Introduction Cancer stem-like cells (CSCs) are recognized to be responsible for chemoresistance and tumor recurrence owing to their self-renewal capacity and differentiation potential. Although WEE1 is a promising target for anticancer therapies, its function in ovarian CSCs remains unknown. We present evidence that WEE1 regulates CSC properties and tumor resistance to carboplatin through a microRNA-dependent mechanism.

Methods Plasmid DNA constructs were transfected into human ovarian cancer cell lines. RNA and protein were extracted from pathologically confirmed tumor tissues. The SKOV3 spheroid tumor model were developed. Immunofluorescence analyses were performed on the xenograft tumors. miR-424 and miR-503 were detected by quantitative real-time PCR and western blot analysis. Spheroid formation assay was performed to investigate the presence and self-renewal ability of CSCs.

Results We found that WEE1 expression is upregulated in ovarian cancer spheroids because of the decreased expression of miR-424 and miR-503, which directly target WEE1. The overexpression of miR-424/503 suppressed CSC activity by inhibiting WEE1 expression, but restoring WEE1 expression reversed this effect. Furthermore, we demonstrated that NANOG modulates the miR-424/503-WEE1 axis that regulates the properties of CSCs. We also demonstrated the pharmacological restoration of the NANOG-miR-424/503-WEE1 axis and attenuation of ovarian CSC characteristics in response to atorvastatin treatment. Lastly, miR-424/503- mediated WEE1 inhibition re-sensitized chemoresistant ovarian cancer cells to carboplatin. Additionally, combined treatment with atorvastatin and carboplatin synergistically reduced tumor growth, chemoresistance, and peritoneal seeding in the intraperitoneal mouse models of ovarian cancer.

Conclusion/Implications We identified a novel NANOG-miR-424/503-WEE1 pathway for regulating ovarian CSCs, which has potential therapeutic utility in ovarian cancer treatment.