Abstract 865: The small heat shock protein αB-crystallin protects versus withaferin A-induced apoptosis and confers a more metastatic phenotype in cisplatin-resistant ovarian cancer cells

Abstract

Abstract A majority of ovarian tumors eventually recur in a drug-resistant form leaving patients few treatment options. The goal of this study was to explore the phenotypic and molecular characteristics of a cisplatin-resistant ovarian cancer cell line (OVCAR8R) as compared to its cisplatin-sensitive syngeneic counterpart (OVCAR8) and to explore the effectiveness of a novel therapeutic, Withaferin A (WA). In addition to unique morphological characteristics and increased expression of vimentin, the small heat shock proteins (Hsps) αB-Crystallin and Hsp27 are constitutively expressed in OVCAR8R cells while OVCAR8 cells do not express these Hsps, supporting that Hsp overexpression may confer resistance to chemotherapy and promote a more aggressive tumor type. WA treatment causes apoptosis in a dose-dependent manner in OVCAR8 cells, while the OVCAR8R cells remain viable at comparable doses of WA. αB-Crystallin was upregulated in a dose dependent manner in the WA-treated OVCAR8R cells. To determine the significance of αB-crystallin expression in conferring a more aggressive phenotype, αB-crystallin was silenced by CRISPR-Cas9 in OVCAR8R cells. Strikingly, the morphology of the OVCAR8R-αB-crystallin-knockout clones revert to the morphology of the cisplatin-sensitive OVCAR8 cell line. Molecular characterization reveals concurrent downregulation of Hsp27, and decreased expression of vimentin supporting that loss of αB-Crystallin is coincident with a less aggressive molecular phenotype. Upon challenge with WA, vimentin is downregulated in the αB-crystallin-null clones and in the cisplatin-sensitive OVCAR8 cells, but not in the OVCAR8R cells. Transient transfection of wildtype αB-Crystallin, but not a chaperone-defective mutant, alters the morphology of the OVCAR8 cells where the αB-Crystallin-knockout clones closely resemble the cisplatin-resistant OVCAR8R cells. Further, transient overexpression of wildtype αB-crystallin, but not a chaperone-defective-mutant, protects cells from WA-induced apoptosis as compared to GFP-transfected cells. Migration assays reveal that OVCAR8R cells have increased migration capability as compared to their cisplatin-sensitive counterparts and silencing of αB-Crystallin decreases migration of cisplatin-resistant cells. This research supports the potential effectiveness of WA as a therapy for ovarian cancer cells that acquire resistance to platinum-based therapies and underscores that αB-crystallin confers a more aggressive cellular phenotype and therefore, may be a promising molecular target for a better clinical outcome. Citation Format: Merideth K. Krevosky, Melissa M. Carmichael. The small heat shock protein αB-crystallin protects versus withaferin A-induced apoptosis and confers a more metastatic phenotype in cisplatin-resistant ovarian cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 865.