LS174T Cells Research Articles

Effects of sulforaphane and its S- and R-enantiomers on the expression and activities of human drug-metabolizing cytochromes P450

The effects of S/R-enantiomers of sulforaphane on drug-metabolizing cytochromes P450, in particular: (i) expression of CYP1A1/2, CYP2B6, CYP2C9, CYP3A4 mRNAs and proteins in human hepatocytes; (ii) mRNA expression and activity of pregnane X receptor (PXR), aryl hydrocarbon receptor (AhR) and glucocorticoid receptor (GR) in human hepatocytes and transgenic gene reporter cell lines, respectively; (iii) catalytic activity of CYP1A2, CYP2A6, CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2D6, CYP2E1 and CYP3A4 in human liver microsomes and human hepatocytes were investigated. The major findings are that (i) sulforaphane exerted insignificant effects on the expression of CYP1A1/2, CYP2B6, CYP2C9, CYP3A4 mRNAs and proteins. We observed induction of CYP2C9 and CYP2B6, but these effects were inconsistent, not enantiospecific, with inter-individual variability between human hepatocytes cultures; (ii) sulforaphane displayed a dose-dependent but not enantiospecific cytotoxicity in HepG2, HeLa and LS174T cells. Sulforaphane had no effects on the expression (mRNA) and transcriptional activity (agonist/antagonist) of AhR, GR and PXR as revealed by RT-PCR and gene reporter assays; (iii) sulforaphane inhibited CYP2A6 (IC50 12 µM), CYP2D6 (IC50 39 µM) and CYP3A4 (IC50 52 µM) in hepatocytes; in microsomes, CYP2D6 (Ki 111 µM) CYP3A4 (Ki 27 µM-testosterone or Ki 193 µM-midazolam) were inhibited and the effects were not enantiospecific.

PTD-Modified ATTEMPTS for Enhanced Toxin-based Cancer Therapy: An In Vivo Proof-of-Concept Study.

To investigate the feasibility of applying PTD-modified ATTEMPTS (Antibody Targeted Triggered Electrically Modified Prodrug-Type Strategy) for enhanced toxin therapy for the treatment of cancer. A heparin-functionalized murine anti-CEA monoclonal antibody (mAb), T84.66-heparin (T84.66-Hep), was chemically synthesized and characterized for specific binding to CEA overexpressed cells. The T84.66-Hep was then applied to the PTD-modified ATTEMPTS approach and the crucial features of the drug delivery system (DDS), 'antibody targeting' and 'heparin/protamine-based prodrug', were evaluated in vitro to examine whether it could selective delivery a PTD-modified toxin, recombinant TAT-gelonin chimera (TAT-Gel), to CEA high expression cancer cells (LS174T). Furthermore, the feasibility of the drug delivery system (DDS) was assessed in vivo by biodistribution and efficacy studies using LS174T s.c. xenograft tumor bearing mice. T84.66-Hep displayed specific binding, but limited internalization (35% after 48h incubation) to CEA high expression LS174T cells over low expression HCT116 cells. When mixed together with TAT-Gel, the T84.66-Hep formed a strong yet reversible complex. This complex formation provided an effective means of active tumor targeting of TAT-Gel, by 1) directing the TAT-Gel to CEA overexpressed tumor cells and 2) preventing nonspecific cell transduction to non-targeted normal cells. The cell transduction of TAT-Gel could, however, be efficiently reversed by addition of protamine. Feasibility of in vivo tumor targeting and "protamine-induced release" of TAT-Gel from the T84.66-Hep counterpart was confirmed by biodistribution and preliminary efficacy studies. This study successfully demonstrated in vitro and in vivo the applicability of PTD-modified ATTEMPTS for toxin-based cancer therapy.

Simultaneous evaluation of human CYP3A4 and ABCB1 induction by reporter assay in LS174T cells, stably expressing their reporter genes.

