This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Brown, P. H. Articles by Howe, L. R. PubMed Articles by Brown, P. H. Articles by Howe, L. R. Related Collections Preclinical Intervention Preclinical Intervention: In Vivo (Animals): Drugs, Nutritional Interventions, Mechanisms

Combination Chemoprevention of HER2/neu-Induced Breast Cancer Using a Cyclooxygenase-2 Inhibitor and a Retinoid X Receptor–Selective Retinoid

Authors' Affiliations: ¹ Breast Center, Departments of Medicine and Molecular and Cellular Biology, Baylor College of Medicine, Houston, Texas; ² Departments of Medicine, ³ Cell and Developmental Biology, and ⁴ Public Health, Weill Medical College of Cornell University; ⁵ Strang Cancer Research Laboratory, Rockefeller University, New York, New York; ⁶ Pharmaceutical Development Center, M. D. Anderson Cancer Center, Houston, Texas; and ⁷ Department of Molecular Oncology, Ligand Pharmaceuticals, Inc., San Diego, California

Requests for reprints: Louise R. Howe, Department of Cell and Developmental Biology, Weill Cornell Medical College, Box 60, 1300 York Avenue, New York, NY 10065. Phone: 212-792-5174; Fax: 212-249-0013; E-mail: lrhowe@med.cornell.edu.

	Abstract

TOP Abstract Materials and Methods Results and Discussion Disclosure of Potential... Acknowledgments References

 
The inducible prostaglandin synthase isoform cyclooxygenase-2 (COX-2) is overexpressed in 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.

Key Words: COX-2 • HER2/neu • RXR-selective retinoid

TOP Abstract Materials and Methods Results and Discussion Disclosure of Potential... Acknowledgments References

 
The inducible prostaglandin (PG) synthase cyclooxygenase-2 (COX-2) is strongly implicated in breast neoplasia (1, 2). COX-2 is overexpressed in 40% of human breast carcinomas and in 60% to 80% of preinvasive ductal carcinoma in situ lesions (1, 2). COX-2 overexpression in breast carcinomas correlates with poor prognosis and with several associated clinical variables, including overexpression of human epidermal growth factor receptor 2 (HER2; also called neu and c-ERBB2; refs. 3–8). Epidemiologic data are broadly consistent with a protumorigenic role for COX enzymes. Several studies have identified reduced breast cancer incidence associated with the use of COX-inhibiting drugs including aspirin, nonsteroidal antiinflammatory drugs, and selective COX-2 inhibitors (9–17).

Consistent with the human expression data, Cox-2 is also up-regulated in rodent mammary tumors (18–22), and thus rodent breast cancer models have proved useful for analyzing the contribution of Cox-2 to mammary neoplasia. Numerous studies have shown that experimental breast cancer can be suppressed by inhibiting Cox activity using either conventional nonsteroidal antiinflammatory drugs or selective Cox-2 inhibitors (1, 2). Given the observed correlations between COX-2 and HER2/neu overexpression in human breast tumors (3–6), HER2/neu-driven models are of particular interest. Both we and others have shown that HER2/neu-induced tumor formation is significantly delayed by administration of the selective COX-2 inhibitor celecoxib (20, 23). Furthermore, knocking out Cox-2 significantly decreases HER2/neu-induced mammary tumor formation in mice (24). Conversely, transgenic overexpression of COX-2 is sufficient to induce mammary neoplasia in multiparous mice, providing direct evidence of the in vivo oncogenicity of COX-2 (25). Mechanistically, the antitumor action of Cox-2 inhibition has been ascribed to induction of apoptosis, suppression of proliferation, and modulation of tumor cell invasiveness and immunosurveillance (2). Additionally, genetic manipulations of Cox-2 gene dosage suggest an important role for Cox-2 in regulating both angiogenesis and the activity of the estrogen synthase aromatase in breast tissues (24, 26–28).

Together, the above data sets identify COX-2 as a potential target for inhibiting breast carcinogenesis, stimulating the development of several clinical trials designed to evaluate COX-2 inhibitors in breast cancer patients.⁸ In support of this approach, randomized clinical trials have shown that COX-2 inhibitors can reduce the incidence of colorectal adenomas (29, 30). Less propitiously, some studies reported an increased risk of cardiovascular events associated with COX-2 inhibitor use, reducing enthusiasm for COX-2 inhibitors as cancer chemopreventive agents (29, 30). Nevertheless, the demonstrated role of COX/PG signaling in neoplasia identifies this pathway as an important target. Thus, it behooves us to identify anticancer strategies capable of suppressing this signaling axis with minimal associated toxicity. We hypothesized that enhanced anti–breast cancer activity and diminished side effects could be achieved by using a COX-2 inhibitor in combination with a drug from a distinct class. Such combination approaches offer the potential to achieve substantial cancer suppression while minimizing collateral toxicity by combining submaximal doses of two or more agents (31–33). To test this concept, here we have assessed the chemopreventive efficacy with respect to HER2/neu-induced breast cancer of celecoxib in combination with the retinoid LGD1069.

