Cathepsin B expression in cells from primary and metastatic human melanomas. Western blot analysis (left panels) of cathepsin B, cathepsin D, cathepsin L and tubulin in the primary melanoma cell lines PM1 (A) and PM2 (B) and in the metastatic melanoma cell lines MM1 (A) and MM2 (B). Quantitative flow cytometry analysis (right panels) of plasma membrane cathepsin B in PM1 (A) and PM2 (B) cell lines and in MM1 (A) and MM2 (B) cell lines. The values of Western blot signals, reported in the bottom panels of (A) and (B), were obtained by densitometric analysis and expressed as arbitrary units (a.u.). Numbers in the right panels of (A) and (B) represent the median fluorescence values. In the right panels of (A) and (B) statistical analysis performed by non-parametric K/S test is reported.