Synergy between celecoxib and radiotherapy results from inhibition of cyclooxygenase-2-derived prostaglandin E2, a survival factor for tumor and associated vasculature

Effect of radiation fractionation on IDO1 via the NF-κB/COX2 axis in non-small cell lung cancer

Radiotherapy (RT) is the mainstay treatment modality for lung cancer. We recently reported that conventionally fractionated radiotherapy (CRT) with daily fractionation of 2Gy significantly increased the activity of indoleamine 2,3-dioxygenase (IDO1), a known immune checkpoint, which predicted poorer long-term survival in patients with non-small cell lung cancer (NSCLC), while stereotactic body radiotherapy (SBRT) using fractionation size of 10Gy did not increase IDO1 activity and had better survival. Here we hypothesized that the hypofractionated SBRT kind of dose fraction stimulates host antitumor immunity via downregulating IDO1 in which CRT could not. We tested this hypothesis in vitro and in vivo using 10Gyx1 and 2Gyx8 fractionations in the laboratory. The results demonstrated that, although there was an initial downregulation after RT, the expression of IDO1 was ultimately upregulated by both fractionation regimens. The 10Gyx1 regimen had minimum upregulation, while the 2Gyx8 regimen significantly increased in IDO1 expression which was positively correlated with the elevated expressions of p-NF-κB and COX2. Pharmacological inhibition of COX2 abolished RT-induced IDO1 expression. Furthermore, the IDO1 inhibitor, D-1-methyl-tryptophan (D-1MT), exerted RT-related tumor-killing effects in the NSCLC cell lines and mouse models. These findings suggest that, in addition to being an immune suppressor, IDO1 may serve as an adaptive resistance factor in RT. Furthermore, an unappreciated mechanism may exist, where a larger fraction size might be superior to conventional sizes in cancer treatment. This study may provide a rationale for future research in using IDO1 as a biomarker to personalize RT dose fractionation and COX2 inhibitor to decrease radiation immune suppression from CRT.

Anti-inflammatory and analgesic effect of LD-RT and some novel thiadiazole derivatives through COX-2 inhibition

Generally, highly selective COX-2 inhibitors cause cardiovascular side effects. Celecoxib is the highly marketed coxib, so there is still a need for the synthesis of COX-2 inhibitors with less adverse effects. Moreover, low-dose radiotherapy (LD-RT) is clinically used for the treatment of inflammatory diseases. The present study aimed to investigate the analgesic and anti-inflammatory activity of a novel series of 1,3,4-thiadiazole derivatives alone or combined with LD-RT with a single dose of 0.5 Gy. Initially, in vitro COX-1/COX-2 inhibition assays were performed, identifying the sulfonamide-containing compounds 5-10 as the most potent candidates, with IC₅₀ values in the range of 0.32-0.37 µM and the highest selectivity indices. These compounds and celecoxib were subjected to in vivo examination after their safety was assessed through the acute toxicity test. Treatment with compounds 5-10 inhibited carrageenan-induced edema by nearly 47-56%, which was nearly equivalent to celecoxib. Compounds 7 and 8 and celecoxib showed an analgesic activity of 64.15%, 49.05%, and 84.90%, respectively, whereas compounds 5, 6, 9, and 10 did not show any analgesic activity unless combined with LD-RT. Ulcerogenic activity, histological paw examination, and docking studies were performed. Compounds 5-10 were nearly similar to celecoxib, showing normal histological features with no ulcerogenic activity.

Preoperative chemoradiotherapy using S-1 combined with celecoxib for advanced lower rectal cancer: Phase I/II study

OBJECTIVES

To clarify the safety and efficacy of celecoxib combined with chemoradiotherapy using S-1 for lower rectal cancer.

METHODS

Twenty-one patients with pathologically proven lower rectal adenocarcinoma (cT3-T4, Tx N+, M0) were included in this study. A total dose of 45 Gy was administered in daily fractions of 1.8 Gy. Celecoxib was given orally twice daily with S-1 on the day of irradiation. The dose of celecoxib was set at 400 mg/day. In Phase I, the S-1 dose was started at 80 mg/m²/day; in Phase II, S-1 was administered in the same dose as Phase I. Patients underwent surgery six to eight weeks after completing chemoradiotherapy, followed by six months of postoperative adjuvant chemotherapy.

RESULTS

The S-1 recommended dose was 80 mg/m²/day. The pathological complete remission rate was 15.8%, the rate of protocol completion was 14.3%, and the rate of adverse events exceeding Grade 3 was 19.0%. Surgery was performed in 19 cases, with a sphincter-sparing rate of 31.6%. Postoperative complications exceeding Grade 3 occurred in 52.4% of cases. The three year overall survival and relapse-free survival rates were 89.3% and 67.0%, respectively.

CONCLUSIONS

We failed to show a synergistic or additive therapeutic effect of preoperative CRT using S-1, combined with celecoxib, for lower advanced rectal cancer beyond CRT using 5 FU or capecitabine alone. The incidence of complications, evidently involving intestinal ischemia, was relatively high. This treatment strategy is not recommended at present.

Targeting the COX/mPGES-1/PGE2 Pathway in Neuroblastoma

The importance of prostaglandin E₂ in cancer progression is well established, but research on its role in cancer has so far mostly been focused on epithelial cancer in adults while the knowledge about the contribution of prostaglandin E₂ to childhood malignancies is limited. Neuroblastoma, an extracranial solid tumor of the sympathetic nervous system, mainly affects young children. Patients with tumors classified as high-risk have poor survival despite receiving intensive treatment, illustrating a need for new treatments complimenting existing ones. The basis of neuroblastoma treatment e.g. chemotherapy and radiation therapy, target the proliferating genetically unstable tumor cells leading to treatment resistance and relapses. The tumor microenvironment is an avenue, still to a great extent, unexplored and lacking effective targeted therapies. Cancer-associated fibroblasts is the main source of prostaglandin E₂ in neuroblastoma contributing to angiogenesis, immunosuppression and tumor growth. Prostaglandin E₂ is formed from its precursor arachidonic acid in a two-step enzymatic reaction. Arachidonic acid is first converted by cyclooxygenases into prostaglandin H₂ and then further converted by microsomal prostaglandin E synthase-1 into prostaglandin E₂. We believe targeting of microsomal prostaglandin E synthase-1 in cancer-associated fibroblasts will be an effective future therapeutic strategy in fighting neuroblastoma.

Celecoxib Conjugated Fluorescent Probe for Identification and Discrimination of Cyclooxygenase-2 Enzyme in Cancer Cells

Cyclooxygenase-2 (COX-2) is an enzyme overexpressed in most types of cancers and has been used for an excellent targetable biomarker. Celecoxib is an effective inhibitor of COX-2, used in anti-inflammation. Herein we report a one and two-photon fluorescence probe (NP-C6-CXB) for COX-2, based on the conjugation of naphthalamide with Celecoxib, by using flexible hexylene linker. NP-C6-CXB is nonfluorescent in buffer solution and normal cells, while it shows bright fluorescence in solutions and cancer cells in the presence of COX-2 with an excellent selectivity. Interestingly, NP-C6-CXB can discriminate cancer cells (MCF-7) from normal cells (COS-7) in the single culture medium under confocal microscopy. Due to the selective binding affinity of NP-C6-CXB with a COX-2 enzyme, the intensity is proportional to the level of COX-2 enzyme in cancer cells. In vivo and in vitro experiments proved that NP-C6-CXB is a potential tool for identification of tumor and might be used in surgical resection of COX-2 expressed tumors.

