Upregulated CD133 expression in tumorigenesis of colon cancer cells

AIM: To analyze the upregulated CD133 expression in tumorigenesis of primary colon cancer cells. METHODS: Upregulated CD133 expression in tumorigenesis of colorectal cancer cell lines (Lovo, Colo205, Caco-2, HCT116 and SW620) was analyzed by flow cytometry. Human colon cancer tissue samples were stained with anti-human CD133. SW620 cells were sorted according to the CD133 expression level measured by fluorescence-activated cell sorting. Spheroids of colorectal cancer cells were cultured with the hanging drop. Expression of CD133 and Lgr5 in spheroids of colorectal cancer cells and monolayer culture was detected by RT-qPCR. Spheroids of colorectal cancer cells were analyzed using anti-human CD133 with immunohistochemical staining. RESULTS: CD133 antigen was expressed in colorectal cancer cell lines (Lovo, Colo205, Caco-2, HCT116 and SW620) as well as in primary and metastatic human colon cancer tissues. However, the CD133 was differently expressed in these cell lines and tissues. The expression levels of CD133 and Lgr5 were significantly higher in spheroids of parental, CD133hi and CD133-cells than in their monolayer culture at the mRNA level (P < 0.05). Immunohistochemical staining of spheroids of CD133-cells showed that CD133 was highly expressed in colorectal cancer cell lines. CONCLUSION: Upregulated CD133 expression plays a role in tumorigenesis colorectal cancer cells, which may promote the expression of other critical genes that can drive tumorigenesis.

Therapeutic implications of colon cancer stem cells

Colorectal cancer is the second most common cause of cancer-related death in many industrialized countries and is characterized by a heterogenic pool of cells with distinct differentiation patterns. Recently, the concept that cancer might arise from a rare population of cells with stem cell-like properties has received support with regard to several solid tumors, including colorectal cancer. According to the cancer stem cell hypothesis, cancer can be considered a disease in which mutations either convert normal stem cells into aberrant counterparts or cause a more differentiated cell to revert toward a stem cell-like behaviour; either way these cells are thought to be responsible for tumor generation and propagation. The statement that only a subset of cells drives tumor formation has major implications for the development of new targeted therapeutic strategies aimed at eradicating the tumor stem cell population. This review will focus on the biology of normal and malignant colonic stem cells, which might contribute to our understanding of the mechanisms responsible for tumor development and resistance to therapy.

Anti-cancer effect of ethylacetate fraction from Orostachys japonicus on HT-29 human colon cancer cells by induction of apoptosis through caspase-dependent signaling pathway

Objective: To investigate the anti-colon cancer effects of ethylacetate fraction from Orostachys japonicus(0. japonicus) on HT-29 cancer cells. Methods: The viability of HT-29 cells was assayed by the 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2 H-tetrazolium(MTS) method. Apoptosis induction and cell cycle inhibition were confirmed by fluorescein isothiocyanate and propidium iodide staining using flow cytometry.Morphological changes in the nucleus were observed, using a fluorescence microscope with4',6-diamidino-2-phenylindole(DAPI) nuclear staining. The expression levels of the upstream and downstream proteins involved in the anti-cancer mechanism were confirmed by Western blotting. Results: After treating HT-29 cells with different concentrations of ethylacetate fraction from O. japonicus, the viability of cells decreased in a concentration-dependent manner,while apoptosis induction and apoptotic body formation increased. Cell cycle analysis showed that the arrest occurred at the sub-G_1 and S phase. Among the upstream and downstream proteins involved in anti-cancer activity, the level of B cell lymphoma-2 decreased, and the bcl-2-associated x protein increased. The level of pro-caspase-3, pro-caspase-8, and pro-caspase-9 decreased, while the level of cleaved-caspase-3, cleaved-caspase-8, and cleaved-caspase-9 increased. Moreover, the phosphorylation, that is, activation of extracellular signal regulated kinase 1/2, Jun-N-terminal kinase, and p38 increased. Conclusions: Combining the above results, it is thought that the survival of HT-29 cells is suppressed by ethylacetate fraction from0. japonicus through mitochondrial regulation-induced caspase cascade activation, induction of apoptosis and cell cycle arrest.

