Expression of peroxisome proliferator-activated receptor (PPAR)gamma in gastric cancer and inhibitory effects of PPARgamma agonists

Growth inhibition and apoptosis induced in human leiomyoma cells by treatment with the PPAR gamma ligand ciglitizone

The nuclear receptors PPARs (peroxisome proliferator-activated receptors) are transcription factors that play important roles in multiple disease conditions. The activation of PPARs by specific ligands is associated with growth suppression of several different types of human cancer, but the molecular mechanism responsible for this growth suppressive effect remains elusive. The aim of this study was to determine the distribution of PPARgamma protein/mRNA expression in uterine leiomyomas and to identify the PPARgamma induced signaling pathways responsible for the growth inhibition induced by treatment with ciglitizone, a synthetic ligand of PPARgamma, in view of identifying targets that could possibly affect the viability and proliferation of uterine leiomyoma cells. Dose-response studies on proliferation found that uterine leiomyoma was more sensitive to inhibition by ciglitizone treatments than normal myometrium. We also found that ciglitizone significantly stimulated gene expression driven by a PPAR-responsive element in cultured leiomyoma cells and reduced the survival of leiomyoma cells relative to the control cells. The reduced survival of ciglitizone treated leiomyoma cells resulted from a mechanism that involved the Fas receptor-mediated apoptosis signaling cascade. These results suggest that uterine leiomyomas growth and differentiation might be modulated through PPARgamma receptors and that PPARgamma ligands may be of potential use for uterine leiomyoma treatment.

Inhibitory effect of meloxicam, a selective cyclooxygenase-2 inhibitor, and ciglitazone, a peroxisome proliferator-activated receptor gamma ligand, on the growth of human ovarian cancers

BACKGROUND

It was recently reported that high expression of peroxisome proliferator-activated receptor gamma (PPARgamma) and low expression of cyclooxygenase-2 (COX-2) might be involved in the inhibition of ovarian tumor progression and confirmed that PPARgamma activation could suppress COX-2 expression via the nuclear factor-kappaB pathway in ovarian cancer cells.

METHODS

The current study investigated whether meloxicam, a selective COX-2 inhibitor, and ciglitazone, a ligand for PPARgamma, inhibit the growth of human ovarian cancer cell lines and aimed to elucidate the molecular mechanism of their antitumor effect. Tumor growth and survival were examined in female nu/nu mice xenografted with subcutaneous OVCAR-3 tumors or with intraperitoneal DISS tumors and treated with meloxicam (162 ppm in diet, every day) or ciglitazone (15 mg/kg intraperitoneally once a week).

RESULTS

Both meloxicam and ciglitazone treatments significantly suppressed the growth of OVCAR-3 tumors xenotransplanted subcutaneously and significantly prolonged the survival of mice with malignant ascites derived from DISS cells as compared with controls. Meloxicam treatment decreased COX-2 expression in tumors by 2.5-fold compared with that observed in untreated tumors. Although ciglitazone treatment did not alter COX-2 expression in tumors, it reduced the expression of microsomal prostaglandin (PG) E synthase, which converts COX-derived PGH(2) to PGE(2). Both meloxicam and ciglitazone decreased PGE(2) levels in serum as well as in ascites. Reduced microvessel density and induced apoptosis were found in solid OVCAR-3 tumors treated with either meloxicam or ciglitazone.

CONCLUSIONS

These results indicate that both meloxicam and ciglitazone produce antitumor effects against ovarian cancer in conjunction with reduced angiogenesis and induction of apoptosis.

AMACR is highly expressed in gastric adenomas and intestinal-type carcinomas

Alpha-methylacyl-CoA racemase (AMACR) is a novel tumor biomarker expressed in a number of neoplasms, including colorectal and prostatic adenocarcinomas. However, AMACR expression has not been investigated in preneoplastic and neoplastic lesions of the stomach. Using immunohistochemistry we studied the expression of AMACR in normal gastric mucosa (n=32), intestinal metaplasia (n=26), adenomas (n=29) and adenocarcinomas (n=132) of the stomach from 135 patients. Synchronous adenocarcinomas arising in the background of adenomas were observed in 26 cases. AMACR immunoreactivity was not observed in all normal gastric mucosa. Tissue from intestinal metaplasia, adenomas, and adenocarcinomas was positive in 7.7% (2/26), 79.3% (23/29), and 62.9% (83/132) of cases, respectively. The difference in AMACR expression between adenomas or adenocarcinomas and non-neoplastic mucosa was statistically significant (p=0.0001). Moreover, intestinal-type carcinomas showed significantly higher expression of AMACR (69.8%) compared to diffuse-type carcinomas (47.2%) (p=0.02). Our results indicate that as well as being an additional diagnostic tool, altered AMACR expression in gastric adenomas and intestinal-type carcinomas suggests that AMACR may be involved early in the development of intestinal-type gastric carcinomas.

Present concepts and future outlook: function of peroxisome proliferator-activated receptors (PPARs) for pathogenesis, progression, and therapy of cancer

Peroxisome proliferator-activated receptors (PPARs) are members of the nuclear receptor superfamily of transcriptional regulators that regulate lipid, glucose, and amino acid metabolism. In recent studies it also has been shown that these receptors are implicated in tumor progression, cellular differentiation, and apoptosis and modulation of their function is therefore considered as a potential target for cancer prevention and treatment. PPAR ligands and other agents influencing PPAR signalling pathways have been shown to reveal chemopreventive potential by mediating tumor suppressive activities in a variety of human cancers and could represent a potential novel strategy to inhibit tumor carcinogenesis and progression. This review summarizes the currently available data on the roles of PPARs in relation to the processes of cell differentiation and carcinogenesis as well as their role as promising future therapeutic targets.

Expression of a peroxisome proliferator-activated receptor gamma 1 splice variant that was identified in human lung cancers suppresses cell death induced by cisplatin and oxidative stress

PURPOSE

The activation of peroxisome proliferator-activated receptor gamma (PPAR gamma) has been implicated in the inhibition of tumor progression in lung cancers through the induction of differentiation and apoptosis. Recently, we identified a novel splice variant of human PPAR gamma1 (hPPAR gamma1) that exhibits dominant-negative activity in human tumor-derived cell lines. This study aimed to examine the expression and pathophysiologic roles of a truncated splice variant of hPPAR gamma1 (hPPAR gamma1(tr)) in primary human lung cancer tissues.

EXPERIMENTAL DESIGN

The expression and localization of hPPAR gamma1(tr) was surveyed in human primary lung cancer tissues using immunohistochemistry and Western blot analysis. Using transfectants stably expressing wild-type hPPAR gamma1 (hPPAR gamma1(wt)) and hPPAR gamma1(tr), we also analyzed the pathophysiologic roles of hPPAR gamma1(tr).

RESULTS

We showed that PPAR gamma is expressed predominantly in the nucleus of nontumorous tissues, whereas it is present in both the nucleus and the cytoplasm of tumorous tissues in squamous cell carcinoma (SCC) of the lung. Western blot analysis confirmed the presence of PPAR gamma1(tr) in primary lung SCC tissue but not in nontumorous tissue. Expression of PPAR gamma1(tr) in Chinese hamster ovary cells attenuated their susceptibility to cell death induced by oxidative stress or cisplatin, whereas their susceptibility was completely recovered by down-regulation of PPAR gamma1(tr) with small interfering RNA.

CONCLUSIONS

hPPAR gamma1(tr) is expressed strongly in tumorous tissues of primary human lung SCC and its overexpression renders transfected cells more resistant to chemotherapeutic drug- and chemical-induced cell death. These data suggest that the decreased drug sensitivity of PPAR gamma1(tr)-expressing cells may be associated with increased tumor aggressiveness and poor clinical prognosis of patients.

Regulation of prostate cancer cell growth and PSA expression by angiotensin II receptor blocker with peroxisome proliferator-activated receptor gamma ligand like action

BACKGROUND

We previously reported that angiotensin II (AII) activated the proliferation of prostate cancer cells, and its antagonist, an AII receptor type 1 (AT1R) blocker (ARB), inhibited the proliferation of prostate cancer in vitro and in vivo. In the present study, we investigated whether telmisartan, an ARB, has a unique feature as a peroxisome proliferator-activated receptor gamma (PPARgamma) ligand, and its suppressive potential on prostate cancer cells.

METHODS

Cell count or MTT assay were carried out for growth suppression of prostate cancer cells. Phosphorylation of mitogen-activated protein kinase (MAPK), specific expression of prostate specific antigen (PSA) and AT1R were investigated by western blot. To confirm the PPARgamma activity of ARBs, luciferase assay using PSA promoter and PPARgamma response elements (PPRE) plasmids was performed.

RESULTS

The results showed that cell proliferation and signal transduction were inhibited by telmisartan treatment. Also, inhibition of PSA expression by telmisartan was confirmed by western blot and luciferase assay, indicating that an ARB acted in a similar way such as an anti-androgenic agent in prostate cancer cells.

CONCLUSION

The present study showed ARBs, especially those possessing a PPARgamma ligand-like structure, have a potential antagonistic effect on androgen-dependent and -independent prostate cancer.

Peroxisome proliferator-activated receptor gamma agonists inhibit the proliferation and invasion of human colon cancer cells

BACKGROUND AND AIMS

Data regarding the effect of peroxisome proliferator-activated receptor gamma (PPAR-gamma) ligands on the invasive ability of colon cancer cells are currently limited. This study was designed to examine the effects of PPAR-gamma agonists on the proliferation and invasion of two colon cancer cells to identify the role of PPAR-gamma in colon cancer growth and metastasis.

