Distribution of allelic and genotypic frequencies of IL1A, IL4, NFKB1 and PAR1 variants in Native American, African, European and Brazilian populations
Amador et al. BMC Res Notes
Distribution of allelic and genotypic frequencies of IL1A, IL4, NFKB1 and PAR1 variants in Native American, African, European and Brazilian populations
Marcos A. T. Amador 0 3
Giovanna C. Cavalcante 0 3
Ney P. C. Santos 0 2 3
Leonor Gusmão 1 4
João F. Guerreiro 0 3
Ândrea Ribeiro‑dos‑Santos 0 2 3
Sidney Santos 0 2 3
0 Laboratório de Genética Humana e Médica, Instituto de Ciências Biológicas, Universidade Federal do Pará , Cidade Universitária Prof. José da Silveira Netto, Rua Augusto Corrêa, 01 - Guamá, Belém, PA CEP: 66.075‐110 , Brazil
1 Laboratório de Diagnóstico por DNA, Universidade Federal do Rio de Janeiro , Rio de Janeiro , Brazil
2 Núcleo de Pesquisas em Oncologia, Universidade Federal do Pará , Belém , Brazil
3 Laboratório de Genética Humana e Médica, Instituto de Ciências Biológicas, Universidade Federal do Pará , Cidade Universitária Prof. José da Silveira Netto, Rua Augusto Corrêa, 01 - Guamá, Belém, PA CEP: 66.075‐110 , Brazil
4 Instituto de Patologia e Imunologia Molecular , Universi‐ dade do Porto, Porto , Portugal
Background: The inflammatory response plays a key role at different stages of cancer development. Allelic variants of the interleukin 1A (IL1A), interleukin 4 (IL4), nuclear factor kappa B1 (NFKB1) and protease‑ activated receptor 1 (PAR1) genes may influence not only the inflammatory response but also susceptibility to cancer development. Among major ethnic or continental groups, these polymorphic variants present different allelic frequencies. In admixed populations, such as the Brazilian population, data on distribution of these polymorphisms are limited. Here, we collected samples of cancer‑ free individuals from the north, northeast, midwest, south and southeast regions of Brazil and from the three main groups that gave rise to the Brazilian population: Native Americans from the Brazilian Amazon, Africans and Europeans. We describe the allelic distributions of four IL1A (rs3783553), IL4 (rs79071878), NFKB1 (rs28362491) and PAR1 (rs11267092) gene polymorphisms, which the literature describes as polymorphisms with a risk of cancer or worse prognosis for cancer. Results: The genotypic distribution of the four polymorphisms was statistically distinct between Native Americans, Africans and Europeans. For the allelic frequency of these polymorphisms, the Native American population was the most distinct among the three parental populations, and it included the greatest number of alleles with a risk of cancer or worse prognosis for cancer. The PAR1 gene polymorphism allelic distribution was similar among all Brazilian regions. For the other three markers, the northern region population was statistically distinct from other Brazilian region populations. Conclusion: The IL1A, IL4, NFKB1 and PAR1 gene polymorphism allelic distributions are homogeneous among the regional Brazilian populations, except for the northern region, which significantly differs from the other four Brazilian regions. Among the parental populations, the Native American population exhibited a higher incidence of alleles with risk of cancer or worse prognosis for cancer, which can indicate greater susceptibility to this disease. These genetic data may be useful for future studies on the association between these polymorphisms and cancer in the investigated populations.
