Abstract 1047: A role for the free beta subunit of human chorionic gonadotropin in sensitivity of epithelial ovarian cancer cells to platinum-based chemotherapeutics

Abstract

Abstract Introduction: The beta-subunit of human chorionic gonadotropin (hCG-β) is elevated in the serum of women with a range of malignant cancers, including epithelial ovarian cancer (EOC). Elevated levels of hCG-β have also been associated with poor response to radiotherapy and chemotherapy in a number of cancers. Women with EOC frequently respond to first line treatment with the platinum based chemotherapeutic drug cisplatin, but relapse with tumors developing chemoresistance. This study aimed to characterise the levels of hCG-β in EOC cell lines and to determine whether hCG-β has a role in the responsiveness of these cell lines to treatment with cisplatin. Methods: qRT-PCR and ELISA were used to determine endogenous levels of hCG-β in seven EOC cell lines: A2780, A2780cis (cisplatin resistant), HEY, SKOV-3, OVCAR-3, PEO-1 and OV202. hCG-β was down-regulated using siRNA in HEY and A2780cis cells. Sensitivity to cisplatin and taxol in these cells was measured using a clonogenic assay. Liquid chromatography-mass spectrometry using isobaric tags for relative and absolute quantitation (iTRAQ) was used to determine the mechanism(s) by which hCGβ may be involved in the sensitivity of EOC cells to cisplatin. Specifically, protein was harvested from A2780cis cells with and without hCGβ downregulation plus or minus treatment with cisplatin at IC50 levels (2μg/ml) for 24h. Protein extracts were then iTRAQ-labeled and global protein changes determined. Results: All cell lines expressed hCG-β transcript and protein. SKOV-3 and HEY cells secreted the highest levels, 14 ng/ml and 3 ng/ml, respectively. OV202, PEO-1, CaOV-3, A2780 and A2780cis cells expressed levels between 0.14-1.4 ng/ml. Down-regulation of hCG-β in HEY and A2780cis increased their sensitivity to cisplatin with the IC50 decreased up to 75% in knockdown compared to control cells. No change in sensitivity was observed with taxol treatment. Down-regulation of hCG-β also increased the sensitivity of these cells to the platinum drugs carboplatin and oxaliplatin. iTRAQ results showed differences in proteins associated with the cell cycle, death and survival pathways, as well as DNA replication, damage and repair. Candidate proteins are currently being validated by western blotting. Conclusions: These findings suggest that hCG-β may be involved in modulating the sensitivity of some EOCs to platinum based chemotherapy. Suppression of hCG-β may be a strategy to increase the responsiveness of primary EOCs to platinum-based chemotherapeutics. Citation Format: Snega M. Sinnappan, Robert C. Baxter, Deborah J. Marsh. A role for the free beta subunit of human chorionic gonadotropin in sensitivity of epithelial ovarian cancer cells to platinum-based chemotherapeutics. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1047. doi:10.1158/1538-7445.AM2015-1047