CPEB4-Promoted Paclitaxel Resistance in Ovarian Cancer In Vitro Relies on Translational Regulation of CSAG2.

Rui Huang,Yaqing Zhang,Xiaomei Ma,Xiaofeng Xie,Hongyun Gan,Fei Zhao,Jin Zhao

doi:10.3389/fphar.2020.600994

Abstract

Background: Drug resistance is a major obstacle in chemotherapy for ovarian cancer, wherein the up regulation of drug-resistant genes plays an important role. The cytoplasmic polyadenylation element binding protein 4 (CPEB4) is an RNA binding protein that controls mRNA cytoplasmic polyadenylation and translation. Methods: The expression of CPEB4 in paclitaxel-resistant ovarian cancer cell lines and recurrent ovarian tumors relative to counterparts was determined by qRT-PCR, Western blotting and immunohistochemistry. The response to paclitaxel treatment was evaluated by cellular viability test and colony formation assay. RNA immunoprecipitation and poly(A) tail test were applied to examine the levels of RNA binding and cytoplasmic polyadenylation. Results: CPEB4 is elevated in paclitaxel-resistant ovarian cancer cells and recurrent ovarian tumors treated with paclitaxel-based chemotherapy. In addition, CPEB4 overexpression promotes paclitaxel resistance in ovarian cancer cells in vitro, and vice versa, CPEB4 knockdown restores paclitaxel sensitivity, indicating that CPEB4 confers paclitaxel resistance in ovarian cancer cells. Mechanistically, CPEB4 binds with the taxol (paclitaxel)-resistance-associated gene-3 (TRAG-3/CSAG2) mRNAs and induces its expression at a translational level. Moreover, CSAG2 expression is upregulated in paclitaxel-resistant ovarian carcinoma and cancer cell lines, and more importantly, siRNA-mediated CSAG2 knockdown overtly attenuates CPEB4-mediated paclitaxel resistance. Conclusion: This study suggests that the drug-resistant protein CSAG2 is translationally induced by CPEB4, which underlies CPEB4-promoted paclitaxel resistance in ovarian cancer in vitro. Thus, interfering CPEB4/CSAG2 axis might be of benefit to overcome paclitaxel-resistant ovarian cancer.

Highlights

Ovarian cancer is the most lethal gynecologic malignancy, and approximate 22,440 new cases and 14,080 deaths have been estimated to occur in the United States in 2017 (Siegel et al, 2017)
We report that cytoplasmic polyadenylation element binding protein 4 (CPEB4) promotes paclitaxel resistance in ovarian cancer, and suggest that this effect depends on its translational regulation of CSAG2
To explore whether CPEB4 plays a role in paclitaxel resistance in ovarian cancer, we compared its transcript levels between naive sensitive SKOV3 (S) cells and their paclitaxel-resistant counterparts SKOV3 (R) through qRT-PCR analysis

Summary

Introduction

Ovarian cancer is the most lethal gynecologic malignancy, and approximate 22,440 new cases and 14,080 deaths have been estimated to occur in the United States in 2017 (Siegel et al, 2017). The standard first-line option for treating ovarian cancer is cytoreductive surgery followed by paclitaxel/platinum-based chemotherapy (Jayson et al, 2014). Up to 80% of patients initially respond well to therapy, most of them develop recurrent ovarian cancer within 12–24 months and succumb to progressive refractory disease resistant to therapy, with a poor 5-years survival rate lower than 30% (Au Yeung et al, 2016). CSAG2, known as the taxol resistance associated gene 3 (TRAG-3), has been identified to be overexpressed in a paclitaxel-resistant ovarian cancer cell line and be a prognostic factor for predicting clinical outcome after paclitaxel-based chemotherapy (Lage and Denkert, 2007; Materna et al, 2007). Drug resistance is a major obstacle in chemotherapy for ovarian cancer, wherein the up regulation of drug-resistant genes plays an important role. The cytoplasmic polyadenylation element binding protein 4 (CPEB4) is an RNA binding protein that controls mRNA cytoplasmic polyadenylation and translation

Methods

Results

Conclusion