Polymorphisms; Cancer; Inflammatory response; Brazil; Native Americans; IL1A gene; IL4 gene; NFKB1 gene and PAR1 gene
External factors that modify tissue homeostasis, such as
microorganism infection, tissue injury and exposure to
contaminants may induce inflammatory processes [
Chronic inflammation is associated with the appearance
of malignant cells and these cells’ proliferation, invasion
and metastasis processes [
The inflammatory response may be modulated through
gene expression variations due to structural genetic
polymorphisms or regulatory regions. Therefore, an
individual genetic composition may influence not only the
inflammatory response but also susceptibility to cancer
Recently, many studies have tested the association
between different forms of cancer and functional variants
of genes responsible for the inflammatory process [
such as interleukin 1A (IL1A), interleukin 4 (IL4), nuclear
factor kappa B1 (NFKB1) and protease-activated receptor
1 (PAR1) [
The gene for the pro-inflammatory cytokine IL1A
presents an insertion/deletion (INDEL) polymorphism
(3′UTR indel TTCA, rs3783553) in a binding site for
the microRNAs miR-122 and miR-378 that modifies the
connection between these microRNAs. The insertion
(Ins) allele is related to higher gene expression [
Different investigations have demonstrated that individuals
homozygous for the insertion (Ins/Ins) are less
susceptible to developing gastric cancer, nasopharyngeal cancer,
hepatocellular carcinoma and cervical cancer [
Interleukin-4 (IL4), which is an anti-inflammatory
cytokine gene, presents a VNTR polymorphism (intron 3
VNTR—70 bp, rs79071878) located on the third intron.
Different alleles for this polymorphism modulate gene
expression. The allele with two repeats (A2) is related to
higher gene expression, while the allele with three repeats
(A3) is related to lower expression [
homozygous genotype for higher IL4 expression (A2/A2) is
associated with a worse prognosis in bladder cancer patients
and with oral and pharyngeal cancers [
Transcription factor NFKB1 plays an important role
in the inflammatory process, and it can influence
cancer development and aggressiveness, increasing tumour
angiogenesis and repressing the immune response [
The NFKB1 gene carries an INDEL polymorphism in
the promoter region (−94 indel ATTG, rs28362491) that
exerts a regulatory effect on gene expression. The
insertion allele is associated with an increase in promoter
activity and protein synthesis [
Several studies on the association between rs28362491
and the risk of developing cancer show conflicting results
]. In a recent meta-analysis of 21 case–control
studies, Yang et al.  showed that the insertion allele
for this polymorphism is significantly associated with a
risk of developing oral, prostate and ovary cancers. The
analyses also reveal similar results in Asian populations,
but not in European populations, which suggests ethnic
variations in predisposition to different types of cancer.
The receptor PAR1 is a member of the
superfamily of G protein-coupled membrane receptors [
These receptors regulate processes ranging from
vascular integrity to systemic inflammation. Activation of
the PAR1 receptor in epithelial cells, macrophages and
endothelial cells promotes the release of
pro-inflammatory mediators, such as TNF, IL1β, IL2, IL6, CXCL8 and
]. The PAR1 gene features an INDEL
polymorphism (−506 indel—13 bp, rs11267092) located in the
promoter region [
]. The deletion allele (Del) is related
to a better prognosis in breast, stomach and oesophagus
The polymorphisms described above exhibit common
features. (1) They are functional polymorphisms that
alter the expression of genes that participate in and for
metabolic pathways associated with carcinogenesis. (2)
Such genes are associated with different types of cancer
with high incidence in the Brazilian population,
especially prostate, stomach, oesophagus, breast and cervical
]. (3) The genes vary in populations with
different ethnic and geographic origins [
]. (4) Information
on allele distributions in Native Americans and admixed
populations, such as the Brazilian population, is limited.
(5) From a technical perspective, all of the investigated
polymorphisms are small INDELs; therefore, genotyping
may be performed using a single PCR step followed by
capillary electrophoresis, which is an accessible and
lowcost laboratory technique.
The Brazilian population is one of the most
heterogeneous populations worldwide that is formed by an
admixture of Native Americans, Europeans and Africans.
This heterogeneity has been well-documented in several
genetic investigations [
]. The admixture process
occurred through different means between the
Brazilian geographic regions. Therefore, the Native American
contribution is more pronounced in Northern Brazil;
the African contribution is more elevated in Northeast
Brazil; and the South features a European predominance
with little Native American and African influence .
We must know the distribution of allelic
frequencies of these polymorphisms [IL-1A (rs3783553),
IL4 (rs79071878), NFKB1 (rs28362491) and PAR1
(rs11267092)] for association studies on cancer, data for
which is limited on Brazilian populations. Thus, the aim
of this study is to characterize allelic distributions in a
representative sample of the Brazilian population from all
geographic regions of the country.
