Progesterone receptor action: defining a role in breast cancer

Re-inforcing the cell death army in the fight against breast cancer

Metastatic breast cancer is responsible for most breast cancer-related deaths. Disseminated cancer cells have developed an intrinsic ability to resist anchorage-dependent apoptosis (anoikis). Anoikis is caused by the absence of cellular adhesion, a process that underpins lumen formation and maintenance during mammary gland development and homeostasis. In healthy cells, anoikis is mostly governed by B-cell lymphoma-2 (BCL2) protein family members. Metastatic cancer cells, however, have often developed autocrine BCL2-dependent resistance mechanisms to counteract anoikis. In this Review, we discuss how a pro-apoptotic subgroup of the BCL2 protein family, known as the BH3-only proteins, controls apoptosis and anoikis during mammary gland homeostasis and to what extent their inhibition confers tumor suppressive functions in metastatic breast cancer. Specifically, the role of the two pro-apoptotic BH3-only proteins BCL2-modifying factor (BMF) and BCL2-interacting mediator of cell death (BIM) will be discussed here. We assess current developments in treatment that focus on mimicking the function of the BH3-only proteins to induce apoptosis, and consider their applicability to restore normal apoptotic responses in anchorage-independent disseminating tumor cells.

Impact of combining the progesterone receptor and preoperative endocrine prognostic index (PEPI) as a prognostic factor after neoadjuvant endocrine therapy using aromatase inhibitors in postmenopausal ER positive and HER2 negative breast cancer

The preoperative endocrine prognostic index (PEPI) predicts survival after neoadjuvant endocrine therapy (NAE) using aromatase inhibitors (AIs) for women with postmenopausal estrogen receptor (ER)-positive breast cancer irrespective of the human epidermal growth factor receptor 2 (HER2) status. Although the progesterone receptor (PgR) is also a prognostic factor for ER-positive breast cancer, the PgR status was not considered a prognostic factor in the original PEPI scoring system. In this study, we investigated the utility of a modified PEPI including the PgR status (PEPI-P) as a prognostic factor after NAE for postmenopausal patients with ER-positive and HER2-negative breast cancer. We enrolled 107 patients with invasive ER-positive and HER2-negative breast cancer treated with exemestane for ≥4 months as NAE. We initially assessed PEPI and compared survival between the groups. Additionally, we obtained an effective cutoff for PgR through survival analysis. Then, we assessed the survival significance of PEPI-P. A PgR staining rate of 50% was the most significant cutoff for predicting recurrence-free survival (RFS) and cancer-specific survival (CSS). PEPI was a significant prognostic factor; moreover, PEPI-P was the most significant prognostic indicator for RFS and CSS. PEPI-P is a potent prognostic indicator of survival after NAE using AIs for postmenopausal patients with ER-positive and HER2-negative breast cancer. This modified PEPI may be useful for therapeutic decision-making regarding postmenopausal ER-positive and HER2-negative breast cancer after NAE.

Revisiting progesterone receptor (PR) actions in breast cancer: Insights into PR repressive functions

Progesterone receptor (PR) is a master regulator in female reproductive tissues that controls developmental processes and proliferation and differentiation during the reproductive cycle and pregnancy. PR also plays a role in progression of endocrine-dependent breast cancer. As a member of the nuclear receptor family of ligand-dependent transcription factors, the main action of PR is to regulate networks of target gene expression in response to binding its cognate steroid hormone, progesterone. Liganded-PR transcriptional activation has been thoroughly studied and associated mechanisms have been described while progesterone-mediated repression has remained less explored. The present work summarizes recent advances in the understanding of how PR-mediated repression is accomplished in breast cancer cells and highlights the significance of fully understanding the determinants of context-dependent PR action.

Fibroblast growth factor signalling induces loss of progesterone receptor in breast cancer cells

We have recently demonstrated that, fibroblast growth factor 2 (FGFR2), signalling via ribosomal S6 kinase 2 (RSK2), promotes progression of breast cancer (BCa). Loss of progesterone receptor (PR), whose activity in BCa cells can be stimulated by growth factor receptors (GFRs), is associated with poor patient outcome. Here we showed that FGF7/FGFR2 triggered phosphorylation of PR at Ser294, PR ubiquitination and subsequent receptor`s degradation via the 26S proteasome pathway in BCa cells. We further demonstrated that RSK2 mediated FGF7/FGFR2-induced PR downregulation. In addition, a strong synergistic effect of FGF7 and progesterone (Pg), reflected in the enhanced anchorage-independent growth and cell migration, was observed. Analysis of clinical material demonstrated that expression of PR inversely correlated with activated RSK (RSK-P) (p = 0.016). Patients with RSK-P(+)/PR(–) tumours had 3.629-fold higher risk of recurrence (p = 0.002), when compared with the rest of the cohort. Moreover, RSK-P(+)/PR(–) phenotype was shown as an independent prognostic factor (p = 0.006). These results indicate that the FGF7/FGFR2-RSK2 axis promotes PR turnover and activity, which may sensitize BCa cells to stromal stimuli and contribute to the progression toward steroid hormone negative BCa.

Cancer molecular markers: A guide to cancer detection and management

Cancer is generally caused by the molecular alterations which lead to specific mutations. Advances in molecular biology have provided an impetus to the study of cancers with valuable prognostic and predictive significance. Over the hindsight various attempts have been undertaken by scientists worldwide, in the management of cancer; where, we have witnessed a number of molecular markers which allow the early detection of cancers and lead to a decrease in its mortality rate. Recent advances in oncology have led to the discovery of cancer markers that has allowed early detection and targeted therapy of tumors. In this context, current review provides a detail outlook on various molecular markers for diagnosis, prognosis and management of therapeutic response in cancer patients.