Predictive value of APAF-1 and COX-2 expression in pathologic complete response to neoadjuvant chemoradiotherapy for patients with locally advanced rectal adenocarcinoma

Purpose

To investigate predictive value of APAF-1 and COX-2 expression in pathologic complete response (pCR) for patients with rectal adenocarcinoma (RAC) who were treated with neoadjuvant chemoradiotherapy (neo-CRT) followed by total mesorectal excision (TME).

Materials and Methods

Immunohistochemistry assay was used to detect expression of APAF-1 and COX-2 in paraffin-wax embedded tissues obtained before neo-CRT for patients with RAC. A 5-point tumor-regression grade (TRG) based on the ratio of residual tumor to fibrosis according to Dworak's scoring system was used to assess neo-CRT response. The relationship between expression of APAF-1 and COX-2 genes and pCR was explored.

Results

pCR (TRG4) was observed in 23 patients (28.0%). pCR were more likely to be achieved for those with APAF-1 over-expression or lower expression of COX-2. pCR rate in patients with combination of high APAF-1 and low COX-2 expression was 56.0%, significantly higher than those with other combination of APAF1 and COX-2 expression. Multivariate analysis showed that over-expression of APAF-1 and suppressed expression of COX-2 were independent predictive factors for pCR.

Conclusion

Immunohistochemical evaluation of APAF-1 and COX-2 expression on pretreatment specimen may be used to predict pCR to neo-CRT in patients with RAC. The potential of the markers in monitoring pCR patient merits further investigation.

Evaluation of Endoglin (CD105) expression in pediatric rhabdomyosarcoma

BACKGROUND

The Intratumoral Microvessel Density (IMVD) is commonly used to quantify tumoral vascularization and is usually assessed by pan-endothelial markers, such as CD31. Endoglin (CD105) is a protein predominantly expressed in proliferating endothelium and the IMVD determined by this marker measures specifically the neovascularization. In this study, we investigated the CD105 expression in pediatric rhabdomyosarcoma and assessed the neovascularization by using the angiogenic ratio IMVD-CD105 to IMVD-CD31.

METHODS

Paraffin-embedded archival tumor specimens were selected from 65 pediatric patients affected by rhabdomyosarcoma. The expression levels of CD105, CD31 and Vascular Endothelial Growth Factor (VEGF) were investigated in 30 cases (18 embryonal and 12 alveolar) available for this study. The IMVD-CD105 to IMVD-CD31 expression ratio was correlated with clinical and pathologic features of these patients.

RESULTS

We found a specific expression of endoglin (CD105) in endothelial cells of all the rhabdomyosarcoma specimens analyzed. We observed a significant positive correlation between the IMVD individually measured by CD105 and CD31. The CD105/CD31 expression ratio was significantly higher in patients with lower survival and embryonal histology. Indeed, patients with a CD105/CD31 expression ratio < 1.3 had a significantly increased OS (88%, 95%CI, 60%-97%) compared to patients with higher values (40%, 95%CI, 12%-67%). We did not find any statistical correlation among VEGF and EFS, OS and CD105/CD31 expression ratio.

CONCLUSION

CD105 is expressed on endothelial cells of rhabdomyosarcoma and represent a useful tool to quantify neovascularization in this tumor. If confirmed by further studies, these results will indicate that CD105 is a potential target for combined therapies in rhabdomyosarcoma.

Neoadjuvant irinotecan, cisplatin, and concurrent radiation therapy with celecoxib for patients with locally advanced esophageal cancer

Background

Patients with locally advanced esophageal cancer who are treated with trimodality therapy have a high recurrence rate. Preclinical evidence suggests that inhibition of cyclooxygenase 2 (COX2) increases the effectiveness of chemoradiation, and observational studies in humans suggest that COX-2 inhibition may reduce esophageal cancer risk. This trial tested the safety and efficacy of combining a COX2 inhibitor, celecoxib, with neoadjuvant irinotecan/cisplatin chemoradiation.

Methods

This single arm phase 2 trial combined irinotecan, cisplatin, and celecoxib with concurrent radiation therapy. Patients with stage IIA-IVA esophageal cancer received weekly cisplatin 30 mg/m² plus irinotecan 65 mg/m² on weeks 1, 2, 4, and 5 concurrently with 5040 cGy of radiation therapy. Celecoxib 400 mg was taken orally twice daily during chemoradiation, up to 1 week before surgery, and for 6 months following surgery.

Results

Forty patients were enrolled with stage IIa (30 %), stage IIb (20 %), stage III (22.5 %), and stage IVA (27.5 %) esophageal or gastroesophageal junction cancer (AJCC, 5th Edition). During chemoradiation, grade 3–4 treatment-related toxicity included dysphagia (20 %), anorexia (17.5 %), dehydration (17.5 %), nausea (15 %), neutropenia (12.5 %), diarrhea (10 %), fatigue (7.5 %), and febrile neutropenia (7.5 %). The pathological complete response rate was 32.5 %. The median progression free survival was 15.7 months and the median overall survival was 34.7 months. 15 % (n = 6) of patients treated on this study developed brain metastases.

Conclusions

The addition of celecoxib to neoadjuvant cisplatin-irinotecan chemoradiation was tolerable; however, overall survival appeared comparable to prior studies using neoadjuvant cisplatin-irinotecan chemoradiation alone. Further studies adding celecoxib to neoadjuvant chemoradiation in esophageal cancer are not warranted.

Trial registration

Clinicaltrials.gov: NCT00137852, registered August 29, 2005.

Advances in Magnetic Resonance Imaging Contrast Agents for Biomarker Detection

Recent advances in magnetic resonance imaging (MRI) contrast agents have provided new capabilities for biomarker detection through molecular imaging. MRI contrast agents based on the T2 exchange mechanism have more recently expanded the armamentarium of agents for molecular imaging. Compared with T1 and T2* agents, T2 exchange agents have a slower chemical exchange rate, which improves the ability to design these MRI contrast agents with greater specificity for detecting the intended biomarker. MRI contrast agents that are detected through chemical exchange saturation transfer (CEST) have even slower chemical exchange rates. Another emerging class of MRI contrast agents uses hyperpolarized (13)C to detect the agent with outstanding sensitivity. These hyperpolarized (13)C agents can be used to track metabolism and monitor characteristics of the tissue microenvironment. Together, these various MRI contrast agents provide excellent opportunities to develop molecular imaging for biomarker detection.

Development of Antioxidant COX-2 Inhibitors as Radioprotective Agents for Radiation Therapy-A Hypothesis-Driven Review

Radiation therapy (RT) evolved to be a primary treatment modality for cancer patients. Unfortunately, the cure or relief of symptoms is still accompanied by radiation-induced side effects with severe acute and late pathophysiological consequences. Inhibitors of cyclooxygenase-2 (COX-2) are potentially useful in this regard because radioprotection of normal tissue and/or radiosensitizing effects on tumor tissue have been described for several compounds of this structurally diverse class. This review aims to substantiate the hypothesis that antioxidant COX-2 inhibitors are promising radioprotectants because of intercepting radiation-induced oxidative stress and inflammation in normal tissue, especially the vascular system. For this, literature reporting on COX inhibitors exerting radioprotective and/or radiosensitizing action as well as on antioxidant COX inhibitors will be reviewed comprehensively with the aim to find cross-points of both and, by that, stimulate further research in the field of radioprotective agents.

