O iginal Resea ch
P o-in lamma o y a y acid p o ile and colo ec al cance
isk: A Mendelian andomisa ion analysis
Sebas ian May-Wilson
a,1
, Ami Sud
a,1
, Philip J. Law
a,1
, Kimmo Palin
b,c
,
Sa i Tuupanen
b,c
, Alexand a Gyl e
b,c
, Ul ika A. Ha
¨nninen
b,c
,
Ta iana Cajuso
b,c
, Tomas Tanskanen
b,c
, Johanna Kondelin
b,c
,
Ee i Kaasinen
b,c
, An i-Pekka Sa in
d
, Johan G. E iksson
g,h,i
,
Ha i Rissanen
g
, Paul Knek
g
, Ee o Pukkala
j,k
, Pekka Jousilah i
g
,
Veikko Salomaa
g
, Samuli Ripa i
d,e,
, Aa no Palo ie
d,l,m,n
,
Lau a Renkonen-Sinisalo
o
, Anna Lepis o
¨
o
, Jan Bo
¨hm
p
,
Jukka-Pekka Mecklin
q
, Nada A. Al-Tassan
, Clai e Palles
s
,
Susan M. Fa ing on
, Ma ia N. Timo ee a
, B ian F. Meye
,
Salma M. Wakil
, Ha y Campbell
u
, Ch is ophe G. Smi h
,
Shelley Idziaszczyk
, Timo hy S. Maughan
w
, Da id Fishe
x
,
Rachel Ke
y
, Da id Ke
z
, Michael N. Passa elli
aa
,
Jane C. Figuei edo
ab,ac
, Daniel D. Buchanan
ad,ae
, Aung K. Win
ae
,
John L. Hoppe
ae
, Ma k A. Jenkins
ae
, No alane M. Lindo
a
,
Polly A. Newcomb
ag
, S e en Gallinge
ah
, Da id Con i
ai
,
F ed Schumache
ai
, G aham Casey
aj
, Lau i A. Aal onen
b,c
,
Je emy P. Cheadle
, Ian P. Tomlinson
s
, Malcolm G. Dunlop
,
Richa d S. Houls on
a,
*
a
Di ision o Gene ics and Epidemiology, The Ins i u e o Cance Resea ch, London, SW7 3RP, UK
b
Genome-Scale Biology Resea ch P og am, Resea ch P og ams Uni , Uni e si y o Helsinki, Helsinki, 00014, Finland
c
Depa men o Medical and Clinical Gene ics, Medicum, Uni e si y o Helsinki, Helsinki, 00014, Finland
d
Ins i u e o Molecula Medicine Finland (FIMM), Uni e si y o Helsinki, Helsinki, 00014, Finland
e
Wellcome T us Sange Ins i u e, Wellcome T us Genome Campus, Hinx on, Camb idge, CB10 1SA, UK
Depa men o Public Heal h, Uni e si y o Helsinki, Helsinki, 00014, Finland
g
Na ional Ins i u e o Heal h and Wel a e, Helsinki, 00271, Finland
h
Folkha
¨lsan Resea ch Cen e, Helsinki, 00250, Finland
i
Uni o Gene al P ac ice and P ima y Heal h Ca e, Uni e si y o Helsinki and Helsinki Uni e si y Hospi al, Helsinki, 00014,
Finland
*Co esponding au ho : Di ision o Gene ics and Epidemiology, The Ins i u e o Cance Resea ch, 15 Co swold Road, London, SM2 5NG, UK.
Fax: þ44 (0) 722 4365.
E-mail add ess: [email p o ec ed] (R.S. Houls on).
1
These au ho s con ibu ed equally o his wo k.
h p://dx.doi.o g/10.1016/j.ejca.2017.07.034
0959-8049/ª2017 The Au ho s. Published by Else ie L d. This is an open access a icle unde he CC BY license (h p://c ea i ecommons.o g/
licenses/by/4.0/).
A ailable online a www.sciencedi ec .com
ScienceDi ec
jou nal homepage: www.ejcance .com
Eu opean Jou nal o Cance 84 (2017) 228e238
j
Finnish Cance Regis y, Ins i u e o S a is ical and Epidemiological Cance Resea ch, Helsinki, 00130, Finland
k
School o Heal h Sciences, Uni e si y o Tampe e, Tampe e, 33014, Finland
l
Analy ic and T ansla ional Gene ics Uni , Depa men o Medicine, Massachuse s Gene al Hospi al, Bos on, MA, 02114,
USA
m
P og am in Medical and Popula ion Gene ics, The B oad Ins i u e o MIT and Ha a d, Camb idge, MA, 02142, USA
n
Depa men o Neu ology, Massachuse s Gene al Hospi al, Bos on, MA, 02114, USA
o
Abdominal Cen e , Depa men o Su ge y, Helsinki Uni e si y Hospi al, Helsinki, 00029, Finland
p
Depa men o Pa hology, Cen al Finland Cen al Hospi al, Jy a
¨skyla
¨, 40620, Finland
q
Depa men o Su ge y, Jy a
¨skyla
¨Cen al Hospi al, Uni e si y o Eas e n Finland, Jy a
¨skyla
¨, 40620, Finland
Depa men o Gene ics, King Faisal Specialis Hospi al and Resea ch Cen e , Riyadh, 12713, Saudi A abia
s
Molecula & Popula ion Gene ics Labo a o y, Wellcome T us Cen e o Human Gene ics, Uni e si y o Ox o d, Ox o d,
OX3 7BN, UK
Colon Cance Gene ics G oup, Uni e si y o Edinbu gh and MRC Human Gene ics Uni , Wes e n Gene al Hospi al,
Edinbu gh, EH4 2XU, UK
u