Association of rs1801157 single nucleotide polymorphism of CXCL12 gene in breast cancer in Pakistan and in-silico expression analysis of CXCL12-CXCR4 associated biological regulatory network

Background

C-X-C chemokine ligand 12 (CXCL12) has important implications in breast cancer (BC) pathogenesis. It is selectively expressed on B and T lymphocytes and is involved in hematopoiesis, thymocyte trafficking, stem cell motility, neovascularization, and tumorigenesis. The single nucleotide polymorphism (SNP) rs1801157 of CXCL12 gene has been found to be associated with higher risk of BC.

Methods

Our study focuses on the genotypic and allelic distribution of SNP (rs1801157; G/A) in Pakistani population as well as its association with the clinico-pathological features. The association between rs1801157 genotypes (G/A) and BC risks was assessed by a multivariate logistic regression (MLR) analysis. Genotyping was performed in both healthy individuals and patients of BC using PCR-restriction fragment length polymorphism (PCR-RFLP) method. Furthermore, in-silico approaches were adapted to investigate the association of CXCL12 and its receptor CXCR4 with genes/proteins involved in BC signalling.

Results

Significant differences in allelic and genotypic distribution between BC patients and healthy individuals of genotype (G/G) and (A/G) (p < 0.05) were observed. The frequency of the allele G in the BC group (77%) was significantly higher as compared to control group (61%) (p = 0.01). The association of genotype GG with clinico-pathological features including age, stages of cancer and organ (lung, liver, bones and brain) metastasis (p > 0.05) was assessed. In a MLR analysis, a number of variables including age, weight of an individual, affected lymph nodes, hormonal status (estrogen and progesterone receptor), alcohol consumption and family history associated with the GG genotype (GG:AA, odds ratio (OR) = 1.30, 95% CI [1.06–1.60]) were found to be independent risk factors for BC. Our in-vitro results suggest that genotype GG is possibly increasing the risk of BC in Pakistani cohorts. in-silico analysis finds that CXCL12–CXCR4 is associated with an increased expression of PDZK1, PI3k and Akt which lead the breast tumor towards metastasis.

Conclusion

Multiple targets such as CXCL12, CXCR4, PDZK1, PI3k and Akt can be inhibited in combined strategies to treat BC metastasis.

The role of progesterone and the progesterone receptor in cancer

There is an abundance of accumulating data strongly suggesting there is a key role for the progesterone receptor in the molecular events effecting the growth or containment of a variety of cancers. This knowledge should lead to novel new strategies to combat various cancers, including drugs classified as progesterone receptor modulators or monoclonal antibodies against some of the key proteins needed for cancer proliferation by suppressing immune surveillance. Areas covered: The role of the classic nuclear receptor and molecular events needed for proliferation are reviewed including cancers of the breast, endometrium, prostate, thyroid, and leiomyomas and leiomyosarcoma. The potential role of non-genomic membrane progesterone receptors is reviewed. The prognostic role of the presence of progesterone receptors is also discussed. Over 1000 research publications were read after conducting a PubMed search. Expert commentary: Discussion is made about a unique immunomodulatory protein called the progesterone induced blocking factor (PIBF). The role of this protein, that is unique to rapidly growing cells, may hold a key to how the cancer cells escape immune surveillance. Thus, techniques to suppress the intracytoplasmic isoforms of PIBF may play a significant role in the fight against all cancers, not just the ones with the classic nuclear progesterone receptors.

S100β as a serum marker in endocrine resistant breast cancer

BACKGROUND

Endocrine therapy is standard treatment for estrogen receptor (ER)-positive breast cancer. However, its efficacy is limited by intrinsic and acquired resistance. Here the potential of S100β as a biomarker and inhibition of its signaling network as a therapeutic strategy in endocrine treated patients was investigated.

METHODS

The expression of S100β in tissue and serum was assessed by immunohistochemistry and an enzyme-linked immunosorbent assay, respectively. The S100β signaling network was investigated in cell line models of endocrine resistance by western blot, PCR, immunoprecipitation, and chromatin-immunoprecipitation. Endocrine resistant xenografts and tumor explants from patients with resistant tumors were treated with endocrine therapy in the presence and absence of the p-Src kinase inhibitor, dasatinib.

RESULTS

Tissue and serum levels of S100β were found to predict poor disease-free survival in endocrine-treated patients (n = 509, HR 2.32, 95% CI is 1.58-3.40, p < 0.0001 and n = 187, HR 4.009, 95% CI is 1.66-9.68, p = 0.002, respectively). Moreover, elevated levels of serum S100β detected during routine surveillance over the patient treatment period significantly associated with subsequent clinically confirmed disease recurrence (p = 0.019). In vivo studies demonstrated that endocrine treatment induced transcriptional regulation of S100β which was successfully disrupted with tyrosine kinase inhibition. In endocrine resistant xenografts and tumor explants from patients with endocrine resistant breast cancer, combined endocrine and dasatinib treatment reduced tumor proliferation and down-regulated S100β protein expression in comparison to endocrine treatment alone.

CONCLUSIONS

S100β has potential as a new surveillance tool for patients with ER-positive breast cancer to monitor ongoing response to endocrine therapy. Moreover, endocrine resistant breast cancer patients with elevated S100β may benefit from combined endocrine and tyrosine-kinase inhibitor treatment.

