Preclinical evaluation of the nonsteroidal anti-inflammatory agent celecoxib on malignant mesothelioma chemoprevention

Synthetic Secoisolariciresinol Diglucoside (LGM2605) Prevents Asbestos-Induced Inflammation and Genotoxic Cell Damage in Human Mesothelial Cells

Although alveolar macrophages play a critical role in malignant transformation of mesothelial cells following asbestos exposure, inflammatory and oxidative processes continue to occur in the mesothelial cells lining the pleura that may contribute to the carcinogenic process. Malignant transformation of mesothelial cells following asbestos exposure occurs over several decades; however, amelioration of DNA damage, inflammation, and cell injury may impede the carcinogenic process. We have shown in an in vitro model of asbestos-induced macrophage activation that synthetic secoisolariciresinol diglucoside (LGM2605), given preventively, reduced inflammatory cascades and oxidative/nitrosative cell damage. Therefore, it was hypothesized that LGM2605 could also be effective in reducing asbestos-induced activation and the damage of pleural mesothelial cells. LGM2605 treatment (50 µM) of huma n pleural mesothelial cells was initiated 4 h prior to exposure to asbestos (crocidolite, 20 µg/cm2). Supernatant and cells were evaluated at 0, 2, 4, and 8 h post asbestos exposure for reactive oxygen species (ROS) generation, DNA damage (oxidized guanine), inflammasome activation (caspase-1 activity) and associated pro-inflammatory cytokine release (IL-1β, IL-18, IL-6, TNFα, and HMGB1), and markers of oxidative stress (malondialdehyde (MDA) and 8-iso-prostaglandin F2a (8-iso-PGF2α). Asbestos induced a time-dependent ROS increase that was significantly (p < 0.0001) reduced (29.4%) by LGM2605 treatment. LGM2605 pretreatment also reduced levels of asbestos-induced DNA damage by 73.6% ± 1.0%. Although levels of inflammasome-activated cytokines, IL-1β and IL-18, reached 29.2 pg/mL ± 0.7 pg/mL and 43.9 pg/mL ± 0.8 pg/mL, respectively, LGM2605 treatment significantly (p < 0.0001) reduced cytokine levels comparable to baseline (non-asbestos exposed) values (3.8 pg/mL ± 0.2 pg/mL and 5.4 pg/mL ± 0.2 pg/mL, respectively). Furthermore, levels of IL-6 and TNFα in asbestos-exposed mesothelial cells were high (289.1 pg/mL ± 2.9 pg/mL and 511.3 pg/mL ± 10.2 pg/mL, respectively), while remaining undetectable with LGM2605 pretreatment. HMGB1 (a key inflammatory mediator and initiator of malignant transformation) release was reduced 75.3% ± 0.4% by LGM2605. Levels of MDA and 8-iso-PGF2α, markers of oxidative cell injury, were significantly (p < 0.001) reduced by 80.5% ± 0.1% and 76.6% ± 0.3%, respectively. LGM2605, given preventively, reduced ROS generation, DNA damage, and inflammasome-activated cytokine release and key inflammatory mediators implicated in asbestos-induced malignant transformation of normal mesothelial cells.

Biomarkers for Malignant Pleural Mesothelioma-A Novel View on Inflammation

Malignant pleural mesothelioma (MPM) is an aggressive disease with limited treatment response and devastating prognosis. Exposure to asbestos and chronic inflammation are acknowledged as main risk factors. Since immune therapy evolved as a promising novel treatment modality, we want to reevaluate and summarize the role of the inflammatory system in MPM. This review focuses on local tumor associated inflammation on the one hand and systemic inflammatory markers, and their impact on MPM outcome, on the other hand. Identification of new biomarkers helps to select optimal patient tailored therapy, avoid ineffective treatment with its related side effects and consequently improves patient's outcome in this rare disease. Additionally, a better understanding of the tumor promoting and tumor suppressing inflammatory processes, influencing MPM pathogenesis and progression, might also reveal possible new targets for MPM treatment. After reviewing the currently available literature and according to our own research, it is concluded that the suppression of the specific immune system and the activation of its innate counterpart are crucial drivers of MPM aggressiveness translating to poor patient outcome.

Scientific Advances and New Frontiers in Mesothelioma Therapeutics

Malignant pleural mesothelioma (MPM) is a rare and aggressive cancer that arises from the mesothelial surface of the pleural and peritoneal cavities, the pericardium, and rarely, the tunica vaginalis. The incidence of MPM is expected to increase worldwide in the next two decades. However, even with the use of multimodality treatment, MPM remains challenging to treat, with a 5-year survival rate of less than 5%. The International Association for the Study of Lung Cancer has gathered experts in different areas of mesothelioma research and management to summarize the most significant scientific advances and new frontiers related to mesothelioma therapeutics.

