Thermostable Direct Hemolysin Downregulates Human Colon Carcinoma Cell Proliferation with the Involvement of E-Cadherin, and β-Catenin/Tcf-4 Signaling

BACKGROUND: Colon cancers are the frequent causes of cancer mortality worldwide. Recently bacterial toxins have received marked attention as promising approaches in the treatment of colon cancer. Thermostable direct hemolysin (TDH) secreted by Vibrio parahaemolyticus causes influx of extracellular calcium with the subsequent rise in intracellular calcium level in intestinal epithelial cells and it is known that calcium has antiproliferative activity against colon cancer. KEY RESULTS: In the present study it has been shown that TDH, a well-known traditional virulent factor inhibits proliferation of human colon carcinoma cells through the involvement of CaSR in its mechanism. TDH treatment does not induce DNA fragmentation, nor causes the release of lactate dehydrogenase. Therefore, apoptosis and cytotoxicity are not contributing to the TDH-mediated reduction of proliferation rate, and hence the reduction appears to be caused by decrease in cell proliferation. The elevation of E-cadherin, a cell adhesion molecule and suppression of β-catenin, a proto-oncogene have been observed in presence of CaSR agonists whereas reverse effect has been seen in presence of CaSR antagonist as well as si-RNA in TDH treated cells. TDH also triggers a significant reduction of Cyclin-D and cdk2, two important cell cycle regulatory proteins along with an up regulation of cell cycle inhibitory protein p27(Kip1) in presence of CaSR agonists. CONCLUSION: Therefore TDH can downregulate colonic carcinoma cell proliferation and involves CaSR in its mechanism of action. The downregulation occurs mainly through the involvement of E-cadherin-β-catenin mediated pathway and the inhibition of cell cycle regulators as well as upregulation of cell cycle inhibitors

Influence of the Physiological Age and Position of the Nodal Explants on Micropropagation of Field-Grown Dendrocalamus Strictus Nees

An efficient and reproducible protocol for plant regeneration through in vitro culture of Dendrocalamus strictus is reported. Murashige and Skoog\u27s (MS) basal medium supplemented with N6-benzyladenine and adenine sulphate resulted in high frequency of shoot organogenesis. Nodal explants obtained from mature field-grown culms of selected elite genotype of D. strictus produced multiple shoots. Percent regeneration and number of multiple shoots was directly correlated with the nodal segments from which explants were collected. Best regeneration response was noted from 1st and 2nd positions from the basal end of the secondary branches. The effect of physiological age of the donor plant on axillary shoot multiplication was studied for three consecutive years. The regeneration frequency declined with the maturity of the donor plant. Roots and monopodial type micro-rhizomes were induced in medium containing half strength of MS macrosalts supplemented with indole-3-butyric acid and regenerants were successfully transplanted in the soil. © 2004 Society for Biology and Biotechnology

Downregulation of Human Colon Carcinoma Cell (COLO-205) Proliferation Through PKG-MAP Kinase Mediated Signaling Cascade by E. Coli Heat Stable Enterotoxin (STa), a Potent Anti-Angiogenic and Anti-Metastatic Molecule

It was reported earlier that Escherichia coli heat stable enterotoxin (STa), a major causative agent of secretory diarrhea, can also inhibit the proliferation of colon carcinoma cells with the involvement of cGMP mediated calcium influx. In the present study it is shown that E. coli STa inhibits cell proliferation in the colonic carcinoma cell line COLO-205 by the PKG-ERK44/42 mediated signaling pathway. This enterotoxin negatively regulates cell proliferation by downregulating the activity of ERK44/42(MAPK) and subsequently the activity of a transcription regulatory protein cMyc. The antiproliferative effect of STa was reversed by LY83583, a guanylate cyclase (GC) inhibitor and KT5823, a PKG inhibitor. Thus suggesting the involvement of cGMP dependent protein kinase (PKG) in the downregulation of ERK44/42 and subsequent inactivation of cMyc activity. Moreover, it has been shown that a specific ERK44/42 inhibitor, PD98059, also inhibits cMyc activation and cell proliferation, which further confirms the involvement of ERK44/42 in the activation of cMyc. It is also shown that E. coli STa significantly inhibits the vascular endothelial growth factor (VEGF, a potent angiogenic factor) expression in COLO-205 cells and also downregulates vascular cell adhesion molecule-1 (VCAM-1, a potent metastatic factor) expression on the COLO-205 cell surface. So it is reported for the first time that E. coli STa inhibits the proliferation of the colonic carcinoma cell line COLO-205 by the PKG-ERK44/42 mediated pathway and it may have a role against the development of colon carcinoma. Copyright © 2007 John Wiley & Sons, Ltd

Downregulation of Human Colon Carcinoma Cell (COLO-205) Proliferation Through PKG-MAP Kinase Mediated Signaling Cascade by E. Coli Heat Stable Enterotoxin (STa), a Potent Anti-Angiogenic and Anti-Metastatic Molecule

