In vitro pharmacological characterization of TKI-28, a broad-spectrum tyrosine kinase inhibitor with anti-tumor and anti-angiogenic effects

Abstract

Tyrosine kinases are used as important biomarkers in many tumor types. Preclinical and clinical anti-tumor studies have shown that broadly acting tyrosine kinase inhibitors may be more useful than specific inhibitors, since the former might overcome redundancies and crosstalk in tumor cell growth signaling pathways. Here, we aim to identify a novel potent tyrosine kinase inhibitor. Computer modeling of the pyrido-pyrimidine class compound, TKI-28(6-(2,6-dichlorophenyl)-8-methyl-2-phenylamino-8H-pyrido[2,3-d] pyrimidine-7-one), predicted that the compound would dock well in the ATP pocket of the ErbB-2 tyrosine kinase, yielding a high binding affinity for ErbB receptors. Biochemical studies revealed that TKI-28 potently inhibited the activities of tyrosine kinases such as ErbB-2, EGFR, KDR, PDGFRß, c-kit and c-Src, but had little effect on Fit-1 in cell-free system. TKI-28 also efficiently blocked autophosphorylation of the listed receptor tyrosine kinases, and subsequently downregulated phosphorylation of many downstream signaling proteins at the cellular level. TKI-28 exhibited a more potent anti-proliferative activity against EGF- and neuregulin-stimulated SK-OV-3 cells versus serum-stimulated cells, accompanied by apparent induction of apoptosis. Finally, TKI-28 was found to possess anti-angiogenic effects, characterized by inhibition of cell proliferation driven by EGF, VEGF and PDGF, as well as decreased cell migration and tube formation in HMECs. These results collectively highlight the pharmacological characteristics of TKI-28 as a broad-spectrum tyrosine kinase inhibitor, suggesting that it has great potential as an anti-cancer and anti-angiogenesis agent. ©2005 Landes Bioscience.