Overexpression of cyclooxygenase-2 is associated with a favorable prognostic phenotype in breast carcinoma

The Role of NSAIDs in Breast Cancer Prevention and Relapse: Current Evidence and Future Perspectives

Aspirin and other non-steroidal anti-inflammatory drugs (NSAIDs) have received considerable interest as potential chemopreventive agents. The aim of this review is to summarize the accumulated knowledge on the effect of NSAIDs on breast cancer incidence and natural history, and the underlying pathophysiology. NSAIDs mainly block inflammation by inhibiting cyclooxygenase enzymes, leading to lower prostaglandin synthesis. The latter has been reported to affect breast cancer risk through hormonal and inflammation-related pathways. Intensity, dose, frequency, duration, and timing of administration may also be significant. There is currently enough evidence to support a role of NSAIDs in breast cancer prevention and relapse, which deserves further large-scale experimental and clinical investigation.

The prognostic impact of COX-2 expression in breast cancer depends on oral contraceptive history, preoperative NSAID use, and tumor size

The association between tumor cyclooxygenase 2 (COX-2) expression and breast cancer prognosis has been inconsistent. The purpose of this study was to evaluate the prognostic significance of COX-2 tumor expression according to adjuvant treatment, and potential effect modifications of non-steroid anti-inflammatory drug (NSAID) use, and other tumor and lifestyle factors. A prospective cohort of 1,116 patients with primary breast cancer in Lund, Sweden, included 2002-2012 was followed until June 2014 (median 5 years). Tumor-specific COX-2 expression was evaluated on tissue microarrays using immunohistochemistry. Associations between COX-2 intensity (negative, weak-moderate, high) and patient and tumor characteristics as well as prognosis were analyzed. Tumor-specific COX-2 expression was available for 911 patients and was significantly associated with higher age at diagnosis and less aggressive tumor characteristics. Higher COX-2 expression was associated with lower risk for breast cancer events during the first five years of follow-up, _adj HR 0.60 (95%CI: 0.37-0.97), per category. The association between COX-2 expression and prognosis was significantly modified by oral contraceptive (OC) use (P_interaction  = 0.048), preoperative NSAID use (P_interaction  = 0.009), and tumor size (P_interaction  = 0.039). COX-2 negativity was associated with increased risk for events during the first five years in ever OC users, _adj HR 1.94 (1.01-3.72) and during the 11-year follow-up in preoperative NSAID users, _adj HR 4.51 (1.18-11.44) as well as in patients with large tumors, _adj HR 2.57 (1.28-5.15). In conclusion, this study, one of the largest evaluating COX-2 expression in breast cancer, indicates that the prognostic impact of COX-2 expression depends on host factors and tumor characteristics.

Obesity-related proliferative diseases: the interaction between adipose tissue and estrogens in post-menopausal women

Epidemiological studies have shown that overweight and cancer are closely related, even though obesity alone does not apparently heighten cancer risk by the same amount. Given the low overall risk of all cancers with obesity, it is unlikely that obesity alone causes cancer, but should instead be considered as a tumor promoter. There are three main hypotheses that could explain how obesity might contribute to cancer development and growth: the inflammatory cytokines from adipose tissue hypothesis, the insulin resistance and hyperinsulinemia hypothesis, and the unopposed estrogen cancer hypothesis. The link between obesity and cancer is that adipocytes constitute a major component of the tumor microenvironment for breast and abdominally metastasizing cancers, promoting tumor growth. This review will mainly focus attention on the relationship between adipose tissue, estrogens, and cancer risk.

