Cyclooxygenase-2 interacts with p53 and interferes with p53-dependent transcription and apoptosis

Self-assembly nanoplatform of platinum (Ⅳ) prodrug for enhanced ovarian cancer therapy

Cisplatin is a metal platinum complex commonly used in the field of anti-tumor and one of the most commonly used drugs in combination chemotherapy. However, chemotherapy with Cisplatin induced overexpression of cyclooxygenase-2 (COX-2) protein in tumor cells, which could impair the therapeutic effect of chemotherapy on tumor progression. Here, we presented a novel method for the treatment of ovarian cancer with a self-assembly based nano-system. Cisplatin and tolfenamic acid were each linked to linoleic acid to give them the ability to self-assemble into nanoparticles in water. TPNPs had flexible drug ratio adjustability, homogeneous stability, and high drug loading capacity. Compared with Cisplatin, TPNPs could promote cellular uptake and tumor aggregation, co-induce enhanced apoptosis and tumor growth inhibition by inhibiting COX-2 in the mice xenograft model of human ovarian cancer, and reduce systemic toxicity. Therefore, TPNPs is a promising antitumor drug as a kind of self-assembly nano-prodrug with high drug load.

Cervical cancer benefits from trabectedin combination with the β-blocker propranolol: in vitro and ex vivo evaluations in patient-derived organoids

Background: Cervical cancer (CC) is characterized by genomic alterations in DNA repair genes, which could favor treatment with agents causing DNA double-strand breaks (DSBs), such as trabectedin. Hence, we evaluated the capability of trabectedin to inhibit CC viability and used ovarian cancer (OC) models as a reference. Since chronic stress may promote gynecological cancer and may hinder the efficacy of therapy, we investigated the potential of targeting β-adrenergic receptors with propranolol to enhance trabectedin efficacy and change tumor immunogenicity. Methods: OC cell lines, Caov-3 and SK-OV-3, CC cell lines, HeLa and OV2008, and patient-derived organoids were used as study models. MTT and 3D cell viability assays were used for drug(s) IC₅₀ determination. The analysis of apoptosis, JC-1 mitochondrial membrane depolarization, cell cycle, and protein expression was performed by flow cytometry. Cell target modulation analyses were carried out by gene expression, Western blotting, immunofluorescence, and immunocytochemistry. Results: Trabectedin reduced the proliferation of both CC and OC cell lines and notably of CC patient-derived organoids. Mechanistically, trabectedin caused DNA DSBs and S-phase cell cycle arrest. Despite DNA DSBs, cells failed the formation of nuclear RAD51 foci and underwent apoptosis. Under norepinephrine stimulation, propranolol enhanced trabectedin efficacy, further inducing apoptosis through the involvement of mitochondria, Erk1/2 activation, and the increase of inducible COX-2. Notably, trabectedin and propranolol affected the expression of PD1 in both CC and OC cell lines. Conclusion: Overall, our results show that CC is responsive to trabectedin and provide translational evidence that could benefit CC treatment options. Our study pointed out that combined treatment offset trabectedin resistance caused by β-adrenergic receptor activation in both ovarian and cervical cancer models.

Hallmarks of Cancer Affected by the MIF Cytokine Family

New diagnostic methods and treatments have significantly decreased the mortality rates of cancer patients, but further improvements are warranted based on the identification of novel tumor-promoting molecules that can serve as therapeutic targets. The macrophage migration inhibitory factor (MIF) family of cytokines, comprising MIF and DDT (also known as MIF2), are overexpressed in almost all cancer types, and their high expressions are related to a worse prognosis for the patients. MIF is involved in 9 of the 10 hallmarks of cancer, and its inhibition by antibodies, nanobodies, or small synthetic molecules has shown promising results. Even though DDT is also proposed to be involved in several of the hallmarks of cancer, the available information about its pro-tumoral role and mechanism of action is more limited. Here, we provide an overview of the involvement of both MIF and DDT in cancer, and we propose that blocking both cytokines is needed to obtain the maximum anti-tumor response.

Cyclooxygenase-2 induces neoplastic transformation by inhibiting p53-dependent oncogene-induced senescence

Much in vivo evidence indicates that cyclooxygenase-2 (COX-2) is deeply involved in tumorigenesis. Although it has been proposed that COX-2-derived pro-inflammatory prostanoids mediate the tumorigenic activity of COX-2, the tumorigenic mechanisms of COX-2 are not yet fully understood. Here, we investigated the mechanism by which COX-2 causes transformation from normal cells to malignant cells by using normal murine or human cells. We found that COX-2 inhibits the pro-senescent function of p53 under oncogenic RAS activation, by which it prevents oncogene-induced senescence (OIS) and induces neoplastic transformation. We also found that COX-2 physically interacts with p53 in the nucleus under oncogenic RAS activation, and that this COX-2-p53 interaction rather than the catalytic activity is involved in the COX-2-mediated inhibition of the pro-senescent function of p53 and OIS, and induction of neoplastic transformation. These findings strongly suggest that the oncogenic property of COX-2 is closely related to its ability to inactivate p53 under strong mitogenic signals, and that aberrant activation of the COX-2/a mitogenic oncogene combination can be a potent driving force for tumorigenesis. This study might contribute to our understanding of the molecular basis for the tumorigenic activity of COX-2 and the development of novel anti-tumor drugs targeting COX-2-p53 interactions.

Cytoguardin: A Tryptophan Metabolite against Cancer Growth and Metastasis

Cytoguardin was identified in the conditioned medium of fibroblasts as a tryptophan metabolite, 5-methoxytryptophan (5-MTP). It is synthesized via two enzymatic steps: tryptophan hydroxylase (TPH) and hydroxyindole O-methyltransferase (HIOMT). A truncated HIOMT isoform, HIOMT298, catalyzes 5-MTP synthesis. Cancer cells produce scarce 5-MTP due to defective HIOMT298 expression. 5-MTP inhibits cancer cell COX-2 expression and thereby reduces COX-2-mediated cell proliferation and migration. 5-MTP also inhibits MMP-9 expression and thereby reduces cancer cell invasion. 5-MTP exerts its anti-cancer effect by blocking p38 MAPK and p38-mediated NF-κB and p300 HAT activation. The stable transfection of A549 cells with HIOMT298 restores 5-MTP production which renders cancer cells less aggressive. The implantation of HIOMT-transfected A549 into subcutaneous tissues of a murine xenograft tumor model shows that HIOMT-transduced A549 cells form smaller tumors and generate fewer metastatic lung nodules than control A549 cells. HIOMT298 transfection suppresses aromatic amino acid decarboxylase (AADC) expression and serotonin production. Serotonin is a cancer-promoting factor. By restoring 5-MTP and suppressing serotonin production, HIOMT298 overexpression converts cancer cells into less malignant phenotypes. The analysis of HIOMT expression in a human cancer tissue array showed reduced HIOMT levels in a majority of colorectal, pancreatic, and breast cancer. HIOMT298 may be a biomarker of human cancer progression. Furthermore, 5-MTP has the potential to be a lead compound in the development of new therapy for the chemoprevention of certain cancers such as hepatocellular cancer.

Ketoplatin in triple-negative breast cancer cells MDA-MB-231: High efficacy and low toxicity, and positive impact on inflammatory microenvironment

Triple-negative breast cancer (TNBC) shares the molecular features facilitating epithelial-to-mesenchymal transition (EMT), which contributed to tumor invasion and metastasis. A platinum(IV) conjugate ketoplatin deriving from FDA-approved drugs cisplatin and ketoprofen was designed and prepared to enhance antitumor activity and suppress EMT in TNBC via positive impact on inflammatory microenvironment by modulating COX-2 signal. As a prodrug, ketoplatin afforded 50.26-fold higher cytotoxicity than cisplatin against TNBC mesenchymal-stem cell-like MDA-MB-231 cells, partly attributing to its dramatic increase of cellular uptake and DNA damage. More importantly, EMT progress in MDA-MB-231 was markedly restrained by ketoplatin, resulting from the suppression of vimentin and N-cadherin mediated by down-regulated COX-2. Further in vivo investigation exhibited that ketoplatin effectively inhibited tumor growth and reduced systemic toxicity compared to cisplatin. Overall, ketoplatin possessed high antitumor activity and low toxicity against TNBC MDA-MB-231 in vitro and in vivo.