Repurposing Drugs in Oncology (ReDO)-diclofenac as an anti-cancer agent

Diclofenac (DCF) is a well-known and widely used non-steroidal anti-inflammatory drug (NSAID), with a range of actions which are of interest in an oncological context. While there has long been an interest in the use of NSAIDs in chemoprevention, there is now emerging evidence that such drugs may have activity in a treatment setting. DCF, which is a potent inhibitor of COX-2 and prostaglandin E2 synthesis, displays a range of effects on the immune system, the angiogenic cascade, chemo- and radio-sensitivity and tumour metabolism. Both pre-clinical and clinical evidence of these effects, in multiple cancer types, is assessed and summarised and relevant mechanisms of action outlined. Based on this evidence the case is made for further clinical investigation of the anticancer effects of DCF, particularly in combination with other agents - with a range of possible multi-drug and multi-modality combinations outlined in the supplementary materials accompanying the main paper.

Drug repositioning for gynecologic tumors: a new therapeutic strategy for cancer

The goals of drug repositioning are to find a new pharmacological effect of a drug for which human safety and pharmacokinetics are established and to expand the therapeutic range of the drug to another disease. Such drug discovery can be performed at low cost and in the short term based on the results of previous clinical trials. New drugs for gynecologic tumors may be found by drug repositioning. For example, PPAR ligands may be effective against ovarian cancer, since PPAR activation eliminates COX-2 expression, arrests the cell cycle, and induces apoptosis. Metformin, an antidiabetic drug, is effective for endometrial cancer through inhibition of the PI3K-Akt-mTOR pathway by activating LKB1-AMPK and reduction of insulin and insulin-like growth factor-1 due to AMPK activation. COX-2 inhibitors for cervical cancer may also be examples of drug repositioning. PGE2 is induced in the arachidonate cascade by COX-2. PGE2 maintains high expression of COX-2 and induces angiogenic factors including VEGF and bFGF, causing carcinogenesis. COX-2 inhibitors suppress these actions and inhibit carcinogenesis. Combination therapy using drugs found by drug repositioning and current anticancer drugs may increase efficacy and reduce adverse drug reactions. Thus, drug repositioning may become a key approach for gynecologic cancer in drug discovery.

Optical imaging of COX-2: studies on an autofluorescent 2,3-diaryl-substituted indole-based cyclooxygenase-2 inhibitor

This study aimed at in vivo visualization of cyclooxygenase-2 (COX-2) by optical imaging using a representative compound of a class of autofluorescent 2,3-diaryl-substituted indole-based selective COX-2 inhibitors (2,3-diaryl-indole coxibs). COX-2 was successfully visualized in mice models with phorbol myristate ester (TPA)-induced inflammation or bearing xenografted human melanoma cells by 2-[4-(aminosulfonyl)phenyl]-3-(4-methoxyphenyl)-1H-indole (C1). COX-2 protein expression in both TPA-induced inflammatory sites and human melanoma xenografts was confirmed by immunoblotting. Control experiments using surrogate markers, sham injections, and non-COX-2 expressing melanoma cells further confirmed specificity of tissue association of C1. The merging of therapeutic and diagnostic properties of 2,3-diaryl-indole coxibs may widen the range of applications of COX-2-targeted treatment, e.g., for in situ-guided surgery and ex vivo diagnostics.

COX-2 overexpression and -8473 T/C polymorphism in 3' UTR in non-small cell lung cancer

A new class of compounds targeting cyclooxygenase 2 (COX-2) together with other different clinically used therapeutic strategies has recently shown a promise for the chemoprevention of several solid tumors including lung cancer. The aim was to study the possible role of COX-2 -8473 T/C NP and its expression in the pathogenesis of non-small cell lung cancer. One hundred ninety non-small cell lung cancer (NSCLC) patients and 200 healthy age-, sex-, and smoking-matched controls were used for polymorphic analysis, and 48 histopathologically confirmed NSCLC patients were analyzed for COX-2 messenger RNA (mRNA) and protein expression. Our results showed that the frequencies of variant genotypes 8473 CT/CC were significantly less common in the cases (30.0%) than in the controls (36%), suggesting that the 8473 C variant allele is related with lower susceptibility in NSCLC (OR = 0.79, 95% CI 0.54-1.4). However, the frequency of COX-2 -8473 TC and CC genotypes were significantly associated with age in NSCLC (P = 0.02). Quantitative real-time expression analysis showed a significant increase in the COX-2 mRNA in tumor tissues as compared to their adjacent normal tissues [delta cycle threshold (ΔCT) = 9.25 ± 4.67 vs 5.63 ± 3.85, P = 0.0001]. Multivariate logistic regression analyses revealed that the COX-2 expression was associated significantly with age (P = 0.044). Also, an increasing trend was observed in stages I and II and in female patients compared to stages III and IV and male patients, respectively, but no statistical significance was observed. However, COX-2 mRNA expression shown no association with the -8473 C variant allele. Our findings indicate that the COX-2 T8473C polymorphism may contribute to NSCLC cancer susceptibility in the Kashmiri population, while our expression analysis revealed a significant increase of COX-2 in tumor tissues as compared to their adjacent normal tissues, suggesting that it could become an important therapeutic marker in NSCLC in the future.

Emerging opportunities for the combination of molecularly targeted drugs with radiotherapy

Recent drug discovery developments in the field of small molecule targeted agents have led to much interest in combining these with radiotherapy. There are good preclinical data to suggest this approach worthy of investigation and in this review we discuss how this has translated into recent clinical trials. The outcome of clinical trials investigating radiotherapy/targeted drug combinations published in the last 5 years is discussed, as are trials in progress. The perceived future opportunities and challenges in the development of this exciting area are considered.

A COX-2 inhibitor enhances the antitumor effects of chemotherapy and radiotherapy for esophageal squamous cell carcinoma

Cyclooxygenase-2 (COX-2) is a key enzyme of prostaglandin (PG) synthesis that has been demonstrated to be overexpressed in several types of cancers. The function of COX-2 in tumor progression has been recently elucidated. In tumors in which COX-2 is overexpressed, the antitumor effects are suppressed. We examined the effects of celecoxib, a COX-2 inhibitor, in enhancing the antitumor effects of chemotherapy and radiotherapy for esophageal squamous cell carcinoma (ESCC) by reducing the COX-2 activity. We used the human esophageal squamous cell lines TE2 and T.Tn treated with celecoxib and 5-FU/radiation, after which cell viability assays were performed. Changes in the expressions of dihydropyrimidine dehydrogenase (DPD), orotate phosphoribosyl transferase (OPRT) mRNA and PGE2 were also measured. In addition, apoptotic changes, and the invasion and migration activity in both the celecoxib and 5-FU treated cells were evaluated. The experiments showed that T.Tn and TE2 proliferation was strongly inhibited by the combination of 5-FU/radiation and the COX-2 inhibitor. Inhibiting the COX-2 activity induced a reduction in PGE2 levels in TE2/T.Tn cells. Following treatment with the COX-2 inhibitor and 5-FU, the OPRT expression was upregulated and the DPD expression was downregulated in the resistant cells. In addition, the combination treatment with the COX-2 inhibitor and 5-FU markedly inhibited both the cell invasion and migration activity. Therefore, COX-2 inhibitors can be useful enhancers of antitumor drugs and radiotherapy for ESCC.

