Increased activity of cathepsin B in fibroblasts isolated from primary melanoma in comparison to fibroblasts from normal skin.

We determined activity of cathepsin B in early-passage fibroblasts isolated from primary melanoma and in fibroblasts from normal skin. Our results show an up to 5-fold increase in activity of cathepsin B in the tumor-derived fibroblasts in comparison to the fibroblasts from normal skin. We conclude that fibroblasts isolated from melanoma tissue are altered with regard to their specific activity of cathepsin B and preserve this elevated activity in early-passage cell culture. The data support the idea that stromal cells are not passive elements of the peritumoral environment but actively participate in the production of proteolytic enzymes.