MicroRNA 375 regulates proliferation and migration of colon cancer cells by suppressing the CTGF-EGFR signaling pathway.

MicroRNA 375 (MIR375) is significantly down regulated in human colorectal cancer (CRC) tissues; we have previously identified MIR375 as a colon cancer associated microRNA (miRNA). We identified putative MIR375 target genes by comparing the mRNA microarray analysis data of MIR375-overexpressing cells with the candidate MIR375 target genes predicted by public bioinformatic tools. We investigated that the connective tissue growth factor (CTGF) is a direct target gene of MIR375. Expression of CTGF, a ligand of epidermal growth factor receptor (EGFR), was markedly enhanced in human CRC tissues in comparison with the corresponding normal colon tissues. We demonstrated that the expression levels of molecules in EGFR signaling pathways were regulated by MIR375 in colorectal cells. Using immunohistochemistry and the xenograft of MIR375-overexpressing colorectal cells in mice, we showed that MIR375 regulates cell growth and proliferation, angiogenesis, cell migration, cell cycle arrest, apoptosis, and necrosis in colon cells. Furthermore, results of MIR375 overexpression and cetuximab treatment indicated that the apoptosis and necrosis in colon cells were synergistically enhanced. Our results suggest that the down-regulation of MIR375 modulates EGFR signaling pathways in human colorectal cells and tissues by increasing CTGF expression; therefore, MIR375 may have a therapeutic value in relation to human CRC.