Vitamin D counteracts tumor progression interacting with not only normal and cancer cells but also cancer-associated stromal cells and cancer stem cells within the tumor microenvironment by upregulating (tumor suppressors genes, TGFβ, and PDF) or downregulating (STAT3, NF-kB, TNFα, cyclins, and oncogenes) different factors that result in anti-inflammatory, anti-angiogenic, anti-proliferative, pro-apoptotic, and pro-differentiating events (17, 18). The gene discussed is STAT3; the disease is cancer.