PPARgamma ligands and ATRA inhibit the invasion of human breast cancer cells in vitro

Peroxisome proliferator-activated receptor gamma-independent effects of thiazolidinediones on human cardiac myofibroblast function

1. Thiazolidinediones (TZDs) are peroxisome proliferator-activated receptor (PPAR) gamma agonists that are used to lower insulin resistance in Type 2 diabetic patients. Although TZDs exhibit beneficial effects on the vasculature, their effects on the heart are less clear and are the subject of current clinical debate. Thiazolidinediones have been reported to reduce adverse myocardial remodelling, a pathology in which cardiac myofibroblasts (CMF) are pivotal. 2. The aim of the present study was to investigate whether TZDs modulate specific human CMF functions of importance to the myocardial remodelling process and to determine whether any of these effects were mediated via PPARgamma activation. 3. Immunoblotting of cultured human CMF homogenates revealed strong expression of PPARgamma (approximately 50 kDa). Three different TZDs (ciglitazone, rosiglitazone and troglitazone) and the endogenous PPARgamma ligand 15-deoxy-delta(12,14)-prostaglandin J(2) (15d-PGJ(2)) inhibited CMF proliferation (cell number and expression of proliferating cell nuclear antigen) in a concentration-dependent manner (range 0.1-10 micromol/L) with similar potencies. This antiproliferative effect of TZDs was not reversed by the PPARgamma antagonists GW9662 or T0070907 (10-25 micromol/L). None of the TZDs or 15d-PGJ(2) affected cell migration or invasion (Boyden chamber assays without or with Matrigel barrier), matrix metalloproteinase-2 or -9 secretion (gelatin zymography) or the actin cytoskeleton (rhodamine/phalloidin fluorescent confocal microscopy). 4. In conclusion, TZDs reduce human CMF proliferation via a PPARgamma-independent mechanism. Although TZDs do not inhibit CMF invasion, their antiproliferative activity may contribute to the ability of this class of drugs to modulate adverse myocardial remodelling.

Anti-invasive effect of gambogic acid in MDA-MB-231 human breast carcinoma cells

Gambogic acid (GA) has been known to have antitumor activity in vitro and in vivo. In the present study, we investigated the anti-invasive effects of GA in MDA-MB-231 human breast carcinoma cells. The results indicated that GA significantly inhibited the adhesion, migration, and invasion of the cells in vitro tested by the heterotypic adhesion assay, wound migration assay, and chamber invasion assay. Results of Western blotting and immunocytochemistry analysis showed that GA could suppress the expressions of matrix metalloproteinase 2 (MMP-2) and 9 (MMP-9) in MDA-MB-231 cells. Furthermore, gelatin zymography revealed that GA decreased the activities of MMP-2 and MMP-9. Additionally, GA exerted an inhibitory effect on the phosphorylation of ERK1/2 and JNK, while it had no effect on p38. Taken together, our results demonstrated the anti-invasive property of GA for the first time and indicated it could serve as a promising drug for the treatment of cancer metastasis.

The role of 15-deoxy-delta(12,14)-prostaglandin J(2), an endogenous ligand of peroxisome proliferator-activated receptor gamma, in tumor angiogenesis

Peroxisome proliferator-activated receptor gamma (PPARgamma), a nuclear hormone receptor, is a ligand-activated transcription factor involved in adipogenesis, glucose homeostasis and lipid metabolism. 15-Deoxy-Delta(12,14)-prostaglandin J(2) (15d-PGJ(2)), an endogenous ligand of PPARgamma, has multifaceted cellular functions. Angiogenesis plays an important role in the pathophysiology of ischemic and neoplastic disorders, especially cancer. 15d-PGJ(2) is involved in regulation of angiogenic mediators including vascular endothelial growth factor and hence participates in the blood vessel formation by means of angiogenesis. However, depending on the experimental conditions, this cyclopentenone prostaglandin can exert opposite effects on angiogenesis. 15d-PGJ(2) inhibits angiogenesis via suppression of pro-inflammatory enzymes and cytokines, while it also stimulates angiogenesis via induction of heme oxygenase-1, endothelial nitric-oxide synthase, and hypoxia inducible factor-1alpha. The aim of this review is to highlight such dual effects of 15d-PGJ(2) on angiogenesis and underlying molecular mechanisms.

