Samimi, S.; Zamzami, A.; Dorkoosh, F.A. Co-Delivery Nanosystems for Cancer Treatment: A Review. Pharm. Nanotechnol. 2019,7, 90–112. [CrossRef] 111. Oliveto, S.; Mancino, M.; Manfrini, N.; Biffo, S. Role of microRNAs in translation regulation and cancer. World J. Biol. Chem. 2017 , 8, 45–56. [CrossRef] 112. Yu, X.J.; Han, Q.B.; Wen, Z.S.; Ma, L.; Gao, J.; Zhou, G.B. Gambogenic acid induces G1 arrest via GSK3 β -dependent cyclin D1 degradation and triggers autophagy in lung cancer cells. Cancer Lett. 2012,322, 185–194. [CrossRef] 113. Su, J.; Cheng, H.; Zhang, D.; Wang, M.; Xie, C.; Hu, Y.; Chang, H.C.; Li, Q. Synergistic effects of 5-fluorouracil and gambogenic acid on A549 cells: Activation of cell death caused by apoptotic and necroptotic mechanisms via the ROS-mitochondria pathway. Biol. Pharm. Bull. 2014,37, 1259–1268. [CrossRef] 114. Tang, X.; Sun, J.; Ge, T.; Zhang, K.; Gui, Q.; Zhang, S.; Chen, W. PEGylated liposomes as delivery systems for Gambogenic acid: Characterization and in vitro/in vivo evaluation. Colloids Surf. B Biointerfaces 2018,172, 26–36. [CrossRef] 115. Patwardhan, C.A.; Fauq, A.; Peterson, L.B.; Miller, C.; Blagg, B.S.J.; Chadli, A. Gedunin inactivates the co-chaperone p23 protein causing cancer cell death by apoptosis. J. Biol. Chem. 2013,288, 7313–7325. [CrossRef] [PubMed] 116. Nwokwu, C.D.U.; Samarakoon, S.R.; Karunaratne, D.N.; Katuvawila, N.P.; Pamunuwa, G.K.; Ediriweera, M.K.; Tennekoon, K.H. Induction of apoptosis in response to improved gedunin by liposomal nano-encapsulation in human non-small-cell lung cancer (NCI-H292) cell line. Trop. J. Pharm. Res. 2017,16, 2079–2087. [CrossRef] 117. Hua, S.; de Matos, M.B.C.; Metselaar, J.M.; Storm, G. Current Trends and Challenges in the Clinical Translation of Nanoparticulate Nanomedicines: Pathways for Translational Development and Commercialization. Front. Pharmacol. 2018 ,9, 790. [CrossRef] [PubMed] 118. Navya, P.N.; Kaphle, A.; Srinivas, S.P.; Bhargava, S.K.; Rotello, V.M.; Daima, H.K. Current trends and challenges in cancer management and therapy using designer nanomaterials. Nano Converg. 2019,6, 23. [CrossRef] [PubMed] 119. Patra, J.K.; Das, G.; Fraceto, L.F.; Campos, E.V.R.; Rodriguez-Torres, M.d.P.; Acosta-Torres, L.S.; Diaz-Torres, L.A.; Grillo, R.; Swamy, M.K.; Sharma, S.; et al. Nano based drug delivery systems: Recent developments and future prospects. J. Nanobiotechnol. 2018,16, 71. [CrossRef] 120. Vitorino, C.; Lopes, C.M.; Lúcio, M. Nanomedicine and Drug Delivery Approaches. In Organelle and Molecular Targeting; CRC Press: Boca Raton, FL, USA, 2021; pp. 23–112. 121. Maniam, G.; Mai, C.-W.; Zulkefeli, M.; Dufès, C.; Tan, D.M.-Y.; Fu, J.-Y. Challenges and Opportunities of Nanotechnology as Delivery Platform for Tocotrienols in Cancer Therapy. Front. Pharmacol. 2018,9, 1358. [CrossRef] 122. Angelova, A.; Garamus, V.M.; Angelov, B.; Tian, Z.; Li, Y.; Zou, A. Advances in structural design of lipid-based nanoparticle carriers for delivery of macromolecular drugs, phytochemicals and anti-tumor agents. Adv. Colloid Interface Sci. 2017 ,249, 331–345. [CrossRef] 123. Fernandes, E.; Soares, T.B.; Gonçalves, H.; Lúcio, M. Spectroscopic Studies as a Toolbox for Biophysical and Chemical Characterization of Lipid-Based Nanotherapeutics. Front. Chem. 2018,6, 323. [CrossRef] 124. Tenchov, R.; Bird, R.; Curtze, A.E.; Zhou, Q. Lipid Nanoparticles—From Liposomes to mRNA Vaccine Delivery, a Landscape of Research Diversity and Advancement. ACS Nano 2021,15, 16982–17015. [CrossRef] [PubMed] Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.