Alterations in lipoxygenase and cyclooxygenase-2 catalytic activity and mRNA expression in prostate carcinoma

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.

Activation of the Thromboxane A2 Pathway in Human Prostate Cancer Correlates with Tumor Gleason Score and Pathologic Stage

OBJECTIVE

We investigated the potential involvement of the thromboxane A(2) (TXA(2)) pathway in human prostate cancer (PCa).

METHODS

Expression of cyclooxygenase-2 (COX-2), TXA(2) synthase (TXS), and TXA(2) receptors (TPRs), the main actors of the TXA(2) pathway, was analyzed on serial tissue sections from 46 human PCa specimens.

RESULTS

The expression levels of COX-2, TXS, and TPRs were significantly higher in malignant than in corresponding nontumoral prostatic epithelial cells. Increased immunoreactivity for these antigens was also observed in high-grade prostate intraepithelial neoplasia (HGPIN) glands. COX-2, TXS, and TPR proteins usually displayed a coordinated overexpression pattern in PCa lesions, as assessed in serial tissue sections. Increased levels of these proteins in the tumors were all significantly associated with higher Gleason scores and pathologic stages.

CONCLUSIONS

Proteins specifically involved in the TXA(2) pathway are up-regulated in human PCa and their level of expression is associated with tumor extraprostatic extension and loss of differentiation. Our study is the first to examine simultaneously all key proteins involved in this pathway including TXA(2) receptors and results suggest that the TXA(2) pathway may be a potential target for PCa prevention/therapy.

Docosahexaenoic acid in combination with celecoxib modulates HSP70 and p53 proteins in prostate cancer cells

The role of cyclooxygenase-2 (COX-2) and the mechanism by which it influences the development and behavior of prostate cancer is unclear. Selective COX-2 inhibitors may be effective against prostate cancer via COX-2-independent mechanisms. But administration of high doses of COX-2 inhibitors over longer period of time may not be devoid of side effects. There is increasing interest in using COX-2 inhibitors in combination with other chemopreventive agents to overcome the issue of toxicity. However, the molecular mechanisms underlying their combined actions are not well understood. Therefore, the present study was designed to determine the effects of low doses of docosahexaenoic acid (DHA) in combination with celecoxib on the molecular targets at the proteins level in rat prostate cancer cells. Two-dimensional gel electrophoresis, in combination with mass spectrometry analysis, was used for protein identification. Western blot analysis confirmed the proteins identified. Paraffin-embedded tissue sections from the rat prostate tumor were used to detect base level expression of heat shock protein 70 (HSP70) and p53. The rate of cancer cell growth was inhibited more effectively (p < 0.01) by DHA in combination with celecoxib at lower doses (2.5 microM each). A total number of twelve proteins were differentially expressed by the combined action of DHA and celecoxib at low doses. It was interesting to note that these agents activated both HSP70 and p53 proteins. Activation of HSP70 by the combined actions of DHA and celecoxib in the presence of wild-type p53 reveals a unique COX-2 independent mode of action against prostate cancer.

Similarities and Differences in Tumor Growth, Skeletal Remodeling and Pain in an Osteolytic and Osteoblastic Model of Bone Cancer

More than 1.3 million cases of cancer will be diagnosed in 2006 in the United States alone, and 90% of patients with advanced cancer will experience significant, life-altering cancer-induced pain. Bone cancer pain is the most common pain in patients with advanced cancer as most common tumors including breast, prostate, and lung have a remarkable affinity to metastasize to bone. Once tumors metastasize to bone they are a major cause of morbidity and mortality as the tumor induces significant skeletal remodeling, pain and anemia, which reduce the survival and quality of life of the patient. Currently, the factors that drive cancer pain are poorly understood; however, several recently introduced models of cancer pain are not only providing insight into the mechanisms that drive bone cancer pain but are guiding the development of novel mechanism-based therapies to treat the pain and skeletal remodeling that accompanies metatstatic bone cancer. As analgesics can also influence disease progression, findings from these studies may lead to therapies that have the potential to improve the quality of life and survival of patients with skeletal malignancies.