Imaging biomarkers to monitor response to the hypoxia-activated prodrug TH-302 in the MiaPaCa2 flank xenograft model

TH-302, a hypoxia-activated anticancer prodrug, was evaluated for antitumor activity and changes in dynamic contrast-enhanced (DCE) and diffusion-weighted (DW) magnetic resonance imaging (MRI) in a mouse model of pancreatic cancer. TH-302 monotherapy resulted in a significant delay in tumor growth compared to vehicle-treated controls. TH-302 treatment was also associated with a significant decrease in the volume transfer constant (K(trans)) compared to vehicle-treated controls 1 day following the first dose measured using DCE-MRI. This early decrease in K(trans) following the first dose as measured is consistent with selective killing of the hypoxic fraction of cells which are associated with enhanced expression of hypoxia inducible transcription factor-1 alpha that regulates expression of permeability and perfusion factors including vascular endothelial growth factor-A. No changes were observed in DW-MRI following treatment with TH-302, which may indicate that this technique is not sensitive enough to detect changes in small hypoxic fractions of the tumor targeted by TH-302. These results suggest that changes in tumor permeability and/or perfusion may be an early imaging biomarker for response to TH-302 therapy.

Tumour response prediction by diffusion-weighted MR imaging: ready for clinical use?

BACKGROUND

The efficacy of anticancer therapy is usually evaluated by anatomical imaging. However, this method may be suboptimal for the evaluation of novel treatment modalities, such as targeted therapy. Theoretically, functional assessment of tumour response by diffusion weighted imaging (DWI) is an attractive tool for this purpose and may allow an early prediction of response. The optimal use of this method has still to be determined.

METHOD

We reviewed the published literature on clinical DWI in the prediction of response to anticancer therapy, especially targeted therapy. Studies investigating the role of DWI in patients with cancer either for response prediction and/or response monitoring were selected for this analysis.

RESULTS

We identified 24 studies that met our criteria. Most studies showed a significant correlation between (changes in) apparent diffusion coefficient (ADC) values and treatment response. However, in different tumours and studies, both high and low pretreatment ADC were found to be associated with response rate. In the course of treatment, an increase in ADC was associated with response in most cases.

CONCLUSION

The potential of DWI for (early) response monitoring of anticancer therapies has been demonstrated. However, validation is hampered by the lack of reproducibility and standardisation. We recommend that these issues should be properly addressed prior to further testing the clinical use of DWI in the assessment of treatments.

COX-derived prostanoid pathways in gastrointestinal cancer development and progression: novel targets for prevention and intervention

Arachidonic acid metabolism through cyclooxygenase (COX) pathways leads to the generation of biologically active eicosanoids. Eicosanoid expression levels vary during development and progression of gastrointestinal (GI) malignancies. COX-2 is the major COX-isoform responsible for G.I. cancer development/progression. COX-2 expression increases during progression from a normal to cancerous state. Evidence from observational studies has demonstrated that chronic NSAID use reduces the risk of cancer development, while both incidence and risk of death due to G.I. cancers were significantly reduced by daily aspirin intake. A number of randomized controlled trials (APC trial, Prevention of Sporadic Adenomatous Polyps trial, APPROVe trial) have also shown a significant protective effect in patients receiving selective COX-2 inhibitors. However, chronic use of selective COX-2 inhibitors at high doses was associated with increased cardiovascular risk, while NSAIDs have also been associated with increased risk. More recently, downstream effectors of COX-signaling have been investigated in cancer development/progression. PGE(2), which binds to both EP and PPAR receptors, is the major prostanoid implicated in the carcinogenesis of G.I. cancers. The role of TXA(2) in G.I. cancers has also been examined, although further studies are required to uncover its role in carcinogenesis. Other prostanoids investigated include PGD(2) and its metabolite 15d-PGJ2, PGF(1α) and PGI(2). Targeting these prostanoids in G.I. cancers has the promise of avoiding cardiovascular toxicity associated with chronic selective COX-2 inhibition, while maintaining anti-tumor reactivity. A progressive sequence from normal to pre-malignant to a malignant state has been identified in G.I. cancers. In this review, we will discuss the role of the COX-derived prostanoids in G.I. cancer development and progression. Targeting these downstream prostanoids for chemoprevention and/or treatment of G.I. cancers will also be discussed. Finally, we will highlight the latest pre-clinical technologies as well as avenues for future investigation in this highly topical research field.

Pretreatment CD133 and cyclooxygenase-2 expression as the predictive markers of the pathological effect of chemoradiotherapy in rectal cancer patients

BACKGROUND

CD133 confers chemoradioresistance properties to cells and has recently been used to identify cancer-initiating cells.

OBJECTIVE

We investigated whether the overexpression of CD133 and cyclooxygenase-2 can be used as predictive markers of tumor response to preoperative chemoradiotherapy in patients with rectal cancer.

SETTING

The study was conducted at the National Defense Medical College Hospital in Japan.

PATIENTS

We recruited 96 patients who underwent a single regimen of preoperative short-term chemoradiotherapy (20 Gy in 5 fractions with 400 mg/day Tegafur/Uracil for 1 week) and radical resection.

DESIGN

This was a retrospective study. We obtained pretreatment biopsy specimens of these patients and immunostained these specimens with antibodies for CD133, cyclooxygenase-2, p53, p27, p21, and epidermal growth factor receptor. The resected primary tumor was evaluated according to 2 different tumor regression grading systems that were based on the degrees of fibrosis and cytological alterations.

RESULTS

Positivity for CD133 or cyclooxygenase-2 expression was associated with chemoradioresistance, which was determined by the degree of fibrosis, in both univariate (P = .02 and P = .0003) and multivariate (P = .03 and P = .001) analyses. Univariate and multivariate analyses of the degree of cytological alterations also revealed a significant association between chemoradioresistance and the expression of CD133 (P = .005 and P = .003) and cyclooxygenase-2 (P = .005 and P = .03), whereas other markers failed to associate.

LIMITATIONS

The information on patients' outcome was not available.

CONCLUSIONS

Our study revealed the independent predictive values of CD133 and cyclooxygenase-2 expressions in histological tumor regression after preoperative chemoradiotherapy.