METHODS

SW480 and LS174T cells were treated with PPAR-gamma ligands, pioglitazone and 15-deoxy-delta(12,14)-prostaglandin J2 (15d-PGJ2), as well as their combinations with the PPAR-gamma antagonist GW9662. MTT assay was used to determine the antiproliferative effects. Cell cycle analysis was conducted by flow cytometry. The mRNA and protein expression were detected by reverse transcriptase polymerase chain reaction (RT-PCR) and western blot, respectively. The invasive ability of cells was determined by the BD BioCoat Matrige invasion chamber.

RESULTS

Pioglitazone and 15d-PGJ2 inhibited the proliferation of both colon cancer cell lines in a dose-dependent manner. This growth inhibitory effect was reversed by GW9662. Results from flow cytometry demonstrated G1 arrest following treatment with pioglitazone and 15d-PGJ2. The expression of matrix metalloproteinase-7 (MMP-7) was only detected in LS174T cells, while its tissue inhibitor-1 (TIMP-1) was expressed in both colon cancer cells. 15d-PGJ2 and pioglitazone downregulated MMP-7 expression and upregulated TIMP-1 expression. PPAR-gamma agonists can only inhibit invasive activity of LS174T cells.

CONCLUSIONS

PPAR-gamma agonists have inhibitory effects on the proliferation of colon cancer cell lines associated with G1 cell cycle arrest and invasive activity. The latter effect is demonstrated in certain cell lines through the down-regulation of MMP-7 synthesis.

Activation of peroxisome proliferator-activated receptor gamma inhibits cell growth via apoptosis and arrest of the cell cycle in human colorectal cancer

OBJECTIVE

To investigate the expression of peroxisome proliferator-activated receptors (PPAR)gamma and the effects of PPARgamma ligands on cells growth in colorectal cancer (CRC) cell line HT-29, and to explore whether the activation of PPARgamma by its selective ligand can induce apoptosis and the arrest of the cell cycle in these cells.

METHODS

A CRC cell line, HT-29, was used in this study. PPARgamma mRNA and the protein expressions were measured by reverse transcriptase-polymerase chain reaction and Western blot. The HT-29 cells were treated with two specific PPARgamma ligands: rosiglitazone and 15-d-PGJ2. The effects of PPARgamma activated by rosiglitazone and 15-d-PGJ2 on the anchorage-dependent and anchorage-independent growth of the cells were assessed by methylthiazolyl terazolium (MTT) and soft agar colony assay, respectively. Apoptosis was measured by TUNEL staining and flow cytometry (FCM) assay by CaspSCREEN Flowcytometric Apoptosis Detection Kit (BioVision, Palo Alto, USA). Furthermore, the caspase-3 expression was determined by a immunocytochemical staining method before and after treatment with rosiglitazone and 15-d-PGJ2 for 48 h. The cell cycles were measured by flow cytometric analysis using propidium iodide (PI).

RESULTS

PPARgamma mRNA and protein expressions were observed in the HT-29 cells. The MTT assay showed that treatment of these cells with 0, 0.1, 1 or 10 micromol/L PPARgamma activators rosiglitazone or 15-d-PGJ2 for 0, 24, 48 or 72 h resulted in the inhibition of anchorage-dependent cell growth in a dosage- and time-dependent way. Rosiglitazone treatment during cell growth resulted in the reduction of colony formation and the effects were not immediately reversible in the cell culture. TUNEL staining showed DNA fragmentation in positive cells after treatment with rosiglitazone and 15-d-PGJ2 for 48 h. In addition, FCM showed that the apoptosis rates were 14.8+/-0.8% and 28.5+/-1.3% or 15+/-0.7% and 40+/-1.2% after the cells were incubated with 10 micromol/L rosiglitazone or 15-d-PGJ2 for 24 h and 48 h, while the apoptosis rates of cells without treatment were 3.8+/-0.4% and 8.8+/-0.4%, respectively. Consistent with these results, the positivity rates of caspase-3 expression in cells treated with rosiglitazone or 15-d-PGJ2 increased significantly when compared with the control group. To explore whether the regulation of the cell cycle was involved in the effect of PPARgamma ligands on cell growth, FCM using PI staining was assessed. The ratio of G0/G1 phase cells increased after incubated with 10 micromol/L rosiglitazone or 15-d-PGJ2 for 24 h and 48 h.

CONCLUSIONS

Our results showed that PPARgamma was expressed in HT-29 cells and PPARgamma activation could inhibit cell growth through inducing apoptosis and suppressing the cell cycle. PPARgamma may be considered as a new therapeutic target for colon cancer in humans.

Role of peroxisome proliferator-activated receptor-γ in resveatrol-induced proliferation inhibition of gastric cancer cell line SGC-7901

AIM: To investigate the role of peroxisome proliferator-activated receptor-γ (PPAR-γ) in the inhibitory effects of resveratrol (Res) on gastric cancer cell SGC-7901 proliferation in vitro.

METHODS: After human gastric cancer cell SGC-7901 was cultured in vitro, MTT assay was used to detect the inhibitory effect of Res and GW9662 (specific blocker of PPAR-γ) on cell proliferation. Flow cytometry was used to detect cell cycle, and PPAR-γ, Cyclin D1 mRNA was measured quantitatively by reverse transcription-polymerase chain reaction (RT-PCR). The expression of PPAR-γ protein was measured quantitatively by Western blot, and the expression of Cyclin D1 protein in gastric cancer cells was detected by immunohistochemistry.

RESULTS: Res inhibited the proliferation of SGC-7901 cells in a dose- and time-dependent manner (P < 0.05), and flow cytometry analysis revealed that the cell cycle was blocked at G₁-phase. RT-PCR and Western blot showed that both PPAR-γ mRNA and protein were expressed in SGC-7901 cells, and Res enhanced PPAR-γ mRNA expression. After SGC-7901 cells were treated by Res with the concentration of 25, 50, 75 and 100 μmol/L, the relative percentages of PPAR-γ mRNA expression were 122.2%, 195.1%, 232.9% and 277.1% of those in the controls (P < 0.05), but the expression of PPAR-γ protein didn't changed. The high levels of Cyclin D1 mRNA and protein expression were detected in SGC-7901 cells, while Res significantly decreased the expression of Cyclin D1. After SGC-7901 cells were treated by Res with the concentration of 25, 50, 75 and 100 mmol/L, the inhibitory rates of Cyclin D1 mRNA were 11.3%, 24.3%, 35.4% and 59.5%, respectively, while GW9662 markedly decreased the above effects of Res.

CONCLUSION: Res can significantly inhibit Cyclin D1 expression partly by activating PPAR-γ in gastric cancer cells SGC-7901, which results in the blockage of cell cycle at G₁ phase and inhibition of cell proliferation.

Long-term Pharmacological Activation of PPARγDoes not Prevent Left Ventricular Remodeling in Dogs with Advanced Heart Failure

BACKGROUND

Peroxisome proliferator-activated receptor gamma (PPARgamma) activators affect the myocardium through inhibition of inflammatory cytokines and metabolic modulation but their effect in the progression of heart failure is unclear. In the present study, we examined the effects of the PPARgamma activator, GW347845 (GW), on the progression of heart failure.

METHODS AND RESULTS

Heart failure was produced in 21 dogs by intracoronary microembolizations to LV ejection fraction (EF) less than 30% and randomized to 3 months of therapy with high-dose GW (10 mg/Kg daily, n = 7), low-dose GW (3 mg/Kg daily, n = 7), or no therapy (control, n = 7). In control dogs, EF significantly decreased (28 +/- 1 vs. 22 +/- 1%, p < 0.001) and end-diastolic volume (EDV) and end-systolic volume (ESV) increased during the 3 months of the follow-up period (64 +/- 4 vs. 76 +/- 5; p = 0.003, 46 +/- 3 vs. 59 +/- 4 ml, p = 0.002, respectively). In dogs treated with low-dose GW, EDV increased significantly (69 +/- 4 vs.81 +/- 5 ml, p = 0.01), whereas ESV remained statistically unchanged (50 +/- 3 vs. 54 +/- 3 ml, p = 0.10) resulting in modestly increased ejection fraction (27 +/- 1 vs. 32 +/- 3%, p = 0.05). In dogs treated with high-dose GW, both EDV and ESV increased (72 +/- 4 vs. 79 +/- 5 ml, p = 0.04; 53 +/- 3 vs. 62 +/- 5 ml, p = 0.04) and EF decreased (26 +/- 1 vs. 23 +/- 1%, p = 0.04) as with control dogs. There was significantly increased myocardial hypertrophy as evidenced by increased LV weight to body weight ratio and myocyte cross-section area in the GW treated animals compared to controls. Compared to control, treatment with GW had no effect on mRNA expression of PPARgamma, inflammatory cytokines, stretch response proteins, or transcription factors that may induce hypertrophy.

CONCLUSIONS

Long-term PPARgamma activation with GW did not prevent progressive LV remodeling in dogs with advanced heart failure.

Peroxisome proliferator-activated receptor gamma is highly expressed in pancreatic cancer and is associated with shorter overall survival times

PURPOSE

Peroxisome proliferator-activated receptor gamma (PPARgamma) is a ligand-activated transcription factor that has been implicated in carcinogenesis and progression of various solid tumors, including pancreatic carcinoma. We aimed to clarify the expression patterns of PPARgamma in pancreatic ductal carcinomas and to correlate these to clinicopathologic variables, including patient survival.