Cen e o Popula ion Heal h Sciences, Uni e si y o Edinbu gh, Edinbu gh, EH8 9AG, UK
Di ision o Cance and Gene ics, School o Medicine, Ca di Uni e si y, Ca di , CF14 4XN, UK
w
CRUK/MRC Ox o d Ins i u e o Radia ion Oncology, Uni e si y o Ox o d, Ox o d, OX3 7DQ, UK
x
MRC Clinical T ials Uni , A ia ion House, London, WC2B 6NH, UK
y
Ox o d Cance Cen e, Depa men o Oncology, Uni e si y o Ox o d, Chu chill Hospi al, Ox o d, OX3 7LE, UK
z
Nu ield Depa men o Clinical Labo a o y Sciences, Uni e si y o Ox o d, John Radcli e Hospi al, Ox o d, OX3 9DU, UK
aa
Depa men o Epidemiology, Geisel School o Medicine a Da mou h, Da mou h-Hi chcock Medical Cen e , Lebanon,
NH, 03756, USA
ab
Samuel Oschin Comp ehensi e Cance Cen e , Ceda s-Sinai Medical Cen e , Los Angeles, CA, USA
ac
Keck School o Medicine, Uni e si y o Sou he n Cali o nia, Los Angeles, CA, USA
ad
Colo ec al Oncogenomics G oup, Gene ic Epidemiology Labo a o y, Depa men o Pa hology, The Uni e si y o
Melbou ne, Vic o ia, 3010, Aus alia
ae
Cen e o Epidemiology and Bios a is ics, The Uni e si y o Melbou ne, Vic o ia, 3010, Aus alia
a
Depa men o Heal h Sciences Resea ch, Mayo Clinic, Sco sdale, AZ, 85259, USA
ag
Cance P e en ion P og am, F ed Hu chinson Cance Resea ch Cen e , Sea le, WA, 98109, USA
ah
Lunen eld-Tanenbaum Resea ch Ins i u e, Moun Sinai Hospi al, To on o, ON, M5G 1X5, Canada
ai
Depa men o P e en i e Medicine, Uni e si y o Sou he n Cali o nia, Los Angeles, CA, 90033, USA
aj
Cen e o Public Heal h Genomics, Uni e si y o Vi ginia, Cha lo es ille, VA, 22908, USA
Recei ed 16 Decembe 2016; ecei ed in e ised o m 20 July 2017; accep ed 22 July 2017
A ailable online 19 Augus 2017
KEYWORDS
Mendelian
andomisa ion;
Colo ec al cance ;
Risk;
Plasma a y acids;
Fa y acids
Abs ac Backg ound: While die a y a has been es ablished as a isk ac o o colo ec al
cance (CRC), associa ions be ween a y acids (FAs) and CRC ha e been inconsis en . Using
Mendelian andomisa ion (MR), we sough o e alua e associa ions be ween polyunsa u a ed
(PUFA), monounsa u a ed (MUFA) and sa u a ed FAs (SFAs) and CRC isk.
Me hods: We analysed geno ype da a on 9254 CRC cases and 18,386 con ols o Eu opean
ances y. Ex e nally weigh ed polygenic isk sco es we e gene a ed and used o e alua e asso-
cia ions wi h CRC pe one s anda d de ia ion inc ease in gene ically de ined plasma FA le els.
Resul s: Risk educ ion was obse ed o oleic and palmi oleic MUFAs (OR
OA
Z0.77, 95%
CI: 0.65e0.92, PZ3.9 10
3
;OR
POA
Z0.36, 95% CI: 0.15e0.84, PZ0.018). PUFAs li-
noleic and a achidonic acid had nega i e and posi i e associa ions wi h CRC espec i ely
(OR
LA
Z0.95, 95% CI: 0.93e0.98, PZ3.7 10
4
;OR
AA
Z1.05, 95% CI: 1.02e1.07,
PZ1.7 10
4
).The SFA s ea ic acid was associa ed wi h inc eased CRC isk
(OR
SA
Z1.17, 95% CI: 1.01e1.35, PZ0.041).
Conclusion: Resul s om ou analysis a e b oadly consis en wi h a p o-in lamma o y FA
p o ile ha ing a de imen al e ec in e ms o CRC isk.
ª2017 The Au ho s. Published by Else ie L d. This is an open access a icle unde he CC
BY license (h p://c ea i ecommons.o g/licenses/by/4.0/).
S. May-Wilson e al. / Eu opean Jou nal o Cance 84 (2017) 228e238 229
1. In oduc ion
Colo ec al cance (CRC) is one o he mos common
cance s and a majo cause o cance - ela ed mo ali y in
economically de eloped coun ies [1]. Geog aphical
di e ences in CRC incidence be ween coun ies and
mig a ion s udies ha e es ablished he impo ance o
li es yle and die as majo de e minan s o CRC isk [2].
Wo ldwide CRC is cu en ly diagnosed in o e one
million indi iduals annually; howe e , i s incidence is se
o inc ease wi h adop ion o wes e n li es yles in de el-
oping coun ies [3]. Gi en he impo ance o die as a
isk ac o o CRC, i s modi ica ion o e s he p ospec
o impac ing signi ican ly on disease incidence h ough
public heal h ini ia i es.
