Isolation and eradication of ovarian CD44+ cancer stem cells via Notch signaling pathway mediated by ectopic silence of MAML1

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. 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.

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-mesenchymal transition (EMT) process and migration.

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.

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.