MiR-509-3p Induces Apoptosis and Affects the Chemosensitivity of Cervical Cancer Cells by Targeting the RAC1/PAK1/LIMK1/Cofilin Pathway.

Chemoresistance is one of the main factors of treatment failure of cervical cancer (CC). Here, we intended to discover the role and mechanism of miR-509-5p in the paclitaxel chemoresistance of CC cells. RT-PCR was conducted to verify miR-509-3p expression. HCC94 and C-33A paclitaxel-resistant CC cell models were constructed. Additionally, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and flow cytometry were performed to verify the viability and apoptosis of HCC94 and C-33A cells after upregulating miR-509-3p. Besides, the downstream target of miR-509-3p was analyzed by bioinformatics, and the targeted relationship between miR-509-3p and RAC1 was identified by the dual-luciferase reporter assay and RNA immunoprecipitation (RIP) assay. Further, the expression of apoptotic proteins (Bcl2, Bax, and Caspase3) and the RAC1/PAK1/LIMK1/Cofilin pathway was monitored by Western blot. The result showed that upregulating miR-509-3p markedly inhibited the viability and promoted the apoptosis of CC cells. On the other hand, miR-509-3p was distinctly downregulated in paclitaxel-resistant HCC94 and C-33A cells (vs. normal cells). The transfection of miR-509-3p mimics notably increased their sensitivity to paclitaxel. Meanwhile, RAC1 was found as the potential target of miR-509-3p in bioinformatics analysis. Moreover, the RAC1/p21 (RAC1) activated kinase 1 (PAK1)/LIM kinase 1 (LIMK1)/Cofilin pathway was significantly activated in paclitaxel-resistant HCC94 and C-33A cells, while miR-509-3p overexpression significantly inactivated this pathway. Additionally, downregulation of RAC1 also partly reversed the paclitaxel-resistance of CC cells and inhibited PAK1/LIMK1/Cofilin. All in all, miR-509-3p enhances the apoptosis and chemosensitivity of CC cells by regulating the RAC1/PAK1/LIMK1/Cofilin pathway.