113P - Dicer contributes to chemoresistance in colorectal cancer via regulating a set of miRNAs and their downstream mRNAs

Abstract

BackgroundChemotherapy has a good success rate in colorectal cancer (CRC); however, recurrence of CRC is still frequent due to acquired drug resistance. Dicer, one of the key enzymes of the microRNA (miRNA) biogenesis pathway, may be involved in chemoresistance through regulating the expression of miRNAs. Until now, the role of Dicer in regulating chemoresistance is still unclear. MethodsOxaliplatin- or 5’FU-resistant cell lines were established to investigate the molecular mechanism of chemoresistance. Western blot was performed to detect the expression of Dicer; next-generation sequencing (NGS) and cDNA array were performed to identify the alternative expression of miRNAs and mRNAs; and RT-qPCR or TaqMan PCR was used to validate the expression of potential miRNAs or mRNAs. Functional characterization of drug-resistant cells was performed by cell proliferation, colony formation, sphere formation, migration and invasive assays. ResultsFrom the TCGA database, the expression level of Dicer mRNA is increased in colorectal cancer; the level of Dicer protein is increased in oxaliplatin- or 5’FU-resistant cell lines. The drug resistant cells possess increased abilities in cell migration, invasion and sphere formation. Knocked-down expression of Dicer can enhance the drug sensitivity in drug resistant cells; in contrast, overexpression of Dicer increases drug resistance in parental drug sensitive cells. By next-generation sequencing and cDNA array, we found that the expression of a set of miRNAs and their downstream mRNAs is changed in oxaliplatin resistant cells. Dicer overexpression enhances the expression of those miRNAs and mRNAs in drug sensitive parental cells. Clinical evaluation further confirmed the increased expression of those miRNAs in the plasma of CRC patients is positively correlated with a poor response to oxaliplatin. In addition, NF-kB and Wnt pathways were found to be activated in drug resistant cells. ConclusionsOur results suggest that those miRNAs may act as biomarkers to predict oxaliplatin response in colorectal cancer by detecting their plasma miRNAs. The molecular mechanism of those miRNAs in regulating the drug response is currently under our investigation. Legal entity responsible for the studyThe author. FundingMinistry of Science and Technology. DisclosureThe author has declared no conflicts of interest.