Cystic duct dilatations and proliferative epithelial lesions in mouse mammary glands upon keratin 5 promoter-driven overexpression of cyclooxygenase-2

Chemoprophylactic activity of nitazoxanide in experimental model of mammary gland carcinoma in rats

The current study focuses on the evaluation of the chemoprophylactic activity of nitazoxanide against the mammary gland carcinoma in experimental rats. The experimental protocol involves total 50 female Wistar albino rats of body weight 120-150 g, which were randomly categorized into five groups; Normal control (1% w/v carboxymethyl cellulose, p.o.); Toxic control (N-methyl-N-nitrosourea, MNU, 47 mg/kg i.v.); Standard (MNU, 47 mg/kg i.v. + tamoxifen, 1 mg/kg p.o.); Treatment 1 (MNU, 47 mg/kg i.v. + NTZ low-dose, 25 mg/kg p.o.); and Treatment 2 (MNU, 47 mg/kg, i.v. + NTZ high-dose, 50 mg/kg p.o.). The mammary gland carcinoma was induced by a single tail vein intravenous injection of MNU at a 47 mg/kg dose. Seven days after MNU administration, daily dosing of nitazoxanide and tamoxifen was initiated till 110th day in respective groups. The MNU toxicity was apparent with the altered electrocardiogram and heart rate variability, increased number of alveolar bud count, differentiation score, and upregulated antioxidant parameters. Nitazoxanide treatment restored the histological architecture in rats along with the reduction of alveolar buds and downregulation of oxidative stress markers as well as inflammatory markers. Therefore, nitazoxanide can be utilized as a potential chemoprophylactic agent against mammary gland carcinoma induced by MNU.

Angelica sinensis Supercritical Fluid CO2 Extract Attenuates D-Galactose-Induced Liver and Kidney Impairment in Mice by Suppressing Oxidative Stress and Inflammation

Angelica sinensis (AS, Danggui in Chinese) is an important herbal component of various traditional formulae for the management of asthenia and its tonic effects. Although AS has been shown to ameliorate cognitive damage and nerve toxicity in D-galactose (D-gal)-elicited senescent mice brain, its effects on liver and kidney injury have not yet been explored. In this work, mice were subjected to hypodermic injection with D-gal (200 mg/kg) and orally gavaged with AS (20, 40, or 80 mg/kg) once a day for 8 successive weeks. Results revealed that AS significantly improved liver and kidney function as assessed by organ index and functional parameters. In addition, AS pretreatment effectively ameliorated the histological deterioration. AS attenuated the MDA level and markedly enhanced the activities and gene expressions of antioxidative enzymes, namely Cu, Zn-SOD, CAT, and GPx. Furthermore, AS markedly inhibited the D-gal-mediated increment of expressions of inflammatory cytokines iNOS, COX-2, IκBα, p-IκBα, and p65 and promoted the IκBα expression level in both hepatic and renal tissues. In sum, AS pretreatment could effectively guard the liver and kidney of mice from D-gal-induced injury, and the underlying mechanism was deemed to be intimately related to attenuating oxidative response and inflammatory stress.

Comparative pharmacokinetics study of anastrozole after single administration and combination with celecoxib

1. There are numerous investigations demonstrating that the cyclooxygenase-2 (COX-2) inhibitors might enhance the efficiency of anastrozole in breast cancer. Hence, this study was conducted to investigate the comparative pharmacokinetics of anastrozole after single administration and combination with celecoxib. 2. A simple protein precipitation procedure was adopted for the sample preparation with satisfactory extraction recovery for both anastrozole and the internal standard, and then anastrozole was separated and analysed on an ACQUITY BEH UPLC C₁₈ column (50 × 2.0 mm, 1.7 μm, Waters) within 2 min. The calibration curves showed good linarites (r = 0.994). Intra- and inter-day precision were within 4.93 and 13.83%, respectively. The mean extraction recoveries across QC levels were within 91.4%, and the matrix effects were within 94.5%. 3. Results showed that the method was reliable to determine anastrozole in rat plasma. Compared with rats in single administration group, no significant difference was found in the combination group. It is workable to use celecoxib combined with anastrozole in clinical therapy.

