Andrew J. Dannenberg

COX‐2 is expressed in human pulmonary, colonic, and mammary tumors

The cyclooxygenase (COX) enzyme catalyzes the formation of prostaglandins, which can affect cell proliferation and alter the response of the immune system to malignant cells. The inducible form of COX, COX‐2, has been shown to be important in carcinogenesis.

Resveratrol Inhibits Cyclooxygenase-2 Transcription and Activity in Phorbol Ester-treated Human Mammary Epithelial Cells

We determined whether resveratrol, a phenolic antioxidant found in grapes and other food products, inhibited phorbol ester (PMA)-mediated induction of COX-2 in human mammary and oral epithelial cells. Treatment of cells with PMA induces COX-2 and causes a marked increase in the production of prostaglandin E2. These effects were inhibited by resveratrol. Resveratrol suppressed PMA-mediated increases in COX-2 mRNA and protein. Nuclear run-offs revealed increased rates of COX-2transcription after treatment with PMA, an effect that was inhibited by resveratrol. PMA caused about a 6-fold increase in COX-2promoter activity, which was suppressed by resveratrol. Transient transfections utilizing COX-2 promoter deletion constructs and COX-2 promoter constructs, in which specific enhancer elements were mutagenized, indicated that the effects of PMA and resveratrol were mediated via a cyclic AMP response element. Resveratrol inhibited PMA-mediated activation of protein kinase C. Overexpressing protein kinase C-α, ERK1, and c-Jun led to 4.7-, 5.1-, and 4-fold increases in COX-2 promoter activity, respectively. These effects also were inhibited by resveratrol. Resveratrol blocked PMA-dependent activation of AP-1-mediated gene expression. In addition to the above effects on gene expression, we found that resveratrol also directly inhibited the activity of COX-2. These data are likely to be important for understanding the anti-cancer and anti-inflammatory properties of resveratrol.

Cyclooxygenase 2: a molecular target for cancer prevention and treatment

Cyclooxygenase2 (COX-2), an inducible prostaglandin G/H synthase, is overexpressed in several human cancers. Here, the potential utility of selective COX-2 inhibitors in the prevention and treatment of cancer is considered. The mechanisms by which COX-2 levels increase in cancers, key data that indicate a causal link between increased COX-2 activity and tumorigenesis, and possible mechanisms of action of COX-2 are discussed. In a proof-of-principle clinical trial, treatment with the selective COX-2 inhibitor celecoxib reduced the number of colorectal polyps in patients with familial adenomatous polyposis. Selective COX-2 inhibitors appear to be sufficiently safe to permit large-scale clinical testing and numerous clinical trials are currently under way to determine whether selective inhibitors of COX-2 are effective in the prevention and treatment of cancer.

Cyclo-oxygenase 2: a pharmacological target for the prevention of cancer

Understanding the mechanisms underlying carcinogenesis provides insights that are necessary for the development of therapeutic strategies to prevent cancer. Chemoprevention--the use of drugs or natural substances to inhibit carcinogenesis - is an important and rapidly evolving aspect of cancer research. We discuss evidence that cyclooxygenase 2 (COX 2), an inducible form of the enzyme, is a potential pharmacological target to prevent cancer. Key data implicating a causal relation between increased activity of COX 2 and carcinogenesis and possible mechanisms of action of COX 2 in this context are covered. Importantly, selective COX 2 inhibitors appear to be safe enough in human beings to allow large-scale clinical testing in healthy people. Several chemoprevention trials using selective COX 2 inhibitors are underway.

Targeting cyclooxygenase-2 in human neoplasia: Rationale and promise

We apologize to the many laboratories whose contribution to this field could not be discussed or cited. Due to space limitations, many primary references were omitted. Support from the National Institutes of Health (R01 CA89578, R01 CA82578) and the Botwinick-Wolfensohn Foundation (in memory of Mr. and Mrs. Benjamin Botwinick) is gratefully acknowledged.

Inhibition of cyclooxygenase-2 gene expression by p53.

Oncogenes enhance the expression of cyclooxygenase (Cox)-2, but interactions between tumor suppressor genes and Cox-2 have not been studied. In the present work, we have compared the levels of Cox-2 and the production of prostaglandin E2 in mouse embryo fibroblasts that do not express any p53 ((10)1) versus the same cell line ((10.1)Val5) engineered to overexpress wild-type (wt) p53 at 32 °C or mutant p53 at 39 °C. Cells expressing wt p53 showed about a 10-fold decrease in synthesis of prostaglandin E2 compared with those expressing mutant p53. Levels of Cox-2 protein and mRNA were markedly suppressed by wt p53 but not by mutant p53. Nuclear run-offs revealed decreased rates of Cox-2 transcription in cells expressing wt p53. The activity of the Cox-2 promoter was reduced by 85% in cells expressing wt p53 but was reduced only by 30% in cells expressing mutant p53 compared with cells null for p53. The effect of p53 on the suppression of Cox-2 promoter activity was localized to the first 40 base pairs 5′ from the transcription start site. Electrophoretic mobility shift assay revealed that p53 competed with TATA-binding protein for binding to mouseCox-2 or human Cox-2 promoter extending from −50 to +52 base pairs. The results of this study suggest that interactions between p53 and Cox-2 could be important for understanding why levels of Cox-2 are undetectable in normal cells and increased in many tumors.