TRIAL REGISTRATION

ClinicalTrials.gov,  NCT01840293 ). Registered on 23 April 2013. Retrospectively registered.

Dissecting the Biology of Menstrual Cycle-Associated Breast Cancer Risk

Fluctuations in circulating estrogen and progesterone across the menstrual cycle lead to increased breast cancer susceptibility in women; however, the biological basis for this increased risk is not well understood. Estrogen and progesterone have important roles in normal mammary gland development, where they direct dynamic interactions among the hormonally regulated mammary epithelial, stromal, and immune cell compartments. The continuous fluctuations of estrogen and progesterone over a woman’s reproductive lifetime affect the turnover of mammary epithelium, stem cells, and the extracellular matrix, as well as regulate the phenotype and function of mammary stromal and immune cells, including macrophages and regulatory T cells. Collectively, these events may result in genome instability, increase the chance of random genetic mutations, dampen immune surveillance, and promote tolerance in the mammary gland, and thereby increase the risk of breast cancer initiation. This article reviews the current status of our understanding of the molecular and the cellular changes that occur in the mammary gland across the menstrual cycle and how continuous menstrual cycling may increase breast cancer susceptibility in women.

Progesterone Receptors, Pathological Complete Response and Early Outcome for Locally Advanced Breast Cancer - a Single Centre Study. (PPLB - 01)

Neoadjuvant chemotherapy (NACT) for locally advanced breast cancer (LABC), apart from increasing breast conservation rates, also provides an opportunity to assess tumour response to chemotherapy, with Pathological Complete Response (pCR) described as an independent prognostic factor and a surrogate marker for better outcome and survival. Our primary aim was to identify clinical and pathological factors associated with pCR following NACT in patients with LABC treated at our institution. Our secondary aim was to analyze the impact of pCR and associated factors on disease free survival (DFS) and overall survival (OS). A retrospective analysis of LABC patients treated with NACT between Jun 2011 and Dec 2013. Clinical and histological variables were analyzed for association with pCR (no invasive or in situ carcinoma in breast or axillary lymph nodes). Kaplan-Meier curves and Cox regression model was used for survival analysis. All values were twosided, and statistical significance was defined as p < 0.05. 240 patients were included. The median tumor size was 6 cm, with T4 disease in 49.8 %. 45 % of tumors were of low grade (G1 + G2) and 53.8 % of high grade (G3). Estrogen Receptor (ER) was positive in 70.8 %, progesterone receptor (PR) in 53.3 % and Her2 in 38.8 %. The preferred NACT regimen was sequential anthracycline and taxane and 88.8 % of patients received this regimen. Of 93 potential Her2 Positive patients, only 23 received trastuzumab. Overall 23.2 % patients had pCR. At median follow up of 21 months (range, 3-42), 16.3 % of patients had recurrent disease, and 6.7 % had died. High tumor grade (p = 0.04), PR negative status (p < 0.01) and trastuzumab treatment (p = 0.01) were significant predictors of pCR in univariate analysis. On multivariate analysis PR negativity (OR 3.2, 95 % CI = 1.6 to 6.04, p = 0.001) and Trastuzumab use (OR 0.24, 95 % CI = 0.1 to 0.6, p = 0.004) were significant. Patients with pCR had positive associations with survival (p < .02,OS& .02,DFS) and interestingly PR positivity had positive association with DFS (p = 0.02) in Kaplan-Meier curves. On Cox regression, PR positivity (HR = 0.3, p < 0.01) and pCR (HR = 0.2, p < 0.01) correlated with DFS, though not with early OS. for the PR positive patients were paradoxical. Though less likely to have pCR (15 %, vs 32 % if PR negative), they had better DFS (p = 0.02), and achieving pCR had no survival benefit in this group. In contrast, PR negative patients, irrespective of ER status, had a high pCR rate, and achieving pCR had survival advantage (p < 0.05,DFS& p < 0.02,OS). PR negative patients without pCR had the worst DFS (p < 0.01) among all. High grade and Trastuzumab treatment as predictors of pCR, and pCR as a surrogate marker for survival are well recognized, and are supported by our findings. In present cohort, PR negativity showed prognostic importance independent of ER status. However these results were derived from sub-group, post-hoc analysis of data from a pre-existing cohort, without 'a-priori' hypothesis for survival analysis in relation to PR. These "hypothesis generating" results need confirmation by a well-designed prospective cohort or a randomized trial.

Phosphorylated-p38 mitogen-activated protein kinase expression is associated with clinical factors in invasive breast cancer

Purpose

P38 mitogen-activated protein kinases (MAPK) level is an important prognostic factor in breast cancer. This study was performed to detect the expressions of P-p38 MAPK expression in breast cancer and explore their correlations with clinicopathological factors.

Experimental design

Tumor samples from 355 Chinese patients diagnosed with invasive breast cancer and adjacent non-cancerous tissue were collected between 2003 and 2010. The expression of P-p38 MAPK was analyzed using immunohistochemical staining. The correlations between P-p38 MAPK expression and clinicopathological findings including age, AJCC Stage, Histologic characters, ER, PR, and HER2 were analyzed using the parametric correlation method. P-p38 MAPK was selected as dependent variable to perform multivariate analysis respectively at last.