It was reported earlier that Escherichia coli heat stable enterotoxin (STa), a major causative agent of secretory diarrhea, can also inhibit the proliferation of colon carcinoma cells with the involvement of cGMP mediated calcium influx. In the present study it is shown that E. coli STa inhibits cell proliferation in the colonic carcinoma cell line COLO-205 by the PKG-ERK44/42 mediated signaling pathway. This enterotoxin negatively regulates cell proliferation by downregulating the activity of ERK44/42(MAPK) and subsequently the activity of a transcription regulatory protein cMyc. The antiproliferative effect of STa was reversed by LY83583, a guanylate cyclase (GC) inhibitor and KT5823, a PKG inhibitor. Thus suggesting the involvement of cGMP dependent protein kinase (PKG) in the downregulation of ERK44/42 and subsequent inactivation of cMyc activity. Moreover, it has been shown that a specific ERK44/42 inhibitor, PD98059, also inhibits cMyc activation and cell proliferation, which further confirms the involvement of ERK44/42 in the activation of cMyc. It is also shown that E. coli STa significantly inhibits the vascular endothelial growth factor (VEGF, a potent angiogenic factor) expression in COLO-205 cells and also downregulates vascular cell adhesion molecule-1 (VCAM-1, a potent metastatic factor) expression on the COLO-205 cell surface. So it is reported for the first time that E. coli STa inhibits the proliferation of the colonic carcinoma cell line COLO-205 by the PKG-ERK44/42 mediated pathway and it may have a role against the development of colon carcinoma. Copyright © 2007 John Wiley & Sons, Ltd

Thermostable Direct Hemolysin Downregulates Human Colon Carcinoma Cell Proliferation With the Involvement of E-Cadherin, and β-Catenin/Tcf-4 Signaling

Background: Colon cancers are the frequent causes of cancer mortality worldwide. Recently bacterial toxins have received marked attention as promising approaches in the treatment of colon cancer. Thermostable direct hemolysin (TDH) secreted by Vibrio parahaemolyticus causes influx of extracellular calcium with the subsequent rise in intracellular calcium level in intestinal epithelial cells and it is known that calcium has antiproliferative activity against colon cancer. Key Results: In the present study it has been shown that TDH, a well-known traditional virulent factor inhibits proliferation of human colon carcinoma cells through the involvement of CaSR in its mechanism. TDH treatment does not induce DNA fragmentation, nor causes the release of lactate dehydrogenase. Therefore, apoptosis and cytotoxicity are not contributing to the TDH-mediated reduction of proliferation rate, and hence the reduction appears to be caused by decrease in cell proliferation. The elevation of E-cadherin, a cell adhesion molecule and suppression of β-catenin, a proto-oncogene have been observed in presence of CaSR agonists whereas reverse effect has been seen in presence of CaSR antagonist as well as si-RNA in TDH treated cells. TDH also triggers a significant reduction of Cyclin-D and cdk2, two important cell cycle regulatory proteins along with an up regulation of cell cycle inhibitory protein p27Kip1 in presence of CaSR agonists. Conclusion: Therefore TDH can downregulate colonic carcinoma cell proliferation and involves CaSR in its mechanism of action. The downregulation occurs mainly through the involvement of E-cadherin-β-catenin mediated pathway and the inhibition of cell cycle regulators as well as upregulation of cell cycle inhibitors. © 2011 Chowdhury et al

Role of Yersinia Enterocolitica Heat-Stable Enterotoxin (Y-STa) on Differential Regulation of Nuclear and Cytosolic Calcium Signaling in Rat Intestinal Epithelial Cells

The heat-stable enterotoxin (Y-STa) produced by the pathogenic strains of Yersinia enterocolitica is a causative agent of secretory diarrhea. We have reported earlier that Y-STa-induced inositol trisphosphate-mediated cytosolic calcium rise occurs in rat intestinal epithelial cells. In the present communication, the involvement of a nuclear calcium store in the action mechanism of Y-STa in rat intestinal epithelial cells has been shown. Calcium imaging with time series confocal microscopy shows that Y-STa stimulates both the nuclear and cytosolic calcium levels in rat intestinal epithelial cells where a rise in nuclear calcium precedes the cytosolic events. Moreover, Y-STa stimulates both cytosolic and nuclear inositol trisphosphate (IP3) levels in a time-dependent manner. Western blot and immunocytochemical analysis reveal a higher density of IP3 receptor type II in the nuclear membrane compared to the cytosol, which may be the cause of an early rise of the nuclear calcium level. Therefore, it is suggested that Y-STa regulates the nuclear and cytosolic calcium signals in a distinct temporal manner in rat intestinal epithelial cells. © 2008 Springer Science+Business Media B.V

Role of Yersinia Enterocolitica Heat-Stable Enterotoxin (Y-STa) on Differential Regulation of Nuclear and Cytosolic Calcium Signaling in Rat Intestinal Epithelial Cells

