Cyclooxygenase-2 mRNA expression correlates with aromatase expression in human breast cancer

Obesity and endocrine therapy resistance in breast cancer: Mechanistic insights and perspectives

The incidence of obesity, a recognized risk factor for various metabolic and chronic diseases, including numerous types of cancers, has risen dramatically over the recent decades worldwide. To date, convincing research in this area has painted a complex picture about the adverse impact of high body adiposity on breast cancer onset and progression. However, an emerging but overlooked issue of clinical significance is the limited efficacy of the conventional endocrine therapies with selective estrogen receptor modulators (SERMs) or degraders (SERDs) and aromatase inhibitors (AIs) in patients affected by breast cancer and obesity. The mechanisms behind the interplay between obesity and endocrine therapy resistance are likely to be multifactorial. Therefore, what have we actually learned during these years and which are the main challenges in the field? In this review, we will critically discuss the epidemiological evidence linking obesity to endocrine therapeutic responses and we will outline the molecular players involved in this harmful connection. Given the escalating global epidemic of obesity, advances in understanding this critical node will offer new precision medicine-based therapeutic interventions and more appropriate dosing schedule for treating patients affected by obesity and with breast tumors resistant to endocrine therapies.

Association between Cyclooxygenase-2 and Indoleamine 2,3-Dioxygenase Expression in Breast Cancer Patients from Pakistan

Background:

Tumors use several immunosuppressive mechanisms to evade immune destruction. Cyclooxygenase-2 (COX-2) expression may be a driver of immunosuppression in breast cancer, but the mechanisms involved remain elusive. COX-2 expression induces the expression of indoleamine 2,3 dioxygenase (IDO) in tumor cells. IDO is an immunosuppressive enzyme which is involved in tumor immune escape mechanisms in breast cancer. Our aim was to evaluate the association between COX-2 and IDO expression to find evidence of immunosuppression in Pakistani breast cancer patients.

Methods:

Immunohistochemical analysis was performed to evaluate the expression of COX-2, IDO, estrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor 2 (HER2) on formalin-fixed paraffin-embedded breast cancer tissues of 100 patients. Univariable and multivariable logistic regression model was used to identify the independent risk factors of COX-2.

Results:

A total of 100 patients were included with a mean age and standard deviation of 48.28 ± 11.83. A significant association was observed among COX-2, IDO, ER, PR and tumor grade. In multivariable analysis, three variables were identified as significant independent risk factors for high COX-2: IDO expression high; [adjusted odds ratio (AOR) 6.51; 95% confidence interval (CI) (2.00-21.20), p=0.001], ER; [AOR 5.62; 95% CI (1.80-17.84), p=0.002] and age [AOR 1.04; 95% CI (1.00-1.10), p=0.05] respectively.

Conclusion:

Our data showed that high IDO expression is associated with high COX-2 expression in Pakistani breast cancer patients. The co-expression of both enzymes may suggest their role in disease pathogenesis. Hence the concurrent targeting of COX-2 and IDO may be a promising therapy for breast cancer.

Effects and mechanism of downregulation of COX‑2 expression by RNA interference on proliferation and apoptosis of human breast cancer MCF‑7 cells

The aim of the present study was to investigate the effects of RNA interference with prostaglandin-endoperoxide synthase 2 (COX‑2) gene on the proliferation and apoptosis of breast cancer MCF‑7 cells, as well as the underlying mechanism. The present study constructed the eukaryotic expression vector of the targeted COX‑2 gene, transfected the MCF‑7 cells and screened the stably expressed clone. Changes in the COX‑2 gene expression in breast cancer MCF‑7 cells prior to and following transfection were examined; the proliferation and apoptosis of MCF‑7 cells were analyzed. Furthermore, changes in the protein levels of survivin, B-cell lymphoma 2 (Bcl‑2) and Bcl-2-associated X (Bax) genes were detected. RNA interference mediated by a lentiviral expression vector significantly decreased the protein expression levels of the COX‑2 gene, and therefore, the proliferation and growth of breast cancer MCF‑7 cells was significantly suppressed and the apoptotic rate increased. Of note, the mRNA and protein expression levels of survivin and Bcl‑2 decreased, while those of Bax increased following COX-2 silencing. RNA interference markedly deactivated the COX‑2 gene, suppressed the proliferation of breast cancer MCF‑7 cells, and, to a certain extent, enhanced the induced spontaneous apoptosis, which is regulated by the Bax gene. These results provided evidence for the potential applications of RNA interference of the targeted COX‑2 gene in gene therapy for the treatment of breast cancer.

