Abstract 4087: ALDH1A1 inhibitor induces cell cycle arrest and reduces cell proliferation of cisplatin-resistant ovarian cancer cells

Introduction: Ovarian cancer is one of the most common malignancies among women that causes severe mortality in USA and globally. Despite advances in cancer treatments in the last few decades, there is no substantial improvement in the survival rates of patients with advanced ovarian cancers. This is mainly attributed to drug resistance and tumor recurrence. Most patients develop resistance to platinum compounds, which are often used as the first-line therapy. Several studies have shown that aldehyde dehydrogenase (ALDH1A1) plays an important role in cancer stemness and confers resistance to cell death induced by platinum compounds used to treat ovarian cancers. Therefore, in this study, we determined the effect of a small-molecule inhibitor of ALDH1A1 (A37) in cisplatin-resistant ovarian cancer cells and assessed it9s molecular mechanism of action. Experimental methods: The cisplatin-resistant ovarian cancer cells (A2780-CR) were exposed to various concentrations of ALDH1A1 inhibitor (A37) and then the cell proliferation by water-soluble tetrazolium salt (WST-1) assay, cell cycle analysis by flow cytometry and oxygen consumption rate (OCR) by Seahorse extracellular flux analysis (Seahorse XFe24 Analyzer) were performed. Furthermore, the protein expression of critical signaling molecules that modulate the proliferation of ovarian cancer cells was assessed by western blot analysis. Results: A37 treatment drastically decreased the proliferation of A2780-CR cells at 24 and 48 h. In addition, cell cycle analysis revealed a significant increase in G1 phase and dramatic decrease in S phase of the cell cycle upon A37 treatment. Interestingly, A37 suppressed the basal OCR, an indicator of mitochondrial respiration. Furthermore, A37 reduced the protein expression of mammalian target of rapamycin (mTOR), which plays a critical role in cancer cell cycle and proliferation. Conclusions: Our findings indicate that the ALDH1A1 inhibitor (A37) induces cell cycle arrest and suppresses the cell proliferation of cisplatin-resistant ovarian cancer cells, possibly through downregulation of mTOR signaling. Most importantly, A37 affects the cancer cell metabolism by reducing the mitochondrial respiration. Taken together, our study highlights the importance of potential therapeutic implication of ALDH1A1 inhibitor towards the treatment of chemoresistant-ovarian cancers. Citation Format: Ilangovan Ramachandran, Sivakumar Ramadoss, Selvendiran Karuppaiyah, Lauren Nathan, R. Ileng Kumaran, Gautam Chaudhuri. ALDH1A1 inhibitor induces cell cycle arrest and reduces cell proliferation of cisplatin-resistant ovarian cancer cells [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 4087.