P53: A Guardian of Immunity Becomes Its Saboteur through Mutation

Awareness of the importance of immunity in controlling cancer development triggered research into the impact of its key oncogenic drivers on the immune response, as well as their value as targets for immunotherapy. At the heart of tumour suppression is p53, which was discovered in the context of viral infection and now emerges as a significant player in normal and cancer immunity. Wild-type p53 (wt p53) plays fundamental roles in cancer immunity and inflammation. Mutations in p53 not only cripple wt p53 immune functions but also sinisterly subvert the immune function through its neomorphic gain-of-functions (GOFs). The prevalence of mutant p53 across different types of human cancers, which are associated with inflammatory and immune dysfunction, further implicates mutant p53 in modulating cancer immunity, thereby promoting tumorigenesis, metastasis and invasion. In this review, we discuss several mutant p53 immune GOFs in the context of the established roles of wt p53 in regulating and responding to tumour-associated inflammation, and regulating innate and adaptive immunity. We discuss the capacity of mutant p53 to alter the tumour milieu to support immune dysfunction, modulate toll-like receptor (TLR) signalling pathways to disrupt innate immunity and subvert cell-mediated immunity in favour of immune privilege and survival. Furthermore, we expose the potential and challenges associated with mutant p53 as a cancer immunotherapy target and underscore existing therapies that may benefit from inquiry into cancer p53 status.

The COX-2 inhibitor NS398 selectively sensitizes hypoxic HeLa cells to ionising radiation by mechanisms both dependent and independent of COX-2

It is widely accepted that the hypoxic nature of solid tumors contribute to their resistance to radiation therapy. There is increasing evidence that cyclooxygenase-2 (COX-2) contributes to increased resistance of tumors to radiation therapy. Several studies demonstrate that combination of COX-2 selective inhibitors with radiation therapy selectively enhances radio responsiveness of tumor cells. However, the majority of these studies utilised suprapharmacological concentrations under normoxic conditions only. Furthermore, the mechanism by which these agents act remain largely unclear. Therefore, the aim of this study was to determine the impact of COX-2 selective inhibitors on both normoxic and hypoxic radiosensitivity in vitro and the mechanisms underlying this. Because of the close, reciprocal relationship between COX-2 and p53 we investigated their contribution to radioresistance. To achieve this we exposed HeLa, MCF-7 and MeWo cells to the COX-2 selective inhibitor, NS398 (10μM). NS398 (10μM) selectively sensitized hypoxic HeLa and MCF-7 but not MeWo cells to ionising radiation (5 Gy). Furthermore, while knockdown of COX-2 with siRNA did not affect either normoxic radiosensitivity in HeLa cells, the radiosensitisation observed with NS398 was lost suggesting both COX-2 dependent and independent mechanisms. We also show that ionising radiation at 5 Gy results in phosphorylation of p53 at serine 15, a key phosphorylation site for p53-mediated apoptosis, and that hypoxia attenuates this phosphorylation. Attenuated phosphorylation of p53 under hypoxic conditions may therefore contribute to hypoxic radioresistance. We also show that NS398 selectively phosphorylates p53 under hypoxic conditions following irradiation at 5 Gy. p53 phosphorylation could be an underlying mechanism by which this agent and other COX-2 inhibitors sensitize tumors to radiation therapy.

HDAC inhibitors show differential epigenetic regulation and cell survival strategies on p53 mutant colon cancer cells

Besides inactivating tumour suppressor activity in cells, mutations in p53 confer significant oncogenic functions and promote metastasis and resistance to anticancer therapy. A variety of therapies involving genetic and epigenetic signalling events regulate tumorogenesis and progression in such cases. Pharmacological interventions with HDAC inhibitors have shown promise in therapy. This work explores the changes in efficacy of the four HDAC inhibitors SAHA, MS-275, valproic acid and sodium butyrate on a panel of colon cancer cell lines - HCT116 (p53 wt), HCT116 p53-/-, HT29 and SW480 (with mutations in p53). Clonogenic assays, gene profiling and epigenetic expression done on these cells point to p53 dependent differential activity of the 4 HDAC inhibitors which also elevate methylation levels in p53 mutant cell lines. In silico modelling establishes the alterations in interactions that lead to such differential activity of valproic acid, one of the inhibitors considered for the work. Molecular Dynamic simulations carried out on the valproic acid complex ensure stability of the complex. This work establishes a p53 dependent epigenetic signalling mechanism triggered by HDAC inhibition expanding the scope of HDAC inhibitors in adjuvant therapy for p53 mutant tumours.

Downregulation of mitochondrial cyclooxygenase-2 inhibits the stemness of nasopharyngeal carcinoma by decreasing the activity of dynamin-related protein 1

Cancer stem cells (CSCs) are a small subset of malignant cells, possessing stemness, with strong tumorigenic capability, conferring resistance to therapy and leading to the relapse of nasopharyngeal carcinoma (NPC). Our previous study suggested that cyclooxygenase-2 (COX-2) would be a novel target for the CSCs-like side population (SP) cells in NPC. In the present study, we further found that COX-2 maintained the stemness of NPC by enhancing the activity of mitochondrial dynamin-related protein 1 (Drp1), a mitochondrial fission mediator, by studying both sorted SP cells from NPC cell lines and gene expression analyses in NPC tissues. Using both overexpression and knockdown of COX-2, we demonstrated that the localization of COX-2 at mitochondria promotes the stemness of NPC by recruiting the mitochondrial translocation of p53, increasing the activity of Drp1 and inducing mitochondrial fisson. Inhibition of the expression or the activity of Drp1 by siRNA or Mdivi-1 downregulates the stemness of NPC. The present study also found that inhibition of mitochondrial COX-2 with resveratrol (RSV), a natural phytochemical, increased the sensitivity of NPC to 5-fluorouracil (5-FU), a classical chemotherapy drug for NPC. The underlying mechanism is that RSV suppresses mitochondrial COX-2, thereby reducing NPC stemness by inhibiting Drp1 activity as demonstrated in both the in vitro and the in vivo studies. Taken together, the results of this study suggest that mitochondrial COX-2 is a potential theranostic target for the CSCs in NPC. Inhibition of mitochondrial COX-2 could be an attractive therapeutic option for the effective clinical treatment of therapy-resistant NPC.

COX-2 inhibitor NS-398 suppresses doxorubicin-induced p53 accumulation through inhibition of ROS-mediated Jnk activation

Cyclooxygenase-2 (COX-2) is one of the isoforms of cyclooxygenase, a rate-limiting enzyme in the arachidonic acid cascade. COX-2 protein expression is highly induced by numerous factors and it has been reportedly overexpressed in various human malignancies. Although anti-tumorigenic effects of COX-2 inhibitors have been shown, several lines of evidence suggest that COX-2 inhibitors antagonize the cytotoxicity of chemotherapeutic agents. In this study, we investigated the effect of NS-398, a COX-2 inhibitor, on modulation of doxorubicin (DOX)-induced p53 accumulation. Non-selective and selective COX-2 inhibitors attenuated DOX-induced accumulation of wild type (WT) but not mutant p53. Nutlin-3α or MG132 abolished the suppressive effect of a COX-2 inhibitor on DOX-induced p53 increase. Moreover, the DOX-induced increase in p53 protein levels was reduced in COX-2 knockout (KO) mouse embryonic fibroblasts (MEFs) compared to those in WT or COX-1 KO MEFs. DOX-induced accumulation of p53 was attenuated by a specific inhibitor or knockdown of Jun-N-terminal kinase (Jnk). In addition, DOX-induced Jnk activation was decreased in COX-2 KO MEFs or by COX-2 inhibition, suggesting that Jnk stabilizes p53 by a mechanism that involves COX-2. Pre-treatment with a reactive oxygen species (ROS) scavenger, N-acetylcysteine, attenuated DOX-induced Jnk activation and subsequent p53 accumulation. Furthermore, the absence or inhibition of COX-2 resulted in suppression of DOX-induced increase in ROS levels. These results suggest that COX-2 activates Jnk through modulation of ROS levels, leading to accumulation of p53. Our study identifies a putative novel cross-talk between COX-2 and p53. © 2016 Wiley Periodicals, Inc.