EXPERIMENTAL DESIGN

Array-based expression profiling of 19 microdissected carcinomas and 14 normal ductal epithelia was conducted. Additionally, Western blots of pancreatic cancer cell lines and paraffinized tissue of 129 pancreatic carcinomas were immunostained for PPARgamma. For statistical analysis, Fisher's exact test, chi2 test for trends, correlation analysis, Kaplan-Meier analysis, and Cox's regression were applied.

RESULTS

Expression profiles showed a strong overexpression of PPARgamma mRNA (change fold, 6.9; P=0.04). Immunohistochemically, PPARgamma expression was seen in 71.3% of pancreatic cancer cases. PPARgamma expression correlated positively to higher pT stages and higher tumor grade. Survival analysis showed a significant prognostic value for PPARgamma, which was found to be independent in the clinically important subgroup of node-negative tumors.

CONCLUSIONS

PPARgamma is commonly up-regulated in pancreatic ductal adenocarcinoma and might be a prognostic marker in this disease. Both findings corroborate the importance of PPARgamma in tumor progression of pancreatic cancer.

Anti-proliferative effect of peroxisome proliferator-activated receptor gamma agonists on human malignant melanoma cells in vitro

Malignant melanoma has a poor reputation for early spread and no curative treatment is yet available. As peroxisome proliferator-activated receptor gamma (PPARgamma) agonists (glitazones) have recently been shown to have growth-inhibiting effects on different cancer lineages, the aim of this study was to analyze the effects of four glitazones (rosiglitazone, ciglitazone, pioglitazone and troglitazone) on the growth of six human malignant melanoma cells in vitro. Proliferation of six human melanoma cell lines under glitazone treatment over a broad concentration range (0.15-300 micromol/l) was assessed by means of the XTT cell proliferation assay, and expression of PPARgamma in these cell lines was analyzed using both immunohistochemical and molecular biological techniques. All four glitazones showed a significant dose-dependent anti-proliferative effect on all six cell lines starting at a concentration of 0.3 micromol/l, with ciglitazone being the most potent inhibitor of cell growth, followed by troglitazone, rosiglitazone and pioglitazone. PPARgamma was predominantly localized in the cytoplasm; however, there were quantitative differences in PPARgamma expression between the different cell lines as demonstrated by quantification of Western blots. As an already approved class of drugs, glitazones have been found to significantly inhibit growth of human malignant melanoma cells in vitro and might be a promising tool for further therapeutic studies.

Interaction with MEK causes nuclear export and downregulation of peroxisome proliferator-activated receptor gamma

The mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK) cascade plays a central role in intracellular signaling by many extracellular stimuli. One target of the ERK cascade is peroxisome proliferator-activated receptor gamma (PPARgamma), a nuclear receptor that promotes differentiation and apoptosis. It was previously demonstrated that PPARgamma activity is attenuated upon mitogenic stimulation due to phosphorylation of its Ser84 by ERKs. Here we show that stimulation by tetradecanoyl phorbol acetate (TPA) attenuates PPARgamma's activity in a MEK-dependent manner, even when Ser84 is mutated to Ala. To elucidate the mechanism of attenuation, we found that PPARgamma directly interacts with MEKs, which are the activators of ERKs, but not with ERKs themselves, both in vivo and in vitro. This interaction is facilitated by MEKs' phosphorylation and is mediated by the basic D domain of MEK1 and the AF2 domain of PPARgamma. Immunofluorescence microscopy and subcellular fractionation revealed that MEK1 exports PPARgamma from the nucleus, and this finding was supported by small interfering RNA knockdown of MEK1 and use of a cell-permeable interaction-blocking peptide, which prevented TPA-induced export of PPARgamma from the nucleus. Thus, we show here a novel mode of downregulation of PPARgamma by its MEK-dependent redistribution from the nucleus to the cytosol. This unanticipated role for the stimulation-induced nuclear shuttling of MEKs shows that MEKs can regulate additional signaling components besides the ERK cascade.

Inhibition of in vivo glioma growth and invasion by peroxisome proliferator-activated receptor gamma agonist treatment

The peroxisome proliferator-activated receptor gamma (PPARgamma), a member of the nuclear hormone receptor family, represents a possible new target in glioma therapy. Because PPARgamma plays a crucial role in regulation of insulin sensitivity, synthetic agonists are already in clinical use for type II diabetes treatment. Beyond these metabolic effects, PPARgamma agonists exhibit antineoplastic effects. In this study, we investigated the antineoplastic effects of the PPARgamma agonist pioglitazone in glioma cells. Pioglitazone reduced cellular viability of rat, human, and PPARgamma-overexpressing glioma cells in vitro in a time- and concentration-dependent manner. No antineoplastic effects were induced by pioglitazone in glioma cells overexpressing a PPARgamma mutant. Furthermore, proliferation was reduced by pioglitazone, as measured by Ki-67 immunoreactivity, in vitro. Continuous intracerebral infusion of pioglitazone into gliomas induced by intrastriatal injection of C6 cells reduced tumor volumes by 83%. Oral administration of pioglitazone reduced tumor volumes by 76.9%. Subsequent brain tissue analysis revealed induction of apoptotic cell death. Ki-67 expression and BrdU incorporation revealed a reduction of proliferation in vivo. Reduced invasion of C6 cells and lower matrix metalloproteinase 9 levels in vivo indicate pioglitazone-mediated reduction of invasion. Together, these data indicate that pioglitazone may be of potential use in treatment of malignant gliomas.

Peroxisome proliferator-activated receptor gamma (PPARgamma) regulates trefoil factor family 2 (TFF2) expression in gastric epithelial cells

Although trefoil factor family 2 (TFF2) plays a critical role in the defense and repair of gastric mucosa, the regulatory mechanism of TFF2 expression is not fully understood. In this study, we investigated the regulation of TFF2 expression by peroxisome proliferator-activated receptor gamma (PPARgamma) in gastric epithelial cells. MKN45 gastric cells were used. TFF2 mRNA expression was analyzed by real-time quantitative RT-PCR. The promoter sequence of the human TFF2 gene was cloned into pGL3-basic vector for reporter gene assays. Ciglitazone was mainly used as a specific PPARgamma ligand. MKN45 cells expressed functional PPARgamma proteins. Endogenous TFF2 mRNA expression and TFF2 reporter gene transcription was significantly up-regulated by ciglitazone in a dose-dependent manner. Reporter gene assays showed that two distinct cis-elements are involved in the response to PAPRgamma activation. Within one of these element (nucleotides -558 to -507), we identified a functional peroxisome proliferator responsive element (PPRE) at -522 (5'-GGGACAAAGGGCA-3'). Electrophoretic mobility shift assay (EMSA) and chromatin immunoprecipitation (ChIP) assay confirmed the binding of PPARgamma to this sequence. Another element (nucleotides -407 to -358) appeared to be a composite enhancer element indirectly regulated by PPARgamma and a combination of these two cis-elements was required for the full response of the human TFF2 gene expression to PPARgamma. These data demonstrate that human TFF2 gene is a direct target of PPARgamma in gastric epithelial cells. Since TFF2 is a critical gastroprotective agent, PPARgamma may be involved in the gastric mucosal defense through regulating TFF2 expression in humans.

15-deoxy-Delta(12,14)-prostaglandin J2 inhibits G2-M phase progression in human breast cancer cells via the down-regulation of cyclin B1 and survivin expression

The cyclopentenone prostaglandin 15-deoxy-Delta(12,14)-prostaglandin J(2) (15d-PGJ(2)) exerts a growth inhibitory effect on cancer cells, and this effect is linked to the induction of apoptosis or cell cycle arrest. Induction of apoptosis by 15d-PGJ(2) is associated with the down-regulation of anti-apoptotic proteins. G(0)-G(1)-->S phase progression is inhibited by 15d-PGJ(2) via the degradation of cyclin D1. In this study, we further investigated the mechanism by which 15d-PGJ(2) inhibits cancer cell growth by using the breast cancer cell lines MCF-7 and T-47D. Treatment with 20 microM 15d-PGJ(2) for 72 h completely blocked the growth in both cell lines. However, the proportions of apoptotic MCF-7 and T-47D cells were 21.1% and 40.9%, respectively, indicating that the induction of apoptosis did not appear to fully account for growth inhibition by 15d-PGJ(2). Cell cycle analysis using cells synchronized at the G(0)-G(1) or S phase revealed that 15d-PGJ(2) blocked not only G(0)-G(1)-->S phase progression but also G(2)-M phase progression. The expression of both cyclins D1 and B1 was decreased by 15d-PGJ(2). Furthermore, 15d-PGJ(2) inhibited aurora-B kinase activity, which coincided with the down-regulation of survivin. Thus, 15d-PGJ(2) induced cell cycle arrest at the G(2)-M phase via inhibition of cyclin B1 expression and aurora-B kinase activity. We conclude that survivin may be an important target for 15d-PGJ(2), and its down-regulation may lead to a decrease in aurora-B kinase activity.