Effect of β-sitosterol against methyl nitrosourea-induced mammary gland carcinoma in albino rats

BACKGROUND

The present study was in quested to study the effects of β-sitosterol on methyl nitrosourea (MNU) induced mammary gland carcinoma in albino wistar rats.

METHODS

Animals were randomized and divided into four groups of eight animals each. Group I (sham control 1 % CMC in normal saline p.o.); Group II (toxic control, MNU 47 mg/kg, i.v); Group III (MNU 47 mg/kg, i.v + β-sitosterol, 10 mg/kg, p.o); Group IV (MNU 47 mg/kg, i.v + β-sitosterol, 20 mg/kg, p.o). Toxicity was induced by single i.v. injection of MNU followed by β-sitosterol supplementation therapy for 115 days at the dose mentioned above.

RESULTS

Treatment with β-sitosterol evidenced decrease in the alveolar bud and lobule score in the whole mount of the mammary gland. β-sitosterol exhibited diminishing effect on oxidative stress through synchronizing lipid and enzymatic antioxidant defense. A significant decrease in the saturated and unsaturated fatty acid was evident with the MNU treatment and β-sitosterol demonstrated a marked effect on it. Pgp 9.5 expression was dose dependently upregulated by β-sitosterol treatment in comparison to MNU treatment. On the contrary, downregulated NF-kB expression was perceived, when β-sitosterol was concomitantly administered with MNU.

CONCLUSION

β-sitosterol afforded significant protection against the deleterious effects of MNU.

Hepatoprotective effect of the flavonoid fraction isolated from the flower of Inula britannica against D-Galactosamine-induced hepatic injury

The aim of this study was to investigate the mechanism and nature of the protective effect of Inula britannica flower flavonoids (IBFF) on antioxidants and the inhibition of inflammation in liver injury. Liver injury was induced in a mouse model by intraperitoneal injection of D-Galactosamine (D-Gal; 850 mg/kg) and IBFF was administered orally at 125, 250 or 500 mg/kg once a day for 7 days. The results revealed that IBFF reversed the increases in serum aminotransferase levels and lipid peroxidation and also reversed the decreases in hepatic glutathione content. IBFF attenuated the D-Gal-induced increases in tumor necrosis factor-α (TNF-α), inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) mRNA and protein levels in the liver. Our data suggest that IBFF ameliorates D-Gal-induced acute liver injury and that this protection may be due to its antioxidative and anti-inflammatory activities.

Transgenic insulin-like growth factor-1 stimulates activation of COX-2 signaling in mammary glands

Studies show that elevated insulin-like growth factor-1 (IGF-1) levels are associated with an increased risk of breast cancer; however, mechanisms through which IGF-1 promotes mammary tumorigenesis in vivo have not been fully elucidated. To assess the possible involvement of COX-2 signaling in the pro-tumorigenic effects of IGF-1 in mammary glands, we used the unique BK5.IGF-1 mouse model in which transgenic (Tg) mice have significantly increased incidence of spontaneous and DMBA-induced mammary cancer compared to wild type (WT) littermates. Studies revealed that COX-2 expression was significantly increased in Tg mammary glands and tumors, compared to age-matched WTs. Consistent with this, PGE(2) levels were also increased in Tg mammary glands. Analysis of expression of the EP receptors that mediate the effects of PGE(2) showed that among the four G-protein-coupled receptors, EP3 expression was elevated in Tg glands. Up-regulation of the COX-2/PGE(2) /EP3 pathway was accompanied by increased expression of VEGF and a striking enhancement of angiogenesis in IGF-1 Tg mammary glands. Treatment with celecoxib, a selective COX-2 inhibitor, caused a 45% reduction in mammary PGE(2) levels, attenuated the influx of mast cells and reduced vascularization in Tg glands. These findings indicate that the COX-2/PGE(2) /EP3 signaling pathway is involved in IGF-1-stimulated mammary tumorigenesis and that COX-2-selective inhibitors may be useful in the prevention or treatment of breast cancer associated with elevated IGF-1 levels in humans. © 2011 Wiley Periodicals, Inc.

