Abstract 3436: MiR-194 modulates paclitaxel resistance in ovarian cancer cells through the regulation of MDM-2 expression
Authors: Nakamura Koji , Sawada Kenjiro , Yoshimura Akihiko , Nakatsuka Erica , Kinose Yasuto , Mabuchi Seiji , Kimura Tadashi 
Published: July 2017

Purpose: Ovarian cancer is the most lethal gynecologic malignancy. Platinum-paclitaxel combination chemotherapy is the current standard postoperative care for patients with advanced ovarian cancer. Despite developments in current chemotherapy regimens in the last decades, overall 5-year survival rate for patients with advanced disease remains approximately 30%, mainly due to primary or acquired drug resistance. Therefore, overcoming chemoresistance remains the great challenge in ovarian cancer management. However, mechanisms underlying chemoresistance to paclitaxel have not been fully understood. The aim of this study is to identify key miRNAs which regulate paclitaxel resistance in ovarian cancer and to pursue those potential as therapeutic targets.

Methods: Using two serous ovarian cancer cell lines, SKVO3ip1 and HeyA8, paclitaxel resistant ovarian cancer cell lines were established by a continuous exposure of paclitaxel. MiRNA PCR arrays were performed and miR-194 was found to be one of down-regulated miRNAs in paclitaxel-resistant cell lines. The effect of miR-194 on paclitaxel resistance was assessed by transducing the precursor miRNA into ovarian cancer cells. In silico analysis revealed MDM-2 is one possible putative target of miR-194 and it was assessed using luciferase reporter assay. Since MDM-2 is one of key regulator of P53 ubiquitination, the effect of miR-194 on cell cycle in ovarian cancer cell was assessed. To analyze the impact of miR-194 and MDM-2 expression on patient survival, Kaplan-Meier and log-rank methods were used using The Cancer Genome Atlas (TCGA) dataset.

Results: While IC50 values of SKOV3ip1 and HeyA8 were 5.0 nM and 3.5 nM respectively, those of paclitaxel resistant cell lines, named as SKOV3ip1-TR and HeyA8-TR, were both over 300 nM. In both resistant cell lines, miR-194 was found to be down-regulated compared with their parental cell lines. Up-regulation of miR-194 sensitized resistant cells to paclitaxel. Conversely, its downregulation induced paclitaxel resistance in parental cells. Luciferase reporter assay revealed that miR-194 directly suppressed MDM-2 transcriptional activity. In resistant cell lines, MDM-2 was up-regulated compared with their parental cell lines. MiR-194 induced P21 upregulation and G1 phase arrest in resistant cell lines through the downregulation of MDM-2. In TCGA dataset, high MDM-2 expression was associated with shorter progression-free survival of ovarian cancer patients (concrete data, p=0.046).

Conclusion: miR-194 acts as a tumor suppressor miRNA through the sensitization to paclitaxel and can be considered as a therapeutic option to overcome paclitaxel-resistant in ovarian cancer patients.

Citation Format: Koji Nakamura, Kenjiro Sawada, Akihiko Yoshimura, Erica Nakatsuka, Yasuto Kinose, Seiji Mabuchi, Tadashi Kimura. MiR-194 modulates paclitaxel resistance in ovarian cancer cells through the regulation of MDM-2 expression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3436. doi:10.1158/1538-7445.AM2017-3436