Expression of stromelysin 3 in the stromal elements of human basal cell carcinoma

In basal cell carcinoma, release of proteolytic activity is implicated in extracellular matrix degradation and tumor infiltration. The stromelysin metalloproteinase family is a major candidate for the matrix proteolytic activity in infiltrative tumors. However, in murine models of basal cell carcinoma, neither stromelysin 1 nor 2 appears to play a role in tumor infiltration. We have analyzed the expression of the newly described stromelysin 3 in human basal cell carcinoma using Northern blot analysis and in situ hybridization. In 12 of 14 cases, levels of stromelysin 3 expression were more than tenfold above those observed in normal skin. In one of five cases of squamous cell carcinoma, stromelysin 3 expression was tenfold above levels seen in normal skin. Stromelysin 3 expression was either undetectable or extremely weak in all five cases of infiltrative malignant melanoma. In basal cell carcinoma, stromelysin 3 transcripts were localized by in situ hybridization to the stromal tissue immediately adjacent to basal cell carcinoma, the tumor cells themselves being negative. Therefore, expression of stromelysin 3 in stromal cells may be expected to play a significant role in destruction of the basal membrane zone and extracellular matrix in basal cell carcinoma invasion.