Potency of non-steroidal anti-inflammatory drugs in chemotherapy

Cancer cell resistance, particularly multidrug resistance (MDR), is the leading cause of chemotherapy failure. A number of mechanisms involved in the development of MDR have been described, including the overexpression of ATP-dependent membrane-bound transport proteins. The enhanced expression of these proteins, referred to as ATP-binding cassette (ABC) transporters, results in an increased cellular efflux of the cytotoxic drug, thereby reducing its intracellular concentration to an ineffective level. Non-steroidal anti-inflammatory drugs (NSAIDs) are the most frequently consumed drugs worldwide. NSAIDs are mainly used to treat pain, fever and inflammation. Numerous studies suggest that NSAIDs also show promise as anticancer drugs. NSAIDs have been shown to reduce cancer cell proliferation, motility, angiogenesis and invasiveness. In addition to these effects, NSAIDs have been shown to induce apoptosis in a wide variety of cancer types. Moreover, several studies have indicated that NSAIDs may sensitise cancer cells to the antiproliferative effects of cytotoxic drugs by modulating ABC transporter activity. Therefore, combining specific NSAIDs with chemotherapeutic drugs may have clinical applications. Such treatments may allow for the use of a lower dose of cytotoxic drugs and may also enhance the effectiveness of therapy. The objective of this review was to discuss the possible role of NSAIDs in the modulation of antitumour drug cytotoxicity. We particularly emphasised on the use of COX-2 inhibitors in combination with chemotherapy and the molecular and cellular mechanisms underlying the alterations in outcome that occur in response to this combination therapy.

Prognostic influence of cyclooxygenase-2 protein and mRNA expression in node-negative breast cancer patients

Background

Cyclooxygenases (COX) play a key role in prostaglandin metabolism and are important for tumor development and progression. The aim of this study was to analyze the prognostic impact of COX-2 expression in a cohort of lymph node-negative breast cancer patients not treated in the adjuvant setting.

Methods

COX-2 expression was determined by immunohistochemistry (IHC) in tumor tissue of 193 node-negative breast cancer patients. Additionally, mRNA expression was determined in corresponding tumor samples using microarray based gene-expression data. Univariate and multivariate Cox regression analyses adjusted for age at diagnosis, tumor size, histological grade, human epithelial growth factor receptor 2 (HER2), estrogen receptor (ER) and progesterone receptor (PR) were performed to evaluate the association of both COX-2 protein and mRNA expression with survival. Survival rates were determined by the Kaplan-Meier method. Correlations between COX-2 expression and established prognostic factors were analyzed using the Chi-square test. A potential correlation between COX-2 protein expression and COX-2 mRNA expression was assessed utilizing the Kruscal-Wallis-H-test.

Results

COX-2 protein expression was positive in 24.9% of the breast cancer samples. Univariate analysis showed that COX-2 protein expression was associated with shorter disease-free survival (DFS) (P = 0.0001), metastasis-free survival (MFS) (P = 0.002) as well as breast cancer specific overall survival (OS) (P = 0.043). In multivariate analysis COX-2 expression retained its significance independent of established prognostic factors for shorter DFS (P < 0.001, HR = 2.767, 95% CI = 1.563-4.901) and for inferior MFS (P = 0.002, HR = 2.7, 95% CI = 1.469-5.263) but not for OS (P = 0.096, HR = 1.929, 95% CI = 0.889-4.187). In contrast, COX-2 mRNA expression was not related to survival and failed to show a correlation with protein expression (P = 0.410).

Conclusions

The present findings support the hypothesis that COX-2 protein but not mRNA expression is associated with an unfavorable outcome in node-negative breast cancer.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2407-14-952) contains supplementary material, which is available to authorized users.

Stromal, rather than epithelial cyclooxygenase-2 (COX-2) expression is associated with overall survival of breast cancer patients

Background

Prognostic value of enhanced COX-2 expression in breast cancer has been controversial for a long time. The opinions vary widely between studies. Moreover, significant majority of studies considered only COX-2 expression in cancer epithelial cells.

Methods

We examined the prognostic value of COX-2 expression in both epithelial and stromal cells using three different antibodies and three algorithms of immunohistochemical scoring and categorizing the tumours into COX-2 overexpressing groups.