Inhibition of peroxisome proliferator-activated receptor gamma activity in esophageal carcinoma cells results in a drastic decrease of invasive properties

Esophageal cancer is difficult to treat because of its rapid progression, and more effective therapeutic approaches are needed. The PPARgamma is a nuclear receptor superfamily member that is expressed in many cancers. PPARgamma expression is a feature of esophageal cancer cell lines, and in the present investigation, the PPARgamma antagonists T0070907 and GW9662 could induce loss of invasion but could not induce growth reduction or apoptosis at low concentrations (< 10 mM). A high concentration of antagonists (50 microM) inhibited cell growth and induced apoptosis, but these effects did not explain our result at the low concentration. Morphological change, decreased expression of the cell signaling pathway and inhibition of cancer cell invasion were observed in the low concentration. This suggested that PPARgamma antagonists inhibited esophageal cancer cell invasion as well as cell adherence, most likely due to alteration in the FAK-MAPK pathway, and this was independent of apoptosis. These results suggested that PPARgamma plays an important role in cancer cell invasion and that it might be a novel target for therapy of esophageal cancer.

Phorbol ester potentiates the growth inhibitory effects of troglitazone via up-regulation of PPARgamma in A549 cells

The activation of peroxisome proliferator-activated receptor gamma (PPARgamma) has been shown to induce growth arrest and differentiation of various cancer cells. In the current study, we investigated the effect of 12-O-tetradecanoylphorbol-13-acetate (TPA) on the expression of PPARgamma and proliferation of A549 cells. TPA elicited a dose- and time-dependent increase in PPARgamma mRNA and protein levels. PPARgamma expression in response to TPA was attenuated by pretreatment with bisindolylmaleimide I, N-acetyl-L-cysteine (NAC) and PD98059. TPA-induced protein kinase C (PKC) activation was linked to the generation of reactive oxygen species (ROS), both of which were indispensable for PPARgamma expression in A549 cells. Pretreatment with bisindolylmaleimide I or NAC blocked TPA-induced phosphorylation of extracellular signal-regulated kinase (ERK), suggesting that ERK-mediated signaling is also involved in the induction of PPARgamma. Furthermore, the growth inhibitory effect of troglitazone was significantly potentiated by prolonged incubation with TPA and was attenuated in the presence of GW9662, a specific inhibitor of PPARgamma. These effects were associated with an induction of cell cycle arrest at G0/G1 phase, which was accompanied by the induction of p21Waf1/Cip1 expression and decreased cyclin D1 expression. Taken together, these observations indicate that TPA synergizes with PPARgamma ligand to inhibit cell growth through up-regulation of PPARgamma expression.

Epigenetic regulation of nuclear steroid receptors

Histone modifier proteins have come to the forefront in the study of gene regulation. It is now known that histone methyltransferases, acetytransferases, kinases, ubiquitinases, deacetylases and demethylases orchestrate expression of target genes by modifying both histone and non-histone proteins. The nuclear receptor (NR) superfamily govern such diverse biological processes as development, physiology and disease, including human cancer. The involvement of NR in complexes with coactivators and corepressors is necessary for regulation of target genes. This review focuses on the newly recognized interactions between the NR and histone modifying enzymes. In addition to regulating histones, the histone modifying proteins directly modify and thereby regulate NR activity. In the same manner that signaling platforms exist within the histone tails that are post-translationally processed by histone modifying proteins, cascades of post-translational modification have been identified within the NR that coordinate their activity. This review focuses on the regulation of the NR estrogen receptor (ERalpha), androgen receptor (AR) and peroxisome proliferator activated receptor-gamma (PPARgamma), given their role in tumor onset and progression.

Expression of peroxisome proliferator activated receptor gamma and cyclo-oxygenase 2 in primary and recurrent ovarian carcinoma

AIM

Peroxisome proliferator-activated receptor gamma (PPARgamma) has emerged as a potential therapeutic target in several types of cancer. In ovarian carcinomas, limited and conflicting data on PPARgamma protein expression have been reported.

METHODS

The immunoexpression of PPARgamma and its putative target cyclo-oxygenase 2 (COX2) was investigated in tumour tissues from 80 patients with primary and corresponding recurrent ovarian serous carcinomas after conventional platinum-based chemotherapy.

RESULTS

PPARgamma expression was observed in 29% of primary and recurrent carcinomas. In the recurrent tumours, PPARgamma expression inversely correlated with COX2 overexpression in both chemosensitive (p = 0.02) and chemoresistant (p = 0.04) carcinomas.

CONCLUSIONS

The data indicate that PPARgamma may represent a potential target for second-line treatment in ovarian cancers.

PPARgamma-independent induction of growth arrest and apoptosis in prostate and bladder carcinoma

Background

Although PPARγ antagonists have shown considerable pre-clinical efficacy, recent studies suggest PPARγ ligands induce PPARγ-independent effects. There is a need to better define such effects to permit rational utilization of these agents.

Methods

We have studied the effects of a range of endogenous and synthetic PPARγ ligands on proliferation, growth arrest (FACS analysis) and apoptosis (caspase-3/7 activation and DNA fragmentation) in multiple prostate carcinoma cell lines (DU145, PC-3 and LNCaP) and in a series of cell lines modelling metastatic transitional cell carcinoma of the bladder (TSU-Pr1, TSU-Pr1-B1 and TSU-Pr1-B2).

Results

15-deoxy-prostaglandin J₂ (15dPGJ2), troglitazone (TGZ) and to a lesser extent ciglitazone exhibited inhibitory effects on cell number; the selective PPARγ antagonist GW9662 did not reverse these effects. Rosiglitazone and pioglitazone had no effect on proliferation. In addition, TGZ induced G0/G1 growth arrest whilst 15dPGJ2 induced apoptosis.

Conclusion

Troglitazone and 15dPGJ2 inhibit growth of prostate and bladder carcinoma cell lines through different mechanisms and the effects of both agents are PPARγ-independent.

Peroxisome proliferator-activated receptor-gamma Pro12Ala polymorphism, Helicobacter pylori infection and non-cardia gastric carcinoma in Chinese

BACKGROUND

Peroxisome proliferator-activated receptor gamma inhibits the growth and induces apoptosis of gastric cancer cells. A common polymorphism at codon 12 of this gene (Pro12Ala) has been shown to confer protection against diabetes and colorectal cancer.

AIM

To study the association between peroxisome proliferator-activated receptor gamma gene polymorphism, Helicobacter pylori infection and gastric cancer in Chinese.

METHODS

One hundred and four consecutive patients with non-cardia gastric adenocarcinoma and 104 matched controls were examined. Peroxisome proliferator-activated receptor gamma Pro12Ala polymorphism was analysed by polymerase chain reaction-restriction fragment length polymorphism.

RESULTS

The frequency of peroxisome proliferator-activated receptor gamma G (Ala12) allele was significantly higher among cancer patients (19.2%) than in control (8.7%; OR 2.5, 95% CI 1.1-5.8). While H. pylori infection was more prevalent in gastric cancer patients (OR 3.0; 95% CI 1.6-5.7), the combination of peroxisome proliferator-activated receptor gamma G allele and H. pylori infection further increased the risk of gastric cancer (OR 12.8, 95% CI 3.2-50.5). The presence of the Ala12 did not increase the risk of gastric cancer in H. pylori-negative subjects.

CONCLUSION

Our study suggests the potential association between peroxisome proliferator-activated receptor gamma polymorphism and H. pylori infection in the development of non-cardia gastric cancer.

Apoptosis induced by troglitazone is both peroxisome proliferator-activated receptor-γ- and ERK-dependent in human non-small lung cancer cells

The role of the peroxisome proliferator-activated receptor-gamma (PPARgamma) in cell differentiation, cell-cycle arrest, and apoptosis has attracted increasing attention. We have recently demonstrated that PPARgamma ligands-troglitazone (TGZ) induced apoptosis in lung cancer cells. In this report, we further studied the role of ERK1/2 in lung cancer cells treated by TGZ. The result demonstrated that TGZ induced PPARgamma and ERK1/2 accumulation in the nucleus, in which the co-localization of both proteins was found. The activation of ERK1/2 resulted in apoptosis via a mitochondrial pathway. Both PPARgamma siRNA and U0126, a specific inhibitor of ERK1/2, were able to block these effects of TGZ, suggesting that apoptosis induced by TGZ was PPARgamma and ERK1/2 dependent. Inhibition of ERK1/2 by U0126 also led to a significant decrease in the level of PPARgamma, indicating a positive cross-talk between PPARgamma and ERK1/2 or an auto-regulatory feedback mechanism to amplify the effect of ERK1/2 on cell growth arrest and apoptosis. In addition to ERK1/2, TGZ also activated Akt. Interestingly, inhibition of ERK1/2 prevented the activation of Akt whereas the suppression of Akt had no effect on ERK1/2, suggesting that Akt was not necessary for TGZ-PPARgamma-ERK pathway. However, the inhibition of Akt promoted the release of cytochrome c, suggesting the activation of Akt may have a negative effect on apoptosis induced by TGZ. In conclusion, our study has demonstrated that TGZ, a synthetic PPARgamma ligand, induced apoptosis in NCI-H23 lung cancer cells via a mitochondrial pathway and this pathway was PPARgamma and ERK1/2 dependent.

The Toxicology of Ligands for Peroxisome Proliferator-Activated Receptors (PPAR)

Peroxisome proliferator-activated receptors (PPARs) are ligand activated transcription factors that modulate target gene expression in response to endogenous and exogenous ligands. Ligands for the PPARs have been widely developed for the treatment of various diseases including dyslipidemias and diabetes. While targeting selective receptor activation is an established therapeutic approach for the treatment of various diseases, a variety of toxicities are known to occur in response to ligand administration. Whether PPAR ligands produce toxicity via a receptor-dependent and/or off-target-mediated mechanism(s) is not always known. Extrapolation of data derived from animal models and/or in vitro models, to humans, is also questionable. The different toxicities and mechanisms associated with administration of ligands for the three PPARs will be discussed, and important data gaps that could increase our current understanding of how PPAR ligands lead to toxicity will be highlighted.