Retinoids have extensively been evaluated as cancer chemopreventive agents (34, 35). Early clinical trials established the utility of retinoids for preventing cancer, using vitamin A derivatives such as 13-cis-retinoid acid, all-trans retinoic acid, and 9-cis-retinoic acid. However, these trials also identified unacceptable toxicity associated with high-dose regimens of these naturally occurring retinoids. Limiting toxicities include teratogenicity, hepatotoxicity, severe headaches, and mucocutaneous toxicity. More recently, compounds with greater selectivity, and hence decreased toxicity, have been developed through increased understanding of retinoid receptor biology (31, 36). Two distinct classes of retinoid receptors have been identified: retinoic acid receptors and retinoid X receptors (RXR). Whereas both retinoic acid receptors and RXRs are ligand-regulated transcription factors of the steroid/thyroid hormone receptor superfamily, the two classes are distinguished by their differential ligand affinities and by the spectrum of proteins with which they interact. Importantly, RXR-selective retinoids, or rexinoids, have markedly diminished toxicities relative to pan-retinoids and retinoic acid receptor ligands (37), and thus offer considerable promise as anticancer agents. Of particular interest, both LGD1069 (bexarotene, Targretin) and LG100268 have robust chemopreventive efficacy with respect to experimental breast cancer, including HER2/neu-induced tumorigenesis (31, 36, 38–40).

Here we have evaluated the combination of the selective COX-2 inhibitor celecoxib and the RXR-selective retinoid LGD1069 for preventing HER2/neu-induced mammary tumorigenesis. We show that celecoxib and LGD1069 in combination mediate greater-than-additive suppression of mammary tumor formation in HER2/neu transgenic mice. Furthermore, parallel decreases in mammary aromatase activity were observed, suggesting that aromatase modulation may contribute to tumor suppression mediated by the celecoxib/LGD1069 combination.

	Materials and Methods

TOP Abstract Materials and Methods Results and Discussion Disclosure of Potential... Acknowledgments References

 
Reagents and chemicals
Celecoxib {Celebrex; 4-[5-(4-methylphenyl)-3-(trifluoromethyl)-1H-pyrazol-1-yl]benzene-sulfonamide} was purchased from LKT Laboratories, Inc. LGD1069 (Targretin; bexarotene) was provided by Ligand Pharmaceuticals.

Mouse experimental procedures
FVB/N-Tg(MMTVneu)202Mul/J mice (MMTV/neu) were obtained from The Jackson Laboratory and bred to produce multiple litters. Virgin female offspring were used in three separate studies.

Study I
Study I has previously been reported (20), and tumor latency data from that study are provided in Table 4 for comparative purposes only. To briefly recapitulate the study design, females were randomly assigned to one of two groups at 3 wk of age (vehicle or celecoxib), both of which were fed Laboratory Autoclavable Rodent Diet 5010 ad libitum. The diet of mice in the celecoxib group was supplemented with 500 ppm celecoxib.

In all three studies, mice were palpated twice weekly for mammary gland tumors, and the age at appearance of the first tumor was recorded (tumor latency). In studies II and III, animals were sacrificed 2 mo after initial tumor detection, and the number of tumors of at least 0.5-cm diameter was scored (tumor multiplicity). Non–tumor-bearing animals were maintained for their natural life span, or up to 98 wk, whichever was shorter. All animals were euthanized by CO₂ asphyxiation in accordance with the recommendations of the Panel on Euthanasia of the American Veterinary Medical Association. Mammary tissues were harvested from sacrificed animals, snap-frozen in liquid nitrogen, and stored at –80°C. Additionally, a portion of mammary tissues and tumors were formalin fixed and embedded in paraffin. Tumors were confirmed by histologic evaluation. Nontumorous mammary glands were used for subsequent analyses.

Determination of eicosanoid levels
Resected mammary glands were homogenized, and eicosanoids were extracted and assayed by liquid chromatography-tandem mass spectrometry as previously described (41).

Assay of celecoxib levels
Blood was collected from 5.5-mo-old animals by retroorbital bleeding, and plasma levels of celecoxib were assayed by liquid chromatography-mass spectrometry as previously described (20).

Aromatase activity assays
Resected mammary glands were homogenized, and mammary aromatase activity was assayed by measuring the release of ³H₂O from [1-³H]androstenedione as previously described (28).

