IL4R and neoplasm: However, typically, IL-4Rα is not expressed or is poorly expressed in normal epithelial tissues (as shown here in the colons of healthy WT mice) but it is overexpressed on the surface of many solid tumors, where IL-4 can stimulate angiogenesis through a soluble VCAM-1/alpha4 integrin pathway from endothelial cells [58,59], while in the immune system elevated levels of IL-4 (normally produced by tumor-infiltrating lymphocytes) may contribute to apoptosis resistance of solid tumors [60,61].