miRNA-483-3p overexpression unleashes invasive growth of metastatic colorectal cancer via NDRG1 downregulation and ensuing activation of the ERBB3/AKT axis

Colorectal cancer is a prevalent disease that is the third most common cause of cancer-associated death globally. The genetic mechanisms underlying tumor aggressiveness in colorectal cancer require further elucidation. Taking advantage of a large panel of human metastatic colorectal cancer xenografts and matched stem-like cell cultures (m-colospheres), we show here that overexpression of miRNA-483-3p, encoded by a frequently amplified gene locus encompassing IGF2, confers an aggressive phenotype. Following ectopic overexpression of miRNA-483-3p, m-colospheres displayed (i) increased proliferative response to exogenous EGFR family ligands EGF and neuregulin 1; (ii) increased spontaneous and growth factor-induced invasiveness and epithelial-mesenchymal transition (EMT); and (iii) enhanced stem-cell frequency and resistance to differentiation. Transcriptomic analyses and functional validation found that miRNA-483-3p directly targets NDRG1, a known metastasis suppressor responsible for downregulation of the EGFR family. As a result, induced or endogenous miRNA-483-3p overexpression associated with stimulation of the signaling pathway triggered by ERBB3, including AKT and GSK3ß, which is responsible for EMT transcription factor activation. Consistently, treatment of miRNA-483-3p-overexpressing m-colospheres with selective ERBB3 antibodies counteracted their proliferative and invasive phenotype. The pro-malignant role of miRNA-483-3p was further corroborated by analysis of human colorectal tumors, where miRNA-483-3p expression levels directly correlated with expression of EMT transcription factors and poor prognosis, and downregulation of miRNA-483-3p, which prevented invasion of tumors formed by m-colosphere transplantation. These results unveil a previously unrecognized link between miRNA-483-3p, NDRG1, and ERBB3-AKT signaling, which can directly support colorectal cancer invasion and is amenable to therapeutic targeting. Overall design: Gene expression profiling analysis (RNA-seq) of colospheres CRC264 and CRC327, each compared with its derivative transduced with miR-483-3p (CRC364miR and CRC327miR, respectively).