Here, we show the presence of the IGF-IR in biopsies taken from patients with AIDS/HIV-related KS, and further demonstrate that the IGF system is essential for cell growth and for mediating antiapoptotic signals in a KS cell line (KSIMM) that has the characteristics of the KS SCs and produce large highly vascularised tumours when injected s.c. in nude mice (Albini et al, 1997). This evidence concerns the gene IGF1R and Kaposi's sarcoma.