Antiproliferative Activity of Pt(IV) Conjugates Containing the Non-Steroidal Anti-Inflammatory Drugs (NSAIDs) Ketoprofen and Naproxen †

Cisplatin and several non-steroidal anti-inflammatory drugs (NSAIDs) have been proven to act synergistically or at least additively on several tumor cell lines. Dual-action cisplatin-based Pt(IV) combos containing ketoprofen and naproxen offer good antiproliferative performance on a panel of human tumor cell lines, including a malignant pleural mesothelioma (MPM) one, a very chemoresistant tumor. The main reason of the increased activity relies on the enhanced lipophilicity of these Pt(IV) conjugates that in turn promotes increased cellular accumulation. A quick Pt(IV)→Pt(II) reduction generates the active cisplatin metabolite. The NSAID adjuvant action seems to be almost independent from cyclooxygenase-2 (COX-2) expression in the tumor cells under investigation (lung A-549, colon HT-29, HCT 116, SW480, ovarian A2780, and biphasic MPM MSTO-211H), but it seems to rely (at least in part) on the activation of the NSAID activated gene, NAG-1 (a member of the transforming growth factor beta, TGF-β, superfamily), which has been suggested to be involved in NSAID antiproliferative activity.

The resistance related to targeted therapy in malignant pleural mesothelioma: Why has not the target been hit yet?

Malignant pleural mesothelioma (MPM) is an aggressive tumor of the pleura with a poor prognosis. The most active first-line regimens are platinum compounds and pemetrexed. There is no standard second-line treatment in MPM. Advances in the understanding of tumor molecular biology have led to the development of several targeted treatments, which have been evaluated in clinical trials. Unfortunately none of the explored targeted treatments can currently be recommended as routine treatment in MPM. We reviewed the biological pathways involved in MPM, the clinical trials about targeted therapy, and possible related mechanisms of resistance. We suggest that specific genetic markers are needed as targets of selective therapy. By this way the selection of patients based on the molecular profile may facilitate a therapeutic strategy that allows the use of the most appropriate drug for each patient.

Latest developments in our understanding of the pathogenesis of mesothelioma and the design of targeted therapies

Malignant mesothelioma is an aggressive cancer whose pathogenesis is causally linked to occupational exposure to asbestos. Familial clusters of mesotheliomas have been observed in settings of genetic predisposition. Mesothelioma incidence is anticipated to increase worldwide in the next two decades. Novel treatments are needed, as current treatment modalities may improve the quality of life, but have shown modest effects in improving overall survival. Increasing knowledge on the molecular characteristics of mesothelioma has led to the development of novel potential therapeutic strategies, including: molecular targeted approaches, that is the inhibition of vascular endothelial growth factor with bevacizumab; immunotherapy with chimeric monoclonal antibody, immunotoxin, antibody drug conjugate, vaccine and viruses; inhibition of asbestos-induced inflammation, that is aspirin inhibition of HMGB1 activity may decrease or delay mesothelioma onset and/or growth. We elaborate on the rationale behind new therapeutic strategies, and summarize available preclinical and clinical results, as well as efforts still ongoing.

Biocompatibility and intradiscal application of a thermoreversible celecoxib-loaded poly-N-isopropylacrylamide MgFe-layered double hydroxide hydrogel in a canine model

Introduction

Chronic low back pain due to intervertebral disc (IVD) degeneration is associated with increased levels of inflammatory mediators. Current medical treatment consists of oral anti-inflammatory drugs to alleviate pain. In this study, the efficacy and safety of a novel thermoreversible poly-N-isopropylacrylamide MgFe-layered double hydroxide (pNIPAAM MgFe-LDH) hydrogel was evaluated for intradiscal controlled delivery of the selective cyclooxygenase (COX) 2 inhibitor and anti-inflammatory drug celecoxib (CXB).

Methods

Degradation, release behavior, and the ability of a CXB-loaded pNIPAAM MgFe-LDH hydrogel to suppress prostaglandin E₂ (PGE₂) levels in a controlled manner in the presence of a proinflammatory stimulus (TNF-α) were evaluated in vitro. Biocompatibility was evaluated histologically after subcutaneous injection in mice. Safety of intradiscal application of the loaded and unloaded hydrogels was studied in a canine model of spontaneous mild IVD degeneration by histological, biomolecular, and biochemical evaluation. After the hydrogel was shown to be biocompatible and safe, an in vivo dose–response study was performed in order to determine safety and efficacy of the pNIPAAM MgFe-LDH hydrogel for intradiscal controlled delivery of CXB.

Results

CXB release correlated to hydrogel degradation in vitro. Furthermore, controlled release from CXB-loaded hydrogels was demonstrated to suppress PGE₂ levels in the presence of TNF-α. The hydrogel was shown to exhibit a good biocompatibility upon subcutaneous injection in mice. Upon intradiscal injection in a canine model, the hydrogel exhibited excellent biocompatibility based on histological evaluation of the treated IVDs. Gene expression and biochemical analyses supported the finding that no substantial negative effects of the hydrogel were observed. Safety of application was further confirmed by the absence of clinical symptoms, IVD herniation or progression of degeneration. Controlled release of CXB resulted in a nonsignificant maximal inhibition (approximately 35 %) of PGE₂ levels in the mildly degenerated canine IVDs.

