okadaic-acid and Adenocarcinoma

Obesity increases the risk of developing several cancers including oesophageal adenocarcinoma (OAC). Obesity is characterised by hyperleptinaemia and hypoadiponectinaemia: we have hypothesised that these hormonal factors may contribute to the progression of OAC. We have examined the effects of leptin and adiponectin on proliferation of OAC cells. Leptin-stimulated proliferation in four different OAC lines (OE33, OE19, BIC-1 and FLO) and this was inhibited by globular but not full length adiponectin. All four OAC lines expressed both adiponectin-receptor isoforms (AdipoR1 and AdipoR2). Globular adiponectin also inhibited leptin-induced proliferation in rat IEC-18 cells which only expressed AdipoR1. Specific inhibitors of 5'-AMP-activated protein kinase (Compound C) and serine/threonine phosphatases (okadaic acid) and a specific siRNA to AdipoR1 blocked the anti-proliferative effects of adiponectin. Adiponectin inhibited leptin-induced Akt phosphorylation; this action was sensitive to okadaic acid but not to Compound C. Adiponectin deficiency may contribute to the promotion of OAC in obesity.

Topics: Adenocarcinoma; Adiponectin; AMP-Activated Protein Kinases; Animals; Cell Line, Tumor; Cell Proliferation; Enzyme Activation; Enzyme Inhibitors; Esophageal Neoplasms; Humans; Leptin; Multienzyme Complexes; Obesity; Okadaic Acid; Protein Isoforms; Protein Serine-Threonine Kinases; Proto-Oncogene Proteins c-akt; Pyrazoles; Pyrimidines; Rats; Receptors, Adiponectin; RNA Interference

Butyric acid is well recognized as a histone deacetylase (HDAC) inhibitor, and changes in histone acetylation are thought to alter gene expression. The mechanism by which sodium butyrate (NaB) induces p21WAF1/CIP1, a critical gene involved in the antiproliferative effect of NaB, was studied at the chromatin level. Using chromatin immunoprecipitation (ChIP) assay, acetylation of histone H3 was observed at the proximal region of the promoter within 30 min of NaB exposure and this extended to the distal region within 2 hr. By contrast, histone H4 was acetylated both at the proximal and the distal regions of the promoter within 30 min. NaB did not influence other histone modifications. NaB stimulated recruitment of the transcription factors ZBP89 and Sp1 as well as GCN5, but did not influence recruitment of Sp3, HDAC1, p300, or CBP. As recruitment of HDAC1 to the promoter appeared not to account for NaB-induced changes in histone acetylation, we aimed to influence HDAC activity by altering its phosphorylation status. The kinase inhibitor, H7, suppressed p21WAF1/CIP1 mRNA in both the absence and the presence of NaB without influencing the butyrate-induced hyperacetylation of H3 and H4 associated with the p21WAF1/CIP1 promoter. These results suggest that acetylation of histones at the p21WAF1/CIP1 promoter is not sufficient for NaB to exert antiproliferative effects via transcription of the p21WAF1/CIP1 gene. Induction of p21WAF1/CIP1 transcription by the phosphatase inhibitor, okadaic acid, in the absence of changes in association of acetylated histones with the p21WAF1/CIP1 promoter provides further evidence of the importance of phosphorylation to p21WAF1/CIP1 transcription.

Topics: Acetylation; Adenocarcinoma; Butyrates; Cell Division; Chromatin; Colorectal Neoplasms; Cyclin-Dependent Kinase Inhibitor p21; Cyclins; Gene Expression Regulation, Neoplastic; Histones; Humans; Okadaic Acid; Phosphorylation; Precipitin Tests; RNA, Messenger; Transcription Factors; Transcription, Genetic; Transcriptional Activation; Tumor Cells, Cultured

