15-deoxyprostaglandin-j2 and Colonic-Neoplasms

In human cells the length of telomeres depends on telomerase activity. This activity and the expression of the catalytic subunit of human telomerase reverse transcriptase (hTERT) is strongly up-regulated in most human cancers. hTERT expression is regulated by different transcription factors, such as c-Myc, Mad1 and Sp1. In this study, we demonstrated that 15d-PG J2 and rosiglitazone (an endogenous and synthetic peroxisome proliferators activated receptor gamma (PPARgamma) ligand, respectively) inhibited hTERT expression and telomerase activity in CaCo-2 colon cancer cells. Moreover, both ligands inhibited c-Myc protein expression and its E-box DNA binding activity. Additionally, Mad1 protein expression and its E-box DNA binding activity were strongly increased by 15d-PG J2 and, to a lesser extent, by rosiglitazone. Sp1 transcription factor expression and its GC-box DNA binding activity were not affected by both PPARgamma ligands. Results obtained by transient transfection of CaCo-2 cells with pmaxFP-Green-PRL plasmid constructs containing the functional hTERT core promoter (including one E-box and five GC-boxes) and its E-box deleted sequences, cloned upstream of the green fluorescent protein reporter gene, demonstrated that 15d-PG J2, and with minor effectiveness, rosiglitazone, strongly reduced hTERT core promoter activity. E-boxes for Myc/Mad/Max binding showed a higher activity than GC-boxes for Sp1. By using GW9662, an antagonist of PPARgamma, we demonstrated that the effects of 15d-PG J2 are completely PPARgamma independent, whereas the effects of rosiglitazone on hTERT expression seem to be partially PPARgamma independent. The regulation of hTERT expression by 15d-PG J2 and rosiglitazone, through the modulation of the Myc/Max/Mad1 network, may represent a new mechanism of action of these substances in inhibiting cell proliferation.

Topics: Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; Blotting, Western; Caco-2 Cells; Colonic Neoplasms; DNA, Neoplasm; Gene Expression Regulation, Neoplastic; Humans; Ligands; PPAR gamma; Promoter Regions, Genetic; Prostaglandin D2; Protein Binding; Proto-Oncogene Proteins c-myc; Repressor Proteins; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Rosiglitazone; Telomerase; Thiazolidinediones

The clinically relevant histone deacetylase inhibitors (HDI) valproic acid (VPA) and suberoylanilide hydroxamic acid exert variable antitumor activities but increase therapeutic efficacy when combined with other agents. The natural endogenous ligand of peroxisome proliferator-activated receptor gamma 15-deoxy-Delta(12,14)-prostaglandin J(2) (15d-PGJ(2)) is a potent antineoplastic agent. Therefore, we investigated whether these HDIs in combination with 15d-PGJ(2) could show synergistic antitumor activity in colon cancer DLD-1 cells.. Cell viability was determined using a Cell Counting Kit-8 assay. Apoptosis and reactive oxygen species (ROS) generation were determined using flow cytometry analysis. Western blotting and real-time reverse transcription-PCR analysis were carried out to investigate the expression of apoptosis-related molecules. Mice bearing DLD-1 xenograft were divided into four groups (n = 5) and injected everyday (i.p.) with diluent, VPA (100 mg/kg), 15d-PGJ(2) (5 mg/kg), or a combination for 25 days.. HDI/15d-PGJ(2) cotreatments synergistically induced cell death through caspase-dependent apoptosis in DLD-1 cells. Moreover, HDIs/15d-PGJ(2) caused histone deacetylase inhibition, leading to subsequent ROS generation and endoplasmic reticulum stress to decrease the expression of antiapoptotic molecules Bcl-X(L) and XIAP and to increase that of proapoptotic molecules CAAT/enhancer binding protein homologous protein and death receptor 5. Additionally, VPA/15d-PGJ(2) cotreatment induced ROS-dependent apoptosis in other malignant tumor cells and was more effective than a VPA or 15d-PGJ(2) monotherapy in vivo.. Cotreatments with the clinically relevant HDIs and the endogenous peroxisome proliferator-activated receptor gamma ligand 15d-PGJ(2) are promising for the treatment of a broad spectrum of malignant tumors.

