Amphiregulin (AR) and epidermal growth factor effects on expression and activity of the extracellular matrix metalloproteinase inducer (EMMPRIN) were examined in NS2T2A1 breast tumor cells. Both growth factors induced mRNA and protein expression of EMMPRIN, and matrix metalloproteinase (MMP) -2 and -9 enzymatic activity. The induction of EMMPRIN by AR was mediated by epidermal growth factor receptor (EGFR) tyrosine kinase activation and inhibited by ZD1839. AR and EGFR antisense (AS) cDNAs inhibited EMMPRIN expression and MMP activity. Coculture of NS2T2A1V expressing AR- or EGFR-AS with fibroblasts and endothelial cells showed a decreased MMP activity. In parallel, nude mice tumors derived from AR and EGFR-AS cells revealed reduced level of EMMPRIN and MMP activity. AR and epidermal growth factor, therefore, regulate EMMPRIN and its MMP-mediated expression, identifying EGFR signaling as critical to this regulation.