gw9662 and Carcinoma--Non-Small-Cell-Lung

Peroxisome proliferator-activated receptor γ (PPARγ) agonists frequently induce cell death in human non-small-cell lung cancer (NSCLC) cells. However, majority of NSCLC patients acquire resistance after cancer therapy, and it is still unclear.. In this study we investigated the apoptotic mechanism and the anti-cancer effects of a novel purine-based PPARγ agonist, CB11 (8-(2-aminophenyl)-3-butyl-1,6,7-trimethyl-1H-imidazo[2,1-f]purine-2,4(3H,8H)-dione), on human NSCLC cells. CB11 mediates PPARγ-dependent cell death, reactive oxygen species (ROS) production, mitochondrial membrane potential (MMP) collapse, cell cycle arrest, lactate dehydrogenase (LDH) cytotoxicity, and caspase-3 activity in human NSCLC cells.. CB11 causes cell death via ROS-mediated ATM-p53-GADD45α signalling in human NSCLC cells, and diphenyleneiodonium (DPI), an NADPH oxidase inhibitor, decreases cell death by inhibiting CB11-mediated ATM signalling. In a xenograft experiment, CB11 dramatically reduced tumour volume when compared to a control group. Furthermore, CB11 induced cell death by inhibiting epithelial-to-mesenchymal transition (EMT) under radiation exposure in radiation-resistant human NSCLC cells. However, PPARγ deficiency inhibited cell death by blocking the ATM-p53 axis in radiation/CB11-induced radiation-resistant human NSCLC cells.. Taken together, our results suggest that CB11, a novel PPARγ agonist, may be a novel anti-cancer agent, and it could be useful in a therapeutic strategy to overcome radio-resistance in radiation-exposed NSCLC.

Topics: 3T3 Cells; Adipocytes; Anilides; Animals; Apoptosis; Ataxia Telangiectasia Mutated Proteins; Azo Compounds; Carcinoma, Non-Small-Cell Lung; Caspase 3; Caspase 9; Cell Cycle Checkpoints; Cell Cycle Proteins; Cell Death; Cell Differentiation; Cell Line, Tumor; DNA Damage; Epithelial-Mesenchymal Transition; Female; Humans; Imidazoles; L-Lactate Dehydrogenase; Ligands; Luciferases; Lung Neoplasms; Membrane Potential, Mitochondrial; Mice; Mice, Inbred BALB C; Mice, Nude; Onium Compounds; PPAR gamma; Purines; Radiation Tolerance; Reactive Oxygen Species; RNA, Small Interfering; Signal Transduction; Thiazolidinediones; Tumor Burden; Tumor Suppressor Protein p53

The antitumorigenic mechanism of the selective cyclooxygenase-2 (COX-2) inhibitor celecoxib is still a matter of debate. Among different structurally related COX-2 inhibitors, only celecoxib was found to cause apoptosis and cell death of human lung cancer cells (IC₅₀ values of 19.96 µM [A549], 12.48 µM [H460], and 41.39 µM [H358]) that was paralleled by a time- and concentration-dependent upregulation of COX-2 and peroxisome proliferator-activated receptor γ (PPARγ) at mRNA and protein levels. Apoptotic death of celecoxib-treated cancer cells was suppressed by the PPARγ antagonist GW9662 and by siRNA targeting PPARγ and, surprisingly, also by the selective COX-2 inhibitor NS-398 and siRNA targeting COX-2. NS-398 (1 µM) was shown to suppress celecoxib-induced COX-2 activity. Among the COX-2-dependent prostaglandins (PG) induced upon celecoxib treatment, PGD₂ and 15-deoxy-Δ¹²,¹⁴-PGJ₂ were found to induce a cytosol-to-nucleus translocation of PPARγ as well as a PPARγ-dependent apoptosis. Celecoxib-elicited PPARγ translocation was inhibited by NS-398. Finally, a COX-2- and PPARγ-dependent cytotoxic action of celecoxib was proven for primary human lung tumor cells. Together, our data demonstrate a proapoptotic mechanism of celecoxib involving initial upregulation of COX-2 and PPARγ and a subsequent nuclear translocation of PPARγ by COX-2-dependent PGs.

