MAPK3 and fibrosarcoma: In keeping with its FGF trapping antagonist potential (13, 14, 17), the inhibitory activity exerted by PTX3 overexpression in fibrosarcoma cells is paralleled by a significant decrease of FGFR3 phosphorylation, as well as of the activation of mitogen activated protein kinase Erk1/2 and AKT in murine MC17-51 cells, and of FGFR3/Akt activation in HT-1080 cells (Figure 2C).