The association of SMAD7 polymorphisms with colorectal cancer susceptibility and clinicopathological features in the Iranian population

Genome-wide association studies (GWAS) have identified 18q21 as a risk locus for colorectal cancer (CRC), which maps to the SMAD7 gene. Our aim was to investigate the association between two single nucleotide polymorphisms (SNPs) of SMAD7 and the risk of CRC in the Iranian individuals.

This case–control study was conducted on 109 CRC cases and 109 controls in the Iranian population to evaluate the influence of two SNPs of SMAD7, rs2337106 and rs6507874, on the risk of CRC as well as on clinicopathological features. Genotype determination was performed by TaqMan assay via an ABI 7500 Real Time PCR System (Applied Biosystems) for DNA of peripheral blood. Descriptive analysis and logistic regression model were used for statistical analyses.

Genotyping of the SNPs in the SMAD7 gene showed that the frequency of G allele of rs2337106 was 53.7% in controls and 56.4% in cases (p-value=0.564) and the frequency of C allele of rs6507874 was 55.5% in controls and 56.3% in cases (p-value=0.772). Besides, there were no significant differences in genotype frequencies of these SNPs between CRC patients and controls. The SMAD7 genotypes were also not associated with the risk of CRC as well as with any clinicopathological characteristics such as tumor site, tumor grade and stage TNM in CRC patients (p-value>0.05), even after adjustment for sex, age and smoking status.

Our results provided the first evidence that SMAD7 genotypes, rs2337106 and rs6507874, could not be predisposing markers in genetic susceptibility to CRC in an Iranian population, at least in the studied population.