Maspin - A novel protease inhibitor with tumor-suppressing activity in breast cancer

Maspin (mammary serpin) is a novel serine protease inhibitor related to the serpin Family with a tumor-suppressing function in breast cancer. Maspin w as originally identified from normal mammary epithelium by subtractive hybr idization and might function as a class II tumor-suppressor gene. Maspin's decreased expression with increased level of malignancy and its loss in met astatic cells is regulated at the transcriptional level. Cytosin methylatio n and heterochromatinization in the promoter region might account for this down-regulation of maspin. Transfection of tumor cells with maspin cDNA inh ibits invasion and motility and decreases tumor growth and metastatic abili ty in nude mice. Maspin interacts with the p53 tumor-suppressor pathway and function as an inhibitor of angiogenesis in vitro and in vivo. The progres sive loss of expression of maspin during tumor progression makes this new p rotein an interesting diagnostic and prognostic marker. The re-expression o f maspin by pharmacological intervention potentially offers a promising app roach as a therapeutic option in breast cancer therapy.