Molecular pathways: adipose inflammation as a mediator of obesity-associated cancer

The increasing rate of obesity worldwide is predicted to be associated with a surge in diseases. Notably, obesity has been linked to approximately 20% of cancer cases in the United States; obesity is associated with both increased risk and worse outcomes after diagnosis. Altered levels of circulating factors are strongly implicated, including insulin, insulin-like growth factor 1, leptin, adiponectin, and interleukin-6 (IL-6). In addition, increasing attention has focused on the consequences of local adipose inflammation. Inflammatory foci characterized by crown-like structures consisting of dead adipocytes encircled by macrophages occur in white adipose depots, including the breast tissue, of most overweight and obese women. Saturated fatty acids, released as a consequence of obesity-associated lipolysis, induce macrophage activation via Toll-like receptor 4, thereby stimulating NF-κB signaling. This, in turn, activates transcription of proinflammatory genes including COX-2, IL-6, IL-1β, and TNFα. Elevated levels of proinflammatory mediators cause both local and systemic effects. Of particular relevance with regard to breast cancer is increased transcription of the CYP19 gene encoding aromatase, the rate-limiting enzyme for estrogen synthesis. Notably, this obesity-inflammation-aromatase axis provides a plausible explanation for increased rates of postmenopausal, hormone receptor-positive breast cancer associated with obesity and hence may offer targets for interventions to attenuate risk or improve prognosis. Potential approaches include weight reduction, exercise, and suppression of obesity-driven signaling pathways using pharmaceutical or dietary agents. A key future goal is to identify biomarkers that accurately report adipose inflammation, both for identification of at-risk individuals and to assess the efficacy of interventions. Clin Cancer Res; 19(22); 6074-83. ©2013 AACR.

Radiation-enhancement of MDA-MB-231 breast cancer cell invasion prevented by a cyclooxygenase-2 inhibitor

BACKGROUND

Recent evidences support that radiation can promote the invasion of cancer cells. As interactions between cancer cells and surrounding stromal cells can have an important role in tumour progression, we determined whether an irradiation to fibroblasts can enhance the invasiveness of breast cancer cells. The role of cyclooxygenase-2 (COX-2), an inflammatory enzyme frequently induced by radiotherapy, was investigated.

METHODS

Irradiated 3T3 fibroblasts were plated in the lower compartment of invasion chambers and used as chemoattractant for non-irradiated human breast cancer cell MDA-MB-231, which are oestrogen receptor negative (ER(-)) and the oestrogen receptor positive (ER(+)) MCF-7 cells. Stimulation of COX-2 expression in irradiated 3T3 cells was measured by a semi-quantitative qPCR and western blot. Capacity of the major product of COX-2, the prostaglandin E2 (PGE(2)), to stimulate the production of the matrix metalloproteinase-2 (MMP-2) and cancer cell invasion were assessed with a zymography gel and invasion chambers.

RESULTS

Irradiation (5 Gy) of 3T3 fibroblasts increased COX-2 expression and enhanced by 5.8-fold the invasiveness of non-irradiated MDA-MB-231 cells, while their migration was not modified. Addition of the COX-2 inhibitor NS-398 completely prevented radiation-enhancement of cancer cell invasion. Further supporting the potential role of COX-2, addition of PGE(2) has increased cancer cell invasion and release of MMP-2 from the MDA-MB-231 cells. This effect of radiation was dependant on the expression of membrane type 1 (MT1)-MMP, which is required to activate the MMP-2, but was not associated with the ER status. Although irradiated fibroblasts stimulated the invasiveness of MDA-MB-231 ER(-) cells, no enhancement was measured with the ER(+) cell line MCF-7.

CONCLUSIONS

Radiation-enhancement of breast cancer cell invasion induced by irradiated 3T3 fibroblasts is not dependant on the ER status, but rather the expression of MT1-MMP. This adverse effect of radiation can be prevented by a specific COX-2 inhibitor.

