MALAT1 rs664589 Polymorphism Inhibits Binding to miR-194-5p, Contributing to Colorectal Cancer Risk, Growth, and Metastasis.

Metastasis associated with lung adenocarcinoma transcript-1 (MALAT1) is an evolutionarily highly conserved lncRNA that contributes to colorectal cancer development. However, the exact molecular mechanisms connecting MALAT1 to colorectal cancer have not been fully elucidated. Here, we performed a case-control study in 1,078 patients with colorectal cancer and 1,175 healthy controls to evaluate the association between potentially functional genetic variants of MALAT1 and survival outcomes in patients with colorectal cancer. MALAT1 rs664589 CG/GG genotypes significantly increased the associated risk and decreased overall survival of patients with colorectal cancer compared with the CC genotype. In vitro and in vivo experiments showed that the rs664589 C to G mutation facilitated carcinogenesis and metastasis of colorectal cancer. Mechanistically, the miRNA miR-194-5p targeted MALAT1 for degradation in the nucleus in an Ago2-dependent manner; the rs664589 G allele altered the binding of MALAT1 to miR-194-5p, resulting in increased expression of MALAT1. Colorectal cancer cells and human tissues with the rs664589 CG/GG genotype expressed significantly higher MALAT1 than those with the rs664589 CC genotype. Multivariate Cox regression analysis showed that MALAT1 was a poor prognostic factor of colorectal cancer. In summary, MALAT1 with the rs664589 G allele demonstrates altered binding to miR-194-5p in the nucleus, leading to increased MALAT1 expression and enhanced colorectal cancer development. SIGNIFICANCE: These findings highlight the functional role of MALAT1 polymorphism in colorectal cancer metastasis and survival as well as the underlying mechanism. ©2019 American Association for Cancer Research.