Ganoderma applanatum terpenes protect mouse liver against benzo(α)pyren-induced oxidative stress and inflammation

Ganoderma applanatum terpenes (GAT) have been reported to have many benefits and medicinal properties. In this study, we evaluated the protective effect of GAT against benzo(a)pyrene (BaP) induced oxidative stress and inflammation in mouse liver, and explored the potential mechanism of its action. Our data showed that GAT significantly decreased levels of ALT and AST in serum and the liver histological injury in BaP-treated mice. GAT markedly decreased the levels of ROS, MDA and lowered the GSH/GSSG ratio in the liver of BaP-treated mice. Furthermore, GAT markedly inhibited the BaP-induced increase of Cu/Zn-SOD, CAT, GPx and GST activities in the mouse liver. Western blot analysis showed that GAT significantly inhibited inflammation by pressing the expression of IL-1β and COX-2 and inhibiting NF-κB translocation in the liver of BaP-treated mice. In conclusion, these results suggested that GAT could protect the mouse liver against BaP-induced injury by improving hepatic function, attenuating histopathologic changes, decreasing levels of ROS and MDA, renewing the activities of antioxidant enzymes and suppressing inflammatory response.

The Role of Non-Steroidal Anti-Inflammatory Drugs in the Chemoprevention of Breast Cancer

Epidemiological evidence suggests that non-steroidal anti-inflammatory drugs (NSAIDs) which act as cyclooxygenase (COX-2) inhibitors may reduce breast cancer incidence by up to 20%. These agents are often taken for pain relief by older women with osteoarthritis. Age is the major risk factor for breast cancer in women with 50% cases being diagnosed in those aged >65 years. NSAIDs reduce serum estradiol by 17% in post-menopausal women and since most of these who develop breast cancers have estrogen receptor positive tumours; this suggests a possible preventative role. Careful use of these agents could provide a strategy for both relief of symptoms of osteoarthritis and also breast cancer prevention. Instead of conducting a randomised trial, proof of efficacy could be from an adequately powered cohort study within the breast screening programme.

Combination chemoprevention of HER2/neu-induced breast cancer using a cyclooxygenase-2 inhibitor and a retinoid X receptor-selective retinoid

The inducible prostaglandin synthase isoform cyclooxygenase-2 (COX-2) is overexpressed in approximately 40% of human breast carcinomas and in precancerous breast lesions, particularly in association with overexpression of human epidermal growth factor receptor 2 (HER2/neu). Experimental breast cancer can be suppressed by pharmacologic inhibition or genetic ablation of Cox-2, suggesting potential clinical utility of COX-2 inhibitors with respect to breast cancer. Importantly, several clinical trials have found reduced colorectal adenoma formation in individuals administered selective COX-2 inhibitors. However, such trials also identified increased cardiovascular risk associated with COX-2 inhibitor use. The goal of this research was to test whether improved chemopreventive efficacy could be achieved by combining submaximal doses of a selective COX-2 inhibitor and a retinoid X receptor-selective retinoid (rexinoid). The rate of HER2/neu-induced mammary tumor formation was substantially delayed by coadministration of the COX-2 inhibitor celecoxib (500 ppm in diet) and the rexinoid LGD1069 (10 mg/kg body weight; oral gavage) to MMTV/neu mice. Median time to tumor formation was increased from 304 to >600 days (P < 0.0001). The combination was substantially more effective than either drug individually. Similarly, potent suppression of aromatase activity was observed in mammary tissues from the combination cohort (44% of control; P < 0.001). Regulation of aromatase expression and activity by COX-derived prostaglandins is well established. Interestingly however, single agent LGD1069 significantly reduced mammary aromatase activity (71% of control; P < 0.001) without modulating eicosanoid levels. Our data show that simultaneous blockade of COX/prostaglandin signaling and retinoid X receptor-dependent transcription confers potent anticancer efficacy, suggesting a novel avenue for clinical evaluation.

