Cyclooxygenase-2 inhibition inhibits PI3K/AKT kinase activity in epithelial ovarian cancer

In vitro screen of a small molecule inhibitor drug library identifies multiple compounds that synergize with oncolytic myxoma virus against human brain tumor-initiating cells

BACKGROUND

Brain tumor-initiating cells (BTICs) are stem-like cells hypothesized to form a disease reservoir that mediates tumor recurrence in high-grade gliomas. Oncolytic virotherapy uses replication-competent viruses to target and kill malignant cells and has been evaluated in clinic for glioma therapy with limited results. Myxoma virus (MyxV) is a safe and highly effective oncolytic virus (OV) in conventional glioma models but, as seen with other OVs, is only modestly effective for patient-derived BTICs. The objective of this study was to determine whether MyxV treatment against human BTICs could be improved by combining chemotherapeutics and virotherapy.

METHODS

A 73-compound library of drug candidates in clinical use or preclinical development was screened to identify compounds that sensitize human BTICs to MyxV treatment in vitro, and synergy was evaluated mathematically in lead compounds using Chou-Talalay analyses. The effects of combination therapy on viral gene expression and viral replication were also assessed.

RESULTS

Eleven compounds that enhance MyxV efficacy were identified, and 6 were shown to synergize with the virus using Chou-Talalay analyses. Four of the synergistic compounds were shown to significantly increase viral gene expression, indicating a potential mechanism for synergy. Three highly synergistic compounds (axitinib, a VEGFR inhibitor; rofecoxib, a cyclooxygenase-2 inhibitor; and pemetrexed, a folate anti-metabolite) belong to classes of compounds that have not been previously shown to synergize with oncolytic viruses in vitro.

CONCLUSIONS

This study has identified multiple novel drug candidates that synergistically improve MyxV efficacy in a preclinical BTIC glioma model.

Inhibition of cyclooxygenase-1 and cyclooxygenase-2 impairs Trypanosoma cruzi entry into cardiac cells and promotes differential modulation of the inflammatory response

The intracellular protozoan parasite Trypanosoma cruzi is the etiologic agent of Chagas disease, a serious disorder that affects millions of people in Latin America. Cell invasion by T. cruzi and its intracellular replication are essential to the parasite's life cycle and for the development of Chagas disease. Here, we present evidence suggesting the involvement of the host's cyclooxygenase (COX) enzymes during T. cruzi invasion. Pharmacological antagonists for COX-1 (aspirin) and COX-2 (celecoxib) caused marked inhibition of T. cruzi infection when rat cardiac cells were pretreated with these nonsteroidal anti-inflammatory drugs (NSAIDs) for 60 min at 37°C before inoculation. This inhibition was associated with an increase in the production of NO and interleukin-1β and decreased production of transforming growth factor β (TGF-β) by cells. Taken together, these results indicate that COX-1 more than COX-2 is involved in the regulation of anti-T. cruzi activity in cardiac cells, and they provide a better understanding of the influence of TGF-β-interfering therapies on the innate inflammatory response to T. cruzi infection and may represent a very pertinent target for new therapeutic treatments of Chagas disease.

Discovery of colorectal cancer PIK3CA mutation as potential predictive biomarker: power and promise of molecular pathological epidemiology

Regular use of aspirin reduces incidence and mortality of various cancers, including colorectal cancer. Anticancer effect of aspirin represents one of the 'Provocative Questions' in cancer research. Experimental and clinical studies support a carcinogenic role for PTGS2 (cyclooxygenase-2), which is an important enzymatic mediator of inflammation, and a target of aspirin. Recent 'molecular pathological epidemiology' (MPE) research has shown that aspirin use is associated with better prognosis and clinical outcome in PIK3CA-mutated colorectal carcinoma, suggesting somatic PIK3CA mutation as a molecular biomarker that predicts response to aspirin therapy. The PI3K (phosphatidylinositol-4,5-bisphosphonate 3-kinase) enzyme has a pivotal role in the PI3K-AKT signaling pathway. Activating PIK3CA oncogene mutations are observed in various malignancies including breast cancer, ovarian cancer, brain tumor, hepatocellular carcinoma, lung cancer and colon cancer. The prevalence of PIK3CA mutations increases continuously from rectal to cecal cancers, supporting the 'colorectal continuum' paradigm, and an important interplay of gut microbiota and host immune/inflammatory reaction. MPE represents an interdisciplinary integrative science, conceptually defined as 'epidemiology of molecular heterogeneity of disease'. As exposome and interactome vary from person to person and influence disease process, each disease process is unique (the unique disease principle). Therefore, MPE concept and paradigm can extend to non-neoplastic diseases including diabetes mellitus, cardiovascular diseases, metabolic diseases, and so on. MPE research opportunities are currently limited by paucity of tumor molecular data in the existing large-scale population-based studies. However, genomic, epigenomic and molecular pathology testings (for example, analyses for microsatellite instability, MLH1 promoter CpG island methylation, and KRAS and BRAF mutations in colorectal tumors) are becoming routine clinical practices. In order for integrative molecular and population science to be routine practice, we must first reform education curricula by integrating both population and molecular biological sciences. As consequences, next-generation hybrid molecular biological and population scientists can advance science, moving closer to personalized precision medicine and health care.