Retinol decreases phosphatidylinositol 3-kinase activity in colon cancer cells

Previously, we showed that retinol inhibited all-trans-retinoic acid (ATRA)-resistant human colon cancer cell invasion via a retinoic acid receptor-independent mechanism. Because phosphatidylinositol 3-kinase (PI3K) regulates cell invasion, the objective of the current study was to determine if retinol affected PI3K activity. Following 24 h of serum starvation, the ATRA resistant human colon cancer cell lines HCT-116 and SW620 were treated with 0, 1, or 10 microM retinol. Thirty minutes of retinol treatment resulted in a significant decrease in PI3K activity in both cell lines. To determine the mechanism by which retinol reduces PI3K activity, the levels and heterodimerization of the regulatory subunit, p85, and the catalytic subunit, p110, of PI3K were examined. Retinol treatment did not alter p85 or p110 protein levels or the heterodimerization of these subunits at any time point examined. To determine if retinol affected the ability of PI3K to phosphorylate the substrate, phosphatidylinositol (PI), PI3K was immunoprecipitated from control cells and incubated with 10 microg PI and increasing concentrations of retinol or 10 microg retinol and increasing concentrations of PI. Retinol decreased PI3K activity in a dose-responsive manner and increased PI suppressed the inhibitory effect of retinol on PI3K activity. Finally, the PI3K inhibitor, LY294002, mimicked the ability of retinol to decrease cell invasion. Computational modeling revealed that retinol may inhibit PI3K activity in a manner similar to that of wortmannin. Thus, a decrease in PI3K activity due to retinol treatment may confer the ability of retinol to inhibit ATRA-resistant colon cancer cell invasion.

Rosiglitazone inhibits metastasis development of a murine mammary tumor cell line LMM3

Background

Activation of peroxisome proliferator-activated receptors γ (PPARγ) induces diverse effects on cancer cells. The thiazolidinediones (TZDs), such as troglitazone and ciglitazone, are PPARγ agonists exhibiting antitumor activities; however, the underlying mechanism remains inconclusive. Rosiglitazone (RGZ), a synthetic ligand of PPARγ used in the treatment of Type 2 diabetes, inhibits growth of some tumor cells and is involved in other processes related to cancer progression. Opposing results have also been reported with different ligands on tumor cells. The purpose of this study was to determine if RGZ and 15d-PGJ₂ induce antitumor effects in vivo and in vitro on the murine mammary tumor cell line LMM3.

Methods

The effect on LMM3 cell viability and nitric oxide (NO) production of different doses of RGZ, 15-dPGJ₂, BADGE and GW9662 were determined using the MTS colorimetric assay and the Griess reaction respectively. In vivo effect of orally administration of RGZ on tumor progression was evaluated either on s.c. primary tumors as well as on experimental metastasis. Cell adhesion, migration (wound assay) and invasion in Transwells were performed. Metalloproteinase activity (MMP) was determined by zymography in conditioned media from RGZ treated tumor cells. PPARγ expression was detected by inmunohistochemistry in formalin fixed tumors and by western blot in tumor cell lysates.

Results

RGZ orally administered to tumor-bearing mice decreased the number of experimental lung metastases without affecting primary s.c. tumor growth. Tumor cell adhesion and migration, as well as metalloproteinase MMP-9 activity, decreased in the presence of 1 μM RGZ (non-cytotoxic dose). RGZ induced PPARγ protein expression in LMM3 tumors. Although metabolic activity -measured by MTS assay- diminished with 1–100 μM RGZ, 1 μM-treated cells recovered their proliferating capacity while 100 μM treated cells died. The PPARγ antagonist Biphenol A diglicydyl ether (BADGE) did not affect RGZ activity. On the contrary, the specific antagonist GW9662 completely abrogated RGZ-induced decrease in cell viability. A decrease in NO levels was detected in the presence of either 1 or 100 μM RGZ. The natural ligand 15d-PGJ₂ did not affect metabolic activity although it induced a significant decrease in NO production.

