miR-302a Inhibits Metastasis and Cetuximab Resistance in Colorectal Cancer by Targeting NFIB and CD44

Introduction: Metastasis and drug resistance contribute substantially to the poor prognosis of colorectal cancer (CRC) patients.However, the epigenetic regulatory mechanisms by which CRC develops metastatic and drug-resistant characteristics remain unclear.This study aimed to investigate the role of miR-302a in the metastasis and molecular-targeted drug resistance of CRC and elucidate the underlying molecular mechanisms.Methods: miR-302a expression in CRC cell lines and patient tissue microarrays was analyzed by qPCR and fluorescence in situ hybridization.The roles of miR-302a in metastasis and cetuximab (CTX) resistance were evaluated both in vitro and in vivo.Bioinformatic prediction algorithms and luciferase reporter assays were performed to identify the miR-302a binding regions in the NFIB and CD44 3'-UTRs.A chromatin immunoprecipitation assay was performed to examine NFIB occupancy in the ITGA6 promoter region.Immunoblotting was performed to identify the EGFR-mediated pathways altered by miR-302a.Results: miR-302a expression was frequently reduced in CRC cells and tissues, especially in CTX-resistant cells and patient-derived xenografts.The decreased miR-302a levels correlated with poor overall CRC patient survival.miR-302a overexpression inhibited metastasis and restored CTX responsiveness in CRC cells, whereas miR-302a silencing exerted the opposite effects.NFIB and CD44 were identified as novel targets of miR-302a.miR-302a inhibited the metastasis-promoting effect of NFIB that physiologically activates ITGA6 transcription.miR-302a restored CTX responsiveness by suppressing CD44-induced cancer stem cell-like properties and EGFR-mediated MAPK and AKT signaling.These results are consistent with clinical observations indicating that miR-302a expression is inversely correlated with the expression of its targets in CRC specimens.Conclusions: Our findings show that miR-302a acts as a multifaceted regulator of CRC metastasis and CTX resistance by targeting NFIB and CD44, respectively.Our study implicates miR-302a as a candidate prognostic predictor and a therapeutic agent in CRC.