Cyclooxygenase-2 as a target for anticancer drug development

The two isoforms cyclooxygenase-1 and -2 catalyze the initial step in the formation of prostaglandins in a variety of pathophysiological processes. More recently their role in carcinogenesis has become more evident. They seem to influence apoptosis, angiogenesis, and invasion, and play a role in the production of carcinogens. Usually, a high level of COX-2 expression is found in cancer cells. However, low COX-2 expression is observed in some cancers like prostate or breast cancer. This phenomenon is quite surprising and should influence on clinical trial designs. Large epidemiological trials studying users and non-users of aspirin have shown that cyclooxygenase (COX) inhibitors and non-steroidal anti-inflammatory drugs (NSAIDs) could be of benefit against the development and growth of malignancies. Moreover, clinical trials in patients with familial adenomatosis polyposis syndrome have shown too the efficacy of non-selective COX inhibitors and recently also of selective COX-2 inhibitors in the reduction of the number and the size of colorectal polyps. However, a primary chemopreventive effect has not been demonstrated yet. NSAIDs are also supposed to have a preventive and growth inhibitory effect in extra-colonic epithelial malignancies. Several preclinical studies show promising results with combination treatments of either chemotherapy or radiotherapy with COX inhibitors. Preclinical studies with the simultaneous use of inhibitors of the epidermal growth factor receptor and COX-2 inhibitors have shown also promising results. Encouraging results with the first clinical trials combining chemotherapy with COX-2 inhibitors in patients with cancer in the advanced and neoadjuvant setting have recently been reported. However, NSAIDs effects in cancer cells are mediated not only by COX enzymes but also by interactions with downstream effectors of COX-2. Hence, we can state that targeting the COX-2 pathway is a promising strategy in the prevention and treatment of solid tumors. Ongoing trials are expected to answer - at least partly - the remaining questions concerning COX-2 and cancer.

Celecoxib Versus Placebo for Men With Prostate Cancer and a Rising Serum Prostate-Specific Antigen After Radical Prostatectomy and/or Radiation Therapy

Purpose

To assess the biologic activity of celecoxib, a selective cyclooxygenase-2 inhibitor, in men with recurrent prostate cancer using change in prostate-specific antigen (PSA) doubling time (PSADT) as the primary outcome variable.

Patients and Methods

Participants had histologically confirmed prostate cancer, no recent hormone therapy, rising serum PSA after radical prostatectomy and/or radiation therapy, and no radiographic evidence of metastases. Patients were randomly assigned to celecoxib (400 mg by mouth twice daily) or placebo. Treatment continued until disease progression or until adverse effects stopped treatment. A positive outcome was defined as post-treatment PSADT of more than 200% baseline PSADT with no new metastases.

Results

The study was terminated early after information about the cardiovascular safety of celecoxib prompted review of ongoing clinical studies. Before discontinuation of the study, 78 men were assigned randomly to either celecoxib or placebo. Eight (20%) of 40 men in the placebo group and 15 (40%) of 38 men in the celecoxib group had post-treatment PSADT of more than 200% of baseline PSADT with no new metastases (P = .08). Mean PSA velocity increased by 3.0% for the placebo group and decreased by 3.4% for the celecoxib group (P = .02).

Conclusion

Although the primary efficacy objective was not met, this study provides some evidence for biologic activity of celecoxib in prostate cancer. Compared with placebo, celecoxib significantly decreased mean PSA velocity and tended to increase the proportion of men who doubled their PSADT.

Elevated 12- and 20-hydroxyeicosatetraenoic acid in urine of patients with prostatic diseases

The role of eicosanoids (metabolites of arachidonic acid) in prostate diseases is receiving increased attention. We investigated the relationship between the concentrations of urinary free acids of 12- and 20-hydroxyeicosatetraenoic acids (12- and 20-HETE) and the benign prostatic hypertrophy (BPH) and prostate cancer (Pca). Urinary concentrations of 12-HETE and 20-HETE of BPH and Pca patients were significantly higher than normal subjects. After removal of the prostate gland, the urinary concentrations of these eicosanoids decreased to concentrations similar to the normal subjects. These results suggest that urinary free acids of 12-HETE and 20-HETE indicate an abnormality of the prostate gland.

Cyclooxygenase-2 (cox-2) expression is an independent predictor of prostate cancer recurrence

Lack of reliable prognostic markers hinders accurate prediction of disease progression in prostate cancer. The inducible proinflammatory enzyme cyclooxygenase-2 (COX-2) is implicated in prostate carcinogenesis, but its role in cancer progression is less clear. We examined whether COX-2 expression evaluated by immunohistochemistry (IHC) in radical prostatectomy (RP) specimens can predict biochemical recurrence. Archival prostate cancer specimens (n = 60) were obtained from patients who underwent RP, but had not received neoadjuvant hormonal therapy. Twenty-three patients had biochemical or clinical recurrence (mean time of recurrence: 38.2 months), and 37 patients were recurrence free (mean follow-up: 95 months). COX-2 expression was determined by IHC, using an anti-COX-2 antibody. Three individuals scored the staining independently, as high- or low-expression. COX-2 was expressed in prostate cancer cells, in adjacent normal glands and in specimens from patients who later progressed. At 62-months follow-up, COX-2 staining predicted progression with 82.4% sensitivity and 81.3% specificity. Sensitivity (86.4%) and specificity (86.7%) improved at > or = 100-months follow-up. In univariate analysis, Gleason score, preoperative PSA, extraprostatic extension, margin, seminal vesicle invasion, and high COX-2 expression were significant predictors of biochemical recurrence (p < 0.05). In multivariate analysis, preoperative PSA (hazard ratio/unit PSA change 1.080; p = 0.0036) and COX-2 expression (hazard ratio 16.442; p < 0.0001) were independent prognostic indicators. Patients with PSA > 7 ng/ml and high COX-2 expression had the highest probability of recurrence (Kaplan-Meier analysis). COX-2 expression is an independent predictor of prostate cancer progression following RP and underscores the significance of inflammatory factors in this process.

