Patient-Derived Ovarian Cancer Spheroids Rely on PI3K-AKT Signaling Addiction for Cancer Stemness and Chemoresistance

SIMPLE SUMMARY: Epithelial ovarian cancer (EOC) is the most fatal gynecological cancer with poor survival rates and high mortality. EOC patients respond to standard platinum-based chemotherapy in the beginning, but relapse often due to chemoresistance. Ovarian cancer cells disseminate from the ovarian tumors and spread within the abdomen, where ascites fluid supports the growth and transition. Malignant ascites is present in a third of patients at diagnosis and is considered as a major source of chemoresistance, recurrence, poor survival, and mortality. Malignant ascites is a complex fluid that contains a pro-tumorigenic environment with disseminated cancer cells in 3D spheroids form. In this study, we established an ovarian cancer cell line and identified that 3D spheroids develop from the 2D monolayer, and the platinum-resistant phenotype develops due to the aberrant PI3K-AKT signaling in tumor cells. Furthermore, when we used a combinatorial approach of cisplatin with LY-294002 (a PI3K-AKT dual kinase inhibitor) to treat the cisplatin version of both MCW-OV-SL-3 and A-2780 cell lines, it prevented the 3D spheroid formation ability and also sensitized the cells for cisplatin. In brief, our results provided evidence to advance therapeutic approaches to treat cisplatin resistance in ovarian cancer patients. ABSTRACT: Ovarian cancer is the most lethal gynecological malignancy among women worldwide and is characterized by aggressiveness, cancer stemness, and frequent relapse due to resistance to platinum-based therapy. Ovarian cancer cells metastasize through ascites fluid as 3D spheroids which are more resistant to apoptosis and chemotherapeutic agents. However, the precise mechanism as an oncogenic addiction that makes 3D spheroids resistant to apoptosis and chemotherapeutic agents is not understood. To study the signaling addiction mechanism that occurs during cancer progression in patients, we developed an endometrioid subtype ovarian cancer cell line named ‘MCW-OV-SL-3’ from the ovary of a 70-year-old patient with stage 1A endometrioid adenocarcinoma of the ovary. We found that the cell line MCW-OV-SL-3 exhibits interstitial duplication of 1q (q21–q42), where this duplication resulted in high expression of the PIK3C2B gene and aberrant activation of PI3K-AKT-ERK signaling. Using short tandem repeat (STR) analysis, we demonstrated that the cell line exhibits a unique genetic identity compared to existing ovarian cancer cell lines. Notably, the MCW-OV-SL-3 cell line was able to form 3D spheroids spontaneously, which is an inherent property of tumor cells when plated on cell culture dishes. Importantly, the tumor spheroids derived from the MCW-OV-SL-3 cell line expressed high levels of c-Kit, PROM1, ZEB1, SNAI, VIM, and Twist1 compared to 2D monolayer cells. We also observed that the hyperactivation of ERK and PI3K/AKT signaling in these cancer cells resulted in resistance to cisplatin. In summary, the MCW-OV-SL3 endometrioid cell line is an excellent model to study the mechanism of cancer stemness and chemoresistance in endometrioid ovarian cancer.