Phosphorylation by p38 mitogen-activated protein kinase promotes estrogen receptor α turnover and functional activity via the SCF(Skp2) proteasomal complex

Beauvericin, produced by Fusarium oxysporum inhibits bisphenol A-induced proliferation of human breast cancer cell line by regulating ERα/p38 pathway

Beauvericin (BEA) is a cyclic depsipeptide secondary metabolite of Fusarium species. It causes chemical hazards in food products and exists in an environment containing soil and various food types. On the other hand, the purified BEA has various biological activities and is regarded as a potential candidate for pharmaceutical research. This study was performed to assess the anti-proliferation activity of BEA against human breast cancer cells by regulating the estrogen receptor-alpha (ERα)/p38 pathway. TA and BA assays verified that BEA is a completed ER antagonist. Additionally, BEA suppressed cell proliferation in the anti-proliferation assay involving ER-positive human breast cancer cells co-treated with BPA and BEA. In respect to an anti-proliferation activity, the BPA-induced phosphorylation of p38 protein was inhibited in the presence of BEA. These results suggested that BEA exerts inhibitory potentials on endocrine disrupting effect and possibly acts as a natural therapeutic material for human estrogen hormonal health.

Dysregulation of deubiquitination in breast cancer

Breast cancer (BC) is a highly frequent malignant tumor that poses a serious threat to women's health and has different molecular subtypes, histological subtypes, and biological features, which act by activating oncogenic factors and suppressing cancer inhibitors. The ubiquitin-proteasome system (UPS) is the main process contributing to protein degradation, and deubiquitinases (DUBs) are reverse enzymes that counteract this process. There is growing evidence that dysregulation of DUBs is involved in the occurrence of BC. Herein, we review recent research findings in BC-associated DUBs, describe their nature, classification, and functions, and discuss the potential mechanisms of DUB-related dysregulation in BC. Furthermore, we present the successful treatment of malignant cancer with DUB inhibitors, as well as analyzing the status of targeting aberrant DUBs in BC.

Environmental estrogens shape disease susceptibility

Along with industrialization, the environment is flooded with endocrine-disrupting chemicals, among which substances with estrogenic effects have attracted widespread attention in medical research. In terms of molecular mechanism, environmental estrogens can cause endocrine and metabolic disorders; interfere with multiple carcinogenic pathways; and lead to neurobehavioral disorders, reproductive toxicity, and multi- or trans-generational phenotypic abnormalities. However, many of the results from molecular and animal experiments were not supported by epidemiology, which may be related to the existence of a window of sensitivity to environmental estrogen exposure over the human life course, where the consequences of exposure vary greatly from other times. This paper will introduce the main sources of environmental estrogens, their toxicity and mechanisms of action, the status of research on several representative types, and current monitoring and treatment methods. We also discussed the extent of the risks to human health dialectically in the context of laboratory and epidemiological findings, with a view to better addressing these chemicals to which we are constantly exposed.

AKTIP loss is enriched in ERα-positive breast cancer for tumorigenesis and confers endocrine resistance

Recurrent deletion of 16q12.2 is observed in luminal breast cancer, yet the causal genomic alterations in this region are largely unknown. In this study, we identify that loss of AKTIP, which is located on 16q12.2, drives tumorigenesis of estrogen receptor alpha (ERα)-positive, but not ERα-negative, breast cancer cells and is associated with poor prognosis of patients with ERα-positive breast cancer. Intriguingly, AKTIP-depleted tumors have increased ERα protein level and activity. Cullin-associated and neddylation-dissociated protein 1 (CAND1), which regulates the cullin-RING E3 ubiquitin ligases, protects ERα from cullin 2-dependent proteasomal degradation. Apart from ERα signaling, AKTIP loss triggers JAK2-STAT3 activation, which provides an alternative survival signal when ERα is inhibited. AKTIP-depleted MCF7 cells and ERα-positive patient-derived organoids are more resistant to ERα antagonists. Importantly, the resistance can be overcome by co-inhibition of JAK2/STAT3. Together, our results highlight the subtype-specific functional consequences of AKTIP loss and provide a mechanistic explanation for the enriched AKTIP copy-number loss in ERα-positive breast cancer.

Diptoindonesin G is a middle domain HSP90 modulator for cancer treatment

HSP90 inhibitors can target many oncoproteins simultaneously, but none have made it through clinical trials due to dose-limiting toxicity and induction of heat shock response, leading to clinical resistance. We identified diptoindonesin G (dip G) as an HSP90 modulator that can promote degradation of HSP90 clients by binding to the middle domain of HSP90 (K_d = 0.13 ± 0.02 μM) without inducing heat shock response. This is likely because dip G does not interfere with the HSP90-HSF1 interaction like N-terminal inhibitors, maintaining HSF1 in a transcriptionally silent state. We found that binding of dip G to HSP90 promotes degradation of HSP90 client protein estrogen receptor α (ER), a major oncogenic driver protein in most breast cancers. Mutations in the ER ligand-binding domain (LBD) are an established mechanism of endocrine resistance and decrease the binding affinity of mainstay endocrine therapies targeting ER, reducing their ability to promote ER degradation or transcriptionally silence ER. Because dip G binds to HSP90 and does not bind to the LBD of ER, unlike endocrine therapies, it is insensitive to ER LBD mutations that drive endocrine resistance. Additionally, we determined that dip G promoted degradation of WT and mutant ER with similar efficacy, downregulated ER- and mutant ER-regulated gene expression, and inhibited WT and mutant cell proliferation. Our data suggest that dip G is not only a molecular probe to study HSP90 biology and the HSP90 conformation cycle, but also a new therapeutic avenue for various cancers, particularly endocrine-resistant breast cancer harboring ER LBD mutations.

[Basic Research on Bullfrog Egg-derived Sialic Acid-binding Lectin for Cancer Treatment]

Sialic acid-binding lectin from Rana catesbeiana (cSBL) is a multifunctional protein with both lectin and ribonuclease activity and is, therefore, called a leczyme. It exerts cancer cell-selective antitumor effects on a variety of cancer cells in vitro and in vivo under conditions where no undesired side effects are observed. cSBL elicits antitumor effects by degrading cellular RNA and subsequently inducing apoptosis via a pathway mediated by mitochondria and endoplasmic reticulum stress. Further, it exerts synergistic antitumor effects with other molecules such as tumor necrosis factor-related apoptosis-inducing ligand and pemetrexed. Recent studies have revealed that long-term treatment of cancer cells with cSBL causes significant pleiotropic changes in the expression profiles of several genes, including multiple genes involved in metabolic pathways. Furthermore, cSBL reduces the expression of some cancer-related molecules such as human epidermal growth factor receptors, aldo-keto reductase 1B10, and ATP-binding cassette transporter C2. The information described above is expected to lead to useful applications, such as effective regimens comprising cSBL and other drugs. These findings reveal favorable properties of cSBL as an anticancer drug, which may contribute to the development of new therapeutic strategies for cancer treatment.

Five-year survival in luminal breast cancer patients: relation with intratumoral activity of proteasomes

Background

The purpose of the study was to analyze the relationship between the caspase-like (CL) and chymotrypsin-like (ChTL) activities of proteasomes and the 5-year overall and metastasis-free survival rates in patients with luminal breast cancer.

Methods

The study included 117 patients with primary operable invasive breast cancer (T1-2N0-1M0). Tissue samples from breast cancer patients were obtained as a result of the radical mastectomy or breast conserving surgery, which was a first line of therapy. The ChTL and CL proteasomes activities in the tumor tissue and in the surrounding adjacent breast tissues were assessed using the fluorometric method. The coefficients of ChTL (cChTL) and CL (cCL) proteasomes activities were also determined. The coefficients were calculated as the ratio of the corresponding proteasomes activity in the tumor tissue to the surrounding adjacent breast tissues. Within 5 years of follow-up, hematogenous metastases occurred in 14% of patients with luminal A breast cancer, in 31% of patients with luminal B human epidermal growth factor receptor-2 (HER-2) negative and in 23% of patients with luminal B HER-2 positive breast cancers. The study protocol was approved by the Local Ethics Committee of the Cancer Research Institute of Tomsk National Research Medical Center. Written informed consent was obtained from all patients.