Genomics of prostate cancer: Is there anything to „translate”?

This review provides an up-dated collection of data concerning the genetic and epigenetic changes during development, growth and progression of prostate cancer. Hereditary and susceptibility factors have a long list, similarly to the expression of single genes connected to various cell functions. It was a hope that covering a large set of genes, array technologies would clarify very rapidly the role of genetics in malignant diseases, offering targets for molecular diagnostics and therapy. The power of high-throughput techniques for the detection and global analysis of gene expression is unquestionable, interesting, astonishing as well as puzzling data have already been obtained. However, the standardization of the procedures is still missing and the reproducibility is rather low in many instances. Moreover, the different array methods can select different gene expression profiles, which makes the decision rather difficult. Another important question is, coming again from the array technologies, how far the genotype (the gene profiles or fingerprints) can reflect the actual phenotype in a highly complex and readily changing disease as cancer. Proteomics will provide a closer look to this seemingly unanswerable problem. We are at the beginning of the exploration of the behavior of cancer cells in order to apply a more effective therapy based on a more reliable set of diagnostic and prognostic informations.

The role of lipoxygenase-isoforms in atherogenesis

Lipoxygenases (LOXs) form a heterogeneous family of lipid-peroxidizing enzymes, and several LOX-isoforms (12/15-LOX, 5-LOX) have been implicated in atherogenesis. However, the precise role of these enzymes is still a matter of discussion. 12/15-LOXs are capable of oxidizing lipoproteins (low-density lipoprotein (LDL), high-density lipoprotein (HDL)) to atherogenic forms, and functional inactivation of this enzyme in murine atherosclerosis models slows down lesion formation. In contrast, rabbits that overexpress this enzyme were protected from lesion formation when fed a lipid-rich diet. To contribute to this discussion, we recently investigated the impact of 12/15-LOX overexpression on in vitro foam cell formation. When 12/15-LOX-transfected J774 cells were incubated in culture with modified LDL, we found that intracellular lipid deposition was reduced in the transfected cells when compared with the corresponding control transfectants. This paper briefly summarizes the current status of knowledge on the biological activity of different LOX-isoforms in atherogenesis and will also provide novel experimental data characterizing the role of 12/15-LOX in cellular LDL modification and for in vitro foam cell formation.

The use of genetically engineered mouse models of prostate cancer for nutrition and cancer chemoprevention research

The ability to modify the expression of specific genes in the mouse through genetic engineering technologies allows for the generation of previously unavailable models for prostate cancer prevention research. Although animal models have existed for some time for the study of prostate cancer prevention (primarily in the rat), it is uncertain if the mechanisms that drive prostate carcinogenesis in these models are relevant to those in human prostate cancer. Cell culture studies are of limited usefulness because the conditions are inherently artificial. Factors such as relevant physiologic concentrations and metabolism of putative chemoprevention compounds are difficult to model in an in vitro system. These studies also preclude the types of interactions known to occur between multiple cell types in vivo. In addition, all prostate cancer cell lines are already highly progressed and are not representative of the type of cells to which most preventive strategies would be targeted. Due to the advent of genetically engineered mouse (GEM) models, we now have models of prostate cancer that are dependent on molecular mechanisms already implicated in human prostate carcinogenesis. With these models we can perform a variety of experiments that could previously only be done in cell culture or in prostate cancer cell line xenografts. The currently available GEM models of prostate cancer have been extensively reviewed therefore, this review will focus on the types of models available and their usefulness for various types of preclinical studies relevant to prostate cancer prevention.

Non-steroidal anti-inflammatory drugs for the prevention and treatment of cancer

Non-steroidal anti-inflammatory drugs (NSAIDs), both cyclooxygenase-2 (COX-2) selective and nonselective inhibitors, are amongst the most popular medications worldwide. Whilst their anti-inflammatory effect is well known, recent studies have demonstrated an unexpected effect in both the prevention and treatment of several types of cancer. The anticancerous effect of NSAIDs is believed to be mainly due to the inhibition of COX-2, which is overexpressed in many types of cancer and may play a major role in tumourigenesis. In this review, we will describe the possible mechanisms for NSAIDs anticancer effect and summarize the major clinical studies in cancer prevention and treatment. We will also discuss the effect of the recent reports of adverse cardiovascular effects on anticancer research of the selective COX-2 inhibitors.