Purple sweet potato color attenuates oxidative stress and inflammatory response induced by d-galactose in mouse liver

The hepatoprotective effects of purple sweet potato color (PSPC), which is natural anthocyanin food colors, have been well demonstrated in many studies. Nevertheless, little work has been done to clarify the detailed mechanism of hepatoprotective effects of PSPC. This study was designed to explore whether PSPC protected mouse liver from d-gal-induced injury by attenuating oxidative stress or suppressing inflammation. The histology changes of mouse liver was assessed by hematoxylin and eosin staining. The results showed that PSPC could effectively suppress the d-gal-induced histology changes including structure damage and leucocyte infiltration in mouse liver. Oxidative stress and antioxidant status in mouse liver were also analysed. The results showed that PSPC could largely attenuate the d-gal-induced MDA increasing and could markedly renew the activities of Cu, Zn-SOD, CAT and GPx in the livers of d-gal-treated mice. Furthermore, the results of western blot analysis showed that PSPC could inhibit the upregulation of the expression of NF-kappaB p65, COX-2 and iNOS caused by d-gal. In conclusion, our data suggested that PSPC could protect the mouse liver from d-gal-induced injury by attenuating lipid peroxidation, renewing the activities of antioxidant enzymes and suppressing inflammatory response. This study provided novel insights into the mechanisms of PSPC in the protection of the liver.

Progressive metaplastic and dysplastic changes in mouse pancreas induced by cyclooxygenase-2 overexpression

Cyclooxygenase-2 (COX-2) overexpression is an established factor linking chronic inflammation with metaplastic and neoplastic change in various tissues. We generated transgenic mice (BK5.COX-2) in which elevation of COX-2 and its effectors trigger a metaplasia-dysplasia sequence in exocrine pancreas. Histologic evaluation revealed a chronic pancreatitis-like state characterized by acinar-to-ductal metaplasia and a well-vascularized fibroinflammatory stroma that develops by 3 months. By 6 to 8 months, strongly dysplastic features suggestive of pancreatic ductal adenocarcinoma emerge in the metaplastic ducts. Increased proliferation, cellular atypia, and loss of normal cell/tissue organization are typical features in transgenic pancreata. Alterations in biomarkers associated with human inflammatory and neoplastic pancreatic disease were detected using immunohistochemistry. The abnormal pancreatic phenotype can be completely prevented by maintaining mice on a diet containing celecoxib, a well-characterized COX-2 inhibitor. Despite the high degree of atypia, only limited evidence of invasion to adjacent tissues was observed, with no evidence of distant metastases. However, cell lines derived from spontaneous lesions are aggressively tumorigenic when injected into syngeneic or nude mice. The progressive nature of the metaplastic/dysplastic changes observed in this model make it a valuable tool for examining the transition from chronic inflammation to neoplasia.

Paracrine overexpression of insulin-like growth factor-1 enhances mammary tumorigenesis in vivo

Insulin-like growth factor-1 (IGF-1) stimulates proliferation, regulates tissue development, protects against apoptosis, and promotes the malignant phenotype in the breast and other organs. Some epidemiological studies have linked high circulating levels of IGF-1 with an increased risk of breast cancer. To study the role of IGF-1 in mammary tumorigenesis in vivo, we used transgenic mice in which overexpression of IGF-1 is under the control of the bovine keratin 5 (BK5) promoter and is directed to either the myoepithelial or basal cells in a variety of organs, including the mammary gland. This model closely recapitulates the paracrine exposure of breast epithelium to stromal IGF-1 seen in women. Histologically, mammary glands from transgenic mice were hyperplastic and highly vascularized. Mammary glands from prepubertal transgenic mice had significantly increased ductal proliferation compared with wild-type tissues, although this difference was not maintained after puberty. Transgenic mice also had increased susceptibility to mammary carcinogenesis, and 74% of the BK5.IGF-1 mice treated with 7,12-dimethylbenz[a]anthracene (20 microg/day) developed mammary tumors compared with 29% of the wild-type mice. Interestingly, 31% of the vehicle-treated BK5.IGF-1 animals, but none of the wild-type animals, spontaneously developed mammary cancer. The mammary tumors were moderately differentiated adenocarcinomas that expressed functional, nuclear estrogen receptor at both the protein and mRNA levels. These data support the hypothesis that tissue overexpression of IGF-1 stimulates mammary tumorigenesis.