Rofecoxib augments anticancer effects by reversing intrinsic multidrug resistance gene expression in BGC-823 gastric cancer cells

OBJECTIVE

To investigate combined chemotherapeutic effects of rofecoxib in combination with 5-fluorouracil (5-FU), cisplatin (DDP) and etoposide (VP-16) in vitro, and to explore the potential mechanisms in modulating multidrug resistance (MDR) expression.

METHODS

The BGC-823 gastric cancer cell line was incubated for 48 h with 0.1 micromol/L rofecoxib, 5-FU, DDP and VP-16 (1 microg/mL, 10 microg/mL and 100 microg/mL) alone, and combined with rofecoxib, respectively. Methyl-thiazolyl-tetrazolium and the terminal deoxynucleotidyl transferase-mediated 2'-deoxyuridine 5'-yriphosphate nick-end labeling assays were performed to calculate inhibitory rates and apoptotic index. Middle effects principles (CI values) were used to determine the interaction between rofecoxib and chemotherapeutic agents. Reverse transcription-polymerase chain reaction (RT-PCR) and Western blot analysis were employed to determine expression of MDR1, multidrug resistance-associated protein 1 (MRP1), glutathione S-tranferase-pi (GST-pi) mRNA and protein in gastric cancer cells administered by rofecoxib, respectively.

RESULTS

Both anticancer drugs such as 5-FU, DDP and VP-16 and rofecoxib inhibited the cells' proliferation and induced apoptosis in a dose-dependent manner, and a more significant inhibition was achieved when the cells were co-treated with anticancer drugs and rofecoxib. There was a synergetic role when different concentrations of chemotherapeutic agents were combined with rofecoxib (all CI < 1, P < 0.01 or 0.05). RT-PCR analyses of MDR gene families in BGC-823 gastric cancer cells revealed a strong expression in MRP1 and GST-pi mRNA, but MDR1 mRNA was undetectable. After administration with different concentrations of rofecoxib (0.1, 1.0, 10 micromol/L), significant downregulation of MRP1 and GST-pi mRNA was observed (MRP1: from 0.984 +/- 0.093-0.513 +/- 0.098; GST-pi: from 1.078 +/- 0.201-0.472 +/- 0.084, P < 0.01 or 0.05). In addition, MRP1 and GST-pi protein expression induced by rofecoxib were also reduced (P < 0.01 or 0.05).

CONCLUSION

Rofecoxib, a specific cyclooxygenase-2 inhibitor, plays a chemotherapeutic sensitizer role in various anticancer agents on the BGC-823 gastric cancer cell line, which could be partly explained by its ability to reverse the intrinsic MRP1 and GST-piin vitro.

Inhibition of cyclooxygenase-2 down-regulates aromatase activity and decreases proliferation of Leydig tumor cells

Our recent studies have revealed that estrogens stimulate an autocrine mechanism determining Leydig tumor cell proliferation. Estrogen overproduction is due to an elevated steroidogenic factor-1 (SF-1) expression and cAMP-response element-binding protein (CREB) phosphorylation, both inducing aromatase overexpression. Although we have shown that increased SF-1 expression depends mainly on higher local insulin-like growth factor I production, the mechanisms and factors determining increased CREB activation in Leydig tumor cells are not completely understood. In this study, we investigated the role of cyclooxygenase-2 (COX-2) in CREB dependent-aromatase expression in Leydig tumor cells. We found that COX-2 is expressed in rat and human Leydigiomas as well as in the rat Leydig tumor cell line R2C, but not in normal testis. Our data indicate that in R2C cells the COX-2-derived prostaglandin E2 (PGE2) binds the PGE2 receptor EP4 and activates protein kinase A (PKA) and ultimately CREB. Inhibitors for COX-2 (NS398), EP4 (AH23848), and PKA (H89) decreased aromatase expression and activity as a consequence of a decreased phosphorylated CREB recruitment to the PII promoter of the aromatase gene. The COX-2/PGE2/PKA pathway also seems to be involved in aromatase post-translational activation, an observation that requires further studies. The reduction in aromatase activity was responsible for a drop in estrogen production and subsequent reduction in cyclin E expression resulting in a decrease in tumor Leydig cell proliferation. Furthermore, COX-2 silencing caused a significant decrease in CREB phosphorylation, aromatase expression, and R2C cell proliferation. These novel findings clarify the mechanisms involved in the growth of Leydig cell tumors and should be taken into account in determining new therapeutic approaches.

