The CD40/CD40L Pathway Regulates the Aggressiveness of Ovarian Cancer Cells via the Activation of Regulatory B Cells

Ovarian cancer (OC) is a challenging cancer frequently detected at advanced stages. Regulatory B cells (Breg cells) can impair antitumor immunity in patients with OC. The imbalanced serum soluble CD40/CD40L pathway is associated with ovarian tumors. This study aimed to explore the mechanisms involving CD40/CD40L signaling through which Breg cells promote the progression of OC. Breg cells were isolated from peripheral blood samples of 20 patients with OC and 20 healthy controls and identified by flow cytometry. Then, the soluble CD40L concentration in peripheral blood serum of OC patients and healthy volunteers was measured by enzyme-linked immunosorbent assay (ELISA), and we found that the serum soluble CD40L level markedly increased and the proportion of Breg cells was positively correlated with CD40L level in peripheral blood of OC patients. Besides, Breg cells were isolated from spleens of female C57BL/6 WT mice and CD40^-/- mice. Reverse transcription-quantitative polymerase chain reaction, cell counting kit-8 assays, colony formation assays, flow cytometry, Western blotting, wound healing assays, and Transwell assays were conducted to assess the in vitro effect of Breg cells and CD40. We found that Breg cells contributed to cell proliferation, migration, and invasion and suppressed cell apoptosis in OC via the CD40/CD40L pathway. Moreover, we established a xenograft tumor model in female nude BALB/c mice. Tumor size and weight were evaluated, and Western blotting and ELISA were conducted, and we found that Breg cells promoted tumor growth via CD40 signaling. In conclusion, this study demonstrates that Breg cells activated by the CD40/CD40L pathway promotes the aggressiveness of OC cells and tumor growth, indicating that targeting the CD40/CD40L pathway might represent a novel therapeutic option for OC treatment.