Inflammation and breast cancer. Cyclooxygenase/prostaglandin signaling and breast cancer

Many human cancers exhibit elevated prostaglandin (PG) levels due to upregulation of cyclooxygenase-2 (COX-2), a key enzyme in eicosanoid biosynthesis. COX-2 over-expression has been observed in about 40% of cases of invasive breast carcinoma and at a higher frequency in preinvasive ductal carcinoma in situ tumors, Extensive pharmacologic and genetic evidence implicates COX enzymes in neoplasia. Epidemiologic analyses demonstrate a protective effect of COX-inhibiting nonsteroidal anti-inflammatory drugs with respect to human cancer. Complementary experimental studies have established that both conventional nonsteroidal anti-inflammatory drugs and selective COX-2 inhibitors suppress mammary tumor formation in rodent breast cancer models. Furthermore, knocking out Cox-2 reduces mammary tumorigenesis and angiogenesis, and, conversely, transgenic COX-2 over-expression induces tumor formation. The utility of COX/PG signaling as a target for chemoprevention has been established by randomized controlled clinical trials. However, these studies also identified increased cardiovascular risk associated with use of selective COX-2 inhibitors. Thus, current efforts are directed toward identifying safer approaches to antagonizing COX/PG signaling for cancer prevention and treatment, with a particular focus on PGE₂ regulation and signaling, because PGE₂ is a key protumorigenic prostanoid.

The cyclooxygenase-2-mediated prostaglandin signaling is causally related to epithelial carcinogenesis

Epidemiologic, pharmacologic, clinical, and experimental studies document the importance of prostaglandin (PG) signaling in cancer development, including non-melanoma skin cancer lesions in humans and mice. First of all, enzymes involved in PG biosynthesis, such as cyclooxygenase (COX)-2 and/or membrane prostaglandin E synthase (mPGES)-1, were found to be overexpressed in a wide range of premalignant and malignant epithelial tumors, including those of the skin, breast, esophagus, stomach, colorectum, pancreas, and bladder. On the other hand, 15-hydroxy-prostaglandin dehydrogenase (15-PGDH), which is involved in the degradation pathway of PG including PGE(2,) thus counteracting the activities of COX-2 and PGES, was found to be downregulated in human epithelial tumors, indicating a tumor suppressor activity of this enzyme. Most remarkably, genetic studies showed that mice, which are deficient in COX-2 and/or PGES are resistant to the development of cancer of skin, colon, and stomach. In contrast, the forced overexpression of COX-2 in proliferative compartments of simple or stratified epithelia such as skin epidermis, urinary bladder, mammary gland, and pancreas results in spontaneous hyperplasia and dysplasia in transgenic mice. In skin, the pathological changes are found to be due to an abnormal process of terminal differentiation, while in other tissues, hyperproliferation seems to be the main contributor to the pre-invasive neoplasms. Moreover, the COX-2 transgenic mouse lines are sensitized for cancer development.

Inactivation of VEGF in mammary gland epithelium severely compromises mammary gland development and function

To investigate the role of the angiogenic cytokine vascular endothelial growth factor (VEGF) during pregnancy and lactation, we used mice in which VEGF had been inactivated in mammary gland epithelial cells. Pups born to mutant mothers failed to thrive, displaying little milk in their stomachs. However, when they were transferred to control mothers they developed normally. Investigation of the mammary gland morphology revealed that lobulo-alveolar expansion into the fat pad was not complete in lactating mutant glands, and an accumulation of fat globules was evident in their secretory epithelium. In contrast to control glands, lactating mutant glands failed to up-regulate mRNAs for genes involved in milk secretion. Blood vessel density was comparable in pregnant mice of both groups but was only half that of controls in lactating mutant mice. FITC-labeled albumin injected intravenously (i.v.) into lactating mice extravasated rapidly and accumulated in the mammary gland epithelial cells in control animals, but was almost completely retained within the vessels in the mutants. Injection of recombinant VEGF i.v. reversed this effect. These findings demonstrate that mammary epithelium-derived VEGF is partially dispensable for angiogenesis during pregnancy and lactation, and by regulating vascular function during lactation, this factor is crucial to mammary gland differentiation and milk production.

