SPARC, AN EXTRACELLULAR-MATRIX PROTEIN WITH TUMOR-SUPPRESSING ACTIVITY IN HUMAN OVARIAN EPITHELIAL-CELLS

SPARC, also termed osteonectin, BM-40 and 43K protein, is an acidic, c ysteine-rich component of the extracellular matrix that has been shown to be directly regulated by progesterone and dexamethasone and indire ctly by cytokines. By RNA fingerprinting technique, we cloned a SPARC homolog from the normal human ovarian surface epithelial (HOSE) cells and demonstrated that it is expressed at high levels in the normal HOS E cells but at much lower levels in ovarian carcinoma cells in vitro a nd in vivo. Subsequently, we transfected the full length SPARC cDNA in to an ovarian carcinoma cell line SKOV3 and showed that it reduced the growth rate of the cancer cell line in culture and reduced the cell's ability to induce tumours in nude mice. These results suggest that SP ARC may play an important role in growth and and differentiation of th e HOSE cells and support the hypothesis that SPARC functions as a tumo r suppressor.