Topics: Anilides; Antineoplastic Agents; Apoptosis; Carcinoma, Non-Small-Cell Lung; Celecoxib; Cell Line, Tumor; Cell Nucleus; Cyclooxygenase 2; Cyclooxygenase 2 Inhibitors; Enzyme Induction; Gene Expression Regulation, Neoplastic; Humans; Intracellular Space; Lung Neoplasms; Nitrobenzenes; PPAR gamma; Prostaglandins; Protein Transport; Pyrazoles; Sulfonamides

The primary goal of the study was to investigate how peroxisome proliferator-activated receptor γ (PPARγ) played a critical role in the protection of H460 cell, one of the non-small cell lung cancer (NSCLC) cells with multidrug resistance, from transforming growth factor β (TGFβ)-mediated mitoinhibition. In the study, TGFβ resistance of H460 cell was first confirmed by analyses of PPARγ expression, its interaction with TGFβ-induced Smad3 and phospho-Smad3 (p-Smad3) and survival of H460. Results showed that enable to escape from G2/M phase arrest, H460 cell had higher resistance to TGFβ-mediated mitoinhibition than CH27 (a drug sensitive control). TGFβ significantly increased PPARγ expression of H460 but not of CH27 cell whereas nuclear accumulation of p-Smad3 was only limited to CH27, the latter was believed to contribute to the induction of P(21 waf1/cip1) and cyclin B1, cell cycle arrest at G2/M phase and TGFβ-mediated mitoinhibition of CH27 cell. TGFβ-induced PPARγ of H460 cell was further demonstrated to bind to Smad3 and p-Smad3, and GW9662 (PPARγ inhibitor) or PPARγ-specific shRNA could disrupt the binding. GW9662 also increased the nuclear accumulation of p-Smad3 that eventually led to the reduction of TGFβ resistance of H460. A transient knockdown of PPARγ with shRNA revealed a similar effect as GW9662. In addition, activation of P(38) instead of ERK played a critical role in TGFβ-induced expression of PPARγ, which subsequently activated RhoA in H460 cell.

Topics: Anilides; Apoptosis; Blotting, Western; Carcinoma, Non-Small-Cell Lung; Cell Cycle; Cell Line, Tumor; Cell Nucleus; Cyclooxygenase 2; Cyclooxygenase 2 Inhibitors; Flavonoids; Flow Cytometry; Gene Expression Regulation, Neoplastic; Humans; Imidazoles; Immunoprecipitation; Mitogen-Activated Protein Kinases; PPAR gamma; Protein Binding; Pyridines; rhoA GTP-Binding Protein; RNA, Small Interfering; Signal Transduction; Smad3 Protein; Transforming Growth Factor beta; Trypan Blue

Emerging preclinical data suggests that tea possess anticarcinogenic and antimutagenic properties. We therefore hypothesize that white tea extract (WTE) is capable of favorably modulating apoptosis, a mechanism associated with lung tumorigenesis. We examined the effects of physiologically relevant doses of WTE on the induction of apoptosis in non-small cell lung cancer cell lines A549 (adenocarcinoma) and H520 (squamous cell carcinoma) cells. We further characterized the molecular mechanisms responsible for WTE-induced apoptosis, including the induction of peroxisome proliferator-activated receptor-gamma (PPAR-gamma) and the 15-lipoxygenase (15-LOX) signaling pathways. We found that WTE was effective in inducing apoptosis in both A549 and H520 cells, and inhibition of PPAR-gamma with GW9662 partially reversed WTE-induced apoptosis. We further show that WTE increased PPAR-gamma activation and mRNA expression, concomitantly increased 15(S)-hydroxy-eicosatetraenoic acid release, and upregulated 15-LOX-1 and 15-LOX-2 mRNA expression by A549 cells. Inhibition of 15-LOX with nordihydroguaiaretic acid (NGDA), as well as caffeic acid, abrogated WTE-induced PPAR-gamma activation and upregulation of PPAR-gamma mRNA expression in A549 cells. WTE also induced cyclin-dependent kinase inhibitor 1A mRNA expression and activated caspase-3. Inhibition of caspase-3 abrogated WTE-induced apoptosis. Our findings indicate that WTE is capable of inducing apoptosis in non-small cell lung cancer cell lines. The induction of apoptosis seems to be mediated, in part, through the upregulation of the PPAR-gamma and 15-LOX signaling pathways, with enhanced activation of caspase-3. Our findings support the future investigation of WTE as an antineoplastic and chemopreventive agent for lung cancer.

Topics: Anilides; Apoptosis; Arachidonate 15-Lipoxygenase; Carcinoma, Non-Small-Cell Lung; Catechin; Drug Evaluation, Preclinical; Gene Expression Regulation, Enzymologic; Gene Expression Regulation, Neoplastic; Hormone Antagonists; Humans; Hydroxyeicosatetraenoic Acids; Lung Neoplasms; Plant Extracts; PPAR gamma; Tea; Tumor Cells, Cultured