Die a y a has been widely implica ed as a isk ac o
o cance , and me a-analyses o epidemiological s udies
ha e ended o associa e CRC isk wi h a highe con-
sump ion o ed and p ocessed mea [4]. The associa ion
be ween a in ake on cance isk howe e , is likely o
depend no only on he quan i y, bu also on he speci ic
ype o a y acid (FA). Animal models and ecological
s udies ha e ended o implica e animal a [5], sa u a ed
a y acid (SFA) and ce ain omega-6 polyunsa u a ed
a y acids (u-6 PUFAs) wi h an inc eased isk, and u-3
PUFA in ake wi h a educed isk [6e8]. E idence o a
causal ela ionship wi h in ake o speci ic ypes o a
om epidemiological s udies has howe e la gely been
inconclusi e. Reasons o inconsis encies in obse a-
ional s udies include he inhe en p oblem o elici ing
accu a e measu emen s o long- e m die , con ounding
and e e se causa ion [9].
Mendelian andomisa ion (MR) analysis ep esen s
an adjunc o he con en ional epidemiological obse -
a ional s udy o examining associa ions be ween an
exposu e wi h a disease. The MR s a egy makes use o
allelic a ian s ha a e andomly assigned du ing
meiosis and a e obus ly associa ed wi h ai s o in e -
es , as ins umen al a iables (IVs). Using gene ically
de ined IVs as p oxies o modi iable exposu e a oids
con ounding by en i onmen al ac o s, is no subjec o
e e se causali y and can in o m on li e-long exposu e
[10,11]. Since s udies ha e shown ha FA in ake in-
luences plasma le els o FAs in heo y MR makes an
a ac i e s a egy o link die a y FA o CRC isk
[12,13].
We ha e he e o e sough o iden i y associa ions
be ween gene ically p edic ed plasma PUFA, MUFAs
and SFA le els and CRC isk. Speci ically: (1) he u-6
PUFAs, linoleic acid (LA), a achidonic acid (AA) and
dihomo-g-linolenic acid (DGLA); (2) he u-3 PUFAs,
eicosapen aenoic acid (EPA), docosapen aenoic acid
(DPA) and docosahexaenoic acid (DHA); (3) he
MUFAs, oleic acid (OA) and palmi oleic acid (POA);
and (4) he SFAs, palmi ic acid (PA), a achidic acid and
s ea ic acid (SA).
2. Me hods
2.1. Colo ec al cance da ase s
We in es iga ed he ela ionship be ween gene ic isk
sco es o le els o MUFAs, PUFAs, and SFAs and
CRC isk adop ing a wo-sample MR s a egy using
da a om se en epo ed genome-wide associa ion
s udies (GWAS) o CRC (Table 1). B ie ly, hese GWAS
we e based on indi iduals wi h Eu opean ances y:
CCFR1, CCFR2, COIN, FINLAND, UK1, Sco land1
and VQ58 [14]. Each s udy was app o ed by espec i e
ins i u ional e hics e iew boa d and pe o med/con-
duc ed in acco dance wi h he Decla a ion o Helsinki.
2.2. Geno yping da a
Comp ehensi e de ails o he geno yping and quali y
con ol o he se en GWAS ha e been p e iously e-
po ed [14]. B ie ly, we excluded single nucleo ide poly-
mo phisms (SNPs) wi h a mino allele equency o
<1%, low call a e <95%, hose SNPs iola ing Ha -
dyeWeinbe g equilib ium, and indi iduals wi h non-
Eu opean ances y as assessed using da a om Hap-
Map 2 [15]. IMPUTE 2 so wa e [16] was used o
eco e un yped SNP geno ypes using a me ged e e -
ence panel consis ing o Sequencing Ini ia i e Suomi
( o he FINLAND da a) o UK10K ( o he emaining
da a) and 1000 Genomes P ojec da a [17,18]. Poo ly
impu ed SNPs, de ined by an INFO sco e o <0.9, we e
excluded. Summa y s a is ics om he se en GWAS
we e used o calcula e he odds a ios (ORs) o FA-
ela ed SNPs.
2.3. Gene a ian s used o cons uc gene ic isk sco es
Gene ic isk sco es o IVs o each plasma FA we e
de eloped om SNPs p e iously iden i ied by The Co-
ho s o Hea and Aging Resea ch in Genomic
Epidemiology (CHARGE) Conso ium. We conside ed
SNPs associa ed a genome-wide signi icance (i.e.
P5.0 10
8
) in indi iduals wi h Eu opean Ances y.
To a oid co-linea i y be ween SNPs o each FA we
imposed a h eshold
2
alue o 0.01 o linkage
disequilib ium (LD) including only he SNPs wi h he
s onges e ec on he ai in gene ic isk sco es (Table
2,[19e22]). Fo each iden i ied SNP, we eco e ed he
ch omosome posi ions, he isk alleles, associa ion es i-
ma es and s anda d e o s. Fo each SNP, he allele ha
was associa ed wi h inc eased FA le el was conside ed
he e ec allele.
2.4. S a is ical analysis
The associa ion be ween he plasma le el o each FA
and CRC was examined using MR on summa y
S. May-Wilson e al. / Eu opean Jou nal o Cance 84 (2017) 228e238230
Table 1
Summa y o he se en colo ec al cance genome-wide associa ion s udies.
