Expression of transforming growth factor beta and transforming growth factor beta receptors on AIDS-associated Kaposi's sarcoma

Several humoral growth factors may contribute to the development and growth of AIDS-associated Kaposi's sarcoma (KS), They are either provided by chronically activated cells of the immune system or in an autocrine/paracrine manner by the neoplastic cells themselves, Transforming growth factor beta (TGF-beta) may directly enhance the growth of KS cells and tumor matrix formation, To mediate a signal both TGF-beta receptors type I and type II (T beta R-I and T beta R-II) have to be expressed, We investigated the expression of TGF-beta, TGF-beta receptors types I and II, and endoglin, a nonsignaling-type T beta R-III, by means of immunohistochemistry on skin biopsies from patients with AlDS-related KS, We found that the TGF-beta ligand was expressed by KS cells in 9 of 11 samples, T beta R-II was strongly expressed in 10 of 12 samples, but none of the investigated tumor samples stained for T beta R-I. Endoglin was weakly expressed on all KS lesions and stained the endothelium of tumor-associated vessels in 92% of the samples, These findings show that most KS lesions have the ability to produce TGF-beta and that KS cells maintain a high expression of T beta R-II in the absence of T beta R-I, which may allow KS to escape growth inhibitory effects of endocrine or paracrine TGF-beta.