The allele and genotype frequencies of the investigated
polymorphisms (rs3783553, rs79071878, rs28362491
and rs11267092) in samples from the five Brazilian
geographic regions and in the parental populations are
presented in Table 1. The genotypic distributions of the
markers exhibited a Hardy–Weinberg equilibrium in
the investigated populations, except for the NFKB1 gene
marker in the European sample (p = 0.003).
When we compared allelic distributions in parental
populations, all markers exhibited a significantly
different allele frequency between the three groups, and the
Native American populations exhibited more differences
from the continental populations (Table 2). Among the
four markers, the average frequency difference (value δ)
between the Native Americans and Africans was 34 %;
between the Native Americans and Europeans was 37 %;
and between the Europeans and Africans was 20 %.
When we considered each marker individually, a higher
average frequency difference was observed between the
continents for IL1A (40 %) followed by IL4 (34 %), PAR1
(30 %) and NFKB1 (17 %).
For the geographic region comparisons (Table 2),
rs11267092 (PAR1 gene) showed no significant difference
between the Brazilian regions. The distributions of the
other three polymorphisms (rs3783553, rs79071878 and
rs28362491) were statistically similar between the
northeast, south and southeast regions.
The analyses showed statistically significant
differences in the rs3783553, rs79071878 and rs28362491
polymorphism distributions between the northern
population and the populations in the other regions, except
the rs3783553 polymorphism in the midwest region
(p = 0.543). This polymorphism exhibited a significantly
different distribution in the midwest population
compared with the northeast, south and southeast regions.
All polymorphisms investigated here have been
previously described as associated with a predisposition to
some form of cancer [
14, 15, 21, 24, 25
], as well as
compared with the prognosis of the disease [
proposed a different approach to analysing the
population data. Under this new approach, the proportion of
individuals who are allele carriers are considered at risk
for cancer or worse prognosis for cancer (referred to as
potentially deleterious alleles ), including the deletion
allele for rs3783553, allele A2 for rs79071878, the
insertion allele for rs28362491, and the insertion allele for
Based on this analysis, the proportion of potentially
deleterious alleles is higher in the Native American
population (50 %) than the African (44 %) and European
(35 %) populations. Among Brazilians, the proportion of
potentially deleterious alleles is 40 %. Likewise, the
proportion of individuals who are carriers of six or more
alleles associated with cancer is greater among the Native
Americans (8.6 %) than the Africans (5.2 %) and
Europeans (1.9 %), and the proportion of Brazilians (4.2 %) is
intermediate among the ancestral population values. The
proportion of carriers is not evenly distributed between
the geographic regions. The proportion is smaller in the
Northeast Brazil population (2.7 %), intermediate in
Midwest and South Brazil populations (mean = 3.4 %) and
more elevated in the North (5.0 %) and Southeast Brazil
populations (6.5 %).
This is the most comprehensive study on the rs3783553,
rs79071878, rs28362491 and rs11267092 polymorphism
variations in Brazil and among its ancestral populations.
This is also the first study to describe the variability of
these markers in Native American populations.
We evaluated the distribution of allele and genotype
frequencies for these four markers among the pairs of
ancestral and Brazilian populations using the Chi-square
test with the due statistical corrections (false discovery
rate) to avoid spurious correlations. This test is adequate
to compare two or more populations for a qualitative
]. Furthermore, our sample size is
representative of the populations studied here (928 Brazilians, 222
Native Americans, 211 Africans and 268 Europeans) and
adequate for using INDEL-type polymorphisms, which
present a low mutation rate compared with other types of
The data from the ancestral populations investigated
here reveal considerable heterogeneity between
continental populations. All investigated markers present
δ values greater than 30 %, except for the NFKB1 gene
polymorphism. In this set of markers, the Native
American populations were the most differentiated among the
investigated continental populations.