Ligands for the peroxisome proliferator-activated receptor-gamma have inhibitory effects on growth of human neuroblastoma cells in vitro

The thiazolidinedione (TZD) or glitazone class of peroxisome proliferator-activated-gamma (PPAR-gamma) ligands not only induce adipocyte differentiation and increase insulin sensitivity, but also exert growth inhibitory effects on several carcinoma cell lines in vitro as well as in vivo. In the current study the in vitro effect of four PPAR-gamma agonists (ciglitazone, pioglitazone, troglitazone, rosiglitazone) on the cell growth of seven human neuroblastoma cell lines (Kelly, LAN-1, LAN-5, LS, IMR-32, SK-N-SH, SH-SY5Y) was investigated. Growth rates were assessed by a colorimetric XTT-based assay kit. Expression of PPAR-gamma protein was examined by immunohistochemistry and Western blot analysis. All glitazones inhibited in vitro growth and viability of the human neuroblastoma cell lines in a dose-dependent manner showing considerable effects only at high concentrations (10 microM and 100 microM). Effectiveness of the glitazones on neuroblastoma cell growth differed depending on the cell line and the agent. The presence of PPAR-gamma protein was demonstrated in all cell lines. Our findings indicate that ligands for PPAR-gamma may be useful therapeutic agents for the treatment of neuroblastoma. Thus the effect of glitazones on the growth of neuroblastoma should now be investigated in an in vivo animal model.

Evaluation of peroxisome proliferator-activated receptor-gamma expression in benign and malignant thyroid pathologies

Impairment of peroxisome proliferator-activated receptor-gamma (PPAR-gamma) function through a dominant negative PAX-8/PPAR-gamma fusion gene or other events resulting in wild-type PPAR-gamma downregulation has been implicated in malignant thyroid cell transformation. The aim of our study was to perform a systematic evaluation of PPAR-gamma mRNA and protein expression in normal thyroid tissue as opposed to benign thyroid pathologies of different functional status and thyroid malignancy, to gain further insights into a putative physiological role of PPAR-gamma in the thyroid and to define whether PPAR-gamma could serve as a marker of thyroid cell differentiation. Ten cold benign (CTN) and 10 toxic (TTN) thyroid nodules and corresponding normal thyroid tissues, 10 follicular thyroid cancers (FTC), 10 papillary thyroid cancers (PTC) and 8 Graves' disease (GD) thyroids were studied by real-time polymerase chain reaction (PCR), immunohistochemistry and reverse transcriptase (RT)-PCR (PAX-8/PPAR-gamma fusion gene). PPAR-gamma mRNA expression was demonstrated in all samples. When comparing benign nodular and normal thyroid tissue of the same patient no significant difference in PPAR-gamma mRNA expression was observed. PPAR-gamma mRNA levels were similar in CTN and FTC. In contrast, PPAR-gamma mRNA expression was downregulated in 9 of 10 PTC and all GD samples, whereby at least 4 fold downregulation (compared with normal and benign nodular thyroid tissues) was observed in the latter. Immunohistochemistry showed an increased, patchy PPAR-gamma nuclear staining in CTNs and TTNs and only faint staining in the corresponding normal thyroid tissues. A diffuse and weak PPAR-gamma staining pattern was observed in all GD samples. No PAX-8/PPAR-gamma rearrangements were detected in any of the 68 thyroid tissue samples. In conclusion PPAR-gamma mRNA and protein expression levels are not concordant in benign thyroid nodular disease. Furthermore there is no clear-cut association of PPAR-gamma mRNA expression with follicular thyroid tumorigenesis. Absence of a PAX-8/PPAR-gamma fusion gene in the series of 68 thyroid samples is in agreement with the suggestion of PAX-8/PPAR-gamma rearrangement being restricted to a subset of follicular thyroid cancers. The marked downregulation of PPAR-gamma in GD warrants further investigation and could be linked, for example, with changes in apoptosis.

Estrogen receptor alpha binds to peroxisome proliferator-activated receptor response element and negatively interferes with peroxisome proliferator-activated receptor gamma signaling in breast cancer cells

PURPOSE

The molecular mechanisms involved in the repressive effects exerted by estrogen receptors (ER) on peroxisome proliferator-activated receptor (PPAR) gamma-mediated transcriptional activity remain to be elucidated. The aim of the present study was to provide new insight into the crosstalk between ERalpha and PPARgamma pathways in breast cancer cells.

EXPERIMENTAL DESIGN

Using MCF7 and HeLa cells as model systems, we did transient transfections and electrophoretic mobility shift assay and chromatin immunoprecipitation studies to evaluate the ability of ERalpha to influence PPAR response element-mediated transcription. A possible direct interaction between ERalpha and PPARgamma was ascertained by co-immunoprecipitation assay, whereas their modulatory role in the phosphatidylinositol 3-kinase (PI3K)/AKT pathway was evaluated by determining PI3K activity and AKT phosphorylation. As a biological counterpart, we investigated the growth response to the cognate ligands of both receptors in hormone-dependent MCF7 breast cancer cells.

RESULTS

Our data show for the first time that ERalpha binds to PPAR response element and represses its transactivation. Moreover, we have documented the physical and functional interactions of ERalpha and PPARgamma, which also involve the p85 regulatory subunit of PI3K. Interestingly, ERalpha and PPARgamma pathways have an opposite effect on the regulation of the PI3K/AKT transduction cascade, explaining, at least in part, the divergent response exerted by the cognate ligands 17beta-estradiol and BRL49653 on MCF7 cell proliferation.

CONCLUSION

ERalpha physically associates with PPARgamma and functionally interferes with PPARgamma signaling. This crosstalk could be taken into account in setting new pharmacologic strategies for breast cancer disease.

Peroxisome proliferator-activated receptors in squamous cell carcinoma and its precursors

BACKGROUND

Peroxisome proliferator-activated receptors (PPARs) mediate several functions that are of interest in carcinogenesis. Although PPARalpha, PPARbeta, and PPARgamma are expressed in multiple human, their expression has not been investigated in non-melanoma skin cancer.

METHODS

We performed a retrospective paired immunohistochemical analysis of normal skin, actinic keratosis (AK), and squamous cell carcinoma (SCC) among 35 individuals. Specimens were considered PPAR immunoreactive when 1% or more of the tumor cells showed clear evidence of immunostaining. Cyclooxygenase-2 (COX-2) expression, the fraction of proliferating endothelial cells, and microvessel density were also evaluated in these samples.

RESULTS

PPARalpha immunoreactivity was significantly less likely to occur in SCC and AK than in normal skin of each individual. In contrast to PPARalpha, PPARbeta appeared to be upregulated in (pre)malignant skin lesions. For each individual, the likelihood that normal skin, AK, or SCC was immunoreactive against PPARgamma was comparable. COX-2 immunopositivity was significantly associated with PPARbeta and PPARgamma immunoreactivity. No statistical differences were noted for the angiogenesis parameters and PPARalpha, PPARbeta, or PPARgamma expression, except that the microvessel density was significantly higher among PPARbeta-immunoreactive SCCs compared to that among immunonegative SCCs.

CONCLUSION

Although further research is warranted, these results suggest that PPAR ligands such as fibrates and thiazolidinediones may have chemoprophylactic properties in skin carcinogenesis.

Expression of peroxisome proliferator-activated receptor delta in human gastric cancer and its response to specific COX-2 inhibitor

Peroxisome proliferator-activated receptor delta (PPARdelta) is ligand-activated transcription factor of the nuclear receptor superfamily which is recently implicated in carcinogenesis. We examined the expression profiles of PPARdelta in human gastric cancer, normal gastric mucosa and gastric cancer cell lines by RT-PCR, Western blot and immunohistochemistry. PPARdelta mRNA and protein was found to be ubiquitously expressed in all 5 gastric cancer cell lines, 40 gastric cancer samples and 10 normal gastric mucosa from non-cancer patients. Positive immunoreactivity was detected in the nuclei of normal and malignant gastric epithelium. Treatment of gastric cell line MKN45 that overexpressed cyclooxygenase-2 (COX-2) with specific COX-2 inhibitor NS398 resulted in a time- and dose-dependent suppression of PPARdelta expression. In contrast, there was no suppression of PPARdelta in MKN28 gastric cell line with low COX-2 expression. Our results demonstrated the ubiquitous expression of PPARdelta in normal and cancer gastric epithelium. Suppression of PPARdelta may be one of the mechanisms underlying the chemopreventive effects of COX-2 inhibitor.

Tocopherols and the treatment of colon cancer

Colorectal cancer is the second most common cause of cancer deaths in the United States. Vitamin E (VE) and other antioxidants may help prevent colon cancer by decreasing the formation of mutagens arising from the free radical oxidation of fecal lipids or by "non-antioxidant" mechanisms. VE is not a single molecule, but refers to at least eight different molecules, that is, four tocopherols and four tocotrienols.

METHODS

Both animal models and human colon cancer cell lines were used to evaluate the chemopreventive potential of different forms of VE. Rats were fed diets deficient in tocopherols or supplemented with either alpha-tocopherol or gamma-tocopherol. Half the rats in each of these groups received normal levels of dietary Fe and the other half Fe at eight times the normal level. In our cell experiments, we looked at the role of gamma-tocopherol in upregulating peroxisome proliferator-activated receptor-gamma (PPAR-gamma) in the SW 480 human cell line.