Intestinal stem cells and the colorectal cancer microenvironment

Colorectal cancer (CRC) remains a highly fatal condition in part due to its resilience to treatment and its propensity to spread beyond the site of primary occurrence. One possible avenue for cancer to escape eradication is via stem-like cancer cells that, through phenotypic heterogeneity, are more resilient than other tumor constituents and are key contributors to cancer growth and metastasis. These proliferative tumor cells are theorized to possess many properties akin to normal intestinal stem cells. Not only do these CRC &#x0201c;stem&#x0201d; cells demonstrate similar restorative ability, they also share many cell pathways and surface markers in common, as well as respond to the same key niche stimuli. With the improvement of techniques for epithelial stem cell identification, our understanding of CRC behavior is also evolving. Emerging evidence about cellular plasticity and epithelial mesenchymal transition are shedding light onto metastatic CRC processes and are also challenging fundamental concepts about unidirectional epithelial proliferation. This review aims to reappraise evidence supporting the existence and behavior of CRC stem cells, their relationship to normal stem cells, and their possible dependence on the stem cell niche.

Testosterone induced apoptosis in colon cancer cells is regulated by PI3K/Racl signaling

Recently, it has been reported that testosterone membrane signaling regulates actin reorganization and induces pro-apoptotic responses in colon tumor cells. In the present study the membrane androgen receptors （mARs）-induced activation of Rac I GTPase and the involvement of PI3K/Racl signaling in controlling the apoptotic responses in testosterone treated Caco2 colon cancer cells has been analyzed. In line with previous findings, activation of mAR by testosterone conjugates triggered early and transient actin reorganization as indicated by the significant decrease of the G/Total actin ratio after 15- and 30-min treatment of the cells. Interestingly, stimulation of mAR rapidly activated the Racl GTPase. This effect was evident after 15 min and persisted for at least 24 h. Testosterone induced Rac I activation was fully blocked in Caco2 cells pre-treated with the PI3K inhibitor wortmannin, indicating that Racl signaling is acting downstream of the PI3K pathway. Remarkably, when cells were pre-treated with wortmannin that blocks the PI3K/Racl signaling, apoptotic response was almost fully inhibited. These finding suggest that Racl activation, triggering actin redistribution, is involved in testosterone induced pro-apoptotic responses governed by mAR activation and emphasize the regulatory role of PI3K/Racl signaling in colon tumors.

Growth inhibition of colon cancer cells by compounds affecting AMPK activity

AIM:To determine if other molecules reported to modulate AMP-dependent protein kinase(AMPK)activ-ity would have effects resembling those of metformin and phenformin on colon cancer cell proliferation and metabolism.METHODS:Studies were performed with four hu-man colon cancer cell lines,Caco-2,HCT116,HT29 and SW1116.The compounds that were studied included A-769662,5-aminoimidazole-4-carboxamide-1-ribofu-ranoside,butyrate,(-)-epigallocatechin gallate(EGCG),KU-55933,quercetin,resveratrol and salicylates.The parameters that were measured were cell proliferation and viability,glucose uptake,lactate production and acidification of the incubation medium.RESULTS:Investigations with several molecules that have been reported to be associated with AMPK activa-tion(A-769662,5-aminoimidazole-4-carboxamide-1-b-D-ribofuranoside,EGCG,KU-55933,quercetin,resve-ratrol and salicylates)or AMPK inhibition(compound C)failed to reveal increased medium acidification and increased glucose uptake in colon cancer cells as previ-ously established with metformin and phenformin.The only exception was 5-aminosalicylic acid with which there were apparently lower glucose levels in the me-dium after incubation for 72 h.Further study in the absence of cells revealed that the effect was an artifact due to inhibition of the enzyme-linked glucose assay.The compounds were studied at concentrations that inhibited cell proliferation.CONCLUSION:It was concluded that treatment with several agents that can affect AMPK activity resulted in the inhibition of the proliferation of colon cancer cells under conditions in which glucose metabolism is not enhanced,in contrast to the effect of biguanides.