Results

Overall, 161 (45 %) and 183 (52 %) of the 355 specimens showed positive P-p38 MAPK staining in the cytoplasm and nucleus respectively, which were significant higher than that in the adjacent non-cancerous tissues in both the cytoplasm and the nucleus. High P-p38 MAPK expression of cytoplasm and nucleus were both associated with positive PR status in luminal A/B type of breast cancer, and were both associated with positive HER2 status in HER2-positive type of breast cancer. The result of multivariate analysis demonstrated that HER2 and PR were both significantly association with P-p38 MAPK expression of cytoplasm and nucleus.

Conclusions

Our study suggests that P-p38 MAPK expression were significantly associated with clinicopathological factors and PR/HER2 might association with phosphorylation of p38 MAPK in different types of breast cancer.

Genomic agonism and phenotypic antagonism between estrogen and progesterone receptors in breast cancer

The functional role of progesterone receptor (PR) and its impact on estrogen signaling in breast cancer remain controversial. In primary ER(+) (estrogen receptor-positive)/PR(+) human tumors, we report that PR reprograms estrogen signaling as a genomic agonist and a phenotypic antagonist. In isolation, estrogen and progestin act as genomic agonists by regulating the expression of common target genes in similar directions, but at different levels. Similarly, in isolation, progestin is also a weak phenotypic agonist of estrogen action. However, in the presence of both hormones, progestin behaves as a phenotypic estrogen antagonist. PR remodels nucleosomes to noncompetitively redirect ER genomic binding to distal enhancers enriched for BRCA1 binding motifs and sites that link PR and ER/PR complexes. When both hormones are present, progestin modulates estrogen action, such that responsive transcriptomes, cellular processes, and ER/PR recruitment to genomic sites correlate with those observed with PR alone, but not ER alone. Despite this overall correlation, the transcriptome patterns modulated by dual treatment are sufficiently different from individual treatments, such that antagonism of oncogenic processes is both predicted and observed. Combination therapies using the selective PR modulator/antagonist (SPRM) CDB4124 in combination with tamoxifen elicited 70% cytotoxic tumor regression of T47D tumor xenografts, whereas individual therapies inhibited tumor growth without net regression. Our findings demonstrate that PR redirects ER chromatin binding to antagonize estrogen signaling and that SPRMs can potentiate responses to antiestrogens, suggesting that cotargeting of ER and PR in ER(+)/PR(+) breast cancers should be explored.

Stromal markers AKR1C1 and AKR1C2 are prognostic factors in primary human breast cancer

BACKGROUND

Stromal fibroblasts influence tumor growth and progression. We evaluated two aldo-keto reductases, AKR1C1 and AKR1C2, in stromal fibroblasts and carcinoma cells as prognostic factors in primary human breast cancer. They are involved in intratumoral progesterone metabolism.

METHODS

Immunohistochemistry was performed on tissue microarrays from 504 core biopsies from breast cancer patients. Primary endpoints were disease-free (DFS) and overall (OS) survival.

RESULTS

AKR1C1 and AKR1C2 expression in fibroblasts and tumor cells correlated with favorable tumor characteristics, such as small tumor size and negative nodal status. In univariate analysis, AKR1C1 expression in carcinoma cells correlated positively with DFS und OS; AKR1C2 expression in both fibroblasts and tumor cells also showed a positive correlation with DFS and OS. In multivariate analysis, AKR1C1 expression in carcinoma cells was an independent prognostic marker.

CONCLUSION

It can be assumed that our observations are due to the independent regulatory function of AKR1C1/2 in progesterone metabolism and therefore provide a basis for new hormone-based therapy options for breast cancer patients, independent of classic hormone receptor status.

Heregulin Co-opts PR Transcriptional Action Via Stat3 Role As a Coregulator to Drive Cancer Growth

Accumulated findings have demonstrated the presence of bidirectional interactions between progesterone receptor (PR) and the ErbB family of receptor tyrosine kinases signaling pathways in breast cancer. We previously revealed signal transducer and activator of transcription 3 (Stat3) as a nodal convergence point between said signaling pathways proving that Stat3 is activated by one of the ErbBs' ligands, heregulin (HRG)β1 via ErbB2 and through the co-option of PR as a signaling molecule. Here, we found that HRGβ1 induced Stat3 recruitment to the promoters of the progestin-regulated cell cycle modulators Bcl-XL and p21(CIP1) and also stimulated Stat3 binding to the mouse mammary tumor virus promoter, which carries consensus progesterone response elements. Interestingly, HRGβ1-activated Stat3 displayed differential functions on PR activity depending on the promoter bound. Indeed, Stat3 was required for PR binding in bcl-X, p21(CIP1), and c-myc promoters while exerting a PR coactivator function on the mouse mammary tumor virus promoter. Stat3 also proved to be necessary for HRGβ1-induced in vivo tumor growth. Our results endow Stat3 a novel function as a coregulator of HRGβ1-activated PR to promote breast cancer growth. These findings underscore the importance of understanding the complex interactions between PR and other regulatory factors, such as Stat3, that contribute to determine the context-dependent transcriptional actions of PR.