Given the differences in the observed allelic
distribution between the parental populations, we tested the
hypothesis that these differences were due to
population sampling. Therefore, we used data published in the
1000 Genomes project (Table 3). We verified that the
cited frequency for the IL1A, NFKB1 and PAR1
markers (the three markers for which data were available)
in the African and European populations are similar
to the frequency observed herein. Thus, we discard the
hypothesis and assume that our samples are
representative of the European, African and Native American
Despite the frequency differences between the parental
populations and the intense and heterogeneous process
of admixture that formed the current Brazilian
population, the allelic distribution is relatively homogeneous
throughout most of the country. In general, only the
northern population exhibits an allele distribution that
significantly differs from the other geographic regions for
three of the four investigated markers.
We understand that these differences may be explained
by a greater contribution of Native Americans to the
northern populations. Previous estimates using different
types of genetic markers show that the greatest Native
American genetic contribution among Brazilians occurs
in North populations [
36, 38, 39, 43
]. Moreover, data
generated in the present work show that Native Americans
form the most differentiated group of all the continental
populations that form the Brazilian population.
Therefore, we believe that, conjunctively, these two factors may
explain the observed differentiation in the Northern
Our analyses involving potentially deleterious alleles
demonstrate that the Native American population
presents a higher proportion (50 %) of these alleles
compared with the other parental populations (44 and 35 %
for African and European, respectively). This analysis
holds when considering the proportion of carriers with
six or more (among eight possible) potentially deleterious
However, we cannot evaluate how this genetic
composition may be associated with a higher incidence of
cancer in this population because Native American
populations form traditional communities that reside in
outlying areas of urban centres. Epidemiological data are
not available on the incidence of different types of cancer
among these populations.
Despite the absence of epidemiological data, recent
studies demonstrate that different forms of cancer are
associated with a higher (or lower) contribution from
Native American ancestry in admixed populations from
South America. The investigations were associated with
acute lymphoblastic leukaemia [
], breast cancer [
and gastric cancer [
In summary, our study shows that the allelic
distribution of the IL-1A (rs3783553), IL4 (rs79071878), NFKB1
(rs28362491) and PAR1 (rs11267092) gene
polymorphisms differs between European, African and Native
American populations. Further, the same heterogeneity
is not observed between regional populations in Brazil,
except for the northern region, which significantly differs
from the other four Brazilian regions.
Moreover, the results show that the Native American
population includes a greater proportion of carriers with
six or more alleles associated with cancer, which suggests
that this population may have a higher risk of developing
(or worse prognosis for) diseases associated with these
alleles. The presented genetic data may be useful for
future studies on the association between these
polymorphisms and cancer in these populations.
The study population consists of 928 non-related and
cancer-free adult individuals, recruited in ten
Brazilian Federal Units, between the years of 2009 and 2010.
In the present work, 180 individuals (90 male and 90
female) residing in the states of Pará (60), Amazonas
(60) and Rondônia (60) represented the North region;
187 individuals (107 male and 80 female) residing in the
states of Ceará (135) and Pernambuco (52) represented
the Northeast region; 186 individuals (95 male and 91
female) residing in the states of Goiás (101), Mato Grosso
do Sul (49) and Distrito Federal (36) represented the
Midwest region; 184 individuals (90 male and 94 female)
residing in the state of São Paulo represented the
Southeast region; and 191 individuals (96 male and 95 female)
residing in the state of Rio Grande do Sul represented the
tions were measured by Chi-square test (χ2 test, df = 2)
in BioEstat software [
]. FDR (False Discovery Rate)
method was used to correct multiple analyses [
MATA carried out the molecular genetic studies, undertook the bibliographic
review, analyzed the data and wrote the paper. GCC revised the manuscript
and participated of the techniques development. ARS, JFG, LG and NPCS
contributed to the discussion. SS coordinated the study and also contributed
to the discussion. All authors read and approved the final version of the
This study was supported by Conselho Nacional de Desenvolvimento
Científico e Tecnológico (CNPq), Pró‑Reitoria de Pesquisa de Pós‑ Graduação
da Universidade Federal do Pará (PROPESP/UFPA) and Fundação de Amparo e
Desenvolvimento da Pesquisa (FADESP).
The authors declare that they have no competing interests.
1. Rasch S , Algül H. A clinical perspective on the role of chronic inflammation in gastrointestinal cancer . Clin Exp Gastroenterol . 2014 ; 7 : 261 - 72 .
