Differential expression of c‐Met in Kaposi's sarcoma according to progression stage and HIV infection status

Several cytokines, growth factors and the HIV transactivator Tat have been shown to be involved in the pathogenesis of Kaposi's sarcoma (KS). Hepatocyte growth factor/scatter factor (HGF) is an angiogenic cytokine that stimulates proliferation of spindle cells cultured from human KS lesions. The receptor for HGF, the c‐Met protein, is expressed by endothelial cells, dermal dendrocytes and KS tumor cells both in vitro and in vivo . KS cells synthesize and secrete HGF and express the hepatocyte growth factor receptor (c‐Met), thus providing an autocrine loop for tumor proliferation and neovascularization which can be enhanced by proinflammatory cytokines. We studied the immunohistochemical expression of c‐Met in 40 cases of classical Kaposi's sarcoma (C‐KS) and AIDS‐associated cutaneous Kaposi's sarcoma (AIDS‐KS), including 22 plaque stage lesions (12 AIDS‐KS cases) and 18 tumor stage lesions (7 AIDS‐KS cases). Statistically significant differences in the average intensity of immunohistochemical staining according to the type of lesions (progression stages) and the serologic status ot the patients were identified. The staining intensity of c‐Met was stronger in tumors than in plaques. When only plaques were taken into consideration, the mean staining score was nearly twice as high in C‐KS as in AIDS‐KS.