Conclusions

In conclusion, this study showed biocompatibility and safe intradiscal application of an MgFe LDH-pNIPAAM hydrogel. Controlled release of CXB resulted in only limited inhibition of PGE₂ in this model with mild IVD degeneration, and further studies should concentrate on application of controlled release from this type of hydrogel in animal models with more severe IVD degeneration.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-015-0727-x) contains supplementary material, which is available to authorized users.

The hexacarbonyldicobalt derivative of aspirin acts as a CO-releasing NSAID on malignant mesothelioma cells

The antiproliferative activity of the aspirin derivative [2-acetoxy-(2-propynyl)benzoate]hexacarbonyldicobalt (Co-ASS) and its analogue hexacarbonyl[μ-(2-ethylphenyl)methanol]dicobalt (Co-EPM) was investigated on malignant pleural mesothelioma (MPM) cell lines, having an epithelioid or a sarcomatoid phenotype. In sarcomatoid cell lines Co-ASS was more potent than Co-EPM and the prototypal metallo-drug cisplatin, and induced cell death through the intrinsic apoptotic pathway, associated with a strong NF-κB inhibition. In contrast, both Co-ASS and Co-EPM showed only a modest cytostatic activity against epithelioid MPM cells. Co-EPM induced an increase of senescent cells, while Co-ASS did not; the different outcomes were traced back to the organic (aspirin-like) portion of the molecule. Both Co-EPM and Co-ASS significantly reduced reactive oxygen/nitrogen species (ROS/RNS), and in turn nitrites, suggesting that the hexacarbonyldicobalt moiety may deliver CO within the cell, acting as a CO-releasing molecule (CO-RM). In perspective, Co-ASS would be better considered as a CO-NSAID agent (a CO-releasing molecule retaining the NSAID properties similar to NO- and H2S-NSAIDs) than as an antitumor drug candidate.

Proteomic (antibody microarray) exploration of the molecular mechanism of action of the specific COX-2 inhibitor DuP 697

We have previously shown that specific COX-2 inhibitors, including DuP 697, have anti-proliferative effects on mesothelioma cells and potentiate the cytotoxicity of pemetrexed. Here, we used a novel proteomic approach to explore the mechanism of action of this agent. COX-2-positive cell lines MSTO-211H (mesothelioma) and A549 (lung cancer) were exposed to DuP 697 for 72 h. Drug carrier only was added to control cells. Extracted proteins from treated and control cells were analysed using a comparative proteomic platform. Differentially expressed proteins, identified by the Panorama Xpress Profiler725 antibody microarray were submitted to Ingenuity Pathway Analysis. A total of 32 unique differentially expressed proteins were identified with a significant (>1.8-fold) difference in expression between treated and untreated cells in at least one cell line. Five molecules, BCL2L1 (Bcl-xL), BID, CHUK (IKK), FASLG and RAF1, were mapped to the Apoptosis Signaling pathway following Ingenuity Pathway Analysis. BCL2L1 (Bcl-xL) and BID were analysed using immuno-blotting and differential expression was confirmed. Proteomic (antibody microarray) analysis suggests that the mechanism of action of DuP 697 may be exerted via the induction of apoptosis. The antibody microarray platform can be utilised to explore the molecular mechanism of action of novel anticancer agents.

Predictive role of plasma vascular endothelial growth factor for the effect of celecoxib in advanced non-small cell lung cancer treated with chemotherapy

AIM OF THE STUDY

The primary purpose of this study is to investigate if pretreatment plasma levels of vascular endothelial growth factor (VEGF) are predictive of the effect of celecoxib on survival in advanced non-small cell lung cancer (NSCLC) treated with palliative chemotherapy. A secondary objective is to describe the course of plasma VEGF levels during and after treatment with cytotoxic chemotherapy combined with celecoxib or placebo.

METHODS

In a previously published double-blind multicenter phase III trial, 316 patients with NSCLC stage IIIB or IV and World Health Organisation (WHO) performance status 0-2 were randomised to receive celecoxib 400mg b.i.d. or placebo in combination with two-drug platinum-based chemotherapy. Chemotherapy cycle length was three weeks and planned duration of chemotherapy was four cycles. Celecoxib was given for a maximum of one year but was stopped earlier in case of disease progression or prohibitive toxicity. In a subset of patients, plasma VEGF levels were examined at onset of treatment and at 6, 12 and 20 weeks.

RESULTS

VEGF levels at start of treatment were obtained in 107 patients at four study sites. The median value was 70 pg/ml. Mean values declined during the first 12 weeks and then increased at 20 weeks. A subpopulation treatment effect pattern plot (STEPP) analysis showed an inverse relationship between initial plasma VEGF and the impact of celecoxib on survival with zero effect at 200 pg/ml. The effect on survival by celecoxib in the whole subset of patients was positive (hazard ratio (HR)=0.64 [confidence interval (CI) 0.43-0.95], p=0.028).

