Abstract
Colorectal cancer (CRC) is a heterogeneous disease and classified into various subtypes, among which transcriptional alterations result in CRC progression, metastasis, and drug resistance. Forkhead-box M1 (FOXM1) is a proliferation-associated transcription factor which is overexpressed in CRC and the mechanisms of FOXM1 regulation have been under investigation. Previously, we showed that FOXM1 binds to promoters of certain microRNAs. Database mining led to several microRNAs that might interact with FOXM1 3'UTR. The interactions between shortlisted microRNAs and FOXM1 3'UTR were quantitated by a dual-luciferase reporter assay. MicroRNA-532-3p interacted with the 3'UTR of the FOXM1 mRNA transcript most efficiently. MicroRNA-532-3p was ectopically overexpressed in colorectal cancer (CRC) cell lines, leading to reduced transcript and protein levels of FOXM1 and cyclin B1, a direct transcriptional target of FOXM1. Further, a clonogenic assay was conducted in overexpressed miR-532-3p CRC cells that revealed a decline in the ability of cells to form colonies and a reduction in migratory and invading potential. These alterations were reinforced at molecular levels by the altered transcript and protein levels of the conventional EMT markers E-cadherin and vimentin. Overall, this study identifies the regulation of FOXM1 by microRNA-532-3p via its interaction with FOXM1 3'UTR, resulting in the suppression of proliferation, migration, and invasion, suggesting its role as a tumor suppressor in CRC.