Effects of phytochemicals on ionization radiation-mediated carcinogenesis and cancer therapy

Ionizing radiation (IR)-induced cellular damage is implicated in carcinogenesis as well as therapy of cancer. Advances in radiation therapy have led to the decrease in dosage and localizing the effects to the tumor; however, the development of radioresistance in cancer cells and radiation toxicity to normal tissues are still the major concerns. The development of radioresistance involves several mechanisms, including the activation of mitogenic and survival signaling, induction of DNA repair, and changes in redox signaling and epigenetic regulation. The current strategy of combining radiation with standard cytotoxic chemotherapeutic agents can potentially lead to unwanted side effects due to both agents. Thus agents are needed that could improve the efficacy of radiation killing of cancer cells and prevent the damage to normal cells and tissues caused by the direct and bystander effects of radiation, without have its own systemic toxicity. Chemopreventive phytochemicals, usually non-toxic agents with both cancer preventive and therapeutic activities, could rightly fit in this approach. In this regard, naturally occurring compounds, including curcumin, parthenolide, genistein, gossypol, ellagic acid, withaferin, plumbagin and resveratrol, have shown considerable potential. These agents suppress the radiation-induced activation of receptor tyrosine kinases and nuclear factor-κB signaling, can modify cell survival and DNA repair efficacy, and may potentiate ceramide signaling. These radiosensitizing and counter radioresistance mechanisms of phytochemicals in cancer cells are also associated with changes in epigenetic gene regulation. Because radioresistance involves multiple mechanisms, more studies are needed to discover novel phytochemicals having multiple mechanisms of radiosensitization and to overcome radioresistance of cancer cells. Pre-clinical studies are needed to address the appropriate dosage, timing, and duration of the application of phytochemicals with radiation to justify clinical trials. Nonetheless, some phytochemicals in combination with IR may play a significant role in enhancing the therapeutic index of cancer treatment.

Plasma levels of vascular endothelial growth factor during and after radiotherapy in combination with celecoxib in patients with advanced head and neck cancer

Celebrex and radiotherapy in advanced head and neck cancer. This phase I dose-escalation study seeks to determine the phase II recommended dose of cyclooxygenase type 2 (COX-2) inhibitor in patients with locally advanced squamous cell head and neck (H&N) cancer, treated with accelerated radiotherapy. Anti-vasculogenic effect of this treatment on serum vascular endothelial growth factor (VEGF) is examined. Patients were irradiated with curative intent (72Gy in 6weeks). Celecoxib was administered throughout the radiotherapy course. Serum VEGF level were tested during radiotherapy and in follow-up. Tumor specimens were stained to quantify the COX-2 expression. Thirty-two patients completed the treatment. The dose of celecoxib was escalated (200, 400 and 800mg bid, then de-escalated to 600mg bid). The acute toxicity related to the treatment in the first and second cohort did not reach grade III; in the third cohort three patients had grade III radiation toxicity and one had celecoxib-related toxicity. In the last fourth cohort the toxicity was acceptable. Significant VEGF level drop (p=0.011) was found between radiation day 1 and post-treatment visit. Significant decrease (p=0.022) of the VEGF level was shown in patients with high COX-2 expression in the tumor. Phase II recommended dose of celecoxib combined with accelerated radiotherapy in advanced H&N cancer was 600mg bid. A significant decrease of the post-treatment serum VEGF level compared to the initial level was noticed only in patients with high COX-2 expression in tumors.

HT-29 colorectal cancer cells undergoing apoptosis overexpress COX-2 to delay ursolic acid-induced cell death

Colorectal cancer is one of the most common cancer types and the third leading cause of cancer-related death in the western world. Generally, colorectal cancers are resistant to anticancer drugs. Several lines of evidence support a critical role for cyclooxygenase-2 (COX-2) during colorectal tumorigenesis and its role in chemoresistance. In this study, we focused our interest on the role played by COX-2 in apoptosis induced in HT-29 human colorectal cancer cells by ursolic acid (UA), a triterpenoid found in a large variety of plants. We showed that UA-induced apoptosis and that COX-2 was overexpressed only in apoptotic cells. We demonstrated that this overexpression was mediated by the p38 MAP kinase pathway as inhibiting its activation using a p38-specific inhibitor, SB 203580, abrogated COX-2 expression. Inhibiting COX-2 expression either by using a p38-specific inhibitor or COX-2-specific siRNA increased apoptosis. These results demonstrated that COX-2 was involved in a resistance mechanism to UA-induced apoptosis in HT-29 cells. Cells undergoing apoptosis were able to trigger a resistance mechanism by overexpressing a protein such as COX-2 to delay their death. Furthermore, we demonstrated that this resistance mechanism was independent of PGE(2) production as the addition of the specific COX-2 activity inhibitor, NS-398, did not affect apoptosis in UA-treated cells.

Targeting apoptosis pathways by Celecoxib in cancer

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

Combined Inhibition of Epidermal Growth Factor Receptor and Cyclooxygenase-2 as a Novel Approach to Enhance Radiotherapy

Targeting epidermal growth factor receptor (EGFR) is a promising approach to increasing radiosensitivity of head and neck cancers but treatment resistance remains an important clinical problem. We hypothesize that combined EGFR and cyclooxygenase-2 (COX-2) inhibition, using small molecule inhibitors erlotinib and celecoxib, respectively would further increase the antitumor activity of radiotherapy. The effects of combinations of celecoxib, erlotinib and ionizing radiation (IR) on cell growth, cell cycle progression and apoptosis of head and neck cancer cell lines were assessed in vitro by cell viability, clonogenic survival, flow cytometry and Annexin V assays and in vivo. The effects of celecoxib, erlotinib and IR on primary and downstream molecular targets were analyzed by immunoblotting & ELISA assays. Compared to single or double agent approaches, concurrent celecoxib, erlotinib and IR was the most effective regimen at reducing clonogenic survival, increasing apoptosis and inhibiting tumor growth in vivo. Concurrent treatment with celecoxib and erlotinib ± IR inhibited multiple prosurvival proteins including p-ERK1/2, p-EGFR, p-AKT, p-STAT3, COX-2 and PGE-2. The combination of celecoxib, erlotinib and IR is a promising strategy to overcoming resistance to combined EGFR inhibition and IR alone.

Celecoxib enhances radiation response of secondary bone tumors of a human non-small cell lung cancer via antiangiogenesis in vivo

PURPOSE

Cyclooxygenase-2 (COX-2) inhibitors mediate a systemic antitumor activity via antiangiogenesis and seem to enhance the response of primary tumors to radiation. Radiosensitizing effects of COX-2 inhibition have not been reported for bone metastases. Therefore, the aim of this study was the investigation of the radiosensitizing effects of the selective COX-2 inhibitor celecoxib in secondary bone tumors of a non-small cell lung carcinoma in vivo.

MATERIALS AND METHODS

Human A549 lung carcinomas were implanted into a cranial window preparation in male SCID mice (n = 24). Animals were treated with either celecoxib or radiation (7 Gy single photon dose) alone or a combination of celecoxib and radiation, respectively. Untreated animals served as controls. The impact of radiation and COX-2 inhibition on angiogenesis, microcirculation, and tumor growth was analyzed over 28 days by means of intravital microscopy and histological methods.

RESULTS

Monotherapies with radiation as well as celecoxib had significant antitumor effects compared to untreated controls. Both therapies reduced tumor growth and vascularization to a similar extent. The simultaneous administration of celecoxib and radiation further enhanced the antitumor and antiangiogenic effects of single-beam radiation. With the combined treatment approach, tumor vascularization and tumor size were decreased by 57% and 51%, respectively, as compared to monotherapy with radiation.

CONCLUSION

The combined application of radiation therapy and COX-2 inhibition showed synergistic effects concerning the inhibition of tumor growth and tumor angiogenesis. Therefore, the combination of radiation with COX-2 inhibitor therapy represents a promising approach to improve the therapeutic efficacy of radiotherapy of bone metastases.

