Résumé
Abstract Lung cancer is a major cause of cancer-related death worldwide. This study investigated the regulatory effects of the microRNA-99a-5p (miR-99a-5)/VLDLR axis on lung cancer cell sensitivity to chemotherapy and its mechanism. miR-99a-5p and VLDLR expression levels were quantified using RT-qPCR and western blotting, respectively. The IC50 value of cisplatin (DDP) was determined using a CCK-8 assay. Lung cancer cell proliferation and apoptosis were measured using the CCK-8 assay and flow cytometry, respectively. The mRNA expression levels of apoptosis-related factors (Bax, Bcl-2, and Caspase-3) were evaluated using RT-qPCR. The direct relationship between miR-99a-5p and VLDLR was validated using dual-luciferase reporter gene and RIP assays. miR-99a-5p was weakly expressed in DDP-resistant lung cancer cells. Overexpression of miR-99a-5p promoted DDP sensitivity, suppressed proliferation and colony formation, and promoted apoptosis of A549/DDP cells in vitro. Mechanistically, miR-99a-5p restrained VLDLR expression by binding to VLDLR 3'UTR, and miR-99a-5p mediated inhibition of VLDLR regulated the DDP sensitivity, proliferation, and apoptosis of A549/ DDP cells. Overexpression of miR-99a-5p inhibited the growth of A549 cells and increased chemosensitivity of A549 cells to DDP in vivo. In conclusion, miR-99a-5p overexpression promotes sensitivity to DDP and cell apoptosis by downregulating VLDLR expression in A549/ DDP cells.
Résumé
Very low density lipoprotein receptor (VLDLR) is thought to participate in the patho-genesis of atherosclerosis induced by VLDL and β-VLDL. The present study was undertaken to elu-cidate the effects of VLDL and β-VLDL on VLDLR expression and its signaling pathway. RAW264.7 cells were incubated with VLDL and β-VLDL. The expression of VLDLR mRNA was detected by RT-PCR. The transcriptional activity of VLDLR gene was detected in recombinant plasmid pGL4.2VR-luciferase transfected RAW264.7. Western blot assay was used to detect the changes of phosphorylated ERK1/2 protein. Inhibitors or activators were used to observe the signal pathway in-volving VLDLR expression regulation. The results showed that VLDL and β-VLDL stimulated ERKI/2 activity in a PKC-dependent manner. VLDL or β-VLDL-induced VLDLR expression on macrophages was extremely abolished by inhibitors ERKI/2 or PKC. Our findings revealed that VLDL or β-VLDL-induced VLDLR expression via PKC/ERK cascades and the effect was linked to the transcriptional activation of VLDLR gene promoter.