Identification of potential biomarkers for measuring inhibition of Src kinase activity in colon cancer cells following treatment with dasatinib.
ABSTRACT Elevated levels of Src kinase expression have been found in a variety of human epithelial cancers. Most notably in colon cancer, elevated Src expression correlates with malignant potential and is also associated with metastatic disease. Dasatinib (BMS-354825) is a novel, orally active, multi-targeted kinase inhibitor that targets Src family kinases and is currently under clinical evaluation for the treatment of solid tumors. However, the effects of dasatinib on epithelial tumors are not fully understood. We show that concentrations of dasatinib that inhibit Src activity do not inhibit proliferation in 10 of 12 colon cancer cells lines. However, inhibition of integrin-dependent adhesion and migration by dasatinib correlated with inhibition of Src activity, suggesting that dasatinib may have anti-invasive or anti-metastatic activity and antiproliferative activity in epithelial tumors. Using phospho-specific antibodies, we show that inhibition of Src activity in colon cancer cell lines correlates with reduced phosphorylation of focal adhesion kinase and paxillin on specific Src-dependent phosphorylation sites. We have validated the use of phospho-specific antibodies against Src Tyr(419) and paxillin Tyr(118) as biomarkers of dasatinib activity in vivo. Colon carcinoma-bearing mice treated with dasatinib showed a decrease in both phospho-Src Tyr(419) and phospho-paxillin Tyr(118) in peripheral blood mononuclear cells, which correlated with inhibition of Src activity in the colon tumors. Thus, peripheral blood mononuclear cells may provide a useful surrogate tissue for biomarker studies with dasatinib using inhibition of Src Tyr(419) and paxillin Tyr(118) phosphorylation as read-outs of Src activity.
[show abstract] [hide abstract]
ABSTRACT: The non-receptor tyrosine kinases of the SRC family (SFK) play important roles in signal transduction induced by a large variety of extracellular stimuli, including growth factors and Integrins. When deregulated, SFKs show oncogenic activity, as originally reported for v-Src, the transforming product of the avian retrovirus RSV, and then, in many human cancers, particularly colorectal cancer (CRC). In CRC, SFK deregulation largely occurs in the absence of mutations of the corresponding genes, but the underlying molecular mechanisms involved are still unclear. In addition to a role in early tumor progression, SFK deregulation may also be important in advanced CRC, as suggested by the association between increased SFK activity and poor clinical outcome. However, SFK contribution to CRC metastasis formation is still poorly documented. Here, we will review recent findings that broaden our understanding of the mechanisms underlying SFK deregulation and signaling in advanced CRC. We will also discuss the implication of these observations for SFK-based therapy in metastatic CRC.American journal of cancer research. 01/2012; 2(4):357-71.
Biomarkers in Medicine 06/2012; 6(3):297-300. · 0.86 Impact Factor
[show abstract] [hide abstract]
ABSTRACT: Anti-VEGF antibody therapy with bevacizumab provides significant clinical benefit in patients with recurrent glioblastoma multiforme (GBM). Unfortunately, progression on bevacizumab therapy is often associated with a diffuse disease recurrence pattern, which limits subsequent therapeutic options. Therefore, there is an urgent need to understand bevacizumab's influence on glioma biology and block it's actions towards cell invasion.To explore the mechanism(s) of GBM cell invasion we have examined a panel of serially transplanted human GBM lines grown either in short-term culture, as xenografts in mouse flank, or injected orthotopically in mouse brain. Using an orthotopic xenograft model that exhibits increased invasiveness upon bevacizumab treatment, we also tested the effect of dasatinib, a broad spectrum SFK inhibitor, on bevacizumab-induced invasion.We show that 1) activation of Src family kinases (SFKs) is common in GBM, 2) the relative invasiveness of 17 serially transplanted GBM xenografts correlates strongly with p120 catenin phosphorylation at Y228, a Src kinase site, and 3) SFK activation assessed immunohistochemically in orthotopic xenografts, as well as the phosphorylation of downstream substrates occurs specifically at the invasive tumor edge. Further, we show that SFK signaling is markedly elevated at the invasive tumor front upon bevacizumab administration, and that dasatinib treatment effectively blocked the increased invasion induced by bevacizumab.Our data are consistent with the hypothesis that the increased invasiveness associated with anti-VEGF therapy is due to increased SFK signaling, and support testing the combination of dasatinib with bevacizumab in the clinic.PLoS ONE 01/2013; 8(2):e56505. · 4.09 Impact Factor