High prevalence of mTOR complex activity can be targeted using Torin2 in papillary thyroid carcinoma

The mammalian target of rapamycin (mTOR) signaling cascade is a key regulatory pathway controlling initiation of messenger RNA in mammalian cells. Although dysregulation of mTOR signaling has been reported earlier in cancers, there is paucity of data about mTOR expression in papillary thyroid carcinoma (PTC). Therefore, in this study, we investigated the presence of mTORC2 and mTORC1 complexes in a large cohort of >500 PTC samples. Our clinical data showed the presence of active mTORC1 and mTORC2 in 81 and 39% of PTC samples, respectively. Interestingly, coexpression of mTORC1 and mTORC2 activity was seen in a 32.5% (164/504) of the PTC studied and this association was statistically significant (P = 0.0244). mTOR signaling complex was also found to be associated with activated AKT and 4E-BP1. In vitro, using Torin2, a second-generation mTOR inhibitor or gene silencing of mTOR expression prevented mTORC1 and mTORC2 activity leading to inactivation of P70S6, 4E-BP1, AKT and Bad. Inhibition of mTOR activity led to downregulation of cyclin D1, a gene regulated by messenger RNA translation via phosphorylation of 4E-BP1. Torin2 treatment also inhibited cell viability and induced caspase-dependent apoptosis via activation of mitochondrial apoptotic pathway in PTC cells. Finally, Torin2 treatment induces anticancer effect on PTC xenograft tumor growth in nude mice via inhibition of mTORC1 and mTORC2 and its associated pathways. Our results suggest that coexpression of mTORC1 and mTORC2 is seen frequently in the clinical PTC samples and dual targeting of mTORC1 and mTORC2 activity may be an attractive therapeutic target for treatment of PTC.

Design, synthesis and structure-activity relationship studies of novel and diverse cyclooxygenase-2 inhibitors as anti-inflammatory drugs

Because of the pivotal role of cyclooxygenase (COX) in the inflammatory processes, non-steroidal anti-inflammatory drugs (NSAIDs) that suppress COX activities have been used clinically for the treatment of inflammatory diseases/syndromes; however, traditional NSAIDs exhibit serious side-effects such as gastrointestinal damage and hyper sensitivity owing to their COX-1 inhibition. Also, COX-2 inhibition-derived suppressive or preventive effects against initiation/proliferation/invasion/motility/recurrence/metastasis of various cancers/tumours such as colon, gastric, skin, lung, liver, pancreas, breast, prostate, cervical and ovarian cancers are significant. In this study, design, synthesis and structure-activity relationship (SAR) of various novel {2-[(2-, 3- and/or 4-substituted)-benzoyl, (bicyclic heterocycloalkanophenyl)carbonyl or cycloalkanecarbonyl]-(5- or 6-substituted)-1H-indol-3-yl}acetic acid analogues were investigated to seek and identify various chemotypes of potent and selective COX-2 inhibitors for the treatment of inflammatory diseases, resulting in the discovery of orally potent agents in the peripheral-inflammation model rats. The SARs and physicochemical properties for the analogues are described as significant findings. For graphical abstract: see Supplementary Material. ( www.informahealthcare.com/enz ).

Aspirin and colorectal cancer: back to the future

Abundant epidemiologic evidence indicates that regular and long-term use of aspirin is associated with a significant reduction in the incidence of colorectal cancer. The long duration of aspirin needed to prevent colorectal cancer is believed to be due to inhibition of precursor lesions known as adenomas, the recurrence of which is inhibited by aspirin in randomized trials. Aspirin intake has also been associated with a statistically significant improvement in patient survival after curative resection of colorectal cancer in large observational studies. In these cohorts, the survival benefit of aspirin was shown to depend upon the level of COX-2 expression in the primary colorectal cancer. More recent analysis of patient tumors from these observational cohorts suggests that the benefit of aspirin may be limited to specific molecular subtypes. Aspirin intake following colorectal cancer resection was associated with a significant improvement of survival in patients whose tumors carried mutant, but not wild-type, copies of the phosphoinositide 3-kinase (PI3KCA) gene, especially tumors that overexpressed COX-2. A mechanistic explanation is suggested by the finding that inhibition of COX-mediated prostaglandin E2 synthesis by aspirin attenuates PI3K signaling activity that is known to regulate cancer cell proliferation and survival. Aspirin has also been shown to reduce the incidence of colorectal cancers bearing wild-type, but not mutant alleles of the BRAF(V600E) oncogene. Although provocative, the potential utility of these molecular markers for predicting aspirin efficacy awaits prospective evaluation in clinical trials. If validated, these findings may support a personalized approach to using aspirin for the therapy of colorectal cancer.