Se ies S udy se ing S udy cen e Geno yping pla o m No. cases No. con ols
CCFR1 Colon Cance Family Regis y Uni e si y o Sou he n
Cali o nia
Illumina 1M, 1M Duo 1290 1055
CCFR2 Colon Cance Family Regis y Uni e si y o Sou he n
Cali o nia
Illumina 1M, Omni exp ess 796 2236
COIN COIN ial: Mul icen e s udy o
ce uximab and o he he apies in
me as a ic CRC. Con ols we e unselec ed
blood dono s
Ca di Uni e si y A yme ix Axiom 2244 2162
FINLAND Finnish Colo ec al Cance P edisposi ion
S udy
Helsinki Uni e si y Illumina 610K/Illumina
HumanOmni2.5M
1172 8266
UK1 CORGI (colo ec al Tumou Gene
Iden i ica ion Conso ium)
Ox o d Uni e si y Illumina Hap550 940 965
Sco land1 COGS (Colo ec al Cance Suscep ibili y
S udy)
Edinbu gh Uni e si y Illumina Hap300/240S 1012 1012
VQ58 Cases: VICTOR, pos - ea men s ages o
a phase III, andomised ial o o ecoxib
(VIOXX) in pa ien s a e po en ially
cu a i e he apy. QUASAR2, mul i-cen e
s udy o capeci abine be acizumab as
adju an ea men . 1958 Bi h coho
con ols
Ox o d Uni e si y Illumina Hap300/370,
Illumina 1M
1800 2690
Table 2
E ec sizes o plasma a y acid con en (pe s anda d de ia ion inc ease in le els) o genome-wide signi ican (P<510
8
) ins umen al
a iables epo ed by CHARGE conso ium.
FA sub ype Fa y acid SNP ID Ch Posi ion (bp)
a
Allele bS dE P- alue Va iance
explained
b
SFA A achidic acid (20:0) s680379 20 12917400 A/G 0.098 0.01 5.81 10
13
e
Palmi ic acid (PA) (16:0) s2391388 1 95485825 C/A 0.18 0.03 2.72 10
11
0.21e0.98%
S ea ic acid (SA) (18:0) s6675668 1 95515637 G/T 0.17 0.02 2.16 10
18
0.37e1.39%
s11119805 1 211918244 T/A 0.17 0.03 2.8 10
09
<0.01e0.72
s102275 11 61557803 T/C 0.18 0.02 1.33 10
20
0.33e1.34%
u-3 PUFA Docosahexaenoic acid
(DHA) (22:6n-3)
s2236212 6 10995015 G/C 0.11 0.01 1.26 10
15
0.7%
Docosapen aenoic acid
(DPA) (22:5n-3)
s780094 2 27741237 T/C 0.02 0.003 9.04 10
09
e
s3734398 6 10982973 C/T 0.04 0.003 9.71 10
43
8.6%
s174547 11 61570783 T/C 0.07 0.003 3.79 10
154
2.8%
Eicosapen aenoic acid
(EPA) (20:5n-3)
s3798713 6 11008622 C/G 0.035 0.005 1.93 10
12
0.4%
u-6 PUFA A achidonic acid
(AA) (20:4n-6)
s174547 11 61570783 T/C 1.69 0.03 3.30 10
971
3.7e37.6%
s16966952 16 15135943 G/A 0.2 0.03 2.43 10
10
0.1e0.6%
Dihomo-g-linolenic acid
(DGLA) (20:3n-6)
s174547 11 61570783 C/T 0.36 0.01 2.63 10
151
8.7e11.1%
s16966952 16 15135943 G/A 0.22 0.02 7.55 10
65
2.0e4.5%
Linoleic acid (LA)
(18:2n-6)
s10740118 10 65101207 G/C 0.25 0.04 8.08 10
09
0.2e0.7%
s174547 11 61570783 C/T 1.47 0.04 4.98 10
274
7.6e18.1%
s16966952 16 15135943 A/G 0.35 0.04 1.23 10
15
0.5e2.5%
u-7 MUFA Palmi oleic acid
(POA) (16:1n-7)
s780093 2 27742603 T/C 0.02 0.003 9.80 10
10
0.23e0.93%
s6722456 2 134529091 G/A 0.05 0.009 4.12 10
08
<0.01e0.57
s603424 10 102075479 G/A 0.03 0.004 5.69 10
15
0.28e1.57%
s11190604 10 102302457 G/A 0.02 0.004 5.69 10
09
0.02e0.71%
s102275 11 61557803 C/T 0.02 0.003 6.60 10
13
0.15e1.03%
u-9 MUFA Oleic acid
(OA) (18:1n-9)
s102275 11 61557803 C/T 0.23 0.02 2.19 10
32
0.32e2.14%
FA, a y acid; SNP, single nucleo ide polymo phism; bp, base pai ; SFA, sa u a ed a y acid; MUFA, monounsa u a ed a y acid; PUFA,
polyunsa u a ed a y acid; S dE , s anda d e o . E ec allele in luencing each FA ai is ma ked in bold.
a
hg19 NCBI build.
b
Taken om CHARGE conso ium, as a pe cen age o o al se um a y acids, calcula ed by (b
2
*2*MAF*(1-MAF))/Va (Y) whe e bis he
eg ession coe icien , MAF is he mino allele equency and Va (Y) is he a iance in le els o he a y acid. IVs ob ained om Re s. [19,20,22].
S. May-Wilson e al. / Eu opean Jou nal o Cance 84 (2017) 228e238 231
s a is ics as pe Bu gess (2015) [23]. The a io es ima e
ðbbÞo all SNPs associa ed wi h each a y acid, com-
bined, on CRC was calcula ed as ollows:
bbZPkXkYks2
Yk
PkX2
ks2
Yk
:
whe e X
k
co esponds o he associa ion o SNP k(as
log o he OR pe isk allele) wi h he a y acid ai Y,
Y
k
is he associa ion be ween SNP kand CRC isk (as
log o he OR) wi h s anda d e o sYk. The es ima e o
ðbbÞ ep esen s he causal inc ease in he log odds o he
CRC, pe uni change in a y acids. The s anda d e o
o he combined a io es ima e is gi en by:
sebbZffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
1
PkX2
ks2
Yk
s:
A me a-analysis o s a is ics o each speci ic FA
gene a ed o each CRC coho was combined unde
ixed-e ec s models o de i e he summa y ORs and
con idence in e als (CIs). To assess he impac o be-
ween s udy he e ogenei y, we also de i ed ORs unde a
andom-e ec s model.