Conclusion

A significant decrease in the number of experimental LMM3 lung metastasis, but not on primary tumor growth, after oral RGZ administration was observed. In vitro, 100 μMRGZ also reduced cell viability and NO production, while no changes were observed in the presence of 15d-PGJ₂. BADGE did not reverse RGZ effect while the antagonist GW9662 completely abrogated it, suggesting a PPARγ- dependent mechanism. Inhibition of lung metastatic nodules by RGZ administered in vivo, might be associated with the observed decrease in MMP-9 expression, in cell adhesion, migration and invasion. RGZ augmented its expression. PPARγ was detected in cell lysates by western blot and by immunohistochemistry in tumors from RGZ-treated mice. In summary we can suggest that RGZ or any other TZDs might be possible future approaches in the treatment of metastasis of PPARγ-expressing cells.

The Roles of Dietary PPARgamma Ligands for Metastasis in Colorectal Cancer

Dietary peroxisome proliferator-activated receptor (PPAR)gamma ligands, linoleic acid (LA) and conjugated linoleic acid (CLA), showed anticancer effects in colorectal carcinoma cells. LA is metabolized by two pathways. Cyclooxygenase (COX)-2 produces procarcinogenic prostaglandin E2, whereas 15-lipoxygenase (LOX)-1 produces PPARgamma ligands. The 15LOX-1 pathway, which is dominant in colorectal adenomas, was downregulated and inversely COX-2 was upregulated in colorectal cancer. LA and CLA inhibited peritoneal metastasis of colorectal cancer cells in nude mice. The inhibitory effect was abrogated by PPARgamma antisense treatment. A continuous LA treatment provided cancer cells quiescence. These quiescent cells formed dormant nests in nude mice administrated LA. The quiescent and dormant cells showed downregulated PPARgamma and upregulated nucleostemin. Thus, short-term exposure to dietary PPARgamma ligands inhibits cancer metastasis, whereas consistent exposure to LA provides quiescent/dormant status with possible induction of cancer stem and/or progenitor phenotype. The complicated roles of dietary PPARgamma ligands are needed to examine further.

All-transRetinoic Acid Enhances Murine Dendritic Cell Migration to Draining Lymph Nodes via the Balance of Matrix Metalloproteinases and Their Inhibitors

Cancers escape immune surveillance through the manipulation of the host's immune system. Sequestration of dendritic cells (DCs) within tumor tissues and the subsequent inhibition of their migration is one of the several mechanisms by which tumors induce immunosuppression. In view of recent findings depicting the improvement of tumor immune responses in cancer patients following all-trans retinoic acid (ATRA) treatment, we sought to identify the effects of ATRA on DC mobility in the context of tumor immunotherapy. Our results demonstrate that ATRA, added to differentiating murine bone marrow progenitor cells, enhances the invasive capacity of the resulting DCs. Immature DCs injected intratumorally in mice show increased accumulation in draining lymph nodes, but not in nondraining lymph nodes and spleens, when differentiated in the presence of ATRA. The in vitro migration of mature DCs through the basement membrane matrix toward the lymphoid chemokines CCL19 and CCL21 is enhanced in these cells, albeit not in the presence of a matrix metalloproteinase (MMP) inhibitor. An increase in MMP production with a simultaneous decrease in the production of their inhibitors (tissue inhibitors of matrix metalloproteinase or TIMPs) is provoked by ATRA. This affects the MMP/TIMP balance in DCs, in particular that of MMP-9 and TIMP-1, favoring protease activity and thus allowing for enhanced DC mobilization. In conclusion, this study demonstrates that ATRA is capable of improving DC trafficking in a tumor milieu and, in view of the encouraging results obtained in the clinic, further supports the notion that ATRA might be a valuable chemical adjuvant to current immunotherapeutic strategies for cancer.

Retinol inhibits the invasion of retinoic acid-resistant colon cancer cells in vitro and decreases matrix metalloproteinase mRNA, protein, and activity levels

Retinol inhibits the growth of all-trans-retinoic acid (ATRA)-resistant human colon cancer cell lines through a retinoic acid receptor (RAR)-independent mechanism. The objectives of the current study were to determine if retinol inhibited the invasion of ATRA-resistant colon cancer cells independent of RAR and the effects of retinol on matrix metalloproteinases (MMPs). Retinol inhibited the migration and invasion of two ATRA-resistant colon cancer cell lines, HCT-116 and SW620, in a dose-dependent manner. To determine if transcription, particularly RAR-mediated transcription, or translation of new genes was required for retinol to inhibit cell invasion, cells were treated with retinol and cycloheximide, actinomycin D, or an RAR pan-antagonist. Treatment of cells with retinol and cycloheximide, actinomycin D, or an RAR pan-antagonist did not block the ability of retinol to inhibit cell invasion. In addition, retinol decreased MMP-1 mRNA levels in both cell lines, MMP-2 mRNA levels in the SW620 cell line, and MMP-7 and -9 mRNA levels in the HCT-116 cell line. Retinol also decreased the activity of MMP-2 and -9 and MMP-9 protein levels while increasing tissue inhibitor of MMP-1 media levels. In conclusion, retinol reduces the metastatic potential of ATRA-resistant colon cancer cells via a novel RAR-independent mechanism that may involve decreased MMP mRNA levels and activity.