Aspirin Blocks EGF-stimulated Cell Viability in a COX-1 Dependent Manner in Ovarian Cancer Cells

Objective: Although aspirin has been associated with a reduction of the risk of cancer when used as a nonsteroidal anti-inflammatory drug, its use to reduce the risk of ovarian cancer is controversial. Ovarian cancer cells usually express high levels of cyclooxygenase-1 (COX)-1. Because aspirin is a rather selective inhibitor of COX-1, the ability of aspirin to reduce the risk of ovarian cancer may be dependent on the level of COX-1 expression in those cells. Furthermore, epidermal growth factor receptor (EGFR) is frequently overexpressed in the malignant phenotype of ovarian cancer leading to increased cell proliferation and survival. Here we investigated if aspirin attenuates EGFR-activated ovarian cancer cell growth in a COX-1 dependent manner.

Methods: Cell viability assays and Western blot analyses were used to determine the effect of aspirin on EGF-stimulated cell proliferation. Gene silencing and gene expression techniques were employed to knockdown or to express COX-1, respectively.

Results: Aspirin inhibited cell viability induced by EGF in a dose dependent manner in COX-1 positive ovarian cancer cells. On the other hand, aspirin had no effect on cell viability in COX-1 negative ovarian cancer cells. In particular, aspirin decreased phosphorylated Akt and Erk activated by EGF. COX-1 silencing in COX-1 positive cells attenuated the inhibitory effect of aspirin on EGF-stimulated cell viability. Furthermore, we developed a COX-1 expressing cell line (SKCOX-1) by stably transfecting COX-1 expression vector into COX-1 negative SKOV-3 cells. SKCOX-1 cells were more responsive to aspirin when compared to cells transfected with empty vector, and decreased EGF-activated Akt and Erk as well as cell viability.

Conclusions: Taken together, aspirin inhibits viability of ovarian cancer cells by blocking phosphorylation of Akt and Erk activated by EGF. Thus it may potentiate the therapeutic efficacy of drugs used to treat COX-1 positive ovarian cancer subsets.

Melatonin overcomes apoptosis resistance in human hepatocellular carcinoma by targeting survivin and XIAP

Apoptosis resistance in hepatocellular carcinoma (HCC) is one of the most significant factors for hepatocarcinogenesis and tumor progression, and leads to resistance to conventional chemotherapy. It is well known that inhibitor of apoptosis proteins (IAPs) play key roles in apoptosis resistance, it has become an important target for antitumor therapy. In this study, we examined if melatonin, the main secretory product of the pineal gland, targeted IAPs, leading to the inhibition of apoptosis resistance. To accomplish this, we first observed that four members of IAPs (cIAP-1, cIAP-2, survivin, and XIAP) were overexpressed in human HCC tissue. Interestingly, melatonin significantly inhibited the growth of HepG2 and SMMC-7721 cells and promoted apoptosis along with the downregulation of survivin and XIAP, but had no effect on the expression of cIAP-1 and cIAP-2. These data suggest that the inhibition of survivin and XIAP by melatonin may play an important part in reversing apoptosis resistance. Notably, cIAP-1, survivin and XIAP were significantly associated with the coexpression of COX-2 in human HCC specimens. Melatonin also reduced the expression of COX-2 and inhibited AKT activation in HepG2 and SMMC-7721 cells. Inhibition of COX-2 activity with the selective inhibitor, NS398, and inhibition of AKT activation using the PI3K inhibitor, LY294002, in tumor cells confirmed that melatonin-induced apoptosis was COX-2/PI3K/AKT-dependent, suggesting that the COX-2/PI3K/AKT pathway plays a role in melatonin inhibition of IAPs. Taken together, these results suggest that melatonin overcomes apoptosis resistance by the suppressing survivin and XIAP via the COX-2/PI3K/AKT pathway in HCC cells.

Biomarkers in precision therapy in colorectal cancer

Colorectal cancer (CRC) is the most commonly diagnosed cancer in Europe. Because CRC is also a major cause of cancer-related deaths worldwide, a lot of research has been focused on the discovery and development of biomarkers to improve the diagnostic process and to predict treatment outcomes. Up till now only a few biomarkers are recommended by expert panels. Current TNM criteria, however, cause substantial under- and overtreatment of CRC patients. Consequently, there is a growing need for new and efficient biomarkers to ensure optimal treatment allocation. An ideal biomarker should be easily translated into clinical practice, to identify patients who can be spared from treatment or benefit from therapy, ultimately resulting in precision medicine in the future. In this review we aim to provide an overview of a number of frequently studied biomarkers in CRC and, at the same time, we will emphasize the challenges and controversies that withhold the clinical introduction of these biomarkers. We will discuss both prognostic and predictive markers of chemotherapy, aspirin therapy as well as overall therapy toxicity. Currently, only mutant KRAS, mutant BRAF, MSI and the Oncotype DX® Colon Cancer Assay are used in clinical practice. Other biomarker studies showed insufficient evidence to be introduced into clinical practice. Divergent patient selection criteria, absence of validation studies and a large number of single biomarker studies are possibly responsible. We therefore recommend that future studies focus on combining key markers, rather than analysing single markers, standardizing study protocols, and validate the results in independent study cohorts, followed by prospective clinical trials.