The heat-stable enterotoxin (Y-STa) produced by the pathogenic strains of Yersinia enterocolitica is a causative agent of secretory diarrhea. We have reported earlier that Y-STa-induced inositol trisphosphate-mediated cytosolic calcium rise occurs in rat intestinal epithelial cells. In the present communication, the involvement of a nuclear calcium store in the action mechanism of Y-STa in rat intestinal epithelial cells has been shown. Calcium imaging with time series confocal microscopy shows that Y-STa stimulates both the nuclear and cytosolic calcium levels in rat intestinal epithelial cells where a rise in nuclear calcium precedes the cytosolic events. Moreover, Y-STa stimulates both cytosolic and nuclear inositol trisphosphate (IP3) levels in a time-dependent manner. Western blot and immunocytochemical analysis reveal a higher density of IP3 receptor type II in the nuclear membrane compared to the cytosol, which may be the cause of an early rise of the nuclear calcium level. Therefore, it is suggested that Y-STa regulates the nuclear and cytosolic calcium signals in a distinct temporal manner in rat intestinal epithelial cells. © 2008 Springer Science+Business Media B.V

The Effects of Dexamethasone on Mitogen Activated Protein Kinase-14 Signaling in Diffuse Intrinsic Pontine Glioma (DIPG) Cells

Objective: Determine the effects of dexamethasone (DEX) on diffuse intrinsic pontine glioma (DIPG) cell behavior. Background: Patients with DIPG routinely receive DEX to treat vasogenic edema, but the direct effects on tumor growth and sensitivity to other therapies are unknown. Previous studies on glioblastoma cell lines have suggested that DEX interferes with nuclear translocation of p38α mitogen activated protein kinase-14 (MAPK-14), which may be required for cytokine production, cell mobility, and invasion, in addition to a metabolic shift from glycolysis to the pentose phosphate pathway. We tested the hypothesis that DEX prevents nuclear translocation of MAPK-14 in DIPG, resulting in metabolic reprogramming and decreased cell survival, migration, and colony formation. Design/Methods: We used immunocytochemistry to measure the nuclear translocation of total and phosphorylated MAPK-14 in cultured SU-DIPG-IV cells following treatment with DEX or vehicle. We also treated cells with DEX, with or without the clinically relevant chemotherapies panobinostat and imatinib on logarithmic dose curves, and measured proliferation rate, viability and apoptosis with combined assays of trypan blue exclusion and caspase 3/7 activation. Results: Treatment with DEX reduced nuclear localization of phosphorylated MAPK-14 in DIPG cells, but did not affect basal or chemotherapy-inhibited rates of cell proliferation, viability or apoptosis. Conclusions: DEX, a commonly prescribed medication for DIPG patients, decreased nuclear localization of phosphorylated MAPK-14 but had no apparent effects on basal or chemotherapy-inhibited rates of cell proliferation, viability or apoptosis. We are currently exploring the effects of DEX and MAPK-14 signaling on cell metabolism, migration, and colony formation

The Effects of Dexamethasone on Mitogen Activated Protein Kinase-14 Signaling in Diffuse Intrinsic Pontine Glioma (DIPG) Cells

Objective: Determine the effects of dexamethasone (DEX) on diffuse intrinsic pontine glioma (DIPG) cell behavior. Background: Patients with DIPG routinely receive DEX to treat vasogenic edema, but the direct effects on tumor growth and sensitivity to other therapies are unknown. Previous studies on glioblastoma cell lines have suggested that DEX interferes with nuclear translocation of p38α mitogen activated protein kinase-14 (MAPK-14), which may be required for cytokine production, cell mobility, and invasion, in addition to a metabolic shift from glycolysis to the pentose phosphate pathway. We tested the hypothesis that DEX prevents nuclear translocation of MAPK-14 in DIPG, resulting in metabolic reprogramming and decreased cell survival, migration, and colony formation. Design/Methods: We used immunocytochemistry to measure the nuclear translocation of total and phosphorylated MAPK-14 in cultured SU-DIPG-IV cells following treatment with DEX or vehicle. We also treated cells with DEX, with or without the clinically relevant chemotherapies panobinostat and imatinib on logarithmic dose curves, and measured proliferation rate, viability and apoptosis with combined assays of trypan blue exclusion and caspase 3/7 activation. Results: Treatment with DEX reduced nuclear localization of phosphorylated MAPK-14 in DIPG cells, but did not affect basal or chemotherapy-inhibited rates of cell proliferation, viability or apoptosis. Conclusions: DEX, a commonly prescribed medication for DIPG patients, decreased nuclear localization of phosphorylated MAPK-14 but had no apparent effects on basal or chemotherapy-inhibited rates of cell proliferation, viability or apoptosis. We are currently exploring the effects of DEX and MAPK-14 signaling on cell metabolism, migration, and colony formation

Purification and Characterization of an Immunogenic Outer Membrane Protein of Shigella Flexneri 2a

In the present study we purified 34 kDa major outer membrane protein (MOMP) of Shigella flexneri 2a for the first time, which was cross-reactive and antigenically conserved among Shigella spp. and the epitope was surface exposed on the intact bacterium. The purified antigen was found to be glycosylated, which aids in binding to macrophages and up-regulated the production of nitric oxide, granulocyte-colony stimulating factor and IL-12p70, indicating that the MOMP is immunogenic and has the ability to commence protective immune responses against intracellular pathogens, thereby it may be considered as a potential vaccine candidate. © 2009 Elsevier Ltd. All rights reserved