Tumor necrosis factor-α (TNF-α)-308G/A promoter polymorphism in colorectal cancer in ethnic Kashmiri population - A case control study in a detailed perspective

Abstract

Background: Inflammation constitutes one of the important components of colorectal cancer (CRC) pathogenesis. Tumor necrosis factor-α (TNF-α), a cytokine and an important inflammatory mediator plays a pivotal role in the malignant cellular proliferation, angiogenesis, tissue invasion and metastasis in CRC. The studies on association of various polymorphisms in human TNF-α gene including TNF-α-308G/A single nucleotide polymorphism (SNP) are limited, mixed and inconclusive.

Materials and methods: The aim of this study was to analyze the association of TNF-α-308G/A promoter SNP with colorectal cancer (CRC) susceptibility and development risk and also to evaluate the modifying effects of possible TNF-α-308G/A genotypes on different risk factors of CRC in ethnic population of Kashmir, India through a case-control setup. The genotype frequencies of TNF-α-308G/A promoter SNP were compared between 142 CRC patients and 184 individually matched healthy controls by using polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP) method. The associations between the TNF-α-308G/A SNP and CRC risk were examined through conditional logistic regression models adjusted for multiple possible confounding (third) variables. Further, the associations between this SNP and various clinico-pathological parameters, demographic variables and environmental factors within the case group subjects with regard to CRC risk were also evaluated.

Results: The association between the TNF-α-308G/A SNP and the modulation of risk of CRC was not found to be significant (p value = 0.156). The effect of less common TNF-α-308A allele on the risk of colorectal cancer was also not found to be significant (p value = 0.175). The variant genotype (AA) was nonexistent in the study population. Further, we found no significant effect modulation of CRC risk by wild and heterozygous TNF-α-308G/A SNP genotypes in presence of different possible risk factors (p > 0.05). We also found no significant association of TNF-α-308G/A SNP with the subsets of various characteristics of the case group subjects under study (p > 0.05).

Conclusions: This study indicates that there is no significant association between the TNF-α-308G/A promoter SNP and the risk of developing CRC in ethnic Kashmiri population. However, in order to substantiate our findings, this study needs to be replicated with bigger sample size and should involve other ethnically defined populations with high CRC risk.

Keywords: Case control study; Colorectal cancer (CRC); Kashmir; Polymorphism; Single nucleotide polymorphism (SNP); Tumor necrosis factor-α (TNF-α).

Fig. 1

Electrophoresis of TNF-α-308G/A SNP PCR products on a 2.5% agarose gel. Lanes S1–S16: amplified PCR products with prominent/desired band 195 bp in size. Lane L: 100 bp molecular size marker/ladder.

Fig. 2

Electrophoresis of TNF-α-308G/A SNP genotyping by PCR-restriction fragment length polymorphism on a 4% agarose gel. Lanes S1–S11: restriction digestion products; wild genotype (GG) is cleaved by NcoI enzyme yielding two fragments of size 173 bp and 22 bp while as variant genotype (AA) yields a single undigested fragment of 195 bp. Heterozygous genotype (GA) yields three fragments 195 bp, 173 bp and 22 bp in size. The 22 bp fragment is not visible in the picture. Lanes S2, S4 and S6 show the heterozygous genotype (GA) while as rest of the lanes show wild genotype (GG) of TNF-α-308G/A SNP. Variant genotype (AA) of TNF-α-308G/A SNP was not observed in any of the samples studied. Lane L: 100 bp molecular size marker/ladder.