Tumor promotion as a target of cancer prevention

Tumor promotion is an essential process in multistage cancer development providing the conditions for clonal expansion and genetic instability of preneoplastic and premalignant cells. It is caused by a continuous disturbance of cellular signal transduction that results in an overstimulation of metabolic pathways along which mediators of cell proliferation and inflammation as well as genotoxic by-products are generated. Among such pathways the oxidative metabolism of arachidonic acid has turned out to be of utmost importance in tumor promotion. The aberrant overexpression of cyclooxygenase-2, an inducible enzyme of prostanoid synthesis and lipid peroxidation, is a characteristic feature of more than two-thirds of all human neoplasias, and the specific inhibition of this enzyme has been found to have a substantial chemopreventive effect in both animal models and man. The prostaglandins produced by COX-2 promote tumor development by stimulating cell proliferation and angiogenesis and by suppressing programmed cell death and immune defense. In mice, a COX-2 transgene fused with the keratin 5 promoter, which is constitutively active in the basal (proliferative) compartment of stratified and simple epithelia, causes a preneoplastic and premalignant phenotype in several organs. Among these organs, skin, mammary gland, urinary bladder, and pancreas have been investigated in more detail. Histologically and biochemically, the COX-2-dependent alterations resemble an autopromoted state that--as shown for skin and urinary bladder--strongly sensitizes the tissue for carcinogenesis. In transgenic animals COX-2 expression is not restricted to keratin 5-positive cells but is seen also in adjacent keratin 5-negative cells. This spreading of the COX-2 signal indicates a paracrine mechanism of autoamplification. While cancer chemoprevention by COX-2 inhibition is a rapidly developing field, much less is known about other pathways of unsaturated fatty acid metabolism, although some of them may play a role in carcinogenesis rivaling that of prostaglandin formation. Here an urgent demand for systematic research exists.

What are cyclooxygenases and lipoxygenases doing in the driver's seat of carcinogenesis?

Substantial evidence supports a functional role for cyclooxygenase- and lipoxygenase-catalyzed arachidonic and linoleic acid metabolism in cancer development. Genetic intervention studies firmly established cause-effect relations for cyclooxygenase-2, but cyclooxygenase-1 may also be involved. In addition, pharmacologic cyclooxygenase inhibition was found to suppress carcinogenesis in both experimental mouse models and several cancers in humans. Arachidonic acid-derived eicosanoid or linoleic acid-derived hydro[peroxy]fatty acid signaling are likely to be involved impacting fundamental biologic phenomena as diverse as cell growth, cell survival, angiogenesis, cell invasion, metastatic potential and immunomodulation. However, long chain unsaturated fatty acid oxidation reactions indicate antipodal functions of distinct lipoxygenase isoforms in carcinogenesis, i.e., the 5- and platelet-type 12-lipoxygenase exhibit procarcinogenic activities, while 15-lipoxygenase-1 and 15-lipoxygenase-2 may suppress carcinogenesis.

Preinvasive duct-derived neoplasms in pancreas of keratin 5-promoter cyclooxygenase-2 transgenic mice

BACKGROUND & AIMS

Basic research aimed at a better understanding of pancreatic carcinogenesis and improving the treatment of this disease is crucial because the majority of pancreatic cancers are highly aggressive and therapeutically nonaccessible. Cyclooxygenase (COX)-2, which is a key enzyme of prostaglandin (PG) biosynthesis, is overexpressed in around 75% of human carcinomas including those of the pancreas.

METHODS

The pathologic changes of transgenic mouse pancreas with keratin 5-promoter-driven expression and activity of COX-2 were characterized.

RESULTS

Aberrant expression of COX-2 in a few ductal cells and COX-2-mediated PG synthesis in the transgenic mice resulted in keratin 19- and mucin-positive intraductal papillary mucinous neoplasm- and pancreatic intraepithelial neoplasia-like structures, characterized by an increased proliferation index and serous cystadenomas. Moreover, Ras activation was enhanced and the HER-2/Neu receptor was overexpressed. Loss of acini, fibrosis, and inflammation were pronounced. Feeding a COX-2-selective inhibitor to the transgenic mice suppressed the accumulation of PG and the phenotype. The changes resemble the human disease in which COX-2 was overexpressed consistently.