A cen al ene in MR is he absence o pleio opy
(i.e. a gene in luencing mul iple ai s) be ween he SNPs
in luencing CRC isk and FA le els. This would be
e ealed as de ia ion om a linea ela ionship be ween
SNPs and hei e ec size o any FA and CRC isk. To
examine o iola ion o he s anda d IV assump ions in
ou analysis, we pe o med in e se a ian weigh ed
(IVW) and MR-Egge eg ession es s [24].
We conside ed a signi icance le el o P0.05 as
being sa is ac o y o de i e a conclusion. While o di-
na ily i would be app op ia e o impose a Bon e oni-
co ec ed h eshold, his assumes an independence o
IVs ac oss all FA ai s, which is no he case in he
p esen analysis. All s a is ical analyses we e unde aken
using R e sion 3.1 so wa e [25].
2.5. Exp ession quan i a i e ai locus analysis
To examine he ela ionship be ween SNP geno ype and
exp ession o FA me abolism genes, we pe o med
exp ession quan i a i e ai locus (eQTL) analysis using
da a om The Cance Genome A las (TCGA) and he
geno ype issue exp ession (GTEx)p ojec [26,27].
3. Resul s
The FA-associa ed gene ic a ian s and hei GWAS-
epo ed cha ac e is ics ha we e used o de i e IVs o
FAs a e de ailed in Table 2. A educed isk o CRC was
obse ed o gene ic a ian s associa ed wi h inc eases in
he MUFAs s udied (Table 3). In all bu one o he se en
coho s inc eased le els o OA we e associa ed wi h
educed CRC isk (Fig. 1). In he me a-analysis o hese
se en coho s he OR
OA
was 0.77 (95% CI: 0.65e0.92,
PZ3.9 10
3
) wi h li le e idence o be ween-s udy
he e ogenei y (P
he
Z0.23, I
2
Z26%). Simila ly,
inc eased le els o POA we e associa ed wi h educed
CRC isk wi h an OR
POA
o 0.36 (95% CI: 0.15e0.84,
PZ0.018, P
he
Z0.08, I
2
Z47%; Fig. 1).
The u-6 PUFAs LA and AA bo h showed associa-
ion wi h CRC isk, bu in di e en di ec ions. Speci -
ically, LA was associa ed wi h educed isk
(OR
LA
Z0.95, 95% CI: 0.93e0.98, PZ3.7 10
4
,
P
he
Z0.03, I
2
Z57%; Fig. 1) and AA wi h an inc eased
isk (OR
AA
Z1.05, 95% CI: 1.02e1.07, PZ1.7 10
4
,
P
he
Z0.03, I
2
Z56%). The associa ion be ween one
s anda d de ia ion inc ease in each o he o he PUFAs
de ined by hei espec i e IVs and CRC isk we e null
(Supplemen a y Fig. 1).
O he h ee SFAs s udied, inc eased SA was nomi-
nally associa ed wi h CRC isk (OR
SA
Z1.17, 95% CI:
1.01e1.35, PZ0.041, P
he
Z0.04, I
2
Z55%).
To o mally assess he impac o he e ogenei y on
s udy indings we de i ed ORs unde a andom-e ec s
Table 3
Odds a ios (ORs) and 95% con idence in e als (CI) o one s anda d de ia ion inc ease in gene ically p edic ed plasma a y acid le els and
colo ec al cance isk.
Fa y acid Signi ican associa ions
OR ( ixed
e ec s)
95% CI
( ixed e ec s)
P- alue
( ixed e ec s)
OR ( andom
e ec s)
95% CI
( andom
e ec s)
P- alue
( andom
e ec s)
I
2
P
he
A achidic acid 0.92 0.61e1.39 0.7 0.93 0.61e1.40 0.71 3% 0.41
Palmi ic acid (PA) 0.97 0.78e1.21 0.82 0.97 0.78e1.21 0.82 0% 0.47
S ea ic acid (SA) 1.16 1.01e1.35 0.04 1.2 0.95e1.49 0.12 55% 0.04
Docosahexaenoic acid (DHA) 1.32 0.94e1.87 0.11 1.32 0.94e1.87 0.11 0% 0.65
Docosapen aenoic acid (DPA) 1.58 0.99e2.52 0.06 1.63 0.97e2.73 0.06 17% 0.3
Eicosapen aenoic acid (EPA) 0.39 0.13e1.21 0.1 0.39 0.13e1.21 0.1 0% 0.57
A achidonic acid (AA) 1.05 1.02e1.07 1.7 10
4
1.05 1.02e1.09 4.9 10
3
56% 0.03
Dihomo-g-linolenic acid (DGLA) 0.91 0.83e1.00 0.06 0.95 0.80e1.01 0.07 23% 0.26
Linoleic acid (LA) 0.95 0.93e0.98 3.7 10
4
0.95 0.91e0.99 8.9 10
3
57% 0.03
Oleic acid (OA) 0.77 0.65e0.92 3.9 10
3
0.76 0.62e0.94 9.7 10
3
26% 0.23
Palmi oleic acid (POA) 0.36 0.15e0.84 0.018 0.32 0.10e1.07 0.06 47% 0.08
P
he
,P- alue o he e ogenei y; I
2
, p opo ion o he o al a ia ion due o he e ogenei y; SFA, sa u a ed a y acid; PUFA, polyunsa u a ed a y
acid; MUFA, monounsa u a ed a y acid.