The bioavailability of orally administered therapies are often significantly limited in the human intestine by the metabolic activities of cytochrome P450 3A4 (CYP3A4) and P-glycoprotein (P-gp). Predicting whether candidate compounds induce CYP3A4 and P-gp is a crucial stage in the drug development process, as drug-drug interactions may result in the induction of intestinal CYP3A4 and P-gp. However, the assay systems needed to evaluate both CYP3A4 and P-gp induction in the intestine are yet to be established. To address this urgent requirement, LS174T cells were used to create two stable cell lines expressing the CYP3A4 or ATP-binding cassette subfamily B member 1 (ABCB1, encoding P-gp) reporter genes. First, these stable cells were tested by treatment with 1α,25-dihydroxyvitamin D3 (1,25(OH)2D3), all-trans-retinoic acid (ATRA) and 9-cis-retinoic acid (9-cis RA) that induce CYP3A4 and P-gp in the intestines. All these compounds significantly increased both CYP3A4 and ABCB1 reporter activities in the stable cell lines. To simultaneously assess the induction of CYP3A4 and ABCB1, both stable cells were co-cultivated to measure their reporter activities. The mixed cells showed a significant increase in the CYP3A4 and ABCB1 reporter activities following treatment with 1,25(OH)2 D3, ATRA, and 9-cis RA. These activity levels were maintained after passaging more than 20 times and following multiple freeze-thaw cycles. These results demonstrate that our established cell lines can be used to evaluate simultaneously CYP3A4 and ABCB1 induction in the intestines, providing a valuable in vitro model for the evaluation of future drug candidates.

Ultra-Performance Liquid Chromatography/Mass Spectrometry Study of Metabolism of 5-Methylpyranopelargonidin

Anthocyanin dyes represent an important group of plant polyphenols significantly affecting human diet. Their stability in solution is low and it depends on pH, presence of sulfur dioxide and other parameters. Many stable pyranoanthocyanins are formed by condensation of anthocyanins with small reactive compounds, i.e. pyruvic acid, acetaldehyde, acetone and others, commonly during maturation of food products (e.g. wines and juices). To date, little is known about their metabolism. This communication deals with the study of in vitro metabolism of 5-methylpyranopelargonidin (5-MePPl) as a simple member of the pyranoanthocyanin family and its direct comparison with common flavonoids quercetin and pelargonidin. Human colon adenocarcinoma cells LS174T and human hepatocellular carcinoma cells HepG2 were used for experiments. Metabolites were analyzed by UPLC/MS/MS. Quercetin underwent extensive biotransformation with a metabolic profile typical for flavonoids, corroborating that the used cells were metabolically active in parallel experiments with pelargonidin and 5-MePPl (condensation of two and three quercetin molecules was tentatively proposed in addition). Biotransformation of 5-methylpyranopelargonidin proceeded with higher yield of metabolites compared to pelargonidin. Processes related to accumulation of 5-MePPl metabolites in pellets exhibit significant differences compared to quercetin and pelargonidin. The fact can be ascribed to the presence of an additional ring (D) in the flavonoid skeleton and probably to a higher hydrophobicity of pyrano-dye compared to both other studied flavonoids. Hydroxylation, glucuronation and glucosidation are the main metabolic processes observed during in vitro metabolization of 5-MePPl providing several chromatographically resolved isomers of metabolites. Moreover, some combined metabolites were found and the site of metabolization in the 5-MePPl structure was specified based on collision spectra.

Butyrate modulates bacterial adherence on LS174T human colorectal cells by stimulating mucin secretion and MAPK signaling pathway.

BACKGROUND/OBJECTIVESFermentation of dietary fiber results in production of various short chain fatty acids in the colon. In particular, butyrate is reported to regulate the physical and functional integrity of the normal colonic mucosa by altering mucin gene expression or the number of goblet cells. The objective of this study was to investigate whether butyrate modulates mucin secretion in LS174T human colorectal cells, thereby influencing the adhesion of probiotics such as Lactobacillus and Bifidobacterium strains and subsequently inhibiting pathogenic bacteria such as E. coli. In addition, possible signaling pathways involved in mucin gene regulation induced by butyrate treatment were also investigated.MATERIALS/METHODSMucin protein content assay and periodic acid-Schiff (PAS) staining were performed in LS174T cells treated with butyrate at various concentrations. Effects of butyrate on the ability of probiotics to adhere to LS174T cells and their competition with E. coli strains were examined. Real time polymerase chain reaction for mucin gene expression and Taqman array 96-well fast plate-based pathway analysis were performed on butyrate-treated LS174T cells.RESULTSTreatment with butyrate resulted in a dose-dependent increase in mucin protein contents in LS174T cells with peak effects at 6 or 9 mM, which was further confirmed by PAS staining. Increase in mucin protein contents resulted in elevated adherence of probiotics, which subsequently reduced the adherent ability of E. coli. Treatment with butyrate also increased transcriptional levels of MUC3, MUC4, and MUC12, which was accompanied by higher gene expressions of signaling kinases and transcription factors involved in mitogen-activated protein kinase (MAPK) signaling pathways.CONCLUSIONSBased on our results, butyrate is an effective regulator of modulation of mucin protein production at the transcriptional and translational levels, resulting in changes in the adherence of gut microflora. Butyrate potentially stimulates the MAPK signaling pathway in intestinal cells, which is positively correlated with gut defense.