CONCLUSION

Low pretreatment plasma levels of VEGF appear to be predictive of a positive effect of celecoxib on survival.

Molecular pathways: targeting mechanisms of asbestos and erionite carcinogenesis in mesothelioma

Malignant mesothelioma is an aggressive malignancy related to asbestos and erionite exposure. AP-1 transcriptional activity and the NF-κB signaling pathway have been linked to mesothelial cell transformation and tumor progression. HGF and c-Met are highly expressed in mesotheliomas. Phosphoinositide 3-kinase, AKT, and the downstream mTOR are involved in cell growth and survival, and they are often found to be activated in mesothelioma. p16(INK4a) and p14(ARF) are frequently inactivated in human mesothelioma, and ∼50% of mesotheliomas contain the NF2 mutation. Molecular therapies aimed at interfering with these pathways have not improved the dismal prognosis of mesothelioma, except possibly for a small subset of patients who benefit from certain therapies. Recent studies have shown the importance of asbestos-induced inflammation in the initiation and growth of mesothelioma, and HMGB1 and Nalp3 inflammasome have been identified as key initiators of this process. Asbestos induces cell necrosis, causing the release of HMGB1, which in turn may activate Nalp3 inflammasome, a process that is enhanced by asbestos-induced production of reactive oxygen species. HMGB1 and Nalp3 induce proinflammatory responses and lead to interleukin-1β and TNF-α secretion and NF-κB activity, thereby promoting cell survival and tumor growth. Novel strategies that interfere with asbestos- and erionite-mediated inflammation might prevent or delay the onset of mesothelioma in high-risk cohorts, including genetically predisposed individuals, and/or inhibit tumor growth. The very recent discovery that germline BAP1 mutations cause a new cancer syndrome characterized by mesothelioma, uveal melanoma, and melanocytic tumors provides researchers with a novel target for prevention and early detection.

Apoptosis induced by piroxicam plus cisplatin combined treatment is triggered by p21 in mesothelioma

BACKGROUND

Malignant mesothelioma (MM) is a rare, highly aggressive tumor, associated to asbestos exposure. To date no chemotherapy regimen for MM has proven to be definitively curative, and new therapies for MM treatment need to be developed. We have previously shown in vivo that piroxicam/cisplatin combined treatment in MM, specifically acts on cell cycle regulation triggering apoptosis, with survival increase.

METHODOLOGY/PRINCIPAL FINDINGS

We analyzed, at molecular level, the apoptotic increase caused by piroxicam/cisplatin treatment in MM cell lines. By means of genome wide analyses, we analyzed transcriptional gene deregulation both after the single piroxicam or cisplatin and the combined treatment. Here we show that apoptotic increase following combined treatment is mediated by p21, since apoptotic increase in piroxicam/cisplatin combined treatment is abolished upon p21 silencing.

CONCLUSIONS/SIGNIFICANCE

Piroxicam/cisplatin combined treatment determines an apoptosis increase in MM cells, which is dependent on the p21 expression. The results provided suggest that piroxicam/cisplatin combination might be tested in clinical settings in tumor specimens that express p21.

Targeting apoptosis pathways by Celecoxib in cancer

Celecoxib is a paradigmatic selective inhibitor of cyclooxygenase-2 (COX-2). This anti-inflammatory drug has potent anti-tumor activity in a wide variety of human epithelial tumor types, such as colorectal, breast, non-small cell lung, and prostate cancers. Up to now, the drug found application in cancer prevention in patients with familial adenomatous polyposis. Moreover, the use of Celecoxib is currently tested in the prevention and treatment of pancreatic, breast, ovarian, non-small cell lung cancer and other advanced human epithelial cancers. Induction of apoptosis contributes to the anti-neoplastic activity of Celecoxib. In most cellular systems Celecoxib induces apoptosis independently from its COX-2 inhibitory action via a mitochondrial apoptosis pathway which is however, not inhibited by overexpression of Bcl-2. In addition, Celecoxib exerts antagonistic effects on the anti-apoptotic proteins Mcl-1 and survivin. Consequently, the use of Celecoxib may be of specific value for the treatment of apoptosis-resistant tumors with overexpression of Bcl-2, Mcl-1, or survivin as single drug or in combination with radiotherapy, chemotherapy, or targeted pro-apoptotic drugs that are inhibited by survivin, Bcl-2 or Mcl-1. As COX-2 inhibition has been associated with cardiovascular toxicity, the value of drug derivatives without COX-2 inhibitory action should be validated for prevention and treatment of human epithelial tumors to reduce the risk for heart attack or stroke. However, its additional COX-2 inhibitory action may qualify Celecoxib for a cautious use in COX-2-dependent epithelial tumors, where the drug could additionally suppress COX-2-mediated growth and survival promoting signals from the tumor and the stromal cells.