Pro-MMP-2 activation by the PPARgamma agonist, ciglitazone, induces cell invasion through the generation of ROS and the activation of ERK

Peroxisome proliferator-activated receptor gamma (PPARgamma) is a nuclear receptor modulating a variety of biological functions including cancer cell proliferation and differentiation. However, the role of PPARgamma and its ligands in tumor invasion is unclear. To evaluate a possible role for PPARgamma ligands in tumor invasion, we examined whether PPARgamma agonists including pioglitazone, troglitazone, rosiglitazone, and ciglitazone could affect the activity of matrix metalloproteinases (MMPs) in the HT1080 cell line, a well-studied and well-characterized cell line for MMP research. The gelatin zymography assay showed that ciglitazone activated pro-MMP-2 significantly. In addition, ciglitazone increased the expression of MMP-2, which was accompanied by an increase of membrane type 1-MMP (MT1-MMP) expression. The PPARgamma antagonist, GW9662 attenuated the ciglitazone-induced PPARgamma activation but it did not affect the pro-MMP2 activation by ciglitazone, suggesting that the action of ciglitazone on the pro-MMP-2 activation bypassed the PPARgamma pathway. Antioxidants and various inhibitors of signal transduction were used to investigate the mechanism of ciglitazone-induced pro-MMP-2 activation. We found that the sustained production of reactive oxygen species (ROS) was required for pro-MMP-2 activation by ciglitazone. We also found that PB98059, an inhibitor of MEK-ERK, significantly blocked ciglitazone-induced pro-MMP-2 activation and that extracellular signal-regulated kinase (ERK) was hyperphosphorylated by ciglitazone. Moreover, cell invasion was significantly increased by ciglitazone in the HT1080 cell lines, whereas cell motility was not affected. This study suggests that ciglitazone-induced pro-MMP-2 activation increases PPARgamma-independent tumor cell invasion through ROS production and ERK activation in some types of cancer cells.

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.

PPARgamma activation by thiazolidinediones (TZDs) may modulate breast carcinoma outcome: the importance of interplay with TGFbeta signalling

The thiazolidinediones (TZDs) are a class of synthetic antidiabetic drugs exerting its action primarily upon acti-vation of the peroxisome proliferator-activated receptor-γ (PPARγ). Given the widespread incidence of diabetes type II and lifelong exposure of these patients to TZDs, there is a possibility that chronic treatment with TZD modifies clinical phenotypes of other common human diseases, for example breast carcinoma. There is evidence that TZDs act as breast carcinoma suppression agents, at least in the in vitro and animal models. Stimulation of the PPARγ by TZDs interferes with oestrogen receptor signalling, STAT5B and NF-κB signalling cascades. On the other hand, TZDs repress TGFβ signalling, a well-known suppressor of the initial stages of breast carcinoma development. Another layer of complexity arises at the later stages of tumour development, when TGFβ acts as a tumour promoter: its overexpression is associated with poor prognosis, higher degree of tumour vascularization and metastasis. Longitudinal studies of breast carcinoma development in chronic TZD users are needed. In this review, we dissect possible interplays between chronic exposure of breast tis-sue to TZDs and TGFβ signalling and predict influence of TZD exposure on cancer-related clinical outcome.

