Regulation of Growth Factor Release By Proteases Inhibitors in Breast Cancer

摘要

The aim of this proposal was to examine the role of proteases and protease inhibitors in the regulation of growth factor release in breast cancer. To this end we report the cloning, sequencing and properties of a TGFalpha- releasing protease present in breast ductal epithelium from an MCF-7 breast cancer cell cDNA library. The deduced 321 amino acid open reading frame shows a high degree of homology with the cell-surface serine proteases enteropeptidase, prekalikrein, hepsin and prostasin. Northern analysis, showed the presence of an approximately 4.2 kb mRNA species in total RNA from MCF-7 cells and normal breast ductal epithelial cells. A GST fusion protein, constructed from a portion of the PCR-7 open reading frame cDNA sequence, was used to raise antibodies in rabbits. On western blot analysis, the antibody recognized a 33 kDa polypeptide in MCF-7 cells under both reducing and non-reducing conditions. This antibody inhibited TPA-induced TGFalpha release from MCF-7 cells in a dose-dependent manner as compared to pre-immune sera. Immunohistochemistry of paraffin sections from normal and cancerous human breast tissue showed that the PCR-7 protein was restricted to the surface of ductal epithelial cells where it co-localized with the epidermal growth factor receptor.