Expression of kinase-defective mutants of c-Src in human metastatic colon cancer cells decreases Bcl-xL and increases oxaliplatin- and Fas-induced apoptosis.
ABSTRACT Tumor resistance to current drugs prevents curative treatment of human colon cancer. A pressing need for effective, tumor-specific chemotherapies exists. The non-receptor-tyrosine kinase c-Src is overexpressed in >70% of human colon cancers and represents a tractable drug target. KM12L4A human metastatic colon cancer cells were stably transfected with two distinct kinase-defective mutants of c-src. Their response to oxaliplatin, to SN38, the active metabolite of irinotecan (drugs active in colon cancer), and to activation of the death receptor Fas was compared with vector control cells in terms of cell cycle arrest and apoptosis. Both kinase-defective forms of c-Src co-sensitized cells to apoptosis induced by oxaliplatin and Fas activation but not by SN38. Cells harboring kinase-defective forms of c-Src carrying function blocking point mutations in SH3 or SH2 domains were similarly sensitive to oxaliplatin, suggesting that reduction in kinase activity and not a Src SH2-SH3 scaffold function was responsible for the observed altered sensitivity. Oxaliplatin-induced apoptosis, potentiated by kinase-defective c-Src mutants, was dependent on activation of caspase 8 and associated with Bid cleavage. Each of the stable cell lines in which kinase-defective mutants of c-Src were expressed had reduced levels of Bcl-x(L.) However, inhibition of c-Src kinase activity by PP2 in vector control cells did not alter the oxaliplatin response over 72 h nor did it reduce Bcl-x(L) levels. The data suggest that longer term suppression of Src kinase activity may be required to lower Bcl-x(L) levels and sensitize colon cancer cells to oxaliplatin-induced apoptosis.
- SourceAvailable from: Ali Mobasheri[show abstract] [hide abstract]
ABSTRACT: Development of treatment resistance and adverse toxicity associated with classical chemotherapeutic agents highlights the need for safer and effective therapeutic approaches. Herein, we examined the effectiveness of a combination treatment regimen of 5-fluorouracil (5-FU) and curcumin in colorectal cancer (CRC) cells. Wild type HCT116 cells and HCT116+ch3 cells (complemented with chromosome 3) were treated with curcumin and 5-FU in a time- and dose-dependent manner and evaluated by cell proliferation assays, DAPI staining, transmission electron microscopy, cell cycle analysis and immunoblotting for key signaling proteins. The individual IC of curcumin and 5-FU were approximately 20 µM and 5 µM in HCT116 cells and 5 µM and 1 µM in HCT116+ch3 cells, respectively (). Pretreatment with curcumin significantly reduced survival in both cells; HCT116+ch3 cells were considerably more sensitive to treatment with curcumin and/or 5-FU than wild-type HCT116 cells. The IC values for combination treatment were approximately 5 µM and 1 µM in HCT116 and 5 µM and 0.1 µM in HCT116+ch3, respectively (). Curcumin induced apoptosis in both cells by inducing mitochondrial degeneration and cytochrome c release. Cell cycle analysis revealed that the anti-proliferative effect of curcumin and/or 5-FU was preceded by accumulation of CRC cells in the S cell cycle phase and induction of apoptosis. Curcumin potentiated 5-FU-induced expression or cleavage of pro-apoptotic proteins (caspase-8, -9, -3, PARP and Bax), and down-regulated anti-apoptotic (Bcl-xL) and proliferative (cyclin D1) proteins. Although 5-FU activated NF-κB/PI-3K/Src pathway in CRC cells, this was down-regulated by curcumin treatment through inhibition of IκBα kinase activation and IκBα phosphorylation. Combining curcumin with conventional chemotherapeutic agents such as 5-FU could provide more effective treatment strategies against chemoresistant colon cancer cells. The mechanisms involved may be mediated via NF-κB/PI-3K/Src pathways and NF-κB regulated gene products.PLoS ONE 01/2013; 8(2):e57218. · 3.73 Impact Factor
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ABSTRACT: Elongation factor-2 kinase (eEF-2 kinase, also known as calmodulin-dependent protein kinase III), is a unique calcium/calmodulin-dependent enzyme that inhibits protein synthesis by phosphorylating and inactivating elongation factor-2 (eEF-2). We previously reported that expression/activity of eEF-2 kinase was up-regulated in several types of malignancies including Gliomas, and was associated with response of tumor cells to certain therapeutic stress. In the current study, we sought to determine whether eEF-2 kinase expression affected sensitivity of glioma cells to treatment with tumor the necrosis factor-related apoptosis-inducing ligand (TRAIL), a targeted therapy able to induce apoptosis in cancer cells but causes no toxicity in most normal cells. We found that inhibition of eEF-2 kinase by RNA interference (RNAi) or by a pharmacological inhibitor (NH125) enhanced TRAIL-induced apoptosis in the human glioma cells, as evidenced by an increase in apoptosis in the tumor cells treated with eEF-2 kinase siRNA or the eEF-2 kinase inhibitor. We further demonstrated that sensitization of tumor cells to TRAIL was accompanied by a down-regulation of the anti-apoptotic protein, Bcl-xL, and that overexpression of Bcl-xL could abrogate the sensitizing effect of inhibiting eEF-2 kinase on TRAIL. The results of this study may help devise a new therapeutic strategy for enhancing the efficacy of TRAIL against malignant glioma by targeting eEF-2 kinase.Biochemical and Biophysical Research Communications 09/2011; 414(1):129-34. · 2.41 Impact Factor
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ABSTRACT: PURPOSE: The aim of this study is to investigate whether Dasatinib, a Src inhibitor, has the synergistic effect with oxaliplatin in treating gastric cancer cells. METHODS: The baseline levels of total Src and p-Src in 10 human gastric cancer cell lines and gastric mucosa epithelial cell line GES-1 were detected by Western blot (WB). The changes of Src and p-Src expression after oxaliplatin exposure were evaluated by WB. The combination indices and clonogenic assay were used to evaluate the synergistic effects of dasatinib with oxaliplatin on cell growth and proliferation in vitro. Gastric cancer xenografts in nude mice were established and treated by oxaliplatin with or without dasatinib. The tumor growth curves were calculated and the impacts of different treatment on the tumor proliferation and src protein expression in gastric cancer xenografts were determined by immunohistochemistry staining and WB. RESULTS: The different levels of Src expression in gastric cancer cells were related with their different sensitivity to oxaliplatin. The expression of p-Src, but not total Src, was elevated after oxaliplatin exposure both in vitro and in vivo. Dasatinib could dramatically inhibit p-Src expression, and combination indices demonstrated that dasatinib and oxaliplatin were synergistic in inhibiting gastric cancer cell growth. Dasatinib plus oxaliplatin were more effective in inhibiting clone formation than oxaliplatin or dasatinib monotherapy in clonogenic assay. The tumor volume and tumor weight of xenografts were significantly lower in doublet treatment group than those in single-agent treatment groups. CONCLUSIONS: Dasatinib plays synergistic role with oxaliplatin in inhibiting gastric cancer cell growth both in vitro and in vivo, via inhibiting Src activity stimulated by oxaliplatin.Cancer Chemotherapy and Pharmacology 05/2013; · 2.80 Impact Factor