Statistical analysis
Kaplan-Meier curves of tumor-free survival in control and drug-treated cohorts were compared with a log-rank test (two-tailed; Prism 4.0 for Macintosh, GraphPad Software, Inc.). Poisson regression analysis was used to compare tumor multiplicity in each group based on the assumption that the number of tumors per animal would follow a Poisson distribution. Mean tumor multiplicity was compared in a pairwise manner, and P values were corrected for multiple comparisons using Tukey's method. Repeated measure ANOVA was used to compare the mean mouse weights in each experimental group over time. Mammary eicosanoid data, shown as mean ± SD, were compared by one-way ANOVA and further analyzed by Dunnett's test to effect comparisons between each treatment group and the control group, adjusting for multiple comparisons. Aromatase activity data, shown as mean + SD, were evaluated for statistical significance with one-way ANOVA followed by pairwise testing using Tukey's method to adjust for multiple comparisons.

	Results and Discussion

TOP Abstract Materials and Methods Results and Discussion Disclosure of Potential... Acknowledgments References

 
Celecoxib and LGD1069 mediate greater-than-additive suppression of mammary tumorigenesis
The primary goal of this research was to compare the chemopreventive efficacy of the COX-2 inhibitor celecoxib and the RXR-selective retinoid LGD1069, alone and in combination, in a breast cancer model. Our ultimate aim was to determine whether greater protection could be achieved by combining drugs from two distinct classes than could be achieved using either drug individually. This combination chemoprevention approach offers the possibility of increased preventive efficacy with minimal associated toxicity through utilization of submaximal doses of individual agents. Thus, drug doses for our study were selected based on the following information. Celecoxib delays tumor formation in MMTV/neu mice when administered in food at either 500 or 900 ppm, whereas 1,500 ppm celecoxib induces cachexia and weight loss in this mouse strain (20, 23). LGD1069 has dose-dependent activity in the MMTV/neu model over the range 10 to 100 mg/kg body weight (40). Therefore, we selected 500 ppm celecoxib and 10 mg/kg LGD1069 as submaximal doses for use in our study.

Virgin female MMTV/neu mice were randomly assigned to one of four experimental groups at 8 weeks of age, as shown in Table 1. Tumor incidence was measured as a function of time in all four groups. The rate of formation of mammary tumors was significantly delayed in the LGD1069 cohort relative to the vehicle group (Fig. 1; Table 2), consistent with the previously reported chemopreventive action of LGD1069 with respect to HER2/neu-induced breast cancer (40). Mammary tumors were detected in 50% of control animals by 304 days of age, versus 420 days of age in LGD1069-treated mice (T₅₀ = 304 versus 420 days; P = 0.0085). Unexpectedly, celecoxib alone failed to delay tumor onset in this study (Fig. 1; Table 2), in contrast to previous reports (20, 23). Failure to achieve comparable circulating celecoxib levels in this study relative to our earlier study would provide a trivial explanation for the lack of effect of celecoxib in the present study. However, serum celecoxib levels in this experiment were 2.8 ± 0.7 µmol/L (mean ± SD; range, 2.2-3.6 µmol/L), and thus extremely similar to those achieved in our previous study (mean, 2.4 µmol/L; ref. 20). We hypothesize that the variable protective efficacy of celecoxib between studies may be attributable to the use of different diets in each experiment (discussed below).

View larger version (12K): [in this window] [in a new window]   Fig. 1. Suppression of mammary tumorigenesis by celecoxib and LGD1069. Female MMTV/neu transgenic mice were subjected to the following drug regimens, starting at 8 wk of age. Group 1 were fed control diet and gavaged 5 d/wk with 100-µL sesame oil (Vehicle; black squares). Group 2 were fed diet containing 500 ppm celecoxib and gavaged 5 d/wk with 100-µL sesame oil (Celecoxib; yellow diamonds). Group 3 received control diet and were gavaged 5 d/wk with 10 mg/kg body weight LGD1069 in 100-µL sesame oil (LGD1069; red triangles). Group 4 were fed celecoxib-containing diet and gavaged with LGD1069 (Both; blue circles). Statistical comparisons of tumor latency were done using the log-rank test, and data are shown in Table 2. The median time to tumor formation was significantly delayed by LGD1069 administration. Celecoxib alone was ineffective but significantly increased the delay in tumor formation mediated by LGD1069.

