miR-29c-3p inhibits autophagy and cisplatin resistance in ovarian cancer by regulating FOXP1/ATG14 pathway

Autophagy, characterized by the elevator of autophagy-related gene 14 (ATG14) and the dysregulation of autophagy-related proteins, contributes to the cisplatin (DDP) resistance in ovarian cancer. Forkhead box protein P1 (FOXP1), which is a well-defined transcription factor, is reported to have the oncogenic effect on ovarian cancer. This study aims to identify the effect of miR-29c-3p/FOXP1/ATG14 pathway in regulating autophagy and DDP resistance in ovarian cancer. The expressions of miR-29c-3p, FOXP1, ATG14 and autophagy-related proteins were detected in DDP-sensitive ovarian cancer cell lines (SKOV3 and A2780) and DDP-resistant cell lines (SKOV3/DDP and A2780/DDP). Cell viability was detected using the MTT assay. The therapeutic effect of miR-29c-3p overexpression was observed in the xenograft model of nude mice.Compared with DDP-sensitive cells, miR-29c-3p was decreased in DDP-resistant cells, and an enhancement of FOXP1, ATG14, autophagy, and drug resistance was shown in DDP-resistant cells. The anti-resistant effect of miR-29c-3p was observed as overexpressing miR-29c-3p inhibited cell viability of DDP-resistant cells. Moreover, FOXP1 was a target of miR-29c-3p, which was confirmed by the luciferase reporter assay, and ATG14 was transactivated by FOXP1, which was confirmed by the ChIP assay. Overexpression of miR-29c-3p increased DDP sensitivity by downregulating FOXP1/ATG14 in vitro. The tumor volume was reduced after the injection of miR-29c-3p-overexpressing SKOV3/DDP cells in vivo. Overexpression of miR-29c-3p inhibited autophagy and DDP resistance partly via downregulating FOXP1/ATG14 pathway, suggesting miR-29c-3p as a novel target in overcoming DDP resistance in ovarian cancer.

自噬（autophagy）以自噬相关基因14（autophagy-related gene 14, ATG14）表达上调及自噬相关蛋白调控异常为特征，其参与卵巢癌对顺铂（cisplatin, DDP）的耐药进程。叉头框蛋白P1（Forkhead box protein P1, FOXP1）是一类已被充分界定的转录因子，据报道其在卵巢癌中发挥致癌作用。本研究旨在明确miR-29c-3p/FOXP1/ATG14通路在调控卵巢癌自噬及顺铂耐药中的作用。本研究检测了顺铂敏感卵巢癌细胞系（SKOV3与A2780）及顺铂耐药细胞系（SKOV3/DDP与A2780/DDP）中miR-29c-3p、FOXP1、ATG14及自噬相关蛋白的表达水平；采用MTT法检测细胞活力；并在裸鼠异种移植模型中观察过表达miR-29c-3p的治疗效果。与顺铂敏感细胞相比，顺铂耐药细胞中miR-29c-3p表达水平降低，而FOXP1、ATG14的表达、自噬活性及耐药性均显著增强。过表达miR-29c-3p可抑制顺铂耐药细胞的活力，由此证实其抗耐药效应。此外，经荧光素酶报告基因实验（luciferase reporter assay）验证，FOXP1是miR-29c-3p的靶基因；而染色质免疫沉淀（chromatin immunoprecipitation, ChIP）实验证实，ATG14可被FOXP1反式激活。体外实验表明，过表达miR-29c-3p通过下调FOXP1/ATG14通路，增强卵巢癌细胞对顺铂的敏感性。体内实验中，注射过表达miR-29c-3p的SKOV3/DDP细胞后，裸鼠的肿瘤体积显著减小。综上，过表达miR-29c-3p可通过下调FOXP1/ATG14通路抑制自噬与顺铂耐药，提示miR-29c-3p可作为克服卵巢癌顺铂耐药的新型治疗靶点。