Transfection of thymidine phosphorylase cDNA with lentiviral vector enhances the anticancer effect of 5'-deoxy-5-fluorouridine on colorectal cancer cell lines HT29 and LS174T

To explore the changes of anticancer efficiency of 5'-deoxy-5-fluorouridine (5'-DFUR) and 5-fluorouracil (5-Fu) in colorectal cancer cell line HT29 and LS174T cells after transfection of thymidine phosphorylase (TP) cDNA with a lentiviral vector. TP cDNA was transfected into human colorectal cancer cell lines HT29 and LS174T with the lentiviral vector pLenti6.3-MCS-IRES2-EGFP, and the transfection efficiency of the two cell lines passed 5 generations was analyzed by flow cytometry. The expression of TP protein and the relative quantitative expression of TP mRNA in these 2 cell lines were detected by Western blot and RT-PCR, respectively. The 50% inhibitory concentration (IC50) of 5'-DFUR and 5-Fu in both HT29 and LS174T parent cells and TP-transfected cells were assessed by MTS assay. Finally, the concentration of converted 5-Fu was detected by high performance liquid chromatography (HPLC) either in the medium containing a series of concentrations of 5'-DFUR, in which HT29/HT29-TP or LS174T/LS174T-TP cells were cultured, or in the cell culture lysates. The HT29 and LS174T cells transfected with human TP cDNA were monitored for 5 generations, and their transfection efficiency was about 95.0%. Immunohistochemical staining showed that both the parent cells and TP-transfected HT29 and LS174T cells were TP-positive, while vector-transfected cells were TP-negative. Western blotting showed that the TP protein expression in HT29-TP and LS174T-TP cells were significantly increased compared with that in their parents cells. The relative quantity (RQ) values of TP mRNA in HT29-TP and LS174T-TP cells were 8.45 ± 0.15 and 2 615.02 ± 253.97, respectively, which were significantly higher than that in their parents cells (P < 0.01). The IC50 values of 5'-DFUR on HT29-TP cells and its parents cell were (14.33 ± 0.74) µmol/L and (707.66 ± 5.66) µmol/L, respectively (P < 0.05), while (0.59 ± 0.11) µmol/L in LS174T-TP cells and (239.20 ± 21.83) µmol/L in its parent cells, respectively (P < 0.05). The IC50 values of 5-Fu of HT29-TP cells and its parents cells were (5.42 ± 0.75) µmol/L and (14.19 ± 0.97) µmol/L, respectively (P < 0.05), while (4.41 ± 0.96)µmol/L in LS174T-TP cells and (16.42 ± 2.12)µmol/L in its parents cells, respectively (P < 0.05). The HPLC results showed that the 5-Fu concentration detected from media contained a series of concentrations of 5'-DFUR for culturing HT29-TP and LS174T-TP cells were 12.2 to 28.7-folds and 13.1 to 23.6-folds, respectively, higher than that in their parents cells, (P < 0.01 for all). Otherwise, just a little of 5-Fu was detected in the two TP-transfected cells lysate, about 0.9% to 4.2% of 5-Fu detected in the media of the same cultured cells, whereas no 5-Fu was detected in the two parent cell lysates. Transfection of TP cDNA into colorectal cancer cell lines HT29 and LS174T with lentiviral vector can improve the expression of both TP mRNA and TP protein levels in passaged cells, enhance the conversion of 5-Fu from 5'-DFUR in the medium, and result in an enhanced anticancer effect on these two cell lines.

CEACAM1 and hollow spheroid formation modulate the chemosensitivity of colorectal cancer to 5-fluorouracil.

Carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) re-expressed and promoted hollow spheroid (HS) formation beyond the invasion front of colorectal cancer. The aim of the present study was to clarify whether CEACAM1 cytoplasmic domain isoform balance and HS are associated with resistance to 5-fluorouracil (5FU). Two-dimensional (D) or 3D culture systems were employed to evaluate the effects of CEACAM1 cytoplasmic isoform balance and HS formation on the chemosensitivity of colorectal cancer cells to 5FU. The risk factors for postoperative recurrence were calculated based on the presence of HS and various clinicopathological characteristics in 82 patients with Stage III colorectal cancer who had undergone curative surgery followed by 5FU-based chemotherapy. CEACAM1-4L-transfected HT29 and CEACAM1-4L and 4S expressing parental LS174T cells had significantly higher resistance to 5FU in comparison with CEACAM1-4S- or vector control-transfected cells. In 3D culture, HS formation induced by CEACAM1-4L induced chemoresistance to 5FU, whereas the solid spheres formed in response to CEACAM1-4S were destroyed by 5FU treatment. HS was identified as an independent factor for recurrence of Stage III colorectal cancer after curative resection followed by 5FU-based chemotherapy. Kaplan-Meier survival curves demonstrated that patients with HS had lower recurrence-free survival rate. CEACAM1 long cytoplasmic domain isoform dominance and HS formation are phenotypes associated with chemoresistance to 5FU.

Galacto-oligosaccharides may directly enhance intestinal barrier function through the modulation of goblet cells.

Here we have tested the hypothesis that prebiotic galacto-oligosaccharides (GOS) may enhance mucosal barrier function through direct modulation of goblet cell function. Human adenocarcinoma-derived LS174T cells, which exhibit an intestinal goblet cell-like phenotype, were used to examine the non-prebiotic effects of GOS on goblet cell functions. LS174T cells were treated with GOS, and the expression of goblet cell secretory product genes mucin 2 (MUC2), trefoil factor 3 (TFF3), resistin-like molecule beta (RETNLB) and the Golgi-sulfotransferase genes, carbohydrate (N-acetylglucosamine-6-O) sulfotransferase 5 (CHST5) and galactose-3-O-sulfotransferase 2 (GAL3ST2), was determined by real-time quantitative RT-PCR. In addition, the abundance of CHST5, TFF3 and RETNLB was confirmed by Western blot analysis. Following treatment with GOS for 72 h, the expression of MUC2 was significantly upregulated 2-4-fold, CHST5 and RETNLB, 5-7-fold, and TFF3 2-4-fold. Western blot analysis demonstrated increased abundance of RETNLB, TFF3 and CHST5. Addition of the Th2 cytokine IL-13 along with GOS resulted in synergistic induction of RETNLB and CHST5. IL-8 secretion was not affected by GOS treatment, suggesting that the effects of GOS are not mediated through an inflammatory pathway. Collectively, the data indicate that GOS may enhance mucosal barrier function through direct stimulation of intestinal goblet cells.

Inhibition of TMEM16A expression suppresses growth and invasion in human colorectal cancer cells.

Metastasis leads to poor prognosis in colorectal cancer patients, and there is a growing need for new therapeutic targets. TMEM16A (ANO1, DOG1 or TAOS2) has recently been identified as a calcium-activated chloride channel (CaCC) and is reported to be overexpressed in several malignancies; however, its expression and function in colorectal cancer (CRC) remains unclear. In this study, we found expression of TMEM16A mRNA and protein in high-metastatic-potential SW620, HCT116 and LS174T cells, but not in primary HCT8 and SW480 cells, using RT-PCR, western blotting and immunofluorescence labeling. Patch-clamp recordings detected CaCC currents regulated by intracellular Ca2+ and voltage in SW620 cells. Knockdown of TMEM16A by short hairpin RNAs (shRNA) resulted in the suppression of growth, migration and invasion of SW620 cells as detected by MTT, wound-healing and transwell assays. Mechanistically, TMEM16A depletion was accompanied by the dysregulation of phospho-MEK, phospho-ERK1/2 and cyclin D1 expression. Flow cytometry analysis showed that SW620 cells were inhibited from the G1 to S phase of the cell cycle in the TMEM16A shRNA group compared with the control group. In conclusion, our results indicate that TMEM16A CaCC is involved in growth, migration and invasion of metastatic CRC cells and provide evidence for TMEM16A as a potential drug target for treating metastatic colorectal carcinoma.

Pyruvate dehydrogenase kinase expression and metabolic changes following dichloroacetate exposure in anoxic human colorectal cancer cells

Dichloroacetate (DCA) is a small molecule that inhibits pyruvate dehydrogenase kinase (PDK) to constrain the aerobic glycolytic pathway observed in many cancer cells and effectively kill them with limited cytotoxicity on normal cells. We previously showed that DCA induced a cytoprotective effect in different human colorectal cancer (CRC) cell lines under anoxic conditions. In this study, we investigated the molecular and metabolic changes that may be providing this cytoprotection. The expression profiles of PDK isoforms in SW480 and LS174T cells along with subsequent changes in pyruvate dehydrogenase (PDH) phosphorylation were assessed following DCA exposure. Changes in mitochondrial activity and subsequent glucose consumption and lactate production were then examined. We show evidence of differential regulation in PDH phosphorylation between different human CRC cells leading to differences in mitochondrial activity following DCA exposure. However, these effects did not lead to significant changes in cellular metabolism nor growth. In conclusion, DCA may only be beneficial in treating a subset of tumor types based on their molecular profiles of different PDK isoforms.