Results

An increase in the ChTL and CL proteasomes activities was shown in all studied molecular subtypes of breast cancer compared to adjacent tissues. It was found that the cChTL of >35.9 U/mg protein and the cCL of >2.21 in breast cancer patients were associated with the development of distant metastases. In patients with luminal A breast cancer, the 5-year metastasis-free survival rates were associated only with the value of cCL of proteasomes (log-rank test: P=0.008). In patients with luminal B HER-2 negative breast cancer, the 5-year metastasis-free survival rates were associated with the levels of ChTL and cCL proteasomes activities (log-rank test: P=0.02 and P=0.04, respectively).

Conclusions

The data obtained on the correlation of 5-year metastasis-free survival rates with the level of proteasomes activities indicate the possibility of their use as additional prognostic criteria for breast cancer.

Evolution of 3-(4-hydroxyphenyl)indoline-2-one as a scaffold for potent and selective anticancer activity

Development of targeted anticancer modalities has prompted a new era in cancer treatment that is notably different from the age of radical surgery and highly toxic chemotherapy. Behind each effective compound is a rich and complex history from first identification of chemical matter, detailed optimization, and mechanistic investigations, ultimately leading to exciting molecules for drug development. Herein we review the history and on-going journey of one such anticancer scaffold, the 3-(4-hydroxyphenyl)indoline-2-ones. With humble beginnings in 19th century Bavaria, we review this scaffold's synthetic history and anticancer optimization, including its recent demonstration of tumor eradication of drug-resistant, estrogen receptor-positive breast cancer. Compounds containing the 3-(4-hydroxyphenyl)indoline-2-one pharmacophore are emerging as intriguing candidates for the treatment of cancer.

FKBP52 and FKBP51 differentially regulate the stability of estrogen receptor in breast cancer

SignificanceEstrogen receptor α (ERα) is a transcription factor that induces cell proliferation and exhibits increased expression in a large subset of breast cancers. We comprehensively searched for indicators of poor prognosis in ERα-positive breast cancer through the multiple databases, including interactome, transcriptome, and survival analysis, and identified FKBP52. We found that two immunophilins, FKBP52 and FKBP51, have opposing effects on ERα stability and propose that therapeutic targeting of FKBP52 could be useful for the prevention and treatment of ERα-positive breast cancers, including endocrine therapy-resistant breast cancers.

A gene signature consisting of ubiquitin ligases and deubiquitinating enzymes of SKP2 is associated with clinical outcome in breast cancer

The ubiquitination of SKP2, an oncoprotein, is controlled by its E3 ligases, including APC/C^FZR1 and deubiquitinases such as USP10. We identified a two-gene signature for the ubiquitination of SKP2, consisting of the copy number of FZR1 compared to the copy number of USP10. The signature reflects the level of SKP2 activity, stratifying BC patients into two groups with significantly different protein levels of SKP2 ubiquitination substrate p27 (t-test p < 0.01) and recapitulating the expression patterns of SKP2 between tumor and normal tissue (Spearman’s ρ = 0.39.) The signature is also highly associated with clinical outcome in luminal BC but not other subtypes, characterizing patients into two groups with significantly different overall survival times (log-rank p = 0.006). In addition, it is dramatically associated with tumor grade (Chi-squared p = 6.7 × 10⁻³), stage (Chi-squared p = 1.6 × 10⁻¹¹), and the number of positive lymph nodes (negative binomial regression coefficient p = 2.0 × 10⁻³). Our study provides a rationale for targeting the SKP2 ubiquitination pathway in luminal BC and for further investigation of the use of ubiquitinase/deubiquitinase genes as prognosis and treatment biomarkers.

Calcineurin regulates the stability and activity of estrogen receptor α

Estrogen receptor α (ER-α) mediates estrogen-dependent cancer progression and is expressed in most breast cancer cells. However, the molecular mechanisms underlying the regulation of the cellular abundance and activity of ER-α remain unclear. We here show that the protein phosphatase calcineurin regulates both ER-α stability and activity in human breast cancer cells. Calcineurin depletion or inhibition down-regulated the abundance of ER-α by promoting its polyubiquitination and degradation. Calcineurin inhibition also promoted the binding of ER-α to the E3 ubiquitin ligase E6AP, and calcineurin mediated the dephosphorylation of ER-α at Ser²⁹⁴ in vitro. Moreover, the ER-α (S294A) mutant was more stable and activated the expression of ER-α target genes to a greater extent compared with the wild-type protein, whereas the extents of its interaction with E6AP and polyubiquitination were attenuated. These results suggest that the phosphorylation of ER-α at Ser²⁹⁴ promotes its binding to E6AP and consequent degradation. Calcineurin was also found to be required for the phosphorylation of ER-α at Ser¹¹⁸ by mechanistic target of rapamycin complex 1 and the consequent activation of ER-α in response to β-estradiol treatment. Our study thus indicates that calcineurin controls both the stability and activity of ER-α by regulating its phosphorylation at Ser²⁹⁴ and Ser¹¹⁸ Finally, the expression of the calcineurin A-α gene (PPP3CA) was associated with poor prognosis in ER-α-positive breast cancer patients treated with tamoxifen or other endocrine therapeutic agents. Calcineurin is thus a promising target for the development of therapies for ER-α-positive breast cancer.

MINDY1 promotes breast cancer cell proliferation by stabilizing estrogen receptor α

Breast cancer is the most commonly diagnosed malignant tumor among females. Estrogen receptor α (ERα) is initially expressed in 70% of breast cancers and is a well-known target of endocrine therapy for ERα-positive breast cancer. In the present study, we identified MINDY1, a member belongs to the motif interacting with Ubcontaining novel DUB family (MINDY), as a potential deubiquitylase of ERα in breast cancer. There was a positive correlation between ERα and MINDY1 protein levels in human breast cancer tissues. We found that high expression of MINDY1 was associated with poor prognosis. MINDY1 interacted with ERα, thereby mediating the deubiquitination of ERα and increased its stability in a deubiquitylation activity-dependent manner. MINDY1 depletion significantly decreased the ERα protein level and ERα signaling activity in breast cancer cells. Specifically, MINDY1 associated with the N-terminal of ERα via its catalytic domain, thus inhibiting K48-specific poly-ubiquitination process on ERα protein. In addition, MINDY1 depletion led to growth inhibition and cell cycle arrest of ERα-positive breast cancer cells. Finally, overexpression of ERα could rescue the MINDY1 depletion-induced growth inhibition both in vitro and in vivo, suggesting that MINDY1 promotes breast carcinogenesis through increasing ERα stability. Overall, our study proposed a novel post-translational mechanism of ERα in supporting breast cancer progression. Targeting the MINDY1 may prove to be a promising strategy for patients with ERα-positive breast cancer.