Results

Our results demonstrate that COX-2 expression in stromal cells is independent prognostic factor indicating worse overall survival of patients. Such a result was obtained using each of the three antibodies and two of the algorithms used for evaluations of COX-2 expression levels. We also show that immunohistochemical assessment of the prognostic value of COX-2 expression in cancer epithelial cells depends to a large extent on a combination of primary antibodies and algorithms used for determination of the COX-2 over-expressing tumours.

Conclusions

Our results indicate that stromal expression of COX-2 is independent prognostic parameter relatively insensitive to variations in sensitivity of antibodies used for its determination. Wide scatter of the published results concerning prognostic value of COX-2 expression in breast cancer tissues seems to be due to a large extent to multitude of antibodies and scoring algorithms used by different groups.

COX2 expression in high-grade breast cancer: evidence for prognostic significance in the subset of triple-negative breast cancer patients

COX2 expression correlates with high-grade breast cancer, but the clinical significance and possible prognostic influence in these patients have not been studied in depth. Our goal was to evaluate the significance of COX2 expression in a group of patients with high-grade breast cancer. Three hundred and three patients (median age 55; age range 25-95 years) with high-grade breast cancer entered this retrospective study. Mean follow-up was 65.2 months (4-179 months). COX2 expression was studied by immunohistochemistry. The distribution of patients with high-grade tumors according to staining for COX2 was as follows: score 0-28/303 (9.3 %); score 1-101/303 (33.3 %); score 2-114/303 (37.6 %); score 3-60/303 (19.8 %). Patients with score 2 and 3 were classified as COX2 positive (174 of 303 patients (57.4 %). There was no correlation between any clinicopathological pattern, ER, PR, Her2 status and COX2 expression. In the group of patients with triple-negative breast cancer, the 5-year disease-free survival rate was 58.3 % for patients with COX2 expression compared with 83.9 % for patients without COX2 expression (P = 0.042). COX2 expression did not provide any prognostic significance for the other biological subtypes of breast cancer with high-grade histological features.

COX-2 and PPAR-γ confer cannabidiol-induced apoptosis of human lung cancer cells

The antitumorigenic mechanism of cannabidiol is still controversial. This study investigates the role of COX-2 and PPAR-γ in cannabidiol's proapoptotic and tumor-regressive action. In lung cancer cell lines (A549, H460) and primary cells from a patient with lung cancer, cannabidiol elicited decreased viability associated with apoptosis. Apoptotic cell death by cannabidiol was suppressed by NS-398 (COX-2 inhibitor), GW9662 (PPAR-γ antagonist), and siRNA targeting COX-2 and PPAR-γ. Cannabidiol-induced apoptosis was paralleled by upregulation of COX-2 and PPAR-γ mRNA and protein expression with a maximum induction of COX-2 mRNA after 8 hours and continuous increases of PPAR-γ mRNA when compared with vehicle. In response to cannabidiol, tumor cell lines exhibited increased levels of COX-2-dependent prostaglandins (PG) among which PGD(2) and 15-deoxy-Δ(12,14)-PGJ(2) (15d-PGJ(2)) caused a translocation of PPAR-γ to the nucleus and induced a PPAR-γ-dependent apoptotic cell death. Moreover, in A549-xenografted nude mice, cannabidiol caused upregulation of COX-2 and PPAR-γ in tumor tissue and tumor regression that was reversible by GW9662. Together, our data show a novel proapoptotic mechanism of cannabidiol involving initial upregulation of COX-2 and PPAR-γ and a subsequent nuclear translocation of PPAR-γ by COX-2-dependent PGs.

Clinical relevance of cyclooxygenase-2 and matrix metalloproteinases (MMP-2 and MT1-MMP) in human breast cancer tissue

