Androgen-induced human breast cancer cell proliferation is mediated by discrete mechanisms in estrogen receptor-alpha-positive and -negative breast cancer cells

Progesterone modulates cell growth via integrin αvβ3-dependent pathway in progesterone receptor-negative MDA-MB-231 cells

Progesterone (P4) plays a pivotal role in regulating the cancer progression of various types, including breast cancer, primarily through its interaction with the P4 receptor (PR). In PR-negative breast cancer cells, P4 appears to function in mediating cancer progression, such as cell growth. However, the mechanisms underlying the roles of P4 in PR-negative breast cancer cells remain incompletely understood. This study aimed to investigate the effects of P4 on cell proliferation, gene expression, and signal transduction in PR-negative MDA-MB-231 breast cancer cells. P4-activated genes, associated with proliferation in breast cancer cells, exhibit a stimulating effect on cell growth in PR-negative MDA-MB-231 cells, while demonstrating an inhibitory impact in PR-positive MCF-7 cells. The use of arginine-glycine-aspartate (RGD) peptide successfully blocked P4-induced extracellular signal-regulated kinase 1/2 (ERK1/2) activation, aligning with computational models of P4 binding to integrin αvβ3. Disrupting integrin αvβ3 binding with RGD peptide or anti-integrin αvβ3 antibody altered P4-induced expression of proliferative genes and modified P4-induced cell growth in breast cancer cells. In conclusion, integrin αvβ3 appears to mediate P4-induced ERK1/2 signal pathway to regulate proliferation via alteration of proliferation-related gene expression in PR-negative breast cancer cells.

Integrins and Actions of Androgen in Breast Cancer

Androgen has been shown to regulate male physiological activities and cancer proliferation. It is used to antagonize estrogen-induced proliferative effects in breast cancer cells. However, evidence indicates that androgen can stimulate cancer cell growth in estrogen receptor (ER)-positive and ER-negative breast cancer cells via different types of receptors and different mechanisms. Androgen-induced cancer growth and metastasis link with different types of integrins. Integrin αvβ3 is predominantly expressed and activated in cancer cells and rapidly dividing endothelial cells. Programmed death-ligand 1 (PD-L1) also plays a vital role in cancer growth. The part of integrins in action with androgen in cancer cells is not fully mechanically understood. To clarify the interactions between androgen and integrin αvβ3, we carried out molecular modeling to explain the potential interactions of androgen with integrin αvβ3. The androgen-regulated mechanisms on PD-L1 and its effects were also addressed.

Pharmacological Targeting of Androgen Receptor Elicits Context-Specific Effects in Estrogen Receptor-Positive Breast Cancer

Androgen receptor (AR) is expressed in 80% to 90% of estrogen receptor α-positive (ER+) breast cancers. Accumulated evidence has shown that AR is a tumor suppressor and that its expression is associated with improved prognosis in ER+ breast cancer. However, both a selective AR agonist (RAD140) and an AR inhibitor (enzalutamide, ENZ) have shown a therapeutic effect on ER+ breast cancer, so the potential for clinical application of AR-targeting therapy for ER+ breast cancer is still in dispute. In this study, we evaluated the efficacy of ENZ and RAD140 in vivo and in vitro in AR+/ER+ breast cancer models, characterizing the relationship of AR and ER levels to response to AR-targeting drugs and investigating the alterations of global gene expression and chromatin binding of AR and ERα after ENZ treatment. In the AR-low setting, ENZ directly functioned as an ERα antagonist. Cell growth inhibition by ENZ in breast cancer with low AR expression was independent of AR and instead dependent on ER. In AR-high breast cancer models, AR repressed ERα signaling and ENZ promoted ERα signaling by antagonizing AR. In contrast, RAD140 activated AR signaling and suppressed AR-high tumor growth by deregulating ERα expression and blocking ERα function. Overall, analysis of the dynamic efficacies and outcomes of AR agonist, and antagonist in the presence of different AR and ERα levels reveals regulators of response and supports the clinical investigation of ENZ in selected ER+ tumors with a low AR/ER ratio and AR agonists in tumors with a high AR/ER ratio.