Expression of cyclooxygenase-2 (COX-2) in an advanced metastasized hypopharyngeal carcinoma and cultured tumor cells

PURPOSE

The inducible enzyme cyclooxygenase-2 (COX-2) catalyzes PGE(2) production and plays an important role in the progression of many solid cancers. However, the role of COX-2 expression in cervical lymph node metastases of head and neck cancer has not been clarified yet.

PATIENT AND METHODS

We comment on a male patient aged 53 who was admitted to an ENT-department with acute bleeding from an advanced hypopharyngeal carcinoma and a frontotemporal mass. Prior to palliative intended radiotherapy, the metastasis was resected. During the procedure, a small amount of tumor tissue was harvested for primary tumor cell culture.

RESULTS

COX-2 overexpression was demonstrated in the primary tumor tissue, the metastasis, in the cultured tumor cells by standard immunohistochemistry, as well as cytochemistry.

CONCLUSIONS

A simultaneous expression of COX-2 in head and neck carcinoma was presented for the first time. Besides the prognostic impact in oral carcinogenesis, this COX-2 role of biomarker for aggressive head and neck squamous cell carcinomas should be further evaluated. Additionally, treatment of hypopharyngeal carcinomas with selective COX-2 inhibitors could be beneficial when administered in combination with radiochemotherapy.

The role of COX-2 in intestinal inflammation and colorectal cancer

Colorectal cancer (CRC) is a heterogeneous disease, including at least three major forms: hereditary, sporadic and colitis-associated CRC. A large body of evidence indicates that genetic mutations, epigenetic changes, chronic inflammation, diet and lifestyle are the risk factors for CRC. As elevated cyclooxygenase-2 (COX-2) expression was found in most CRC tissue and is associated with worse survival among CRC patients, investigators have sought to evaluate the effects of nonsteroidal anti-inflammatory drugs (NSAIDs) and selective COX-2 inhibitors (COXIBs) on CRC. The epidemiological studies, clinical trials and animal experiments indicate that NSAIDs are among the most promising chemopreventive agents for this disease. NSAIDs exert their anti-inflammatory and antitumor effects primarily by reducing prostaglandin production by inhibition of COX-2 activity. In this review, we highlight breakthroughs in our understanding of the roles of COX-2 in CRC and inflammatory bowel disease. These recent data provide a rationale for re-evaluating COX-2 as both the prognostic and the predictive marker in a wide variety of malignancies and for renewing the interest in evaluating relative benefits and risk of COXIBs in appropriately selected patients for cancer prevention and treatment.

Curcumin: a potential radio-enhancer in head and neck cancer

OBJECTIVES/HYPOTHESIS

To investigate whether curcumin enhances the cytotoxic effect of radiotherapy in head and neck squamous cell carcinoma (HNSCC).

METHODS

HNSCC cell lines SCC-1, SCC-9, KB, as well as A431 cell line were treated with curcumin, irradiation, or their combination. Cell viability was evaluated by XTT assay. Cyclooxygenase-2 (COX-2), epithelial growth factor receptor (EGFR), and p-Erk1/2 were measured by Western blot analysis. CD-1 athymic nude mice with orthotopic implanted SCC-1 cells, were treated with control diet, curcumin containing diet, local single-dose radiation, or combination.

RESULTS

Curcumin (IC50 range, 15-22 microM) and radiation inhibited cell viability in all cell lines were tested. The combination of curcumin and radiation resulted in additive effect. Curcumin decreased COX-2 expression and inhibited phosphorylation of EGFR in SCC-1 cells. In tumor-bearing mice the combination regimen showed a decrease in both tumor weight (25%, P = .09) and tumor size (15%, P = .23) compared to the nontreated mice.

CONCLUSIONS

: Curcumin inhibited HNSCC cell growth and augmented the effect of radiation in vitro and in vivo. A possible mechanism is inhibition of COX-2 expression and EGFR phosphorylation.

Double blind randomized phase II study with radiation+5-fluorouracil+/-celecoxib for resectable rectal cancer

PURPOSE

To assess the feasibility and efficacy of the COX-2 inhibitor celecoxib in conjunction with preoperative chemoradiation for patients with locally advanced rectal cancer in a double blind randomized phase II study.

MATERIALS AND METHODS

Thirty-five patients of the initially planned 80 patients with locally advanced rectal cancer were treated with preoperative radiation (45 Gy; 1.8 Gy/fraction, 5 days/week) combined with 5-fluorouracil (continuous infusion, 225 mg/m(2)/day) and celecoxib (2 x 400 mg/day) or placebo. Pathological response and toxicity of study treatment were evaluated, as well as expression of COX-2 and Ki67 in tumor tissue and IL-6 in plasma as possible molecular correlates and predictors of response to treatment.

RESULTS

Patients treated with celecoxib tended to show a better response (61%) when compared to those treated with placebo (35%), although not significant (p=0.13). T-downstaging and N-downstaging were also slightly higher with celecoxib. Plasma IL-6 levels and intratumoral COX2 or Ki67 were altered by chemoradiation, but were not further altered by celecoxib treatment and therefore not useful for prediction of treatment benefit. Celecoxib therapy in conjunction with chemoradiation was not associated with additional toxicity and seemed to help mitigate therapy-related pain.

CONCLUSIONS

Addition of celecoxib to preoperative chemoradiation is feasible for patients with locally advanced rectal cancer. To study the individual effect of COX-2 inhibitors on pathological response phase III studies are required.

Combined action of celecoxib and ionizing radiation in prostate cancer cells is independent of pro-apoptotic Bax

BACKGROUND AND PURPOSE

The cyclooxygenase-2-inhibitor celecoxib has been shown to inhibit cell growth and to reduce prostatic intraepithelial neoplasia in mice. The drug was suggested to increase efficacy of ionizing radiation. However, extent and mechanisms of the suggested benefit of celecoxib on the radiation response are still unclear. The aim of the present study was to analyze cytotoxic efficacy of celecoxib in combination with irradiation on human prostate cancer cell lines and to define the importance of pro-apoptotic Bax in this process.

MATERIALS AND METHODS

Induction of apoptosis and global and clonogenic cell survival upon irradation- (2-10Gy), celecoxib- (10-75microM) or combined treatment were evaluated in prostate cancer cells by fluorescence microscopy, WST-1 assay and standard colony formation assays.

RESULTS

Celecoxib <25microM caused morphological changes and growth inhibition without substantial apoptosis or radiosensitization in terms of decreased clonogenic cell survival. In contrast, celecoxib 25microM increased radiation-induced cell death and clonogenic kill. While radiation-induced clonogenic death was increased in the presence of Bax, effects of celecoxib or combined treatment were Bax independent.

CONCLUSIONS

Our findings reveal Bax-independent beneficial effects of celecoxib on radiation-induced apoptosis and eradication of clonogenic prostate cancer cells in vitro providing a rationale for clinical evaluation of high-dose celecoxib in combination with irradiation in prostate cancer patients.

DNA-PKcs-dependent modulation of cellular radiosensitivity by a selective cyclooxygenase-2 inhibitor

PURPOSE

Inhibition of cyclooxygenase-2 has been shown to increase radiosensitivity. Recently, the suppression of radiation-induced DNA-dependant protein kinase (DNA-PK) activity by the selective cyclooxygenase-2 inhibitor celecoxib was reported. Given the importance of DNA-PK for repair of radiation-induced DNA double-strand breaks by nonhomologous end-joining and the clinical use of the substance, we investigated the relevance of the DNA-PK catalytic subunit (DNA-PKcs) for the modulation of cellular radiosensitivity by celecoxib.