Orphan nuclear receptors as drug targets for the treatment of prostate and breast cancers

Nuclear receptors (NRs), a family of 48 transcriptional factors, have been studied intensively for their roles in cancer development and progression. The presence of distinctive ligand binding sites capable of interacting with small molecules has made NRs attractive targets for developing cancer therapeutics. In particular, a number of drugs have been developed over the years to target human androgen- and estrogen receptors for the treatment of prostate cancer and breast cancer. In contrast, orphan nuclear receptors (ONRs), which in many cases lack known biological functions or ligands, are still largely under investigated. This review is a summary on ONRs that have been implicated in prostate and breast cancers, specifically retinoic acid-receptor-related orphan receptors (RORs), liver X receptors (LXRs), chicken ovalbumin upstream promoter transcription factors (COUP-TFs), estrogen related receptors (ERRs), nerve growth factor 1B-like receptors, and ‘‘dosage-sensitive sex reversal, adrenal hypoplasia critical region, on chromosome X, gene 1’’ (DAX1). Discovery and development of small molecules that can bind at various functional sites on these ONRs will help determine their biological functions. In addition, these molecules have the potential to act as prototypes for future drug development. Ultimately, the therapeutic value of targeting the ONRs may go well beyond prostate and breast cancers.

Progesterone action in breast, uterine, and ovarian cancers

Progesterone and progesterone receptors (PRs) are essential for the development and cyclical regulation of hormone-responsive tissues including the breast and reproductive tract. Altered functions of PR isoforms contribute to the pathogenesis of tumors that arise in these tissues. In the breast, progesterone acts in concert with estrogen to promote proliferative and pro-survival gene programs. In sharp contrast, progesterone inhibits estrogen-driven growth in the uterus and protects the ovary from neoplastic transformation. Progesterone-dependent actions and associated biology in diverse tissues and tumors are mediated by two PR isoforms, PR-A and PR-B. These isoforms are subject to altered transcriptional activity or expression levels, differential crosstalk with growth factor signaling pathways, and distinct post-translational modifications and cofactor-binding partners. Herein, we summarize and discuss the recent literature focused on progesterone and PR isoform-specific actions in breast, uterine, and ovarian cancers. Understanding the complexity of context-dependent PR actions in these tissues is critical to developing new models that will allow us to advance our knowledge base with the goal of revealing novel and efficacious therapeutic regimens for these hormone-responsive diseases.

Marginal activity of progesterone receptor B (PR-B) in dogs but high incidence of mammary cancer

Progesterone plays an important role in the normal development and carcinogenesis of the mammary gland. In vitro studies have shown that the canine progesterone receptor B (cPR-B), which is essential for mammary development in the mouse, does not transactivate reporter constructs containing progesterone response elements. Therefore, the question was raised whether the cPR-B was completely devoid of transactivation potential of endogenous progesterone regulated genes. Canine mammary cell lines expressing doxycycline-inducible cPR-B, human PR-B or a chimera in which the canine B-upstream segment (BUS) was replaced by a human BUS were treated for 24h with doxycycline, progesterone or a combination of the two. The expression profiling was subsequently performed using a dog-specific microarray and miRNA primers. Incubation of stably transfected cell lines with doxycycline or progesterone alone, did not change expression of any endogenous gene. Expression of activated human PR-B or the chimera of human BUS with the canine PR resulted in differential expression of >500 genes whereas the activated cPR-B regulated only a subset of 40 genes and to a limited extent. The relevance of the marginal transactivation potential or the consequence of a lack of cPR-B function for the carcinogenesis of mammary gland tumors is discussed.

Crystal structure of the mineralocorticoid receptor DNA binding domain in complex with DNA

The steroid hormone receptors regulate important physiological functions such as reproduction, metabolism, immunity, and electrolyte balance. Mutations within steroid receptors result in endocrine disorders and can often drive cancer formation and progression. Despite the conserved three-dimensional structure shared among members of the steroid receptor family and their overlapping DNA binding preference, activation of individual steroid receptors drive unique effects on gene expression. Here, we present the first structure of the human mineralocorticoid receptor DNA binding domain, in complex with a canonical DNA response element. The overall structure is similar to the glucocorticoid receptor DNA binding domain, but small changes in the mode of DNA binding and lever arm conformation may begin to explain the differential effects on gene regulation by the mineralocorticoid and glucocorticoid receptors. In addition, we explore the structural effects of mineralocorticoid receptor DNA binding domain mutations found in type I pseudohypoaldosteronism and multiple types of cancer.

In pulmonary lymphangioleiomyomatosis expression of progesterone receptor is frequently higher than that of estrogen receptor

Lymphangioleiomyomatosis (LAM) of the lung is a rare low-grade malignancy affecting primarily women of childbearing age. LAM is characterized by the proliferation of SMA and HMB-45 positive spindle-shaped and epithelioid cells throughout the lung in the form of discrete lesions causing cystic destruction and ultimately respiratory insufficiency. LAM occurs sporadically or in patients with tuberous sclerosis complex (TSC) and is etiologically linked to mutations in the TSC1 and TSC2 genes. Although LAM cells are known to express estrogen and progesterone receptors (ER and PR, respectively), their respective expression level was never determined. Therefore, here we measured the immunohistochemical expression of ERs and PRs in a large series of pulmonary LAM cases using the Aperio Spectrum Analysis Platform. Our case series comprised open lung biopsy specimens from 20 LAM patients and lungs explanted during the course of lung transplant from 24 patients. All cases were positive for ER and PR. PR expression was statistically significantly higher than ER in 80 % of the biopsies while ER predominated only in one case. Specimens from explanted cases of LAM had relatively fewer PR-positive nuclei. As a result, PR expression was significantly higher than ER in 38 % of the cases, whereas ER predominated in 33 %. Overall, PR expression predominated in 57 % of cases and ER in 21 %. These data indicate that PR frequently prevails over ER in pulmonary LAM. LAM is unusual in its high PR/ER ratio; other female neoplasms show a definite prevalence of ER. Our findings therefore warrant further study of PR function in LAM.