2. Sun B , Karin M. The therapeutic value of targeting inflammation in gastrointestinal cancers . Trends Pharmacol Sci . 2014 ; 35 : 349 - 57 .
3. Gu X , Shen Y , Fu L , Zuo H , Yasen H , He P , Guo H , Shi Y , Yusufu M. Polymorphic variation of inflammation‑related genes and risk of non‑Hodgkin lymphoma for Uygur and Han Chinese in Xinjiang . Asian Pac J Cancer Prev . 2014 ; 15 : 9177 - 83 .
4. Wang Q , Zhang C , Walayat S , Chen HW , Wang Y . Association between cytokine gene polymorphisms and cervical cancer in a Chinese population . Eur J Obstet Gynecol Reprod Biol . 2011 ; 158 : 330 - 3 .
5. Lu Z‑H , Gu X ‑ J, Shi K‑Z , Li X , Chen D ‑D , Chen L. Association between genetic polymorphisms of inflammatory response genes and the risk of ovarian cancer . J Formos Med Assoc . 2016 ; 115 : 31 - 7
6. Mandal RK , Agrawal T , Mittal RD . Genetic variants of chemokine CCL2 and chemokine receptor CCR2 genes and risk of prostate cancer . Tumor Biol . 2014 ; 36 : 375 - 81 .
7. Wang Z , Liu Q‑L , Sun W , Yang C‑ J , Tang L , Zhang X , Zhong X ‑M. Genetic polymorphisms in inflammatory response genes and their associations with breast cancer risk . Croat Med J. 2014 ; 55 : 638 - 46 .
8. Zhang Y , Mao Y , Sun Y. Genetic polymorphisms of IL‑6 and IL ‑10 genes correlate with lung cancer in never‑smoking Han population in China . Int J Clin Exp Med . 2015 ; 8 : 1051 - 8 .
9. Gao J , Xu H‑L , Gao S , Zhang W , Tan Y ‑ T , Rothman N , Purdue M , Gao Y‑ T , Zheng W , Shu X‑ O , Xiang Y ‑B. Genetic polymorphism of NFKB1 and NFK ‑ BIA genes and liver cancer risk: a nested case‑ control study in Shanghai, China . BMJ Open . 2014 ; 4 : e004427 .
10. Yu Y , Zheng S , Zhang S , Jin W , Liu H , Jin M , Chen Z , Ding Z , Wang L , Chen K. Polymorphisms of inflammation‑related genes and colorectal cancer risk: a population‑based case ‑ control study in China . Int J Immunogenet . 2014 ; 41 : 289 - 97 .
11. Kopp TI , Andersen V , Tjonneland A , Vogel U. Polymorphisms in NFKB1 and TLR4 and interaction with dietary and life style factors in relation to colorectal cancer in a Danish prospective case‑ cohort study . PLoS One . 2015 ; 10 : e0116394 .
12. De Martino M , Haitel A , Schatzl G , Klatte T. The protease activated receptor 1 gene variation IVSn ‑14 A > T is associated with distant metastasis and cancer specific survival in renal cell carcinoma . J Urol . 2013 ; 190 : 1392 - 7 .
13. Gao Y , He Y , Ding J , Wu K , Hu B , Liu Y , Wu Y , Guo B , Shen Y , Landi D , Landi S , Zhou Y , Liu H . An insertion/deletion polymorphism at miRNA‑122‑binding site in the interleukin‑1α 3′ untranslated region confers risk for hepatocellular carcinoma . Carcinogenesis . 2009 ; 30 : 2064 - 9 .
14. Zeng X‑F , Li J , Li S ‑B. A functional polymorphism in IL ‑1A gene is associated with a reduced risk of gastric cancer . Tumour Biol . 2014 ; 35 : 265 - 8 .
15. Yang ZH , Dai Q , Zhong L , Zhang X , Guo QX , Li SN . Association of IL‑1 polymorphisms and IL‑1 serum levels with susceptibility to nasopharyngeal carcinoma . Mol Carcinog . 2011 ; 50 : 208 - 14 .