Topics: Animals; Apoptosis; bcl-X Protein; Blotting, Western; Cell Line, Tumor; Cell Proliferation; Colonic Neoplasms; Drug Synergism; Histone Deacetylase Inhibitors; Humans; Hydroxamic Acids; Luciferases; Male; Mice; Mice, Inbred BALB C; Mice, Nude; Prostaglandin D2; Reactive Oxygen Species; Receptors, TNF-Related Apoptosis-Inducing Ligand; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; RNA, Small Interfering; Transcription Factor CHOP; Vorinostat; X-Linked Inhibitor of Apoptosis Protein

We found previously that X-linked inhibitor of apoptosis protein (XIAP), a potent endogenous inhibitor of apoptosis, is overexpressed in colon cancer. Ligand-induced activation of peroxisome proliferator-activated receptor gamma (PPARgamma) has been shown to exert proapoptotic and antiproliferative effects in many cancer cell types. However, neither XIAP down-regulation alone nor monotherapy using PPARgamma ligands is potent enough to control colon cancer. We explored whether XIAP inhibition and PPARgamma activation offer a synergistic anticancer effect in colon cancer. HCT116-XIAP(+/+) and HCT116-XIAP(-/-) cells were treated with troglitazone or 15-deoxy-Delta(12,14)-prostaglandin J(2) (15-PGJ(2)). Cell growth and apoptosis were measured. Nude mice were s.c. inoculated with HCT116 cells with or without oral troglitazone. Tumor growth, angiogenesis, and apoptosis were measured. Troglitazone- and 15-PGJ(2)-induced growth inhibition and apoptosis were more prominent in HCT116-XIAP(-/-) cells. Troglitazone- and 15-PGJ(2)-induced apoptosis correlated with enhanced cleavage of caspases and poly(ADP-ribose) polymerase, which were more profound in HCT116-XIAP(-/-) cells. Pretreatment of cells with XIAP inhibitor 1396-12 also sensitized HCT116-XIAP(+/+) cells to PPARgamma ligand-induced apoptosis. Troglitazone significantly retarded the growth of xenograft tumors, more significantly so in HCT116-XIAP(-/-) cell-derived tumors. Reduction of tumor size was associated with reduced expression of Ki-67, vascular endothelial growth factor, and CD31 as well as increased apoptosis. Loss of XIAP significantly sensitized colorectal cancer cells to PPARgamma ligand-induced apoptosis and inhibition of cell proliferation. Thus, simultaneous inhibition of XIAP and activation of PPARgamma may have a synergistic antitumor effect against colon cancer.

Topics: Apoptosis; Caspases; Cell Line, Tumor; Cell Proliferation; Cell Survival; Chromans; Colonic Neoplasms; Down-Regulation; Humans; Ki-67 Antigen; Ligands; Poly(ADP-ribose) Polymerases; PPAR gamma; Prostaglandin D2; Proteasome Endopeptidase Complex; Thiazolidinediones; Troglitazone; Vascular Endothelial Growth Factor A; X-Linked Inhibitor of Apoptosis Protein; Xenograft Model Antitumor Assays

We investigated whether the anticancer effect of a combination of XIAP down-regulation and PPAR gamma activation on colon cancer is PPARgamma receptor dependent. HCT116-XIAP(+/+) cells and HCT116-XIAP(-/-) cells were treated with troglitazone or 15-deoxy-Delta(12,14)-prostaglandin J2 (15-PGJ2) with or without prior exposure to PPARgamma inhibitor GW9662. Cell proliferation and apoptosis was evaluated. Athymic mice carrying HCT116-XIAP(-/-) cells-derived tumors were treated with troglitazone in the presence or absence of GW9662. Inhibition of cell proliferation and induction of apoptosis by troglitazone and 15-PGJ2 were more prominent in HCT116-XIAP(-/-) cells. PPARgamma ligand-induced growth inhibition, apoptosis, caspase and PARP cleavage could not be blocked by GW9662. Troglitazone significantly retarded growth of xenograft tumors and this effect was not blocked by GW9662. Marked apoptosis and an up-regulation of E-cadherin were observed in xenograft tumor tissues, and GW9662 did not affect these effects. Thus, a combination of XIAP down-regulation and PPARgamma ligands exert a significant anticancer effect in colon cancer via a PPARgamma independent pathway.

