Regulation of Membrane Proteases Associated with Breast Cancer.

Seprase is a homodimeric 170 kDa integral membrane gelatinase whose expression correlates with the invasiveness of the human melanoma cell line LOX. We are interested in determining its potential role in breast cancer metastasis since seprase mRNA has been detected in the breast carcinoma cell lines MDA-MB-436 and Hs 578T. Sequence analysis of a cDNA clone from LOX indicates that it is a type I integral membrane glycoprotein that belongs to the family of nonclassical serine hydrolases. Additional sequence analysis of seprase cDNA clones from LOX, MDA-MB-436 and the fibroblast line WI-38 strongly suggests that seprase and fibroblast activation protein a are the same protein. We have produce stable seprase transfectants for the breast carcinoma cell lines MCF-7,MDA-MB-23 1 and MDA-MB-43 which will be tested in in vitro matrix degradationinvasion assay systems. Unexpectedly, we have discovered that seprase pre-mRNA undergoes alternative exon splicing giving rise to a truncated mRN which cannot encode the membrane form of seprase but potentially encodes a truncated intracellular form of seprase. Preliminary RNA analysis of Hs 578Bst and Hs 578T suggests that the truncated RNA is up regulated in the breast carcinoma.