OTUD7B stabilizes estrogen receptor α and promotes breast cancer cell proliferation

Breast cancer is the most common malignancy in women worldwide. Estrogen receptor α (ERα) is expressed in ∼70% of breast cancer cases and promotes estrogen-dependent cancer progression. In the present study, we identified OTU domain-containing 7B (OTUD7B), a deubiquitylase belonging to A20 subgroup of ovarian tumor protein superfamily, as a bona fide deubiquitylase of ERα in breast cancer. OTUD7B expression was found to be positively correlated with ERα in breast cancer and associated with poor prognosis. OTUD7B could interact with, deubiquitylate, and stabilize ERα in a deubiquitylation activity-dependent manner. Depletion of OTUD7B decreased ERα protein level, the expression of ERα target genes, and the activity of estrogen response element in breast cancer cells. In addition, OTUD7B depletion significantly decreased ERα-positive breast cancer cell proliferation and migration. Finally, overexpression of ERα could rescue the suppressive effect induced by OTUD7B depletion, suggesting that the ERα status was essential to the function of OTUD7B in breast carcinogenesis. In conclusion, our study revealed an interesting post-translational mechanism between ERα and OTUD7B in ERα-positive breast cancer. Targeting the OTUD7B–ERα complex may prove to be a potential approach to treat patients with ERα-positive breast cancer.

Sex differences in vulnerability to addiction

This article reviews evidence for sex differences in vulnerability to addiction with an emphasis on the neural mechanisms underlying these differences. Sex differences in the way that the gonadal hormone, estradiol, interacts with the ascending telencephalic dopamine system results in sex differences in motivated behaviors, including drug-seeking. In rodents, repeated psychostimulant exposure enhances incentive sensitization to a greater extent in females than males. Estradiol increases females' motivation to attain psychostimulants and enhances the value of drug related cues, which ultimately increases their susceptibility towards spontaneous relapse. This, along with females' dampened ability to alter decisions regarding risky behaviors, enhances their vulnerability for escalation of drug use. In males, recent evidence suggests that estradiol may be protective against susceptibility towards drug-preference. Sex differences in the actions of estradiol are reviewed to provide a foundation for understanding how future research might enhance understanding of the mechanisms of sex differences in addiction-related behaviors, which are dependent on estradiol receptor (ER) subtype and the region of the brain they are acting in. A comprehensive review of the distribution of ERα, ERβ, and GPER1 throughout the rodent brain are provided along with a discussion of the possible ways in which these patterns differentially regulate drug-taking between the sexes. The article concludes with a brief discussion of the actions of gonadal hormones on the circuitry of the stress system, including the hypothalamic pituitary adrenal axis and regulation of corticotropin-releasing factor. Sex differences in the stress system can also contribute to females' enhanced vulnerability towards addiction.

The effect of environmental Bisphenol A exposure on breast cancer associated with obesity

Bisphenol A (BPA) is a widely used endocrine disrupter. Its environmental exposure is a causative factor of cell aging via decreasing telomerase activity, thus leading to shortening of telomere length. Epidemiological studies confirm positive associations between BPA exposure and the incidence of obesity and type 2 diabetes (T2DM). Increased urinary BPA levels in obese females are both significantly correlated with shorter relative telomere length and T2DM. BPA is a critically effective endocrine disrupter leading to poor prognosis via the obesity-inflammation-aromatase axis in breast cancer. Environmental BPA exposure contributes to the progression of both estrogen dependent and triple negative breast cancers. BPA is a positive regulator of human telomerase reverse transcriptase (hTERT) and it increases the expression of hTERT mRNA in breast cancer cells. BPA exposure can lead to tamoxifen resistance. Among patients treated with chemotherapy, those with persistent high telomerase activity due to BPA are at higher risk of death.

TRIM8 inhibits breast cancer proliferation by regulating estrogen signaling

Breast cancer (BC) is the most common female malignancy worldwide, and 70% of which are estrogen receptor α (ERα) positive. Endocrine treatment, such as tamoxifen, is a primary adjuvant therapy for patients with ER-positive BC. However, some patients will develop acquired resistance following long-time treatment. Further research on estrogen signaling is important to improve the therapy of these patients. In this study, we report that the E3 ubiquitin ligase tripartite motif 8 (TRIM8) acts as a novel regulator of ERα signaling. TRIM8 is downregulated in BC and is associated with poor prognosis. In addition, the protein level of TRIM8 is negatively correlated with ERα. RNA sequencing revealed that estrogen signaling maybe a potential target of TRIM8. Moreover, knockdown of TRIM8 can significantly enhance BC cell proliferation and migration both in vitro and in vivo. And this effect can be reversed by ERα depletion. Further mechanistic studies showed that TRIM8 interacts with AF1 domain of ERα via its RING domain in the cytoplasm and increases poly-ubiquitination of the ERα protein. In conclusion, our study reveals an interesting post-translational mechanism between ERα and TRIM8 in ER-positive BC, which suggests that TRIM8 may be a potential therapeutic target in the treatment of BC.

TRIM11 promotes breast cancer cell proliferation by stabilizing estrogen receptor α

Breast cancer is the most commonly diagnosed malignancy in female worldwide, over 70% of which are estrogen receptor α (ERα) positive. ERα has a crucial role in the initiation and progression of breast cancer and is an indicator of endocrine therapy, while endocrine resistance is an urgent problem in ER-positive breast cancer patients. In the present study, we identify a novel E3 ubiquitin ligase TRIM11 function to facilitate ERα signaling. TRIM11 is overexpressed in human breast cancer, and associates with poor prognosis. The protein level of TRIM11 is highly correlated with ERα. RNA-seq results suggest that ERα signaling may be an underlying target of TRIM11. Depletion of TRIM11 in breast cancer cells significantly decreases cell proliferation and migration. And the suppression effects can be reversed by overexpressing ERα. In addition, ERα protein level, ERα target genes expression and estrogen response element activity are also dramatically decreased by TRIM11 depletion. Further mechanistic analysis indicates that the RING domain of TRIM11 interacted with the N terminal of ERα in the cytoplasm and promotes its mono-ubiquitination, thus enhances ERα protein stability. Our study describes TRIM11 as a modulating factor of ERα and increases ERα stability via mono-ubiquitination. TRIM11 could be a promising therapeutic target for breast cancer treatment.

Intrinsic and Extrinsic Factors Governing the Transcriptional Regulation of ESR1

Transcriptional regulation of ESR1, the gene that encodes for estrogen receptor α (ER), is critical for regulating the downstream effects of the estrogen signaling pathway in breast cancer such as cell growth. ESR1 is a large and complex gene that is regulated by multiple regulatory elements, which has complicated our understanding of how ESR1 expression is controlled in the context of breast cancer. Early studies characterized the genomic structure of ESR1 with subsequent studies focused on identifying intrinsic (chromatin environment, transcription factors, signaling pathways) and extrinsic (tumor microenvironment, secreted factors) mechanisms that impact ESR1 gene expression. Currently, the introduction of genomic sequencing platforms and additional genome-wide technologies has provided additional insight on how chromatin structures may coordinate with these intrinsic and extrinsic mechanisms to regulate ESR1 expression. Understanding these interactions will allow us to have a clearer understanding of how ESR1 expression is regulated and eventually provide clues on how to influence its regulation with potential treatments. In this review, we highlight key studies concerning the genomic structure of ESR1, mechanisms that affect the dynamics of ESR1 expression, and considerations towards affecting ESR1 expression and hormone responsiveness in breast cancer.

Estrogen Receptors and Ubiquitin Proteasome System: Mutual Regulation

This review provides information on the structure of estrogen receptors (ERs), their localization and functions in mammalian cells. Additionally, the structure of proteasomes and mechanisms of protein ubiquitination and cleavage are described. According to the modern concept, the ubiquitin proteasome system (UPS) is involved in the regulation of the activity of ERs in several ways. First, UPS performs the ubiquitination of ERs with a change in their functional activity. Second, UPS degrades ERs and their transcriptional regulators. Third, UPS affects the expression of ER genes. In addition, the opportunity of the regulation of proteasome functioning by ERs—in particular, the expression of immune proteasomes—is discussed. Understanding the complex mechanisms underlying the regulation of ERs and proteasomes has great prospects for the development of new therapeutic agents that can make a significant contribution to the treatment of diseases associated with the impaired function of these biomolecules.