METHODS AND MATERIALS

We used a syngeneic model of Chinese hamster ovarian cell lines: AA8, possessing a wild-type DNK-PKcs; V3, lacking a functional DNA-PKcs; and V3/WT11, V3 stably transfected with the DNA-PKcs. The cells were treated with celecoxib (50 muM) for 24 h before irradiation. The modulation of radiosensitivity was determined using the colony formation assay.

RESULTS

Treatment with celecoxib increased the cellular radiosensitivity in the DNA-PKcs-deficient cell line V3 with a dose-enhancement ratio of 1.3 for a surviving fraction of 0.5. In contrast, clonogenic survival was increased in DNA-PKcs wild-type-expressing AA8 cells and in V3 cells transfected with DNA-PKcs (V3/WT11). The decrease in radiosensitivity was comparable to the radiosensitization in V3 cells, with a dose-enhancement ratio of 0.76 (AA8) and 0.80 (V3/WT11) for a survival of 0.5.

CONCLUSIONS

We have demonstrated a DNA-PKcs-dependent differential modulation of cellular radiosensitivity by celecoxib. These effects might be attributed to alterations in signaling cascades downstream of DNA-PK toward cell survival. These findings offer an explanation for the poor outcomes in some recently published clinical trials.

Cyclooxygenase in the treatment of glioma: its complex role in signal transduction

BACKGROUND

High-grade glioma remains one of the most difficult cancers to treat. Recent studies in oncology have identified a role of the ubiquitous enzyme, cyclooxygenase (Cox), especially cyclooxygenase-2 (COX-2) in cell proliferation, and its inhibition in cancer control, apoptosis, as well as synergy with other forms of therapy. The inhibitors of the Cox enzyme are well known as members of the nonsteroidal anti-inflammatory drug (NSAID) class of pharmaceuticals.

METHODS

In vitro and in vivo studies of different cancers expressing COX-2, including glioma studies, along with the few clinical trials that have been reported are reviewed to specifically identify the actions of these agents.

RESULTS

The anticancer effect of the COX-2 inhibitors may occur irrelevant of COX-2 expression, and it appears to be drug-specific, as well as dose-specific in different cancers. In combination with chemotherapeutic agents, the COX-2 inhibitors may have an additive, synergistic, or inhibitory effect on tumor growth.

CONCLUSIONS

As evaluations of this class of drugs begin in glioma, in vitro and in vivo data should be acquired to accurately predict which compounds will have an effect in controlling tumor growth and at which doses these should be used. The actual expression and inhibition of COX-2 may not always be relevant to the effects on tumor growth.

Cyclooxygenase 2 expression in rectal cancer is of prognostic significance in patients receiving preoperative radiotherapy

PURPOSE

To determine the effect of cyclooxygenase (COX)-2 expression on clinical behavior in irradiated and nonirradiated rectal carcinomas.

EXPERIMENTAL DESIGN

Tumor samples were collected from 1,231 patients of the Dutch TME trial, in which rectal cancer patients were treated with standardized surgery and randomized for preoperative short-term (5 x 5 Gy) radiotherapy or no preoperative radiotherapy. Tissue microarrays were constructed from primary tumor material, and COX-2 expression was assessed by immunohistochemistry. Tumor cell apoptosis was determined by M30 immunostaining.

RESULTS

A high level of COX-2 expression after radiotherapy was associated with low levels of tumor cell apoptosis (P=0.001). COX-2 expression had no significant effect on patient survival or tumor recurrence in nonirradiated tumors. However, in patients receiving preoperative radiotherapy, high level of COX-2 expression was associated with higher incidence of distant recurrences [P=0.003; hazard ratio (HR), 1.7; 95% confidence interval (95% CI), 1.2-2.5] and shorter disease-free survival (P=0.002; HR, 1.8; 95% CI, 1.2-2.5) and overall survival (P=0.009; HR, 1.5; 95% CI, 1.1-2.0), independent of patient age, tumor stage, tumor location, or the presence of tumor cells in the circumferential resection margin.

CONCLUSIONS

A high level of COX-2 expression after preoperative radiotherapy in resection specimens is associated with apoptosis resistance, high distant recurrence rates, and a poor prognosis in rectal cancer.

Enhancement of glioblastoma radioresponse by a selective COX-2 inhibitor celecoxib: inhibition of tumor angiogenesis with extensive tumor necrosis

PURPOSE

Toward improved glioblastoma multiforme treatment, we determined whether celecoxib, a selective cyclooxygenase (COX)-2 inhibitor, could enhance glioblastoma radiosensitivity by inducing tumor necrosis and inhibiting tumor angiogenesis.

METHODS AND MATERIALS

U-87MG cells treated with celecoxib, irradiation, or both were assayed for clonogenic survival and angiogenic factor protein analysis (angiopoietin-1, angiopoietin-2, and vascular endothelial growth factor [VEGF]). In vivo, survival of mice intracranially implanted with U-87MG cells and treated with celecoxib and/or irradiation was monitored. Isolated tumors were assessed for tumor necrosis and tumor microvascular density by von Williebrand's factor (vWF) immunohistochemical staining.

RESULTS

Celecoxib (4 and 30 microM; 24, 48, and 72 h) enhanced U-87MG cell radiosensitivity by significantly reducing clonogenic survival of irradiated cells. Angiopoietin-1 and VEGF proteins were decreased, whereas angiopoietin-2 expression increased after 72 h of celecoxib alone and when combined with irradiation. In vivo, median survival of control mice intracranially implanted with U-87MG cells was 18 days. Celecoxib (100 mg/kg/day, 2 weeks) significantly extended median survival of irradiated mice (24 Gy total) from 34 to 41 days, with extensive tumor necrosis [24.5 +/- 8.6% of tumor region, compared with irradiation alone (2.7 +/- 1.8%)]. Tumor microvascular density was significantly reduced in combined celecoxib and irradiated tumors (52.5 +/- 2.9 microvessels per mm2 tumor region), compared with irradiated tumors alone (65.4 +/- 4.0 microvessels per mm2).

CONCLUSION

Celecoxib significantly enhanced glioblastoma radiosensitivity, reduced clonogenic survival, and prolonged survival of glioblastoma-implanted mice by inhibition of tumor angiogenesis with extensive tumor necrosis.

Inhibition of cyclooxygenase-2 activity by celecoxib does not lead to radiosensitization of human prostate cancer cells in vitro

PURPOSE

To evaluate the potential radiosensitizing effect of the specific COX-2 inhibitor celecoxib (Celebrex) on prostate carcinoma cells in vitro.

MATERIALS AND METHODS

The influence of celecoxib (concentration range 5 to 75 microM) on radiation-induced cellular and clonogenic survival was investigated in prostate carcinoma cell lines PC-3, DU145, LNCaP and normal prostate epithelial cells (PrEC). Western blot analysis and ELISA were used to determine the impact of radiation alone or radiation combined with celecoxib treatment on COX-2 expression and prostaglandin E2 synthesis. To evaluate induction of celecoxib-induced apoptosis cell cycle analysis has been performed.