Progesterone receptor-B enhances estrogen responsiveness of breast cancer cells via scaffolding PELP1- and estrogen receptor-containing transcription complexes

Progesterone and estrogen are important drivers of breast cancer proliferation. Herein, we probed ER-alpha and PR cross-talk in breast cancer models. Stable expression of PR-B in PR-low/ER+ MCF7 cells increased cellular sensitivity to estradiol and IGF1, as measured in growth assays performed in the absence of exogenous progestin; similar results were obtained in PR-null/ER+ T47D cells stably expressing PR-B. Genome-wide microarray analyses revealed that unliganded PR-B induced robust expression of a subset of estradiol-responsive ER-target genes, including CathepsinD (CTSD). Estradiol-treated MCF7 cells stably expressing PR-B exhibited enhanced ER Ser167 phosphorylation and recruitment of ER, PR, and the proline, glutamate and leucine rich protein 1 (PELP1) to an estrogen response element (ERE) in the CTSD distal promoter; this complex co-immunoprecipitated with IGF1R in whole cell lysates. Importantly, ER/PR/PELP1 complexes were also detected in human breast cancer samples. Inhibition of IGF1R or PI3K blocked PR-B-dependent CTSD mRNA upregulation in response to estradiol. Similarly, inhibition of IGF1R or PR significantly reduced ER recruitment to the CTSD promoter. Stable knockdown of endogenous PR or onapristone treatment of multiple unmodified breast cancer cell lines blocked estradiol-mediated CTSD induction, inhibited growth in soft agar, and partially restored tamoxifen-sensitivity of resistant cells. Further, combination treatment of breast cancer cells with both onapristone and IGF1R tyrosine kinase inhibitor AEW541 was more effective than either agent alone. In summary, unliganded PR-B enhanced proliferative responses to estradiol and IGF1 via scaffolding of ERalpha/PELP1/IGF1R-containing complexes. Our data provide a strong rationale for targeting PR in combination with ER and IGF1R in patients with luminal breast cancer.

Progesterone receptor assembly of a transcriptional complex along with activator protein 1, signal transducer and activator of transcription 3 and ErbB-2 governs breast cancer growth and predicts response to endocrine therapy

INTRODUCTION

The role of the progesterone receptor (PR) in breast cancer remains a major clinical challenge. Although PR induces mammary tumor growth, its presence in breast tumors is a marker of good prognosis. We investigated coordinated PR rapid and nonclassical transcriptional effects governing breast cancer growth and endocrine therapy resistance.

METHODS

We used breast cancer cell lines expressing wild-type and mutant PRs, cells sensitive and resistant to endocrine therapy, a variety of molecular and cellular biology approaches, in vitro proliferation studies and preclinical models to explore PR regulation of cyclin D1 expression, tumor growth, and response to endocrine therapy. We investigated the clinical significance of activator protein 1 (AP-1) and PR interaction in a cohort of 99 PR-positive breast tumors by an immunofluorescence protocol we developed. The prognostic value of AP-1/PR nuclear colocalization in overall survival (OS) was evaluated using Kaplan-Meier method, and Cox model was used to explore said colocalization as an independent prognostic factor for OS.

RESULTS

We demonstrated that at the cyclin D1 promoter and through coordinated rapid and transcriptional effects, progestin induces the assembly of a transcriptional complex among AP-1, Stat3, PR, and ErbB-2 which functions as an enhanceosome to drive breast cancer growth. Our studies in a cohort of human breast tumors identified PR and AP-1 nuclear interaction as a marker of good prognosis and better OS in patients treated with tamoxifen (Tam), an anti-estrogen receptor therapy. Rationale for this finding was provided by our demonstration that Tam inhibits rapid and genomic PR effects, rendering breast cancer cells sensitive to its antiproliferative effects.

CONCLUSIONS

We here provided novel insight into the paradox of PR action as well as new tools to identify the subgroup of ER+/PR + patients unlikely to respond to ER-targeted therapies.

Progesterone receptor isoform analysis by quantitative real-time polymerase chain reaction in formalin-fixed, paraffin-embedded canine mammary dysplasias and tumors

Cloning and sequencing of the progesterone receptor gene in dogs have revealed 2 isoforms, A and B, transcribed from a single gene. Distribution of isoforms A and B in canine mammary lesions has hitherto been investigated only by Western blot analysis. This study analyzed progesterone receptor and its isoforms in formalin-fixed, paraffin-embedded tissue samples from canine mammary lesions (4 dysplasias, 10 benign tumors, and 46 carcinomas) using 1-step SYBR Green quantitative real-time polymerase chain reaction (RT-qPCR). Progesterone receptor was expressed in 75% of dysplasias, all benign tumors, and 59% of carcinomas. Carcinomas, and particularly simple epithelial-type carcinomas, displayed the lowest levels of expression. A high rate of agreement was recorded between RT-qPCR and immunohistochemical labeling. Isoforms A and B were successfully amplified, with correlation coefficients of 0.99 and amplification efficiencies close to 2, and were expressed in all lesion types analyzed. Predominance of A over B expression was observed in carcinomas and complex adenomas. Low-grade tumors exhibited higher progesterone receptor messenger RNA (mRNA) levels, but no difference was observed in the expression of isoform A versus B. Analysis of progesterone receptor mRNA isoforms by RT-qPCR was successful in routinely formalin-fixed, paraffin-embedded tissue samples and enabled the distribution of isoforms A and B to be identified for the first time in dysplasias, benign tumors, and malignant tumors of the canine mammary gland. These findings will facilitate future research into the role of progesterone receptor isoforms in the progression of canine mammary tumors.