Inhibitory effect of cucurbitacin B on proliferation of human colon cancer cells

Objective To investigate the inhibitory effect of cucurbitacin B on proliferation of human colon cancer cells.Methods LS174-T cells were treated with different concentrations of cucurbitacin B (0.01,0.10,1.00,10.00,and 100.00 mol/L) for 24,48 and 72 h.The cell proliferation was detected by cell counting kit-8 (CCK-8) method,and the distribution of cell cycle by flow cytometry.signaling transducers and activators of transcription 3 (STAT3),Caspase-3,and Tert mRNA were detected by fluorescence quantitative polymerase chain reaction (FQ-PCR).Results CCK-8 results showed that after treatment with cucurbitacin B (0.01 and 100.00 moL/L) for 24 h,inhibitory rate of LS174-T cell proliferation was (5.22 ±2.02)％ and (73.90 ± 1.85)％ respectively.After treatment with 100.00 mol/L of cucurbitacin B for 24 h and 48 h,inhibitory rate was (73.90 ± 1.85)％ and (98.84 ±0.51)％ respectively.The statistically significant difference was dose-and time-dependent (P ＜ 0.05).Flow cytometry revealed that as compared with control group,the percentage of cells in G2/M phase in 1.00 μmol/L concentration group was increased [(6.33 ± 0.74) ％ and (30.43 ± 4.09) ％],and that in G0/G1 phase decreased [(78.5 ± 4.72) ％ and (43.2 ± 5.65) ％] with the difference being statistically significant (P ＜0.05).The FQ-PCR indicated that after treatment with cucurbitacin B of 0.01 and 10.00 mol/L for 24 h,STAT3 level was 0.750 0 ±0.003 8,0.660 0 ±0.005 5,respectively.After treatment with cucurbitacin B of 0.10 μmol/L for 24 h and 48 h,Caspase-3 mRNA level was 4.30 ±0.29 and 6.79 ±0.13 respectively with the difference being statistically significant (P ＜ 0.05).Conclusion Cucurbitacin B can inhibit proliferation of colon cancer cells. Key words: Cucurbitacin B; Colon cancer; Proliferation

Carboxymefloquine, the major metabolite of the antimalarial drug mefloquine, induces drug-metabolizing enzyme and transporter expression by activation of pregnane X receptor.

Malaria patients are frequently coinfected with HIV and mycobacteria causing tuberculosis, which increases the use of coadministered drugs and thereby enhances the risk of pharmacokinetic drug-drug interactions. Activation of the pregnane X receptor (PXR) by xenobiotics, which include many drugs, induces drug metabolism and transport, thereby resulting in possible attenuation or loss of the therapeutic responses to the drugs being coadministered. While several artemisinin-type antimalarial drugs have been shown to activate PXR, data on nonartemisinin-type antimalarials are still missing. Therefore, this study aimed to elucidate the potential of nonartemisinin antimalarial drugs and drug metabolites to activate PXR. We screened 16 clinically used antimalarial drugs and six major drug metabolites for binding to PXR using the two-hybrid PXR ligand binding domain assembly assay; this identified carboxymefloquine, the major and pharmacologically inactive metabolite of the antimalarial drug mefloquine, as a potential PXR ligand. Two-hybrid PXR-coactivator and -corepressor interaction assays and PXR-dependent promoter reporter gene assays confirmed carboxymefloquine to be a novel PXR agonist which specifically activated the human receptor. In the PXR-expressing intestinal LS174T cells and in primary human hepatocytes, carboxymefloquine induced the expression of drug-metabolizing enzymes and transporters on the mRNA and protein levels. The crucial role of PXR for the carboxymefloquine-dependent induction of gene expression was confirmed by small interfering RNA (siRNA)-mediated knockdown of the receptor. Thus, the clinical use of mefloquine may result in pharmacokinetic drug-drug interactions by means of its metabolite carboxymefloquine. Whether these in vitro findings are of in vivo relevance has to be addressed in future clinical drug-drug interaction studies.