Cyclooxygenase-2 expression correlates with local chronic inflammation and tumor neovascularization in human prostate cancer

PURPOSE

Chronic inflammation is linked to the development of cancer in several organs, including the prostate. Up-regulated cyclooxygenase-2 (COX-2) may play a role in influencing cell proliferation, differentiation, apoptosis, or angiogenesis. This study aimed to derive data from human prostate cancer to investigate whether chronic inflammation and angiogenesis were correlated with the expression of COX-2.

EXPERIMENTAL DESIGN

In this study, we did double-immunohistochemical analysis of a set of 43 human prostate cancer for COX-2 expression and the correlation with T-lymphocyte and macrophage densities and CD31-marked microvessel density (MVD) in situ.

RESULTS

COX-2 positive staining was detected in 40/43 cancer samples with the very heterogeneous expression. Elevated COX-2 expression was associated with high Gleason score (P = 0.002). Foci of chronic inflammation were found in all 43 samples. COX-2-positive areas were noted with high T-lymphocyte and macrophage densities than COX-2-negative tumor areas (P < 0.0001 and P = 0.001, respectively). MVD were also found higher in COX-2-positive areas than in COX-2-negative tumor areas (P = 0.001).

CONCLUSIONS

This study shows a novel relationship between COX-2 expression and the local chronic inflammation within prostate cancer and the increased angiogenesis. It is likely that the proinflammatory cytokines, released by T-lymphocytes and macrophages, up-regulate COX-2 in adjacent tumor cells and stimulate the angiogenesis in stromal tissues. These findings suggest that COX-2 may be an effective therapeutic target in prostate cancer treatment.

Resistance of prostate cancer cell lines to COX-2 inhibitor treatment

Targeting of cyclooxygenase-2 (COX-2) for cancer chemoprevention is well supported for several tumor types, most notably colon cancer. In contrast, the data for its role in prostate cancer carcinogenesis are correlative only. Thus, we compared the COX-2 expression, activity, and effects of inhibition in prostate cancer cells on COX-2-dependent colon cancer cells. COX-2 levels in benign and malignant human prostate tissue were determined by immunohistochemistry. Compared to colon cancer cells, prostate cancer cells expressed lower levels of COX-2, produced less PGE2, and were resistant to selective COX-2 inhibition. Examination of benign prostatic epithelium from prostatectomy samples demonstrated rare foci of COX-2. Whereas, human prostate cancer sections were uniformly negative for COX-2. In conclusion, these studies indicate the lack of a putative role for COX-2 in prostate cancer development. Direct evidence for the involvement of COX-2 in prostate cancer carcinogenesis is desperately needed.

Nonsteroidal anti-inflammatory drugs and risk of prostate cancer in the Baltimore Longitudinal Study of Aging

BACKGROUND

Laboratory and epidemiologic studies suggest that aspirin and nonaspirin nonsteroidal anti-inflammatory drugs (NSAID) reduce the risk of cancer, possibly via inhibition of the cyclooxygenase enzymes. We evaluated the association of aspirin and nonaspirin NSAIDs with subsequent prostate cancer in a prospective study. We also assessed whether use of these drugs influences serum prostate-specific antigen (PSA) concentration.

METHODS

Participants were 1,244 male members of the Baltimore Longitudinal Study of Aging. Use of prescription and over-the-counter drugs was collected by questionnaire and interview at multiple study visits. One hundred forty-one prostate cancer cases diagnosed between 1980 and May 2004 were confirmed by medical record review. We used Cox proportional hazards regression to estimate the rate ratio (RR) of prostate cancer updating drug use over time and taking into account age and year. We used generalized estimating equations to calculate age-adjusted geometric mean PSA concentration by aspirin or nonaspirin NSAIDs use among 933 of the men without prostate cancer, for whom 3,749 PSA measurements in archived sera had been done previously.

RESULTS

On 46.0% and 21.5% of the visits, current use of aspirin or nonaspirin NSAIDs (mostly ibuprofen) was reported, respectively. The RRs of prostate cancer comparing ever to never use were 0.76 [95% confidence interval (95% CI), 0.54-1.07] for aspirin, 0.79 (95% CI, 0.54-1.16) for nonaspirin NSAIDs, and 0.71 (95% CI, 0.49-1.02) for either medication. The association for ever use of either aspirin or nonaspirin NSAIDs was suggestively more pronounced in men <70 years (RR, 0.54; 95% CI, 0.27-1.03) than in men >/=70 years (RR, 0.78; 95% CI, 0.50-1.22; P(interaction) = 0.73). The RR for current use of either drug was attenuated relative to ever use. Mean PSA concentration did not differ between users and nonusers of either aspirin or nonaspirin NSAIDs (1.01 versus 0.98 ng/mL, P = 0.56).

CONCLUSION

In this prospective study, men, in particular younger men, who had ever used aspirin or nonaspirin NSAIDs had a modest nonstatistically significant lower risk of prostate cancer. The modest inverse association was unlikely due to detection bias that might have resulted if anti-inflammatory drugs had influenced serum PSA concentration.