A Common Docking Domain in Progesterone Receptor-B links DUSP6 and CK2 signaling to proliferative transcriptional programs in breast cancer cells

Progesterone receptors (PR) are transcription factors relevant to breast cancer biology. Herein, we describe an N-terminal common docking (CD) domain in PR-B, a motif first described in mitogen-activated protein kinases. Binding studies revealed PR-B interacts with dual-specificity phosphatase 6 (DUSP6) via the CD domain. Mutation of the PR-B CD domain (mCD) attenuated cell cycle progression and expression of PR-B target genes (including STAT5A and Wnt1); mCD PR-B failed to undergo phosphorylation on Ser81, a ck2-dependent site required for expression of these genes. PR-B Ser81 phosphorylation was dependent on binding with DUSP6 and required for recruitment of a transcriptional complex consisting of PR-B, DUSP6 and ck2 to an enhancer region upstream of the Wnt1 promoter. STAT5 was present at this site in the absence or presence of progestin. Furthermore, phospho-Ser81 PR-B was recruited to the STAT5A gene upon progestin treatment, suggestive of a feed-forward mechanism. Inhibition of JAK/STAT-signaling blocked progestin-induced STAT5A and Wnt1 expression. Our studies show that DUSP6 serves as a scaffold for ck2-dependent PR-B Ser81 phosphorylation and subsequent PR-B-specific gene selection in coordination with STAT5. Coregulation of select target genes by PR-B and STAT5 is likely a global mechanism required for growth promoting programs relevant to mammary stem cell biology and cancer.

Joint detection of multiple immunohistochemical indices and clinical significance in breast cancer

Breast cancer is one of the most common malignancies in women. This study was conducted to analyze the association between the expressions of eight immunohistochemical (IHC) indices and clinicopathological characteristics in breast cancers (BCs) and investigate the clinical significance. IHC Envision ldpe-g-nvp was used to detect the expression of estrogen receptor (ER), progesterone receptor (PR), human epidermal growth factor receptor-2 (HER2), vascular endothelial growth factor (VEGF), epidermal growth factor receptor (EGFR), p53, type II topoisomerase (TOPO II) and Ki-67 in postoperative paraffin blocks of 286 cases of invasive BC and statistically analyzed their correlations with clinicopathological characteristics. The positive rates of ER, PR, HER2, VEGF, p53, EGFR, TOPO II and Ki-67 expression were 62.24, 41.96, 57.34, 53.85, 81.82, 46.85, 54.55 and 69.93%, respectively. ER expression was negatively correlated with age, tumor size and histological grade (P<0.05) and PR expression was negatively correlated with age and histological grade (P<0.05). Among the ER, PR and c-erbB-2 statuses, a significant correlation was observed between ER expression and PR status (P=0.0000), whereas the expression of ER and PR exhibited a negative correlation with HER2 status (P<0.05). We also demonstrated a significant correlation between EGFR expression and lymph node metastasis (P=0.0240), p53 expression and tumor size (P=0.0300), p53 and Ki-67 expression and histological grade (P<0.05) and the expressions of VEGF, EGFR, p53, TOPO II, Ki-67 and HER2 status (P<0.05). In addition, the Luminal B and HER2/neu subtypes exhibited a close correlation with age (P<0.01), while the HER2/neu and triple-negative subtypes were positively correlated with poor histological grade (P<0.05). In conclusion, there is a definite correlation between IHC indices and clinicopathological characteristics in BCs. Combined detection of these indices may be significant in the evaluation of biological behavior and prognosis of BC and thus in the diagnosis and comprehensive treatment of this disease.

The hyperplastic phenotype in PR-A and PR-B transgenic mice: lessons on the role of estrogen and progesterone receptors in the mouse mammary gland and breast cancer

Progesterone receptor (PR) belongs to the superfamily of steroid receptors and mediates the action of progesterone in its target tissues. In the mammary gland, in particular, PR expression is restricted to the luminal epithelial cell compartment. The generation of estrogen receptor-α (ER) and PR knockout mice allowed the specific characterization of the roles of each of these in mammary gland development: ER is critical for ductal morphogenesis, whereas PR has a key role in lobuloalveolar differentiation. To further study the role PR isoforms have in mammary gland biology, transgenic mice overexpressing either the "A" (PR-A) or the "B" (PR-B) isoforms of PR were generated. Overexpression of the A isoform of PR led to increased side branching, multilayered ducts, loss of basement membrane integrity, and alterations in matrix metalloproteinase activation in the mammary gland. Moreover, levels of TGFβ1 and p21 were diminished and those of cyclin D1 increased. Interestingly, the phenotype was counteracted by antiestrogens, suggesting that ER is essential for the manifestation of the hyperplasias. Mice overexpressing the B isoform of PR had limited ductal growth but retained the ability to differentiate during pregnancy. Levels of latent and active TGFβ1 were increased compared to PR-A transgenics. The phenotypes of these transgenic mice are further discussed in the context of the impact of progesterone on mammary stem cells and breast cancer. We conclude that an adequate balance between the A and B isoforms of PR is critical for tissue homeostasis. Future work to further understand the biology of PR in breast biology will hopefully lead to new and effective preventive and therapeutic alternatives for patients.