RESULTS

Celecoxib (5, 10 and 25 microM) in combination with single-dose irradiation of 2 Gy induced a significant radiosensitization in normal prostate epithelial cells which could not be observed for any of the prostate carcinoma cell lines investigated. Increased COX-2 protein expression in PC-3 cells was obvious only after IR with 15 Gy, while PGE2 production was elevated following irradiation (2-15 Gy) in a dose-dependent manner. Treatment with celecoxib alone or in combination with IR led to a dose-dependent increase in COX-2 protein expression. Nevertheless pre-treatment with celecoxib caused a marked reduction of radiation-induced enzyme activity as tested at the level of PGE2 production, both in PC-3 and DU145 cells. Following fractionated irradiation with single doses of 2 Gy, elevated COX-2 protein expression as well as enhanced PGE2 production was observed already after the second fraction in PC-3 cells. Pre-treatment with celecoxib reduced the amount of PGE(2) significantly, but not of COX-2 protein.

CONCLUSIONS

Our data obtained for the human prostate cancer cell lines do not indicate that a marked inhibition of prostaglandin E2 synthesis by celecoxib leads to enhanced radiosensitization. Thus, in terms of radiosensitization the analysed prostate cancer cells can be classified as non-responders to celecoxib treatment.

Determination of endogenous tissue inflammation profiles by LC/MS/MS: COX- and LOX-derived bioactive lipids

Cyclooxygenase and lipoxygenase arachidonate products, including prostaglandins (PGs), leukotrienes (LTs), and hydroxyeicosatetraenoic acids (HETEs), are known to modulate inflammation within tissues and can serve as important etiologic factors in carcinogenesis. Eicosanoid content in tissues is typically determined either as a single molecular species through antibody-based assays or by high-performance liquid chromatography after addition of an exogenous substrate such as arachidonic acid. Unfortunately, the methods currently in use are either time-consuming or complicated. Here we report a method for simultaneously identifying eicosanoids appearing as endogenous bioactive lipids in in vivo settings using LC/MS/MS. The analyses indicate marked differences in endogenous eicosanoid content between malignant tissue types suggesting a need for selective therapeutic approaches. As a demonstration of the utility of the method, we present data to show that the technique can be used to distinguish eicosapentaenoic acid-derived formation of PGE(3) from PGE(2) in murine prostate tissue. The method has also been applied to an examination of endogenous eicosanoid metabolism in 7,12-dimethylbenz[a]anthracene (DMBA)-induced oral cancer in hamsters demonstrating the inflammatory nature of this type of cancer with elevated levels of both PGE(2) and LTB(4). In addition, the concentration of the eicosanoid 13-hydroxyoctadecadienoic acid was 67.6% lower in DMBA treated specimens than in control specimens. Thus, our method provides a powerful tool for measuring modulation of eicosanoid metabolites in various preclinical and clinical tissues and may be useful in studies of the endogenous changes in eicosanoid metabolism at various stages of cancer development.

Non-steroidal anti-inflammatory drugs to potentiate chemotherapy effects: from lab to clinic

Most solid tumors express the cyclooxygenase-2 (COX-2) protein, a target of NSAIDs. COX-2 overexpression in tumorsis considered a predictor of more advanced stage disease and of worse prognosis in a number of studies investigating solid malignancies. Therefore, NSAIDs are evaluated as anti-cancer drugs. NSAIDs inhibit proliferation, invasiveness of tumors, and angiogenesis and overcome apoptosis resistance in a COX-2 dependent and independent manner. This review will focus on the rationale behind NSAIDs, including selective COX-2 inhibitors, in combination with conventional chemotherapeutic drugs or novel molecular targeted drugs. Studies investigating anti-cancer effects of NSAIDs on cell lines and xenograft models have shown modulation of the Akt, NF-kappaB, tyrosine kinase and the death receptor-mediated apoptosis pathways. COX-2 expression in tumors is not yet used as biomarker in the clinic. Despite the increased risk on cardiovascular toxicity induced by selective COX-2 inhibitors, several ongoing clinical trials are still investigating the therapeutic benefits of NSAIDs in oncology. The anti-tumor effects in these trials balanced with the side effects data will define the precise role of selective COX-2 inhibitors in the treatment of cancer patients.

Inhalation delivery and anti-tumor activity of celecoxib in human orthotopic non-small cell lung cancer xenograft model

PURPOSE

To determine the in vivo anti-tumor effect of aerosolized Celecoxib (Cxb) in combination with i.v Docetaxel (Doc) and compare the anti-tumor effect with oral Cxb combined with i.v Doc in human orthotopic non-small cell lung cancer (NSCLC) xenograft model.

MATERIALS AND METHODS

Female Nu/Nu mice were implanted with orthotopic tumors by injecting A549 cells into the lung parenchyma. Seven day after tumor implantation the mice were treated with aerosolized Cxb (30 min exposure/day, 5 mg/ml solution) + i.v Doc (10 mg/kg) and the effect was compared with oral Cxb (150 mg/kg/day) + i.v Doc (10 mg/kg), for 28 days. Small-animal nose only inhalation chamber (CH Technologies, Westwood, NJ) was utilized for aerosol exposure. Therapeutic activity of Cxb (aerosol/oral) + Doc was estimated by differences in lung weight, tumor area and animal body weight. Lung tumor samples isolated from mice were analyzed for (a) PGE2 levels by enzyme immunoassay (EIA) (b) expression of Fas and Factor VIII by immunohistochemistry (c) IL-8 expression using EIA kits and (d) mRNA expression for caspase-3 by Real-Time PCR.

RESULTS

Mice treated with Cxb (aerosol/oral) + Doc showed significant reduction (P < 0.001) in lung weight and tumor area as compared to Cxb or Doc treatments. Cxb (aerosol/oral) + Doc showed increased apoptosis mediated via increased Fas and caspase-3 (P < 0.001) expression as compared to untreated control. Further, the combination treatment showed antiangiogenic effect as demonstrated by reduced expression of Factor VIII, IL-8 (P < 0.001) and PGE2 (P < 0.001) in lung tumors as compared to untreated control. Aerosolized Cxb at a significantly lower therapeutic dose (4.56 mg/kg/day) demonstrated comparable anti-tumor efficacy to orally administered Cxb (150 mg/kg/day).

CONCLUSION

Cxb was formulated and effectively delivered via aerosolization to treat orthotopic lung tumors in combination with i.v Doc. Cxb when administered by aerosol produced same therapeutic effect as oral Cxb, but at lower therapeutic dose and thus shows promise for the treatment of lung cancer.

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

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

COX-2 inhibitors act as radiosensitizer in tumor treatment

Since cyclooxygenase-2 (COX-2) is overexpressed in malignant tissues, the COX-2 mediated signaling pathway has been recognized as potential target for therapeutic intervention. In most human tumors, COX-2 overexpression has been associated with tumor aggressiveness and poor clinical outcome. In vitro studies show inhibition of cell proliferation by selective COX-2 inhibitors alone, and enhancement of the response to irradiation. In vivo experimental reports demonstrate enhanced tumor response and impediment of tumor neovascularization following radiotherapy combined with COX-2 inhibition. Clinical studies on the combination of irradiation with COX-2 inhibitors are emerging. Taken together, the perspective for the combined approach of radiotherapy with COX-2 inhibition yields clinical significance since preclinical data demonstrate selective COX-2 inhibitors to act as radiosensitizer in tumor treatment.