Using in vitro studies of lymphangiogenesis with a rat mesenteric LEC cell line and in vivo studies of PGE2-induced lymphangiogenesis in angioreactors placed under the skin of nude mice, we demonstrated the roles of tumor as well as host-derived PGE2 in inducing lymphangiogenesis, at least in part, by activating EP4 and VEGFR-3 on LECs [77]. The gene discussed is PTGER4; the disease is neoplasm.