Tumor cell-fibroblast heterotypic aggregates in malignant ascites of patients with ovarian cancer

Ascitic multicellular aggregates (MCAs) promote peritoneal metastasis of ovarian cancer. The aim of the present study was to elucidate the role of cancer-associated fibroblasts (CAFs) in MCA formation and metastasis in patients with high-grade serous ovarian cancer (HGSOC). Immunohistochemistry was used to identify the cell phenotypes and the presence of CAFs in ascitic MCAs. The role of CAFs in tumor-cell MCA formation was assessed by co-culture in suspension. Primary ascitic tumor cells and omental CAFs were used to generate ex vivo MCAs in hanging drops, and the invasiveness of MCAs was evaluated by mesothelial clearance and adhesion assays in vitro and in vivo. MCAs containing CAFs and tumor cells were identified in the ascitic fluid. CAFs facilitated tumor cell aggregation and compaction to form MCAs, and enhanced the mesothelial clearance and adhesion abilities of tumor-cell MCAs. These findings suggest that ascitic CAFs promote peritoneal metastasis by forming heterotypic aggregates with tumor cells, and that they may serve as potential targets for the treatment of HGSOC.