Overexpression of 12/15-lipoxygenase, an ortholog of human 15-lipoxygenase-1, in the prostate tumors of TRAMP mice

Changes in the expression and activity of lipid-metabolizing enzymes, including the linoleic acid (LA)-metabolizing enzyme 15-lipoxygenase-1 (15-LO-1), may play a role in the development and progression of human prostate carcinoma (PCa). We reported that human 15-LO-1 (designated as leukocyte type 12-LO or 12/15-LO in mouse) is expressed in human prostate and increased in PCa, particularly high-grade PCa. Genetically engineered mouse (GEM) models of PCa could facilitate the study of this gene and its regulation and function in PCa progression. In this study, we examine the protein expression and enzyme activity levels of 12/15-LO associated with PCa progression in the TRansgenic Adenocarcinoma of Mouse Prostate (TRAMP) model of PCa. This GEM model develops prostatic intraepithelial neoplasia (PIN), followed by invasive gland-forming PCa and invasive and metastatic less differentiated PCa, with neuroendocrine (NE) differentiation (NE Ca). In the wild-type and TRAMP prostates, the most prominent LA metabolite was 13-hydroxyoctadecadienoic acid (13-HODE). Lesser amounts of 12-hydroxyeicosatetraenoic acid and 15-hydroxyeicosatetraenoic acid (HETE) were made from arachidonic acid (AA). In TRAMP prostates, 12/15-LO activity was increased compared to wild type at 20, 29, 39, and 49 weeks, as assessed by LA conversion to 13-HODE, and by AA conversion to 12/15-HETE, respectively. Immunostaining demonstrated that the increased capacity to generate 13-HODE was paralleled by an increase in neoplastic epithelial expression of 12/15-LO in PIN and invasive carcinomas. In conclusion, although there is a basal 12/15-LO activity in the wild-type mouse prostate, there is a marked increase in the expression of 12/15-LO with TRAMP PCa progression, paralleling our previously reported increased expression of the ortholog 15-LO-1 in high-grade human PCa. Thus, 12/15-LO and LA metabolism in the TRAMP model shares similarities to human PCa, and may allow to confirm a role for LA metabolism and other biologic functions of 15-LO-1 in human PCa. In addition, the TRAMP model will serve as a tool for testing the suitability of 12/15-LO-and ultimately human 15-LO--as a therapeutic target during PCa progression.

Celecoxib Inhibits Prostate Cancer Growth: Evidence of a Cyclooxygenase-2-Independent Mechanism

PURPOSE

Selective cyclooxygenase-2 (COX-2) inhibitors may suppress carcinogenesis by both COX-2-dependent and COX-2-independent mechanisms. The primary purpose of this study was to evaluate whether celecoxib or rofecoxib, two widely used selective COX-2 inhibitors, possess COX-2-independent antitumor activity.

EXPERIMENTAL DESIGN

PC3 and LNCaP human prostate cancer cell lines were used to investigate the growth inhibitory effects of selective COX-2 inhibitors in vitro. To complement these studies, we evaluated the effect of celecoxib on the growth of PC3 xenografts.

RESULTS

COX-1 but not COX-2 was detected in PC3 and LNCaP cells. Clinically achievable concentrations (2.5-5.0 micromol/L) of celecoxib inhibited the growth of both cell lines in vitro, whereas rofecoxib had no effect over the same concentration range. Celecoxib inhibited cell growth by inducing a G(1) cell cycle block and reducing DNA synthesis. Treatment with celecoxib also led to dose-dependent inhibition of PC3 xenograft growth without causing a reduction in intratumor prostaglandin E(2). Inhibition of tumor growth occurred at concentrations (2.37-5.70 micromol/L) of celecoxib in plasma that were comparable with the concentrations required to inhibit cell growth in vitro. The highest dose of celecoxib led to a 52% reduction in tumor volume and an approximately 50% decrease in both cell proliferation and microvessel density. Treatment with celecoxib caused a marked decrease in amounts of cyclin D1 both in vitro and in vivo.

CONCLUSIONS

Two clinically available selective COX-2 inhibitors possess different COX-2-independent anticancer properties. The anticancer activity of celecoxib may reflect COX-2-independent in addition to COX-2-dependent effects.