Previous studies have demonstrated that several splice variants are derived from both the caspase 9 and Bcl-x genes in which the Bcl-x splice variant, Bcl-x(L) and the caspase 9 splice variant, caspase 9b, inhibit apoptosis in contrast to the pro-apoptotic splice variants, Bcl-x(s) and caspase 9. In a recent study, we showed that ceramide induces the dephosphorylation of SR proteins, a family of protein factors that regulate alternative splicing. In this study, the regulation of the alternative processing of pre-mRNA of both caspase 9 and Bcl-x(L) was examined in response to ceramide. Treatment of A549 lung adenocarcinoma cells with cell-permeable ceramide, D-e-C(6) ceramide, down-regulated the levels of Bcl-x(L) and caspase 9b mRNA and immunoreactive protein with a concomitant increase in the mRNA and immunoreactive protein levels of Bcl-x(s) and caspase 9 in a dose- and time-dependent manner. Pretreatment with calyculin A (5 nm), an inhibitor of protein phosphatase-1 (PP1) and protein phosphatase 2A (PP2A) blocked ceramide-induced alternative splicing in contrast to okadaic acid (10 nm), a specific inhibitor of PP2A at this concentrations in cells, demonstrating a PP1-mediated mechanism. A role for endogenous ceramide in regulating the alternative splicing of caspase 9 and Bcl-x was demonstrated using the chemotherapeutic agent, gemcitabine. Treatment of A549 cells with gemcitabine (1 microm) increased ceramide levels 3-fold via the de novo sphingolipid pathway as determined by pulse labeling experiments and inhibition studies with myriocin (50 nm), a specific inhibitor of serine palmitoyltransferase (the first step in de novo synthesis of ceramide). Treatment of A549 cells with gemcitabine down-regulated the levels of Bcl-x(L) and caspase 9b mRNA with a concomitant increase in the mRNA levels of Bcl-x(s) and caspase 9. Again, inhibitors of ceramide synthesis blocked this effect. We also demonstrate that the change in the alternative splicing of caspase 9 and Bcl-x occurred prior to apoptosis following treatment with gemcitabine. Furthermore, doses of D-e-C(6) ceramide that induce the alternative splicing of both caspase 9 and Bcl-x-sensitized A549 cells to daunorubicin. These data demonstrate a role for protein phosphatases 1 (PP1) and endogenous ceramide generated via the de novo pathway in regulating this mechanism. This is the first report on the dynamic regulation of RNA splicing of members of the Bcl-2 and caspase families in response to regulator

Topics: Adenocarcinoma; Alternative Splicing; Base Sequence; bcl-X Protein; Carboxylic Acids; Caspase 9; Caspases; Ceramides; DNA Primers; Enzyme Inhibitors; Fumonisins; Humans; Lung Neoplasms; Marine Toxins; Okadaic Acid; Oxazoles; Phosphoprotein Phosphatases; Protein Phosphatase 1; Protein Phosphatase 2; Proto-Oncogene Proteins c-bcl-2; Sphingolipids; Tumor Cells, Cultured

LoVo adenocarcinoma cells are fairly sensitive to cytostatic drugs, e.g. doxorubicin, but can develop drug resistance by expression of a P-glycoprotein-mediated MDR1 phenotype. LoVo cells respond with apoptosis to nanomolar concentrations of okadaic acid and micromolar concentrations of cantharidic acid. Interestingly, LoVoDx cells which had become about 10-fold less sensitive to doxorubicin by incubation in increasing concentrations of this cytostatic drug were also less sensitive to the toxicity of okadaic acid. Resistance to both agents was lost or significantly reduced by incubation in drug-free medium for about 4 months. On the other hand, LoVoDx cells did not lose responsiveness to the structurally different phosphatase inhibitor cantharidic acid but were about twofold more sensitive to the cytotoxic effect of this agent. Thus, MDR expression protects LoVo cells from the toxicity of phosphatase inhibitors that presumably are substrates of the P-glycoprotein, e.g. okadaic acid and its derivatives but not cantharidic acid, despite the fact that both agents are potent inducers of apoptotic cell death via ser/thr phosphatase inhibition.

Topics: Adenocarcinoma; Animals; Apoptosis; ATP Binding Cassette Transporter, Subfamily B, Member 1; Cantharidin; Cells, Cultured; Doxorubicin; Enzyme Inhibitors; Okadaic Acid; Phosphoprotein Phosphatases; Rats

8-Cl-cAMP and 8-NH2-cAMP induced MCF-7 cell death. The type(s) of cell death were studied in more detail and compared with the cell death type (apoptosis) induced by okadaic acid, an inhibitor of serine/threonine phosphatases. By morphological criteria dying cells showed loss of cell-cell interactions and microvilli, condensation of nuclear chromatin and segregation of cytoplasmic organelles. By in situ nick end-labelling, using digoxigenin-conjugated dUTP as probe, a large fraction of 8-Cl-cAMP, 8-NH2-cAMP and 8-Cl-adenosine-exposed cells stained positively in the advanced stages of death. In the early phase of chromatin condensation the cells stained negatively. Specific (internucleosomal) DNA fragmentation was not observed. The MCF-7 cell death induced by 8-Cl-cAMP and 8-NH2-cAMP was not mediated by activation of the cAMP kinase since more stable cAMP analogues (8-CPT-cAMP and N6-benzoyl-cAMP) or forskolin failed to induce death. Furthermore, 8-Cl-cAMP action was counteracted by adenosine deaminase and 3-isobutyl-1-methylxanthine, and mimicked by 8-Cl-adenosine, a major metabolite of 8-Cl-cAMP. It is concluded that 8-Cl- and 8-NH2-cAMP can induce morphological and biochemical effects resembling apoptotic cell death in MCF-7 cells through their conversion into potent cytotoxic metabolite(s).