Effects of silkworm pupa protein on apoptosis and energy metabolism in human colon cancer DLD-1 cells

Objective:To investigate the effects of silkworm pupa(Bombyx mori) protein(SPP) on cell proliferation,apoptosis and energy metabolism in human colon cancer cells DLD-1.Methods:CCK-8 was used to detect cell proliferation rate after 72 h of cell culture for the control group(normal cultured DLD-1 cells) and SPP dose groups;Annexin-V/PI was applied to observe cell apoptosis;XFe24 Extracellular Flux Analyzer was used to detect cell mitochondrial respiratory function and glycolytic function.Results:Comparing with the control,SPP significantly inhibited the proliferation of DLD-1 cells with all the dosage tested(P <0.01);flow cytometry showed that SPP significantly promoted apoptosis(P<0.05).Additionally,SPP could significantly inhibited mitochondrial metabolism and glycolysis of DLD-1 cells and decreased cell energy metabolism in all groups treated with different doses.Conclusion:SPP can cause oxidative damage,promote apoptosis,and reduce mitochondrial respiratory and glycolysis rate in colon cancer DLD-1 cells,which reveals that SPP has the potential to serve as the anti-cancer drugs in the future,but further experimental evidence is needed.

Targeting BCRP/ABCG2 by RNA Interference Enhances the Chemotherapy Sensitivity of Human Colon Cancer Side Population Cells

Relapse and metastasis are frequent in colon cancer and may be linked to stem cell characteristics.This study isolated side population（SP） cells from a colon cancer cell line（Colo-320） and examined their self-renewal and differentiation abilities.Compared to non-SP（NSP） cells,SP colon cancer cells were more tumorigenic in vivo and exhibited more invasive characteristics and a greater ability to form colonies.Additionally,more cells were in G0/G1 phase and more highly expressed the multidrug resistance protein BCRP/ABCG2.We achieved enhanced chemotherapy sensitivity by transfecting SP cells with a hairpin-like,small interfering RNA（si RNA） eukaryotic expression plasmid targeting BCRP/ABCG2.

Identification of integrin β6 gene promoter and analysis of its transcription regulation in colon cancer cells

BACKGROUND The integrinβ6 gene,which is expressed in epithelial cancer,plays a pivotal role in various aspects of cancer progression.The present research for integrinβ6 regulation mainly focuses on the post-transcription and translation related regulation mechanism and its role in tumorigenesis.The mechanisms of how the integrinβ6 gene is regulated transcriptionally,and the promoter and transcription factors responsible for basic transcription of integrinβ6 gene remain unknown.AIM To clone and characterize the integrinβ6 promoter.METHODS Software analysis was used to predict the region of integrinβ6 promoter.Luciferase reporter plasmids,which contained the integrinβ6 promoter,were constructed.Element deletion analysis was performed to identify the location of core promoter and binding sites for transcription factors.RESULTS The regulatory elements for the transcription of the integrinβ6 gene were located between-286 and-85 and contained binding sites for transcription factors such as STAT3 and Ets-1.CONCLUSION For the first time,we found the region ofβ6 core promoter and demonstrated the binding sites for transcription factors such as Ets-1 and STAT3,which are important for integrinβ6 promoter transcription activity.These findings are important for investigating the mechanism of integrinβ6 activation in cancer progression.

