Genetic variant in miR‐21 binding sites is associated with colorectal cancer risk

Single nucleotide polymorphisms (SNPs) within binding sites of microRNAs (miRNAs) could modify cancer susceptibility by changing the binding affinity of miRNAs on their target mRNA 3ʹ‐untranslated regions (UTRs). MicroRNA‐21 (miR‐21) is involved in the development of colorectal cancer. However, the relationship between SNPs within the binding sites of miR‐21 and colorectal cancer risk has not been widely investigated. A case‐control study including 1147 patients and 1203 controls was performed to evaluate the association of SNPs in miR‐21 binding sites and colorectal cancer risk. Dual‐luciferase reporter assays and functional assays were performed to evaluate the effects of miR‐21. The SNP rs6504593 C allele conferred an increased risk of colorectal cancer compared with the T allele in an additive model (odds ratio [OR] = 1.19, 95% confidence interval [CI] = 1.04‐1.36, P = 0.011). Dual‐luciferase reporter assays demonstrated that the rs6504593 T allele negatively post‐transcriptionally regulated IGF2BP1 by altering the binding affinity of miR‐21. Additionally, colorectal cancer cells transiently transfected with miR‐21 mimics promoted cell proliferation and suppressed apoptosis, whereas inhibition of miR‐21 decreased cell growth. These data suggest that the miR‐21 binding site SNP rs6504593 in the IGF2BP1 3ʹ‐UTR may alter IGF2BP1 expression and contribute to colorectal cancer risk.