S. May-Wilson e al. / Eu opean Jou nal o Cance 84 (2017) 228e238232

model. Associa ions be ween AA, LA and OA and CRC
isk emained signi ican (Table 3).
We assessed he impac o possible classical pleio-
opism on MR es ima es using bo h IVW and MR-
Egge eg ession es s. The e was no e idence o
iola ion o he s anda d IV assump ions used o MR
analysis, such as a dependence on con ounde s
(Table 4).
In he p esen analysis, we used he SNP s102275 in
combina ion wi h o he SNPs o gene a e a polygenic
isk sco e o SA, OA and POA, whe eas s174547,
which is in LD wi h s102275 (
2
Z1.0 and D0Z1.0),
was used o DPA, AA, DGLA and LA. Bo h SNPs
anno a e he FADS2 gene. FADS2 is a a e-limi ing
enzyme in he desa u a ion o LA o AA, and a-lino-
lenic acid in o DHA and EPA (Fig. 2). These FAs a e
p ecu so s o p os aglandins and leuko ienes, which
a e key media o s o he in lamma o y esponse. In an
eQTL analysis s174547 and s102275 geno ype we e
shown o be s ongly co ela ed wi h FADS2 exp es-
sion ac oss a ange o di e en issue ypes, including
blood (PZ3.98 10
29
), no mal colon
(PZ1.65 10
10
)andCRC(PZ2.07 10
5
)
(Supplemen a y Table 1).
Fig. 1. Me a-analysis odds a ios (OR) o colo ec al cance pe uni inc ease in gene ic isk sco e (s anda d de ia ion o ai ) o sig-
ni ican a y acid associa ions. (a) Oleic acid; (b) a achidonic acid; (c) s ea ic acid; (d) linoleic acid; (e) palmi oleic acid; I
2
: p opo ion o
he o al a ia ion due o he e ogenei y. Boxes: OR poin es ima e; i s a ea is p opo ional o he weigh o he s udy. Diamond: o e all
summa y es ima e, wi h con idence in e als gi en by i s wid h. Ve ical line: null alue (OR Z1.0).
S. May-Wilson e al. / Eu opean Jou nal o Cance 84 (2017) 228e238 233
4. Discussion
While die a y a in ake has been associa ed wi h he
CRC isk, easing ou speci ic FA associa ions and hei
mechanis ic basis has p o en o be challenging. A
numbe o obse a ional s udies ha e epo ed associa-
ions be ween se um le els o speci ic FAs wi h CRC
[28,29], suppo ing ou indings.
A majo s eng h o he MR s a egy o iden i y
causal associa ions is ha i is no in luenced by ecall
bias and con ounding ha can a ec adi ional obse -
a ional s udies. Ne e heless, a key assump ion in MR
is ha he a ian s used o gene a e gene ic sco es a e
associa ed wi h he exposu e being que ied. He ein, we
only made use o SNPs associa ed wi h each FA a
genome-wide signi icance om hypo hesis- ee GWAS.
Fu he mo e, we only used da a om indi iduals o
Eu opean descen so as o limi bias om popula ion
s a i ica ion. Ano he cen al assump ion in MR is ha
a ian s a e associa ed wi h CRC only h ough he
exposu e and a e no con ounded by pleio opy, which
would be e ealed by a posi i e co ela ion be ween
inc easing e ec sizes in he IVs and CRC isk. While we
did no obse e such ela ionship, we acknowledge ha
IVs o a numbe o he FAs we e solely based on only
one o wo SNPs, p e en ing assessmen by IVW and
MR-Egge analysis. One s a egy o o e come his and
ully in es iga e any pleio opy would be o measu e FA
se um le els in co ela ion wi h CRC isk.
In his analysis, he same SNP ( s102275, o co e-
la ed SNP s174547) was used o make causal de-
duc ions be ween mul iple FAs and CRC isk.
The e o e, SNPs ha e been used each ime assuming
ha he exposu e indi idually accoun s o he disease
associa ion. The gene ic a ian associa ion wi h CRC
isk is consequen ly double-coun ed, in ha he e ec is
a ibu ed o di e en FA exposu es [30]. Wi h such
e ical pleio opism, single locus MR analyses canno
obus ly deciphe which FA is p ima ily d i ing he
ela ionship wi h CRC isk. Such conside a ions ha e
no been add essed in p e ious s udies o he ela ion-
ship be ween PUFAs and p os a e cance [31] o be-
ween b anched-chain amino acids and diabe es [32].
While we did no demons a e a causal associa ion
be ween o he FAs including se e al PUFAs, SFAs and
CRC isk, we acknowledge ha ou powe o demon-
s a e a ela ionship was limi ed. Fo example, wi h
espec o EPA: assuming he a iance explained by he
alleles is 0.04%, based on epidemiological obse a ional
s udy da a, and a ela i e isk o 1.04 we had <10%
powe o demons a e a ela ionship [33].