The carboxyl terminus of VEGF-A is a potential target for anti-angiogenic therapy.

Anti-VEGF-A therapy has become a mainstay of treatment for ocular neovascularisation and in cancer; however, their effectiveness is not universal, in some cases only benefiting a minority of patients. Anti-VEGF-A therapies bind and block both pro-angiogenic VEGF-Axxx and the partial agonist VEGF-Axxxb isoforms, but their anti-angiogenic benefit only comes about from targeting the pro-angiogenic isoforms. Therefore, antibodies that exclusively target the pro-angiogenic isoforms may be more effective. To determine whether C-terminal-targeted antibodies could inhibit angiogenesis, we generated a polyclonal antibody to the last nine amino acids of VEGF-A165 and tested it in vitro and in vivo. The exon8a polyclonal antibody (Exon8apab) did not bind VEGF-A165b even at greater than 100-fold excess concentration, and dose dependently inhibited VEGF-A165 induced endothelial migration in vitro at concentrations similar to the VEGF-A antibody fragment ranibizumab. Exon8apab can inhibit tumour growth of LS174t cells implanted in vivo and blood vessel growth in the eye in models of age-related macular degeneration, with equal efficacy to non-selective anti-VEGF-A antibodies. It also showed that it was the VEGF-Axxx levels specifically that were upregulated in plasma from patients with proliferative diabetic retinopathy. These results suggest that VEGF-A165-specific antibodies can be therapeutically useful.

Role of Bcl-xL/Beclin-1 in synergistic apoptotic effects of secretory TRAIL-armed adenovirus in combination with mitomycin C and hyperthermia on colon cancer cells.

In this study, we attempted to develop a multimodality approach using chemotherapeutic agent mitomycin C, biologic agent tumor necrosis factor-related apoptosis-inducing ligand (TRAIL/Apo-2L), and mild hyperthermia to treat colon cancer. For this study, human colon cancer LS174T, LS180, HCT116 and CX-1 cells were infected with secretory TRAIL-armed adenovirus (Ad.TRAIL) and treated with chemotherapeutic agent mitomycin C and hyperthermia. The combinatorial treatment caused a synergistic induction of apoptosis which was mediated through an increase in caspase activation. The combinational treatment promoted the JNK-Bcl-xL-Bak pathway which transmitted the synergistic effect through the mitochondria-dependent apoptotic pathway. JNK signaling led to Bcl-xL phosphorylation at serine 62, dissociation of Bak from Bcl-xL, oligomerization of Bak, alteration of mitochondrial membrane potential, and subsequent cytochrome c release. Overexpression of dominant-negative mutant of Bcl-xL (S62A), but not dominant-positive mutant of Bcl-xL (S62D), suppressed the synergistic death effect. Interestingly, Beclin-1 was dissociated from Bcl-xL and overexpression of dominant-negative mutant of Bcl-xL (S62A), but not dominant-positive mutant of Bcl-xL (S62D), suppressed dissociation of Beclin-1 from Bcl-xL. A combinatorial treatment of mitomycin C, Ad.TRAIL and hyperthermia induced Beclin-1 cleavage, but the Beclin-1 cleavage was abolished in Beclin-1 double mutant (D133A/D146A) knock-in HCT116 cells, suppressing the apoptosis induced by the combination therapy. We believe that this study supports the application of the multimodality approach to colon cancer therapy.

PGE2-induced colon cancer growth is mediated by mTORC1

The inflammatory prostaglandin E2 (PGE2) cytokine plays a key role in the development of colon cancer. Several studies have shown that PGE2 directly induces the growth of colon cancer cells and furthermore promotes tumor angiogenesis by increasing the production of the vascular endothelial growth factor (VEGF). The signaling intermediaries implicated in these processes have however not been fully characterized. In this report, we show that the mechanistic target of rapamycin complex 1 (mTORC1) plays an important role in PGE2-induced colon cancer cell responses. Indeed, stimulation of LS174T cells with PGE2 increased mTORC1 activity as observed by the augmentation of S6 ribosomal protein phosphorylation, a downstream effector of mTORC1. The PGE2 EP4 receptor was responsible for transducing the signal to mTORC1. Moreover, PGE2 increased colon cancer cell proliferation as well as the growth of colon cancer cell colonies grown in matrigel and blocking mTORC1 by rapamycin or ATP-competitive inhibitors of mTOR abrogated these effects. Similarly, the inhibition of mTORC1 by downregulation of its component raptor using RNA interference blocked PGE2-induced LS174T cell growth. Finally, stimulation of LS174T cells with PGE2 increased VEGF production which was also prevented by mTORC1 inhibition. Taken together, these results show that mTORC1 is an important signaling intermediary in PGE2 mediated colon cancer cell growth and VEGF production. They further support a role for mTORC1 in inflammation induced tumor growth.

