Non-melanoma skin cells, such as basal cell carcinoma (BCC) and squamous cell carcinoma (SCC), express receptors for IL-17 and IL-22 and Nardinocchi et al. [16] show that these factors can increase tumor cell proliferation and migration in vitro. The enhanced proliferation and migration of BCC and SCC cell lines in response to IL-17 and IL-22 is associated with the induction of IL-6 and IL-8. The recruitment of myeloid cells (CD11c+) may constitute one of the pro-tumorigenic mechanisms of action of Th17 cells. Th17 and Th22 cells are depicted in the figure, but the cellular source of their signature cytokines in skin cancer remains to be determined. Using xenograft assays, Nardinocchi et al. show that these cytokines also accelerate tumor growth in vivo. IL-17 treatment of the SCC cell line CAL 27 induced NF-κB signaling in these cells and IL-22 treatment activated the Erk1/2 and STAT3 signaling pathway, which may be responsible for tumor progression.