Accep ing hese ca ea s we ha e p o ided suppo o
di e ing e ec s o OA, and u-6 PUFAs LA and AA on
CRC isk. Ou indings b oadly acco d wi h he indings
om many o he published ecological and epidemio-
logical obse a ional s udies. No ably, inc eased le els
o AA con ibu e as a isk ac o o CRC de elopmen
[34,35], while inc eased in ake o oli e oil, which is high
in OA, is associa ed wi h dec eased isk [36]. A numbe
o epidemiological s udies ha e p o ided e idence ha a
Medi e anean die , wi h a highe oli e oil in ake, is
associa ed wi h educed CRC isk [36e38].
In he eQTL analysis, bo h s102275 and s174547
show e idence o cis- egula o y e ec s on FADS2
exp ession. In iguingly, s174547 has p e iously been
epo ed o ha e opposing e ec s on FADS2 and
FADS1 exp ession in CRC [39]. Collec i ely, hese da a
p o ide o ela ionship be ween die , geno ype, FA
me abolism and CRC isk h ough modula ion o an
in lamma o y esponse.
E en so, a biological basis o associa ions be ween
speci ic FAs and CRC isk emain o be es ablished. I is
howe e , p edic ed a p io i ha wi hin any FA class,
di e en membe s ha e di e en ac ions and e ec s. Wi h
Table 4
IVW and MR-Egge es esul s o combined a y acid ins umen al a iables.
Fa y acid
sub ype
Fa y acid IVW MR-Egge
Slope Es ima e (95% CI) P- alue Es ima e (95% CI) P- alue
SFA S ea ic acid (SA) 0.1 (0.33 o 0.64) 0.30 In e cep 0.68 (4.79 o 3.43) 0.28
Slope 4.10 (19.86 o 28.06) 0.27
u-3 PUFA Docosapen aenoic acid (DPA) 0.46 (2.32 o 3.23) 0.55 In e cep 0.09 (0.56 o 0.39) 0.26
Slope 2.01 (7.9 o 11.61) 0.23
Eicosapen aenoic acid (EPA) 0.59 (7.99 o 9.16) 0.54 In e cep 0.11 (N/A) e
Slope 2.2 (N/A) e
u-6 PUFA A achidonic acid (AA) 0.04 (0.2 o 0.33) 0.29 In e cep 0.04 (N/A) e
Slope 0.02 (N/A) e
Dihomo-g-linolenic
acid (DGLA)
0.09 (2.48 o 2.29) 0.70 In e cep 0.25 (N/A) e
Slope 0.90 (N/A) e
Linoleic acid (LA) 0.05 (0.17 o 0.07) 0.22 In e cep 0.02 (0.64 o 0.67) 0.77
Slope 0.07 (0.81 o 0.68) 0.46
MUFA Palmi oleic acid (POA) 1.03 (2.64 o 0.58) 0.15 In e cep 0.11 (0.27 o 0.05) 0.12
Slope 3.13 (3.16 o 9.41) 0.21
CI, con idence in e al; MUFA, monounsa u a ed a y acid; PUFA, polyunsa u a ed a y acid; SFA, sa u a ed a y acid; IVW, in e se a ian
weigh ed. *FA ai s wi h wo IVs, p e en ing calcula ion o CIs and P- alue.
S. May-Wilson e al. / Eu opean Jou nal o Cance 84 (2017) 228e238234
espec o u-6, e idence suppo s he in lamma o y e ec s
o AA h ough COX-2 p oduc ion o in lamma o y me-
dia o s [40] including p os aglandin E2, which a ec CRC
ca cinogenesis [41e43]. This implies ha die s high in AA,
such as mea o eggs, may lead o mo e in lamma o y
compounds, which in u n may inc ease CRC isk. While
inc easing die a y LA, an essen ial FA, migh po en ially
en ich issues wi h AA due o hei me abolic link [44],a
geneeen i onmen in e ac ion may exis o in luence
colon FA con en [45]. The e is howe e , con adic o y
e idence om s udies ha ha e associa ed LA wi h bo h
an inc eased [46] and dec eased isk o CRC, possibly by
al e ing u-6 o u-3 FA a ios [47] o al e na i ely p o-
duc ion o eac i e oxygen species [48]. The abili y o
aspi in o i e e sibly inhibi COX-1 and COX-2 and
he e o e lowe p o-in lamma o y signals independen o
geno ype and die , has hus p o ed an a ac i e op ion o
CRC chemop e en ion [49].
Fig. 2. Pa hway o a y acids. Shown a e he a ious a y acids analysed, and he enzymes in ol ed in hei me abolism. COX: cyclo-
oxygenase, LOX: 5-lipoxygenase.
S. May-Wilson e al. / Eu opean Jou nal o Cance 84 (2017) 228e238 235
In conclusion, i espec i e o he biological basis o
associa ions be ween FAs and CRC isk ou indings a e
consis en wi h he obse a ion ha he die a y
composi ion o MUFAs in Medi e anean die s a e isk
educing, and ha a p o-in lamma o y die a e isk
inc easing [50]. While we may no be a a s age whe e we
can jus i iably ad ise indi iduals o al e hei in ake o
speci ic FAs o dec ease he isk o de eloping CRC, i
seems he cu en guidelines o mode a e o al a and
SFA consump ion and inc ease unsa u a ed FA in ake
is likely o be bene icial.
Con lic o in e es s a emen
None decla ed.
Acknowledgemen s
A he Ins i u e o Cance Resea ch, his wo k was
suppo ed by Cance Resea ch UK (C1298/A8362 -
Bobby Moo e Fund o Cance Resea ch UK). Addi-
ional suppo was p o ided by he Na ional Cance
Resea ch Ne wo k. S. M-W was in eceip o a PhD
s uden ship om The Ins i u e o Cance Resea ch. A.S.
is suppo ed by a clinical ellowship om Cance
Resea ch UK. In Edinbu gh he wo k was suppo ed by
P og amme G an unding om Cance Resea ch UK
(C348/A12076). In Ox o d addi ional unding was p o-
ided by he Ox o d Comp ehensi e Biomedical
Resea ch Cen e and he EU FP7 CHIBCHA g an .