Hypoxia differentially regulates estrogen receptor alpha in 2D and 3D culture formats

Hypoxia is a common feature in solid tumors. Clinical samples show a positive correlation between the expression of the hypoxia-inducible factor HIF-1α and estrogen receptor alpha (ERα) and a negative correlation between HIF-1α and hormone sensitivity. Results from monolayer cultures are in contention with clinical observations, showing that ER (+) cell lines no longer express ERα under hypoxic conditions (1% O₂). Here, we compared the impact of hypoxia on the ERα signaling pathway for T47D cells in a 2D and 3D culture format. In the 2D format, the cells were cultured as monolayers. In the 3D format, paper-based scaffolds supported cells suspended in a collagen matrix. Using ELISA, Western blot, and immunofluorescence measurements, we show that hypoxia differentially regulates ERα protein levels in a culture environment-dependent manner. In the 2D format, the protein levels are significantly decreased in hypoxia. In the 3D format, the protein levels are maintained in hypoxia. Hypoxia reduced ERα transcriptional activation in both culture formats. These results highlight the importance of considering tissue dimensionality for in vitro studies. They also show that ERα protein levels in hypoxia are not an accurate indicator of ERα transcriptional activity, and confirm that a positive stain for ERα in a clinical sample may not necessarily indicate hormone sensitivity.

Co-expression of nuclear P38 and hormone receptors is prognostic of good long-term clinical outcome in primary breast cancer and is linked to upregulation of DNA repair

Background

P38 mitogen activated protein kinase is an intermediary signal transduction factor with context-specific roles in breast cancer. Recent mechanistic studies add to the growing consensus that P38 is a tumour suppressor, and it may represent a novel target for breast cancer treatment. The aim of this study is to add definitive data on the prognostic value of P38 and its link with biomarkers in primary breast cancer.

Methods

A large, well-characterised series of 1332 primary breast cancer patients with long-term clinical follow-up was assessed for P38 expression by immunohistochemistry. Association of clinicopathological factors and a panel of breast cancer biomarkers was determined by chi-squared test, and multivariate survival analysis was performed using Cox Proportional Hazards regression modelling.

Results

This study shows that nuclear P38 is co-expressed with nuclear hormone receptors (p < 0.001) and is an independent prognostic marker of good long-term clinical outcome in primary breast cancer (hazard ratio 0.796, 95% confidence interval 0.662–0.957, p = 0.015). Significant association was found between expression of P38 and markers of DNA repair including nuclear BRCA1 and RAD51, and cleaved PARP1 (all p < 0.001).

Conclusions

The findings support the proposed role for P38 as a tumour suppressor in breast cancer via upregulation of DNA repair proteins and provide novel hypothesis-generating information on the potential role of P38 in adjuvant therapy decision making.

Electronic supplementary material

The online version of this article (10.1186/s12885-018-4924-2) contains supplementary material, which is available to authorized users.

Sialic Acid-Binding Lectin from Bullfrog Eggs Exhibits an Anti-Tumor Effect Against Breast Cancer Cells Including Triple-Negative Phenotype Cells

Sialic acid-binding lectin from Rana catesbeiana eggs (cSBL) is a multifunctional protein that has lectin and ribonuclease activity. In this study, the anti-tumor activities of cSBL were assessed using a panel of breast cancer cell lines. cSBL suppressed the cell growth of all cancer cell lines tested here at a concentration that is less toxic, or not toxic at all, to normal cells. The growth suppressive effect was attributed to the cancer-selective induction of apoptosis. We assessed the expressions of several key molecules associated with the breast cancer phenotype after cSBL treatment by western blotting. cSBL decreased the expression level of estrogen receptor (ER) α, while it increased the phosphorylation level of p38 mitogen-activated protein kinase (MAPK). cSBL also suppressed the expression of the progesterone receptor (PgR) and human epidermal growth factor receptor type 2 (HER2). Furthermore, it was revealed that cSBL decreases the expression of the epidermal growth factor receptor (EGFR/HER1) in triple-negative breast cancer cells. These results indicate that cSBL induces apoptosis with decreasing ErbB family proteins and may have great potential for breast cancer chemotherapy, particularly in triple-negative phenotype cells.

Polyubiquitination inhibition of estrogen receptor alpha and its implications in breast cancer

Estrogen receptor alpha (ERα) is detected in more than 70% of the cases of breast cancer. Nuclear activity of ERα, a transcriptional regulator, is linked to the development of mammary tumors, whereas the extranuclear activity of ERα is related to endocrine therapy resistance. ERα polyubiquitination is induced by the estradiol hormone, and also by selective estrogen receptor degraders, resulting in ERα degradation via the ubiquitin proteasome system. Moreover, polyubiquitination is related to the ERα transcription cycle, and some E3-ubiquitin ligases also function as coactivators for ERα. Several studies have demonstrated that ERα polyubiquitination is inhibited by multiple mechanisms that include posttranslational modifications, interactions with coregulators, and formation of specific protein complexes with ERα. These events are responsible for an increase in ERα protein levels and deregulation of its signaling in breast cancers. Thus, ERα polyubiquitination inhibition may be a key factor in the progression of breast cancer and resistance to endocrine therapy.

Gender Bias in Human Systemic Lupus Erythematosus: A Problem of Steroid Receptor Action?

Systemic lupus erythematosus (SLE) is a chronic systemic autoimmune disease resulting from abnormal interactions between T and B cells. The acquisition of SLE is linked to genetic susceptibility, and diverse environmental agents can trigger disease onset in genetically susceptible individuals. However, the strongest risk factor for developing SLE is being female (9:1 female to male ratio). The female sex steroid, estradiol, working through its receptors, contributes to the gender bias in SLE although the mechanisms remain enigmatic. In a small clinical trial, monthly administration of the estrogen receptor (ERα) antagonist, ICI182,780 (fulvestrant), significantly reduced disease indicators in SLE patients. In order to identify changes that could account for improved disease status, the present study utilized fulvestrant (Faslodex) to block ERα action in cultured SLE T cells that were purified from blood samples collected from SLE patients (n = 18, median age 42 years) and healthy control females (n = 25, median age 46 years). The effects of ERα antagonism on estradiol-dependent gene expression and canonical signaling pathways were analyzed. Pathways that were significantly altered by addition of Faslodex included T helper (Th) cell differentiation, steroid receptor signaling [glucocorticoid receptor (GR), ESR1 (ERα)], ubiquitination, and sumoylation pathways. ERα protein expression was significantly lower (p < 0.018) in freshly isolated, resting SLE T cells suggesting ERα turnover is inherently faster in SLE T cells. In contrast, ERα/ERβ mRNA and ERβ protein levels were not significantly different between SLE and normal control T cell samples. Plasma estradiol levels did not differ (p > 0.05) between SLE patients and controls. A previously undetected interaction between GR and ERα signaling pathways suggests posttranslational modification of steroid receptors in SLE T cells may alter ERα/GR actions and contribute to the strong gender bias of this autoimmune disorder.

Inhibition of estrogen receptor reduces connexin 43 expression in breast cancers

Connexins are widely supported as tumor suppressors due to their downregulation in cancers, nevertheless, more recent evidence suggests roles for connexins in facilitating tumor progression in later stages, including metastasis. One of the key factors regulating the expression, modification, stability, and localization of connexins is hormone receptors in hormone-dependent cancers. It is reasonable to consider that hormones/hormone receptors may modulate connexins expression and play critical roles in the cellular control of connexins during breast cancer progression. In estrogen receptor (ER)-positive breast cancers, tamoxifen and fulvestrant are widely used therapeutic agents and are considered to alter ER signaling. In this present study, we investigated the effects of fulvestrant and tamoxifen in Cx43 expression, and we also explored the role of Cx43 in ER-positive breast cancer migration and the relationship between Cx43 and ER. The involvement of estrogen/ER in Cx43 modulation was further verified by administering tyrosine kinase inhibitors and chemotherapeutic agents. We found that inhibition of ER promoted the binding of E3 ligase Nedd4 to Cx43, leading to Cx43 ubiquitination. Furthermore, inhibition of ER by fulvestrant and tamoxifen phosphorylated p38 MAPK, and inhibition of Rac, MKK3/6, and p38 reversed fulvestrant-reduced Cx43 expression. These findings suggest that Cx43 expression which may positively regulate cell migration is ER-dependent in ER-positive breast cancer cells.

