Background: The expression of the proteinases cathepsins L and B are induced in tumors by malignant transformation, growth factors, and tumor promoters suggesting they play an important role in tumor invasion and metastasis.
Methods: By immunohistochemistry, procathepsin L and cathepsin B were studied in patients with Kaposi's sarcoma (KS). Formalin-fixed and paraffin-embedded tissues from 29 cases of KS (AIDS-associated KS, n = 24; non-AIDS-associated KS, n = 5) were immunolabeled with the polyclonal antibody directed against procathepsin L and the antisera directed against cathepsin B.
Results: Normal epidermis, eccrine sweat glands, and hair follicle expressed both cathepsins. We also found a positive staining for procathepsin L in normal blood vessels. In both "angiomatous" and "fibroblastic" lesions of KS no expression of these enzymes was observed.
Conclusions: These findings support the hypothesis of a benign autochthonous origin of the lesions, such as a hyperplasia.