Drug-mediated perturbations of mammary eicosanoid levels
We previously reported a reduction of 50% in mammary PGE₂ levels in celecoxib-treated mice (20). In the present study, celecoxib administration resulted in a modest 34% decrease in mean mammary PGE₂ levels and a 49% decrease in mean mammary PGD₂ levels (Table 3), although neither of these changes achieved statistical significance. Interestingly, substantially increased levels of leukotriene B₄ and 12-hydroxyeicosatetraenoic acid were observed in mammary tissues from celecoxib-treated animals (Table 3). Mean levels of mammary leukotriene B₄ and 12-hydroxyeicosatetraenoic acid were increased to 337% and 183%, respectively, of those in mammary tissues from vehicle-treated mice (P < 0.001 and P = 0.11, respectively). These data suggest that a metabolic shunt is occurring in mammary tissues from celecoxib-treated animals, with arachidonic acid being metabolized by 5-lipoxygenase to leukotriene A₄ and subsequent byproducts, and by 12-lipoxygenase to 12-hydroxyeicosatetraenoic acid, (rather than by Cox-2).

Mouse diet modulates susceptibility to celecoxib-mediated tumor suppression
The failure of celecoxib to delay tumor formation in MMTV/neu mice in the present study contrasts with previous data from our group and from other investigators (20, 23). Three alterations in experimental design relative to our earlier study were implemented in the present study, any of which could provide a basis for the discrepant observations. First, the age at initiation of drug administration was changed from 3 weeks in our first study (study I) to 8 weeks in the present study (study II). Second, the diet was switched from 5010 mouse chow to AIN-76A, a purified diet. Third, all animals received 100 µL of sesame oil by gavage 5 d/wk. To evaluate the influence of timing of drug initiation on celecoxib efficacy, a third study was done (study III) in which animals were fed AIN-76A, as in study II, and celecoxib administration was initiated at 3 weeks, as in study I. Tumor latency in the vehicle cohort was similar to that observed in study II, and the rate of tumor formation was not delayed by celecoxib administration (Table 4). Comparison of tumor latencies in control cohorts in all three experiments suggests that the alteration in diet could account for the lack of concordance between these studies. Specifically, tumors formed substantially more rapidly in the vehicle cohort in study I than in study II or III (e.g., T₅₀ = 32 weeks in study I versus T₅₀ = 43 weeks in study II; Table 4), suggesting that tumor formation is accelerated in MMTV/neu mice fed 5010 mouse chow compared with those fed AIN-76A diet, presumably due to differences in nutritional constituents. Because tumor latency was similar in the vehicle cohort in studies II and III, but only animals in study II received sesame oil, we infer that sesame oil administration in study II is unlikely to account for the increased tumor latency observed in studies II and III relative to study I.

Comparisons of tumor latencies in vehicle-treated animals in the three studies and of the relative chemopreventive efficacy of celecoxib thus support the following conclusions. First, the rate of mammary tumor formation is accelerated in MMTV/neu mice fed 5010 mouse chow relative to those consuming AIN-76A purified diet (study I versus studies II and III). Second, consumption of 5010 mouse chow is associated with susceptibility to celecoxib-mediated chemoprotection against breast cancer (study I versus studies II and III). Third, initiating drug treatment at 3 weeks of age in AIN-76A–fed mice is insufficient to confer susceptibility to celecoxib-mediated protection (study II versus study III).

Because HER2/neu-induced breast neoplasia is suppressed by either pharmacologic inhibition or genetic ablation of the PG synthase Cox-2 (20, 23, 24), increasing mammary PG levels would be predicted to accelerate HER2/neu-driven mammary tumor formation. We speculate that 5010 chow may contain components that increase mammary eicosanoid levels. Consistent with this notion, dietary administration of celecoxib reduced mammary PGE₂ by only 34% in animals consuming AIN-76A (Table 3), compared with the 47% reduction we previously reported for 5010-fed animals (20), suggesting that animals consuming 5010 chow may have elevated basal mammary eicosanoid levels.

Celecoxib and LGD1069 suppress mammary aromatase activity
Our next goal was to investigate potential mechanisms by which celecoxib and LGD1069 might induce greater-than-additive suppression of HER2/neu-induced mammary tumor formation. Substantial evidence supports a functional relationship between COX/PG signaling and the estrogen synthase aromatase. Correlations have been identified between expression of COX enzymes and the aromatase cytochrome P450 in human breast cancers (45, 46). These correlations are believed to reflect a causal relationship because PG signaling can stimulate transcription of the CYP19 gene encoding aromatase (28, 47–51). Furthermore, aromatase activity is reduced in mammary tissues from Cox-2 knockout mice and, conversely, is increased by transgenic COX-2 overexpression (27, 28). Therefore, we focused on aromatase modulation as a potential effector of celecoxib/LGD1069–mediated chemoprotection.

Aromatase activity was compared in mammary tissues from all four experimental groups of the celecoxib/LGD1069 combination chemoprevention experiment (study II). Celecoxib alone caused a 17% decrease in mammary aromatase activity relative to that in the vehicle cohort (P < 0.001; Fig. 2). The magnitude of the celecoxib effect was substantially less than the 60% reduction in mammary aromatase activity we had previously observed in Cox-2 knockout mice (28), consistent with the comparatively modest celecoxib-mediated reductions in mammary PGE₂ levels in the current experiment (Table 3).