Topics: 1-Methyl-3-isobutylxanthine; 8-Bromo Cyclic Adenosine Monophosphate; Adenocarcinoma; Adenosine Deaminase; Amino Acid Sequence; Apoptosis; Biotransformation; Breast Neoplasms; Chromatin; Colforsin; Cyclic AMP; Cyclic AMP-Dependent Protein Kinases; DNA Damage; Ethers, Cyclic; Female; Humans; Marine Toxins; Microvilli; Molecular Sequence Data; Necrosis; Okadaic Acid; Organelles; Oxazoles; Phosphoprotein Phosphatases

Butyrate is a potent differentiating agent present in high concentrations in colonic lumen as a result of metabolic breakdown of dietary fibre and, as such, may directly influence colonic cancer progression. We have investigated the effects of butyrate on an enzyme system important in colonic tumour progression, the plasminogen-activating system, in a poorly differentiated colon cancer cell. Butyrate was found to induce a rapid and transient increase in plasminogen activator inhibitor type 1 (PAI-1) mRNA while concomitantly suppressing the constitutive production of both urokinase-type plasminogen activator (uPA) and uPA receptor (uPAR) mRNA transcripts. We have investigated the mechanisms involved in mediating these effects by run-on transcription and RNA stability analyses. Our data show that PAI-1 mRNA induction occurs through both regulation of the stability of the alternately spliced 3.3 kb PAI-1 mRNA transcript and induction of the 2.4 kb PAI-1 mRNA transcript. Studies using modulators of signal transduction pathways demonstrate that induction of PAI-1 mRNA synthesis is independent of protein kinase C but dependent on the activation of protein kinase A. Suppression of uPA mRNA by butyrate was found to occur by down-regulation of gene transcription through a process independent of de novo protein synthesis. The transcription rate of the uPAR gene was not modulated by butyrate, but rapid turnover of the uPAR gene by butyrate was dependent on ongoing protein synthesis. Our results demonstrate that butyrate can effect rapid changes in the expression of genes of the plasminogen-activating system through several different mechanisms in a gene-specific manner.

Topics: Adenocarcinoma; Butyrates; Colonic Neoplasms; Cyclic AMP-Dependent Protein Kinases; Cycloheximide; Down-Regulation; Ethers, Cyclic; Gene Expression Regulation, Neoplastic; In Vitro Techniques; Okadaic Acid; Plasminogen Activator Inhibitor 1; Protein Kinase C; Receptors, Cell Surface; Receptors, Urokinase Plasminogen Activator; RNA, Messenger; RNA, Neoplasm; Signal Transduction; Transcription, Genetic; Tumor Cells, Cultured; Urokinase-Type Plasminogen Activator

To understand the transcriptional regulation of the human insulin-like growth factor II (IGF-II) gene, we examined the effects of okadaic acid, a potent in vitro inhibitor of protein phosphatases, on the activation of human IGF-II gene expression. Treatment of A-549 human lung adenocarcinoma cells with okadaic acid increased expression of the IGF-II mRNAs. Since the 4.8-kb mRNA is transcribed under the control of human IGF-II P4 promoter, we examined the P4 promoter element responsible for the okadaic acid-mediated transcriptional activation. Transfection of IGF-II P4 promoter-chloramphenicol acetyltransferase constructs demonstrated that the effects of okadaic acid on the induction of IGF-II gene expression are mediated through multiple promoter elements, including an Egr-1 consensus element. We have also shown that okadaic acid induced the expression of the transcription factor Egr-1. Moreover, by using a GAL4-Egr-1 fusion protein, we have directly demonstrated that okadaic acid positively regulates Egr-1 transcriptional activity in vivo. These results indicate that protein phosphatases play an important role in the transcriptional regulation of the IGF-II.

Topics: Adenocarcinoma; Base Sequence; Chloramphenicol O-Acetyltransferase; DNA; DNA-Binding Proteins; Early Growth Response Protein 1; Ethers, Cyclic; Gene Expression Regulation; Humans; Immediate-Early Proteins; Insulin-Like Growth Factor II; Lung Neoplasms; Molecular Sequence Data; Okadaic Acid; Phosphoprotein Phosphatases; Promoter Regions, Genetic; Protein Processing, Post-Translational; RNA, Messenger; Transcription Factors; Transcription, Genetic; Tumor Cells, Cultured