Cdk5 Directly Targets Nuclear p21CIP1 and Promotes Cancer Cell Growth

The significance of Cdk5 in cell-cycle control and cancer biology has gained increased attention. Here we report the inverse correlation between the protein levels of Cdk5 and p21^CIP1 from cell-based and clinical analysis. Mechanistically, we identify that Cdk5 overexpression triggers the proteasome-dependent degradation of p21^CIP1 through a S130 phosphorylation in a Cdk2-independent manner. Besides, the evidence from cell-based and clinical analysis shows that Cdk5 primarily regulates nuclear p21^CIP1 protein degradation. S130A-p21^CIP1 mutant enables to block either its protein degradation or the increase of cancer cell growth caused by Cdk5. Notably, Cdk5-triggered p21^CIP1 targeting primarily appears in S-phase, while Cdk5 overexpression increases the activation of Cdk2 and its interaction with DNA polymerase δ. The in vivo results show that Cdk2 might play an important role in the downstream signaling to Cdk5. In summary, these findings suggest that Cdk5 in a high expression status promotes cancer growth by directly and rapidly releasing p21^CIP1-dependent cell-cycle inhibition and subsequent Cdk2 activation, which illustrates an oncogenic role of Cdk5 potentially applied for future diagnosis and therapy. Cancer Res; 76(23); 6888-900. ©2016 AACR.

Estradiol postconditioning relieves ischemia/reperfusion injury in axial skin flaps of rats, inhibits apoptosis and alters the MKP-1/ERK pathway

Previous studies have suggested that estradiol can reduce the ischemia/reperfusion (I/R) injury in skin flaps. However, the mechanism, particularly the signal pathways involved in this protective effect are not well established. In the current study, an I/R injury model was established in rats to explore the connection between estradiol protection during I/R injury and extracellular signal‑regulated kinase (ERK) signaling. Healthy male Wistar rats were divided into five groups (n=10): Control group (group I), I/R group (group II), saline group (group III), estradiol group (group IV) and inhibitor (PD‑98059) group (group V). The survival rate of the flap was compared between groups, morphological changes were observed by hematoxylin and eosin staining of sections, and terminal deoxynucleotidyl transferase dUTP nick end labeling was performed to identify apoptotic cells and determine the apoptotic index. To further investigate the mechanism, western blot analysis was performed to assess the protein level of ERK1/2, phospho‑ERK1/2, and mitogen‑activated protein kinase phosphatase 1 (MKP‑1). The results of the present study demonstrated that estradiol therapy can reduce I/R injury and decrease the apoptosis index in an axial skin flap model. The inhibitor of the ERK pathway (PD‑98059) partially abolished the effects of estradiol, which involve the phosphatase enzyme MKP‑1. Taken together, the findings of the present study indicate that estradiol may act by reducing the expression of MKP‑1, mediating the expression/activation changes of the ERK pathway and subsequently reduce the level of apoptosis and the I/R injury the axial flap. Estrogen may be used to mitigate the adverse reaction caused by ischemia‑reperfusion injury and effectively improve the survival rate and survival quality of free skin flap and improve patient prognosis.

Correlation between genetic polymorphisms within the MAPK1/HIF-1/HO-1 signaling pathway and risk or prognosis of perimenopausal coronary artery disease

BACKGROUND

Mitogen-activated protein kinase-1 (MAPK1), as well as its downstream factors of hypoxia-inducible factor-1 (HIF-1) and heme oxygenase-1 (HO-1), have been documented to be involved in modulating development of coronary artery disease (CAD).

HYPOTHESIS

Genetic mutations within the MAPK1/HIF-1/HO-1 signaling pathway could alter the risk of perimenopausal CAD in Chinese patients.

METHODS

Peripheral blood samples were gathered from 589 CAD patients and 860 healthy controls, and 12 potential single-nucleotide polymorphisms (SNPs) were obtained from HapMap database and previously published studies. Genotyping of SNPs was implemented with the TaqMan SNP Genotyping Assays. Odds ratios (OR) and 95% confidence intervals (CI) were utilized to evaluate the correlations between SNPs and CAD risk.

RESULTS

Regarding MAPK1 , rs6928 (OR: 1.71, 95% CI: 1.47-1.98, P < 0.05), rs9340 (OR: 0.85, 95% CI: 0.73-0.99, P < 0.05), and rs11913721 (OR: 0.70, 95% CI: 0.52-0.95, P < 0.05) were remarkably associated with susceptibility to perimenopausal CAD. Of these, rs9340 and rs11913721 were also regarded as protective factors for perimenopausal CAD patients. Moreover, results of HIF-1 indicated noticeable correlations between combined SNPs of rs1087314 and rs2057482 and risk of perimenopausal CAD (OR: 1.24, 95% CI: 1.01-1.53, P < 0.05; and OR: 0.71, 95% CI: 0.55-0.91, P < 0.05, respectively). Nonetheless, rs2071746 in HO-1 was found to be only associated with perimenopausal CAD risk (OR: 0.67, 95% CI: 0.58-0.78, P < 0.05).

CONCLUSIONS

The genetic mutations within MAPK1 (rs6928, rs9340, rs11913721), HIF-1 (rs1087314, rs2057482), and HO-1 (rs2071746) could alter susceptibility to perimenopausal CAD in this Chinese population.

Full antagonism of the estrogen receptor without a prototypical ligand side chain

Resistance to endocrine therapies remains a major clinical problem for the treatment of estrogen receptor-α (ERα)-positive breast cancer. On-target side effects limit therapeutic compliance and use for chemoprevention, highlighting an unmet need for new therapies. Here we present a full-antagonist ligand series lacking the prototypical ligand side chain that has been universally used to engender antagonism of ERα through poorly understood structural mechanisms. A series of crystal structures and phenotypic assays reveal a structure-based design strategy with separate design elements for antagonism and degradation of the receptor, and access to a structurally distinct space for further improvements in ligand design. Understanding structural rules that guide ligands to produce diverse ERα-mediated phenotypes has broad implications for the treatment of breast cancer and other estrogen-sensitive aspects of human health including bone homeostasis, energy metabolism, and autoimmunity.

Nuclear receptors outside the nucleus: extranuclear signalling by steroid receptors

Steroid hormone receptors mediate numerous crucial biological processes and are classically thought to function as transcriptional regulators in the nucleus. However, it has been known for more than 50 years that steroids evoke rapid responses in many organs that cannot be explained by gene regulation. Mounting evidence indicates that most steroid receptors in fact exist in extranuclear cellular pools, including at the plasma membrane. This latter pool, when engaged by a steroid ligand, rapidly activates signals that affect various aspects of cellular biology. Research into the mechanisms of signalling instigated by extranuclear steroid receptor pools and how this extranuclear signalling is integrated with responses elicited by nuclear receptor pools provides novel understanding of steroid hormone signalling and its roles in health and disease.

Oestrogen receptor negativity in breast cancer: a cause or consequence?