CONCLUSIONS

We present strong evidence for a causal relationship between aberrant COX-2 overexpression and COX-2-mediated PG synthesis and the development of serous cystadenoma, intraductal papillary mucinous, and pancreatic intraepithelial neoplasms. This model offers the unique possibility of identifying molecular pathways leading to the formation and malignant progression of the various types of preinvasive lesions of pancreatic adenocarcinomas that show different dismal outcomes.

Differential protein expression in the epidermis of wild-type and COX-2 transgenic mice

Cyclooxygenases (COX) 1 and 2 are the key enzymes of prostaglandin biosynthesis. Like in many tissues, in adult skin COX-1 is a constitutive 'housekeeping' enzyme, while COX-2 is induced transiently in stress situations such as tissue damage and regeneration. In human skin carcinomas and corresponding early-stage cancer lesions, permanent COX-2 expression and activation is a consistent feature. Knockout and various transgenic approaches and pharmacologic studies show strong evidence for a cause-and-effect relationship between the aberrant COX-2 activation and tumor formation. In skin epidermis, keratin 5 promoter-driven overexpression of COX-2 caused hyperplasia and dysplasia, and sensitized skin for carcinogenesis. Therefore, this model offers the unique possibility of identifying COX-2-dependent and prostaglandin-mediated molecular pathways leading to the formation and malignant progression of early-stage cancer lesions.

Molecular pathology of breast apocrine carcinomas: A protein expression signature specific for benign apocrine metaplasia

Breast cancer is a heterogeneous disease that encompasses a wide range of histopathological types including: invasive ductal carcinoma, lobular carcinoma, medullary carcinoma, mucinous carcinoma, tubular carcinoma, and apocrine carcinoma among others. Pure apocrine carcinomas represent about 0.5% of all invasive breast cancers according to the Danish Breast Cancer Cooperative Group Registry, and despite the fact that they are morphologically distinct from other breast lesions, there are at present no standard molecular criteria available for their diagnosis. In addition, the relationship between benign apocrine changes and breast carcinoma is unclear and has been a matter of discussion for many years. Recent proteome expression profiling studies of breast apocrine macrocysts, normal breast tissue, and breast tumours have identified specific apocrine biomarkers [15-hydroxyprostaglandin dehydrogenase (15-PGDH) and hydroxymethylglutaryl coenzyme A reductase (HMG-CoA reductase)] present in early and advanced apocrine lesions. These biomarkers in combination with proteins found to be characteristically upregulated in pure apocrine carcinomas (psoriasin, S100A9, and p53) provide a protein expression signature distinctive for benign apocrine metaplasias and apocrine cystic lesions. These studies have also presented compelling evidence for a direct link, through the expression of the prostaglandin degrading enzyme 15-PGDH, between early apocrine lesions and pure apocrine carcinomas. Moreover, specific antibodies against the components of the expression signature have identified precursor lesions in the linear histological progression to apocrine carcinoma. Finally, the identification of proteins that characterize the early stages of mammary apocrine differentiation such as 15-PGDH, HMG-CoA reductase, and cyclooxygenase 2 (COX-2) has opened a window of opportunity for pharmacological intervention, not only in a therapeutic manner but also in a chemopreventive setting. Here we review published and recent results in the context of the current state of research on breast apocrine cancer.

Apocrine cysts of the breast: biomarkers, origin, enlargement, and relation with cancer phenotype