16. Pu Y , Zhang Z , Zhou B , Chen P , Zhang K , Song Y , Gao Q , Wang K , Quan Y , Xi M , Zhang L. Association of an insertion/deletion polymorphism in IL1A 3′‑UTR with risk for cervical carcinoma in Chinese Han Women . Hum Immunol . 2014 ; 75 : 740 - 4 .
17. Kesarwani P , Ahirwar D , Singh R , Manchanda PK , Mittal RD . Do IL‑4 intron 3 VNTR and IL‑6 (‑174) G/C variants reflect ethnic variation? A comparative study between the global and North Indian populations . Asian Pac J Cancer Prev . 2008 ; 9 : 76 - 80 .
18. Nakashima H , Miyake K , Inouoe Y , Shimizu S , Akahoshi M , Tunaka Y , Otsuka T , Harada M. Association between IL‑4 genotype and IL ‑4 production in the Japanese population . Genes Immun . 2002 ; 3 : 107 - 9 .
19. Ahirwar D , Kesarwani P , Manchanda PK , Mandhani A , Mittal RD . Anti‑ and proinflammatory cytokine gene polymorphism and genetic predisposition: association with smoking, tumor stage and grade, and bacillus Calmette‑ Guérin immunotherapy in bladder cancer . Cancer Genet Cytogenet . 2008 ; 184 : 1 - 8 .
20. Yang CM , Chen HC , Hou YY , Lee MC , Liou HH , Huang SJ , Yen LM , Eng DM , Hsieh YD , Ger LP. A high IL‑4 production diplotype is associated with an increased risk but better prognosis of oral and pharyngeal carcinomas . Arch Oral Biol . 2014 ; 59 : 35 - 46 .
21. Yang X , Li P , Tao J , Qin C , Cao Q , Gu J , Deng X , Wang J , Liu X , Wang Z , Wu B , Gu M , Lu Q , Yin C . Association between NFKB1 ‑94ins/del ATTG promoter polymorphism and cancer susceptibility: an updated meta‑analysis . Int J Genomics . 2014 ; 2014 : 1 - 9 .
22. Li P , Gu J , Yang X , Cai H , Tao J , Yang X , Lu Q , Wang Z , Yin C , Gu M. Functional promoter 9‑4 ins/del ATTG polymorphism in NFKB1 gene is associated with bladder cancer risk in a Chinese population . PLoS One . 2013 ; 8 : 1 - 7 .
23. Duan W , Wang E , Zhang F , Wang T , You X , Qiao B . Association between the NFKB1‑94 ins/del ATTG polymorphism and cancer risk: an updated meta‑analysis . Cancer Invest . 2014 ; 32 : 311 - 20 .
24. Umar M , Upadhyay R , Kumar S , Ghoshal UC , Mittal B . Association of common polymorphisms in TNFA, NFkB1 and NFKBIA with risk and prognosis of esophageal squamous cell carcinoma . PLoS One . 2013 ; 8 : 1 - 12 .
25. Xu L , Huang S , Chen W , Song Z , Cai S. NFKB1 ‑94 insertion/deletion polymorphism and cancer risk: a meta‑analysis . Tumor Biol . 2014 ; 35 : 5181 - 7 .
26. Fujimoto D , Hirono Y , Goi T , Katayama K , Matsukawa S , Yamaguchi A . The activation of proteinase‑activated receptor ‑1 (PAR1) promotes gastric cancer cell alteration of cellular morphology related to cell motility and invasion . Int J Oncol . 2013 ; 42 : 565 - 73 .
27. Mercer PF , Williams AE , Scotton CJ , José RJ , Sulikowski M , Moffatt JD , Murray LA , Chambers RC . Proteinase‑activated receptor ‑1, CCL2, and CCL7 regulate acute neutrophilic lung inflammation . Am J Respir. Cell Mol Biol . 2014 ; 50 : 144 - 57 .
28. Arnaud E , Nicaud V , Poirier O , Rendu F , Alhenc‑ Gelas M , Fiessinger J‑N , Emmerich J , Aiach M. Protective effect of a thrombin receptor (proteaseactivated receptor 1) gene polymorphism toward venous thromboembolism . Arterioscler Thromb Vasc Biol . 2000 ; 20 : 585 - 92 .