Endocrine resistance, which occurs either by de novo or acquired route, is posing a major challenge in treating hormone-dependent breast cancers by endocrine therapies. The loss of oestrogen receptor α (ERα) expression is the vital cause of establishing endocrine resistance in this subtype. Understanding the mechanisms that determine the causes of this phenomenon are therefore essential to reduce the disease efficacy. But how we negate oestrogen receptor (ER) negativity and endocrine resistance in breast cancer is questionable. To answer that, two important approaches are considered: (1) understanding the cellular origin of heterogeneity and ER negativity in breast cancers and (2) characterization of molecular regulators of endocrine resistance. Breast tumours are heterogeneous in nature, having distinct molecular, cellular, histological and clinical behaviour. Recent advancements in perception of the heterogeneity of breast cancer revealed that the origin of a particular mammary tumour phenotype depends on the interactions between the cell of origin and driver genetic hits. On the other hand, histone deacetylases (HDACs), DNA methyltransferases (DNMTs), miRNAs and ubiquitin ligases emerged as vital molecular regulators of ER negativity in breast cancers. Restoring response to endocrine therapy through re-expression of ERα by modulating the expression of these molecular regulators is therefore considered as a relevant concept that can be implemented in treating ER-negative breast cancers. In this review, we will thoroughly discuss the underlying mechanisms for the loss of ERα expression and provide the future prospects for implementing the strategies to negate ER negativity in breast cancers.

Role of the p38 mitogen-activated protein kinase signaling pathway in estrogen-mediated protection following flap ischemia-reperfusion injury

Ischemia-reperfusion (I/R) injury often occurs during skin flap transplantation and results in tissue damage. Although estrogen treatment significantly alleviates this I/R injury-induced damage, the detailed molecular mechanism is not clear. In this study, a superficial epigastric artery flap I/R injury model was created in adult Wistar rats. Severe necrosis was observed in skin tissue after I/R injury. Histological examination of skin tissue revealed that I/R injury damages skin structure and results in neutrophil infiltration. Inflammation-related parameters, including neutrophil count, tumor necrosis factor-α, and interleukin-10 levels, were increased due to I/R injury. These pathological phenomena were reduced by estradiol treatment. Further investigation found that I/R injury triggers the p38 mitogen-activated protein kinase (p38-MAPK) pathway. The expression levels of p38-MAPK and phosphorylated p38-MAPK were increased after I/R injury. Estradiol increased the expression level of MAPK phosphatase-2, a putative phosphatase of p38, and reduced the levels of p38-MAPK and phosphorylated p38-MAPK. These results suggest that estradiol can improve skin flap survival, possibly by inhibiting neutrophil infiltration and the expression of p38-MAPK. This study provides an explanation for how estrogen alleviates I/R injury-induced damage that occurs during skin flap transplantation. In a rat pathological model, I/R injury leads to skin necrosis, skin structure damage, neutrophil infiltration, and inflammatory cytokine secretion, which are probably downstream effects of activation of the p38-MAPK pathway. On the other hand, estradiol treatment triggers the expression of MAPK phosphatase-2, a putative phosphatase of p38-MAPK, and reduced all examined pathological phenomena. Therefore, estrogen may reduce the deleterious effect of I/R injury on skin flap transplantation through modulating the p38-MAPK pathway.

ERpS294 is a biomarker of ligand or mutational ERα activation and a breast cancer target for CDK2 inhibition

ERα phosphorylation at hinge site S294 (pS294) was recently shown to be essential for ER-dependent gene transcription and mediated by an unknown cyclin-dependent kinase (CDK). This study was undertaken to identify the exact CDK pathway mediating pS294 formation, and to determine if this phosphorylation event occurs with, and can be targeted to treat, the ligand-independent growth of breast cancers expressing endocrine-refractory ESR1 mutations. Using a newly developed anti-pS294 monoclonal antibody, a combination of CDK specific siRNA knockdown studies and a broad panel of CDK selective inhibitors against ligand (E2)-stimulated MCF7 cells, we first identified CDK2 as the primary mediator of pS294 formation and showed that CDK2-selective inhibitors like Dinaciclib, but not CDK4/6 inhibitors like Palbociclib, can selectively prevent pS294 formation and repress ER-dependent gene expression. We then expressed the ER-activating mutations ERmut(Y537S) and ERmut(D538G) in MCF7 cells, and demonstrated their ability to induce ligand-independent and tamoxifen-resistant growth, associated with constitutive and CDK2-dependent pS294 expression. Following robust growth of E2-independent and TAM-resistant MCF7mutER(Y537S) tumors in vivo, nude mice were also treated with either Dinaciclib or Palbociclib at doses and injection schedules unable to retard tumor growth as single agents; the TAM plus Palbociclib combination arrested further tumor growth without affecting pS294 formation, while the TAM plus Dinaciclib combination produced tumor regression associated with loss of pS294 expression. These findings, and our proposed mechanistic model, provide new rationale for the clinical evaluation of CDK2 inhibitors given in combination with endocrine agents as a new treatment strategy against ESR1 mutation expressing breast cancers.

Mechanisms that Increase Stability of Estrogen Receptor Alpha in Breast Cancer

Estrogen receptor alpha (ER) is a transcriptional regulator that controls the expression of genes related to cellular proliferation and differentiation in normal mammary tissue. However, the expression, abundance, and activity of this receptor are increased in 70% of breast cancers. The ER upregulation is facilitated by several molecular mechanisms, including protein stability, which represents an important strategy to maintain an active and functional repertoire of ER. Several proteins interact and protect ER from degradation by the ubiquitin-proteasome system. Through diverse mechanisms, these proteins prevent polyubiquitination and degradation of ER, leading to an increase in ER protein levels; consequently, estrogen signaling and its physiologic effects are enhanced in breast cancer cells. Thus, increased protein stability seems to be one of the main reasons that ER is upregulated in breast cancer. Here, we highlight findings on the proteins and mechanisms that participate directly or indirectly in ER stability and their relevance to breast cancer.

In touch with your feminine side: how oestrogen metabolism impacts prostate cancer

Prostate cancer is the primary cancer in males, with increasing global incidence rates making this malignancy a significant healthcare burden. Androgens not only promote normal prostate maturity but also influence the development and progression of prostate cancer. Intriguingly, evidence now suggests endogenous and exogenous oestrogens, in the form of phytoestrogens, may be equally as relevant as androgens in prostate cancer growth. The prostate gland has the molecular mechanisms, catalysed by steroid sulphatase (STS), to unconjugate and utilise circulating oestrogens. Furthermore, prostate tissue also expresses enzymes essential for local oestrogen metabolism, including aromatase (CYP19A1) and 3β- and 17β-hydroxysteroid dehydrogenases. Increased expression of these enzymes in malignant prostate tissue compared with normal prostate indicates that oestrogen synthesis is favoured in malignancy and thus may influence tumour progression. In contrast to previous reviews, here we comprehensively explore the epidemiological and scientific evidence on how oestrogens impact prostate cancer, particularly focusing on pre-receptor oestrogen metabolism and subsequent molecular action. We analyse how molecular mechanisms and metabolic pathways involved in androgen and oestrogen synthesis intertwine to alter prostate tissue. Furthermore, we speculate on whether oestrogen receptor status in the prostate affects progression of this malignancy.

