Figure 1.

Tumor-promoting actions of VEGF in skin carcinogenesis. Epithelial tumor cells produce large amounts of VEGF in the skin, as depicted by the arrow on the left side of each panel. Traditionally, VEGF has been recognized only for its ability to stimulate angiogenesis through paracrine actions on endothelial cells (a). However, additional functions of VEGF have now been described. Recent studies have suggested that VEGF can affect epithelial cells in an autocrine manner by stimulating proliferation, maintaining stemness, or possibly by promoting survival (b). Additionally, macrophages can be recruited to skin tumors by VEGF through paracrine mechanisms. These macrophages are capable of producing an array of mediators that can support the growth of tumor cells in the skin.