Genetic analysis and allele-specific expression of SMAD7 3'UTR variants in human colorectal cancer reveal a novel somatic variant exhibiting allelic imbalance.

BACKGROUND:Considering the impact of SMAD7 deregulation in colorectal cancer (CRC) progression and the significance of single nucleotide variant (SNV)-mediated disruptions of microRNA (miRNA)-dependent regulation for cancer susceptibility, our study aimed to analyze genetic variation in the SMAD7 3' untranslated region ( 3'UTR) in CRC, measure differences in allelic mRNA expression, and evaluate its interference with miRNA-mediated post-transcriptional regulation. PATIENTS AND METHODS:This study included 80 patients with different CRC stages and six human colon cancer cell lines of various histological origins. SMAD7 3'UTR was analyzed by direct sequencing, followed by the relative quantification of differential allelic expression of detected variants by allele-specific qRT-PCR. In silico tools were employed for predictions of regulatory consequences of detected variants. RESULTS:A total of four different SNVs in one cell line and nine patients were found, among which were a novel somatic point variant and three already known germline variants (rs16950113, rs1050799536, and rs1043778717). All evaluated SNVs exhibited variable extents of allelic imbalance in expression. In silico analysis predicted significant effects of SNVs on miRNA binding efficiency, with each SNV disrupting existing and creating new target sites for one or more miRNAs. CONCLUSION:Imbalance observed in the expression of SNV alleles altering miRNA binding suggests that all investigated SNVs are potential contributing factors impacting SMAD7 expression regulation in CRC that further studies should investigate.