Objective: To elucidate tumor-stromal interactions during tumor invasion by assessing the expression of proteolytic enzymes by carcinoma-associated fibroblasts (CAFs) in vivo using complementary DNA (cDNA) array analysis. Methods: Tumor-associated stroma was isolated from tumor and adjacent mucosal specimens of the same patient by laser capture microdissection, and the messenger RNA (mRNA) was assessed by cDNA microarray specific for proteolytic enzymes and their inhibitors. Protein overexpression was then analyzed by immunoblotting of primary fibroblast isolates derived from skin, mucosa, and tumor specimens. Results: Array analysis of 4 tumor and 4 adjacent mucosal samples demonstrated significant (2.6-fold) overexpression of membrane type 1 matrix metalloproteinase (MT1-MMP) but not of serine proteases or other matrix metalloproteinases. Analysis of normal dermal fibroblasts, normal mucosal fibroblasts, and CAFs similarly demonstrated up-regulation of MT1-MMP. Conclusions: These results suggest that MT1-MMP mRNA is specifically up-regulated in CAFs in vivo whereas MT1-MMP protein is specifically up-regulated in CAFs in vitro. Known to induce tumor cell invasion when expressed in tumor cells, CAF expression of MT1-MMP may be important in the stromal response to tumor cells that characterizes the desmoplastic reaction.