RESULTS

Rats fed the diets supplemented with alpha-tocopherol had higher levels of VE in feces, colonocytes, plasma, and liver than did rats fed diets supplemented with gamma-tocopherol. Dietary Fe levels did not influence tocopherol levels in plasma, liver, or feces. For colonocytes, high dietary Fe decreased tocopherol levels. Rats fed the gamma-tocopherol-supplemented diets had lower levels of fecal lipid hydroperoxides than rats fed the alpha-tocopherol-supplemented diets. Ras-p21 levels were significantly lower in rats fed the gamma-tocopherol-supplemented diets compared with rats fed the alpha-tocopherol-supplemented diets. High levels of dietary Fe were found to promote oxidative stress in feces and colonocytes. Our data with the SW480 cells suggest that both alpha- and gamma-tocopherol upregulate PPAR-gamma mRNA and protein expression. gamma-tocopherol was, however, found to be a better enhancer of PPAR-gamma expression than alpha-tocopherol at the concentrations tested.

Chemopreventive Effect of Peroxisome Proliferator–Activated Receptor γ on Gastric Carcinogenesis in Mice

Peroxisome proliferator-activated receptor gamma (PPARgamma) is known to be expressed in several cancers, and the treatment of these cancer cells with PPARgamma ligands often induces cell differentiation and apoptosis. Recently, the chemopreventive potential of PPARgamma ligands on colon carcinogenesis was reported, although the effect of PPARgamma on colon carcinogenesis and the mechanism of the effect remain controversial. In this study, we attempted to elucidate the role of PPARgamma in gastric carcinogenesis and explored the possible use of PPARgamma ligand as a chemopreventive agent for gastric cancer. N-methyl-N-nitrosourea (MNU, 240 ppm) was given in drinking water for 10 weeks to induce gastric cancer in PPARgamma wild-type (+/+) and heterozygous-deficient (+/-) mice, followed by treatment with PPARgamma ligand [troglitazone, 0.15% (w/w) in powder food] or the vehicle alone for 42 weeks. At the end of the experiment, PPARgamma (+/-) mice were more susceptible to MNU-induced gastric cancer than wild-type (+/+) mice (89.5%/55.5%), and troglitazone significantly reduced the incidence of gastric cancer in PPARgamma (+/+) mice (treatment 55.5%/vehicle 9%) but not in PPARgamma (+/-) mice. The present study showed that (a) PPARgamma suppresses gastric carcinogenesis, (b) the PPARgamma ligand troglitazone is a potential chemopreventive agent for gastric carcinogenesis, and (c) troglitazone's chemopreventive effect is dependent on PPARgamma.

Treatment of thyroid cancer with histone deacetylase inhibitors and peroxisome proliferator-activated receptor-gamma agonists

Among the most promising new antineoplastic therapies for poorly differentiated or undifferentiated thyroid cancer are the histone deacetylase inhibitors and the peroxisome proliferator-activated receptor (PPAR)-gamma agonists. These two classes of drugs have been shown to inhibit growth and induce apoptosis and redifferentiation in a variety of hematologic and solid cancer cell lines and animal models. In this article we review the molecular mechanisms, in vitro and in vivo studies, and clinical applications of the histone deacetylase inhibitors and PPAR-gamma agonists in the treatment of thyroid cancer.

Peroxisome proliferator-activated receptor gamma inhibition prevents adhesion to the extracellular matrix and induces anoikis in hepatocellular carcinoma cells

Activation of the nuclear transcription factor peroxisome proliferator-activated receptor gamma (PPARgamma) inhibits growth and survival of hepatocellular carcinoma (HCC) cell lines. To further investigate the function of PPARgamma in HCC, PPARgamma expression patterns in primary tumors were examined, and the responses of two HCC cell lines to PPARgamma activation and inhibition were compared. PPARgamma expression was increased in HCC and benign-appearing peritumoral hepatocytes compared with remote benign hepatocytes. Both compound PPARgamma inhibitors and PPARgamma small interfering RNAs prevented HCC cell lines from adhering to the extracellular matrix. Loss of adhesion was followed by caspase-dependent apoptosis (anoikis). PPARgamma inhibitors had no effect on initial beta1 integrin-mediated adhesion, or on total focal adhesion kinase levels but did reduce focal adhesion kinase phosphorylation. The PPARgamma inhibitor T0070907 was significantly more efficient at causing cancer cell death than the activators troglitazone and rosiglitazone. T0070907 caused cell death by reducing adhesion and inducing anoikis, whereas the activators had no direct effect on adhesion and caused cell death at much higher concentrations. In conclusion, PPARgamma overexpression is present in HCC. Inhibition of PPARgamma function causes HCC cell death by preventing adhesion and inducing anoikis-mediated apoptosis. PPARgamma inhibitors represent a potential novel treatment approach to HCC.

Peroxisome proliferator activated receptor-γ ligands induced cell growth inhibition and its influence on matrix metalloproteinase activity in human myeloid leukemia cells

Peroxisome proliferator-activated receptor-gamma (PPAR-gamma) is one of the best characterized nuclear hormone receptors (NHRs) in the superfamily of ligand-activated transcriptional factors. PPAR-gamma ligands have recently been demonstrated to affect proliferation, differentiation and apoptosis of different cell types. The present study was undertaken to investigate PPAR-gamma ligands induced cell growth inhibition and its influence on matrix metalloproteinase MMP-9 and MMP-2 activities on leukemia K562 and HL-60 cells in vitro. The results revealed that PPAR-gamma expression was detectable in the two kinds of leukemia cells; Both 15-deoxy-delta(12,14)-prostaglandin J2(15d-PGJ2) and troglitazone (TGZ) have significant growth inhibition effects on these two kinds of leukemia cells. These two PPAR-gamma ligands could inhibit the leukemic cell adhesion to the extracellular matrix (ECM) proteins and the invasion through matrigel matrix. The expressions of MMP-9 and MMP-2 as well as their gelatinolytic activities in both HL-60 and K562 cells were inhibited by 15d-PGJ2 and TGZ significantly. We therefore conclude that PPAR-gamma ligands 15d-PGJ2 and TGZ have significant growth inhibition effects on myeloid leukemia cells in vitro, and that PPAR-gamma ligands can inhibit K562 and HL-60 cell adhesion to and invasion through ECM as well as downregulate MMP-9 and MMP-2 expressions. The data suggest that PPAR-gamma ligands may serve as potential anti-leukemia reagents.

Possible involvement of p38 in mechanisms underlying acceleration of proliferation by 15-deoxy-Delta(12,14)-prostaglandin J2 and the precursors in leukemia cell line THP-1

15-deoxy-Delta(12,14)-prostaglandin J(2) (15dPGJ2), which is a ligand for peroxisome proliferator-activated receptor gamma (PPARgamma), induced apoptosis of several human tumors including gastric, lung, colon, prostate, and breast. However, the role of PPARgamma signals in other types of cancer cells (e.g., leukemia) except solid cancer cells is still unclear. The aim of this study is to evaluate the ability of 15dPGJ2 to modify the proliferation of the human leukemia cell line THP-1. 15dPGJ2 at 5 microM stimulated the proliferation in THP-1 at 24 to 72 h after incubation. In contrast, 15dPGJ2 at concentrations above 10 microM inhibited the proliferation through the induction of apoptosis. PGD2, PGJ2, and Delta12-PGJ2 (DeltaPGJ2), precursors of 15dPGJ2, had similar proliferative effects at lower concentrations, whereas they induced apoptosis at high concentrations. 15dPGJ2 and three precursors failed to induce the differentiation in THP-1 as assessed by using the differentiation marker CD11b. FACScan analysis revealed that PGD2 at 5 microM, PGJ2 at 1 microM, DeltaPGJ2 at 1 microM and 15dPGJ2 at 5 microM all accelerated cell cycle progression in THP-1. Immunoblotting analysis revealed that PGD2 at 5 microM and 15dPGJ2 at 5 microM inhibited the expression of phospho-p38, phospho-MKK3/MKK6, and phospho-ATF-2, and the expression of Cdk inhibitors including p18, p21, and p27 in THP-1. In contrast, PGJ2 at 1 microM and DeltaPGJ2 at 1 microM did not affect their expressions. These results suggest that 15dPGJ2 and PGD2 may, through inactivation of the p38 mitogen-activated protein kinase pathway, inhibit the expression of Cdk inhibitors, leading to acceleration of the THP-1 proliferation.

Enhanced expression of peroxisome proliferator-activated receptor gamma in epithelial ovarian carcinoma

The peroxisome proliferator-activated receptors (PPARs) belong to a subclass of nuclear hormone receptor that executes important cellular transcriptional functions. Previous studies have demonstrated the expression of PPARγ in several tumours including colon, breast, bladder, prostate, lung and stomach. This study demonstrates the relative expression of PPARγ in normal ovaries and different pathological grades of ovarian tumours of serous, mucinous, endometrioid, clear cell and mixed subtypes. A total of 56 ovarian specimens including 10 normal, eight benign, 10 borderline, seven grade 1, nine grade 2 and 12 grade 3 were analysed using immunohistochemistry. Immunoreactive PPARγ was not expressed in normal ovaries. Out of eight benign and 10 borderline tumours, only one tumour in each group showed weak cytoplasmic PPARγ expression. In contrast, 26 out of 28 carcinomas studied were positive for PPARγ expression with staining confined to cytoplasmic and nuclear regions. An altered staining pattern of PPARγ was observed in high-grade ovarian tumours with PPARγ being mostly localized in the nuclei with little cytoplasmic immunoreactivity. On the other hand, predominant cytoplasmic staining was observed in lower-grade tumours. Significantly increased PPARγ immunoreactivity was observed in malignant ovarian tumours (grade 1, 2 and 3) compared to benign and borderline tumours (χ²=48.80, P<0.001). Western blot analyses showed significant elevation in the expression of immunoreactive PPARγ in grade 3 ovarian tumours compared with that of normal ovaries and benign ovarian tumours (P<0.01). These findings suggest an involvement of PPARγ in the onset and development of ovarian carcinoma and provide an insight into the regulation of this molecule in the progression of the disease.