Catalase potentiates retinoic acid-induced THP-1 monocyte differentiation into macrophage through inhibition of peroxisome proliferator-activated receptor gamma

Macrophage differentiation plays a pivotal role in cardiovascular diseases and many other physiological processes. However, the role of reaction oxygen species in macrophage differentiation has not been elucidated. Here, we report functional characterization of catalase, an enzyme that degrades hydrogen peroxide (H(2)O(2)), in THP-1 monocyte differentiation. Treatment of THP-1 cells with catalase was able to synergize with all-trans retinoic acid (ATRA) to enhance macrophage differentiation, demonstrated by changes of cell adherence, cell cycle arrest, nitroblue tetrazolium reduction, and expression of differentiation markers including CD68, CD11b, and matrix metalloproteinase 9 (MMP9). ATRA could stimulate retinoic acid (RA) receptor-mediated transcription, but this was not affected by catalase. However, ATRA and catalase were capable of reducing transcriptional activity mediated by peroxisome proliferator-activated receptor gamma (PPARgamma). Consistently, PPARgamma antagonists enhanced, and PPARgamma agonists inhibited MMP9 expression stimulated by ATRA and catalase in THP-1 cells. Therefore, these data indicate that catalase is able to potentiate ATRA-induced macrophage differentiation by inhibition of PPARgamma activity, underscoring an important interplay between H(2)O(2), RA, and PPARgamma in macrophages.

The clinicopathological and prognostic significance of membrane type 1 matrix metalloproteinase (MT1-MMP) and MMP-9 according to their localization in invasive breast carcinoma

AIMS

To investigate the clinicopathological and prognostic significance of membrane type 1 matrix metalloproteinase (MT1-MMP) and MMP-9 proteins expression in invasive breast carcinoma and their relationship to tumour proliferation and expression of c-erbB2 and peroxisome proliferator-activated receptor (PPAR) gamma.

METHODS

Immunohistochemistry was carried out on 175 paraffin-embedded breast tissue specimens to detect MT1-MMP, MMP-9, oestrogen receptor (ER), progesterone receptor, c-erbB-2, Ki67, topoisomerase IIalpha (topo IIalpha) and PPARgamma protein expression.

RESULTS

Both MT1-MMP and MMP-9 were expressed in the cytoplasm of the malignant cells and the peritumoral stroma. Cytoplasmic MT1-MMP was more often observed in ER+ tumours (P = 0.022), of a lower nuclear grade (P = 0.020) and with reduced expression of Ki67 and topo IIalpha (P = 0.027 and P = 0.006, respectively). Moreover, cytoplasmic MT1-MMP was positively associated with MMP-9 (P = 0.010) and PPARgamma (P < 0.0001). Cytoplasmic MMP-9 was inversely associated with Ki67 (P = 0.034) and topo IIalpha (P = 0.004), whereas its relationship with MT1-MMP (P = 0.034) and PPARgamma (P = 0.024) was found to be positive. Stromal MMP-9 was more often observed in c-erbB2+ tumours (P = 0.043) and had an unfavourable impact on overall and relapse-free survival in both univariate (P = 0.0157 and P = 0.0274, respectively) and multivariate analyses (P = 0.007 and P = 0.024, respectively).

CONCLUSIONS

Cytoplasmic MT1-MMP and MMP-9 seem to be related to well-differentiated tumours, with a low proliferation potential, while stromal MMP-9 is associated with an aggressive tumour phenotype and is recognized as an independent poor prognostic indicator.

Peroxisome proliferator-activated receptor-gamma ligands inhibit proliferation and induce apoptosis in mantle cell lymphoma

Peroxisome proliferator-activated receptor-gamma, a nuclear receptor and transcription factor, and its natural and synthetic ligands have become a focus of novel approaches to induction of apoptosis in solid tumors and hematologic malignancies, including malignant B-lineage cells. The effect on mantle cell lymphoma, a subtype with dismal prognosis, has not yet been analyzed. We investigated the effect of 15-deoxy-delta-12,14-prostaglandin J2 (15d-PGJ2), pioglitazone (PGZ) or rosiglitazone (RGZ) on human mantle cell lymphoma cell lines (GRANTA-519, Hbl-2 and JeKo-1). Mantle cell lymphoma cell lines exhibited a high expression of Peroxisome proliferator-activated receptor-gamma protein in Western blot analysis. MTT assays revealed anti-proliferative effects induced by both 15d-PGJ2, the natural activator of Peroxisome proliferator-activated receptor-gamma, and PGZ and RGZ, synthetic Peroxisome proliferator-activated receptor-gamma ligands, in a dose-dependent manner. At a dose of 50 micromol/l, 15d-PGJ2 induced growth inhibition in all cell lines. The anti-proliferative effect of PGZ and RGZ was slightly lower. Induction of apoptosis was indicated by annexin V staining. At a dose of 50 micromol/l, 15d-PGJ2 led to apoptosis in all cell lines (87-99%) after 48 h of incubation. Again, the apoptotic effect with thiazolidinediones was slightly lower at the same dose level. This is the first study evaluating Peroxisome proliferator-activated receptor-gamma expression and its therapeutic implications in human mantle cell lymphoma cells. Thiazolidinediones comprise anti-lymphoma activity in vitro and should be further explored for the treatment of mantle cell lymphoma.

