LY294002 potentiates the anti-cancer effect of oxaliplatin for gastric cancer via death receptor pathway

AIM:To examine the effects of combined treatment of oxaliplatin and phosphatidylinositol 3'-kinase inhibitor,2-(4-morpholinyl) -8-phenyl-4H-1-benzopyran-4-one(LY294002) for gastric cancer. METHODS:Cell viability was evaluated by 3-(4,5-dimethylthiazol-2-yl) -2,5-diphenyltetrazolium bromide assay.Apoptotic cells were detected by flow cytometric analysis and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling assay.Western blotting and immuno-precipitation were used to examine protein expression and recruitment,respectively.Nuclear factorκB(NFκB) binding activities were investigated using electrophoretic mobility shift assay.Nude mice were used to investigate tumor growth. RESULTS:Treatment with combined oxaliplatin and LY294002 resulted in increased cell growth inhibi-tion and cell apoptosis in vitro,and increased tumor growth inhibition and cell death in the tumor mass in vivo.In MKN45 and AGS cells,oxaliplatin treatment promoted both protein kinase B(Akt) and NFκB activation,while pretreatment with LY294002 significantly attenuated oxaliplatin-induced Akt activity and NFκB binding.LY294002 promoted oxaliplatin-induced Fas ligand(FasL) expression,Fas-associated death domain protein recruitment,caspase-8,Bid,and caspase-3 activation,and the short form of cellular caspase-8/FLICEinhibitory protein(c-FLIPS) inhibition.In vivo,LY294002 inhibited oxaliplatin-induced activation of Akt and NFκB,and increased oxaliplatin-induced expression of FasL,inhibition of c-FLIPS,and activation of caspase-8,Bid,and caspase-3. CONCLUSION:Combination of oxaliplatin and LY294002 was therapeutically promising for gastric cancer treatment.The enhanced sensitivity of the combined treatment was associated with the activation of the death receptor pathway.

Xanthotoxin induces apoptosis in SGC-7901 cells through death receptor pathway

Objective： To investigate the effects of xanthotoxin from Apiaceae medicinal plants on cell proliferation and apoptosis, and explore its mechanism of action against human gastric carcinoma SGC-7901 cells in vitro.Methods： SGC-7901, HepG-2, MCF-7, and A549 cells were treated with different concentrations of xanthotoxin（10, 20, 60, 80, 100, 120, 140, and 160 μg/mL） for 48 h, and the cell viability（IC50） was determined by MTT assay; Xanthotoxin-induced apoptosis in cells was observed by using Hoechst 33258 Staining Kit and Annexin V-FITC Apoptosis Detection Kit; Flow cytometry was used to detect apoptosis related proteins of Fas/FasL, Bid, and DR5/TRAIL proteins in human gastric carcinoma SGC-7901 cells after being treated by xanthotoxin; The influence of xanthotoxin on Caspase-8 protein expression in the cells was determined by Flouormetric Assay Kit.Results： Xanthotoxin obviously inhibited SGC-7901, HepG-2, MCF-7, and A549 cells proliferation, and its inhibition was in a concentration-dependent manner; flow cytometry results showed that in a certain concentration range, xanthotoxin can increase the expression levels of Fas/FasL and DR5/TRAIL proteins in a concentration-dependence manner. The content of Bid protein in cells was increased, and it showed concentration-dependence.Conclusion： Xanthotoxin may induce SGC-7901 cells apoptosis in a certain concentration range through the Fas/FasL protein mediated death receptor pathway, or by DR5/TRAIL mediated death receptor pathway, and increase the expression level of death receptor protein, activation Caspase-8, activating downstream effect factor, inducing cell apoptosis, or activate Caspase-8 cutting activate protein Bid, and then enter the mitochondrial pathway, induction of apoptosis.

Environmental hypoxia induces apoptosis in large yellow croaker Larimichthys crocea via both intrinsic and extrinsic pathways

Hypoxia has become an unfavorable factor affecting the sustainable development of the large yellow croaker Larimichthys crocea,an economically important mariculture fish in China.Apoptosis is a consequence of hypoxia on fish.However,the effects of hypoxia stress on apoptosis in L.crocea remain largely unknown.We investigated the effect of environmental hypoxia on apoptosis in L.crocea.Results show that hypoxia induced apoptosis in L.crocea both in vivo and in vitro.The mitochondrial membrane potential was significantly reduced in large yellow croaker fry(LYCF)cells.The expression levels of Bcell lymphoma/leukemia-2(Bcl-2)m RNA and protein were also significantly decreased in the liver and LYCF cells during 96 h and 48 h of hypoxia stress,respectively,whereas the expression level of Bcl-2 associated X(Bax)mRNA,Casp3 mRNA,and activity of caspase-3/7/9 were significantly increased,indicating that hypoxia induced caspase-dependent intrinsic apoptosis in L.crocea.The expression level of the apoptosis-inducing factor(AIF)protein was significantly increased in the liver and LYCF cells.The level of AIF protein was significantly decreased in the cytoplasm but increased in the nuclei of L.crocea,demonstrating that hypoxia induced the AIF-mediated caspase-independent intrinsic apoptosis.In addition,the activity of caspase-8 was significantly increased,indicating that hypoxia stress induced extrinsic apoptosis in L.crocea.Therefore,hypoxia induced apoptosis in L.crocea through both the intrinsic and extrinsic pathways.The present study accumulated basic biological information to help elucidate the mechanism of hypoxia response in marine fish.