Cyclooxygenase-2 and Epidermal Growth Factor Receptor: Pharmacologic Targets for Chemoprevention

Understanding the mechanisms underlying carcinogenesis provides insights that are necessary for the development of therapeutic strategies to prevent cancer. Chemoprevention, the use of drugs or natural substances to inhibit carcinogenesis, is a rapidly evolving aspect of cancer research. Evidence is presented that cyclooxygenase-2 (COX-2) and epidermal growth factor receptor (EGFR) are potential pharmacologic targets to prevent cancer. In this paper, we review key data implicating a causal relationship between COX-2, EGFR, and carcinogenesis and possible mechanisms of action. We discuss evidence of crosstalk between COX-2 and EGFR in order to strengthen the rationale for combination chemoprevention, and review plans for a clinical trial that will evaluate the concept of combination chemoprevention targeting COX-2 and EGFR.

MicroRNA expression in squamous cell carcinoma and adenocarcinoma of the esophagus: Associations with survival

Purpose: The dismal outcome of esophageal cancer patients highlights the need for novel prognostic biomarkers, such as microRNAs (miRNA). Although recent studies have established the role of miRNAs in esophageal carcinoma, a comprehensive multicenter study investigating different histologic types, including squamous cell carcinoma (SCC) and adenocarcinoma with or without Barretts, is still lacking. Experimental Design: miRNA expression was measured in cancerous and adjacent noncancerous tissue pairs collected from 100 adenocarcinoma and 70 SCC patients enrolled at four clinical centers from the United States, Canada, and Japan. Microarray-based expression was measured in a subset of samples in two cohorts and was validated in all available samples. Results: In adenocarcinoma patients, miR-21, miR-223, miR-192, and miR-194 expression was elevated, whereas miR-203 expression was reduced in cancerous compared with noncancerous tissue. In SCC patients, we found elevated miR-21 and reduced miR-375 expression levels in cancerous compared with noncancerous tissue. When comparing cancerous tissue expression between adenocarcinoma and SCC patients, miR-194 and miR-375 were elevated in adenocarcinoma patients. Significantly, elevated miR-21 expression in noncancerous tissue of SCC patients and reduced levels of miR-375 in cancerous tissue of adenocarcinoma patients with Barretts were strongly associated with worse prognosis. Associations with prognosis were independent of tumor stage or nodal status, cohort type, and chemoradiation therapy. Conclusions: Our multicenter-based results highlight miRNAs involved in major histologic types of esophageal carcinoma and uncover significant associations with prognosis. Elucidating miRNAs relevant to esophageal carcinogenesis is potentially clinically useful for developing prognostic biomarkers and identifying novel drug targets and therapies. (Clin Cancer Res 2009;15(19):6192–200)

Peroxisome Proliferator-activated Receptor γ Ligands Suppress the Transcriptional Activation of Cyclooxygenase-2 EVIDENCE FOR INVOLVEMENT OF ACTIVATOR PROTEIN-1 AND CREB-BINDING PROTEIN/p300

We investigated whether peroxisome proliferator-activated receptor γ (PPARγ) ligands (ciglitazone, troglitazone, and 15-deoxy-Δ12,14prostaglandin J2) inhibited cyclooxygenase-2 (COX-2) induction in human epithelial cells. Ligands of PPARγ inhibited phorbol ester (phorbol 12-myristate 13-acetate, PMA)-mediated induction of COX-2 and prostaglandin E2 synthesis. Nuclear run-offs revealed increased rates of COX-2 transcription after treatment with PMA, an effect that was inhibited by PPARγ ligands. PMA-mediated induction of COX-2 promoter activity was inhibited by PPARγ ligands; this suppressive effect was prevented by overexpressing a dominant negative form of PPARγ or a PPAR response element decoy oligonucleotide. The stimulatory effects of PMA were mediated by a cyclic AMP response element in the COX-2promoter. Treatment with PMA increased activator protein-1 (AP-1) activity and the binding of c-Jun, c-Fos, and ATF-2 to the cyclic AMP response element, effects that were blocked by PPARγ ligands. These findings raised questions about the mechanism underlying the anti-AP-1 effect of PPARγ ligands. The induction of c-Jun by PMA was blocked by PPARγ ligands. Overexpression of either c-Jun or CREB-binding protein/p300 partially relieved the suppressive effect of PPARγ ligands. When CREB-binding protein and c-Jun were overexpressed together, the ability of PPARγ ligands to suppress PMA-mediated induction of COX-2 promoter activity was essentially abrogated. Bisphenol A diglycidyl ether, a compound that binds to PPARγ but lacks the ability to activate transcription, also inhibited PMA-mediated induction of AP-1 activity and COX-2. Taken together, these findings are likely to be important for understanding the anti-inflammatory and anti-cancer properties of PPARγ ligands.

Inflammation and increased aromatase expression occur in the breast tissue of obese women with breast cancer

Obesity is a risk factor for the development of hormone receptor–positive breast cancer in postmenopausal women and has been associated with an increased risk of recurrence and reduced survival. In humans, obesity causes subclinical inflammation in visceral and subcutaneous adipose tissue, characterized by necrotic adipocytes surrounded by macrophages forming crown-like structures (CLS). Recently, we found increased numbers of CLS, activation of the NF-κB transcription factor, and elevated aromatase levels and activity in the mammary glands of obese mice. These preclinical findings raised the possibility that the obesity → inflammation axis is important for the development and progression of breast cancer. Here, our main objective was to determine if the findings in mouse models of obesity translated to women. Breast tissue was obtained from 30 women who underwent breast surgery. CLS of the breast (CLS-B) was found in nearly 50% (14 of 30) of patient samples. The severity of breast inflammation, defined as the CLS-B index, correlated with both body mass index (P < 0.001) and adipocyte size (P = 0.01). Increased NF-κB binding activity and elevated aromatase expression and activity were found in the inflamed breast tissue of overweight and obese women. Collectively, our results suggest that the obesity → inflammation → aromatase axis is present in the breast tissue of most overweight and obese women. The presence of CLS-B may be a biomarker of increased breast cancer risk or poor prognosis. Cancer Prev Res; 4(7); 1021–9. ©2011 AACR.