The impact of low-dose carcinogens and environmental disruptors on tissue invasion and metastasis

The purpose of this review is to stimulate new ideas regarding low-dose environmental mixtures and carcinogens and their potential to promote invasion and metastasis. Whereas a number of chapters in this review are devoted to the role of low-dose environmental mixtures and carcinogens in the promotion of invasion and metastasis in specific tumors such as breast and prostate, the overarching theme is the role of low-dose carcinogens in the progression of cancer stem cells. It is becoming clearer that cancer stem cells in a tumor are the ones that assume invasive properties and colonize distant organs. Therefore, low-dose contaminants that trigger epithelial-mesenchymal transition, for example, in these cells are of particular interest in this review. This we hope will lead to the collaboration between scientists who have dedicated their professional life to the study of carcinogens and those whose interests are exclusively in the arena of tissue invasion and metastasis.

Environmental immune disruptors, inflammation and cancer risk

An emerging area in environmental toxicology is the role that chemicals and chemical mixtures have on the cells of the human immune system. This is an important area of research that has been most widely pursued in relation to autoimmune diseases and allergy/asthma as opposed to cancer causation. This is despite the well-recognized role that innate and adaptive immunity play as essential factors in tumorigenesis. Here, we review the role that the innate immune cells of inflammatory responses play in tumorigenesis. Focus is placed on the molecules and pathways that have been mechanistically linked with tumor-associated inflammation. Within the context of chemically induced disturbances in immune function as co-factors in carcinogenesis, the evidence linking environmental toxicant exposures with perturbation in the balance between pro- and anti-inflammatory responses is reviewed. Reported effects of bisphenol A, atrazine, phthalates and other common toxicants on molecular and cellular targets involved in tumor-associated inflammation (e.g. cyclooxygenase/prostaglandin E2, nuclear factor kappa B, nitric oxide synthesis, cytokines and chemokines) are presented as example chemically mediated target molecule perturbations relevant to cancer. Commentary on areas of additional research including the need for innovation and integration of systems biology approaches to the study of environmental exposures and cancer causation are presented.

Mechanisms of ceramide-induced COX-2-dependent apoptosis in human ovarian cancer OVCAR-3 cells partially overlapped with resveratrol

Ceramide is a member of the sphingolipid family of bioactive molecules demonstrated to have profound, diverse biological activities. Ceramide is a potential chemotherapeutic agent via the induction of apoptosis. Exposure to ceramide activates extracellular-signal-regulated kinases (ERK)1/2- and p38 kinase-dependent apoptosis in human ovarian cancer OVCAR-3 cells, concomitant with an increase in the expression of COX-2 and p53 phosphorylation. Blockade of cyclooxygenase-2 (COX-2) activity by siRNA or NS398 correspondingly inhibited ceramide-induced p53 Ser-15 phosphorylation and apoptosis; thus COX-2 appears at the apex of the p38 kinase-mediated signaling cascade induced by ceramide. Induction of apoptosis by ceramide or resveratrol was inhibited by the endocytosis inhibitor, cytochalasin D (CytD); however, cells exposed to resveratrol showed greater sensitivity than ceramide-treated cells. Ceramide-treated cells underwent a dose-dependent reduction in trans-membrane potential. Although both ceramide and resveratrol induced the expressions of caspase-3 and -7, the effect of inducible COX-2 was different in caspase-7 expression induced by ceramide compared to resveratrol. In summary, resveratrol and ceramide converge on an endocytosis-requiring, ERK1/2-dependent signal transduction pathway and induction of COX-expression as an essential molecular antecedent for subsequent p53-dependent apoptosis. In addition, expressions of caspase-3 and -7 are observed. However, a p38 kinase-dependent signal transduction pathway and change in mitochondrial potential are also involved in ceramide-induced apoptosis.

Early induction of cytokines/cytokine receptors and Cox2, and activation of NF-κB in 4-nitroquinoline 1-oxide-induced murine oral cancer model

The purpose of this study was to identify the genes induced early in murine oral carcinogenesis. Murine tongue tumors induced by the carcinogen, 4-nitroquinoline 1-oxide (4-NQO), and paired non-tumor tissues were subjected to microarray analysis. Hierarchical clustering of upregulated genes in the tumor tissues revealed an association of induced genes with inflammation. Cytokines/cytokine receptors induced early were subsequently identified, clearly indicating their involvement in oral carcinogenesis. Hierarchical clustering also showed that cytokine-mediated inflammation was possibly linked with Mapk6. Cox2 exhibited the greatest extent (9-18 fold) of induction in the microarray data, and its early induction was observed in a 2h painting experiment by RT-PCR. MetaCore analysis showed that overexpressed Cox2 may interact with p53 and transcriptionally inhibit expression of several downstream genes. A painting experiment in transgenic mice also demonstrated that NF-κB activates early independently of Cox2 induction. MetaCore analysis revealed the most striking metabolic alterations in tumor tissues, especially in lipid metabolism resulting from the reduction of Pparα and Rxrg. Reduced expression of Mapk12 was noted, and MetaCore analysis established its relationship with decreased efficiency of Pparα phosphorylation. In conclusion, in addition to cytokines/cytokine receptors, the early induction of Cox2 and NF-κB activation is involved in murine oral carcinogenesis.

Restoration of tumor suppressor p53 by differentially regulating pro- and anti-p53 networks in HPV-18-infected cervical cancer cells

Abrogation of functional p53 is responsible for malignant cell transformation and maintenance of human papilloma virus (HPV)-infected cancer cells. Restoration of p53 has, therefore, been regarded as an important strategy for molecular intervention of HPV-associated malignancies. Here we report that differential regulation of pro- and anti-p53 setups not only upregulates p53 transcription but also stabilizes and activates p53 protein to ensure p53-induced apoptosis in HPV-18-infected cervical cancer. Functional restoration of p53 can be achieved by non-steroidal anti-inflammatory drug celecoxib via multiple molecular mechanisms: (i) inhibition of p53 degradation by suppressing viral oncoprotein E6 expression, (ii) promoting p53 transcription by downmodulating cycloxygenase-2 (Cox-2) and simultaneously retrieving p53 from Cox-2 association and (iii) activation of p53 via ataxia telangiectasia mutated-/p38 mitogen-activated protein kinase-mediated phosphorylations at serine-15/-46 residues. That restored p53 is functional has been confirmed by its ability of transactivating Bax and p53-upregulated modulator of apoptosis, which in turn switch on the apoptotic machinery in these cells. Studies undertaken in biopsy samples of cervical carcinoma further validated celecoxib effect. Our approaches involving gene manipulation and pharmacological interference finally highlight that celecoxib alters pro- and anti-p53 networks, not in isolation but in concert, to rejuvenate p53-dependent apoptotic program in HPV-infected cervical cancer cells.

Expression of COX2 and p53 in Rat Esophageal Cancer Induced by Reflux of Duodenal Contents

Aim. Reflux of duodenal contents can induce mucosal injury, stimulate cell proliferation, and promote tumorigenesis. We examined the expression of COX2 and p53 in rat esophageal lesions induced by duodenal content reflux. Methods. Thirty 8-week-old male Wistar rats were exposed to duodenal content esophageal reflux. All animals underwent an esophagoduodenal anastomosis (EDA) with total gastrectomy in order to produce chronic esophagitis. Ten rats were the sham. Control. They were sacrificed at the 40th week. Their esophagi were examined for HE, COX2, p53, and proliferating cell nuclear antigen (PCNA). Results. After 40 weeks of reflux, dysplasia, squamous cell carcinoma (SCC), and adenocarcinoma (ADC) were found. PCNA labeling index was higher in dysplastic and cancer tissue than that in normal. Overexpression of COX2 was shown in ADC and SCC. Wild-type p53 accumulation was found in ADC, and not in SCC. Conclusion. Reflux of duodenal contents into the esophagus led to ADC and SCC in rats. COX2 may play an important role in esophageal cancer by duodenal content reflux. Our present results suggest an association between wild-type p53 accumulation and COX2 expression in ADC, with no such relation seen in SCC.

