S100B induces angiogenesis via the clathrin/FOXO1/β-catenin signaling pathway and contributes to Bevacizumab resistance in epithelial ovarian cancer.

INTRODUCTION: Bevacizumab (BEV), the most common antiangiogenic agent for treating ovarian cancer, prolongs progression-free survival (PFS) but does not significantly improve overall survival (OS). Improving the limited clinical benefit of BEV remains a major challenge in ovarian cancer treatment. Although several studies have explored the mechanisms underlying tumor resistance to BEV, the clinical translation of these findings to overcome BEV resistance has been limited. OBJECTIVES: To identify the key molecules and mechanisms that modulate ovarian cancer sensitivity to BEV. METHODS: RNA sequencing was conducted on BEV-sensitive and BEV-resistant mouse ovarian cancer tissue to identify differentially expressed genes (DEGs). A prognostic assessment was performed and a risk signature was constructed using these DEGs and the BEV-related sequencing datasets. S100B was identified and assessed in angiogenesis using tube formation, 3D fibrin bead sprouting, wound healing, and migration assays. Downstream targets and signaling pathways of S100B in HUVECs were identified by proteomics and validated by western blot. The effect of S100B inhibitors on BEV efficacy was evaluated using in vivo experiments. RESULTS: A BEV-related prognostic signature comprising 11 genes was constructed. Of these, S100B expression significantly increased in BEV-resistant mouse ovarian cancer tissue and significantly correlated with poor PFS and OS of ovarian cancer patients treated with a BEV combination chemotherapy. HUVECs co-cultured with S100B-overexpressing ovarian cancer cells promoted tube formation, sprouting, and migration. Exogenous S100B entered HUVECs via clathrin-mediated endocytosis, downregulated FOXO1 expression, and promoted β-catenin nuclear translocation and transcriptional activity, ultimately enhancing tube formation. The S100B inhibitor pentamidine significantly increased BEV responsiveness and prolonged survival in ovarian tumor-bearing mice. CONCLUSION: S100B is a key molecule regulating ovarian cancer sensitivity to BEV. Paracrine S100B secreted by ovarian cancer cells acts on HUVECs, promoting angiogenesis through the FOXO1/β-catenin pathway. Pentamidine combined with BEV holds potential for overcoming BEV resistance in clinical use.