How to win the ovarian cancer stem cell battle: destroying the roots.

Ovarian cancer has the highest mortality rate among gynecologic malignancies. The combination of cytoreductive surgery and chemotherapy is the standard regimen for the treatment of ovarian cancer. The initial treatment is usually effective, but many patients with ovarian cancer experience recurrence, and treatment options for recurrent disease remain challenging. Cancer stem cells (CSCs) are suggested to play an essential role in cancer recurrence after initial chemotherapy. Furthermore, they are of great interest as CSCs may also be involved in chemotherapy susceptibility. Thus, understanding the characteristics and mechanisms by which CSCs display resistance to therapeutic agents is important to design effective cancer treatments. In this review, we describe and discuss current therapeutic regimens for ovarian cancer, as well as the various CSC markers, association between CSCs and disease progression, correlation of CSCs with poor prognosis, enrichment of CSCs in tumor tissues following repeated chemotherapy cycles, activation of major signaling pathways following chemotherapy, and potential inhibitors that suppress these signaling cascades. In addition, clinical trials evaluating novel targeted therapies to overcome chemotherapy resistance will be reviewed. The combination of traditional chemotherapy and CSC-targeted therapy could be an effective and promising anticancer treatment for ovarian cancer. Understanding the biological properties of CSCs and the mechanism of chemotherapy resistance are critical to design and develop new therapeutic strategies to overcome CSC-associated chemotherapy resistance.