Cyclooxygenase inhibitors: scope of their use and development in cancer chemotherapy

The traditional nonsteroidal anti-inflammatory drugs (NSAIDs) exert their effect by inhibition of cyclooxygenase-1 (COX-1) as well as COX-2 enzymes. As COX-1 is responsible for maintaining normal biological functions, the nonselective inhibition of these enzymes caused side effects including gastrointestinal (GI) problems. Recently developed selective COX-2 inhibitors could reduce these adverse effects, but the evidence of cardiovascular side effects including an increased risk of myocardial infarction began to emerge, and some of the COX-2 inhibitors were eventually withdrawn from the market and this led to the downfall of this research. So, the discovery of novel COX-2 inhibitors with their safety profile became the biggest challenge in pharmaceutical research. However, recent mechanistic and clinical studies revolutionized this area by indicating the fact that COX-2 is involved in apoptosis resistance, angiogenesis, and tumor progression. Epidemiological data suggest that selective COX-2 inhibitors might prevent the development of cancers. Moreover, COX-2 is found to be overexpressed in many cancers thus making it an attractive therapeutic target for the prevention and treatment of a number of malignancies. The purpose of this review is to focus on the medicinal chemistry aspects of COX-2 inhibitors in cancer chemotherapy and recent reports on these inhibitors as anticancer agents. We attempted to cover only the COX inhibitors that showed anticancer activity, although a number of potent COX-2 inhibitors have been reported without their anticancer effects. Furthermore, structure-activity relationships (SAR) of different classes of compounds for COX-2 inhibition as well as anticancer activity, and their future applications are discussed.

COX-2 regulates the proliferation of glioma stem like cells

Cancer stem-like cells (CSCs) possessing features of neural precursor cells (NPC) influence initiation, recurrence and chemoresistance of glioblastoma multiforme (GBM). As inflammation is crucial for glioblastoma progression we investigated the effect of chronic IL-1β treatment on CSCs derived from glioblastoma cell line U87MG. Exposure to IL-1β for 10 days increased (i) accumulation of 8-OHdG - a key biomarker of oxidative DNA damage; (ii) DNA damage response (DDR) indicators γH2AX, ATM and DNA-PK; (iii) nuclear and cytoplasmic p53 and COX-2 levels and (iv) interaction between COX-2 and p53. Despite upregulating p53 expression IL-1β had no effect on cell cycle progression, apoptosis or self renewal capacity of CSCs. COX-2 inhibitor Celecoxib reduced self renewal capacity and increased apoptosis of both control and IL-1β treated CSCs. Therefore the ability of COX-2 to regulate proliferation of CSCs irrespective of exposure to IL-1β, warrants further investigation of COX-2 as a potential anti-glioma target.

Resveratrol and apoptosis

Resveratrol is a naturally occurring stilbene with desirable cardioprotective and anti-cancer properties. We have demonstrated the existence of a plasma membrane receptor for resveratrol near the arginine-glycine-aspartate (RGD) recognition site on integrin α(v)β₃ that is involved in stilbene-induced apoptosis of cancer cells. Resveratrol treatment in vitro causes activation and nuclear translocation of mitogen-activated protein kinase (ERK1/2), consequent phosphorylation of Ser-15 of p53, and apoptosis. An RGD peptide blocks these actions of resveratrol. By a PD98059-inhibitable process, resveratrol causes inducible COX-2 to accumulate in the nucleus where it complexes with pERK1/2 and p53. Chromatin immunoprecipitation reveals binding of nuclear COX-2 to promoters of certain p53-responsive genes, including PIG3 and Bax. NS-398, a specific pharmacologic inhibitor of COX-2, prevents resveratrol-induced complexing of nuclear ERK1/2 with COX-2 and with pSer-15-p53 and subsequent apoptosis; cyclooxygenase enzyme activity is not involved. Molecular steps in the pro-apoptotic action of resveratrol in cancer cells include induction of intranuclear COX-2 accumulation relevant to activation of p53. Epidermal growth factor, estrogen, and thyroid hormone act downstream of ERK1/2 to prevent resveratrol-induced apoptosis.

Inducible COX-2-dependent apoptosis in human ovarian cancer cells

Resveratrol is a naturally occurring trihydroxyl-diphenylethylene compound that has been shown experimentally to have beneficial effects in the treatment of cancer and cardiovascular disease. Resveratrol induces programmed cell death (apoptosis) in these cells and activates important signal transducing proteins including extracellular signal-regulated kinases (ERKs) 1 and 2 in cancer cells. Resveratrol also causes nuclear accumulation of the enzyme cyclooxygenase (COX)-2 and of the oncogene suppressor protein, p53. We have studied the molecular basis of the anticancer actions of resveratrol using human ovarian carcinoma (OVCAR-3) cells. Our findings include the following: (i) nuclear accumulation of COX-2 in resveratrol-treated cells is blocked by the ERK1/2 inhibitor, PD98059; (ii) an inhibitor of COX-2 activity, NS398, prevents accumulation of ERK1/2, COX-2, activated p53 and small ubiquitin-like modifier (SUMO-1) in the nucleus; (iii) apoptosis, quantitated by nucleosome enzyme-linked immunosorbent assay and the nuclear abundance of the pro-apoptotic protein, BcL-xs, were inhibited by NS398. This finding implicates nuclear COX-2 in p53-mediated apoptosis induced by resveratrol. Sumoylation is important to stabilization of p53 and a COX-2-SUMO-1 interaction suggests sumoylation of COX-2 in resveratrol-treated cells and (iv) chromatin immunoprecipitation studies showed binding of induced nuclear COX-2 to the promoter region of PIG3 and Bax, pro-apoptotic gene targets of transcriptionally active p53. Nuclear accumulation of activated ERK1/2 and sumolyated COX-2 are essential to resveratrol-induced pSer-15-p53-mediated apoptosis in human ovarian cancer cells.

A comparative immunohistochemical analysis of COX-2, p53, and Ki-67 expression in keratocystic odontogenic tumors

OBJECTIVE

The aim of the present study was to investigate the association between the expression of cyclooxygenase-2 (COX-2) in keratocystic odontogenic tumors (KCOT) and more commonly used markers, such as p53 and Ki-67.

STUDY DESIGN

Expression of cyclooxygenase-2 (COX-2) in 20 biopsy specimens of keratocystic odontogenic tumors (KCOT) has been analyzed and compared with the expression of previously reported markers Ki-67 and p53. Formalin-fixed, paraffin-embedded blocks were sectioned and used for hematoxylin-eosin (H&E) staining and incubated with anti-cox-2, anti-ki-67, and anti-p53 monoclonal antibodies for immunohistochemical examination. Detection of the COX-2 antibody was performed with the EnVision kit. Cellular staining pattern was cytoplasmatic for COX-2 and nuclear for both Ki-67 and p-53. Molecular expressions were semiquantitatively evaluated as negative (-), mild (±) or strong (+).

RESULTS

Mild to strong expression of COX-2 was observed in 20 (100%) of the cases. Fifteen (75%) of the KCOTs stained positive for p53 and 18 (90%) stained positive for Ki-67. There was no statistically relevant difference between the expressions of COX - 2, Ki-67, and p53.

CONCLUSIONS

Although COX-2 has rarely been used to assess the biological activity of the KCOT, the results portrayed in the current study and the current knowledge of the overall role known to be played by COX-2 in tumorigenesis suggest that COX-2 may be an important marker involved in the biological behavior of the KCOT. Larger studies are required to improve our knowledge of the possible role of COX-2 in the pathogenic mechanism involved in KCOT.

Cyclooxygenase-2, p53 and glucose transporter-1 as predictors of malignancy in the development of gallbladder carcinomas

Gallbladder carcinoma is the fifth most common malignancy of the gastrointestinal tract. The absolute characteristics of the disease are the high mortality rate due to the late discovery of a tumor and the low therapeutic possibilities except by surgical intervention. In oncology we can predict the outcome of the disease with a combination of classical standard clinico/pathological parameters (stage of the tumors, differentiation) and the intrinsic genetic and biochemical properties of the tumor. Such intrinzic properties of the tumors that are connected with the outcome of the disease are the denominators (markers). The author searched extensively for the expression and influence of 3 markers included in chronic inflammation and early carcinogenesis, cell cycle regulation and tissue hypoxia: cyclooxygenase-2 (COX-2), p53 gene and glucose transporter-1 protein (GLUT-1). The author discusses their possible role in the development as well as fighting this disease, if specific medications targeting them were available.

Clinicopathological correlations of cyclooxygenase-2, MDM2, and p53 expressions in surgically resectable pancreatic invasive ductal adenocarcinoma

OBJECTIVES

Cyclooxygenase-2 (COX-2) and p53 represent molecules linked to oncogenesis of pancreatic cancer, and there is also a known regulatory loop between mouse double minute 2 (MDM2) and p53. The complex cross talks between p53 and COX-2 and scenarios explaining patterns of p53 and COX-2 expressions in precursor and cancer lesions have been recently reported.

METHODS

The expressions of COX-2, p53, and MDM2 were examined using immunohistochemistry in 85 resection specimens of pancreatic ductal adenocarcinoma.

