H-ras, but not N-ras, induces an invasive phenotype in human breast epithelial cells: A role for MMP-2 in the H-ras-induced invasive phenotype

Elevated p21ras expression is associated with tumor aggressiveness in breas t cancer including the extent of invasion into fat tissues, infiltration in to lymphatic vessels and tumor recurrence. In the present study, we have ex amined the roles of H-ras and N-ras, members of the human ras gene family, in the pathogenesis of breast cancer. We show that H-ros, but not N-ras, in duces an invasive phenotype in human breast epithelial cells (MCF10A) as de termined by the Matrigel invasion assay, whereas both H-ros and N-ras induc e anchorage-independent growth, as shown by soft agar assay. We examined th e effects of H-ms and N-ras activation on the expression of MMP-2 and MMP-9 , which can degrade type IV collagen, the major structural collagen of the basement membrane. We show that MMP-2 is efficiently induced by H-ras, wher eas MMP-9 induction is more prominent in N-ras-activated MCF10A cells. We a lso show that H-ros-mediated invasiveness is significantly inhibited when t he expression of MMP-2 is down-regulated, using an oligodeoxyribonucleotide complementary to the MMP-2 mRNA, or when MMP-2 activity is blocked by its inhibitor TIMP-2 (tissue inhibitors of matrix metalloproteinase-2). Our res ults show that the H-ras-induced invasive phenotype is associated more clos ely with the expression of MMP-2 in human breast epithelial cells, rather t han the induction of MMP-9 expression, as shown previously for rat embryoni c fibroblasts. (C) 2000 Wiley-Liss, Inc.