SIGNIFICANCE

The ratio of androgen receptor to estrogen receptor in breast cancer dictates the response to AR-targeted therapies, providing guidelines for developing AR-directed treatment strategies for patients with breast cancer.

Transcriptome profiling and proteomic validation reveals targets of the androgen receptor signaling in the BT-474 breast cancer cell line

BACKGROUND

Accumulating evidence suggests that the androgen receptor (AR) and its endogenous ligands influence disease progression in breast cancer (BCa). However, AR-mediated changes in BCa differ among the various BCa subtypes according to their hormone receptor profile [i.e., presence/absence of estrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor 2, (HER2)]. Thus, we explored the androgen-regulated transcriptomic changes in the ER⁺PR⁺HER2⁺ BCa cell line, BT-474, and compared them with PR-mediated changes.

METHODS

We performed RNA sequencing analysis in treated BT-474 cells with dihydrotestosterone (DHT) and progesterone. Validation of the top ten differentially androgen-regulated genes and a number of other genes found in enriched signaling pathways was performed by qRT-PCR in BT-474 and other BCa cell lines. In addition, a parallel reaction monitoring targeted proteomic approach was developed to verify selected transcripts at the protein level.

RESULTS

In total 19,450 transcripts were detected, of which 224 were differentially regulated after DHT treatment. The increased expression of two well-known androgen-regulated genes, KLK2 (p < 0.05) and KLK3 (p < 0.001), confirmed the successful androgen stimulation in BT-474 cells. The transcription factor, ZBTB16, was the most highly upregulated gene, with ~ 1000-fold change (p < 0.001). Pathway enrichment analysis revealed downregulation of the DNA replication processes (p < 0.05) and upregulation of the androgen signaling and fatty acid metabolism pathways (p < 0.05). Changes related to progesterone treatment showed opposite effects in gene expression than DHT treatment. Similar expression profiles were observed among other BCa cell lines expressing high levels of AR (ZR75.1 and MBA-MB-453). The parallel reaction monitoring targeted proteomic analysis further confirmed that altered protein expression (KLK3, ALOX15B) in the supernatant and cell lysate of DHT-treated BT-474 cells, compared to control cells.

DISCUSSION

Our findings suggest that AR modulates the metabolism of BT-474 cells by affecting the expression of a large number of genes and proteins. Based on further pathway analysis, we suggest that androgen receptor acts as a tumor suppressor in the BT-474 cells.

A Phase II Study Evaluating Orteronel, an Inhibitor of Androgen Biosynthesis, in Patients With Androgen Receptor (AR)-Expressing Metastatic Breast Cancer (MBC)

BACKGROUND

AR is a targetable pathway with AR modulation inhibiting estrogen- and androgen-mediated cell proliferation. Orteronel is an oral, selective, nonsteroidal inhibitor of 17, 20-lyase, a key enzyme in androgen biosynthesis. This study evaluated single-agent orteronel in AR+ metastatic breast cancer (MBC).

METHODS

Male/female patients with AR+ MBC were grouped in Cohort 1: AR+ TNBC with l-3 prior chemotherapy regimens or Cohort 2: AR+ HR+ (estrogen [ER+]/ progesterone receptor [PR+] positive) HER2+/- with 1 to 3 prior hormonal and at least 1 prior chemotherapy regimen. Patients with HER2+ MBC must have received at least 2 lines of HER2-targeted therapy. Orteronel was administered at 300 mg BID; response rate was the primary endpoint.

RESULTS

Seventy patients were enrolled (Cohort 1, n = 26 and Cohort 2, n = 44). Median treatment duration was 7.1 weeks. Seven patients were on treatment for ≥6 months. One of the 21 evaluated patients in Cohort 1 (4.8%) had an objective response. In Cohort 2, none of the first 23 patients to be evaluated had a response and accrual was stopped. Median progression-free and overall survival were 1.8 and 8.3 months, respectively. Toxicities were predominantly Grade 1 or 2 nausea/vomiting (36%) and fatigue (31%). Grade 3 or 4 events in ≥5% of patients included increased amylase/lipase (10%) and hypertension (6%).

CONCLUSIONS

Orteronel demonstrated limited clinical activity in heavily pre-treated AR+ MBC. Further development of orteronel in MBC is not recommended. Further efforts to validate the AR as a therapeutic target should focus on identifying new markers predictive of sensitivity to AR-targeted agents.