Targeting angiogenesis in the pathological ovary

The ovary is a key tissue in the study of physiological neo-vascularisation in the adult and its study has highlighted important molecules involved in the regulation of angiogenesis in vivo. These include vascular endothelial growth factor, delta-like ligand 4, thrombospondin-1, prokineticin-1 and prostaglandin E2. Targeting these molecular pathways has therapeutic potential and their manipulation has an increasing preclinical and clinical role in the management of the pathological ovary. Targeting angiogenic pathways has utility in the promotion of ovarian angiogenesis to improve tissue and follicle survival and function as well as the prevention and management of ovarian hyperstimulation syndrome. There is a theoretical possibility that targeting angiogenesis may improve the function of the polycystic ovary and a real role for targeting angiogenesis in ovarian cancer.

Celecoxib inhibits insulin-like growth factor 1 induced growth and invasion in non-small cell lung cancer

Despite a large number of studies indicating that celecoxib plays an important role in the prevention and treatment of tumors, the detailed molecular mechanisms are not well understood. The aim of the present study was to investigate the effect of celecoxib on insulin-like growth factor 1 (IGF-1)-induced growth and invasion in non-small cell lung cancer (NSCLC). For these experiments, IGF-1-induced cell growth and invasion were analyzed in A549 cells in the presence and absence of celecoxib. The effects of celecoxib on the expression of phosphorylated type-1 IGF receptor (IGF-1R) and phosphorylated AKT (p-AKT) were examined using western blot analysis. The influence of celecoxib on IGF-binding protein-3 (IGFBP-3) expression was analyzed using ELISA. Celecoxib inhibited IGF-1-stimulated growth and invasion in a dose-dependent manner. Celecoxib also reduced the expression of IGF-1R, IGFBP-3 and phosphorylation of AKT. The results suggest that modulating the IGF axis may be a new mechanism for the anticancer effect of celecoxib on NSCLC.

Nonsteroidal anti-inflammatory drugs and risk of ovarian cancer: systematic review and meta-analysis of observational studies

OBJECTIVE

Several observational studies have investigated the association between nonsteroidal anti-inflammatory drug (NSAID) use and ovarian cancer risk, but with conflicting results. We performed a systematic review and meta-analysis of the association between NSAID use and ovarian cancer risk.

DESIGN

Systematic review and meta-analysis of observational studies published until September 2012.

SETTING

Studies were identified from the PubMed database.

POPULATION

Fourteen case-control and seven cohort studies were included.

METHODS

Pooled relative risks (RRs) with corresponding 95% confidence intervals (CI) for aspirin and non-aspirin NSAIDs, separately, were calculated. Both fixed and random effect models were applied, but only random effect pooled RRs are presented. Risk estimates for invasive and borderline ovarian tumors combined and for invasive ovarian tumors only were calculated. Furthermore, heterogeneity and publication bias were evaluated.

MAIN OUTCOME MEASURES

Ovarian cancer.

RESULTS

In the combined analysis, a slight inverse association between use of aspirin (RR 0.93; 95% CI 0.84-1.02) and non-aspirin NSAIDs (RR 0.94; 95% CI 0.84-1.06) and ovarian cancer risk was found, although it was not statistically significant. However, the risk of invasive ovarian cancer was significantly reduced with use of aspirin (RR 0.88; 95% CI 0.79-0.98). A similar tendency was observed for non-aspirin NSAIDs, but the results were not significant.

CONCLUSIONS

This meta-analysis showed a slight inverse association between NSAIDs and risk of ovarian cancer. However, data suggest that a chemopreventive effect of NSAIDs may be restricted to invasive ovarian tumors. Further research on NSAIDs and ovarian cancer is needed before definite conclusions can be drawn.

Effects of combining Taxol and cyclooxygenase inhibitors on the angiogenesis and apoptosis in human ovarian cancer xenografts

The present study aimed to investigate the combined effects of Taxol and cyclooxygenase (COX) inhibitors on angiogenesis and cell apoptosis of SKOV-3 human ovarian carcinoma cell xenograft-bearing mice. The experiments were continued for 28 days. Animals were treated with 3 mg/kg SC-560 (a COX-1-selective inhibitor) alone, 100 mg/kg celecoxib (a COX-2-selective inhibitor) alone or SC-560/celecoxib by gavage twice a day, 20 mg/kg Taxol alone intraperitoneally once a week or in combination with SC-560 or celecoxib or SC-560/celecoxib/Taxol for three weeks. The mRNA levels of vascular endothelial growth factor (VEGF) was determined by reverse transcription-polymerase chain reaction (RT-PCR). The microvessel density (MVD) of ovarian carcinoma was determined by immunohistochemistry with anti-CD₃₄ as the label. The apoptotic index was detected by the terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labeling (TUNEL) method. The MVD value and apoptotic index in the SC-560/Taxol group were notably inhibited compared with the Taxol group (P<0.001). Moreover, the VEGF mRNA levels, MVD value and apoptotic index in the SC-560/Taxol group were significantly different from the celecoxib/Taxol group (P<0.05, P<0.05 and P<0.001, respectively). The present study demonstrated that SC-560 enhances the anti-angiogenic and pro-apoptotic effects of Taxol and these effects are better than with celecoxib.