Synergistic effect of gefitinib and rofecoxib in mesothelioma cells

BACKGROUND

Malignant mesothelioma (MM) is an aggressive tumor that is resistant to conventional modes of treatment with chemotherapy, surgery or radiation. Research into the molecular pathways involved in the development of MM should yield information that will guide therapeutic decisions. Epidermal growth factor receptor (EGFR) and cyclooxygenase-2 (COX-2) are involved in the carcinogenesis of MM. Combination of COX-2 and EGFR inhibitors, therefore, could be an effective strategy for reducing cell growth in those lines expressing the two molecular markers.

RESULTS

In order to verify the effect of COX-2 and EGFR inhibitors, five MM cell lines NCI-2452, MPP89, Ist-Mes-1, Ist-Mes-2 and MSTO-211 were characterized for COX-2 and EGFR and then treated with respective inhibitors (rofecoxib and gefitinib) alone and in combination. Only MPP89, Ist-Mes-1 and Ist-Mes-2 were sensitive to rofecoxib and showed growth-inhibition upon gefitinib treatment. The combination of two drugs demonstrated synergistic effects on cell killing only in Ist-Mes-2, the cell line that was more sensitive to gefitinib and rofecoxib alone. Down-regulation of COX-2, EGFR, p-EGFR and up-regulation of p21 and p27 were found in Ist-Mes-2, after treatment with single agents and in combination. In contrast, association of two drugs resulted in antagonistic effect in Ist-Mes-1 and MPP89. In these cell lines after rofecoxib exposition, only an evident reduction of p-AKT was observed. No change in p-AKT in Ist-Mes-1 and MPP89 was observed after treatment with gefitinib alone and in combination with rofecoxib.

CONCLUSIONS

Gefitinib and rofecoxib exert cell type-specific effects that vary between different MM cells. Total EGFR expression and downstream signalling does not correlate with gefitinib sensitivity. These data suggest that the effect of gefitinib can be potentiated by rofecoxib in MM cell lines where AKT is not activated.

PC-407, a celecoxib derivative, inhibited the growth of colorectal tumor in vitro and in vivo

This study aimed to observe the growth-inhibitory effect of PC-407 (4-[5-naphthyl-3-(trifluoromethyl)-1H-pyrazol-1-yl] benzenesulfonamide), a celecoxib derivative synthesized in our lab, in human colorectal cancer cells and a colitis-associated colorectal cancer (CACC) model, and investigate the relative molecular mechanisms. SW-1116 (expressing a high level of cyclooxygenase-2 [COX-2]), HT-29 (expressing a moderate level of COX-2), and SW-480 (no expression of COX-2) cell lines were exposed to different concentrations of celecoxib (0-100 micromol/L) or PC-407 (0-100 micromol/L). Then, COX-2 levels were assessed by reverse transcription-PCR and Western blotting. COX-2 activity was evaluated by measuring prostaglandin E(2) concentration using enzyme-linked immunoassay. A mouse model of colitis-associated carcinogenesis was employed to determine the effect of PC-407 in vivo. PC-407 inhibited cell growth in a concentration-dependent manner, and the IC(50) values of PC-407 for growth inhibition of SW-1116, HT-29, and SW-480 cells were 17.60 +/- 3.02, 18.14 +/- 2.81, and 8.13 +/- 0.40 micromol/L, respectively. PC-407 down-regulated COX-2 mRNA and protein levels and reduced prostaglandin E(2) production significantly. In vivo, PC-407 inhibited the genesis of CACC effectively. Our data indicate that PC-407 can inhibit the growth of tumor both in vitro and in vivo and suggest that the effect probably involves inhibition of the COX-2 pathway and other COX-2-independent pathways.

Apoptosis induction in human lung adenocarcinoma cells by oil-soluble allyl sulfides: triggers, pathways, and modulators

DAS (diallyl sulfide), DADS (diallyl disulfide), and DATS (diallyl trisulfide) are major oil-soluble allyl sulfides (OAS) that represent major garlic constituents. The anticarcinogenic and antimutagenic effects of these substances have been extensively studied during the last decades. Previous reports suggest that induction of apoptosis by OASs might contribute to their chemopreventive effects. In this study, we report that OASs DADS and DATS induce significant apoptosis in human lung adenocarcinoma A549 cells, whereas DAS does not. Differential modulation of reactive oxygen intermediates (ROI) and mitochondria membrane potential (MMP) may account for the apoptotic effects of DADS and DATS. The underlying molecular mechanisms of apoptosis induction by both compounds include activation of C-Jun N-terminal kinase (JNK), up-regulation of p53, and down-regulation of bcl-2 expression. In our test series, up-regulation of extracellular signal-regulated protein kinase (ERK) was dispensable for apoptosis induction; DAS, DADS, or DATS did not modify expression of MAPK p38, bax, and bcl-xL. Further investigation revealed that the specific JNK inhibitor SP600125 and the antioxidant NAC blocked DADS and DATS-induced apoptosis, whereas ERK inhibitors did not. Additionally, our data provide the first evidence that Fas-mediated cell death pathway is partly involved in DADS but not DATS-mediated cell death. Taken together, our work has elucidated the triggers, important modulators, and signal transduction pathways in DADS and DATS-mediated apoptosis.