Antineoplastic effects of rosiglitazone and PPARgamma transactivation in neuroblastoma cells

Neuroblastoma (NB) is the most common extracranial solid tumour in infants. Unfortunately, most children present with advanced disease and have a poor prognosis. In the present study, we evaluated the role of the peroxisome proliferator-activated receptor γ (PPARγ) agonist rosiglitazone (RGZ) in two NB cell lines (SK-N-AS and SH-SY5Y), which express PPARγ. Rosiglitazone decreased cell proliferation and viability to a greater extent in SK-N-AS than in SH-SY5Y. Furthermore, 20 μM RGZ significantly inhibited cell adhesion, invasiveness and apoptosis in SK-N-AS, but not in SH-SY5Y. Because of the different response of SK-N-AS and SH-SY5Y cells to RGZ, the function of PPARγ as a transcriptional activator was assessed. Noticeably, transient transcription experiments with a PPARγ responsive element showed that RGZ induced a three-fold increase of the reporter activity in SK-N-AS, whereas no effect was observed in SH-SY5Y. The different PPARγ activity may be likely due to the markedly lower amount of phopshorylated (i.e. inactive) protein observed in SK-N-AS. To our knowledge, this is the first demonstration that the differential response of NB cells to RGZ may be related to differences in PPARγ transactivation. This finding indicates that PPARγ activity may be useful to select those patients, for whom PPARγ agonists may have a beneficial therapeutic effect.

Conjugated linoleic acid reduced metastasized LL2 tumors in mouse peritoneum

The effect of conjugated linoleic acid (CLA) on pre-existent peritoneal metastasis was examined by mouse peritoneal metastasis models. The cell growth of LL2 mouse cancer cells was suppressed by CLA in a dose-dependent manner. CLA-induced growth inhibition was recovered by the exposure to antisense S-oligodeoxynucleotide for peroxisome proliferator-activated receptor (PPAR)-gamma. C57B6 mice were inoculated with LL2 cells into their peritoneal cavity. Two weeks after inoculation, colonized peritoneal cancer foci (2.2+/-0.4 mm in diameter) were treated with CLA administrated intraperitoneally (200 or 600 pmol/mouse, twice a week). CLA treatment decreased the number of peritoneal tumors: 8.7+/-0.6, 5.7+/-0.6, and 2.3+/-0.6 in untreated, 200 pmol/mouse CLA, and 600 pmol/mouse CLA groups, respectively (P<0.0001). CLA treatment decreased the size of peritoneal tumors: 3.7+/-1.5, 1.3+/-0.5, and 1.0+/-0.4 mm in untreated, 200 pmol/mouse CLA, and 600 pmol/mouse CLA groups, respectively (P<0.0001). In CLA-treated tumors, proliferating cells were decreased (P<0.0001), whereas apoptotic cells were increased (P=0.0010). CLA-treated LL2 tumors showed decrease of PPARgamma and EGFR proteins and increase of BAX protein in comparison with untreated tumors. These findings suggest that CLA possesses anti-tumor capability to peritoneal metastasis.

Peroxisome proliferator-activated receptor-gamma ligands for the treatment of breast cancer

Pioglitazone and rosiglitazone are thiazolidinediones used for the treatment of Type 2 diabetes mellitus. They modulate glucose and fat metabolism, mainly by binding to the nuclear hormone receptor peroxisome proliferator-activated receptor (PPAR)-gamma. PPAR-gamma signalling is involved in a number of other disease conditions including cancer. In breast cancer cells, PPAR-gamma ligands inhibit proliferation and induce apoptosis both in vitro and in vivo. PPAR-gamma ligands also inhibit tumour angiogenesis and invasion. The only published clinical trial using a PPAR-gamma ligand in patients with metastatic breast cancer failed to show any clinical benefits. The mechanism of action of the thiazolidinediones in breast cancer cells is not fully understood but involves interactions with other nuclear hormone receptors, transcriptional co-activators and repressors as well as PPAR-gamma-independent effects. A better understanding of these mechanisms will be needed before PPAR-gamma ligands may be useful in the treatment of breast cancer patients.