View larger version (6K): [in this window] [in a new window]   Fig. 2. Celecoxib and LGD1069 suppress mammary aromatase activity. Aromatase activity was measured in mammary glands harvested from mice from each of the four experimental groups in the experiment shown in Fig. 1 (study II). Aromatase activity in all three drug-treated groups was significantly lower than that in the control group (*, P < 0.001). Celecoxib caused a modest reduction in mammary aromatase activity (83% of control). Aromatase activity was decreased to 71% in tissues from mice treated with LGD1069 alone, and to 44% in tissues from mice treated with both celecoxib and LGD1069. Aromatase activity in tissues from the celecoxib/LGD1069 combination group was significantly less than that in samples from animals treated with LGD1069 alone (, P < 0.001). Enzyme activity is expressed as fentomoles per microgram of protein per hour. Columns, mean (n = 6 per group); bars, SD.

Strikingly, the combination of celecoxib and LGD1069 potently suppressed mammary aromatase activity, causing a greater-than-additive reduction (56%; P < 0.001, compared with vehicle; Fig. 2). The relative potency of the three drug regimens for depressing mammary aromatase activity was celecoxib/LGD1069 > LGD1069 > celecoxib. Because the drug regimens ranked in the same order of efficacy with respect to tumor suppression, we speculate that inhibition of aromatase expression may contribute to the observed chemopreventive activity. Whereas frank tumors in MMTV/neu mice lack estrogen receptor expression, estrogen receptor is expressed in normal-appearing and hyperplastic MMTV/neu mammary tissues (40, 53). Importantly, tumor formation in the MMTV/neu strain is antagonized by the selective estrogen receptor modulators arzoxifene and acolbifene, indicating that estrogen signaling contributes to tumorigenesis in this model (39). Thus, we conclude that drug-mediated alterations in mammary aromatase activity may contribute to the observed chemopreventive activity of the celecoxib/LGD1069 combination.

Conclusions
The major goal of this study was to compare the chemopreventive efficacy of celecoxib and LGD1069 in combination with that of each of the two drugs individually in a breast cancer model. The MMTV/neu strain was used for this experiment because we had previously demonstrated chemopreventive efficacy of both celecoxib and LGD1069 as single agents in this model (20, 40). We observed a potent, greater-than-additive action of celecoxib and LGD1069 in suppressing mammary tumor formation (Fig. 1). Interestingly, we detected corresponding decreases in mammary aromatase activity (Fig. 2), leading us to conclude that aromatase suppression may be a component of the anticancer action of the celecoxib/LGD1069 combination.

Our data have potential implications for the clinical management of breast cancer. Combination approaches are thought likely to afford greater benefit than can be achieved using single agents, with the additional benefit of minimizing collateral toxicity (31–33). For example, simultaneous targeting of COX-2 and HER-2/neu with celecoxib and anti–HER-2 antibodies has been shown to inhibit experimental colorectal carcinoma growth more effectively than either agent alone (54). This combination approach has been extended to experimental breast cancer. Rexinoid/selective estrogen receptor modulator combinations, for example, have striking synergistic efficacy in rodent breast cancer models (31, 39). Furthermore, clinical trials are ongoing to evaluate celecoxib in combination with aromatase inhibitors as neoadjuvant therapy. LGD1069 is Food and Drug Administration approved for treating refractory advanced stage cutaneous T-cell lymphoma, and is currently being evaluated in numerous clinical studies, including breast cancer–related trials. Additionally, several rexinoids with even greater RXR selectivity, and hence diminished side effects, have been developed, including LG100268 and UAB30 (31, 36, 55). These agents have demonstrated cancer-preventive activity and may be useful candidates for future clinical development. The results of our present study suggest that drug combinations targeting COX/PG signaling and RXR-dependent transcription may have clinical utility for breast cancer prevention.

	Disclosure of Potential Conflicts of Interest

TOP Abstract Materials and Methods Results and Discussion Disclosure of Potential... Acknowledgments References

 
R.P. Bissonnette and P.H. Brown: Ownership Interest, Ligand Pharmaceuticals. A.J. Dannenberg: Commercial Research Grant, Pfizer, Inc.; Consultant, Tragara Pharmaceuticals and Pfizer, Inc. The other authors disclosed no potential conflicts of interest.

	Acknowledgments

TOP Abstract Materials and Methods Results and Discussion Disclosure of Potential... Acknowledgments References

 
We thank Paul Christos for providing preliminary statistical support for this study.