Enhanced antitumor therapy by inhibition of p21waf1 in human malignant mesothelioma

PURPOSE

The p21 cyclin-dependent kinase inhibitor was frequently expressed in human malignant pleural mesothelioma (MPM) tissues as well as cell lines. Recent data indicate that p21 keeps tumor cells alive after DNA damage, favoring a survival advantage. In this study, we assessed the possibility of p21 suppression as a therapeutic target for MPM.

EXPERIMENTAL DESIGN

We established two different MPM-derived (from H28 and H2052 cells) subclones using vector-based short hairpin RNA (shRNA). Then, chemosensitivity against low doses of antineoplastic DNA-damaging agents was investigated by colony formation assays, and furthermore, the type of cell response induced by these drugs was analyzed. To examine the effect of p21 shRNA on chemosensitivity in vivo, tumor formation assays in nude mice were done.

RESULTS

In colony formation assay, the IC50 of doxorubicin was 33 +/- 3.0 nmol/L in p21 shRNA-transfected cells with respect to 125 +/- 10 nmol/L of control vector-transfected cells. This enhancement of growth inhibition was achieved by converting a senescence-like growth arrest to apoptosis in response to doxorubicin, etoposide, and CPT11. In the in vivo assays, CPT11 and loss-of-expression of p21 in combination led to considerable suppression of tumor growth associated with a substantially enhanced apoptotic response, whereas CPT11 alone was ineffective at inducing these responses.

CONCLUSIONS

These results indicated that p21 might play an important role in chemosensitivity to anticancer agents, and the suppression of its expression might be a potential therapeutic target for MPM.

Delayed antiviral plus immunomodulator treatment still reduces mortality in mice infected by high inoculum of influenza A/H5N1 virus

The mortality of human infection by influenza A/H5N1 virus can exceed 80%. The high mortality and its poor response to the neuraminidase inhibitor oseltamivir have been attributed to uncontrolled virus-induced cytokine storm. We challenged BALB/c mice with 1,000 LD50 of influenza A/Vietnam/1194/04. Survival, body weight, histopathology, inflammatory markers, viral loads, T lymphocyte counts, and neutralizing antibody response were documented in infected mice treated individually or in combination with zanamvir, celecoxib, gemfibrozil, and mesalazine. To imitate the real-life scenario, treatment was initiated at 48 h after viral challenge. There were significant improvements in survival rate (P = 0.02), survival time (P < 0.02), and inflammatory markers (P < 0.01) in the group treated with a triple combination of zanamivir, celecoxib, and mesalazine when compared with zanamivir alone. Zanamivir with or without immunomodulators reduced viral load to a similar extent. Insignificant prolongation of survival was observed when individual agents were used alone. Significantly higher levels of CD4+ and CD8+ T lymphocytes and less pulmonary inflammation were also found in the group receiving triple therapy. Zanamivir alone reduced viral load but not inflammation and mortality. The survival benefits of adding celecoxib and mesalazine to zanamivir could be caused by their synergistic effects in reducing cytokine dysfunction and preventing apoptosis. Combinations of a neuraminidase inhibitor with these immunomodulators should be considered in randomized controlled treatment trials of patients suffering from H5N1 infection.

Molecular analysis of the effects of Piroxicam and Cisplatin on mesothelioma cells growth and viability

Nonsteroidal anti-inflammatory drugs (NSAIDs) have been proposed for prevention and treatment of a variety of human cancers. Piroxicam, in particular, has been recently shown to exert significant anti-tumoral activity in combination with cisplatin (CDDP) on mesothelioma cells. However, the mechanisms through which NSAIDs regulate the cell cycle as well as the signal pathways involved in the growth inhibition, remain unclear. In the present study, using two mesothelioma cell lines, MSTO-211H and NCI-H2452, we have investigated the influence of piroxicam alone and in association with CDDP on proliferation, cell cycle regulation and apoptosis. In both cell lines a significant effect on cell growth inhibition, respect to the control, was observed with all the drugs tested. Moreover, treatment with piroxicam or CDDP alone altered the cell cycle phase distribution as well as the expression of some cell cycle regulatory proteins in both cell lines. These effects were increased, even if in a not completely overlapping manner, after treatment with the association of piroxicam and CDDP. In particular, the two drugs in NCI cell line had a synergistic effect on apoptosis, probably through activation of caspase 8 and caspase 9, while the most evident targets among the cell cycle regulators were cyclin D1 and p21waf1. These results suggest that the association of piroxicam and CDDP specifically triggers cell cycle regulation and apoptosis in different mesothelioma cell lines and may hold promise in the treatment of mesothelioma.

Adenovirus type 5 E1A-induced apoptosis in COX-2-overexpressing breast cancer cells

INTRODUCTION

Suppression of Bcl-2 expression can overcome cellular resistance to apoptosis induced by the adenovirus type 5 gene E1A in models of ovarian and breast cancer. Celecoxib, a cyclooxygenase-2 (COX-2) inhibitor, is known to downregulate Bcl-2 expression. We hypothesized that celecoxib would enhance E1A-induced apoptosis by suppressing Bcl-2 through suppressing COX-2 expression. If successful, this strategy could represent a means of overcoming resistance to E1A gene therapy.