Epigenetic modification regulates both expression of tumor-associated genes and cell cycle progressing in human colon cancer cell lines: Colo-320 and SW1116

The aim of this study is to assess the effects of DNA methylation and historic acetylation, alone or in combination, on the expression of several tumor-associated genes and cell cycle progression in two established human colon cancer cell lines: Colo-320 and SW1116. Treatments with 5-aza-2'-deoxycytidine (5-aza-dC) and trichostatin A, alone or in combination, were applied respectively. The methylation status of the CDKN2A promoter was determined by methyla-tion-specific PCR, and the acetylated status of the histones associated with the p21WAF1 and CDKN2A genes was examined by chromatin immunoprecipitation. The expression of the CDKN2A, p21WAF1, p53, p73, APC, c-myc, c-Ki-ras and survivin genes was detected by real-time RT-PCR and RT-PCR. The cell cycle profile was established by flow cytometry. We found that along with the demethylation of the CDKN2A gene promoter in both cell lines induced by 5-aza-dC alone or in combination with TSA, the expression of both CDKN2A and APC genes increased. The treatment of TSA or sodium butyrate up-regulated the transcription of p21WAF1 significantly by inducing the acetylation of histones H4 and H3, but failed to alter the acetylation level of CDKN2A-associated histones. No changes in transcription of p53, p73, c-myc, c-Ki-ras and survivin genes were observed. In addition, TSA or sodium butyrate was shown to arrest cells at the G1 phase. However, 5-aza-dC was not able to affect the cell cycle progression. In conclusion, regulation by epigenetic modification of the transcription of tumor-associated genes and the cell cycle progression in both human colon cancer cell lines Colo-320 and SW1116 is gene-specific.

Growth hormone releasing peptide 2 reverses anorexia associated with chemotherapy with 5-fluoruracil in colon cancer cell-bearing mice

The cancer-associated anorexia-cachexia syndrome is observed in 80% of patients with advanced-stage cancer, and is one of the major obstacles in chemo- therapy. Ghrelin is a orexigenic hormone that has been proposed to prevent anorexia. Aim of the study was to determine whether the addition of the ghrelin agonist growth hormone releasing peptide 2 (GHRP-2) to cytotoxic therapy with 5-fluoruracil (5-FU) prevents the anorexia associated with chemotherapy in cancer cachectic mice. Thirty-three BALB/c female tumourbearing mice were randomized to receive a solution containing: (a) placebo; (b) GHRP-2; (c) 5-FU; or (d) 5-FU + GHRP-2. Ten BALB/c no tumour-bearing mice received placebo solution. Food intake and survival were checked. Six hours after the drug injection the cumulative food intake was signifi cantly increased in mice treated with the combination of 5-FU + GHRP-2 versus the 5-FU alone (P = 0.0096). On day 3, the cumulative food intake of mice treated with GHRP-2,5-FU and 5-FU + GHRP-2 signifi cantly increased com- pared with naive and vehicle groups (P = 0.0007, P = 0.0038 and P = 0.0166, respectively). The median survival time was longer in 5-FU + GHRP-2 treated mice than in those with 5-FU, although it was not signifi cant (18 d versus 15.5 d, P = 0.7). For the fi rst time, we demonstrated that the addition of GHRP-2 to cytotoxic therapy with 5-FU improved appetite in tumour-bearing mice with anorexia/cachexia syndrome in early stage. These data suggest that GHRP-2 may improve the effi cacy of therapy and the quality of life of cancer patients thank to the amelioration of their nutritional state.

Radiosensitivity of human colon cancer cell enhanced by immunoliposomal docetaxel