	Footnotes

 
Grant support: NIH grants R03 CA105458 (L.R. Howe), R03 CA119273 (L.R. Howe), and R01 CA078480 (P.H. Brown); a Breast Cancer Alliance Young Investigator Grant (L.R. Howe); the Breast Cancer Research Foundation (P.H. Brown and A.J. Dannenberg); and the Irving Weinstein Foundation, Inc. (L.R. Howe).

http://www.cancer.gov/clinicaltrials

Received for publication February 20, 2008. Accepted February 27, 2008

	References

TOP Abstract Materials and Methods Results and Discussion Disclosure of Potential... Acknowledgments References

 

1. Howe LR. Inflammation and breast cancer. Cyclooxygenase/prostaglandin signaling and breast cancer. Breast Cancer Res 2007;6:210.

2. Howe LR. Cyclooxygenase-2 and breast cancer. In: Yao AP, editor. Trends in breast cancer research. New York: Nova; 2005, p. p. 1–38.

3. Boland GP, Butt IS, Prasad R, Knox WF, Bundred NJ. COX-2 expression is associated with an aggressive phenotype in ductal carcinoma in situ. Br J Cancer 2004;90:423–9.[CrossRef][Medline]

4. Ristimaki A, Sivula A, Lundin J et al . Prognostic significance of elevated cyclooxygenase-2 expression in breast cancer. Cancer Res 2002;62:632–5.[Abstract/Free Full Text]

5. Subbaramaiah K, Norton L, Gerald W, Dannenberg AJ. Cyclooxygenase-2 is overexpressed in HER-2/neu-positive breast cancer. Evidence for involvement of AP-1 and PEA3. J Biol Chem 2002;277:18649–57.[Abstract/Free Full Text]

6. Wulfing P, Diallo R, Muller C et al . Analysis of cyclooxygenase-2 expression in human breast cancer: high throughput tissue microarray analysis. J Cancer Res Clin Oncol 2003;129:375–82.[CrossRef][Medline]

7. Denkert C, Winzer KJ, Muller BM et al . Elevated expression of cyclooxygenase-2 is a negative prognostic factor for disease free survival and overall survival in patients with breast carcinoma. Cancer 2003;97:2978–87.[CrossRef][Medline]

8. Spizzo G, Gastl G, Wolf D et al . Correlation of COX-2 and Ep-CAM overexpression in human invasive breast cancer and its impact on survival. Br J Cancer 2003;88:574–8.[CrossRef][Medline]

9. Friedman GD Ury HK. Initial screening for carcinogenicity of commonly used drugs. J Natl Cancer Inst 1980;65:723–33.[Medline]

10. Harris RE, Beebe-Donk J, Alshafie GA. Reduction in the risk of human breast cancer by selective cyclooxygenase-2 (COX-2) inhibitors. BMC Cancer 2006;6:27.[CrossRef][Medline]

11. Harris RE, Chlebowski RT, Jackson RD et al . Breast cancer and nonsteroidal anti-inflammatory drugs: prospective results from the Women's Health Initiative. Cancer Res 2003;63:6096–101.[Abstract/Free Full Text]

12. Harris RE, Namboodiri KK, Farrar WB. Nonsteroidal antiinflammatory drugs and breast cancer. Epidemiology 1996;7:203–5.[Medline]

13. Khuder SA Mutgi AB. Breast cancer and NSAID use: a meta-analysis. Br J Cancer 2001;84:1188–92.[CrossRef][Medline]

14. Rahme E, Ghosn J, Dasgupta K, Rajan R, Hudson M. Association between frequent use of nonsteroidal anti-inflammatory drugs and breast cancer. BMC Cancer 2005;5:159.[CrossRef][Medline]

15. Schreinemachers DM Everson RB. Aspirin use and lung, colon, and breast cancer incidence in a prospective study. Epidemiology 1994;5:138–46.[Medline]

16. Sharpe CR, Collet JP, McNutt M, Belzile E, Boivin JF, Hanley JA. Nested case-control study of the effects of non-steroidal anti-inflammatory drugs on breast cancer risk and stage. Br J Cancer 2000;83:112–20.[CrossRef][Medline]

17. Terry MB, Gammon MD, Zhang FF et al . Association of frequency and duration of aspirin use and hormone receptor status with breast cancer risk. JAMA 2004;291:2433–40.[Abstract/Free Full Text]

18. Hamid R, Singh J, Reddy BS, Cohen LA. Inhibition by dietary menhaden oil of cyclooxygenase-1 and -2 in N-nitrosomethylurea-induced rat mammary tumors. Int J Oncol 1999;14:523–8.[Medline]

19. Howe LR, Crawford HC, Subbaramaiah K, Hassell JA, Dannenberg AJ, Brown AMC. PEA3 is up-regulated in response to Wnt1 and activates the expression of cyclooxygenase-2. J Biol Chem 2001;276:20108–15.[Abstract/Free Full Text]

