The natural FGF-trap long pentraxin 3 inhibits lymphangiogenesis and lymphatic dissemination

The lymphatic vascular system represents a major route for dissemination of several solid tumors, including melanoma. Even though the members of the Vascular Endothelial Growth Factor family VEGF-C and VEGF-A have been shown to drive tumor lymphangiogenesis, experimental evidence indicates that also the pro-angiogenic factor Fibroblast Growth Factor-2 (FGF2) may play a role in the lymphangiogenic switch by triggering the activation of lymphatic endothelial cells (LECs) in cooperation with VEGFs.The soluble pattern recognition receptor Long Pentraxin 3 (PTX3) acts as a natural FGF trap, thus exerting an oncosuppressive role in FGF-dependent tumors. Here, the capacity of PTX3 to modulate lymphangiogenesis was assessed in vitro and in vivo. The results demonstrate that recombinant human PTX3 inhibits the lymphangiogenic activity exerted by the VEGF-A/FGF2/sphingosine-1-phosphate (VFS) cocktail on human and murine LECs. In keeping with in vitro data, a reduced lymphangiogenic response was observed in a lymphangiogenic Matrigel plug assay following the subcutaneous injection of the VFS cocktail in PTX3-overexpressing transgenic TgN(Tie2-hPTX3) mice when compared to wild-type or Ptx3 null animals. Accordingly, the capacity of B16F10-VEGFC-luc melanoma cells to colonize the primary tumor-draining lymph node after grafting into the foot pad was dramatically impaired in PTX3-overexpressing mice.Together with the observation that both the VFS cocktail and melanoma cell conditioned media caused a significant downregulation of PTX3 expression in LECs, these data indicate that the FGF trap activity of PTX3 may exert a key effect in the modulation of lymphangiogenesis and tumor metastatic dissemination.