Topics: Anilides; Animals; Antineoplastic Agents; Apoptosis; Blotting, Western; Caspases; Chromans; Colonic Neoplasms; Down-Regulation; HCT116 Cells; Humans; Immunohistochemistry; Male; Mice; Mice, Inbred BALB C; PPAR gamma; Prostaglandin D2; Thiazolidinediones; Troglitazone; X-Linked Inhibitor of Apoptosis Protein

To compare effects of sulindac, PPARgamma activator and PPARgamma antagonist on the proliferation and apoptosis of the colonic cancer cells, and to investigate whether sulindac exerts its colonic neoplasm inhibiting activity through pathway of PPARgamma.. Cell strain HT-29 of colonic cancer was divided into six groups: the control group, sulindac group, 15d-PGJ2 (PPARgamma activator) group, GW9662 (PPARgamma antagonist) group, sulindac+GW9662 group and 15d-PGJ2+ GW9662 group. After 24 and 48 hours' culturing, proliferation status of each group was determined by immunocytochemical staining of PCNA, and cell apoptosis status was determined by double staining method of AnnexinV-FITC/PI, examined on flow cytometer.. (1) Proliferation status of the colonic cancer cells of each group: 24 and 48 hours after medication, PCNA positive ratios were 33.2%+/- 4.5% and 25.0%+/-4.7% of the control group, 11.8%+/-3.7% and 8.6%+/-1.9% of sulindac group, 11.2%+/-2.5% and 11.4%+/-2.1% of 15d-PGJ2 group, 35.3%+/-4.3% and 26.8%+/-3.9% of GW9662 group, 16.5%+/-5.3% and 12.2 %+/-2.4% of sulindac + GW9662 group, 21.0%+/-4.8% and 21.5%+/-4.2% of 15d-PGJ2+GW9662 group. (2) Apoptosis ratio of colonic cancer cells of each group: 24 hours after medication, apoptosis rate of colonic cancer cells was 13.0%+/-1.0% of the control group, 41.0%+/-2.6% of sulindac group, 11.5%+/-0.6% of 15d-PGJ2 group, 12.4%+/-0.9% of GW9662 group,33.6%+/-2.3% of sulindac+GW9662 group, and 13.0%+/-1.0% of 15d-PGJ2 + GW9662 group. 48 hours after medication, apoptosis rate was 14.0%+/-3.4% of the control group, 95.3%+/-1.5% of sulindac group, 31.5%+/-2.3% of 15d-PGJ2 group, 13.0%+/-1.9% of GW9662 group, 86.8%+/-0.4% of sulindac+GW9662 group, and 12.9%+/-1.0% of 15d-PGJ2+GW9662 group.. Both sulindac and PPARgamma activator can inhibit proliferation and promote apoptosis of colonic cancer cells, and their effects can be antagonized by PPARgamma antagonist, which indicates that as a kind of PPARgamma ligand, sulindac can inhibit proliferation of colonic cancer cells via activating PPARgamma.

Topics: Anilides; Antineoplastic Agents; Apoptosis; Cell Proliferation; Colonic Neoplasms; Flow Cytometry; HT29 Cells; Humans; Immunohistochemistry; PPAR gamma; Proliferating Cell Nuclear Antigen; Prostaglandin D2; Sulindac