20. Howe LR, Subbaramaiah K, Patel J et al . Celecoxib, a selective cyclooxygenase-2 inhibitor, protects against human epidermal growth factor receptor 2 (HER-2)/neu-induced breast cancer. Cancer Res 2002;62:5405–7.[Abstract/Free Full Text]

21. Nakatsugi S, Ohta T, Kawamori T et al . Chemoprevention by nimesulide, a selective cyclooxygenase-2 inhibitor, of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP)-induced mammary gland carcinogenesis in rats. Jpn J Cancer Res 2000;91:886–92.[CrossRef]

22. Robertson FM, Parrett ML, Joarder FS et al . Ibuprofen-induced inhibition of cyclooxygenase isoform gene expression and regression of rat mammary carcinomas. Cancer Lett 1998;122:165–75.[CrossRef][Medline]

23. Lanza-Jacoby S, Miller S, Flynn J et al . The cyclooxygenase-2 inhibitor, celecoxib, prevents the development of mammary tumors in Her-2/neu mice. Cancer Epidemiol Biomarkers Prev 2003;12:1486–91.[Abstract/Free Full Text]

24. Howe LR, Chang SH, Tolle KC et al . HER2/neu-induced mammary tumorigenesis and angiogenesis are reduced in cyclooxygenase-2 knockout mice. Cancer Res 2005;65:10113–9.[Abstract/Free Full Text]

25. Liu CH, Chang SH, Narko K et al . Overexpression of cyclooxygenase-2 is sufficient to induce tumorigenesis in transgenic mice. J Biol Chem 2001;276:18563–9.[Abstract/Free Full Text]

26. Chang SH, Liu CH, Conway R et al . Role of prostaglandin E2-dependent angiogenic switch in cyclooxygenase 2-induced breast cancer progression. Proc Natl Acad Sci U S A 2004;101:591–6.[Abstract/Free Full Text]

27. Muller-Decker K, Berger I, Ackermann K et al . Cystic duct dilatations and proliferative epithelial lesions in mouse mammary glands upon keratin 5 promoter-driven overexpression of cyclooxygenase-2. Am J Pathol 2005;166:575–84.[Abstract/Free Full Text]

28. Subbaramaiah K, Howe LR, Port ER et al . HER-2/neu status is a determinant of mammary aromatase activity in vivo: evidence for a cyclooxygenase-2-dependent mechanism. Cancer Res 2006;66:5504–11.[Abstract/Free Full Text]

29. Bertagnolli MM. Chemoprevention of colorectal cancer with cyclooxygenase-2 inhibitors: two steps forward, one step back. Lancet Oncol 2007;8:439–43.[CrossRef][Medline]

30. Bresalier RS. Chemoprevention of colorectal neoplasia: advances and controversies (the COX-2 story). Curr Opin Gastroenterol 2007;23:44–7.[Medline]

31. Liby KT, Yore MM, Sporn MB. Triterpenoids and rexinoids as multifunctional agents for the prevention and treatment of cancer. Nat Rev Cancer 2007;7:357–69.[CrossRef][Medline]

32. Steele VE Kelloff GJ. Development of cancer chemopreventive drugs based on mechanistic approaches. Mutat Res 2005;591:16–23.[Medline]

33. Dannenberg AJ, Lippman SM, Mann JR, Subbaramaiah K, DuBois RN. Cyclooxygenase-2 and epidermal growth factor receptor: pharmacologic targets for chemoprevention. J Clin Oncol 2005;23:254–66.[Abstract/Free Full Text]

34. Lippman SM Lotan R. Advances in the development of retinoids as chemopreventive agents. J Nutr 2000;130:479S–82S.

35. Moon RC, Mehta RG, Rao KVN. Retinoids and cancer in experimental animals. In: MB Sporn, AB Roberts, and DS Goodman, editors. The retinoids: biology, chemistry and medicine. 2nd ed. New York: Raven Press;; 1994, p. 573–95.

36. Howe LR. Rexinoids and breast cancer prevention. Clin Cancer Res 2007;13:5983–7.[Free Full Text]

37. Miller VA, Benedetti FM, Rigas JR et al . Initial clinical trial of a selective retinoid X receptor ligand, LGD1069. J Clin Oncol 1997;15:790–5.[Abstract/Free Full Text]

38. Gottardis MM, Bischoff ED, Shirley MA, Wagoner MA, Lamph WW, Heyman RA. Chemoprevention of mammary carcinoma by LGD1069 (Targretin): an RXR-selective ligand. Cancer Res 1996;56:5566–70.[Abstract/Free Full Text]

39. Liby K, Rendi M, Suh N et al . The combination of the rexinoid, LG100268, and a selective estrogen receptor modulator, either arzoxifene or acolbifene, synergizes in the prevention and treatment of mammary tumors in an estrogen receptor-negative model of breast cancer. Clin Cancer Res 2006;12:5902–9.[Abstract/Free Full Text]

