Degradation of the basement membrane by matrix metalloproteinases (MMPs) is an important step in the growth, invasion, metastasis, and angiogenesis of human tumors. MMP-2 and MMP-9 are key enzymes in the degradation of Type IV collagens, a major component of the basement membrane in cancer tissues. MMPs are secreted by stromal fibroblasts near tumor cell clusters, and may also be secreted by tumor cells themselves. EMMPRIN, or extracellular matrix metalloproteinase inducer, is a 58kD protein with two immunoglobulin domains that was originally purified from the plasma membrane of the human LX-1 lung carcinoma cell line. EMMPRIN has been localized on the outer surface of tumor cells, where it interacts with fibroblasts to stimulate the expression of MMPs. Although the mechanism of EMMPRIN’s regulatory action on MMPs is unknown, the p38 MAP kinase pathway has been implicated in the induction of MMP in dermal fibroblasts.