METHODS

We first established the cytotoxicity of celecoxib in two COX-2-overexpressing E1A-transfected breast cancer cell lines (MDA-MB-231 and MDA-MB-435) and in two low-COX-2-expressing E1A-transfected cell lines (MCF-7 (breast cancer) and SKOV3.ip1 (ovarian cancer)). We next tested whether higher sensitivity to celecoxib among these cell lines resulted from increased apoptosis by flow cytometry and western blotting. We further investigated whether suppression of Bcl-2 by celecoxib was involved in the apoptosis resulting from celecoxib treatment, and we explored whether the celecoxib-induced apoptosis in these cells depends on a COX-2 downstream pathway.

RESULTS

The two COX-2-overexpressing cell lines MDA-MB-231-E1A and MDA-MB-435-E1A were more sensitive to celecoxib than the corresponding control cells, but the two low-COX-2-expressing cell lines MCF-7-E1A and SKOV3.ip1-E1A were no more sensitive than control cells to celecoxib. Therefore, we used the MDA-MB-231-E1A and MDA-MB-435-E1A cells for all further experiments. In both cell lines, sub-G1 fraction was increased, or cleavage of PARP and caspase-9 were increased after 5 days of exposure to 40 microM celecoxib. However, Bcl-2 was suppressed only in the MDA-MB-435-E1A cells and not in the MDA-MB-231-E1A cells. Restoring Bcl-2 expression in the MDA-MB-435-E1A stable transfectants did not affect their sensitivity to celecoxib. However, adding prostaglandin E2 (PGE2) or PGF2alpha blunted the sensitivity to celecoxib of both E1A stable transfectants.

CONCLUSION

We speculate that one mechanism by which celecoxib enhances E1A-induced apoptosis in cells that express high levels of COX-2 is through blocking PGE2 or PGF2alpha.

Cyclooxygenase-2 (COX-2)-independent anticarcinogenic effects of selective COX-2 inhibitors

Nonsteroidal antiinflammatory drugs (NSAIDs) appear to reduce the risk of developing cancer. One mechanism through which NSAIDs act to reduce carcinogenesis is to inhibit the activity of cyclooxygenase-2 (COX-2), an enzyme that is overexpressed in various cancer tissues. Overexpression of COX-2 increases cell proliferation and inhibits apoptosis. However, selective COX-2 inhibitors can also act through COX-independent mechanisms. In this review, we describe the COX-2-independent molecular targets of these COX-2 inhibitors and discuss how these targets may be involved in the anticarcinogenic activities of these selective COX-2 inhibitors. We also compare the concentrations of these inhibitors used in in vitro and in vivo experiments and discuss the implications of the in vitro studies for clinical management of cancer with these drugs.

Downregulation of survivin expression and concomitant induction of apoptosis by celecoxib and its non-cyclooxygenase-2-inhibitory analog, dimethyl-celecoxib (DMC), in tumor cells in vitro and in vivo

Background

2,5-Dimethyl-celecoxib (DMC) is a close structural analog of the selective cyclooxygenase-2 (COX-2) inhibitor celecoxib (Celebrex^®) that lacks COX-2-inhibitory function. However, despite its inability to block COX-2 activity, DMC is able to potently mimic the anti-tumor effects of celecoxib in vitro and in vivo, indicating that both of these drugs are able to involve targets other than COX-2 to exert their recognized cytotoxic effects. However, the molecular components that are involved in mediating these drugs' apoptosis-stimulatory consequences are incompletely understood.

Results

We present evidence that celecoxib and DMC are able to down-regulate the expression of survivin, an anti-apoptotic protein that is highly expressed in tumor cells and known to confer resistance of such cells to anti-cancer treatments. Suppression of survivin is specific to these two drugs, as other coxibs (valdecoxib, rofecoxib) or traditional NSAIDs (flurbiprofen, indomethacin, sulindac) do not affect survivin expression at similar concentrations. The extent of survivin down-regulation by celecoxib and DMC in different tumor cell lines is somewhat variable, but closely correlates with the degree of drug-induced growth inhibition and apoptosis. When combined with irinotecan, a widely used anticancer drug, celecoxib and DMC greatly enhance the cytotoxic effects of this drug, in keeping with a model that suppression of survivin may be beneficial to sensitize cancer cells to chemotherapy. Remarkably, these effects are not restricted to in vitro conditions, but also take place in tumors from drug-treated animals, where both drugs similarly repress survivin, induce apoptosis, and inhibit tumor growth in vivo.

Conclusion

In consideration of survivin's recognized role as a custodian of tumor cell survival, our results suggest that celecoxib and DMC might exert their cytotoxic anti-tumor effects at least in part via the down-regulation of survivin – in a manner that does not require the inhibition of cyclooxygenase-2. Because inhibition of COX-2 appears to be negligible, it might be worthwhile to further evaluate DMC's potential as a non-coxib alternative to celecoxib for anti-cancer purposes.