Aspirin use, tumor PIK3CA mutation, and colorectal-cancer survival

BACKGROUND

Regular use of aspirin after a diagnosis of colon cancer has been associated with a superior clinical outcome. Experimental evidence suggests that inhibition of prostaglandin-endoperoxide synthase 2 (PTGS2) (also known as cyclooxygenase-2) by aspirin down-regulates phosphatidylinositol 3-kinase (PI3K) signaling activity. We hypothesized that the effect of aspirin on survival and prognosis in patients with cancers characterized by mutated PIK3CA (the phosphatidylinositol-4,5-bisphosphonate 3-kinase, catalytic subunit alpha polypeptide gene) might differ from the effect among those with wild-type PIK3CA cancers.

METHODS

We obtained data on 964 patients with rectal or colon cancer from the Nurses' Health Study and the Health Professionals Follow-up Study, including data on aspirin use after diagnosis and the presence or absence of PIK3CA mutation. We used a Cox proportional-hazards model to compute the multivariate hazard ratio for death. We examined tumor markers, including PTGS2, phosphorylated AKT, KRAS, BRAF, microsatellite instability, CpG island methylator phenotype, and methylation of long interspersed nucleotide element 1.

RESULTS

Among patients with mutated-PIK3CA colorectal cancers, regular use of aspirin after diagnosis was associated with superior colorectal cancer-specific survival (multivariate hazard ratio for cancer-related death, 0.18; 95% confidence interval [CI], 0.06 to 0.61; P<0.001 by the log-rank test) and overall survival (multivariate hazard ratio for death from any cause, 0.54; 95% CI, 0.31 to 0.94; P=0.01 by the log-rank test). In contrast, among patients with wild-type PIK3CA, regular use of aspirin after diagnosis was not associated with colorectal cancer-specific survival (multivariate hazard ratio, 0.96; 95% CI, 0.69 to 1.32; P=0.76 by the log-rank test; P=0.009 for interaction between aspirin and PIK3CA variables) or overall survival (multivariate hazard ratio, 0.94; 95% CI, 0.75 to 1.17; P=0.96 by the log-rank test; P=0.07 for interaction).

CONCLUSIONS

Regular use of aspirin after diagnosis was associated with longer survival among patients with mutated-PIK3CA colorectal cancer, but not among patients with wild-type PIK3CA cancer. The findings from this molecular pathological epidemiology study suggest that the PIK3CA mutation in colorectal cancer may serve as a predictive molecular biomarker for adjuvant aspirin therapy. (Funded by The National Institutes of Health and others.).

Aspirin use, tumor PIK3CA mutation, and colorectal-cancer survival

BACKGROUND

Regular use of aspirin after a diagnosis of colon cancer has been associated with a superior clinical outcome. Experimental evidence suggests that inhibition of prostaglandin-endoperoxide synthase 2 (PTGS2) (also known as cyclooxygenase-2) by aspirin down-regulates phosphatidylinositol 3-kinase (PI3K) signaling activity. We hypothesized that the effect of aspirin on survival and prognosis in patients with cancers characterized by mutated PIK3CA (the phosphatidylinositol-4,5-bisphosphonate 3-kinase, catalytic subunit alpha polypeptide gene) might differ from the effect among those with wild-type PIK3CA cancers.

METHODS

We obtained data on 964 patients with rectal or colon cancer from the Nurses' Health Study and the Health Professionals Follow-up Study, including data on aspirin use after diagnosis and the presence or absence of PIK3CA mutation. We used a Cox proportional-hazards model to compute the multivariate hazard ratio for death. We examined tumor markers, including PTGS2, phosphorylated AKT, KRAS, BRAF, microsatellite instability, CpG island methylator phenotype, and methylation of long interspersed nucleotide element 1.

RESULTS

Among patients with mutated-PIK3CA colorectal cancers, regular use of aspirin after diagnosis was associated with superior colorectal cancer-specific survival (multivariate hazard ratio for cancer-related death, 0.18; 95% confidence interval [CI], 0.06 to 0.61; P<0.001 by the log-rank test) and overall survival (multivariate hazard ratio for death from any cause, 0.54; 95% CI, 0.31 to 0.94; P=0.01 by the log-rank test). In contrast, among patients with wild-type PIK3CA, regular use of aspirin after diagnosis was not associated with colorectal cancer-specific survival (multivariate hazard ratio, 0.96; 95% CI, 0.69 to 1.32; P=0.76 by the log-rank test; P=0.009 for interaction between aspirin and PIK3CA variables) or overall survival (multivariate hazard ratio, 0.94; 95% CI, 0.75 to 1.17; P=0.96 by the log-rank test; P=0.07 for interaction).