Co e in as uc u e suppo o he Wellcome T us
Cen e o Human Gene ics, Ox o d was p o ided by
g an (090532/Z/09/Z). We a e g a e ul o many col-
leagues wi hin UK Clinical Gene ics Depa men s ( o
CORGI) and o many collabo a o s who pa icipa ed in
he VICTOR and QUASAR2 ials. We also hank
colleagues om he UK Na ional Cance Resea ch
Ne wo k ( o NSCCG). Suppo om he Eu opean
Union (FP7/207-2013, g an 258236) and FP7 collabo-
a i e p ojec SYSCOL and COST Ac ion in he UK is
also acknowledged (BM1206). The COIN and COIN-B
ials we e unded by Cance Resea ch UK and he
Medical Resea ch Council and we e conduc ed wi h he
suppo o he Na ional Ins i u e o Heal h Resea ch
Cance Resea ch Ne wo k. COIN and COIN-B ans-
la ional s udies we e suppo ed by he Bobby Moo e
Fund om Cance Resea ch UK, Teno us, he Kidani
T us , Cance Resea ch Wales and he Na ional Ins i-
u e o Social Ca e and Heal h Resea ch Cance Ge-
ne ics Biomedical Resea ch Uni (2011e2014). N.A.A.,
B.F.M. and S.M.W. we e unded and suppo ed by
KFSHRC. In Finland, his wo k was suppo ed by
g an s om he Academy o Finland (Finnish Cen e o
Excellence P og am 2012e2017, 250345), he Jane and
Aa os E kko Founda ion, he Finnish Cance Socie y
(K.P.), he Eu opean Resea ch Council [ERC; 268648],
he Sig id Juselius Founda ion, SYSCOL, he No dic
In o ma ion o Ac ion eScience Cen e (NIASC), he
No dic Cen e o Excellence inanced by No dFo sk
(p ojec 62721, K.P.) and S a e Resea ch Funding o
Kuopio Uni e si y Hospi al (B1401). We acknowledge
he compu a ional esou ces p o ided by he ELIXIR
node, hos ed a he CSCeIT Cen e o Science,
Finland, and unded by he Academy o Finland (g an s
271642 and 263164), he Minis y o Educa ion and
Cul u e, Finland. V.S. was suppo ed by he Finnish
Academy (g an numbe 139635). Sample collec ion and
geno yping in he Finnish Twin Coho has been sup-
po ed by he Wellcome T us Sange Ins i u e,
ENGAGE eEu opean Ne wo k o Gene ic and
Genomic Epidemiology, FP7-HEALTH-F4-2007
(201413), he Na ional Ins i u e o Alcohol Abuse and
Alcoholism [g an s AA-12502 and AA-00145 o Richa d
J Rose and K02AA018755 o Danielle M Dick] and he
Academy o Finland (100499, 205585, 265240 and
263278 o J.K.). The wo k o he Colon Cance Family
Regis y (CCFR) was suppo ed by om he Na ional
Cance Ins i u e (UM1 CA167551), Na ional Ins i u es
o Heal h and h ough coope a i e ag eemen s wi h he
ollowing CCFR cen e s: Aus alasian Colo ec al Can-
ce Family Regis y (U01 CA074778, U01/U24
CA097735), USC Conso ium Colo ec al Cance Fam-
ily Regis y (U01/U24 CA074799), Mayo Clinic Coop-
e a i e Familial Regis y o Colon Cance S udies
(U01/U24 CA074800), On a io Familial Colo ec al
Cance Regis y (U01/U24 CA074783), Sea le Colo-
ec al Cance Family Regis y (U01/U24 CA074794),
and Uni e si y o Hawaii Colo ec al Cance Family
Regis y (U01/U24 CA074806). The CCFR Illumina
GWAS was suppo ed by unding om he Na ional
Cance Ins i u e, Na ional Ins i u es o Heal h (U01
CA122839 and R01 CA143237 o G.C.). Addi ional
suppo was p o ided om he Su eillance, Epidemi-
ology and End Resul s (SEER) P og am o he Na ional
Cance Ins i u e o F ed Hu chinson Cance Resea ch
Cen e (Con ol Nos. N01-CN-67009, N01-PC-35142
and Con ac No. HHSN2612013000121), he Hawai’i
Depa men o Heal h (Con ol Nos. N01-PC-67001,
N01-PC-35137, and Con ac No.
HHSN26120100037C), and he Cali o nia Depa men
o Public Heal h (con ac HHSN261201000035C)
awa ded o he Uni e si y o Sou he n Cali o nia. The
con en o his manusc ip does no necessa ily e lec
he iews o policies o he Na ional Cance Ins i u e,
any SEER p og am o any o he collabo a ing cen es
in he CCFR, no does men ion o ade names, com-
me cial p oduc s, o o ganisa ions imply endo semen
by he US Go e nmen , SEER o he CCFR.
We a e g a e ul o all indi iduals who pa icipa ed in
he a ious s udies. This s udy made use o geno yping
da a om he 1958 Bi h Coho , kindly made a ailable
by he Wellcome T us Case Con ol Conso ium 2. A
ull lis o he in es iga o s who con ibu ed o he
S. May-Wilson e al. / Eu opean Jou nal o Cance 84 (2017) 228e238236