Conjugated linoleic acid inhibits peritoneal metastasis in human gastrointestinal cancer cells

The effect of conjugated linoleic acid (CLA) on peritoneal metastasis was examined by in vitro treatment of cancer cells and mouse peritoneal metastasis models. First, cell growth of MKN28 human gastric cancer cells and Colo320 human colon cancer cells was suppressed by CLA in a dose-dependent manner with an increment in apoptosis. CLA significantly inhibited invasion into type IV collagen-coated membrane of MKN28 and Colo320 cells (p < 0.05). CLA-induced growth inhibition was recovered by the exposure to antisense S-oligodeoxynucleotide for peroxisome proliferator-activated receptor (PPAR)-gamma in both cell lines. BALB/c nu-nu mice were inoculated with MKN28 and Colo320 cells into their peritoneal cavity, and administrated with CLA intraperitoneally (weekly, 4 times). CLA treatment did not affect food intake or weight gain of mice. CLA treatment significantly decreased metastatic foci of both cells in the peritoneal cavity (p < 0.005). Survival rate in mice inoculated with MKN28 or Colo320 cells was significantly recovered by CLA treatment (p = 0.0025 and 0.0052, respectively). Protein production in MKN28 and Colo320 cells treated with CLA showed a decrease in epidermal growth factor receptor and transforming growth factor-alpha and an increase in Bax. These findings suggest that CLA inhibits metastasis of human gastric and colon cancer cells.

Growth inhibition and apoptosis in human Philadelphia chromosome-positive lymphoblastic leukemia cell lines by treatment with the dual PPARalpha/gamma ligand TZD18

Treatment of adult Philadelphia chromosome-positive lymphocytic leukemia is rarely successful. We report here the effects of TZD18, a novel dual ligand specific for peroxisome proliferator-activated receptor alpha and gamma (PPARalpha/gamma) on Ph(+) lymphocytic leukemia cell lines BV173, SD1, and SupB-15. Exposure of these cells to TZD18 resulted in growth inhibition in a dose- and time-dependent manner that was associated with G(1) cell cycle arrest. This effect was much stronger than that mediated by the PPARgamma ligand pioglitazone (PGZ), which also belongs to the thiazolidinediones (TZD) class of ligands. However, it may not be mediated through PPARgamma or PPARalpha activation because antagonists of PPARgamma and PPARalpha cannot reverse it. Study of the key regulators of cell cycle progression by Western blot analysis showed that the expression of the cyclin-dependent kinase inhibitor (CDKI) p27(kip1), but not that of p21(cip1), was enhanced, whereas that of c-Myc, cyclin E, cyclin D2, and cyclin-dependent kinases 2 and 4 (CDK-2 and CDK-4) was decreased when these cells were treated with TZD18 (10 or 20 microM). Therefore, the up-regulation of p27(kip1) and the down-regulation of CDK-2 and CDK-4 may, at least in part, account for the G(1) cell cycle arrest. Furthermore, a remarkable induction of apoptosis was observed in the cells treated with this dual ligand. No obvious alteration of bcl-2 protein level occurred, but bax was up-regulated in these TZD18-treated cells. Activation of caspase 8 and caspase 9 by TZD18 was also observed. Importantly, NF-kappaB DNA-binding activity was markedly decreased by the TZD18 treatment. In addition, TZD18 enhanced the growth inhibitory effect of imatinib, a specific tyrosine kinase inhibitor therapeutically used in the treatment of Ph(+) leukemia. Overall, our findings strongly suggest that TZD18 may offer a new therapeutic approach to aid in the treatment of Ph(+) lymphocytic leukemia.

Expression of tissue inhibitor of matrix metalloproteinases-1 during aging in rat liver

AIM: To investigate the expression and role of tissue inhibitor of matrix metalloproteinases-1 (TIMP-1) during natural aging in rat liver and to detect the expression of matrix metalloproteinase-2 (MMP-2) and MMP-9.