Breast cancer (BC) is the most common neoplasm among women in most developed countries, including Egypt. Elevated levels of certain proteins in human BC are associated with unfavorable prognosis and progressive stages of the disease. The aim of our study was to evaluate the protein expression profile and prognostic significance of cyclooxygenase-2 (COX-2), matrix metalloproteinase-2 (MMP-2), MMP-9 and membrane type 1-MMP (MT1-MMP) and their interaction in operable BC patients. The protein expression of COX-2, MMP-2 and MT1-MMP were evaluated by western blot technique, whereas enzymatic activity of MMP-2 and MMP-9 was determined by zymography in 47 breast cancer patients as well as normal adjacent tissues. Also, the correlation between these proteins and age, tumor size, LN stage, TNM stage, estrogen receptor, progesterone receptor, disease-free survival, and overall survival (OS) has been investigated. As compared to adjacent normal tissues, COX-2, MMP-2 and MT1-MMP were over-expressed in 43, 64, and 60 % of tumor tissues, respectively. In the same pattern, the activity of MMP-2 (62 %) and MMP-9 (45 %) was elevated in BC tissues. Multivariate analysis showed a positive correlation between the protein expression of COX-2, MMP-2, and MT1-MMP and the activity of MMP-2 and MMP-9 in BC patients. However, the enzymatic activity showed no correlation with clinicopathological features. This study confirms the preclinical evidence that COX-2 increased the expression of MT1-MMP, which in turn activates MMP-2. The lack of correlation with clinicopathological features, OS or disease-free survival ascertains the complexity of tumor progression and metastasis with many pro- and counter regulatory factors.

COX-2 expression predicts worse breast cancer prognosis and does not modify the association with aspirin

Some previous studies have found worse prognosis among cyclooxygenase-2 (COX-2)-expressing breast cancers. Aspirin and NSAIDs inhibit COX-2. Three studies, including ours, have reported a survival advantage among women with breast cancer who take either aspirin or NSAIDs. Through this study we hypothesized that in the Nurses' Health Study (NHS), COX-2 expression would be associated with worse prognosis, and aspirin use would be associated with better survival particularly among women with COX-2 positive tumors. In this study we investigated 2,001 women presenting with invasive breast cancers stained for COX-2 by immunohistochemistry. Tumor prognostic factors were from medical records. Aspirin use was assessed at least 12 months after diagnosis and updated. Cause of death was identified from death certificates. Statistical analyses included logistic regression of prognostic factors with COX-2 status as the outcome, and proportional hazards regression with breast cancer death as the outcome. Tumor COX-2 expression was associated with higher diagnostic stage. Compared with stage I, the RR(95% CI) for stages II-IV were 1.16 (0.93-1.45), 1.68 (1.27-2.22), and 1.76 (0.93-3.32). COX-2 expression was associated with lobular compared with ductal histology (1.40 [1.02-1.92]), and estrogen receptor positive compared with negative (2.22 [1.66-2.95]). The RR(95% CI) of breast cancer death for current aspirin use was similar for women with COX-2-positive and COX-2-negative tumors; 0.64 (0.43-0.96) and 0.57 (0.44-0.74), respectively. In the NHS, COX-2 breast cancer expression was associated with higher stage at diagnosis. The survival benefit associated with aspirin use did not differ by COX-2 status. COX-2 breast cancer expression is associated with worse prognosis. If aspirin truly impacts breast cancer survival, then it is not solely via COX-2.

Non-steroidal anti-inflammatory drugs (NSAIDs) and breast cancer risk: differences by molecular subtype

Use of non-steroidal anti-inflammatory drugs (NSAIDs) has been associated with reduced risk of breast cancer, though findings have been inconsistent. This inconsistency may result from differences in etiology for breast tumors of different subtypes. We examined the association between NSAID use and breast cancer characterized by molecular subtypes in a population-based case-control study in Western New York. Cases (n = 1,170) were women with incident, primary, histologically confirmed breast cancer. Controls (n = 2,115) were randomly selected from NY Department of Motor Vehicles records (<65 years) or Medicare rolls (≥ 65 years). Participants answered questions regarding their use of aspirin and ibuprofen in the year prior to interview and their use of aspirin throughout their adult life. Logistic regression models estimated odds ratios (OR) and 95% confidence intervals (95% CI). Recent and lifetime aspirin use was associated with reduced risk, with no differences by subtype. Recent use of ibuprofen was significantly associated with increased risk of ER+/PR+(OR 1.33, 95% CI: 1.09-1.62), HER2- (OR 1.27, 95% CI: 1.05-1.53), and p53- breast cancers (OR 1.28, 95% CI: 1.04-1.57), as well as luminal A or B breast cancers. These findings support the hypothesis of heterogeneous etiologies of breast cancer subtypes and that aspirin and ibuprofen vary in their effects.