Antitumor properties of dimethyl-celecoxib, a derivative of celecoxib that does not inhibit cyclooxygenase-2: implications for glioma therapy

✓ Celecoxib (Celebrex) appears to be unique among the class of selective COX-2 inhibitors (coxibs), because this particular compound exerts a second function that is independent of its celebrated ability to inhibit COX-2. This second function is the potential to inhibit cell proliferation and stimulate apoptotic cell death at much lower concentrations than any other coxibs. Intriguingly, these two functions are mediated by different moieties of the celecoxib molecule and can be separated. The author, as well as others, have generated and investigated analogs of celecoxib that retain only one of these two functions. One derivative, 2,5-dimethyl-celecoxib (DMC), which retains the antiproliferative and apoptosis-inducing function, but completely lacks the COX-2 inhibitory activity, is able to mimic faithfully all of the numerous antitumor effects of celecoxib that have been investigated so far, including reduction of neovascularization and inhibition of experimental tumor growth in various in vivo tumor models. In view of the controversy that has recently arisen regarding the life-threatening side effects of this class of coxibs, it may be worthwhile to pursue further the potential benefits of drugs such as DMC for anticancer therapy. Because DMC is not a coxib yet potently maintains celecoxib's antitumor potential, one may be inclined to speculate that this novel compound could potentially be advantageous in the management of COX-2–independent cancers. In this summary, the implications of recent findings with DMC will be presented and discussed.

Antiangiogenic therapies for mesothelioma

A large body of preclinical evidence suggests that angiogenesis plays a key role in the pathogenesis of malignant mesothelioma. Several mediators of angiogenesis seem to be autocrine growth factors in mesothelioma, and in preclinical models, agents that target angiogenesis produce tumor regression. Several clinical trials are currently evaluating the efficacy of inhibitors of angiogenesis in mesothelioma. This article details the preliminary results of these trials and future directions.

Cyclooxygenase-2 expression predicts survival in malignant pleural mesothelioma

The expression of cyclooxygenase 2 (COX-2) protein is increased in many tumours and may be associated with a more aggressive phenotype. We aimed to assess COX-2 expression in a large series of archival mesothelioma specimens. Archival tissue was obtained from 86 malignant pleural mesothelioma samples (histological subtype: 42 epithelial, 28 biphasic and 16 sarcomatoid). Overexpression of COX-2 was detected by immunohistochemical analysis. Positive staining was located in the cytoplasm of malignant tumour cells. Overall 51/86 (59%) tumour sections demonstrated COX-2 overexpression. The frequency varied with histological subtype with 31/42 (73%) of epithelial sections, 14/28 (50%) of biphasic sections and 6/16 (37%) of sarcomatoid sections recorded as positive. Kaplan Meier survival analysis indicated that overexpression of COX-2 was significantly related to improved prognosis (P < 0.001) and was an independent prognostic factor in multivariant analysis. Overexpression of COX-2 protein may confer a survival advantage in mesothelioma patients.

Molecular prognostic markers in malignant mesothelioma

Malignant mesothelioma remains a highly lethal cancer. Recent advances in both surgical and medical therapy have improved survival, but the treatments remain toxic and selection of appropriate patients for these therapies is difficult. Research into the molecular pathways involved in the development of mesothelioma should yield information that will guide therapeutic decisions in the near future. In particular, expression of EGFR and VEGF receptor hold promise to alter standards of patient care in the next few years. Alterations in cell cycle control proteins such as p16, p21, and p27 also offer information on prognosis and represent potential targets for therapy.

Induction of stem cell factor/c-Kit/slug signal transduction in multidrug-resistant malignant mesothelioma cells

Malignant mesothelioma (MM) is strongly resistant to conventional chemotherapy by unclear mechanisms. We and others have previously reported that cytokine- and growth factor-mediated signal transduction is involved in the growth and progression of MM. Here, we identified a pathway that involves stem cell factor (SCF)/c-Kit/Slug in mediating multidrug resistance of MM cells. When we compared gene expression profiles between five MM cells and their multidrug-resistant (MM DX) sublines, we found that MM DX cells expressed both SCF and c-Kit and had higher mRNA levels of Slug. Knockdown of c-Kit or Slug expression with their respective small interfering RNA sensitized MM DX cells to the induction of apoptosis by different chemotherapeutic agents, including doxorubicin, paclitaxel, and vincristine. Transfection of c-Kit in parental MM cells in the presence of SCF up-regulated Slug and increased resistance to the chemotherapeutic agents. Moreover, MM cells expressing Slug showed a similar increased resistance to the chemotherapeutic agents. These results indicate that induction of Slug by autocrine production of SCF and c-Kit activation plays a key role in conferring a broad spectrum chemoresistance on MM cells and reveal a novel signal transduction pathway for pharmacological or genetic intervention of MM patients.