P68 RNA Helicase facilitates Breast Cancer progression by promoting Proliferation and Migration via PDGFR-β/AR axis

Aberrant expression of P68 RNA helicase (p68), a prototypical member of the DEAD box family of RNA helicases, contributes to tumor development and progression. P68 tyrosine phosphorylation induced by PDGF signaling facilitates cancer metastasis by promoting EMT. In this report, we show that p68 promotes breast cancer cell EMT and cell migration by upregulation of PDGF receptor β (PDGFR-β). Knockdown of p68 in MDA-MB-231 and BT549 cells significantly decreases PDGFR-β both in mRNA and protein levels. P68 promotes EMT and cell migration in response to PDGF-BB stimulation via upregulation of PDGFR-β, suggesting that p68 enhances PDGF signaling by a positive feedback loop in cancer cells. Furthermore, our study reveals that p68 mediates the effects of PDGFR-β in regulation of androgen receptor (AR) in breast cancer cells. We demonstrate that p68 and PDGFR-β co-regulate AR expression and promote androgen-mediated proliferation in breast cancer cells. Our studies uncover an important pathway of p68-PDGFR-β axis in promoting breast cancer progression.

Breast cancer risk in patients with polycystic ovary syndrome: a Mendelian randomization analysis

PURPOSE

The association between polycystic ovary syndrome (PCOS) and breast cancer remains inconclusive. Conventional observational studies are susceptible to inverse causality and potential confounders. With a Mendelian randomization (MR) approach, we aimed to investigate the causal relationship between genetically predicted PCOS and breast cancer risk.

METHODS

Our study included 11 PCOS-associated single nucleotide polymorphisms as instrumental variables identified by the latest genome-wide association study. Individual-level genetic summary data of participants were obtained from the Breast Cancer Association Consortium, with a total of 122,977 cases and 105,974 controls. The inverse-variance weighted method was applied to estimate the causality between genetically predicted PCOS and breast cancer risk. To further evaluate the pleiotropy, the weighted median and MR-Egger regression methods were implemented as well.

RESULTS

Our study demonstrated that genetically predicted PCOS was causally associated with an increased risk of overall breast cancer (odds ratio (OR) = 1.07; 95% confidence interval (CI) 1.02-1.12, p = 0.005). The subgroup analyses according to immunohistochemical type further illustrated that genetically predicted PCOS was associated with an increased risk of estrogen receptor (ER)-positive breast cancer (OR = 1.09; 95% CI 1.03-1.15, p = 0.002), while no causality was observed for ER-negative breast cancer (OR = 1.02; 95% CI 0.96-1.09, p = 0.463). In addition, no pleiotropy was found in our study.

CONCLUSIONS

Our findings indicated that PCOS was likely to be a causal factor in the development of ER-positive breast cancer, providing a better understanding for the etiology of breast cancer and the prevention of breast cancer.

Role of androgen and microRNA in triple-negative breast cancer

Breast cancer (BC) is the most frequent type of malignancy affecting females worldwide. Molecular-based studies resulted in an identification of at least four subtypes of breast carcinoma, including luminal A and luminal B, Human growth factor receptor (HER-2)-enriched and triple-negative tumors (basal-like and normal breast-like). A proportion of BC cases are of the triple-negative breast cancer (TNBC) type. TNBC lacks the expression of estrogen receptor (ER), progesterone receptor (PR), and HER-2, and is known to express androgen receptor (AR) at considerable levels. AR has been shown to promote the progression of TNBC. However, the exact mechanisms have yet to be unraveled. One of these mechanisms could be through regulating the expression of microRNA (miRNA) molecules, which play an important regulatory role in BC through post-transcriptional gene silencing. Activation of AR controls the expression of miRNA molecules, which target selective mRNAs, consequently, affecting protein expression. In this review we attempt to elucidate the relations between AR and miRNA in TNBC.

Coronaviruses and Integrin αvβ3: Does Thyroid Hormone Modify the Relationship?

