HYALURONIC-ACID SECRETED BY MESOTHELIAL CELLS - A NATURAL BARRIER TO OVARIAN-CANCER CELL-ADHESION

The adhesion to mesothelial monolayers of eight cultured ovarian tumou r cell lines was studied in multiwell plates as a model for some of th e interactions of ovarian cancer in the peritoneal cavity. When only t he upper half of the conditioned medium (CM) from a confluent mesothel ial cell culture was aspirated, the adhesion of the tumour cells was l ow (3.5%-36%). When the medium was removed completely the adhesion inc reased. The tumour cell lines showing the greatest enhancement of adhe sion were those which had previously been shown to express the highest amounts of CD44. By adding erythrocyte suspensions to mesothelial cel ls it was shown that there was a pericellular coat around the mesothel ial cells that could be destroyed by aspirating the medium, or by trea ting the medium with hyaluronidase (Hase). Treatment of the CM with Ha se also considerably increased tumour cell adhesion. Furthermore, CM w as shown to contain high amounts of hyaluronic acid (HA). HA blocked a dhesion in the absence of CM, but the effect was not as large as that produced by the pericellular coat. It is proposed that pericellular HA produced by mesothelial cells has an important role in the invasion o f ovarian tumour cells in the peritoneal cavity.