CONCLUSIONS

Regular use of aspirin after diagnosis was associated with longer survival among patients with mutated-PIK3CA colorectal cancer, but not among patients with wild-type PIK3CA cancer. The findings from this molecular pathological epidemiology study suggest that the PIK3CA mutation in colorectal cancer may serve as a predictive molecular biomarker for adjuvant aspirin therapy. (Funded by The National Institutes of Health and others.).

Arsenic trioxide synergizes with everolimus (Rad001) to induce cytotoxicity of ovarian cancer cells through increased autophagy and apoptosis

Phosphatidylinositol 3-kinase/AKT/mammalian target of rapamycin pathway plays a key role in the tumorigenesis of a variety of human cancers including ovarian cancer. However, inhibitors of this pathway such as Rad001 have not shown therapeutic efficacy as a single agent for this cancer. Arsenic trioxide (ATO) induces an autophagic pathway in ovarian carcinoma cells. We found that ATO can synergize with Rad001 to induce cytotoxicity of ovarian cancer cells. Moreover, we identified synergistic induction of autophagy and apoptosis as the likely underlying mechanism that is responsible for the enhanced cytotoxicity. The enhanced cytotoxicity is accompanied by decreased p-AKT levels as well as upregulation of ATG5-ATG12 conjugate and LC3-2, hallmarks of autophagy. Rad001 and ATO can also synergistically inhibit tumors in a xenograft animal model of ovarian cancer. These results thus identify and validate a novel mechanism to enhance and expand the existing targeted therapeutic agent to treat human ovarian cancer.

New peptide pENW (pGlu-Asn-Trp) inhibits platelet activation by attenuating Akt phosphorylation

Platelets play a key role in hemostasis and in the initiation and propagation of thrombus formation. New peptide pGlu-Asn-Trp (pENW), initially extracted from snake venom, shows a concentration-dependent antithrombotic activity, significantly attenuated thrombus formation in the arterial and venous vessel systems. This study was designed to further reveal the mechanisms underlying its antithrombotic effect by focusing on its in vitro antiplatelet effect after precluding its influence on coagulation factors. It showed that pENW concentration-dependently inhibited ADP-, collagen- and platelet activating factor (PAF)-induced platelet aggregation, inversely depending upon the intensity of stimulation induced by agonists. Furthermore, data obtained by ELISA and flow cytometry presented that pENW also suppressed ADP-mediated serotonin secretion and P-selectin expression in a concentration-dependent manner. As shown by Western blot assay, ADP-induced platelet Akt phosphorylation was attenuated by the priming incubation with pENW, demonstrating the influence on platelet intracellular signaling. It provided the explaining information for its activity of inhibiting platelet activation in vitro. These results suggested pENW attenuated thrombus formation in part by inhibiting platelet activation instead of coagulation factors, presented evidence of pENW interfering intracellular signaling system in the process of platelet activation and indicated the possibility that pENW could potentially be developed as a novel therapeutic agent in the prevention and treatment of thrombotic disorders.

Synergistic cytotoxic effect of sulindac and pyrrolidine dithiocarbamate against ovarian cancer cells

Sulindac, a non-steroidal anti-inflammatory drug, suppresses carcinogenesis and inhibits growth of tumor cells. Pyrrolidine dithiocarbamate (PDTC), a potent NF-κB inhibitor, has been also identified as a potential anti-neoplastic agent. We hypothesized that combination of sulindac and PDTC could result in augmentation of cytotoxicity against ovarian cancer cells. The effect of sulindac and PDTC was examined on several ovarian cancer lines. Tumor cell viability was assessed using the MTT assay. Annexin-V/PI staining was used to detect apoptosis, cell cycle distribution was analyzed in FACS, and expression of cellular proteins was detected by Western blotting. Incubation of OVA-14, OVP-10 and CAOV-1 ovarian cancer cells with sulindac and PDTC resulted in significantly greater inhibition of cell viability compared to either compound alone. In a model of OVA-14 cells it was evident that this effect was not related to the expression of COX enzymes since both active (sulindac sulfide) and inactive (sulindac) in vitro compounds affected the growth of tumor cells to a similar extent and synergized in cytotoxicity with PDTC. Combination of sulindac and PDTC lead to G0 arrest and massive apoptosis in co-treated cultures. Western blotting analysis argued for induction of the mitochondrial apoptotic pathway. These data demonstrate the synergistic cytotoxic effect of sulindac and PDTC on ovarian cancer cells through apoptosis and cell cycle arrest and prompt to test the efficacy of this combination in animal models.