The role of estrogen, progesterone and aromatase in human non-small-cell lung cancer

Lung cancer is the leading cause of cancer-related deaths in both men and women worldwide. Despite advances in treatment, patients have few effective therapeutic options and survival rates remain low. Emerging evidence suggests that the hormones estrogen and progesterone play a key role in the progression of non-small-cell lung cancer (NSCLC). The aromatase enzyme, which is responsible for a key step in estrogen biosynthesis, elicits higher levels of estrogen in lung tumors as well as in metastases compared with nonmalignant tissues. Thus, aromatase may prove to be a key predictive biomarker for treatment of NSCLC. Epidemiologic and preclinical data show estrogens play a critical role in lung tumor development and progression. Two estrogen receptors, α and β, are expressed in normal and in cancerous lung epithelium, and estrogen promotes gene transcription that stimulates cell proliferation and inhibits cell death. Furthermore, expression of both forms of estrogen receptor, progesterone receptor and aromatase in NSCLC specimens has been correlated with worse clinical outcomes. Combination therapies that include estrogen receptor downregulators and aromatase inhibitors are currently being assessed in Phase I-II clinical trials among patients with advanced NSCLC. Results will help guide future lung cancer management decisions, with a goal of achieving more effective and less toxic treatments for patients.

Phosphorylated and sumoylation-deficient progesterone receptors drive proliferative gene signatures during breast cancer progression

INTRODUCTION

Progesterone receptors (PR) are emerging as important breast cancer drivers. Phosphorylation events common to breast cancer cells impact PR transcriptional activity, in part by direct phosphorylation. PR-B but not PR-A isoforms are phosphorylated on Ser294 by mitogen activated protein kinase (MAPK) and cyclin dependent kinase 2 (CDK2). Phospho-Ser294 PRs are resistant to ligand-dependent Lys388 SUMOylation (that is, a repressive modification). Antagonism of PR small ubiquitin-like modifier (SUMO)ylation by mitogenic protein kinases suggests a mechanism for derepression (that is, transcriptional activation) of target genes. As a broad range of PR protein expression is observed clinically, a PR gene signature would provide a valuable marker of PR contribution to early breast cancer progression.

METHODS

Global gene expression patterns were measured in T47D and MCF-7 breast cancer cells expressing either wild-type (SUMOylation-capable) or K388R (SUMOylation-deficient) PRs and subjected to pathway analysis. Gene sets were validated by RT-qPCR. Recruitment of coregulators and histone methylation levels were determined by chromatin immunoprecipitation. Changes in cell proliferation and survival were determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays and western blotting. Finally, human breast tumor cohort datasets were probed to identify PR-associated gene signatures; metagene analysis was employed to define survival rates in patients whose tumors express a PR gene signature.

RESULTS

'SUMO-sensitive' PR target genes primarily include genes required for proliferative and pro-survival signaling. DeSUMOylated K388R receptors are preferentially recruited to enhancer regions of derepressed genes (that is, MSX2, RGS2, MAP1A, and PDK4) with the steroid receptor coactivator, CREB-(cAMP-response element-binding protein)-binding protein (CBP), and mixed lineage leukemia 2 (MLL2), a histone methyltransferase mediator of nucleosome remodeling. PR SUMOylation blocks these events, suggesting that SUMO modification of PR prevents interactions with mediators of early chromatin remodeling at 'closed' enhancer regions. SUMO-deficient (phospho-Ser294) PR gene signatures are significantly associated with human epidermal growth factor 2 (ERBB2)-positive luminal breast tumors and predictive of early metastasis and shortened survival. Treatment with antiprogestin or MEK inhibitor abrogated expression of SUMO-sensitive PR target-genes and inhibited proliferation in BT-474 (estrogen receptor (ER)+/PR+/ERBB2+) breast cancer cells.

CONCLUSIONS

We conclude that reversible PR SUMOylation/deSUMOylation profoundly alters target gene selection in breast cancer cells. Phosphorylation-induced PR deSUMOylation favors a permissive chromatin environment via recruitment of CBP and MLL2. Patients whose ER+/PR+ tumors are driven by hyperactive (that is, derepressed) phospho-PRs may benefit from endocrine (antiestrogen) therapies that contain an antiprogestin.

Hormone-responsive 3D multicellular culture model of human breast tissue

A hormone-responsive 3D human tissue-like culture system was developed in which human primary mammary epithelial cells (MECs) were co-cultured with two types of predominant mammary stromal cells on silk protein scaffolds. Silk porous scaffolds with incorporated extracellular matrix provided a compatible environment for epithelial structure morphogenesis and differentiation. The presence of stromal cells promoted MEC proliferation, induced both alveolar and ductal morphogenesis and enhanced casein expression. In contrast, only alveolar structures were observed in monocultures. The alveolar structures generated from the heterotypic cultures in vitro exhibited proper polarity similar to human breast tissue in vivo. Consistent with their phenotypic appearance, more functional differentiation of epithelial cells was also observed in the heterotypic cultures, where casein-α and -β mRNA expression were increased significantly. Additionally, this 3D multicellular culture model displayed an estrogen-responsive physiologically relevant response, evidenced by enhanced cell proliferation, aberrant morphology, changes in gene expression profile and few polarized lumen structures after estrogen treatment. This culture system offers an excellent opportunity to explore the role of cell-cell and cell-substrate interactions during mammary gland development, the consequences of hormone receptor activation on MEC behavior and morphogenesis, as well as their alteration during neoplastic transformation in human breast tissue.