OCT-4: a novel estrogen receptor-α collaborator that promotes tamoxifen resistance in breast cancer cells

Tamoxifen has shown great success in the treatment of breast cancer; however, long-term treatment can lead to acquired tamoxifen (TOT) resistance and relapse. TOT classically antagonizes estradiol (E2) -dependent breast cancer cell growth, but exerts partial agonist/antagonist behavior on gene expression. Although both E2 and TOT treatment of breast cancer cells results in recruitment of the estrogen receptor (ER) to common and distinct genomic sites, the mechanisms and proteins underlying TOT preferential recruitment of the ER remains poorly defined. To this end, we performed in silico motif-enrichment analyses within the ER-binding peaks in response to E2 or TOT, to identify factors that would specifically recruit ER to genomic binding sites in the presence of TOT as compared to E2. Intriguingly, we found Nkx3-1 and Oct-transcription factor homodimer motifs to be enriched in TOT preferential binding sites and confirmed the critical role of Oct-3/4 (aka Oct-4) in directing ER recruitment to TOT preferential genomic binding sites, by chromatin immunoprecipitation (ChIP) analyses. Further investigation revealed Oct-4 expression to be basally repressed by Nkx3-1 in MCF-7 cells and TOT treatment appeared to elevate Nkx3-1 degradation through a p38MAPK-dependent phosphorylation of the E3 ligase, Skp2 at serine-64 residue, as observed by quantitative mass-spectrometry analyses. Consistently, Oct-4 upon induction by phospho-Ser64-Skp2-mediated proteasomal degradation of Nkx3-1, participated in ER transcriptional complexes along with p38MAPK and Skp2 in a tamoxifen-dependent manner leading to TOT-dependent gene activation and cell proliferation of the TOT-resistant MCF-7-tam^r breast cancer cells. Notably, Oct-4 levels were highly elevated in MCF-7-tam^r cells, and appeared critical for their TOT sensitivity in cell proliferation assays. Furthermore, overexpression of Oct-4 enhanced tumor growth in the presence of tamoxifen in mice in vivo. Collectively, our work presents a novel mechanism for tamoxifen-specific gene activation by ER, secondary to its TOT preferential recruitment to genomic sites by specific activation of Oct-4, a phenomenon that appears to underlie tamoxifen resistance in breast cancer cells and in xenograft tumor models, and could be useful in designing therapeutic interventions to improve treatment outcome.

Antiproliferative and apoptosis induction of α-mangostin in T47D breast cancer cells

α-Mangostin extracted from mangosteen, Garcinia mangostana Linn. is known as 'queen of fruits'. The anticancer activity of α-mangostin through apoptosis induction and related signaling pathways in human breast cancer T47D cells was investigated. Human epidermal growth factor receptor 2 (HER2) and mitogen-activated protein kinase (MAPK) signaling have been shown to play important roles in apoptosis. The results showed that α-mangostin induced cell proliferation inhibition, DNA fragmentation, nuclear condensation, increased cleaved caspase-3 and cleaved caspase-9, but decreased Bcl-2 and Mcl-1 expression. Mitochondrial dysfunction and cytochrome c release were also detected. In addition, phosphorylation of ERα, HER2, PI3K, Akt and ERK1/2 were downregulated whereas p-JNK1/2 and p-p38 were upregulated. These results indicated that α-mangostin induced apoptosis associated with HER2/PI3K/Akt and MAPK signaling pathways suggesting that α-mangostin may be used as food supplement or a potential therapeutic compound for breast cancer.

Effects of Activating Mutations on EGFR Cellular Protein Turnover and Amino Acid Recycling Determined Using SILAC Mass Spectrometry

Rapid mutations of proteins that are targeted in cancer therapy often lead to drug resistance. Often, the mutation directly affects a drug's binding site, effectively blocking binding of the drug, but these mutations can have other effects such as changing the protein turnover half-life. Utilizing SILAC MS, we measured the cellular turnover rates of an important non-small cell lung cancer target, epidermal growth factor receptor (EGFR). Wild-type (WT) EGFR, EGFR with a single activating mutant (Del 746–750 or L858R), and the drug-resistant double mutant (L858R/T790M) EGFR were analyzed. In non-small cell lung cancer cell lines, EGFR turnover rates ranged from 28 hours in A431 cells (WT) to 7.5 hours in the PC-9 cells (Del 746–750 mutant). The measurement of EGFR turnover rate in PC-9 cells dosed with irreversible inhibitors has additional complexity due to inhibitor effects on cell viability and results were reported as a range. Finally, essential amino acid recycling (K and R) was measured in different cell lines. The recycling was different in each cell line, but the overall inclusion of the effect of amino acid recycling on calculating EGFR turnover rates resulted in a 10–20% reduction in rates.

Using gene expression signatures to identify novel treatment strategies in gulf war illness

Background

Gulf War Illness (GWI) is a complex multi-symptom disorder that affects up to one in three veterans of this 1991 conflict and for which no effective treatment has been found. Discovering novel treatment strategies for such a complex chronic illness is extremely expensive, carries a high probability of failure and a lengthy cycle time. Repurposing Food and Drug Administration approved drugs offers a cost-effective solution with a significantly abbreviated timeline.

Methods

Here, we explore drug re-purposing opportunities in GWI by combining systems biology and bioinformatics techniques with pharmacogenomic information to find overlapping elements in gene expression linking GWI to successfully treated diseases. Gene modules were defined based on cellular function and their activation estimated from the differential expression of each module’s constituent genes. These gene modules were then cross-referenced with drug atlas and pharmacogenomic databases to identify agents currently used successfully for treatment in other diseases. To explore the clinical use of these drugs in illnesses similar to GWI we compared gene expression patterns in modules that were significantly expressed in GWI with expression patterns in those same modules in other illnesses.

Results

We found 19 functional modules with significantly altered gene expression patterns in GWI. Within these modules, 45 genes were documented drug targets. Illnesses with highly correlated gene expression patterns overlapping considerably with GWI were found in 18 of the disease conditions studied. Brain, muscular and autoimmune disorders composed the bulk of these.

Conclusion

Of the associated drugs, immunosuppressants currently used in treating rheumatoid arthritis, and hormone based therapies were identified as the best available candidates for treating GWI symptoms.

Electronic supplementary material

The online version of this article (doi:10.1186/s12920-015-0111-3) contains supplementary material, which is available to authorized users.

Ubiquitylation of nuclear receptors: new linkages and therapeutic implications

The nuclear receptor (NR) superfamily is a group of transcriptional regulators that control multiple aspects of both physiology and pathology and are broadly recognized as viable therapeutic targets. While receptor-modulating drugs have been successful in many cases, the discovery of new drug targets is still an active area of research, because resistance to NR-targeting therapies remains a significant clinical challenge. Many successful targeted therapies have harnessed the control of receptor activity by targeting events within the NR signaling pathway. In this review, we explore the role of NR ubiquitylation and discuss how the expanding roles of ubiquitin could be leveraged to identify additional entry points to control receptor function for future therapeutic development.

Systems level-based RNAi screening by high content analysis identifies UBR5 as a regulator of estrogen receptor-α protein levels and activity

Estrogen receptor-α (ERα) is a central transcription factor that regulates mammary gland physiology and a key driver in breast cancer. In the present study, we aimed to identify novel modulators of ERα-mediated transcriptional regulation via a custom-built siRNA library screen. This screen was directed against a variety of coregulators, transcription modifiers, signaling molecules and DNA damage response proteins. By utilizing a microscopy-based, multi-end point, estrogen responsive biosensor cell line platform, the primary screen identified a wide range of factors that altered ERα protein levels, chromatin remodeling and mRNA output. We then focused on UBR5, a ubiquitin ligase and known oncogene that modulates ERα protein levels and transcriptional output. Finally, we demonstrated that UBR5 also affects endogenous ERα target genes and E2-mediated cell proliferation in breast cancer cells. In conclusion, our multi-end point RNAi screen identified novel modulators of ERα levels and activity, and provided a robust systems level view of factors involved in mechanisms of nuclear receptor action and pathophysiology. Utilizing a high throughput RNAi screening approach we identified UBR5, a protein commonly amplified in breast cancer, as a novel regulator of ERα protein levels and transcriptional activity.

