Single Nucleotide Polymorphisms in Colorectal Cancer: Associations with Tumor Site and TNM Stage

Abstract

Background & aim. Colon tumor carcinogenesis and rectal tumor carcinogenesis have each been associated with different genetic features, but data are still controversial and are insufficient to support their distinct molecular biology. Recently, genome-wide association studies (GWAS) have also found heterogeneity in colorectal cancer (CRC) risks based on population ethnicity and tumor features. Several single nucleotide polymorphism (SNP) markers are described in the literature as having site and/or stage specificity, including rs10795668, rs3802842, rs6983267, and rs4939827.  Replication of initial findings in different ethnic groups by independent studies is required to unravel the population-specific differences in risk.

Methods. We examined whether inherited risk variants at rs10795668, rs3802842, rs6983267, and rs4939827 exerted a differential effect on colon and rectal cancers in a Romanian hospital based series of 153 CRC cases and 182 non-affected control subjects prospectively recruited between 2007 and 2010.

Results. Rectal tumors were significantly associated with rs4939827 (OR = 4.85, P = 0.002) and rs6983267 (OR = 3.00, P = 0.036), suggesting that carriers of risk alleles at these loci had increased susceptibility to development of rectal cancer rather than colon cancer. Carrying the C allele at rs3802842 appeared to be associated with a lower risk for rectal tumors in our dataset. We found no association between genotypes and tumor aggressiveness as reflected by TNM staging.

Conclusions. The associations between SNPs, and tumor site and staging remain to be further clarified. Our results should be considered cautiously, but may be taken into acount in future, larger epidemiological studies.