29. Lurje G , Husain H , Power DG , Yang D , Groshen S , Pohl A , Zhang W , Ning Y , Manegold PC , El‑Khoueiry A , et al. Genetic variations in angiogenesis pathway genes associated with clinical outcome in localized gastric adenocarcinoma . Ann Oncol . 2010 ; 21 : 78 - 86 .
30. Lurje G , Leers JM , Pohl A , Oezcelik A , Zhang W , Ayazi S , Winder T , Ning Y , Yang D , Klipfel NE , et al. Genetic variations in angiogenesis pathway genes predict tumor recurrence in localized adenocarcinoma of the esophagus . Ann Surg . 2010 ; 251 : 857 - 64 .
31. Eroğlu A , Karabıyık A , Akar N. The association of protease activated receptor 1 gene-506 I/D polymorphism with disease‑free survival in breast cancer patients . Ann Surg Oncol . 2012 ; 19 : 1365 - 9 .
32. Ferlay J , Soerjomataram I , Ervik M , Dikshit R , Eser S , Mathers C , Rebelo M , Parkin DM , Forman D , Bray F. GLOBOCAN 2012 v1. 0, Cancer incidence and mortality worldwide: IARC CancerBase No . 11 [internet]. International Agency for Research on Cancer, Lyon , France. 2013 . http://globocan.iarc. fr. Accessed on 6 Jan 2016 .
33. The 1000 Genomes Project Consortium. An integrated map of genetic variation from 1092 human genomes . Nature . 2012 ; 491 : 56 - 65 .
34. Cardena MMSG , Ribeiro‑ dos ‑Santos AKC , Santos SEB , Mansura AJ , Bernardez‑Pereira S , Santos PCJL , Pereira AC , Fridman C . Mitochondrial and genomic ancestry are associated with etiology of heart failure in Brazilian patients . J Hum Hypertens . 2015 ; 5 : 1 .
35. Leite FPN , Callegari‑ Jacques SM , Carvalho BA , Kommers T , Matte CHF , Raimann PE , Schwengber SP , Sortica VA , Tsuneto LT , Petzl‑Erler ML , Salzano FM , Hutz MH . Y‑STR analysis in Brazilian and South Amerindian populations . Am J Hum Biol . 2008 ; 20 : 359 - 63 .
36. Manta FSN , Pereira R , Vianna R , De Araújo ARB , Gitaí DLG , Da Silva DA , Gusmão L. Revisiting the genetic ancestry of Brazilians using autosomal AIM‑indels . PLoS One . 2013 ; 8 : 1 - 11 .
37. Palha T , Gusmão L , Ribeiro‑Rodrigues E , Guerreiro JF , Ribeiro ‑ dos ‑Santos Â , Santos S. Disclosing the genetic structure of Brazil through analysis of male lineages with highly discriminating haplotypes . PLoS One . 2012 ; 7 : 1 - 8 .
38. Pena SDJ , di Pietro G , Fuchshuber‑Moraes M , Genro JP , Hutz MH , Kehdy FDSG , Kohlrausch F , Magno LAV , Montenegro RC , Moraes MO , de Moraes MEA , de Moraes MR , Ojopi ÉB , Perini JA , Racciopi C , Ribeiro‑ dos ‑Santos ÂKC , Rios‑Santos F , Romano ‑Silva MA , Sortica VA , Suarez‑Kurtz G. The genomic ancestry of individuals from different geographical regions of Brazil is more uniform than expected . PLoS One 2011 ; 6 ( 2 ): e17063
39. Santos NPC , Ribeiro‑Rodrigues EM , Ribeiro ‑ dos ‑Santos AKC , Pereira R , Gusmão L , Amorim A , Guerreiro JF , Zago MA , Matte C , Hutz MH , Santos SEB . Assessing individual interethnic admixture and population substructure using a 48‑Insertion‑Deletion (INSEL) Ancestry‑Informative Marker (AIM) Panel . Hum Mutat. 2010 ; 31 : 184 - 90 .
