IL6 and Kaposi's sarcoma: The role of fibroblasts contributing to the paracrine growth signaling in KS is more established; latent infection of fibroblasts with KSHV leads the fibroblasts to secrete pro-inflammatory cytokines such as VEGF-A, IL-6, IL-8, and IL-10, as well as matrix metalloproteinases that break down the extracellular matrix and increase tumor cell invasion,155, 156 and are required by KS spindle cells for in vitro growth and to maintain their tumorigenic potential in nude mice.157