BACKGROUND

Uptake of coronaviruses by target cells involves binding of the virus by cell ectoenzymes. For the etiologic agent of COVID-19 (SARS-CoV-2), a receptor has been identified as angiotensin-converting enzyme-2 (ACE2). Recently it has been suggested that plasma membrane integrins may be involved in the internalization and replication of clinically important coronaviruses. For example, integrin αvβ3 is involved in the cell uptake of a model porcine enteric α-coronavirus that causes human epidemics. ACE2 modulates the intracellular signaling generated by integrins.

OBJECTIVE

We propose that the cellular internalization of αvβ3 applies to uptake of coronaviruses bound to the integrin, and we evaluate the possibility that clinical host T4 may contribute to target cell uptake of coronavirus and to the consequence of cell uptake of the virus.

DISCUSSION AND CONCLUSIONS

The viral binding domain of the integrin is near the Arg-Gly-Asp (RGD) peptide-binding site and RGD molecules can affect virus binding. In this same locale on integrin αvβ3 is the receptor for thyroid hormone analogues, particularly, L-thyroxine (T4). By binding to the integrin, T4 has been shown to modulate the affinity of the integrin for other proteins, to control internalization of αvβ3 and to regulate the expression of a panel of cytokine genes, some of which are components of the 'cytokine storm' of viral infections. If T4 does influence coronavirus uptake by target cells, other thyroid hormone analogues, such as deaminated T4 and deaminated 3,5,3'-triiodo-L-thyronine (T3), are candidate agents to block the virus-relevant actions of T4 at integrin αvβ3 and possibly restrict virus uptake.

Nongenomic Actions of Thyroid Hormone: The Integrin Component

The extracellular domain of plasma membrane integrin αvβ3 contains a cell surface receptor for thyroid hormone analogues. The receptor is largely expressed and activated in tumor cells and rapidly dividing endothelial cells. The principal ligand for this receptor is l-thyroxine (T₄), usually regarded only as a prohormone for 3,5,3'-triiodo-l-thyronine (T₃), the hormone analogue that expresses thyroid hormone in the cell nucleus via nuclear receptors that are unrelated structurally to integrin αvβ3. At the integrin receptor for thyroid hormone, T₄ regulates cancer and endothelial cell division, tumor cell defense pathways (such as anti-apoptosis), and angiogenesis and supports metastasis, radioresistance, and chemoresistance. The molecular mechanisms involve signal transduction via mitogen-activated protein kinase and phosphatidylinositol 3-kinase, differential expression of multiple genes related to the listed cell processes, and regulation of activities of other cell surface proteins, such as vascular growth factor receptors. Tetraiodothyroacetic acid (tetrac) is derived from T₄ and competes with binding of T₄ to the integrin. In the absence of T₄, tetrac and chemically modified tetrac also have anticancer effects that culminate in altered gene transcription. Tumor xenografts are arrested by unmodified and chemically modified tetrac. The receptor requires further characterization in terms of contributions to nonmalignant cells, such as platelets and phagocytes. The integrin αvβ3 receptor for thyroid hormone offers a large panel of cellular actions that are relevant to cancer biology and that may be regulated by tetrac derivatives.

Androgen Receptor Expression and Its Correlation with Clinicopathological Parameters in Iranian Patients with Triple Negative Breast Cancer

BACKGROUND & OBJECTIVE

Our knowledge about correlation of androgen receptor expression and clinicopathological properties of triple-negative breast cancer (TNBC) patients is inadequate, particularly in the Iranian population. The main aim of the present study was to assess the AR expression in TNBC Iranian patients and evaluate its correlation with their clinicopathological parameters.

METHODS

Herein, 76 TNBC patients were evaluated for the AR expression by immunohistochemistry. The slides' staining intensity was investigated according to the average degree of nuclear staining and sub-classified into negative (0), weak (1), moderate (2), or strong (3). Subsequently, the positive cells percentage for each slide was assessed and sub-classified into <25% (1), 25-50% (2), 50-75% (3), and >75% (4). The aggregation of these two scores was used as the final score ranging from 0 to 7. While 4-7 scores were selected as positive, the others were included in the AR-negative expression group. Fisher's exact test was used to analyze the AR expression correlation with the clinicopathological parameters.

