Peritoneal mesothelial cells as a significant source of ascitic immunostimulatory protein 90K.

The tumor associated antigen 90K is known to possess cytokine-like modulatory properties on the cellular immune system, whereby accessory cells are the primary target of this molecule. In 67 ovarian cancer patients presenting with significant amounts of ascites, immunostimulatory protein 90K was detected in all ascitic fluid samples examined. Furthermore, 90K levels correlated to ascitic s-IL-2R content. To elucidate the source of protein 90K in ascitic fluid; its in vitro release was investigated in primary cultured normal human peritoneal mesothelial cells (HPMC). Peritoneal mesothelium was found to produce five-fold more 90K than ovarian cancer cells. Release of protein 90K was significantly increased by treatment with IFN-gamma in both mesothelial and ovarian cancer cells. In contrast neither IL-1 beta nor TNF-alpha treatment consistently influenced the secretion of 90K in either cell type.