RESULTS

The positive tumor expression rates of COX-2, p53, and MDM2 were 69.4%, 60.0%, and 41.2%, respectively. Significant correlations between COX-2 and p53 expressions and between p53 and MDM2 expressions were revealed. In the Kaplan-Meier analysis, no statistically significant correlations were found among the levels of COX-2, p53, and MDM2 expressions and survival rates. In the multivariate Cox proportional hazards regression model, grade and nodal status showed to be a valuable predictor of a worse overall survival.

CONCLUSIONS

The reported findings confirmed the relationship of p53, MDM2, and COX-2 with the biological process of pancreatic cancer. The expression of none of the examined proteins showed to be a valuable independent prognostic factor. On the contrary, grade and nodal status showed to be a valuable predictor of a worse survival.

Identification and characterization of two novel isoforms of Pirh2 ubiquitin ligase that negatively regulate p53 independent of RING finger domains

Pirh2 is a newly identified E3 ubiquitin ligase known to inhibit tumor suppressor p53 function via ubiquitination and proteasomal degradation. We have identified two novel Pirh2 splice variants that encode different Pirh2 isoforms and named these Pirh2B and Pirh2C. Accordingly, the full-length protein is now classified as isoform Pirh2A. The central region of Pirh2 harbors a RING finger domain that is critical for its ubiquitin ligase function. The Pirh2B isoform lacks amino acids 171-179, whereas Pirh2C is missing C-terminal amino acids 180-261, which for each isoform results in a RING domain deletion and the abrogation of ubiquitin ligase activity. Our findings further indicate that the Pirh2B isoform but not the Pirh2C isoform is capable of binding to Pirh2A, suggesting that the C-terminal region absent in Pirh2C is critical for Pirh2-Pirh2 interactions. Similar to Pirh2A, both Pirh2B and Pirh2C interact with p53; however, interactions between p53 and Pirh2B appear stronger than those between p53 and Pirh2C. Interestingly, although both Pirh2B and Pirh2C are not able to promote in vitro p53 ubiquitination, both are capable of negatively regulating p53 protein stability and promoting the intracellular ubiquitination of p53. Furthermore, like Pirh2A, both isoforms are able to inhibit p53 transcriptional activity. We have also for the first time demonstrated that Pirh2A as well as the novel isoforms also interact directly with MDM2 within a region encompassing MDM2 acidic and zinc finger domains. It is therefore possible that Pirh2A and the novel Pirh2 isoforms identified in this study may also modulate p53 function by engaging MDM2.

Cyclooxygenase-2 functionally inactivates p53 through a physical interaction with p53

Cyclooxygenase-2 (COX-2), an endoplasmic reticulum-resident protein, has been known to promote tumorigenesis, but the exact mechanisms involved have not been identified. We have previously reported that COX-2 physically interacts with the tumor suppressor p53 and regulates its function. However, it remains to be elucidated how COX-2 can interact with p53 residing in different compartments and whether their interaction is involved in the regulation of p53 function. We here demonstrated that upon genotoxic stress, COX-2 and p53 accumulate in the nucleus, where they physically interact with one another. We also showed that an amino-terminal region (amino acids 1-126) of COX-2 interacts with the DNA-binding domain of p53. The p53-interacting region was critical for COX-2-mediated inhibition of p53 DNA-binding and transcriptional activity as well as p53- and genotoxic stress-induced apoptosis. In addition, an active site mutant of COX-2 (S516Q) as well as wild-type COX-2 potently inhibited p53 transcriptional activity and genotoxic stress-induced apoptosis. These results suggest that COX-2 principally inhibits p53 function through a catalytic activity-independent mechanism and that COX-2 inhibits p53 function through a physical interaction with p53 in the nucleus. These findings provide novel insight into the action mechanisms of COX-2 and strongly suggest that the functional inactivation of p53 by COX-2 can be one of the mechanisms by which COX-2 promotes tumorigenesis.

Immunoexpression of cyclooxygenase-2 and p53 in oral squamous cell carcinoma

PURPOSE

Cyclooxygenase-2 (COX-2) is an induced proinflammatory enzyme involved in various steps of carcinogenesis such as cell proliferation, reduction in apoptosis rates, and promotion of tumor angiogenesis. Mutation or inactivation of the tumor suppressor gene p53 is frequently observed in malignant neoplasms and is known to be involved in the early stages of carcinogenesis. Recent studies reveal a possible correlation between COX-2 and p53 expression in several malignant neoplasms. The present study analyzed the correlation between the expression of COX-2 and p53 in oral squamous cell carcinoma (OSCC) and evaluated the differences in the expression of these 2 proteins according to the histologic grade of malignancy of the tumor.

MATERIALS AND METHODS

Thirty-four cases of OSCC were graded according to the histologic grading system proposed by Bryne [Oral Dis 4(2) (1998) 70-77]. Immunoexpression of COX-2 and p53 was analyzed by counting 1000 neoplastic cells in 5 different fields at the deep invasive front of the tumor under a light microscope. On the basis of the number of immunopositive cells, the labeling index expressed as the percentage of positively stained cells was established for each marker.

RESULTS

Increased COX-2 expression in most specimens was observed, although no significant correlation was observed between COX-2 and p53 labeling indices (P > .05). Moreover, there were no significant differences in the expression of these proteins between high- and low-grade tumors (P > .05).

CONCLUSION

The increased expression of COX-2 in OSCC suggests a role for this protein in the pathogenesis and progression of oral cancer.

Expression of COX-2 is associated with accumulation of p53 in pancreatic cancer: analysis of COX-2 and p53 expression in premalignant and malignant ductal pancreatic lesions

OBJECTIVES

Cyclooxygenase-2 (COX-2) and tumor suppressor p53 are molecules that are linked to the oncogenesis of pancreatic cancer. COX-2 represents a key modulatory molecule in inflammation and carcinogenesis, and is known to be implicated in the positive regulation of growth and tumorigenesis. Abnormal expression of p53 is common in many human neoplasms including pancreatic cancer. Recent studies demonstrated functional interactions between p53 and COX-2. The p53-dependent upregulation of COX-2 was proposed to be another mechanism by which p53 could abate its own growth-inhibitory and apoptotic effects.

METHODS

In this study, we immunohistochemically analyzed the expression of COX-2 and p53 in 95 pancreatic resection specimens [adenocarcinomas, 95 lesions; pancreatic intraepithelial neoplasias (PanINs), 155; normal ducts, 70].

RESULTS

The expression of COX-2 increased progressively with the grade of ductal lesions (P<0.00001). A statistically significant difference of COX-2 expression between normal ducts and low-grade PanINs was revealed (P=0.0042). COX-2 overexpression was demonstrated in 82 PanINs (52.9%), and in 76 adenocarcinomas (80%). No significant correlation between the grade of adenocarcinoma and COX-2 expression was revealed (P=0.2). The expression of p53 again increased progressively with the grade of lesions (P<0.00001) with a significant increase in high-grade PanINs. A correlation between COX-2 and p53 expression levels in carcinomas was revealed (P=0.0002), and an accumulation of p53 was associated with COX-2 overexpression in premalignant and malignant ductal lesions.

CONCLUSION

These findings confirmed the generally accepted pancreatic cancer progression model, and supported the concept of the interactive role of COX-2 and p53 in pancreatic cancer carcinogenesis, which offers opportunities for targeted therapy and chemoprevention of pancreatic cancer using COX-2 inhibitors.

COX-2 and p53 in human sinonasal cancer: COX-2 expression is associated with adenocarcinoma histology and wood-dust exposure

The causal role of wood-dust exposure in sinonasal cancer (SNC) has been established in epidemiological studies, but the mechanisms of SNC carcinogenesis are still largely unknown. Increased amounts of COX-2 are found in both premalignant and malignant tissues, and experimental evidence link COX-2 to development of cancer. Many signals that activate COX-2 also induce tumor suppressor p53, a transcription factor central in cellular stress response. We investigated COX-2 and p53 expressions by immunohistochemistry in 50 SNCs (23 adenocarcinomas, and 27 squamous cell carcinomas (SCC); 48 analyzed for COX-2; 41 for p53). Occupational histories and smoking habits were available for majority of the cases. Most of the adenocarcinoma cases with exposure history data had been exposed to wood dust at work in the past (88%, 14/16). For smokers, 63% (12/19) presented with SSC, whereas 64% (7/11) of nonsmokers displayed adenocarcinoma. COX-2 was expressed at higher levels in adenocarcinoma as compared to SSC (p < 0.001). COX-2 expression showed significant association with occupational exposure to wood dust (p = 0.024), and with nonsmoking status (p = 0.001). No statistically significant associations between the exposures and p53 accumulation were found; however, the p53 accumulation pattern (p = 0.062 for wood dust exposure) resembled that of COX-2 expression. In summary, our findings show increased COX-2 expression in SNC adenocarcinoma with wood dust exposure, suggesting a role for inflammatory components in the carcinogenesis process. In contrast, SCCs predominated among smokers and expressed COX-2 rarely; this may suggest at least partially different molecular mechanisms.

