Expression of kinase-defective mutants of c-Src in human metastatic colon cancer cells decreases Bcl-x(L) 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.
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- "The tyrosine kinase Src, that regulates cellular signaling pathways, has been linked with different stages of tumor progression such as CRC metastasis ,  and implicated in treatment resistance to chemotherapeutic agents . Indeed, it has been reported that suppression of Src signaling sensitizes tumor cells to chemotherapies , . In agreement with these findings, we clearly demonstrate that curcumin alone or in combination with 5-FU markedly decreases Src expression in a dose-dependent manner in HCT116 cells, suggesting the inhibition of Src activity by curcumin imparts higher sensitivity to 5-FU. "
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 02/2013; 8(2):e57218. DOI:10.1371/journal.pone.0057218 · 3.23 Impact Factor
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- "More recently, Src kinase has been implicated in drug resistance  and is shown to be a modulator of sensitivity to oxaliplatin . Pre-clinical evidence indicates that inhibition of Src renders the cancer cells susceptible to chemotherapies [44-46]. In light of these findings, investigations are being carried out to develop dasatinib, a highly potent Src inhibitor, as an adjuvant therapy for treatment of cancer along with inhibition of recurrence. "
ABSTRACT: ABSTRACT: Metastatic colorectal cancer remains a serious health concern with poor patient survival. Although 5-Fluorouracil (5-FU) or 5-FU plus oxaliplatin (FOLFOX) is the standard therapy for colorectal cancer, it has met with limited success. Recurrence of the tumor after chemotherapy could partly be explained by the enrichment of the chemo-resistant sub-population of cancer stem cells (CSCs) that possess the ability for self-renewal and differentiation into different lineages in the tumor. Therefore development of therapeutic strategies that target CSCs for successful treatment of this malignancy is warranted. The current investigation was undertaken to examine the effectiveness of the combination therapy of dasatinib (a Src inhibitor) and curcumin (a dietary agent with pleiotropic effect) in inhibiting the growth and other properties of carcinogenesis of chemo-resistant colon cancer cells that are enriched in CSCs sub-population. Remnants of spontaneous adenomas from APCMin +/- mice treated with dasatinib and/or curcumin were analyzed for several cancer stem cell markers (ALDH, CD44, CD133 and CD166). Human colon cancer cells HCT-116 (p53 wild type; K-ras mutant) and HT-29 (p53 mutant; K-ras wild type) were used to generate FOLFOX resistant (referred to as CR) cells. The effectiveness of the combination therapy in inhibiting growth, invasive potential and stemness was examined in colon cancer CR cells. The residual tumors from APCMin +/- mice treated with dasatinib and/or curcumin showed 80-90% decrease in the expression of the CSC markers ALDH, CD44, CD133, CD166. The colon cancer CR cells showed a higher expression of CSCs markers, cell invasion potential and ability to form colonospheres, compared to the corresponding parental cells. The combination therapy of dasatinib and curcumin demonstrated synergistic interactions in CR HCT-116 and CR HT-29 cells, as determined by Calcusyn analysis. The combinatorial therapy inhibited cellular growth, invasion and colonosphere formation and also reduced CSC population as evidenced by the decreased expression of CSC specific markers: CD133, CD44, CD166 and ALDH. Our data suggest that the combination therapy of dasatinib and curcumin may be a therapeutic strategy for re-emergence of chemo-resistant colon cancer by targeting CSC sub-population.Journal of Molecular Signaling 07/2011; 6:7. DOI:10.1186/1750-2187-6-7
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- "Irinotecan is a prodrug that, in presence of hepatic or gastrointestinal carboxylesterase, is metabolized to its active form 7-ethyl-10-hydroxy camptothecin (SN-38). Irinotecan and SN-38 bind to the topoisomerase DNA complex preventing religation of the singlestrand breaks in the DNA molecule and causing DNA double strand breaks, which can lead to apoptosis (Catley et al., 2004; Griffiths et al., 2004). The dose-limiting toxic effects of irinotecan are myelosuppression and diarrhea. "
ABSTRACT: The recent introduction of new drugs such as capecitabine, irinotecan, and oxaliplatinum has greatly improved the clinical outcome of patients with advanced/metastatic colorectal cancer. Nevertheless, some patients may suffer from the adverse drug reactions which will probably be the main cause of chemotherapy failure. The goal of pharmacogenomics is to find correlations between therapeutic responses to drugs and the genetic profiles of patients; the different responses to a particular drug are due, in fact, not only to the specific clinico-pathological features of the patient or to environmental factors, but also to the ethnic origins and the particular individual's genetic profile. Genes which codify for the metabolism enzymes, receptor proteins, or protein targets of chemotherapy agents often present various genetic polymorphisms. The main aim of this review is to provide an overview of the known polymorphisms present in the genes which codify for factors (thymidylate synthase dihydropyrimidine dehydrogenase, uridine diphosphate (UDP)-glucuronosyl-transferase 1A1, enzymes implicated in DNA repair) involved in the action mechanisms of the drugs now utilized in chemotherapeutic treatment of colorectal carcinoma, such as fluoropyrimidines, irinotecan, and platinum agents.Journal of Cellular Physiology 09/2005; 204(3):742-9. DOI:10.1002/jcp.20357 · 3.84 Impact Factor