Emerging evidence suggests that down-regulated miRNAs play an important role in the carcinogenesis of colorectal cancer (CRC). Single nucleotide polymorphisms (SNPs) in the promoter region of miRNAs may disturb miRNAs processing, alter their expression, and ultimately affect an individual's susceptibility to CRC. We conducted a case-control study and analyzed twelve SNPs in the promoter region of miR-143/145 of 525 subjects including 242 cases with CRC and 283 controls using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assay. The mutant genotypes or alleles of rs41291957, rs353292, rs353293, and rs4705341 were significantly associated with an increased risk of CRC compared with the wild genotypes or alleles, while rs4705343, rs17796757, rs3733845, and rs3733846 were significantly associated with a decreased risk of CRC. When stratification analysis was done by different variables, such as tumor size, tumor site, differentiated status, clinical stage, and metastasis status, we found that patients with the mutant allele of rs41291957 had an increased risk to develop a tumor size larger than 5 cm. These findings suggest that SNPs in the promoter region of miR-143/145 may be related to the etiology of CRC. However, further larger studies with different ethnic origins are needed to confirm our results due to limited sample sizes in the study.
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