40. Cavalcante GC , Freitas NSC , Ribeiro‑ dosSantos AM , Carvalho DC , Silva EM , Assumpção PP , Ribeiro‑ dos ‑Santos AKC , Santos SEB , Santos NPC . Investigation of potentially deleterious alleles for response to cancer treatment with 5‑Fluorouracil . Anticancer Res . 2015 ; 35 ( 12 ): 6971 - 7 .
41. Callegari‑ Jacques SM . Bioestatística: princípios e aplicações . Porto Alegre: Artmed; 2003
42. Freitas NSC , Resque RL , Ribeiro‑Rodrigues EM , Guerreiro JF , Santos NPC , Ribeiro‑ dos ‑Santos AKC , Santos SEB . X ‑linked insertion/deletion polymorphisms: forensic applications of a 33‑markers panel . Int J Legal Med . 2010 ; 124 : 589 - 93 .
43. Pena SDJ , Pimenta JR , Bydlowski SP . DNA tests probe the genomic ancestry of Brazilians DNA tests probe the genomic ancestry of Brazilians . Braz J Med Biol Res . 2009 ; 42 : 870 - 6 .
44. Carvalho DC , Wanderley AV , Amador MAT , Fernandes MR , Cavalcante GC , Pantoja KB , Mello FA , de Assumpção PP , Khayat AS , Ribeiro‑ dosSantos Â , Santos S , dos Santos NP. Amerindian genetic ancestry and INDEL polymorphisms associated with susceptibility of childhood B‑ cell Leukemia in an admixed population from the Brazilian Amazon . Leuk Res . 2015 ; 39 : 1239 - 45 .
45. Vieira PC , Burbano RM , Fernandes DC , Montenegro RC , dos Santos SE , Sortica VA , Assumpção PP , Ribeiro‑ dos ‑Santos ÂK , Carvalho AA , Santos NP . Population stratification effect on cancer susceptibility in an admixed population from Brazilian Amazon . Anticancer Res . 2015 ; 35 ( 4 ): 2009 - 14 .
46. Pereira L , Zamudio R , Soares‑Souza G , et al. Socioeconomic and nutritional factors account for the association of gastric cancer with Amerindian ancestry in a Latin American admixed population . PLoS One . 2012 ; 7 : e41200 .
47. Zamudio R , Pereira L , Rocha CD , Berg DE , et al. Population, epidemiological, and functional genetics of gastric cancer candidate genes in peruvians with predominant amerindian ancestry . Dig Dis Sci . 2016 ; 61 : 107 - 16 .
48. Ribeiro‑Rodrigues EM , Palha TJBF , Bittencourt EA , Ribeiro ‑ dos ‑Santos AKC , Santos S. Extensive survey of 12 X‑STRs reveals genetic heterogeneity among Brazilian populations . Int J Legal Med . 2011 ; 125 : 445 - 52 .
49. Santos SEB , Ribeiro‑Rodrigues EM , Ribeiro ‑ dos ‑Santos AKC , Hutz MH , Tovo‑Rodrigues L , Salzano FM , Callegari‑ Jacques SM . Autosomal STR analyses in native Amazonian tribes suggest a population structure driven by isolation by distance . Hum Biol . 2009 ; 81 : 71 - 88 .
50. Silva WA , Bortolini MC , Schneider MP , Marrero A , Elion J , Krishnamoorthy R , Zago MA. MtDNA haplogroup analysis of black Brazilian and subSaharan populations: implications for the Atlantic slave trade . Hum Biol . 2006 ; 78 : 29 - 41 .
51. Excoffier L , Lischer HEL . Arlequin suite version 3 . 5: a new series of programs to perform population genetics analyses under Linux and Windows . Mol Ecol Resour . 2010 ; 10 : 564 - 7 .
52. Ayres M , Ayres JRM , Ayres DL , Santos AS . BioEstat version 5 .0. Sociedade Civil Mamirauá , MCT-CNPq , Belém, Pará, Brasil, 2007 .
53. Benjamini Y , Hochberg Y. Controlling the false discovery rate: a practical and powerful approach to multiple testing . J R Stat Soc B . 1995 ; 57 : 289 - 300 .