Cyclooxygenase-2 expression in animal cancers

Cyclooxygenase (COX; also known as prostaglandin endoperoxide synthase) is a key enzyme in the biochemical pathway leading to the synthesis of prostaglandins. A large amount of epidemiological and experimental evidence supports a role for COX-2, the inducible form of the enzyme, in human tumorigenesis, notably in colorectal cancer. COX-2 mediates this role through the production of PGE(2) that acts to inhibit apoptosis, promote cell proliferation, stimulate angiogenesis, and decrease immunity. Similarly, COX-2 is believed to be involved in the oncogenesis of some cancers in domestic animals. Here, the author reviews the current knowledge on COX-2 expression and role in cancers of dogs, cats, and horses. Data indicate that COX-2 upregulation is present in many animal cancers, but there is presently not enough information to clearly define the prognostic significance of COX-2 expression. To date, only few reports document an association between COX-2 expression and survival, notably in canine mammary cancers and osteosarcomas. Some evidence suggests that COX inhibitors could be useful in the prevention and/or treatment of certain cancers in domestic animals, the best example being urinary transitional cell carcinomas in dogs. However, determination of the levels of COX-2 in a tumor does not appear to be a good prognostic factor or a good indicator for the response to nonsteroidal anti-inflammatory drug therapy. Clearly, additional research, including the development of in vitro cell systems, is needed to determine if COX-2 expression can be used as a reliable prognostic factor and as a definite therapeutic target in animal cancers.

The value of COX-2 expression in the prognostic parameters of invasive ductal carcinoma of the breast

Cyclooxygenase is an enzyme that changes the immune response to malign cells and catalyzes prostaglandins that may have an impact on cell proliferation. The purpose of this study was to examine the relation between established clinicopathological parameters in breast carcinomas and COX-2 protein expression. COX-2, estrogen receptor (ER), progesterone receptor (PR) and c-erB-2 primary antibodies were assessed in the slides prepared from the paraffin blocks of 62 invasive ductal carcinoma cases. The relation between ER, PR, and c-erbB-2 positivity, histological grade, nuclear grade, lymphovascular invasion, tumor diameter, lymph node positivity, metastasis, and age were evaluated. The results were analyzed statistically. Cytoplasmic COX-2 expression was seen in 75.8% of all breast carcinomas. In both univariate and multivariate logistic regression analysis, there was a positive correlation between COX-2 expression and negative ER status, respectively (P=0.0173) (P=0.016). There was any statistically significant relation between PR positivity, c-erbB-2 positivity, histological grade, nuclear grade, lymphovascular invasion, tumor diameter, lymph node positivity, metastasis, and age (P≥0.05). Given that there was found a statistically significant relation between COX-2 expression and negative ER status, which is considered a poor prognostic parameter, suggests that COX-2 expression can have a place among the other prognostic parameters of breast carcinoma.

Celecoxib antagonizes perifosine's anticancer activity involving a cyclooxygenase-2-dependent mechanism

Perifosine is an orally bioavailable alkylphospholipid currently being tested in phase II clinical trials as a potential anticancer drug. In this study, we reveal a novel mechanism underlying the anticancer activity of perifosine that involves the induction of cyclooxygenase 2 (COX-2) in human cancer cells. Perifosine induced apoptosis and/or cell cycle arrest in several lung and head and neck cancer cell lines. However, the combination of perifosine with low concentrations of celecoxib rendered cells less sensitive to perifosine both in cell culture systems and in lung cancer xenograft models. Subsequently, we examined the effects of perifosine on COX-2 expression and activity in a set of lung and head and neck cancer cell lines, and found that perifosine rapidly and potently increased COX-2 levels and activity, the degrees of which correlated to the abilities of perifosine to inhibit the growth of cancer cells. We also detected increased COX-2 levels in lung cancer xenografts treated with perifosine. Moreover, blockage of COX-2 induction by both antisense and small interfering RNA approaches decreased cell sensitivity to perifosine. Collectively, these data indicate that the activation of COX-2 contributes to the anticancer activity of perifosine, including apoptosis induction and growth arrest. These data are clinically relevant as they suggest that the combination of perifosine and COX-2 inhibitors such as celecoxib, may produce a potential drug contradiction.