AIM:To enhance the radiosensitivity of human colon cancer cells by docetaxel. METHODS: Immunoliposomal docetaxel was prepared by coupling monoclonal antibody against carcinoembryonic antigen to cyanuric chloride at the PEG terminus of liposome. LoVo adenocarcinoma cell line was treated with immunoliposomal docetaxel or/and irradiation. MTT colorimetric assay was used to estimate cytotoxicity of immunoliposomal docetaxel and radiotoxicity. Cell cycle redistribution and apoptosis were determined with flow cytometry. Survivin expression in LoVo cells was verified by immunohistochemistry. D801 morphologic analysis system was used to semi-quantify immunohistochemical staining of survivin. RESULTS: Cytotoxicity was induced by immunoliposomal docetaxel alone in a dose-dependent manner. Immunoliposomal docetaxel yielded a cytotoxicity effect at a low dose of 2 nmol/L. With a single dose irradiation, the relative surviving fraction of LoVo cells showed a dose-dependent response, but there were no significant changes as radiation delivered from 4 to 8 Gy. Compared with liposomal docetaxel or single dose irradiation, strongly radiopotentiating effects of immunoliposomal docetaxel on LoVo cells were observed. A low dose of immunoliposomal docetaxel could yield sufficient radiosensitivity. Immunoliposomal docetaxel were achieved both specificity of the conjugated antibody and drug radiosensitization. Combined with radiation, immunoliposomal docetaxel significantly increased the percentage of G2/M cells and induced apoptosis, but significantly decreased the percentage of cells in G2/G1 and S phase by comparison with liposomal docetaxel. Immunohistochemical analysis showed that the brown stained survivin was mainly in cytoplasm of LoVo cells. Semi-quantitative analysis of the survivin immunostaining showed that the expression of survivin in LoVo cells under irradiation with immunoliposomal docetaxel was significantly decreased. CONCLUSION: Immunoliposomal docetaxel is strongly effective for target radiosensitation in LoVo colon carcinoma cells, and may offer the potential to improve local radiotherapy.

Estradiol agonists inhibit human Lo Vo colorectal-cancer cell proliferation and migration through p53

AIM: To investigate the effects of 17&#x003b2;-estradiol via estrogen receptors (ER) or direct administration of ER agonists on human colorectal cancer.

Leucine-rich repeat-containing G protein-coupled receptor 5 marks different cancer stem cell compartments in human Caco-2 and LoVo colon cancer lines

BACKGROUND Colon cancer cell lines are widely used for research and for the screening of drugs that specifically target the stem cell compartment of colon cancers.It was reported that colon cancer carcinoma specimens contain a subset of leucine-rich repeatcontaining G protein-coupled receptor 5(LGR5)-expressing stem cells,these socalled“tumour-initiating”cells,reminiscent in their properties of the normal intestinal stem cells(ISCs),may explain the apparent heterogeneity of colon cancer cell lines.Also,colon cancer is initiated by aberrant Wnt signaling in ISCs known to express high levels of LGR5.Furthermore,in vivo reports demonstrate the clonal expansion of intestinal adenomas from a single LGR5-expressing cell.AIM To investigate whether colon cancer cell lines contain cancer stem cells and to characterize these putative cancer stem cells.METHODS A portable fluorescent reporter construct based on a conserved fragment of the LGR5 promoter was used to isolate the cell compartments expressing different levels of LGR5 in two widely used colon cancer cell lines(Caco-2 and LoVo).These cells were then characterized according to their proliferation capacity,gene expression signatures of ISC markers,and their tumorigenic properties in vivo and in vitro.RESULTS The data revealed that the LGR5 reporter can be used to identify and isolate a classical intestinal crypt stem cell-like population from the Caco-2,but not from the LoVo,cell lines,in which the cancer stem cell population is more akin to B lymphoma Moloney murine leukemia virus insertion region 1 homolog(+4 crypt)stem cells.This sub-population within Caco-2 cells exhibits an intestinal cancer stem cell gene expression signature and can both self-renew and generate differentiated LGR5 negative progeny.Our data also show that cells expressing high levels of LGR5/enhanced yellow fluorescent protein(EYFP)from this cell line exhibit tumorigenic-like properties in vivo and in vitro.In contrast,cell compartments of LoVo that are expressing high levels of LGR5/EYFP did not show these stem cell-like properties.Thus,cells that exhibit high levels of LGR5/EYFP expression represent the cancer stem cell compartment of Caco-2 colon cancer cells,but not LoVo cells.CONCLUSION Our findings highlight the presence of a spectrum of different ISC-like compartments in different colon cancer cell lines.Their existence is an important consideration for their screening applications and should be taken into account when interpreting drug screening data.We have generated a portable LGR5-reporter that serves as a valuable tool for the identification and isolation of different colon cancer stem cell populations in colon cancer lines.