PPARgamma ligands inhibit growth and induce apoptosis of various cancer cells. 4-Hydroxynonenal (HNE), a product of lipid peroxidation, inhibits proliferation and induces differentiation or apoptosis in neoplastic cells. The aim of this work was to investigate the effects of PPARgamma ligands (rosiglitazone and 15-deoxy-prostaglandin J2 (15d-PGJ2)) and HNE, alone or in association, on proliferation, apoptosis, differentiation, and growth-related and apoptosis-related gene expression in colon cancer cells (CaCo-2 cells). PPARgamma ligands inhibited cell proliferation (IC50 was 37.47+/-6.6 microM, for 15d-PGJ2, and 170.34+/-20 microM for rosiglitazone). HNE (1 microM) inhibited cell growth by 70%. Apoptosis was induced by 15d-PGJ2 and HNE and, to a minor extent, rosiglitazone. Differentiation was induced by rosiglitazone and by 15d-PGJ2, but not by HNE. PPARgamma ligands inhibited c-myc expression. HNE induced a transitory increase in c-myc expression and a subsequent down-regulation. HNE induced p21 expression, whereas PPARgamma ligands did not. Expression of the bax gene was increased by HNE and 15d-PGJ2, but not by rosiglitazone. No synergism or antagonism was found between HNE and PPARgamma ligands. Both apoptosis and differentiation induction may be responsible for the inhibition of proliferation by PPARgamma ligands; apoptosis and c-myc and p21 expression seem to be involved in the inhibition of proliferation by HNE.

Topics: Aldehydes; Apoptosis; bcl-2-Associated X Protein; Caco-2 Cells; Cell Differentiation; Cell Proliferation; Colonic Neoplasms; Cross-Linking Reagents; Cysteine Proteinase Inhibitors; Drug Synergism; Gene Expression; Humans; Ligands; PPAR gamma; Prostaglandin D2; Rosiglitazone; Thiazolidinediones

15-Deoxy-Delta(12,14) prostaglandin J2 (15d-PGJ2) is a natural ligand for the peroxisome proliferator-activated receptor gamma (PPARgamma) that exhibits antiproliferative activity in colon cancer cells, but its mechanism of action is still poorly understood. In this study, we showed that Krüppel-like factor 4 (KLF4) is one of the downstream effectors of 15d-PGJ2. Treatment of HT-29 cells with 15d-PGJ2 resulted in up-regulation of both KLF4 mRNA and protein expression, and these increases were also observed in other colon cancer cell lines. Down-regulation of KLF4 expression by small interfering RNA (siRNA) targeting KLF4 reduced 15d-PGJ2-mediated G1 phase arrest, suggesting that KLF4-mediated function of 15d-PGJ2. The effect of 15d-PGJ2 on KLF4 expression seems not to involve its nuclear receptor PPARgamma, in that our data show that:1) KLF4 gene promoter does not contain putative PPRE sequence, 2) 15d-PGJ2 rapidly activates extracellular signal-regulated kinase (ERK) and induces KLF4 mRNA expression, 3) KLF4 is induced by 15d-PGJ2 but not by rosiglitazone, a synthetic PPARgamma ligand, and 4) 15d-PGJ2 is unable to stimulate PPAR-dependent promoter activity in the absence of cotransfected PPARgamma. Moreover, 15d-PGJ2-mediated KLF4 mRNA expression was blocked by 2'-amino-3'-methoxyflavone (PD98059) or 1,4-diamino-2,3-dicyano-1,4-bis(methylthio)butadiene (U0126), two ERK kinase MAP inhibitors, whereas the phosphoinositol-3 kinase inhibitors wortmannin and 2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one (LY294002) had no such effect. Furthermore, KLF4 induction by 15d-PGJ2 occurred only in signal transducer and activator of transcription 1 (STAT1)-expressing, not in STAT1-knockout cells. Together, these results suggest that 15d-PGJ2-induced growth inhibition of colon cancer cells is mediated, at least in part, through up-regulation of KLF4 expression. This induction is unlikely to be mediated through the PPARgamma receptor but may involve the mitogen-activated protein kinase kinase/ERK pathway and is STAT1-dependent.

Topics: Caco-2 Cells; Cell Proliferation; Colonic Neoplasms; DNA; Extracellular Signal-Regulated MAP Kinases; G1 Phase; Gene Expression Regulation; HT29 Cells; Humans; Kruppel-Like Factor 4; Kruppel-Like Transcription Factors; MAP Kinase Signaling System; Phosphorylation; PPAR gamma; Prostaglandin D2; RNA, Messenger; RNA, Small Interfering; Up-Regulation