Elevated aromatase expression correlates with cervical carcinoma progression

OBJECTIVES

We have previously demonstrated that aromatase mRNA is induced in cervical carcinomas compared to normal tissue, suggesting that in situ aromatase expression leading to elevated local estrogen production may contribute to cervical carcinogensis. Our objectives are to examine 1) whether aromatase protein and activity are induced in cervical carcinomas, 2) aromatase expression correlates with disease stage, and 3) inflammatory cytokines (e.g., IL-6 and TNFalpha) may correlate with aromatase expression.

METHODS

RNA and protein were isolated from human cervical carcinomas and normal cervical biopsies to examine aromatase expression, using real-time RT-PCR, Western blot analysis, and immunohistochemistry. Aromatase activity in tissue was measured using the tritiated water release method. IL-6 and TNFalpha expression was also examined.

RESULTS

Aromatase protein and activity levels were increased in cervical carcinomas compared to normal tissue. RNA levels correlated significantly with disease progression, with highest aromatase expression detected in stage IV tumors (p<0.001, R(2)=0.77). Aromatase promoters 1.3 and 1.4 were elevated in cervical carcinomas and in cervical cancer cells. The expression of inflammatory cytokines IL-6 and TNFalpha, known to induce aromatase, significantly correlated with aromatase expression (R(2)>0.9). TNFalpha treatment induced aromatase expression in cervical cancer cells.

CONCLUSION

Increased aromatase protein and activity in cervical carcinomas and the correlation of its expression with disease stage implicates it in cervical carcinogenesis. The correlation of IL-6 and TNFalpha expression with aromatase suggests that these inflammatory cytokines may induce aromatase expression, which is confirmed by induction of aromatase expression due to TNFalpha treatment of cervical cancer cells.

In situ aromatase expression in primary tumor is associated with estrogen receptor expression but is not predictive of response to endocrine therapy in advanced breast cancer

Background

New, third-generation aromatase inhibitors (AIs) have proven comparable or superior to the anti-estrogen tamoxifen for treatment of estrogen receptor (ER) and/or progesterone receptor (PR) positive breast cancer. AIs suppress total body and intratumoral estrogen levels. It is unclear whether in situ carcinoma cell aromatization is the primary source of estrogen production for tumor growth and whether the aromatase expression is predictive of response to endocrine therapy. Due to methodological difficulties in the determination of the aromatase protein, COX-2, an enzyme involved in the synthesis of aromatase, has been suggested as a surrogate marker for aromatase expression.

Methods

Primary tumor material was retrospectively collected from 88 patients who participated in a randomized clinical trial comparing the AI letrozole to the anti-estrogen tamoxifen for first-line treatment of advanced breast cancer. Semi-quantitative immunohistochemical (IHC) analysis was performed for ER, PR, COX-2 and aromatase using Tissue Microarrays (TMAs). Aromatase was also analyzed using whole sections (WS). Kappa analysis was applied to compare association of protein expression levels. Univariate Wilcoxon analysis and the Cox-analysis were performed to evaluate time to progression (TTP) in relation to marker expression.

Results

Aromatase expression was associated with ER, but not with PR or COX-2 expression in carcinoma cells. Measurements of aromatase in WS were not comparable to results from TMAs. Expression of COX-2 and aromatase did not predict response to endocrine therapy. Aromatase in combination with high PR expression may select letrozole treated patients with a longer TTP.

Conclusion

TMAs are not suitable for IHC analysis of in situ aromatase expression and we did not find COX-2 expression in carcinoma cells to be a surrogate marker for aromatase. In situ aromatase expression in tumor cells is associated with ER expression and may thus point towards good prognosis. Aromatase expression in cancer cells is not predictive of response to endocrine therapy, indicating that in situ estrogen synthesis may not be the major source of intratumoral estrogen. However, aromatase expression in combination with high PR expression may select letrozole treated patients with longer TTP.

Trial registration

Sub-study of trial P025 for advanced breast cancer.

The role of cyclooxygenase-2 in breast cancer: review

There is a growing body of evidence that COX-2 expression s a fundamental step in breast cancer pathogenesis acting through prostaglandin-dependent and independent mechanisms. Epidemiological studies suggest that NSAIDs confer a moderate degree of benefit against breast cancer. However further work is required to establish how this enzyme system can be best manipulated for therapeutic benefit.