Activation of Epidermal Growth Factor Receptor Mediates Mucin Production Stimulated by p40, a Lactobacillus rhamnosus GG-derived Protein

The mucus layer coating the gastrointestinal tract serves as the first line of intestinal defense against infection and injury. Probiotics promote mucin production by goblet cells in the intestine. p40, a Lactobacillus rhamnosus GG-derived soluble protein, has been shown to transactivate the EGF receptor (EGFR) in intestinal epithelial cells, which is required for inhibition of apoptosis and preservation of barrier function in the colon, thereby ameliorating intestinal injury and colitis. Because activation of EGFR has been shown to up-regulate mucin production in goblet cells, the purpose of this study was to investigate the effects and mechanisms of p40 regulation of mucin production. p40 activated EGFR and its downstream target, Akt, in a concentration-dependent manner in LS174T cells. p40 stimulated Muc2 gene expression and mucin production in LS174T cells, which were abolished by inhibition of EGFR kinase activity, down-regulation of EGFR expression by EGFR siRNA transfection, or suppression of Akt activation. Treatment with p40 increased mucin production in the colonic epithelium, thus thickening the mucus layer in the colon of wild type, but not of Egfr(wa5) mice, which have a dominant negative mutation in the EGFR kinase domain. Furthermore, inhibition of mucin-type O-linked glycosylation suppressed the effect of p40 on increasing mucin production and protecting intestinal epithelial cells from TNF-induced apoptosis in colon organ culture. Thus, these results suggest that p40-stimulated activation of EGFR mediates up-regulation of mucin production, which may contribute to the mechanisms by which p40 protects the intestinal epithelium from injury.

Cytotoxicity and metabolic stress induced by acetaldehyde in human intestinal LS174T goblet-like cells.

There is compelling evidence indicating that ethanol and its oxidative metabolite acetaldehyde can disrupt intestinal barrier function. Apart from the tight junctions, mucins secreted by goblet cells provide an effective barrier. Ethanol has been shown to induce goblet cell injury associated with alterations in mucin glycosylation. However, effects of its most injurious metabolite acetaldehyde remain largely unknown. This study aimed to assess short-term effects of acetaldehyde (0, 25, 50, 75, 100 μM) on functional characteristics of intestinal goblet-like cells (LS174T). Oxidative stress, mitochondrial function, ATP, and intramitochondrial calcium (Ca(2+)) were assessed by dichlorofluorescein, methyltetrazolium, and bioluminescence, MitoTracker green and rhod-2 double-labeling. Membrane integrity and apoptosis were evaluated by measuring lactate dehydrogenase (LDH), caspase 3/7, and cleavage of cytokeratin 18 (CK18). Expression of mucin 2 (MUC2) was determined by cell-based ELISA. Acetaldehyde significantly increased reactive oxygen species generation and decreased mitochondrial function compared with negative controls (P < 0.05). In addition, acetaldehyde dose-dependently decreased ATP levels and induced intramitochondrial Ca(2+) accumulation compared with negative controls (P < 0.05). Furthermore, acetaldehyde induced LDH release and increased caspase3/7 activity and percentage of cells expressing cleaved CK18 and increased MUC2 protein expression compared with negative controls (P < 0.0001). ATP depletion and LDH release could be largely prevented by the antioxidant N-acetylcysteine, suggesting a pivotal role for oxidative stress. Our data demonstrate that acetaldehyde has distinct oxidant-dependent metabolic and cytotoxic effects on LS174T cells that can lead to induction of cellular apoptosis. These effects may contribute to acetaldehyde-induced intestinal barrier dysfunction and subsequently to liver injury.