Inflammation and prostate cancer: a future target for prevention and therapy?

Given its long natural history, prostate cancer has become an ideal model for the clinical and basic science study of neoplastic disease in distinct pathologic phases: tumor initiation, progression, invasion, and metastasis. Chronic or recurrent acute inflammation, a product of infectious agents or other sources, has potential promotional roles in each of these phases. Nonsteroidal anti-inflammatory drugs (NSAIDs), because of their ability to attenuate inflammation, as well as possibly direct anti-cancer properties associated with the inhibition of stromal cyclooxygenase-2, are potential candidates for clinical use in prostate cancer. Though epidemiologic evidence indicating a reduced risk of prostate cancer for NSAID users supports a chemoprotective benefit, observational assessment and clinical trials of these agents among large cohorts of prostate cancer patients are needed to determine their value in prostate cancer management.

Versatile functions of p53 protein in multicellular organisms

The p53 tumor suppressor plays a pivotal role in multicellular organism by enforcing benefits of the organism over those of an individual cell. The task of p53 is to control the integrity and correctness of all processes in each individual cell and in the organism as a whole. Information about the state of ongoing events in the cell is gathered through multiple signaling pathways that convey signals modifying activities of p53. Changes in the activities depend on the character of damages or deviations from optimum in processes, and the activity of p53 changes depending on the degree of the aberration, which results in either stimulation of repair processes and protective mechanisms, or the cessation of further cell divisions and the induction of programmed cell death. The strategy of p53 ensures genetic identity of cells and prevents the selection of abnormal cells. By accomplishing these strategic tasks, p53 may use a wide spectrum of activities, such as its ability to function as a transcription factor, by inducing or repressing different genes, or as an enzyme, by acting as an exonuclease during DNA reparation, or as an adaptor or a regulatory protein, intervening into functions of numerous signaling pathways. Loss of function of the p53 gene occurs in virtually every case of cancer, and deficiency in p53 is an unavoidable prerequisite to the development of malignancies. The functions of p53 play substantial roles in many other pathologies as well as in the aging process. This review is focused on strategies of the p53 gene, demonstrating individual mechanisms underlying its functions.

RBEL1 is a novel gene that encodes a nucleocytoplasmic Ras superfamily GTP-binding protein and is overexpressed in breast cancer

Rab family proteins are generally known as regulators of protein transport and trafficking. A number of Rab proteins have been implicated in cancer development and/or progression. Here we report the identification of a novel Rab-like protein, which we have named RBEL1 (Rab-like protein 1) for its higher similarity to the Rab subfamily members. We have characterized two isoforms of RBEL1 including the predominant RBEL1A and the less abundant RBEL1B that results from alternative splicing. Both isoforms harbor conserved N-terminal guanine trinucleotide phosphate (GTP) binding domains and, accordingly, are capable of binding to GTP. Both isoforms contain variable C termini and exhibit differential subcellular localization patterns. Unlike known Rabs that are mostly cytosolic, RBEL1B predominantly resides in the nucleus, whereas RBEL1A is localized primarily to the cytosol. Interestingly, a point mutation affecting RBEL1B GTP binding also alters the ability of mutant protein to accumulate in the nucleus, suggesting GTP binding potential to be important for RBEL1B nuclear localization. Our results also indicate that RBEL1A is overexpressed in about 67% of primary breast tumors. Thus, RBEL1A and RBEL1B are novel Rab-like proteins that localize in the nucleus and cytosol and may play an important role in breast tumorigenesis.

A novel natural compound, a cycloanthranilylproline derivative (Fuligocandin B), sensitizes leukemia cells to apoptosis induced by tumor necrosis factor related apoptosis-inducing ligand (TRAIL) through 15-deoxy-Delta 12, 14 prostaglandin J2 production

Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) induces apoptosis in many transformed cells; however, not all human tumors respond to TRAIL, potentially limiting its therapeutic utility. Although there is substantial evidence that cytotoxic drugs can augment sensitivity to TRAIL, it has become important to know what kinds of nontoxic drugs can be used together with TRAIL. We thus screened several natural compounds that can overcome resistance to TRAIL and found that a cycloanthranilylproline derivative, Fuligocandin B (FCB), an extract of myxomycete Fuligo candida, exhibited significant synergism with TRAIL. Treatment of the TRAIL-resistant cell line KOB with FCB and TRAIL resulted in apparent apoptosis, which was not induced by either agent alone. FCB increased the production of 15-deoxy-Delta(12,14) prostaglandin J(2) (15d-PGJ(2)), an endogenous PPAR gamma ligand, through activation of cyclooxygenase-2 (COX-2). This unique mechanism highlighted the fact that 15d-PGJ(2) directly enhanced sensitivity to TRAIL by inhibiting multiple antiapoptotic factors. More importantly, similar effects were observed in other leukemia cell lines irrespective of their origin. The enhancement was observed regardless of PPAR gamma expression and was not blocked even by peroxisome proliferator-activated receptor-gamma (PPAR gamma) siRNA. These results indicate that 15d-PGJ(2) sensitizes TRAIL-resistant cells to TRAIL in a PPAR gamma-independent manner and that the use of 15d-PGJ(2) or its inducers, such as FCB, is a new strategy for cancer therapy.

Aspirin blocks proliferation in colon cells by inducing a G1 arrest and apoptosis through activation of the checkpoint kinase ATM

Colorectal cancer (CRC) is the most common gastrointestinal malignancy. Most of the clinical data on CRC prevention have come from the use of aspirin. Besides inhibition of cyclooxygenases, aspirin has a diversity of molecular effects that counteract colon carcinogenesis. Aspirin restrains cell proliferation by inducing a G1 arrest in colorectal cells. To determine which cell cycle checkpoint pathways are involved in this response, colorectal cell lines wild-type or defective for p53 and p21Waf1/Cip1 were treated with aspirin or the anti-proliferative drug sulindac sulfide, then assayed for proliferative activity, for cell cycle progression and apoptosis, for the activation and phosphorylation of checkpoint components and for the transcriptional up-regulation of p21Waf1/Cip1 and Bax. Aspirin and sulindac sulfide induced a G1 arrest within 48 h. While all cell lines responded in a comparable way to sulindac sulfide, the aspirin-induced G1 arrest was dependent on p21Waf1/Cip1--as cells lacking the cyclin-dependent kinase inhibitor failed to show this arrest--and on ataxia-telangiectasia-mutated kinase (ATM)--as the inhibitor caffeine abrogated the checkpoint. Moreover, aspirin induced cell death mainly in cells expressing p53. Aspirin induced the phosphorylation of p53 at residue Ser15 within 8 h in a caffeine-dependent manner, and also caused the activation of checkpoint kinase 2 and the cleavage of caspase 7. Our results suggest that aspirin induces a G1 arrest and apoptosis by activating p53 and p21Waf1/Cip1 in an ATM-dependent way. By activating these checkpoint pathways, aspirin may restrain uncontrolled proliferation of colorectal cells, enhance their response to stresses such as DNA damage and promote entry of abnormal cells into apoptosis.

p53 modulation of the DNA damage response

The tumor suppressor p53 plays a central role in the DNA damage response. After exposure to genotoxic stress, p53 can both positively and negatively regulate cell fate. Initially, p53 promotes cell survival by inducing cell cycle arrest, DNA repair, and other pro-survival pathways. However, when cells accumulate DNA damage or demonstrate aberrant growth, p53 can direct the elimination of damaged cells. In this review, we will discuss the transcriptional-dependent and -independent roles of p53 in regulating the DNA damage response.

