High-grade epithelial ovarian cancer is a fatal disease in women frequently associated with drug resistance and poor outcomes. We previously demonstrated that a marine-derived compound MalforminA1 (MA1) was cytotoxic for the breast cancer cell line MCF-7. In this study, we aimed to examine the effect of MA1 on human ovarian cancer cells. The potential cytotoxicity of MA1was tested on cisplatin-sensitive (A2780S) and cisplatin-resistant (A2780CP) ovarian cancer cell lines using AlamarBlue assay, Hoechst dye, flow cytometry, Western blot, and RT-qPCR. MA1 had higher cytotoxic activity on A2780S (IC50 = 0.23 µM) and A2780CP (IC50 = 0.34 µM) cell lines when compared to cisplatin (IC50 = 31.4 µM and 76.9 µM, respectively). Flow cytometry analysis confirmed the cytotoxic effect of MA1. The synergistic effect of the two drugs was obvious, since only 13% of A2780S and 7% of A2780CP cells remained alive after 24 h of treatment with both MA1 and cisplatin. Moreover, we examined the expression of bcl2, p53, caspase3/9 genes at RNA and protein levels using RT-qPCR and Western blot, respectively, to figure out the cell death mechanism induced by MA1. A significant down-regulation in bcl2 and p53 genes was observed in treated cells compared to non-treated cells (p < 0.05), suggesting that MA1 may not follow the canonical pathway to induce apoptosis in ovarian cancer cell lines. MalforminA1 showed promising anticancer activity by inducing cytotoxicity in cisplatin-sensitive and cisplatin-resistant cancer cell lines. Interestingly, a synergistic effect was observed when MA1 was combined with cisplatin, leading to it overcoming its resistance to cisplatin.

Objectives: New compounds are needed to overcome the resistance to commonly used cytotoxic chemotherapy for epithelial ovarian cancer. Marine sponges are a rich source of diverse chemical compounds and hymenialdisine has been found to have antiproliferative effects. This study aimed to investigate the cytotoxic effect of hymenialdisine in cisplatin-sensitive and cisplatin resistant ovarian cancer cell lines. Methods: This study took place at Sultan Qaboos University, Muscat, Oman between August and November, 2019. The anti-cancer effects of hymenialdisine or cisplatin were assessed using treating cells with different concentrations of hymenialdisine and cisplatin. Cell viability was determined using the AlamarBlue® Assay. Results: The half-maximal inhibitory concentration (IC50) of cisplatin was estimated at 31.4 μM for A2780S and 76.9 μM for A2780CP, whereas the IC50 of hymenialdisine was evaluated at 146.8 μM for A2780S cells. Despite the higher concentrations of hymenialdisine (up to 300 μM), IC50 could not be determined for the A2780CP cell line. Conclusion: When compared to cisplatin, hymenialdisine was less toxic against both A2780S and A2780CP ovarian cancer cell lines.