Abstract A74: The HIV protease inhibitor nelfinavir, alone or in combination with the proteasome inhibitor bortezomib, is cytotoxic to high-grade serous ovarian cancer cells regardless of platinum sensitivity

Abstract

Abstract High-grade serous ovarian cancer (HGSOC) is a deadly disease, affecting women worldwide. Major challenges in treating HGSOC patients involve overcoming resistance to platinum (Pt)-based therapy by developing novel treatment approaches. Nelfinavir (NFV), an anti-HIV drug, has shown to be effective against cancers of high secretory capacity—e.g., multiple myeloma—by aggravating the stress of the endoplasmic reticulum (ER). Its potential therapeutic role against HGSOC, however, remains unclear. We hypothesized that simultaneous ER stress aggravation by NFV and blockage of the proteolytic capacity of the proteasome with a proteasome inhibitor should cause sufficient ER stress to tilt cells to a death fate. In this study, we investigated the cytotoxicity of the ER aggravator NFV as monotherapy and in combination with the proteasome inhibitor bortezomib (BZ) against HGSOC cells having differential sensitivities to cisplatin (CDDP). NFV caused cell cycle arrest associated with increased expression of cyclin-dependent kinase inhibitor p27kip1, while triggering the unfolded protein response (UPR) in a dose-dependent manner and assessed by increased subrogate ER stress biomarkers GRP78 and CHOP. We also discovered that blocking the ubiquitin proteasome system (UPS) using cytostatic concentrations of BZ causes accumulation of poly-ubiquitinated proteins and further activation of the UPR. More importantly, when we combined BZ with NFV, we observed a potentiation of the action of BZ leading to HGSOC lethality regardless of Pt sensitivity. These results suggest that NFV could potentially be used following standard Pt-based treatment, either as monotherapy or in conjunction with proteasome inhibitors, to kill the remaining HGSOC cells that otherwise recur and recreate the disease. In addition, the data provide the rationale for rapid repurposing to treat HGSOC of two drugs clinically approved for other uses, as their systemic toxicities have already been assessed. Citation Format: Mahbuba R. Subeha, Alicia A. Goyeneche, Michael A. Lisio, Carlos M. Telleria. The HIV protease inhibitor nelfinavir, alone or in combination with the proteasome inhibitor bortezomib, is cytotoxic to high-grade serous ovarian cancer cells regardless of platinum sensitivity [abstract]. In: Proceedings of the AACR Special Conference on Advances in Ovarian Cancer Research; 2019 Sep 13-16, 2019; Atlanta, GA. Philadelphia (PA): AACR; Clin Cancer Res 2020;26(13_Suppl):Abstract nr A74.