Bisphenol A exerts estrogenic effects by modulating CDK1/2 and p38 MAP kinase activity

Bisphenol A (BPA) is considered to be an endocrine disruptor, but the mechanisms by which it disrupts endocrine functions are poorly understood. Here, we have shown that BPA binds both estrogen receptor (ER)-α and ER-beta (ER-β) using a fluorescence polarization competitive binding assay. In addition, we found that BPA induced cell proliferation by modulating cell cycle-related genes in the MCF-7 human mammary cancer cell line. Moreover, using a BG1 luciferase ER transactivation assay, we found that BPA has estrogenic activity. Modulating the MAPK pathway by using an ERK inhibitor (PD98059) or a JNK inhibitor (SP600125) had no effect on the ability of BPA to induce estrogenic activity. However, the antiestrogen, ICI 182,780, and the p38 inhibitor, PD 169316 successfully blocked BPA-induced estrogenic activity. Our findings suggest that BPA mimics ER-dependent estrogenic activity by targeting proteins that regulate the cell cycle and p38 MAPK.

Extranuclear estrogen receptor's roles in physiology: lessons from mouse models

Steroid receptors exist and function in multiple compartments of cells in most organs. Although the functions and nature of some of these receptors is being defined, important aspects of receptor localization and signaling to physiology and pathophysiology have been identified. In particular, extranuclear sex steroid receptors have been found in many normal cells and in epithelial tumors, where they enact signal transduction that impacts both nongenomic and genomic functions. Here, I focus on the progress made in understanding the roles of extranuclear estrogen receptors (ER) in physiology and pathophysiology. Extranuclear ER serve as a model to selectively intervene with novel receptor reagents to prevent or limit disease progression. Recent novel mouse models and membrane ER-selective agonists also provide a better understanding of receptor pool cross-talk that results in the overall integrative actions of sex steroids.

Regulation of Androgen Receptor by E3 Ubiquitin Ligases: for More or Less

Prostate cancer (PCa) primarily depends on the dysregulations of androgen receptor (AR) signaling pathway for the initiation and growth as well as recurrence after chemotherapy ^[1]. Androgen deprivation therapy (ADT) effectively alleviates symptoms of the malignancy to arrest further growth of primary tumors or progression of metastasis in patients with advanced PCa. However, relapse occurs in many patients after a short period, and PCa cells eventually become insensitive to ADT - termed castration resistant prostate cancer (CRPC) ^{[2, 3]}. Tremendous advancements have been achieved to decipher the mechanisms on AR signaling, and the ubiquitination machinery contributes to PCa directly or indirectly by either promotion of AR transcriptional activity or degradation of AR protein levels. The recent report reveals that SKP2 regulates AR protein through ubiquitin-mediated proteasomal degradation, highlighting the role of SKP2 in AR signaling. Given the pivotal roles of AKT and SKP2 in cancers, the differential mechanisms of AR ubiquitination by various E3 ligases hold valuable significance and beneficial implications for PCa control.

Xenoestrogens alter estrogen receptor (ER) α intracellular levels

17β-estradiol (E2)-dependent estrogen receptor (ER) α intracellular concentration is a well recognized critical step in the pleiotropic effects elicited by E2 in several target tissues. Beside E2, a class of synthetic and plant-derived chemicals collectively named endocrine disruptors (EDs) or xenoestrogens bind to and modify both nuclear and extra-nuclear ERα activities. However, at the present no information is available on the ability of EDs to hamper ERα intracellular concentration. Here, the effects of bisphenol A (BPA) and naringenin (Nar), prototypes of synthetic and plant-derived ERα ligands, have been evaluated on ERα levels in MCF-7 cells. Both EDs mimic E2 in triggering ERα Ser118 phosphorylation and gene transcription. However, only E2 or BPA induce an increase of cell proliferation; whereas 24 hrs after Nar stimulation a dose-dependent decrease in cell number is reported. E2 or BPA treatment reduces ERα protein and mRNA levels after 24 hrs. Contrarily, Nar stimulation does not alter ERα content but reduces ERα mRNA levels like other ligands. Co-stimulation experiments indicate that 48 hrs of Nar treatment prevents the E2-induced ERα degradation and hijacks the physiological ability of E2:ERα complex to regulate gene transcription. Mechanistically, Nar induces ERα protein accumulation by preventing proteasomal receptor degradation via persistent activation of p38/MAPK pathway. As a whole these data demonstrate that ERα intracellular concentration is an important target through which EDs hamper the hormonal milieu of E2 target cells driving cells to different outcomes or mimicking E2 even in the absence of the hormone.

Links between oestrogen receptor activation and proteolysis: relevance to hormone-regulated cancer therapy

Oestrogen receptor-α (ERα) is a master transcription factor that regulates cell proliferation and homeostasis in many tissues. Despite beneficial ERα functions, sustained oestrogenic exposure increases the risk and/or the progression of various cancers, including those of the breast, endometrium and ovary. Oestrogen–ERα interaction can trigger post-translational ERα modifications through crosstalk with signalling pathways to promote transcriptional activation and ubiquitin-mediated ERα proteolysis, with co-activators that have dual roles as ubiquitin ligases. These processes are reviewed herein. The elucidation of mechanisms whereby oestrogen drives both ERα transactivation and receptor proteolysis might have important therapeutic implications not only for breast cancer but also potentially for other hormone-regulated cancers.

Phosphorylation: a fundamental regulator of steroid receptor action

Steroid hormone receptors (SHRs) are hormone-activated transcription factors involved in numerous cellular functions and in health and disease. Their activities depend on the cellular level of the receptor, the presence of coregulator proteins, and the cell signaling pathways that are active in the cell. SHRs and their coregulators are phosphorylated on multiple sites by a wide variety of kinases. Each site may contribute to multiple functions and the net effect of an individual phosphorylation depends on the activating kinase. Here we discuss functions of known SHR phosphorylation sites, kinase regulation, evidence of translational relevance, and crosstalk between SHRs and cell signaling pathways. Understanding how cell signaling pathways regulate SHRs might yield novel therapeutic targets for multiple human diseases.

Expression and activation of P38 MAP kinase in invasive ductal breast cancers: correlation with expression of the estrogen receptor, HER2 and downstream signaling phosphorylated proteins

MAP kinase signaling proteins have major implications in the molecular oncogenesis of breast cancers and have been extensively investigated as putative targets for therapy. This study reports the investigation of the expression of P38 MAPK and its phosphorylated form (p-P38 MAPK) in clinical specimens of invasive breast carcinomas and their correlation with estrogen receptor (ER) and HER2 expression, as well as MAPK and PI3 kinase-AKT pathway signaling phosphorylated proteins. Expression levels of P38 MAPK and p-P38 MAPK as well as p-AKT, p-GSK3β, p-S6 kinase, p-MEK1 and p-ERK1/2 were quantitatively assessed using multiplex bead immunoassay in frozen specimens from 45 invasive ductal breast cancers. Twenty-nine specimens were ER+, 15 were HER2+ and 10 were triple‑negative breast cancers (TNBCs). P38 MAPK was found to be expressed in all tumor specimens and was significantly (P=0.002) overexpressed in ER+ tumors. P38 MAPK expression was lower in TNBCs than in all of the other tumors. The median expression of p-P38 MAPK was also higher in ER+ tumors while lower in the TNBCs. HER2 status had no effect on P38 MAPK and p-P38 MAPK expression. No variation in the phosphorylation rate of P38 MAPK was observed in relation with ER, HER2 or TNBC status. Significantly higher (P=0.0048) expression of p-AKT was observed in HER2+ tumors. No significant difference in p-MEK1, p-GSK3β and p-S6K expression was found in any other comparisons based on ER and HER2 expression subtypes. Investigation of the expression of multiple phosphorylated signaling proteins can be used for personalized targeted therapy. In invasive breast cancer, the overexpression of P38 MAPK may serve as a biomarker for the evaluation of P38 MAPK inhibitors.