Interactions of human peritoneal mesothelial cells with serous ovarian cancer cell spheroids--evidence for a mechanical and paracrine barrier function of the peritoneal mesothelium.

BACKGROUND: Ovarian carcinoma spreads by implantation of tumor cells onto the peritoneal mesothelium. We established a 3-dimensional coculture model to simulate the interactions of ovarian carcinoma cell aggregates with human peritoneal mesothelial cells (HPMC).

METHODS: Multicellular tumor spheroids (MCTS) of the human ovarian cancer cell line SK-OV-3 were directly inoculated onto either confluent HPMC monolayers or their submesothelial matrix or were cocultured with mesothelium without direct cellular contact.

RESULTS AND DISCUSSIONS: Inoculation of MCTS onto submesothelial matrix resulted in rapid attachment (within 30 minutes) of the tumor cell aggregates followed by rapid dissemination (within 12 hours) and growth of tumor cells. Intact mesothelium increased the time required for MCTS attachment (up to 180 minutes) and led to almost complete inhibition of tumor cell dissemination and to 47% tumor growth suppression. Bromodeoxyuridine incorporation into tumor cell nuclei was almost completely abolished in cocultured MCTS. Growth also was inhibited in MCTS treated with supernatants of HPMC. Analysis of coculture supernatants revealed that HPMC-derived transforming growth factor β (TGF-β) was almost completely bound by MCTS. Addition of a function-blocking anti-TGF-β antibody (30 μg/mL) to the cocultures abrogated the growth inhibitory effect of the mesothelium by 50%.

CONCLUSIONS: The present model provides a dynamic system to study the complex interactions of ovarian carcinoma cells with HPMC over extended periods and suggests that the mesothelium constitutes a mechanical and partly TGF-β-mediated paracrine barrier to the progression of ovarian cancer.