Artemisinin protects against dextran sulfate-sodium-induced inflammatory bowel disease, which is associated with activation of the pregnane X receptor

Artemisinin has been used to treat malaria for centuries in the context of traditional Chinese medicine. In the present study, the effects of artemisinin on pregnane X receptor (PXR)-mediated CYP3A expression and its therapeutic role in inflammatory bowel disease were investigated. LS174T cells exposed to artemisinin at various concentrations and for different periods of time were examined with respect to the specific induction of CYP3A4 and PXR mRNA expression. Transient transfection experiments showed transcriptional activation of the CYP3A4 gene through artemisinin to be PXR-dependent. An electrophoretic-mobility shift assay (EMSA) showed that artemisinin activates the DNA-binding capacity of the PXR for the CYP3A4 element. These results indicate that the induction of CYP3A4 by artemisinin is mediated through the activation of PXR. Using animal models, it was demonstrated that artemisinin abrogates dextran sulfate sodium (DDS)-induced intestinal inflammation. Preadministration of artemisinin ameliorated the clinical hallmarks of colitis in DSS-treated mice as determined by body weight loss and assessment of diarrhea, rectal bleeding, colon length, and histology. Artemisinin was found to prevent or reduce the severity of colonic inflammation by inducing CYP3A expression by activation of PXR.

CD55 limits sensitivity to complement-dependent cytolysis triggered by heterologous expression of α-gal xenoantigen in colon tumor cells.

Engineering cancer cells to express heterologous antigen α-gal and induce the destruction of tumor cells depending on the complement cascade may be a promising strategy of tumor therapy. However, the feasibility and effect of using α-gal to induce colorectal adenocarcinoma cell line cytolysis is not yet known. In this study, we evaluated α-gal expression's ability to sensitize human colorectal adenocarcinoma cell lines to complement attack in cell lines LoVo, SW620, and Ls-174T. Nearly all α-gal-expressing LoVo and SW620 cells were killed by normal human serum (NHS), but α-gal-expressing Ls-174T cells showed no significant lysis. We analyzed the expression levels of membrane-bound complement regulatory proteins (mCRPs) on the three cell lines, and their protective role in α-gal-mediated activation of the complement. LoVo showed no expression of any of the three proteins. CD59 was strongly expressed by SW620 and Ls-174T. CD46 and CD55 varied between the two cell lines. CD46 on SW620 was only half the intensity of CD46 on Ls-174T. Ls-174T showed a notable expression of CD55, while expression of CD55 on SW620 was not detected. The sensitivity of Ls-174T expressing α-gal to NHS greatly increased following the downregulation of CD46 and CD55 with short hairpin RNA (shRNA). However, there is no increase in cell killing when CD59 expression was diminished. Our findings suggest that the use of α-gal as antigen to induce tumor cell killing may be a potential therapeutic strategy in colon cancer and that CD55 plays a primary role in conferring resistance to lysis.

Effects of dietary clays on performance and intestinal mucus barrier of broiler chicks challenged with Salmonella enterica serovar Typhimurium and on goblet cell function in vitro

In vivo and in vitro experiments were conducted to test for beneficial effects of dietary clays on broiler chicks challenged with Salmonella enterica serovar Typhimurium and to explore potential mechanisms. First, two hundred forty 1-d-old male broilers (initial BW: 41.6 ± 0.4 g) were allotted in a 2 × 4 factorial arrangement in a randomized complete block design. There were 2 infection treatments (with or without Salmonella) and 4 diets: basal (BAS), 0.3% smectite A (SMA), 0.3% smectite B, and 0.3% zeolite. The Salmonella reduced (P < 0.05) the growth rate of chicks fed the BAS, and feeding clay largely restored it (challenge × diet interaction, P < 0.05). Goblet cell number and size were increased (P < 0.05) by Salmonella in chicks fed the BAS and were reduced (P < 0.05) in Salmonella- challenged chicks by feeding SMA. Villus height was reduced by the Salmonella challenge in the chicks fed dietary clays (P < 0.01) but not in chicks fed the BAS (interaction P < 0.05). A human adenocarcinoma cell line (LS174T) was cultured in vitro in 3 separate experiments in the absence or presence of 3 concentrations (0.05, 0.10, and 0.50%) of SMA. Expression of mucin 2 (MUC2), resistin-like molecule β (RELMß), and trefoil factor 3 (TFF3) were determined by real-time reverse-transcription PCR. The expression of RELMβ was increased and expression of MUC2 was reduced (P < 0.05) by 0.10% SMA. Also, LS174T cells were cultured without or with SMA (0.05 and 0.10%) and the medium and cell lysate were analyzed for RELMβ using an immunoblot assay. Protein expression of RELMß in the cell lysate was reduced (P < 0.05) by SMA addition but increased in the medium, indicating that SMA increased secretion of RELMß, thus depleting the cell and concentrating this protein in the medium. In conclusion, the dietary clays restored the growth depression caused by Salmonella, and changes in goblet cell function may contribute to the benefits of one of the clays, specifically SMA.