RESULTS

Positive immunoreactivity for AR was observed in 8 out of 76 (11%) specimens. No-correlation (P>0.05) was observed between the AR expression and grade, stage, lymph node status, and Ki-67 level. The AR-positive patients exhibited older age at the time of diagnosis (P=0.0339) and larger tumor size (P=0.0224) in comparison with the AR-negative patients. Low percentage of TNBC patients expressed AR and no significant correlation was observed between its expression and most of the clinicopathological parameters.

CONCLUSION

AR may not be a suitable biomarker and treatment target for the Iranian patients with TNBC.

Integrin αvβ3 in the Mediating Effects of Dihydrotestosterone and Resveratrol on Breast Cancer Cell Proliferation

Hormones and their receptors play an important role in the development and progression of breast cancer. Hormones regulate the proliferation of breast cancer cells through binding between estrogen or progestins and steroid receptors that may reside in the cytoplasm or be transcriptionally activated as steroid–protein nuclear receptor complexes. However, receptors for nonpeptide hormones also exist in the plasma membrane. Via those receptors, hormones are able to stimulate breast cancer cell proliferation when activated. Integrins are heterodimeric structural proteins of the plasma membrane. Their primary functions are to interact with extracellular matrix proteins and growth factors. Recently, integrin αvβ3 has been identified as a receptor for nonpeptide hormones, such as thyroid hormone and dihydrotestosterone (DHT). DHT promotes the proliferation of human breast cancer cells through binding to integrin αvβ3. A receptor for resveratrol, a polyphenol stilbene, also exists on this integrin in breast cancer cells, mediating the anti-proliferative, pro-apoptotic action of the compound in these cells. Unrelated activities of DHT and resveratrol that originate at integrin depend upon downstream stimulation of mitogen-activated protein kinase (MAPK, ERK1/2) activity, suggesting the existence of distinct, function-specific pools of ERK1/2 within the cell. This review will discuss the features of these receptors in breast cancer cells, in turn suggesting clinical applications that are based on the interactions of resveratrol/DHT with integrin αvβ3 and other androgen receptors.

The expression and prognostic role of EBP1 and relationship with AR in HER2+ breast cancer

Human epidermal growth factor receptor (HER)-2 positive (HER2⁺) breast cancer (BC) has a poor survival rate and is more aggressive in nature. HER2-targeting agents could be beneficial for patients with HER2⁺ BC. In addition, targeted therapy and chemotherapy have been successfully used. However, a few patients are resistant to treatment. ErbB3 binding protein 1 (EBP1) binds to HER3 and inhibits the proliferation and invasive potential of tumor cells. However, its role in HER2⁺ BC has not been demonstrated. In this study, we aimed to analyze the relationship between androgen receptor (AR) and EBP1 expression in HER2⁺ BC. A total of 282 cases (140 cases of HER2⁺ invasive BC and 142 HER2-negative invasive BC) were included in this study. We performed immunohistochemistry (IHC) to analyze the expression of AR and EBP1; thereafter, we evaluated the relationship between these two biomarkers and estrogen receptor (ER), progesterone receptor (PR), HER2, p53, Ki67 expression, and other clinicopathological parameters. Of the HER2⁺ cases, 67 (47.9%) showed high expression of EBP1 (EBP1^high) and 73 (52.1%) showed low/no expression of EBP1 (EBP1^low/no). EBP1 expression was correlated with AR expression, histological grade, and lymphatic metastasis (p < 0.001, < 0.001, and 0.013, respectively). Kaplan-Meier analysis revealed that AR⁺ and EBP1^low/no group had poorer overall survival (OS) and disease-free survival (DFS) compared with other groups (AR^- and EBP1^low/no, AR⁺ and EBP1^high, and AR^- and EBP1^high). AR⁺ and EBP1^low/no expression were independent prognostic factors for OS and DFS in HER2+ BC. This study showed the clinicopathological role of EBP1 and AR in HER2+ BC. Targeting EBP1 may be an effective treatment strategy for patients with AR⁺ HER2⁺ BC.