Expression of T-STAR gene is associated with regulation of telomerase activity in human colon cancer cell line HCT-116

AIM： To investigate the effects on telomerase activity of transfection of human T-STAR gene full-length sense cDNA or partial antisense cDNA into human colon cancer cell line HCT-116.METHODS： mRNA and protein expression levels of T-STAR gene were determined by RT-PCR and western blot, and telomerase activity was measured by PCR- ELISA, after transfection of T-STAR sense or antisense gene into HCT-116 cells with lipofectamine. RESULTS： T-STAR gene expression was enhanced or knocked down both at mRNA and protein levels, and telomerase activity was significantly increased or decreased. CONCLUSION： The T-STAR gene may participate in regulation of telomerase activity in human colon cancer HCT-116 cells in a parallel fashion.

Down-regulation of p110β Expression Increases Chemosensitivity of Colon Cancer Cell Lines to Oxaliplatin

This study examined the synergetic effect of class ⅠA Phosphoinositide 3-kinases catalytic subunit p110β knockdown in conjunction with oxaliplatin treatment on colon cancer cells. Down-regulation of p110β by siRNA interference and oxaliplatin treatment were applied in colon cancer cell lines HT29, SW620 and HCT116. MTT assay was used to measure the inhibitory effect of p110β knockdown on the proliferation of colon cancer cell lines. SubG1 assay and Annexin-Ⅴ FITC/PI double-labeling cytometry were applied to detect cell apoptosis. And cell cycle was evaluated by using PI staining and flow cytometry. The expression of caspase 3, cleaved PARP, p-Akt, T-Akt and p110β was determined by western blotting. The results suggested that down-regulation of p110β expression by siRNA obviously reduced cell number via accumulation in G0-G1 phase of the cell cycle in the absence of notablely increased apoptosis in colon cancer cell lines HT29 and SW620 (S phase arrest in HCT116). Moreover, inhibition of p110β expression increased oxaliplatin-induced cell apoptosis and cell cycle arrest in HT29, HCT116 and SW620 cell lines. In addition, increases of cleaved caspase-3 and cleaved PARP induced by oxaliplatin treatment were determined by immunoblotting in p110β knockdown group compared with normal control group and wildtype group. It is concluded that down-regulated expression of p110β could inhibit colon cancer cells proliferation and result in increased chemosensitivity of colorectal cancer cells to oxaliplatin through augmentation of oxaliplatin-induced cell apoptosis and cell cycle arrest.

EFFECT OF TNF-a AND IFN-g ON THE EXPRESSION OF INDUCIBLE NITRIC OXIDE SYNTHASE GENE AND PROLIFERATION INHIBITION OF HUMAN COLON CANCER CELL LINE

Objective: To study the expression of the inducible nitric oxide synthase (iNOS) gene and the effects of tumor necrosis factor-α(TNF-a) and interferon-γ(IFN-g)on proliferation of the continuous cultured human colon cancer cell line CCL229. Methods: Using the molecular and biochemical techniques and electron microscopy to analyze the expression of iNOS, production of NO and growth characteristics of human colon cancer cells. Results: cytokine treatment can induce expression of the iNOS gene and production of nitric oxide was significantly higher after treatment of CCL229 cells with TNF-αor IFN-γ. Treatment with either cytokine or a combination of both significantly increased levels of Malondialdehyde (MDA) over control. Furthermore, cytokine treatment increased the proliferation inhibition rate as assessed in vitro and decreased the cell proliferation index on flow cytometry. Electron microscopy showed that cells treated with cytokines had fewer pseudopodia or cell processes than control cells and that cytokine treated cells had dilatation of the mitochondria and endoplasmic reticulum and dilated vesicular or tubular cisternae. Conclusion: Our findings indicate that TNF-α and IFN-γ induce the expression of iNOS gene in CCL229 cells, which increases the production of nitric oxide, inhibits proliferation, causes lipid peroxidation, and results in ultrastructural changes.