We have investigated the regulation of the intestinal mucin gene MUC2 in HT29 cells. Surprisingly, sodium butyrate, an effective inducer of aspects of colonic cell differentiation in HT29 cells, fails to induce MUC2 during short-term exposure, despite the fact that it has been used to select stably differentiated clones of HT29 that resemble goblet cells and produce mucin. However, 12-O-tetradecanoylphorbol-13-acetate and forskolin, which trigger the protein kinase C- and A-dependent signal transduction pathways, respectively, are potent inducers of MUC2 gene expression. 12-O-Tetradecanoylphorbol-13-acetate and forskolin operate through distinct mechanisms, with the former requiring de novo protein synthesis and the latter not. Experiments using specific protein kinase inhibitors suggest that both inducers operate by triggering their respective signal transduction pathways. Nuclear runoff analyses suggest that post-transcriptional (rather than transcriptional) mechanisms are important in the accumulation of MUC2 mRNA. Finally, we show that in several cell lines from human mucinous tumors, characterized by elevated levels of mucin production, MUC2 expression is very high and constitutive compared to forskolin-treated HT29 cells. Thus, the different regulation of MUC2 in HT29 cells and in mucinous tumor cell lines may reflect molecular pathways that characterize colon carcinomas of different histology and pathology.

Topics: 1-Methyl-3-isobutylxanthine; Adenocarcinoma; Bucladesine; Calcimycin; Colforsin; Colonic Neoplasms; DNA Probes; Ethers, Cyclic; Gene Expression Regulation, Neoplastic; Humans; Intestinal Mucosa; Ionomycin; Ionophores; Kinetics; Mucins; Okadaic Acid; RNA, Messenger; RNA, Neoplasm; Tetradecanoylphorbol Acetate; Transcription, Genetic; Tumor Cells, Cultured

The aim of the present study was to elucidate the mechanism responsible for the high mannose glycoprotein instability in undifferentiated HT-29 cells (a human colon cancer cell line) reported previously. The results presented here are consistent with lysosomal degradation of these molecular species. In addition inhibitors of the autophagic-lysosomal degradative pathway (3-methyladenine, okadaic acid and asparagine) dramatically block the degradation of proteins and N-linked glycoproteins in undifferentiated HT-29 cells. The main conclusions of this work are: 1- the autophagic-lysosomal pathway is responsible for the high mannose glycoprotein degradation in undifferentiated HT-29 cells; 2- this degradative pathway exists in differentiated cells but is greatly reduced (3.5-4 fold); 3- the HT-29 cell line is a new model to investigate the molecular regulation of autophagy.

Topics: Adenine; Adenocarcinoma; Asparagine; Autophagy; Carbon Radioisotopes; Carcinogens; Cell Differentiation; Cell Line; Chloroquine; Colonic Neoplasms; Ethers, Cyclic; Glycoproteins; Humans; Kinetics; Leucine; Lysosomes; Mannose; Okadaic Acid; Polysaccharides; Tritium; Tumor Cells, Cultured

A novel non-phorbol-ester-like tumor promoter, okadaic acid (OA) has been shown to be an inhibitor of protein phosphatase I and IIA and, thus, to cause an "apparent activation" of protein kinase C (PKC). We previously showed that cis-diamminedichloroplatinum(II) (CDDP)-resistant cells, PC-9/CDDP, were cross-resistant to OA and that the cross-resistance was not due to the increased efflux of OA. We hypothesized that the phosphorylation status of some cellular proteins might be important in CDDP-resistance. No significant difference in PKC activity or total protein phosphatase activity measured in vitro was seen between PC-9 and PC-9/CDDP cells, nor in their sensitivity to inhibition by OA, nor in the amount of phosphorylation of whole cells or TCA-insoluble material. By SDS-PAGE after incubation of intact cells with 32P, we detected a marked increase, compared to PC-9 cells, in phosphorylation of the nuclear proteins of MW 32 and 20 kDa in CDDP-resistant PC-9/CDDP cells with no apparent difference in protein content. When phosphorylation of nuclear proteins observed in PC-9/CDDP cells was analyzed by 2-dimensional SDS-PAGE, the 32-kDa protein had a PI of about 4.5. The 32-kDa and 20-kDa bands were increased in a dose-dependent manner by CDDP treatment. On the other hand, no increase in phosphorylation of these proteins was observed in parental PC-9 cells. These results demonstrate a marked difference in the phosphorylation status of specific nuclear proteins between parental and CDDP-resistant cell lines, which may be related to CDDP-resistance.

Topics: Adenocarcinoma; Cell Nucleus; Cisplatin; Drug Resistance; Electrophoresis, Gel, Two-Dimensional; Ethers, Cyclic; Humans; Lung Neoplasms; Molecular Weight; Nuclear Proteins; Okadaic Acid; Phosphoprotein Phosphatases; Phosphoproteins; Phosphorylation; Protein Kinase C; Tetradecanoylphorbol Acetate; Time Factors; Tumor Cells, Cultured