Cyclooxygenases in cancer: progress and perspective

Aspirin has been used to control pain and inflammation for over a century. Epidemiological studies first associated a decreased incidence of colorectal cancer with the long-term use of aspirin in the early 1980s. Near the same time the first reports showing regression of colorectal adenomas in response to the non-steroidal anti-inflammatory drug (NSAID) sulindac were reported. In subsequent years, the use of other NSAIDs, which inhibit cyclooxygenase (COX) enzymes, was linked to reduced cancer risk in multiple tissues including those of the breast, prostate, and lung. Together these studies resulted in the identification of a new cancer preventive and/or therapeutic target-COX enzymes, especially COX-2. Meanwhile, the overexpression of COX-2, and less consistently, the upstream and downstream enzymes of the prostaglandin synthesis pathway, was demonstrated in multiple cancer types and some pre-neoplastic lesions. Direct interactions of prostaglandins with their receptors through autocrine or paracrine pathways to enhance cellular survival or stimulate angiogenesis have been proposed as the molecular mechanisms underlying the pro-carcinogenic functions of COX-2. The rapid development of safe and effective inhibitors targeting individual COX enzymes not only dramatically improved our understanding of the function of COX-2, but also resulted in discovery of COX independent functions of NSAIDs, providing important hints for future drug design. Here we review the fundamental features of COX enzymes, especially as related to carcinogenesis, their expression and function in both animal tumor models and clinical cancers and the proposed mechanisms behind their roles in cancer.

COX-2 inhibitors and other nonsteroidal anti-inflammatory drugs in genitourinary cancer

Selective cyclooxygenase (COX)-2-inhibiting and other nonsteroidal anti-inflammatory drugs (NSAIDs) show promise for preventing and treating bladder and prostate cancers. In contrast to the strong NSAID epidemiology in colorectal cancer, the epidemiologic data on NSAIDs and genitourinary (GU) cancers are limited and mixed. However, a substantial body of preclinical in vitro and in vivo animal model data shows consistent NSAID activity in treating, and in some cases preventing, GU cancers and begins to address the mechanisms behind this activity (eg, involving Akt and ERK2 in the prostate). Many preclinical and clinical NSAID studies currently under way are helping to resolve the best type (selective or nonselective COX inhibitors or non-COX inhibitors), dose and duration of NSAID treatment for prevention in the GU setting. Future studies likely will focus on clarifying the NSAID mechanisms behind and developing NSAID combinations for both treating and preventing GU cancers.

Approaches to understanding the importance and clinical implications of peroxisome proliferator-activated receptor gamma (PPARgamma) signaling in prostate cancer

The development and maintenance of the prostate are dependent upon a complex series of interactions occurring between the epithelial and stromal tissues (Hayward and Cunha [2000]: Radiol. Clin. N. Am. 38:1-14). During the process of prostatic carcinogenesis, there are progressive changes in the interactions of the nascent tumor with its surrounding stroma and extracellular matrix. These include the development of a reactive stromal phenotype and the possible promotion, by stromal cells, of epithelial proliferation and loss of differentiated function (Hayward et al. [1996]: Ann. N. Y. Acad. Sci. 784:50-62; Grossfeld et al. [1998]: Endocr. Related Cancer 5:253-270; Rowley [1998]: Cancer Metastasis Rev. 17:411-419; Tuxhorn et al. [2002]: Clin. Cancer Res. 8:2912-2923). Many molecules play an as yet poorly defined role in establishing and maintaining a growth quiescent glandular structure in the adult. Peroxisome proliferator-activated receptor gamma (PPARgamma) is a candidate regulator of prostatic epithelial differentiation and may play a role in restricting epithelial proliferation. PPARgamma agonists are relatively non-toxic and have been used with limited success to treat some prostate cancer patients. We would propose that a more complete understanding of PPARgamma biology, particularly in the context of appropriate stromal-epithelial and host-tumor interactions would allow for the selection of patients most likely to benefit from this line of therapy. In particular, it seems reasonable to suggest that the patients most likely to benefit may be those with relatively indolent low stage disease for whom this line of therapy could be a useful additive to watchful waiting.

Subcellular localization and tumor-suppressive functions of 15-lipoxygenase 2 (15-LOX2) and its splice variants

15-Lipoxygenase 2 (15-LOX2), the most abundant arachidonate (AA)-metabolizing enzyme expressed in adult human prostate, is a negative cell-cycle regulator in normal human prostate epithelial cells. Here we study the subcellular distribution of 15-LOX2 and report its tumor-suppressive functions. Immunocytochemistry and biochemical fractionation reveal that 15-LOX2 is expressed at multiple subcellular locations, including cytoplasm, cytoskeleton, cell-cell border, and nucleus. Surprisingly, the three splice variants of 15-LOX2 we previously cloned, i.e. 15-LOX2sv-a/b/c, are mostly excluded from the nucleus. A potential bi-partite nuclear localization signal (NLS),203RKGLWRSLNEMKRIFNFRR221, is identified in the N terminus of 15-LOX2, which is retained in all splice variants. Site-directed mutagenesis reveals that this putative NLS is only partially involved in the nuclear import of 15-LOX2. To elucidate the relationship between nuclear localization, enzymatic activity, and tumor suppressive functions, we established PCa cell clones stably expressing 15-LOX2 or 15-LOX2sv-b. The 15-LOX2 clones express 15-LOX2 in the nuclei and possess robust enzymatic activity, whereas 15-LOX2sv-b clones show neither nuclear protein localization nor AA-metabolizing activity. To our surprise, both 15-LOX2- and 15-LOX2sv-b-stable clones proliferate much slower in vitro when compared with control clones. More importantly, when orthotopically implanted in nude mouse prostate, both 15-LOX2 and 15-LOX2sv-b suppress PC3 tumor growth in vivo. Together, these results suggest that both 15-LOX2 and 15-LOX2sv-b suppress prostate tumor development, and the tumor-suppressive functions apparently do not necessarily depend on AA-metabolizing activity and nuclear localization.