INHIBITORY EFFECT OF DEMO ON THE GROWTH OF TRANSPLANTED HUMAN COLON CANCER IN NUDE MICE

A human colon cancer cell line Hce- 8693 was heterotransplanted in nude mice. Polyamine blosythesis Inhibitor a- dlfiuoromethylomithine (DFMO ) show a marked reproducible inhibition in this model. The size and weight of transplanted tumor In DFMO group were smaller than those of the control group and the average inhibition rate was 72.8% (P < 0.001) . DFMO showed higher tumor inhibitory rate than 5-Fu (35. 4%) (P<0. 001) . Furthermore. DFMO demonstrated less severe bone marrow inhibition in the nude mice than 5-Fu (20. 0% Vs 53. 2%. P<0. 001) .There was no synergistic action in these two drugs at the experimental dose. The concentration of putrescine and spermidine in the plasma and tumor tissue in the DFMO group were 70% lower than those of the control group (P<0. 001) . These results indicate that the anti-tumor effect of DFMO might be explained by the inhibition of polyamine biosynthesis and this study provides an experimental basis for future clinical application of DFMO.

DZNep inhibits the proliferation of colon cancer HCT116 cells by inducing senescence and apoptosis

EZH2 is over-expressed in human colon cancer and is closely associated with tumor proliferation,metastasis and poor prognosis.Targeting and inhibiting EZH2 may be an effective therapeutic strategy for colon cancer.3-Deazaneplanocin A(DZNep),as an EZH2 inhibitor,can suppress cancer cell growth.However,the anti-cancer role of DZNep in colon cancer cells has been rarely studied.In this study,we demonstrate that DZNep can inhibit the growth and survival of colon cancer HCT116 cells by inducing cellular senescence and apoptosis.The study provides a novel view of anti-cancer mechanisms of DZNep in human colon cancer cells.

Oxidative stress-induced mitochondrial dysfunction in a normal colon epithelial cell line

AIM To determine how a normal human colon cell line reacts to microbial challenge as a way to study oxidative stress-induced responses associated with inflammatory bowel disease.METHODS Normal human colon epithelial cells(ATCC?CRL.1790?)were stimulated with either heat killed E.coli or heat killed murine cecal contents(HKC)and examined for several relevant biomarkers associated with inflammation and oxidative stress including cytokine production,mitochondrial autophagy and oxidant status.TNFα,IL-1βand IL-8 protein concentrations were measured within the supernatants.Fluorescent microscopy was performed to quantify the production of reactive oxygen species(ROS)using an oxidation responsive fluorogenic probe.Mitochondrial morphology and mitochondrial membrane potential was assessed by dual staining using COXIV antibody and a dye concentrating in active mitochondria.Mitochondrial ROS scavenger was used to determine the source of ROS in stimulated cells.Autophagy was detected by staining for the presence of autophagic vesicles.Positive controls for autophagy and ROS/RNS experiments were treated with rapamycin and chloroquine.Mitochondrial morphology,ROS production and autophagy microscopy experiments were analyzed using a custom acquisition and analysis microscopy software(Image J).RESULTS Exposing CRL.1790 cells to microbial challenge stimulated cells to produce several relevant biomarkers associated with inflammation and oxidative stress.Heat killed cecal contents treatment induced a 10-12fold increase in IL-8 production by CRL.1790 cells compared to unstimulated controls at 6 and 12 h(P<0.001).Heat killed E.coli stimulation resulted in a4-5 fold increase in IL-8 compared to the unstimulated control cells at each time point(P<0.001).Both heat killed E.coli and HKC stimulated robust ROS production at 6(P<0.001),and 12 h(P<0.01).Mitochondrial morphologic abnormalities were detected at 6 and12 h based on reduced mitochondrial circularity and decreased mitochondrial membrane potential,P<0.01.Microbial stimulation also induced significant autophagy at 6 and 12 h,P<0.01.Lastly,blocking mitochondrial ROS generation using mitochondrial specific ROS scavenger reversed microbial challenge induced mitochondrial morphologic abnormalities and autophagy.CONCLUSION The findings from this study suggest that CRL.1790cells may be a useful alternative to other colon cancer cell lines in studying the mechanisms of oxidative stress events associated with intestinal inflammatory disorders.