Association of common variants on chromosome 8q24 with gastric cancer in Venezuelan patients.

Gastric cancer remains one of the leading causes of death in the world, being Central and South America among the regions showing the highest incidence and mortality rates worldwide. Although several single nucleotide polymorphisms (SNPs) identified in the chromosomal region 8q24 by genome-wide association studies have been related with the risk of different kinds of cancers, their role in the susceptibility of gastric cancer in Latin American populations has not been evaluated yet. Hereby, we performed a case-control study to explore the associations between three SNPs at 8q24 and gastric cancer risk in Venezuelan patients. We analyzed rs1447295, rs4733616 and rs6983267 SNPs in 122 paraffin-embedded tumor samples from archival bank and 129 samples with chronic gastritis (obtained by upper endoscopy during the study) from the Central Hospital of Barquisimeto (Lara, Venezuela). Genotypes were determined by PCR-RFLP reactions designed in this study for efficient genotyping of formalin-fixed/paraffin-embedded tissues. No significant differences in genotype frequencies between case and control groups were found. However, carriers of the homozygous TT genotype of SNP rs4733616 had an increased risk of developing poorly differentiated gastric cancer according to the codominant (OR=3.59, P=0.035) and the recessive models (OR=4.32, P=0.014, best-fitting model of inheritance), adjusted by age and gender. Our study suggests that the SNP rs4733616 is associated with susceptibility to poorly differentiated gastric cancer in Venezuelans. Additional studies are needed to further interrogate the prognostic value of the rs4733616 marker in this high-risk population for gastric cancer.

Distribution of GSTM1, GSTT1, GSTP1 and TP53 disease-associated gene variants in native and urban Venezuelan populations.

The contemporary Venezuelan population is the product of major admixture process across various historical events, which has provided it a particular genetic background. The aim of this study concerns the analysis of glutathione S-transferase (GST) GSTM1, GSTP1 and GSTT1 genetic variants and five polymorphisms at the TP53 gene, which are related to cancer susceptibility, in an urban/admixed population and five Amerindian tribes (Bari, Panare, Pemon, Warao and Wayuu) from Venezuela. Genotyping was carried out in 120 individuals from an urban sample and 188 Amerindians. The analysis performed on TP53 haplotype and GST allele distribution showed a close correlation for Pemon and Warao populations, while Bari group appears isolated from the other populations. GSTT1 null variant frequency in our admixed (11%) and native samples (0.0-11.4%) was lower when compared with Caucasians, Africans and Asians. Frequency of the GSTP1*Val cancer-associated allele found in Bari (88.6%) and Panare (63.0%) is of the highest so far reported. Fourteen TP53 haplotypes were observed in the admixed populations, whereas only 3 to 5 in Amerindians. To our knowledge this is the first report of GST polymorphisms and TP53 haplotype distribution in Venezuelans. The distribution of most of analyzed polymorphisms in the urban sample is consistent with the admixed origin of the present-day population of Venezuela. While, the inter-ethnic variations in genetic polymorphisms found in Native American tribes seem to be the result of the influence of demographic factors. These results provide additional data for undertaking ethnographic and disease association studies in Venezuela.