The present study sought to determine the anti-tumor effects of OXA-11, a potent, novel small-molecule amino pyrimidine inhibitor (1.2 pM biochemical IC(50)) of focal adhesion kinase (FAK). In studies of cancer cell lines, OXA-11 inhibited FAK phosphorylation at phospho-tyrosine 397 with a mechanistic IC(50) of 1 nM in TOV21G tumor cells, which translated into functional suppression of proliferation in 3-dimensional culture with an EC(50) of 9 nM. Studies of OXA-11 activity in TOV21G tumor-cell xenografts in mice revealed a pharmacodynamic EC(50) of 1.8 nM, indicative of mechanistic inhibition of pFAK [Y397] in these tumors. OXA-11 inhibited TOV21G tumor growth in a dose-dependent manner and also potentiated effects of cisplatin on tumor cell proliferation and apoptosis in vitro and on tumor growth in mice. Studies of pancreatic neuroendocrine tumors in RIP-Tag2 transgenic mice revealed OXA-11 suppression of pFAK [Y397] and pFAK [Y861] in tumors and liver. OXA-11 given daily from age 14 to 17 weeks reduced tumor vascularity, invasion, and when given together with the anti-VEGFR-2 antibody DC101 reduced the incidence, abundance, and size of liver metastases. Liver micrometastases were found in 100 % of mice treated with vehicle, 84 % of mice treated with OXA-11, and 79 % of mice treated with DC101 (19-24 mice per group). In contrast, liver micrometastases were found in only 52 % of 21 mice treated with OXA-11 plus DC101, and those present were significantly smaller and less numerous. Together, these findings indicate that OXA-11 is a potent and selective inhibitor of FAK phosphorylation in vitro and in vivo. OXA-11 slows tumor growth, potentiates the anti-tumor actions of cisplatin and--when combined with VEGFR-2 blockade--reduces metastasis of pancreatic neuroendocrine tumors in RIP-Tag2 mice.
Keywords: Cisplatin; Focal adhesion kinase; Liver metastasis; Pancreatic islet cell tumors; RIP-Tag2 transgenic mice; Vascular endothelial growth factor receptor-2.