Isolation and Eradication of Ovarian CD44+Cancer Stem Cells via Notch Signaling Pathway Mediated by Ectopic Silence of MAML1

Background: Ovarian cancer is the fifth leading cause of cancer-related deaths among women globally. Cancer stem cells (CSCs) are a subpopulation of tumor cells involved in ovarian tumor formation, metastasis, relapse, and chemoresistance. Moreover, the Notch signaling pathway has a pivotal role in CSCs maintenance. Objectives: This study was designed to isolate CSCs from the A2780 cell line and determine the effectiveness of Mastermind-like transcriptional coactivator 1 (MAML1) inhibition, a key factor of the Notch pathway, in targeted therapy against ovarian CSCs. Methods: The CD44(+) or CD133(+) CSCs were isolated from the ovarian A2780 cell line using magnetic cell sorting. The isolated CSCs were also evaluated for stemness markers expression, self-renewal capacity, cell cycle progression, and chemoresistance compared to their negative counterparts. Afterward, MAML1-shRNA was used to inhibit the Notch pathway in CD44(+)CSCs. The role of MAML1 was also evaluated in the CD44(+)CSCs epithelial-mesenchyrnal transition (EMT) process and migration. Results: In addition to the high expression of stemness markers, such as Sox2 and Musashi1, ovarian CD44(+) or CD133(+) CSCs had a high ability for sphere formation, higher percentage in the G1 phase to S phase, and decreased sensitivity to chemotherapy drug compared to CD44- or CD133- cells. Besides, silencing MAML1 significantly reduced the levels of EMT markers and cell migration in CD44+ CSCs, compared to scramble. Conclusion: Mastermind-like transcriptional coactivator 1 can be considered a pivotal factor in the targeted therapy and eradication of CD44(+) CSCs through the inhibition of the Notch signaling pathway in an ovarian cancer patient with a special focus on the ovarian A2780 cell line.