Primary culture model of peroxisome proliferator-activated receptor gamma activity in prostate cancer cells

BRL 49653 (rosiglitazone) is a thiazolidinedione anti-diabetic drug that activates the nuclear receptor, peroxisome proliferator-activated receptor gamma (PPARgamma). Pilot clinical trials have shown evidence of therapeutic activity of PPARgamma agonists against prostate cancer. To more effectively use PPARgamma ligands to treat this common and generally chemo-resistant type of cancer, it will be necessary to better understand the nature of PPARgamma activity in prostate cancer cells. Tumor suppressor effects of activation of PPARgamma may include suppression of growth and/or induction of differentiation or apoptosis. We investigated responses of primary cultures of human prostatic cancer cells to BRL 49653. PPARgamma was expressed in all of the cell strains examined. BRL 49653 caused dose- and time-dependent growth inhibition that was associated with increased expression of the transcription repressor, transforming growth factor beta-stimulated clone 22 (TSC-22), and markedly increased expression of the secretory differentiation-associated gene adipophilin. Adipocyte-type fatty acid binding protein (aFABP), neutrophil gelatinase-associated lipocalin (NGAL), glycerol kinase (GyK), and beta-catenin, which are regulated by PPARgamma ligands in certain other types of cells, were not regulated by BRL 49653 in prostate cells. Upregulation of adipophilin coincided with morphological changes and the appearance of cytoplasmic vacuoles with ultrastructural features of secondary lysosomes. These results extend previous studies with established cancer cell lines and show that PPARgamma agonists can inhibit proliferation and modulate expression of secretory-associated genes in primary cultures of prostate cancer cells, further warranting consideration of these agents as pro-differentiating chemotherapeutic or chemoprevention agents for the treatment of prostate cancer.

Requirement of cyclooxygenase-2 expression and prostaglandins for human prostate cancer cell invasion

The PC-3 Low Invasive cells and the PC-3 High Invasive cells were used to investigate the correlation of the COX-2 expression and its arachidonic acid metabolites, prostaglandins, with their invasiveness through Matrigel using a Boyden chamber assay. The COX-2 expression in PC-3 High Invasive cells was approximately 3-fold higher than in PC-3 Low Invasive cells while the COX-1 expression was similar in both cell sublines. When incubated with arachidonic acid, PGE2 was the major prostaglandin produced by these cells. PC-3 High Invasive cells produced PGE2 approximately 2.5-fold higher than PC-3 Low Invasive cells. PGD2 was the second most abundant prostaglandin produced by these cells. Both indomethacin (a nonspecific COX inhibitor) and NS-398 (a specific COX-2 inhibitor) inhibited the production of prostaglandins and the cell invasion. PGE2 alone did not induce the cell invasion of PC-3 Low Invasive cells. However, PGE2 reversed the inhibition of cell invasion by NS-398 and enhanced the cell invasion of the PC-3 High Invasive cells. In contrast, PGD2 slightly inhibited the cell invasion. These results suggest that in the PC-3 Low Invasive cells, COX-2-derived PGE2 may not be sufficient to induce cell invasion while in the PC-3 High Invasive cells, PGE2 may be sufficient to act as an enhancer for the cell invasion. Further, PGD2 may represent a weak inhibitor and counteracts the effect of PGE2 in the cell invasion.

Cyclooxygenase 2 selective inhibitors in cancer treatment and prevention

Prostaglandin synthesis by a number of enzymes is important at all stages during the genesis of cancer. The availability of prostaglandin H(2) as a substrate for prostaglandin production is a critical control point in its synthesis. Cyclooxygenase (COX) occurs in two forms (COX-1 and -2) and acts as the rate-limiting enzyme that generates prostaglandin H(2). COX-1 is produced as a steady-state enzyme, while COX-2 is heavily involved in inflammation and tumorigenesis. Differences in the catalytic sites of these enzymes are utilised to generate COX-2 selective inhibitors. Certain chemical characteristics of non-steroidal anti-inflammatory drugs and COX-2 selective inhibitors make some of these inhibitors more effective against COX-2 than others. Epidemiological, animal and preclinical data demonstrate the promise of non-steroidal anti-inflammatory drugs and COX-2 selective inhibitors as anticancer agents. Ongoing clinical trials are designed to determine the efficacy of non-steroidal anti-inflammatory drugs and COX-2 selective inhibitors in the prevention and treatment of many types of cancer.