Synergistic action of folate intake and testosterone associated with breast cancer risk

The amount of irreparable DNA damage is a function of the rate of cell division, and the association between sex hormones and the risk of breast cancer has been explained by an increase in cell division. Folate intake insufficiency leads to disturbances in DNA replication and DNA repair. We hypothesized that folate intake insufficiency and high serum concentrations of sex hormones act synergistically on the risk of breast cancer. The aim of this study was to investigate the interaction between sex hormones (exposure of interest A) and dietary folate intake (exposure of interest B) on the risk of breast cancer. We included 342 breast cancer primary postmenopausal cases and 294 controls obtained from a large population-based case-control study. Multiple conditional logistic regression models were used for the analysis and interactions were tested. The joint effect of the lowest dietary folate intake (T1 < 259.40 mg/d) and the highest serum concentration of testosterone (T3 ≥ 0.410 on the risk of breast cancer was odds ratio = 9.18 (95% confidence interval 2.56-32.88) when compared to the lowest-risk category, namely, the group of women with the highest dietary folate intake (T3 > 381.29 mg/d) and the lowest serum concentration of testosterone (T1 ≤ 0.25 pg/mL). There were some indications that the estimated join effect was greater than the product of the estimated effects alone (P = .001). These findings have important public health implications with respect to reducing the risk of the most frequent cancer in women worldwide.

Controversial association between polycystic ovary syndrome and breast cancer

Polycystic ovary syndrome (PCOS) risk factors overlap with breast cancer, and the hormonal profile may be implicated in breast cancer pathogenesis. This study aims to report a literature review considering epidemiological and molecular mechanisms that correlate PCOS and breast cancer, as well as the influence of PCOS treatment on the incidence of breast cancer. Epidemiological studies failed to adjust potential variables that affect the risk and have thus provided inconclusive results. Molecular effects of androgenic pathways in breast cancer have been studied and androgens seem to have an inhibitory effect on mammary epithelial proliferation. However, increased bioavailable androgens were associated with recurrence of breast cancer due to conversion to oestrogens. Sex hormone-binding globulin has a role in hormone-dependent cancers and can be considered a marker for PCOS; a gene profile has already been linked to breast cancer risk in these patients. PCOS medical treatment is a promising tool for stratifying breast cancer risk due to the metabolic influence and hormonal environment. Clinical reports are inconsistent, emphasizing the need for further studies with a prospective design. In the future, the role of pharmacological interventions in PCOS will increase knowledge and awareness of breast cancer pathogenesis and will help to refine breast cancer risk stratification.

Consideration of breast cancer subtype in targeting the androgen receptor

The androgen receptor (AR) is a drug target in breast cancer, and AR-targeted therapies have induced tumor responses in breast cancer patients. In this review, we summarized the role of AR in breast cancer based on preclinical and clinical data. Response to AR-targeted therapies in unselected breast cancer populations is relatively low. Preclinical and clinical data show that AR antagonists might have a role in estrogen receptor (ER)-negative/AR-positive tumors. The prognostic value of AR for patients remains uncertain due to the use of various antibodies and cut-off values for immunohistochemical assessment. To get more insight into the role of AR in breast cancer, we additionally performed a retrospective pooled analysis to determine the prognostic value of the AR using mRNA profiles of 7270 primary breast tumors. Our analysis shows that a higher AR mRNA level is associated with improved disease outcome in patients with ER-positive/human epidermal growth factor receptor 2 (HER2)-negative tumors, but with worse disease outcome in HER2-positive subgroups. In conclusion, next to AR expression, incorporation of additional tumor characteristics will potentially make AR targeting a more valuable therapeutic strategy in breast cancer.

A human-derived prostate co-culture microtissue model using epithelial (RWPE-1) and stromal (WPMY-1) cell lines