Mechanisms involved in the cytotoxic effects of berberine on human colon cancer HCT-8 cells

Berberine,a constituent of some traditional Chinese medicinal plants,has been reported to have cytotoxicity effects on different human cancer cell lines.There is no available information about the effects and mechanism of action of berberine on human colon cancer cell line HCT-8.In this paper,the cytotoxicity of berberine on HCT-8 cancer cells was investigated by MTT assay,fluorescence microscopy and flow cytometry analysis.Our data revealed that berberine could significantly inhibit the growth of HCT-8 cells in a dose-and time-dependent manner.Morphology of apoptotic cells was studied with acridine orange/ethidium bromide staining.The concentrations of lactate dehydrogenase and both acid and alkaline phos-phatases were significantly increased in cell supernatants after berberine treatment,suggesting cell death.Furthermore,flow cytometry analysis showed that berberine could arrest HCT-8 cells at S phase in a time-dependent manner.To further investigate the apoptotic molecular mechanism,reverse transcription-poly-merase chain reaction(RT-PCR)and western blotting methods were used.The up-regulated mRNA and/or protein expressions of Fas,FasL,TNF-α,caspase-3 and down-regulation of pro-caspase-3 suggest that the death receptor pathway may be involved in the apoptotic pathway induced by berberine.Decrease of Bcl-2 and increase of Bax in mRNA and/or protein expressions showed that the Bcl-2 family proteins were involved in berberine-induced apoptosis.We also found that berberine-induced apoptosis was associated with an up-regulated expressions of p53 and prohibitin(PHB),and decreased vimentin expression.These results suggest that berberine can suppress cell growth and reduce cell survival by arresting the cell-cycle and by inducing apoptosis of HCT-8 cells.

Iso-suillin from Suillus flavus Induces Apoptosis in Human Small Cell Lung Cancer H446 Cell Line

Background： The suillin isoform iso-suillin is a natural substance isolated from a petroleum ether extract of the fruiting bodies of the mushroom Suillus.flavus. Previous studies have found its inhibition effect on some cancer cells, and we aimed to study its effects on human small cell lung cancer H446 cell line. Methods： Cell viability was measured by 3-（4,5-dimethyl-2-thiazolyl）-2,5-diphenyl-2-H-tetrazolium bromide assay. Cellular morphological changes （apoptosis and necrosis） were evaluated using an electron microscope and Hoechst 33258 staining detected by the inverted microscope. Flow cytometry was used to detect cell apoptosis, cell cycle distribution, and mitochondrial membrane potential. Protein expression was determined by Western blotting analysis. Results： Here, we describe the ability of iso-suillin to inhibit the growth of H446 cells in time- and dose-dependent way. Iso-suillin had no obvious impact on normal human lymphocyte proliferation at low concentrations （9.09, 18.17, or 36.35 μmol/L） but promoted lymphocyte proliferation at a high concentration （72.70 μmol/L）. After treatment of different concentrations of iso-suillin （6.82, 13.63, or 20.45 μmol/L）, the apoptosis rate of H446 cells increased with increasing concentrations of iso-suillin （16.70%, 35.54%, and 49.20%, respectively, all P 〈 0.05 compared with the control）, and the expression of related apoptotic proteins in the mitochondrial pathway including cytochrome c and caspase-9 were up-regulated compared with the control （all P 〈 0.05）. On the contrary, Bcl-2/Bax ratio was down-regulated compared with the control. Besides, the expression of pro-apoptotic proteins in the death receptor apoptosis pathway, including Fas-associating protein with a novel death domain and caspase-8, and the expression of caspase-3, a downstream regulatory protein of apoptosis, were also increased compared with the control （all P 〈 0.05）. lnhibitors of caspase-9 and caspase-8 reversed the apoptosis process in H446 cells to varying degrees. Conclusions： These results suggest that iso-suillin could induce H446 cell apoptosis through the mitochondrial pathway and the death-receptor pathway. Therefore, iso-suillin might have a potential application as a novel drug for lung cancer treatment.

Drug and apoptosis resistance in cancer stem cells: a puzzle with many pieces

Resistance to anticancer agents and apoptosis results in cancer relapse and is associated with cancer mortality.Substantial data have provided convincing evidence establishing that human cancers emerge from cancer stemcells (CSCs), which display self-renewal and are resistant to anticancer drugs, radiation, and apoptosis, andexpress enhanced epithelial to mesenchymal progression. CSCs represent a heterogeneous tumor cell populationand lack specific cellular targets, which makes it a great challenge to target and eradicate them. Similarly, theirclose relationship with the tumor microenvironment creates greater complexity in developing novel treatmentstrategies targeting CSCs. Several mechanisms participate in the drug and apoptosis resistance phenotype in CSCsin various cancers. These include enhanced expression of ATP-binding cassette membrane transporters, activationof various cytoprotective and survival signaling pathways, dysregulation of stemness signaling pathways, aberrantDNA repair mechanisms, increased quiescence, autophagy, increased immune evasion, deficiency ofmitochondrial-mediated apoptosis, upregulation of anti-apoptotic proteins including c-FLIP [cellular FLICE (FADDlikeIL-1β-converting enzyme)-inhibitory protein], Bcl-2 family members, inhibitors of apoptosis proteins, andPI3K/AKT signaling. Studying such mechanisms not only provides mechanistic insights into these cells that areunresponsive to drugs, but may lead to the development of targeted and effective therapeutics to eradicate CSCs.Several studies have identified promising strategies to target CSCs. These emerging strategies may help targetCSC-associated drug resistance and metastasis in clinical settings. This article will review the CSCs drug and apoptosis resistance mechanisms and how to target CSCs.