The role of Pea3 group transcription factors in esophageal squamous cell carcinoma

The transcription factors Pea3, Erm, and Er81 can promote cancer initiation and progression in various types of solid tumors. However, their role in esophageal squamous cell carcinoma (ESCC) has not been elucidated. In this study, we found that the expression levels of Pea3 and Erm, but not that of Er81, were significantly higher in ESCC compared with nontumor esophageal epithelium. A high level of Pea3 expression was significantly correlated with a shorter overall survival in a cohort of 81 patients with ESCC and the subgroup with N1 stage tumor (Wilcoxon-Gehan test, P = 0.016 and P = 0.001, respectively). Pea3 was overexpressed in seven ESCC cell lines compared with two immortalized esophageal cell lines. Pea3 knockdown reduced cell proliferation and suppressed nonadherent growth, migration, and invasion in ESCC cells in vitro. In addition, Pea3 knockdown in ESCC cells resulted in a down-regulation of phospho-Akt and matrix metalloproteinase 13, whereas a significant positive correlation in the expression levels was observed between Pea3 and phospho-Akt (r = 0.281, P < 0.013) and between Pea3 and matrix metalloproteinase 13 in the human specimens (r = 0.462, P < 0.001). Moreover, Pea3 modulated the sensitivity of EC109 cells to doxorubicin, probably via reduced activity of the phosphatidylinositol 3-kinase-Akt-mammalian target of Rapamycin complex 1 pathway on Pea3 knockdown. In conclusion, our results suggest that Pea3 plays an important role in the progression of ESCC.

HGF/c-Met pathway has a prominent role in mediating antiapoptotic signals through AKT in epithelial ovarian carcinoma

The Met receptor tyrosine kinase and its ligand, hepatocyte growth factor (HGF), are overexpressed and/or activated in a variety of human malignancies. However, its role in epithelial ovarian carcinoma (EOC) has not been clearly elucidated. Therefore, we investigated the role of HGF/c-Met signaling pathway in a large series (156) of Saudi EOC patient samples, a panel of cell lines, and xenografts in a NUDE mouse model. Using immunohistochemistry, c-Met overexpression was found in 27.2% Middle Eastern EOC samples and was associated with an advanced tumor stage (P=0.0187). c-Met overexpression was also associated with antiapoptotic markers X-chromosome-linked inhibitors of apoptosis (XIAP) (P=0.0008) and Bcl-XL (P=0.0493) expression. Treatment of EOC cell lines with PHA665752 causes a dose-dependent inhibition of cell viability and induction of apoptosis. Furthermore, PHA665752 treatment causes dephosphorylation of AKT and downregulation of antiapoptotic proteins XIAP and Bcl-XL. In addition, PHA665752-induced apoptosis occurs through activation of Bax-mediated release of cytochrome c and activation of caspases. Finally, co-treatment of EOC with PHA665752 and cisplatin causes augmented effect on apoptosis of EOC cells and resulted in synergistic inhibition of EOC xenograft tumor growth in NUDE mice. These results indicate that c-Met/HGF pathway may be a potential target for therapeutic intervention for treatment of EOC.

Cyclin D1 expression and the inhibitory effect of celecoxib on ovarian tumor growth in vivo

The report aims to investigate the relationship between the expression of cyclin D1 and Cyclooxgenase-2 (COX-2), thus to explore the molecular mechanisms of the antitumor efficacy of Celecoxib, a COX-2 inhibitor. Human ovarian SKOV-3 carcinoma cell xenograft-bearing mice were treated with Celecoxib by infusing gaster (i.g.) twice/day for 21 days. The mRNA levels of COX-2 and cyclin D1 were determined by RT-PCR. The expression of cyclin D1 at the protein level was detected by immunohistochemistry, while COX-2 protein expression was determined by Western blot. A high-dose of Celecoxib (100 mg/kg) significantly inhibited tumor growth (P < 0.05), and the expression of cyclin D1 was reduced by 61%. Celecoxib decreased the proliferation cell index by 40% (P < 0.001) and increased apoptotic index by 52% (P < 0.05) in high-dose Celecoxib treated group. Our results suggest that the antitumor efficacy of Celecoxib against ovarian cancer in mice may in part be mediated through suppression of cyclin D1, which may contribute to its ability to suppress proliferation.

Pooled analysis of the association of PTGS2 rs5275 polymorphism and NSAID use with invasive ovarian carcinoma risk

Inflammation is postulated to play an important role in ovarian carcinogenesis. Prostaglandin endoperoxide synthase 2 (PTGS2) is responsible for the conversion of arachidonic acid to prostaglandins in response to inflammation. In a pooled analysis of two population-based studies, the Hawaii Ovarian Cancer Case-Control Study and the New England Case-Control Study, including 1,025 women with invasive ovarian carcinoma and 1,687 cancer-free controls, the association of ovarian cancer risk with the PTGS2 rs5275 polymorphism and the use of nonsteroidal antiinflammatory drugs (NSAIDs) were examined. Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated using unconditional logistic regression. In the pooled analysis, the CC genotype was associated with a reduced risk of nonserous ovarian carcinoma (OR = 0.66; CI: 0.44-0.98). In addition, the lowest risk was observed among carriers of the CC genotype who were users of only nonaspirin NSAIDs (OR = 0.43; CI:0.20-0.93) in all women combined. The association of PTGS2 rs5275 with nonserous ovarian carcinoma and possible effect modification by NSAID use needs further validation, preferably in prospective studies.

