Anti-FGF2 approaches as a strategy to compensate resistance to anti-VEGF therapy: Long-pentraxin 3 as a novel antiangiogenic FGF2-antagonist

Angiogenesis, the formation of new blood vessels from the endothelium of the existing vasculature, plays a pivotal role in tumor growth, progression and metastasis. Over the last 30 years, numerous pro- and antiangiogenic molecules, their ligands, and intracellular signaling pathways have been identified, and significant efforts have been undertaken to develop antiangiogenic strategies for cancer therapy. Agents that selectively target vascular endothelial growth factor (VEGF) and its receptors have shown promising activity in clinical trials and have been approved for use in selected cancer indications. However, patients may ultimately develop resistance to these drugs. One proposed mechanism of tumor escape from anti-VEGF therapy is the up-regulation of fibroblast growth factor-2 (FGF2). FGF2 is a pleiotropic, angiogenesis inducer belonging to the family of the heparin-binding FGF growth factors. FGF2 is expressed by numerous tumor types and exerts its proangiogenic activity by interacting with tyrosine kinase receptors, heparan-sulfate proteoglycans, and integrins expressed on the endothelial cell surface. Experimental evidence suggests that targeting FGF2, in addition to VEGF, might provide synergistic effects in the treatment of angiogenesis-related diseases, including cancer. Several FGF2 inhibitors, with different chemical structure and mechanism of action, have been identified. Recent observations have shown the ability of the soluble pattern recognition receptor long-pentraxin-3 (PTX3) to bind FGF2, thus acting as a FGF2 antagonist. PTX3 binds FGF2 with high affinity and specificity. This interaction prevents the binding of FGF2 to its cognate tyrosine kinase receptors, leading to inhibition of the angiogenic activity of the growth factor. Further, preliminary observations support the hypothesis that PTX3 may inhibit FGF2-mediated tumor angiogenesis and growth. The identification of the FGF2-binding domain in the unique N-terminal extension of PTX3 has allowed the design of PTX3-derived synthetic peptides endowed with significant antiangiogenic activity in vitro and in vivo. These findings may provide the basis for the development of novel antiangiogenic FGF2 antagonists, with potential implications for cancer therapy.