COX-2 expression correlates with survival in patients with osteosarcoma lung metastases

The purpose of this study was to determine whether a correlation exists between tumor cyclooxygenase (COX)-2 expression and disease-specific survival in patients with osteosarcoma lung metastases. Thirty-six patients diagnosed with osteosarcoma lung metastases between the years 1990 and 2001 were included in this retrospective study. The majority of the patients (72%) presented newly -diagnosed osteosarcoma lung metastases whereas the remaining patients (28%) presented recurrent disease. Clinicopathologic parameters were obtained from patients' clinical records. Tissue samples were obtained at the time of resection of the lung metastases and stained for COX-2 using immunohistochemistry. Samples were graded according to the intensity of COX-2 staining (grade 0: negative, grade 1: very weak, grade 2: weak, grade 3: moderate, and grade 4: strong). COX-2 staining was correlated with disease-specific survival and clinicopathologic parameters using the Jonckheere-Terpstra and the Kruskal-Wallis tests. All patients with grade 3 or 4 COX-2 expression died of osteosarcoma lung metastases. Ten percent of patients with grade 2 COX-2 expression and 29% of patients with grade 1 expression were alive and free of disease at the last follow-up. By contrast, 60% of the patients with grade 0 COX-2 expression were alive and free of disease at the last follow-up. No association between COX-2 expression and clinicopathologic parameters was found. However, COX-2 expression correlated inversely with disease-specific survival in patients with osteosarcoma lung metastases. Our data indicate that COX-2 expression in metastatic osteosarcoma may have prognostic significance.

Estrogen-dependent prognostic significance of cyclooxygenase-2 expression in early-stage invasive breast cancers treated with breast-conserving surgery and radiation

PURPOSE

To evaluate the prognostic significance of cyclooxygenase-2 (COX-2) in breast cancer patients treated with conservative surgery and radiation therapy (CS+RT).

METHODS AND MATERIALS

Between 1975 and 2003, we retrieved specimens from 504 breast cancer patients treated with CS+RT. The specimens were constructed into tissue microarrays processed and stained for estrogen receptor (ER), progesterone receptor, Her2/neu, and COX-2. Each core was scored as positive or negative. All data including demographics, clinical, pathologic, staging, and outcome variables were entered into a computerized database.

RESULTS

Expression of COX-2 was positive in 58% of cases and correlated with younger age (p = 0.01) and larger tumor size (p = 0.001). Expression of COX-2 was predictive of local relapse (relative risk[RR], 3.248; 95% confidence interval [CI], 1.340-7.871; p = 0.0091), distant metastasis (RR, 2.21; 95% CI, 1.259-3.896; p = 0.0058), and decreased survival (RR, 2.321; 95% CI, 1.324-4.071; p = 0.0033). Among ER-positive patients, COX-2 expression was predictive of worse local control (85% vs. 93%, p = 0.04), distant metastasis (75% vs. 95%, p = 0.002) and worse survival (65% vs. 94%, p = 0.002). Among ER-negative tumors COX-2 expression was not significantly correlated with local control (87 vs. 95%, p = 0.12), distant metastasis (73% vs. 78%, p = 0.39), or survival (77% vs. 87%, p = 0.15).

CONCLUSIONS

In breast cancer patients treated with CS+RT, COX-2 expression is associated with younger age, larger tumor size, worse local control, distant metastasis, and worse overall survival. The significance is limited to hormone receptor-positive tumors, consistent with the known effect of COX-2/PGE2 on aromatase activity. Use of COX-2 inhibitors in estrogen-dependent breast cancers warrants further investigation.