Troglitazone, the peroxisome proliferator-activated receptor-gamma agonist, induces antiproliferation and redifferentiation in human thyroid cancer cell lines

Troglitazone is a potent agonist for the peroxisome proliferator-activated receptor-gamma (PPARgamma) that is a ligand-activated transcription factor regulating cell differentiation and growth. PPARgamma may play a role in thyroid carcinogenesis since PAX8-PPARgamma1 chromosomal translocations are commonly found in follicular thyroid cancers. We investigated the antiproliferative and redifferentiation effects of troglitazone in 6 human thyroid cancer cell lines: TPC-1 (papillary), FTC-133, FTC-236, FTC-238 (follicular), XTC-1 (Hürthle cell), and ARO82-1 (anaplastic) cell lines. PPARgamma was expressed variably in these cell lines. FTC-236 and FTC-238 had a rearranged chromosome at 3p25, possibly implicating the involvement of the PPARgamma encoding gene whereas the other cell lines did not. Troglitazone significantly inhibited cell growth by cell cycle arrest and apoptotic cell death. PPARgamma overexpression did not appear to be a prerequisite for a response to treatment with troglitazone. Troglitazone also downregulated surface expression of CD97, a novel dedifferentiation marker, in FTC-133 cells and upregulated sodium iodide symporter (NIS) mRNA in TPC-1 and FTC-133 cells. Our investigations document that human thyroid cancer cell lines commonly express PPARgamma, but chromosomal translocations involving PPARgamma are uncommon. Troglitazone, a PPARgamma agonist, induced antiproliferation and redifferentiation in thyroid cancer cell lines. PPARgamma agonists may therefore be effective therapeutic agents for the treatment of patients with thyroid cancer that fails to respond to traditional treatments.

Ciglitizone inhibits cell proliferation in human uterine leiomyoma via activation of store-operated Ca2+ channels

This study investigated the acute effects of a peroxisome proliferator-activated receptor (PPAR)-γ ligand, ciglitizone, on cell proliferation and intracellular Ca2+ signaling in human normal myometrium and uterine leiomyoma. Changes in intracellular Ca2+ concentration ([Ca2+]i) were measured with fura-2 AM, and cellular viabilities were determined by viable cell count and 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide reduction assay. Ciglitizone (100 μM) induced greater inhibition of cell proliferation in uterine leiomyoma than in myometrium. Ciglitizone also dose-dependently increased [Ca2+]i in both myometrium and uterine leiomyoma; these [Ca2+]i increases were inhibited by PPAR-γ antagonists and raloxifene. Ciglitizone-induced [Ca2+]i increase showed only an initial peak in normal myometrial cells, whereas in uterine leiomyoma there was a second sustained [Ca2+]i increase as well. The initial [Ca2+]i increase in both myometrium and uterine leiomyoma resulted from the release of Ca2+ by the sarcoplasmic reticulum via activation of ryanodine receptors. The second [Ca2+]i increase was observed only in uterine leiomyoma because of a Ca2+ influx via an activation of store-operated Ca2+ channels (SOCCs). Cell proliferation was inhibited and secondary [Ca2+]i increase in uterine leiomyoma was attenuated by cotreatment of ciglitizone with a SOCC blocker, lanthanum. The results suggest that ciglitizone inhibits cell proliferation and increases [Ca2+]i through the activation of SOCCs, especially in human uterine leiomyoma.

Implication of peroxisome proliferator-activated receptor gamma and proinflammatory cytokines in gastric carcinogenesis: link to Helicobacter pylori-infection

Peroxisome proliferator-activated receptor gamma (PPARgamma) is a ligand-dependent transcription factor involved in various processes including the inflammation and carcinogenesis. The aim of the present study was 1) to examine the mRNA and protein expression of PPARgamma in gastric cancer (GC); 2) to evaluate the effect of PPARgamma ligand (ciglitazone) on the proliferation and apoptosis of GC cell line; and 3) to assess the levels of gastric tissue proinflammatory cytokines, IL-1beta and IL-8, and plasma gastrin in GC patients before and after Helicobacter pylori (H. pylori) eradication. The trial material included 30 H. pylori-negative controls and 30 sex- and age-matched GC patients without or with H. pylori before and after its eradication. Expression of tissue PPARgamma, tissue levels of IL-1beta and IL-8, and plasma concentration of gastrin were significantly higher in H. pylori-positive GC compared to controls, but H. pylori eradication significantly reduced these parameters. Kato III cells incubated with alive H. pylori upregulated PPARgamma expression and ciglitazone inhibited cell proliferation and induced apoptosis. PPARgamma, proinflammatory cytokines and plasma gastrin appear to be implicated in H. pylori-related gastric carcinogenesis and PPARgamma agonists may have potential in cancer therapy.

Acetylation of nuclear receptors in cellular growth and apoptosis

Post-translational modification of chromatin histones governs a key mechanism of transcriptional regulation. Histone acetylation, together with methylation, phosphorylation, ubiquitylation, sumoylation, glycosylation, and ADP ribosylation, modulate the activity of many genes by modifying both core histones and non-histone transcription factors. Epigenetic protein modification plays an important role in multiple cellular processes including DNA repair, protein stability, nuclear translocation, protein-protein interactions, and in regulation of cellular proliferation, differentiation and apoptosis. Histone acetyltransferases modify histones, coactivators, nuclear transport proteins, structural proteins, cell cycle components and transcription factors including p53 and nuclear receptors. The estrogen, PPARgamma and androgen receptor are members of the nuclear receptor (NR) superfamily. The androgen receptor (AR) and estrogen receptor alpha (ERalpha) are directly acetylated by histone acetyltransferases at a motif that is conserved between species and other NR. Point mutations at the lysine residue within the acetylation motif of the AR and ERalpha have been identified in prostate cancer as well as in breast cancer tissue. Acetylation of the NR governs ligand sensitivity and hormone antagonist responses. The AR is acetylated by p300, P/CAF and TIP60 and acetylation of the AR regulates co-regulator recruitment and growth properties of the receptors in cultured cells and in vivo. AR acetylation mimic mutants convey reduced apoptosis and enhanced growth properties correlating with altered promoter specificity for cell-cycle target genes. Cell-cycle control proteins, including cyclins, in turn alter the access of transcription factors and nuclear receptors to the promoters of target genes.

Underexpression of peroxisome proliferator-activated receptor (PPAR)gamma in PAX8/PPARgamma-negative thyroid tumours

The expression of peroxisome proliferator-activated receptor (PPAR)γ in thyroid neoplasias and in normal thyroid (NT) tissues has not been fully investigated. The objectives of the present work were: to study and compare the relative expression of PPARγ in normal, benign and malignant thyroid tissues and to correlate PPARγ immunostaining with clinical/pathological features of patients with thyroid cancer. We analysed the expression of PPARγ in several types of thyroid tissues by reverse transcription–polymerase chain reaction (RT–PCR), interphase fluorescent in situ hybridisation, real-time RT–PCR and immunohistochemistry. We have demonstrated that NT tissues express PPARγ both at mRNA and at protein level. PAX8-PPARγ fusion gene expression was found in 25% (six of 24) of follicular thyroid carcinomas (FTCs) and in 17% (six of 36) of follicular thyroid adenomas, but in none of the 10 normal tissues, 28 nodular hyperplasias, 38 papillary thyroid carcinomas (PTCs) and 11 poorly differentiated thyroid carcinomas (PDTCs). By real-time RT–PCR, we observed that tumours negative for the PAX8-PPARγ rearrangement expressed lower levels of PPARγ mRNA than the NT. Overexpression of PPARγ transcripts was detected in 80% (four of five) of translocation-positive tumours. Diffuse nuclear staining was significantly (P<0.05) less prevalent in FTCs (53%; 18 of 34), PTCs (49%; 19 of 39) and PDTCs (0%; zero of 13) than in normal tissue (77%; 36 of 47). Peroxisome proliferator-activated receptorγ-negative FTCs were more likely to be locally invasive, to persist after surgery, to metastasise and to have poorly differentiated areas. Papillary thyroid carcinomas with a predominantly follicular pattern were more often PPARγ negative than classic PTCs (80% vs 28%; P=0.01). Our results demonstrated that PPARγ is underexpressed in translocation-negative thyroid tumours of follicular origin and that a further reduction of PPARγ expression is associated with dedifferentiation at later stages of tumour development and progression.