METHODS: The rats were divided into 3-mo-old group (n = 5), 10-mo-old group (n = 5) and 24-mo-old group (n = 5). Histopathologic changes of liver were observed with HE and Masson stain. The location and protein expressions of TIMP-1 were determined by immunohistochemistry and Western blot; message RNA (mRNA) levels were measured in livers from rats of various ages by semi-quantitative reverse transcriptional polymerase chain reaction (RT-PCR). In addition, the expression of MMP-2 and MMP-9 was assessed by RT-PCR and Western blot.

RESULTS: Histologic examination showed that the aging liver had excessive fatty degeneration and collagen deposition. Immunohistochemical staining showed that TIMP-1 related antigen in livers was located in cytoplasm. The protein expression of TIMP-1 was significantly higher in the oldest animals and the mRNA expression was increased significantly in the 24-mo-old rats (t = 4.61, P = 0.002<0.05, 24-vs 10-mo-old rats; t = 4.31, P = 0.003<0.05, 24- vs 3-mo-old rats). The expression of MMP-2 and MMP-9 had no change during aging; the ratios TIMP-1/MMP-2 and TIMP-1/MMP-9 in aging liver were significantly higher than those in maturation and young livers.

CONCLUSION: TIMP-1 may play an important role in the process of liver aging.

PPARgamma expression in breast cancer: clinical value and correlation with ERbeta

AIMS

To examine the expression of peroxisome proliferator-activated receptor gamma (PPARgamma) in invasive breast carcinoma in relation to known clinicopathological features, ERbeta, and relapse-free and overall patient survival. PPARgamma is a ligand-activated transcriptional factor that regulates the transcription of various target genes and has been implicated in human breast cancer.

METHODS AND RESULTS

We performed immunohistochemistry to detect PPARgamma, ERalpha, PR and ERbeta in 170 infiltrative breast carcinomas. The results were subjected to statistical analysis. PPARgamma was detected in the cytoplasm of 58% of breast carcinoma samples. PPARgamma did not differ with regard to any of the clinicopathological parameters except for histological grade, to which it was found to be inversely correlated (P = 0.019), and ERbeta, to which it was positively related (P = 0.016). As regards relapse-free survival, in univariate statistical analysis PPARgamma was found to exert a marginally favourable impact on all the patients (P = 0.076), but a strong one on patients with ductal carcinoma (P = 0.027), whereas Cox's regression analysis depicted PPARgamma to be an independent prognosticator for patients with ductal carcinoma (P = 0.039). No association was found between PPARgamma expression and overall survival.

CONCLUSION

These results indicate the favourable impact of PPARgamma expression on disease-free survival of patients with ductal breast carcinoma and its possible cooperation with ERbeta in exerting that favourable effect.

The Nonthiazolidinedione Tyrosine-Based Peroxisome Proliferator-Activated Receptor γ Ligand GW7845 Induces Apoptosis and Limits Migration and Invasion of Rat and Human Glioma Cells

Despite new approaches, treatment options for malignant gliomas are still limited, calling for further development of therapeutic strategies. The peroxisome proliferator-activated receptor (PPAR)gamma, a member of the nuclear hormone receptor family, represents a possible new target for neoplastic therapies. Synthetic PPARgamma agonists were developed and are already in clinical use for the treatment of type II diabetes, since PPARgamma plays a crucial role in lipid metabolism and regulation of insulin sensitivity. Beyond these metabolic effects, PPARgamma agonists exhibit antineoplastic effects in various malignant tumor cells. Here, we investigated the antineoplastic effects of the nonthiazolidinedione tyrosine-based PPARgamma ligand (S)-2-(1-carboxy-2-{4-[2-(5-methyl-2-phenyloxazol-4-yl)ethoxy]phenyl}ethylamino)benzoic acid methyl ester (GW7845) in rat and human glioma cells. GW7845 reduced cellular viability of rat C6 glioma and human glioma cells in a time-dependent manner. Analysis of GW7845-treated tumor cells revealed induction of apoptotic cell death as determined by terminal deoxynucleotidyl transferase dUTP nick-end labeling staining and cleaved caspase-3 activation. Furthermore, GW7845 reduced proliferation of C6 glioma cells as measured by Ki-67 immunore-activity. There was also a reduction of migration and invasion, assessed by Boyden chamber and spheroid experiments. Together, these data indicate that the PPARgamma agonist GW7845 may be of potential use in treatment of malignant gliomas.