Cyclooxygenase-2 (cox-2) and the inflammogenesis of cancer

Cohesive scientific evidence from molecular, animal, and human investigations supports the hypothesis that aberrant induction of COX-2 and up-regulation of the prostaglandin cascade play a significant role in carcinogenesis, and reciprocally, blockade of the process has strong potential for cancer prevention and therapy. Supporting evidence includes the following: [1] expression of constitutive COX-2-catalyzed prostaglandin biosynthesis is induced by most cancer-causing agents including tobacco smoke and its components (polycylic aromatic amines, heterocyclic amines, nitrosamines), essential polyunsaturated fatty acids (unconjugated linoleic acid), mitogens, growth factors, proinflammatory cytokines, microbial agents, tumor promoters, and other epigenetic factors, [2] COX-2 expression is a characteristic feature of all premalignant neoplasms, [3] COX-2 expression is a characteristic feature of all malignant neoplasms, and expression intensifies with stage at detection and cancer progression and metastasis, [4] all essential features of carcinogenesis (mutagenesis, mitogenesis, angiogenesis, reduced apoptosis, metastasis, and immunosuppression) are linked to COX-2-driven prostaglandin (PGE-2) biosynthesis, [5] animal studies show that COX-2 up-regulation (in the absence of genetic mutations) is sufficient to stimulate the transformation of normal cells to invasive cancer and metastatic disease, [6] non-selective COX-2 inhibitors, such as aspirin and ibuprofen, reduce the risk of human cancer and precancerous lesions, and [7] selective COX-2 inhibitors, such as celecoxib, reduce the risk of human cancer and precancerous lesions at all anatomic sites thus far investigated. Results confirming that COX-2 blockade is effective for both cancer prevention and therapy have been tempered by observations that some COX2 inhibitors pose a risk to the cardiovascular system, and more studies are needed in order to determine if certain of these drugs can be taken at dosages that prevent cancer without increasing cardiovascular risk. It is emphasized that the "inflammogenesis model of cancer" is not mutually exclusive and may in fact be synergistic with the accumulation of somatic mutations in tumor suppressor genes and oncogenes or epigenetic factors in the development of cancer.

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

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

Cyclooxygenase-2 expression in astrocytomas. Relationship with microvascular parameters, angiogenic factors expression and survival

OBJECTIVE

Cyclooxygenase-2 (COX-2) is the enzyme isoform involved in the synthesis of prostaglandins (PGs) and thromboxane from arachidonic acid. The role of the up-regulation of COX-2 in the formation and progression of gliomas has been dealt with in earlier reports, which describe increased levels of PGs within gliomas. In the present study, we examined the expression of COX-2 in diffuse gliomas of astrocytic origin in relation to microvascular parameters, angiogenic factors and survival.

MATERIALS AND METHODS

A total of 83 cases of diffuse astrocytomas (grade II-IV) were analyzed by immunohistochemistry for the presence of COX-2.

RESULTS

COX-2 expression was detected in 79 cases (95%) with an increased expression in grade IV as compared to grades II/III (p=0.024). A positive correlation occurred between COX-2 and angiogenic factors such as vascular endothelial growth factor (VEGF) (p<0.0001) and hypoxia inducible factor (HIF)-1alpha (p=0.005), as well as the tumours' proliferative activity (expressed as the percentage of Ki-67 positive cells) (p=0.032), and total vascular area (TVA) (p=0.040). In univariate analysis, COX-2 was associated with shortened survival (p = 0.050). Multivariate survival analysis showed that the interaction model of COX-2 with grade along with age were the only significant prognostic indicators.

CONCLUSION

These results implicate COX-2 in the angiogenesis and biological aggressiveness of diffuse astrocytomas, and suggest that it would be worthwhile to examine how the inhibition of COX-2 expression may influence astrocytoma patients' survival.