Clinical implication of expression of cyclooxygenase-2 and peroxisome proliferator activated-receptor gamma in epithelial ovarian tumours

Expression of cyclooxygenase (COX)-2 plays a key role in tumorigenesis and development and peroxisome proliferator-activated receptor gamma (PPARgamma) has been implicated in the control of COX-2 expression in some tissues. The aim of this study is to investigate (1) whether expression of COX-2 and PPARgamma is associated with ovarian carcinogenesis and progression of ovarian tumours and (2) whether COX-2 expression is controlled through ligand-mediated activation of PPARgamma in ovarian carcinoma cells. For this purpose, the presence of COX-2 and PPARgamma was immunohistochemically examined in 71 epithelial ovarian carcinomas, 18 borderline tumours and 23 benign tumours and the levels of COX-2 and PPARgamma proteins were determined by enzyme immunoassay in four benign tumours, three borderline tumours and 12 carcinomas. The frequency of COX-2 and PPARgamma detection was significantly increased and decreased as lesions progressed to carcinoma, respectively. The COX-2 protein was not detected in the three borderline tumours, whereas PPARgamma protein was detected in all of them. COX-2 protein was detected in eight of the 12 carcinomas, whereas PPARgamma protein was detected in only two cases. In addition, PPARgamma protein was not detected in all of the eight carcinomas in which COX-2 protein was detected, suggesting that expression of PPARgamma and COX-2 was in a reciprocal relationship. Furthermore, in cultured ovarian carcinoma cells, Western blot revealed that PPARgamma and COX-2 expression was regulated conversely as a result of stimulation by 15-deoxy-Delta(12, 14) PGJ(2) (15-PGJ(2)), a PPARgamma activator. In addition, 15d-PGJ(2) suppressed tumour necrosis factor-alpha-induced-COX-2 expression, confirming the reciprocal correlation between COX-2 and PPARgamma. From these results, it was suggested that PPARgamma activation might suppress COX-2 expression via the nuclear factor-kappaB pathway in the ovarian carcinoma cells and that low expression of PPARgamma and high expression of COX-2 might be involved in carcinogenesis and progression of ovarian tumours.

Antineoplastic effects of peroxisome proliferator-activated receptor gamma agonists

Peroxisome proliferator-activated receptors (PPAR) are members of a superfamily of nuclear hormone receptors. Activation of PPAR isoforms elicits both antineoplastic and anti-inflammatory effects in several types of mammalian cells. PPARs are ligand-activated transcription factors and have a subfamily of three different isoforms: PPAR alpha, PPAR gamma, and PPAR beta/delta. All isoforms heterodimerise with the 9-cis-retinoic acid receptor RXR, and play an important part in the regulation of several metabolic pathways, including lipid biosynthesis and glucose metabolism. Endogenous ligands of PPAR gamma include long-chain polyunsaturated fatty acids, eicosanoid derivates, and oxidised lipids. Newly developed synthetic ligands include thiazolidinediones-a group of potent PPAR gamma agonists and antidiabetic agents. Here, we review PPAR gamma-induced antineoplastic signalling pathways, and summarise the antineoplastic effects of PPAR gamma agonists in different cancer cell lines, animal models, and clinical trials.

Activation of NFkappaB represents the central event in the neoplastic progression associated with Barrett's esophagus: a possible link to the inflammation and overexpression of COX-2, PPARgamma and growth factors

The molecular mechanisms responsible for the progression of malignant transformation in Barrett's esophagus (BE) are still poorly understood. This study was undertaken (1) to investigate the gene and protein expression of cyclooxygenase-2 (COX-2), peroxisome proliferator-activated receptor-gamma (PPARgamma), interleukin-8 (IL-8), hepatocyte growth factor (HGF), gastrin, and its receptor (CCK-2) in the Barrett's epithelium; (2) to analyze the activity of NFkappaB in Barrett's esophagus with low-grade dysplasia; and (3) to assess the effects of PPARgamma ligand (ciglitazone) and gastrin on cell proliferation in the cell line derived from esophageal adenocarcinoma (OE-33). COX-2, PPARgamma, IL-8, HGF, gastrin, and CCK-2 expression levels relative to the control gene encoding GAPDH were analyzed by RT-PCR and Western blot in specimens of BE with low-grade dysplasia (n = 20) and compared with that in the normal squamous esophageal mucosa from the middle portion of the esophagus (n = 20). In vitro experiments included the incubation of cell line OE-33 with ciglitazone (1-15 microM) and gastrin (100 nM). NFkappaB activity in biopsies specimens was measured by highly sensitive ELISA. COX-2, PPARgamma, IL-8, HGF, gastrin, and CCK-2 expressions were significantly increased in BE compared with normal squamous esophageal mucosa. NFkappaB activity was significantly upregulated in BE. Ciglitazone inhibited cell proliferation of OE-33 cells as assessed by BrdU and this effect was attenuated partly by gastrin. (1) COX-2, PPARgamma, HGF, gastrin, and its receptor are significantly upregulated in BE, suggesting a possible role for these factors in Barrett's carcinogenesis; (2) the increased NFkappaB activity is probably linked to increased IL-8 and COX-2 expression; and (3) PPARgamma ligands might be useful as a new therapeutic option in the prevention and treatment of Barrett's carcinoma.

Redifferentiation therapy for thyroid cancer

Thyroid tumorigenesis and carcinogenesis accompany progressive loss of thyroid-specific differentiated functions. Some thyroid cancers are or become dedifferentiated, and they become refractory to efficacy-proven conventional therapies such as radioiodine ablation therapy and thyrotropin (TSH)-suppressive therapy. Redifferentiation therapy by either redifferentiating agents or gene transfer of differentiation-related genes may retard tumor growth and make tumors respond to conventional therapies.

Induction of Proliferation by 15-Deoxy-Δ12,14-Prostaglandin J2 and the Precursors in Monocytic Leukemia U937

Peroxisome proliferator-activated receptor gamma (PPARgamma) is expressed in several human tumors including gastric, lung, colon, prostate and breast. However, the role of PPARgamma signals in leukemia is still unclear. The aim of this study is to evaluate the ability of 15-deoxy-Delta12,14-prostaglandin J2 (15dPGJ2), that is a ligand for PPARgamma, on proliferation of human leukemia cell line U937. 15dPGJ2 at 5 micromol/l stimulated the proliferation. In contrast, 15dPGJ2 at concentrations of >10 micromol/l inhibited the proliferation through the induction of apoptosis. PGD2, PGJ2 and Delta12-PGJ2 (DeltaPGJ2), those are precursors of 15dPGJ2, had similarly proliferative effects, whereas they showed antiproliferative effects at high concentrations. FACScan analysis revealed that PGD2 at 5 micromol/l, PGJ2 at 1 micromol/l, DeltaPGJ2 at 1 micromol/l and 15dPGJ2 at 5 micromol/l, all accelerated cell cycle progression. Immunoblotting analysis revealed that PGD2 at 5 micromol/l and 15dPGJ2 at 5 micromol/l inhibited the expression of phospho-p38, phospho-MKK3/MKK6 and phospho-ATF-2, and the expression of Cdk inhibitors including p18, p27. In contrast, PGJ2 at 1 micromol/l and DeltaPGJ2 at 1 micromol/l did not affect the expression of them. These results suggest that 15dPGJ2 and PGD2 may, through inactivation of the p38 MAPK pathway, inhibit the expression of Cdk inhibitors, leading to acceleration of proliferation.

Peroxisome proliferator-activated receptor gamma ligands induce growth inhibition and apoptosis of human B lymphocytic leukemia

This study examined the expression and structural intactness of peroxisome proliferator-activated receptor gamma (PPARgamma) in human acute lymphocytic leukemia (ALL) cells and determined the effect of PPARgamma ligands on growth and apoptosis of these cells. We noted that all lymphocytic leukemia cell lines expressed PPARgamma and no PPARgamma mutations were found in these cell lines as indicated by SSCP analysis. Effect of the PPARgamma ligands on the proliferation, differentiation and apoptosis of B type ALL cells was further examined. Treatment of these cells with the PPARgamma ligands Pioglitazone (PGZ) and 15-deoxy-delta (12,14)-prostaglandin J2 (15d-PGJ2) resulted in growth inhibition in a dose-dependent manner which was associated with a G1 to S cell cycle arrest. However, this effect appeared to be PPARgamma-independent since several PPARgamma antagonists could not reverse this effect. No differentiation was induced by this treatment. Four out of five cell lines underwent apoptosis after culture with the PPARgamma ligands. This effect was partially caspase-dependent because a pan-caspase inhibitor partially reversed this effect. In conclusion, our results suggest that PPARgamma ligands may offer a new therapeutic approach to aid in the treatment of ALL.

Association of peroxisome proliferator–activated receptor gamma 2 Pro-12-Ala polymorphism with endometriosis

We explored the association of the PPAR-gamma2 (peroxisome proliferator-activated receptor) Pro-12-Ala polymorphism with endometriosis in a case-control study with 51 women with endometriosis stages I-IV and 55 control women without endometriosis. The 12-Pro allele of PPAR-gamma2 may have protective effects avoiding the development and progression of endometriosis.

Therapeutic potential of thiazolidinediones as anticancer agents

Thiazolidinediones (TZDs) are synthetic ligands that activate the nuclear receptor peroxisome proliferator-activated receptor-gamma (PPAR-gamma). These compounds are widely used in the treatment of Type 2 diabetes. TZDs have antitumour activity in a wide variety of experimental cancer models, in vitro and in vivo, by affecting the cell cycle, induction of cell differentiation and apoptosis as well as by inhibiting tumour angiogenesis. These effects are mediated through both PPAR-gamma-dependent and -independent pathways depending on concentration and tumour cell type. Angiogenesis inhibition mechanisms of TZDs include directly inhibiting endothelial cell proliferation and migration as well as decreasing tumour cell vascular endothelial growth factor production. Further studies suggest that TZDs may be effective in prevention of certain cancers and in the treatment of cancer as adjuvant therapy.