Up to one-third of women aged 30-50 years have cysts in their breasts and are presumed to be at increased risk of developing breast cancer. Here we present an extensive proteomic and immunohistochemistry (IHC) study of breast apocrine cystic lesions aimed at generating specific biomarkers and elucidating the relationship, if existent, of apocrine cysts with cancer phenotype. To this end we compared the expression profiles of apocrine macrocysts obtained from mastectomies from high risk cancer patients with those of cancerous and non-malignant mammary tissue biopsies collected from the same patients. We identified two biomarkers, 15-hydroxyprostaglandin dehydrogenase and 3-hydroxymethylglutaryl-CoA reductase, that were expressed specifically by apocrine type I cysts as well as by apocrine metaplastic cells in type II microcysts, terminal ducts, and intraductal papillary lesions. No expression of these markers was observed in non-malignant terminal ductal lobular units, type II flat cysts, stroma cells, or fat tissue as judged by IHC analysis of matched non-malignant tissue samples collected from 93 high risk patients enrolled in our cancer program. IHC analysis of the corresponding 93 primary tumors indicated that most apocrine changes have little intrinsic malignant potential, although some may progress to invasive apocrine cancer. None of the apocrine lesions examined, however, seemed to be a precursor of invasive ductal carcinomas, which accounted for 81% of the tumors analyzed. Our studies also provided some insight into the origin, development, and enlargement of apocrine cysts in mammary tissue. The successful identification of differentially expressed proteins that characterize specific steps in the progression from early benign lesions to apocrine cancer opens a window of opportunity for designing and testing new approaches for pharmacological intervention, not only in a therapeutic setting but also for chemoprevention, to inhibit cyst development as both 15-hydroxyprostaglandin dehydrogenase and 3-hydroxymethylglutaryl-CoA reductase are currently being targeted for chemoprevention strategies in various malignancies.

Current directions for COX-2 inhibition in breast cancer

Chemotherapy is effective against breast cancer. COX-2 has been implicated in the progression and angiogenesis of cancers. Celecoxib, a cyclooxygenase type 2 (COX-2) inhibitor, has both apoptotic and antiangiogenic activities, and may be of use in treatment of breast tumors which overexpress the COX-2 enzyme. Preliminary clinical trials have shown that the combination of chemotherapy with celecoxib has minimal additional toxicity and it may enhance the effects of the chemotherapy. Beside chemotherapy, celecoxib may promulgate the effect of aromatase inhibitor in breast cancer cells. Animal studies have shown that there are fewer and smaller tumors treated by combining exemestane and celecoxib. Larger clinical trials should be initiated to study the potential anti-cancer effects of celecoxib in breast cancer.

Myoepithelial cells in the control of mammary development and tumorigenesis: data from genetically modified mice

Until recently, myoepithelial cells-the second major cell population in the mammary epithelium-were not considered to play an important role in the morphogenetic events during gland development. Mouse mutants with changes in the gene expression pattern characteristic of the basal myoepithelial cell layer have been generated and used to show that these cells influence the proliferation, survival and differentiation of luminal cells, modulate stromal-epithelial interactions and actively participate in mammary morphogenesis. Various cellular and molecular mechanisms may underlie the observed phenotypes. These include an unbalanced expression of matrix degrading metalloproteinases (MMPs) and their inhibitors, leading to changes in the composition and organization of the (extracellular matrix) ECM, the production of soluble growth factors affecting stromal and epithelial cell growth and differentiation and direct signaling through cell-cell contacts between the myoepithelial and luminal cell layers.

Transitional Cell Hyperplasia and Carcinomas in Urinary Bladders of Transgenic Mice with Keratin 5 Promoter-Driven Cyclooxygenase-2 Overexpression

The inducible form of cyclooxygenase (COX), COX-2, is up-regulated in many epithelial cancers and its prostaglandin products increase proliferation, enhance angiogenesis, and inhibit apoptosis in several tissues. Pharmacologic inhibition and genetic deletion studies showed a marked reduction of tumor development in colon and skin. COX-2 has also been strongly implicated in urinary bladder cancer primarily by studies with nonselective COX- and COX-2-selective inhibitors. We now show that forced expression of COX-2, under the control of a keratin 5 promoter, is sufficient to cause transitional cell hyperplasia (TCH) in 17% and 75% of the heterozygous and homozygous transgenic lines, respectively, in an age-dependent manner. TCH was strongly associated with inflammation, primarily nodules of B lymphocytes; some T cells and macrophage infiltration were also observed. Additionally, transitional cell carcinoma was observed in approximately 10% of the K5.COX-2 transgenic mice; no TCH or transitional cell carcinoma was observed in wild-type bladders. Immunohistochemistry for vascular proliferation and vascular endothelial growth factor showed significant increases above that in wild-type urinary bladders. Our results suggest that overexpression of COX-2 is sufficient to cause hyperplasia and carcinomas in the urinary bladder. Therefore, inhibition of COX-2 should continue to be pursued as a potential chemopreventive and therapeutic strategy.