Cyclooxygenase-2 promotes prostate cancer progression

BACKGROUND

Cyclooxygenase (COX) -2, an inducible isoform of COX, has been observed to be expressed in prostate cancer. Several studies have reported that COX-2 overexpression is associated with carcinogenesis, cell growth, angiogenesis, apoptosis, and invasiveness in a variety of tumor types.

METHODS

To investigate the function of COX-2 in prostate cancer directly, we stably transfected human full-length COX-2 cDNA into LNCaP cells (LNCaP-COX-2), which express low levels of endogenous COX-2.

RESULTS

The level of COX-2 mRNA and protein and the COX activity in COX-2 LNCaP-COX-2 cells was significantly increased compared with parent and control-transfected cells. Overexpression of COX-2 increased both proliferation in vitro and tumor growth rate in vivo. However, the pro-tumor effect was neither associated with changes of androgen receptor (AR) expression level nor AR activity. Furthermore, addition of the major metabolites of COX-2-mediated arachidonic acid metabolism did not alter the proliferation of LNCaP-COX-2 cells in vitro. LNCaP-COX-2 cells had increased secretion of vascular endothelial growth factor (VEGF) protein, suggesting that angiogenesis induced by COX-2 stimulates tumor growth in vivo.

CONCLUSION

These data demonstrate that COX-2 contributes to prostate cancer progression and suggest that it mediates this effect, in part, through increased VEGF.

The effect of 15-lipoxygenase-1 expression on cancer cells

Lipoxygenases oxidatively metabolize polyunsaturated fatty acids to a rich spectrum of biologically active products. One enzyme of the lipoxygenase family, Arachidonate 15-lipoxygenase-1 (arachidonate:oxygen 15-oxidoreductase, EC 1.13.11.33), is implicated in several forms of epithelial cell cancers, and provides a rationale for exploring its role in the progression and metastasis of cancers. Thus, 15-LO-1 could be a marker of the growth and spread of cancers. The importance of 15-LO-1 expression is imparted by its metabolic product of linoleic acid, yielding 13-(S)-hydroxyoctadecadienoic acid (13-(S)-HODE). In order to maximize our understanding of the roles of lipoxygenases and cyclooxygenases in cancer, it is necessary to correlate their metabolic pathways to the respective expression levels, and not exaggerate the presence or absence of an enzyme or its function when it clearly is not there. It is also important to acknowledge that some forms of these enzymes may not even be relevant to human disease. Although it is unlikely that any single gene is sufficient to account for the complex etiology of cancer, 15-LO-1 overexpression is clearly a key component in the cell proliferation process. This article is divided into three sections emphasizing the key role of 15-LO-1 in prostate, colorectal, and breast cancers.

Molecular mechanisms of cancer pain

Pain is the most disruptive influence on the quality of life of cancer patients. Although significant advances are being made in cancer treatment and diagnosis, the basic neurobiology of cancer pain is poorly understood. New insights into these mechanisms are now arising from animal models, and have the potential to fundamentally change the way that cancer pain is controlled.

An immunohistochemical survey of nine cases of medullary carcinoma of thyroid including reactivity for Cox-1 and Cox-2 enzymes

There has been much recent investigation of the cyclooxygenase (Cox) enzymes in tumor biology, but, to our knowledge, no study has yet been published describing Cox activity in medullary carcinoma of the thyroid (MTC). Nine cases of MTC from the past 10 yr were retrieved from our hospital archives. Slides cut from formalin-fixed paraffin-embedded tumor tissue from these cases were assessed for the activities of Cox-1 and Cox-2 enzymes by immunohistochemistry as well as by a battery of immunohistochemical stains for intermediate filaments, peptide hormone, and proliferation and promoter antigens. The staining reactions were semiquantitatively assessed and scored for comparison with each other as well as with each patient s clinical presentation and course. Staining for Cox-1 and Cox-2 enzymes was present only in tumorous tissue, not in nontumorous thyroid tissue or C-cells. Cox-2 staining was not consistently increased over Cox-1 staining; however, Cox-2 staining bore statistically significant correlations with the expression of low molecular weight keratin, thyroid-transforming factor-1, topoisomerase, and MIB1. Hyperplastic C-cells from patients with diverse physiologic conditions and from three patients with C-cell hyperplasia accompanying medullary carcinoma or multiple endocrine neoplasia type IIa showed no reactivity for the Cox antibodies. It appears that Cox enzyme immunoreactivity is present only in the neoplastic C-cells of medullary carcinoma, but with variable expression. A practical application of the preceding finding might involve the use of Cox staining to distinguish invasive medullary carcinoma cells from hyperplastic C-cells.