HHV-8 also induces viral and host cytokine production that promotes KS cell proliferation and differentiation (IL-6, oncostatin, alfa-TNF, PDGF, VEGF), and in HIV patients HIV-Tat protein also induces the expression of cytokines (N-kappa B activation, INF gamma, VEGF). This evidence concerns the gene TNF and Kaposi's sarcoma.