Cyclooxygenase-2 inhibits UVB-induced apoptosis in mouse skin by activating the prostaglandin E2 receptors, EP2 and EP4

Cyclooxygenase-2 (COX-2) is induced by UVB light and reduces UVB-induced epidermal apoptosis; however, the mechanism is unclear. Therefore, wild-type (WT) and COX-2-/- mice were acutely treated with UVB (5 kJ/m(2)), and apoptotic signaling pathways were compared. Following exposure, apoptosis was 2.5-fold higher in COX-2-/- compared with WT mice. Because prostaglandin E(2) (PGE(2)) is the major UV-induced prostaglandin and manifests its activity via four receptors, EP1 to EP4, possible differences in EP signaling were investigated in WT and COX-2-/- mice. Following UVB exposure, protein levels of EP1, EP2, and EP4 were elevated in WT mice, but EP2 and EP4 levels were 50% lower in COX-2-/- mice. Activated cyclic AMP-dependent protein kinase (PKA) and Akt are downstream in EP2 and EP4 signaling, and their levels were reduced in UVB-exposed COX-2-/- mice. Furthermore, p-Bad (Ser(136) and Ser(155)), antiapoptotic products of activated Akt and PKA, respectively, were significantly reduced in UVB-exposed COX-2-/- mice. To further study the roles of EP2 and EP4, UVB-exposed CD-1 mice were topically treated with indomethacin to block endogenous PGE(2) production, and PGE(2), the EP2 agonist (butaprost) or EP4 agonist (PGE(1) alcohol), was applied. Indomethacin reduced PKA and Akt activation by approximately 60%, but PGE(2) and the agonists restored their activities. Furthermore, both agonists decreased apoptosis in COX-2-/- mice by 50%. The data suggest that COX-2-generated PGE(2) has antiapoptotic roles in UVB-exposed mouse skin that involves EP2- and EP4-mediated signaling.

Selective COX-2 inhibitor, NS-398, suppresses cellular proliferation in human hepatocellular carcinoma cell lines via cell cycle arrest

AIM: To investigate the growth inhibitory mechanism of NS-398, a selective cyclooxygenase-2 (COX-2) inhibitor, in two hepatocellular carcinoma (HCC) cell lines (HepG2 and Huh7).

METHODS: HepG2 and Huh7 cells were treated with NS-398. Its effects on cell viability, cell proliferation, cell cycles, and gene expression were respectively evaluated by water-soluble tetrazolium salt (WST-1) assay, 4’-6-diamidino-2-phenylindole (DAPI) staining, flow cytometer analysis, and Western blotting, with dimethyl sulfoxide (DMSO) as positive control.

RESULTS: NS-398 showed dose- and time-dependent growth-inhibitory effects on the two cell lines. Proliferating cell nuclear antigen (PCNA) expressions in HepG2 and Huh7 cells, particularly in Huh7 cells were inhibited in a time- and dose-independent manner. NS-398 caused cell cycle arrest in the G1 phase with cell accumulation in the sub-G1 phase in HepG2 and Huh7 cell lines. No evidence of apoptosis was observed in two cell lines.

CONCLUSION: NS-398 reduces cell proliferation by inducing cell cycle arrest in HepG2 and Huh7 cell lines, and COX-2 inhibitors may have potent chemoprevention effects on human hepatocellular carcinoma.

Comparison of gene expression profiles in core biopsies and corresponding surgical breast cancer samples

Introduction

Gene expression profiling has been successfully used to classify breast cancer into clinically distinct subtypes, and to predict the risk of recurrence and treatment response. The aim of this study was to investigate whether the gene expression profile (GEP) detected in a core biopsy (CB) is representative for the entire tumor, since CB is an important tool in breast cancer diagnosis. Moreover, we investigated whether performing CBs prior to the surgical excision could influence the GEP of the respective tumor.

Methods

We quantified the RNA expression of 60 relevant genes by quantitative real-time PCR in paired CBs and surgical specimens from 22 untreated primary breast cancer patients. Subsequently, expression data were compared with independent GEPs obtained from tumors of 317 patients without preceding CB.

Results

In 82% of the cases the GEP detected in the CB correlated very well with the corresponding profile in the surgical sample (r_s ≥ 0.95, p < 0.001). Gene-by-gene analysis revealed four genes significantly elevated in the surgical sample compared to the CB; these comprised genes mainly involved in inflammation and the wound repair process as well as in tumor invasion and metastasis.

Conclusion

A GEP detected in a CB are representative for the entire tumor and is, therefore, of clinical relevance. The observed alterations of individual genes after performance of CB deserve attention since they might impact the clinical interpretation with respect to prognosis and therapy prediction of the GEP as detected in the surgical specimen following CB performance.

Cross-talks between cyclooxygenase-2 and tumor suppressor protein p53: Balancing life and death during inflammatory stress and carcinogenesis

Overexpression of Cyclooxygenase-2 (COX-2) is observed in most tumor types. Increased COX-2 activity and synthesis of prostaglandins stimulates proliferation, angiogenesis, invasiveness and inhibits apoptosis. Many stress and proinflammatory signals induce COX-2 expression, including oxyradicals or DNA-damaging agents. The latter also induces p53, a transcription factor often inactivated by mutation in cancer. Several studies have identified complex cross-talks between p53 and COX-2, whereby p53 can either up- or down-regulate COX-2, which in turn controls p53 transcriptional activity. However, the molecular basis of these effects are open to debate, in particular since no p53 binding sequences have been identified in COX-2 regulatory regions. In this review, we summarize the molecular mechanisms by which COX-2 contributes to carcinogenesis and discuss the experimental set-up, results and conclusions of studies analyzing cross-talks between p53 and COX-2. We propose 2 scenarios accounting for overexpression of COX-2 in precursor and cancer lesions. In the "inflammatory" scenario, p53, activated by DNA damage induced by oxygen and nitrogen species, recruits NF-kappaB to activate COX-2, resulting in antiapoptotic effects that contribute to cell expansion in inflammatory precursor lesions. In the "constitutive proliferation" scenario, oncogenic stress due to activation of growth signaling cascades may upregulate COX-2 promoter independently of NF-kappaB and p53, synergizing with TP53 mutation to promote cancer progression. These 2 scenarios, although not mutually exclusive, may account for the diversity of the correlations between COX-2 expression and TP53 mutation, which vary according to cancer types and biological contexts, and have implications for the use of COX-2 inhibitors in cancer prevention and therapy.

The p53 pathway and outcome among patients with T1G3 bladder tumors

PURPOSE

The aim was to analyze Tp53 and HDM2 in T1G3 bladder tumors and to determine the prognostic value of their alterations.

EXPERIMENTAL DESIGN

Tumors (n = 119) were extracted from a prospective study of 1,356 bladder cancers. Tp53 mutations (exons 4-9) were assessed by sequencing of PCR products. HDM2 dose was assessed by quantitative PCR. p53, HDM2, and the products of p53 target genes were analyzed by immunohistochemistry. Cases were distributed in three categories. The association with prognosis was determined using Kaplan-Meier and Cox analyses.

RESULTS

Eighty-five percent of tumors harbored alterations in Tp53 or HDM2. In group 1 (n = 77), 69 tumors had inactivating Tp53 mutations (58%), and 8 had HDM2 gains (7%). Group 2 (n = 24) comprised tumors overexpressing p53 in the absence of mutations (20%). Group 3 tumors (n = 18) had no alterations. HDM2 gains were associated to HDM2 overexpression and to wild-type Tp53. Expression of type 1 insulin-like growth factor receptor, 14-3-3 sigma, and cyclooxygenase-2 was similar in groups 1 and 2 and significantly different from group 3. Survivin was expressed in the majority of tumors regardless of p53 pathway status. Taking group 3 as reference, the hazard ratios (HR) for recurrence, progression, and death were not significantly different in the other patient groups. HRs for recurrence were 1.13 for group 1 [95% confidence interval (95% CI), 0.25-5.03] and 1.40 for group 2 (95% CI, 0.27-7.20). HRs for progression were 0.50 for group 1 (95% CI, 0.18-1.40) and 0.25 for group 2 (95% CI, 0.05-1.29).

CONCLUSIONS

The p53 pathway is inactivated in most T1G3 bladder tumors. These genetic alterations do not independently predict patient's prognosis.