Molecular typing of epithelial ovarian carcinomas using inflammatory markers

BACKGROUND

Ovarian epithelial carcinomas have recently been classified as slow growing type I tumors and rapidly growing highly aggressive type II tumors. The present study sought to molecularly characterize type I and II tumors using known molecular markers.

METHODS

Specimens from 213 patients with ovarian carcinoma were categorized as type I or type II, and evaluated by immunohistochemistry for the inflammatory markers glucose transporter protein-1 (Glut-1), inducible nitric oxide synthase (iNOS), cyclooxygenase-1 (COX-1), cyclooxygenase-2 (COX-2), and nuclear factor kappa B. Statistical analysis was performed to investigate whether these molecular markers could distinguish between type I and type II tumors. Kaplan-Meier survival curves and COX regression analysis were used to determine the prognostic effect of these markers on survival in the 2 types of tumors.

RESULTS

Overexpression of COX-1, COX-2, iNOS, and Glut-1 was significantly higher in type II tumors (P < .05). Women with type II tumors had a poorer median survival (60 months) as compared with those with type I tumors (141 months) (P = .0001). Multivariate analysis revealed type II tumors, late stage, and age >60 years as significant predictors of poor survival. For type II tumors, median survival of patients with tumors overexpressing COX-2 was 44 compared with 85 months for those with tumors with low COX-2 expression (P = .029). Looking at both type I and II tumors, the number of markers simultaneously overexpressed in each tumor was a significant predictor of poor patient survival (P = .005).

CONCLUSIONS

The present study demonstrates that the new proposed histologic classification of ovarian epithelial carcinomas correlates with a distinct expression of inflammatory pathway proteins. High expression of these markers may explain the different biologic behavior of these 2 tumor types and provide targets for therapy.

Nimesulide, a selective cyclooxygenase-2 inhibitor, inhibits the growth of esophageal carcinoma in vivo by modulating PPARγ signal transduction pathway

AIM: To detect the expression of cyclooxygenase-2 (COX-2) and peroxisome proliferator-activated receptor γ (PPARγ) in human esophageal carcinoma, to investigate the inhibitory effects of nimesulide on tumor growth in esophageal carcinoma xenografts in nude mice, and to explore potential mechanisms involved.

METHODS: The expression of PPARγ and COX-2 in 18 normal esophageal epithelial specimens and 59 esophageal squamous cell carcinoma (ESCC) specimens were examined by immunohistochemistry. A nude mouse model bearing Eca-109 cell xenografts was established. The mice were divided randomly into control group and nimesulide group [treated with nimesulide at a dose of 20 mg/(kg•d) for 4 wk]. The tumor volume and reduced rate of tumor growth were calculated according to the length and width of xenograft tumors. Cell apoptosis was detected by flow cytometry. The expression of COX-2 and PPARγ mRNAs and proteins was detected by RT-PCR and immunohistochemistry, respectively.

RESULTS: The immunohistochemical score of PPARγ was significantly lower in ESCC than in normal esophageal epithelium (2.88 ± 2.23 vs 6.29 ± 2.17, P < 0.05), while that of COX-2 was significantly higher in ESCC than in normal esophageal epithelium (2.12 ± 1.77 vs 0.82 ± 0.46, P < 0.05). The immunohistochemical score of PPARγ decreased as tumor pathological grade increased. The immunohistochemical score of PPARγ was closely related to tumor differentiation degree (P < 0.05). The expression level of COX-2 was significantly higher in well and moderately differentiated ESCC than in poorly differentiated ESCC (P < 0.05). Nimesulide significantly inhibited tumor growth in esophageal carcinoma xenografts when compared with the control group (tumor volume: 807.68 mm3 ± 217.76 mm3 vs 2116.77 mm3 ± 362.47 mm3; tumor weight: 0.81 g ± 0.21 g vs 1.45 g ± 0.39 g; both P < 0.05), and the reduced rate of tumor growth was 44.14% ± 6.3%. Nimesulide treatment increased the apoptosis rate from 15.86% ± 2.57% to 32.21% ± 5.98%. COX-2 expression was down-regulated, and PPARγ expression up-regulated in the nimesulide group when compared with the control group. A negative correlation was noted between the expression of COX-2 and PPARγ.

CONCLUSION: Down-regulation of PPARγ expression and up-regulation of COX-2 expression are related to the carcinogenesis of ESCC. Nimesulide inhibits tumor growth and induces apoptosis in esophageal carcinoma xenografts possibly by down-regulating COX-2 expression and up-regulating PPARγ expression.