ACTIVATION OF FAS LIGAND RECEPTOR SYSTEM KILLS OVARIAN-CANCER CELL-LINES BY AN APOPTOTIC MECHANISM/

The majority of ovarian cancers originate from the surface epithelium of the ovary and from inclusion cysts derived from the epithelium that becomes sequestered in the stroma. To identify naturally occurring li gands that could activate mechanisms by which these ovarian neoplasms could be eliminated, we have examined the ability of anti-Fas mAb to i nduce apoptosis in two cell lines, HEY and Caov-3, derived from ovaria n carcinomas of surface epithelial origin. Treatment of each cell line with anti-Fas mAb caused chromatin condensation, nuclear segmentation , and apoptotic body formation, indicative of apoptosis. Furthermore w e have shown that anti-Fas mAb activates the sphingomyelin-ceramide si gnal transduction pathway. Sphingomyelin levels were measured by norma l-phase high-performance liquid chromatography interfaced with electro spray mass spectrometry. The six most abundant sphingomyelin species i dentified in Caov-3 cells were 34:1 (d18:1/16:0), 36:1 (d18:1/18:0), 4 0:1 (d18:1/22:0), 41:1(d18:1/23:0), 42:1 (d18:1/24:0), and 42:2 (d18:1 /24:1). Treatment of Caov-3 cells for 30 min caused a 40% decrease in the total sphingomyelin content. Specifically three of these species, 34:1, 40:1, and 42:2, were reduced to 44, 70, and 54% of control value s, respectively. The decrease was attributed to the hydrolysis of sphi ngomyelin. Treatment of these cell lines with ceramide, a product of s phingomyelin hydrolysis, using a cell-permeable synthetic ceramide ana logue C-2-ceramide, also caused the above cells to undergo apoptosis. Thus, the Fas ligand/receptor system, acting through the sphingomyelin -ceramide pathway, provides a mechanism by which ovarian surface epith elial cancer cells can be induced to undergo apoptosis. (C) 1998 acade mic Press.