Cyclooxygenase inhibitors modulate the p53/HDM2 pathway and enhance chemotherapy-induced apoptosis in neuroblastoma

Cyclooxygenase-2 (COX-2) is upregulated in many tumors including neuroblastoma, and its overexpression has been implicated in resistance to p53-dependent apoptosis. Although p53 is rarely mutated in neuroblastoma, the p53 protein is rendered inactive via several mechanisms including sequestration in the cytoplasm. Here, we show that COX inhibitors inhibit the growth of neuroblastoma and when combined with low doses of chemotherapy, exert synergistic effects on neuroblastoma cells. Following COX inhibitor treatment, HDM2, which targets p53 for ubiquitin-mediated degradation, is downregulated, resulting in an attenuation of p53 ubiquitination and an increase in p53 half-life. The level of HDM2 phosphorylation at ser166, which influences both HDM2 and p53 subcellular distribution, is markedly diminished in response to COX inhibitors and is associated with increased p53 nuclear localization. Combining COX inhibitors with low-dose chemotherapy potentiates apoptosis and p53 stability, nuclear localization, and activity. p53 knockdown by siRNA resulted in the rescue of COX-inhibitor-treated cells, indicating that COX inhibitor-induced apoptosis is, at least in part, p53-dependent. Taken together, these results provide the first evidence that COX inhibitors enhance chemosensitivity in neuroblastoma via downregulating HDM2 and augmenting p53 stability and nuclear accumulation.

Resveratrol-induced cyclooxygenase-2 facilitates p53-dependent apoptosis in human breast cancer cells

Cyclooxygenase-2 (COX-2) is antiapoptotic and is implicated in tumorigenesis. Recent reports, however, have also ascribed a proapoptotic action to inducible COX-2. We show here for the first time that a stilbene, resveratrol, induces nuclear accumulation of COX-2 protein in human breast cancer MCF-7 and MDA-MB-231 cell cultures. The induction of COX-2 accumulation by resveratrol is mitogen-activated protein kinase (MAPK; extracellular signal-regulated kinase 1/2)- and activator protein 1- dependent. Nuclear COX-2 in resveratrol-treated cells colocalizes with Ser(15)-phosphorylated p53 and with p300, a coactivator for p53-dependent gene expression. The interaction of COX-2, p53, and p300, as well as resveratrol-induced apoptosis, was inhibited by a MAPK activation inhibitor, PD98059. A specific inhibitor of COX-2, NS398, and small interfering RNA knockdown of COX-2 were associated with reduced p53 phosphorylation and consequent decrease in p53-dependent apoptosis in resveratrol-treated cells. We conclude that nuclear accumulation of COX-2 can be induced by resveratrol and that the COX has a novel intranuclear colocalization with Ser(15)-phosphorylated p53 and p300, which facilitates apoptosis in resveratrol-treated breast cancer cells.

Ionizing radiation suppresses FAP-1 mRNA level in A549 cells via p53 activation

Ionizing radiation (IR) is known to upregulate cell surface Fas through p53 activation in various cells. However, the signaling pathway intermediating between p53 activation and cell surface Fas upregulation remains to be elucidated. Recently, Fas-associated phosphatase-1 (FAP-1) has been reported to associate with Fas and inhibit cell surface Fas expression. We evaluated the expression of FAP-1 mRNA following IR in A549 cells. Ionizing radiation inhibited the expression of FAP-1 mRNA. Pretreatment with p53 inhibitor pifithrin alpha cancelled the IR-induced downregulation of FAP-1 mRNA. These results suggest that IR-induced p53 activation may upregulate cell surface Fas via the down-modulation of FAP-1.

APRIL and BAFF promote increased viability of replicating human B2 cells via mechanism involving cyclooxygenase 2

Of relevance to both protective and pathogenic responses to Ag is the recent finding that soluble molecules of the innate immune system, i.e., IL-4, B cell-activation factor of the TNF family (BAFF), and C3, exhibit significant synergy in promoting the clonal expansion of human B2 cells following low-level BCR ligation. Although IL-4, BAFF, and C3dg each contribute to early cell cycle entry and progression to S phase, only BAFF promotes later sustained viability of progeny needed for continued cycling. The present study sought to further clarify the mechanisms for BAFF's multiple functions. By comparing BAFF and a proliferation-inducing ligand (APRIL) efficacy at different stages in the response (only BAFF binds BR3; both bind transmembrane activator and calcium modulator and cyclophilin ligand interactor (TACI) and B cell maturation Ag, the early role was attributed to BR3, while the later role was attributed to TACI/B cell maturation Ag. Importantly, BAFF- and APRIL-promoted viability of cycling lymphoblasts was associated with sustained expression of cyclooxygenase 2 (COX-2), the rate-limiting enzyme for PGE2 synthesis, within replicating cells. Supernatants of cultures with BAFF and APRIL contained elevated PGE2. Although COX-2 inhibitors diminished daughter cell viability, exogenous PGE2 (1-1000 nM) increased the viability and recovery of lymphoblasts. Increased yield of viable progeny was associated with elevated Mcl-1, suggesting that a BAFF/APRIL --> TACI --> COX-2 --> PGE2--> Mcl-1 pathway reduces activation-related, mitochondrial apoptosis in replicating human B2 cell clones.

Cyclo-oxygenase-2 (Cox-2) expression and resistance to platinum versus platinum/paclitaxel containing chemotherapy in advanced ovarian cancer

Background

Cyclo-oxygenase-2 (COX-2), the key enzyme in the conversion of arachidonic acid to prostaglandins, is involved in critical steps of tumor onset and progression, and is a strong predictor of chemotherapy resistance and poor outcome in advanced ovarian cancer. To our knowledge, no data has been reported until now about the association between COX-2 status and response to different chemotherapy regimens.

Methods

A retrospective study was performed to investigate the association of COX-2 with outcome and response to platinum versus platinum/paclitaxel in 68 primary ovarian cancer. COX-2 immunoreaction was performed on paraffin-embedded sections by using rabbit polyclonal antiserum against COX-2.

Results

In the overall series, COX-2 positivity was found in a statistically significant higher percentage of not responding cases than in patients responding to chemotherapy (n = 15/21; 71.4% versus n = 17/47; 36.1%; p value = 0.0072). A higher percentage of COX-2 positivity was found in patients unresponsive (n = 11/13; 84.6%) versus patients responsive to platinum-based chemotherapy (n = 9/26; 34.6%). In cases administered platinum/paclitaxel, COX-2 positivity was found in 4 out of 8 (50%) of un responsive versus 8 out of 21 (38.1%) of responsive cases. Logistic regression analysis of parameters likely to affect response to treatment resulted in a p value = 0.17 for the interaction COX-2/type of treatment.

Conclusion

Although these findings need to be confirmed in a larger series, our study suggests a possible indication that there is a difference in the influence of COX-2 on response depending on treatment regimen.

Overexpression of Cox-2 in Human Osteosarcoma Cells Decreases Proliferation and Increases Apoptosis

Overexpression of cyclooxygenase-2 (COX-2) is generally considered to promote tumorigenesis. To investigate a potential role of COX-2 in osteosarcoma, we overexpressed COX-2 in human osteosarcoma cells. Saos-2 cells deficient in COX-2 expression were retrovirally transduced or stably transfected with murine COX-2 cDNA. Functional expression of COX-2 was confirmed by Northern and Western analyses and prostaglandin production. Overexpression of COX-2 reduced cell numbers by 50% to 70% compared with controls. Decreased proliferation in COX-2-overexpressing cells was associated with cell cycle prolongation in G(2)-M. Apoptosis, measured by both Annexin V binding assay and terminal deoxyribonucleotidyl transferase-mediated dUTP nick end labeling staining, was increased in cells overexpressing COX-2, and the increase was not reversed by treatment with NS-398, indicating that the effects were not mediated by prostaglandins. Retroviral COX-2 overexpression in two other human osteosarcoma cell lines, U2OS and TE85, also decreased cell viability. However, in the human colon carcinoma HCT-116 cell line, which is deficient in COX-2, retroviral overexpression of COX-2, at similar efficiency as in Saos-2 cells, increased resistance to apoptosis. Reactive oxygen species (ROS), measured by flow cytometry, were increased by COX-2 overexpression in Saos-2 cells but not in HCT-116 cells. Inhibition of peroxidase activity, but not of COX activity, blocked the ROS increase. Antioxidants blocked the increase in ROS and the increase in apoptosis due to COX-2 overexpression in Saos-2 cells. Our results suggest that (a) COX-2 overexpression in osteosarcoma cells may increase resistance to tumorigenesis by increasing ROS to levels that decrease cell viability and (b) the effects of COX-2 overexpression are cell type/tissue dependent.