Abstract
Interplay between various lymphangiogenic factors in promoting lymphangiogenesis and lymphatic metastasis remains poorly understood. Here we show that FGF-2 and VEGF-C, two lymphangiogenic factors, collaboratively promote angiogenesis and lymphangiogenesis in the tumor microenvironment, leading to widespread pulmonary and lymph-node metastases. Coimplantation of dual factors in the mouse cornea resulted in additive angiogenesis and lymphangiogenesis. At the molecular level, we showed that FGFR-1 expressed in lymphatic endothelial cells is a crucial receptor that mediates the FGF-2-induced lymphangiogenesis. Intriguingly, the VEGFR-3-mediated signaling was required for the lymphatic tip cell formation in both FGF-2- and VEGF-C-induced lymphangiogenesis. Consequently, a VEGFR-3-specific neutralizing antibody markedly inhibited FGF-2-induced lymphangiogenesis. Thus, the VEGFR-3-induced lymphatic endothelial cell tip cell formation is a prerequisite for FGF-2-stimulated lymphangiogenesis. In the tumor microenvironment, the reciprocal interplay between FGF-2 and VEGF-C collaboratively stimulated tumor growth, angiogenesis, intratumoral lymphangiogenesis, and metastasis. Thus, intervention and targeting of the FGF-2- and VEGF-C-induced angiogenic and lymphangiogenic synergism could be potentially important approaches for cancer therapy and prevention of metastasis.