40. Wu K, Zhang Y, Xu XC et al . The retinoid X receptor-selective retinoid, LGD1069, prevents the development of estrogen receptor-negative mammary tumors in transgenic mice. Cancer Res 2002;62:6376–80.[Abstract/Free Full Text]

41. Yang P, Chan D, Felix E et al . Determination of endogenous tissue inflammation profiles by LC/MS/MS: COX- and LOX-derived bioactive lipids. Prostaglandins Leukot Essent Fatty Acids 2006;75:385–95.[CrossRef][Medline]

42. Wu K, Kim HT, Rodriquez JL et al . Suppression of mammary tumorigenesis in transgenic mice by the RXR-selective retinoid, LGD1069. Cancer Epidemiol Biomarkers Prev 2002;11:467–74.[Abstract/Free Full Text]

43. Kim HT, Kong G, Denardo D et al . Identification of biomarkers modulated by the rexinoid LGD1069 (bexarotene) in human breast cells using oligonucleotide arrays. Cancer Res 2006;66:12009–18.[Abstract/Free Full Text]

44. Kong G, Kim HT, Wu K et al . The retinoid X receptor-selective retinoid, LGD1069, down-regulates cyclooxygenase-2 expression in human breast cells through transcription factor crosstalk: implications for molecular-based chemoprevention. Cancer Res 2005;65:3462–9.[Abstract/Free Full Text]

45. Brodie AM, Lu Q, Long BJ et al . Aromatase and COX-2 expression in human breast cancers. J Steroid Biochem Mol Biol 2001;79:41–7.[CrossRef][Medline]

46. Brueggemeier RW, Quinn AL, Parrett ML, Joarder FS, Harris RE, Robertson FM. Correlation of aromatase and cyclooxygenase gene expression in human breast cancer specimens. Cancer Lett 1999;140:27–35.[CrossRef][Medline]

47. Agarwal VR, Bulun SE, Leitch M, Rohrich R, Simpson ER. Use of alternative promoters to express the aromatase cytochrome P450 (CYP19) gene in breast adipose tissues of cancer-free and breast cancer patients. J Clin Endocrinol Metab 1996;81:3843–9.[Abstract/Free Full Text]

48. Chen S, Zhou D, Okubo T, Kao YC, Yang C. Breast tumor aromatase: functional role and transcriptional regulation. Endocr Relat Cancer 1999;6:149–56.[Abstract]

49. Diaz-Cruz ES, Shapiro CL, Brueggemeier RW. Cyclooxygenase inhibitors suppress aromatase expression and activity in breast cancer cells. J Clin Endocrinol Metab 2005;90:2563–70.[Abstract/Free Full Text]

50. Prosperi JR Robertson FM. Cyclooxygenase-2 directly regulates gene expression of P450 Cyp19 aromatase promoter regions pII, pI.3 and pI.7 and estradiol production in human breast tumor cells. Prostaglandins Other Lipid Mediat 2006;81:55–70.[CrossRef][Medline]

51. Zhao Y, Agarwal VR, Mendelson CR, Simpson ER. Estrogen biosynthesis proximal to a breast tumor is stimulated by PGE2 via cyclic AMP, leading to activation of promoter II of the CYP19 (aromatase) gene. Endocrinology 1996;137:5739–42.[CrossRef][Medline]

52. Rubin GL, Duong JH, Clyne CD et al . Ligands for the peroxisomal proliferator-activated receptor and the retinoid X receptor inhibit aromatase cytochrome P450 (CYP19) expression mediated by promoter II in human breast adipose. Endocrinology 2002;143:2863–71.[CrossRef][Medline]

53. Zhang X, Podsypanina K, Huang S et al . Estrogen receptor positivity in mammary tumors of Wnt-1 transgenic mice is influenced by collaborating oncogenic mutations. Oncogene 2005;24:4220–31.[CrossRef][Medline]

54. Mann M, Sheng H, Shao J et al . Targeting cyclooxygenase 2 and HER-2/neu pathways inhibits colorectal carcinoma growth. Gastroenterology 2001;120:1713–9.[CrossRef][Medline]

55. Grubbs CJ, Lubet RA, Atigadda VR et al . Efficacy of new retinoids in the prevention of mammary cancers and correlations with short-term biomarkers. Carcinogenesis 2006;27:1232–9.[Abstract/Free Full Text]

This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Brown, P. H. Articles by Howe, L. R. PubMed Articles by Brown, P. H. Articles by Howe, L. R. Related Collections Preclinical Intervention Preclinical Intervention: In Vivo (Animals): Drugs, Nutritional Interventions, Mechanisms