MiR-92b-3p Regulates Cell Cycle And Apoptosis By Targeting CDKN1C,and Affects The Multidrug Resistance Of Human Colorectal Cancer

Colorectal cancer(CRC)is the third most common malignant tumor in the world and the second leading cause of cancer death,with only 13% five-year survival rate after tumor spread.Chemotherapy is the standard regimen for patients with this disease,but drug resistance,especially multidrug resistance(MDR),has become a major obstacle in the clinical treatment of CRC,with nearly 90% of patients developing some degree of MDR during treatment,which prevents clinical treatment from achieving the desired effects,thus causing tumor recurrence and metastasis and eventual death from cancer.However,the clear molecular mechanism of MDR is complex,and other potential mechanisms and biomarkers remain to be identified.Studies have shown that micro RNAs(miRNAs)are involved in a variety of biological processes and play an important role in tumor proliferation,migration,invasion,angiogenesis,and drug resistance in the form of oncogenes or tumor suppressor genes.To search for miRNA targets that may be involved in the CRC MDR phenotype,this study used transcriptomic and small RNAomic screens to analyze and evaluate the expression profiles of miRNAs in CRC HCT8 cell line and its chemoresistant counterpart HCT8/T cell line.It was found that miR-92b-3p was highly expressed in HCT8/T cells and might play an important role in CRC MDR.From the present study,it was found that miR-92b-3p level was significantly elevated in MDR HCT8/T and HCT8/V cells and could be up-regulated by PTX induction.Furthermore,miR-92b-3p overexpression could maintain cell viability in the chemotherapy setting and promote cell migration and resistance to chemotherapeutics,whereas miR-92b-3p knockdown attenuated the resistance of MDR HCT8/T cells to multiple chemotherapeutic drugs in vitro and sensitized tumors to PTX and NVB in vivo.Double luciferase reporter gene analysis and Western blotting analysis showed that miR-92b-3p directly targeted and inhibited the expression of CDKN1 C,which encodes p57Kip2 protein.CDKN1 C silencing reduced the sensitivity of HCT8 cells to chemotherapeutics,while CDKN1 C overexpression significantly reversed the MDR in HCT8/T cells.In addition,co-silencing of miR-92b-3p and CDKN1 C reversed the sensitizing effect of miR-92b-3p silencing on HCT8/T cells.The results of this study suggested that miR-92b-3p regulated drug sensitivity of CRC cells by targeting CDKN1 C,whereas knockdown of miR-92b-3p up-regulated CDKN1 C expression,significantly reversed drug resistance in vivo and in vitro.Further investigation of the intrinsic biological mechanism,CDKN1 C encoded protein p57Kip2 could induce cell cycle G1 arrest and exerted a pro-apoptotic effect in the chemotherapy environment,enhanced chemotherapeutic drug-induced cell apoptosis,thereby regulating the sensitivity of CRC cells to chemotherapy drugs.Overall,chemotherapeutic drugs could stimulate colorectal cancer cells to up-regulate miR-92b-3p expression and confer cellular resistance to chemotherapeutic drugs.miR-92b-3p regulated cell cycle and apoptosis pathways by targeting CDKN1 C,thus reducing cell sensitivity to chemotherapeutic drugs.To the best of our knowledge,this study revealed a new mechanism of MDR in CRC,identified miR-92b-3p as a key regulator of CRC drug sensitivity,elucidated the direct relationship between miR-92b-3p/CDKN1 C and chemoresistance,suggested that miR-92b-3p-mediated molecular mechanisms might play an important role in the development of MDR,indicated that miR-92b-3p could be used as a potential therapeutic target for reducing MDR in chemotherapy and as a candidate biomarker for predicting the efficacy of chemotherapy.