Vascular endothelial growth factor receptor-3 and focal adhesion kinase bind and suppress apoptosis in breast cancer cells

Focal adhesion kinase (FAK) and vascular endothelial growth factor receptor-3 (VEGFR-3) are protein tyrosine kinases that are overexpressed in human cancer and play an important role in survival signaling. In addition to its involvement with cell survival, VEGFR-3 is a primary factor in lymphatic angiogenesis. Because FAK function is regulated by its COOH terminus (FAK-CD), we used FAK-CD as a target to identify binding partners. We isolated a peptide from a phage library that bound to FAK-CD, specifically the focal adhesion targeting domain of FAK and was homologous to VEGFR-3, suggesting these two tyrosine kinases physically interact. We have also shown that VEGFR-3 is overexpressed in human breast tumors and cancer cell lines. For the first time, we have shown the physical association of FAK and VEGFR-3. The association between the NH2 terminus of VEGFR-3, containing the peptide identified by phage display, and the COOH terminus of FAK was detected by in vitro and in vivo binding studies. We then coupled a 12-amino-acid VEGFR-3 peptide, AV3, to a TAT cellular penetration sequence and showed that AV3 and not control-scrambled peptide caused specific displacement of FAK from the focal adhesions and affected colocalization of FAK and VEGFR-3. In addition, AV3 peptide decreased proliferation and caused cell detachment and apoptosis in breast cancer cell lines but not in normal breast cells. Thus, the FAK/VEGFR-3 interaction may have a potential use to develop novel molecular therapeutics to target the signaling between FAK and VEGFR-3 in human tumors.