The development and normal function of prostate tissue depends on signalling interactions between stromal and epithelial compartments. Development of a prostate microtissue composed of these two components can help identify substance exposures that could cause adverse effects in humans as part of a non-animal risk assessment. In this study, prostate microtissues composed of human derived stromal (WPMY-1) and epithelial (RWPE-1) cell lines grown in scaffold-free hydrogels were developed and characterized using immunohistochemistry, light microscopy, and qRT-PCR. Within 5 days after seeding, the microtissues self-organized into spheroids consisting of a core of stromal WPMY-1 cells surrounded by epithelial RWPE-1 cells. The RWPE-1 layer is reflective of intermediate prostatic epithelium, expressing both characteristics of the luminal (high expression of PSA) and basal (high expression of cytokeratins 5/6 and 14) epithelial cells. The response of the microtissues to an androgen (dihydrotestosterone, DHT) and an anti-androgen (flutamide) was also investigated. Treatment with DHT, flutamide or a mixture of DHT and flutamide indicated that the morphology and self-organization of the microtissues is androgen dependent. qRT-PCR data showed that a saturating concentration of DHT increased the expression of genes coding for the estrogen receptors (ESR1 and ESR2) and decreased the expression of CYP1B1 without affecting the expression of the androgen receptor. With further development and optimization RWPE-1/WPMY-1 microtissues can play an important role in non-animal risk assessments.

MicroRNAs and Androgen Receptor: Emerging Players in Breast Cancer

Breast cancer (BC) is the most common cause of cancer among women, with a high incidence rate occurrence every year worldwide despite advances in its management. BC is characterized by a spectrum of subtypes which respond differently to treatments due to their biological features, representing the main issue in the control of this type of malignancy. Androgen receptor (AR) is emerging as a target to investigate among hormone receptors, since it seems to play a role at various stages of development of specific BC subsets. For this reason, in recent years AR has become very important in the clinical practice, although its role remains controversial. A number of studies have proposed a correlation between microRNAs (miRNAs), a class of gene expression modulators, and AR in prostate cancer (PC), but there are still few evidences about the relationship between miRNAs and AR in BC. The purpose of this review is to present a state of the art scenario with consideration to the most recent discoveries about miRNAs involved in the AR associated pathogenesis of BC, in order to provide new insights into the role of miRNAs as key drivers in the modulation of AR, and possible actors in the development and progression of BC. Moreover, we consider findings about involvement of AR signaling in all stages of BC, highlighting its association with different subsets of breast carcinomas and with pre- and postmenopausal state of patients.

Bioactivity of Thyroid Hormone Analogs at Cancer Cells

In the context of genomic thyroid hormone actions in normal (noncancer) cells that involve primary interactions with nuclear thyroid hormone receptors (TRs), L-thyroxine (T4), and 3,3',5'-triiodo-L-thyronine (reverse T3, rT3) have little bioactivity. In terms of TRs, T4 is a prohormone from which the active nuclear ligand, 3,5,3'-triido-L-thyronine (T3), is generated by deiodination. Deaminated T4 and T3 metabolites have different genomic effects: tetraiodothyroacetic acid (tetrac) is a low grade thyromimetic derivative of T4, whereas triiodothyroacetic acid (triac), the acetic acid metabolite of T3, has substantial thyromimetic activity. In cancer cells, the cell surface receptor for thyroid hormone on integrin αvβ3 mediates non-genomic actions of thyroid hormone analogs. The integrin is expressed in large measure by cancer cells and dividing endothelial cells and has a substantially different panel of responses to thyroid hormone analogs. At αvβ3, T4 is a potent proliferative, anti-apoptotic and pro-angiogenic hormone and is the primary ligand. rT3 may also be proliferative at this site. In contrast, tetrac and triac are antagonists of T4 at αvβ3, but also have anticancer properties at this site that are independent of their effects on the binding of T4.

Novel synthetic cyclic integrin αvβ3 binding peptide ALOS4: Antitumor activity in mouse melanoma models

ALOS4, a unique synthetic cyclic peptide without resemblance to known integrin ligand sequences, was discovered through repeated biopanning with pIII phage expressing a disulfide-constrained nonapeptide library. Binding assays using a FITC-labeled analogue demonstrated selective binding to immobilized αvβ3 and a lack of significant binding to other common proteins, such as bovine serum albumin and collagen. In B16F10 cell cultures, ALOS4 treatment at 72 h inhibited cell migration (30%) and adhesion (up to 67%). Immunofluorescent imaging an ALOS4-FITC analogue with B16F10 cells demonstrated rapid cell surface binding, and uptake and localization in the cytoplasm. Daily injections of ALOS4 (0.1, 0.3 or 0.5 mg/kg i.p.) to mice inoculated with B16F10 mouse melanoma cells in two different cancer models, metastatic and subcutaneous tumor, resulted in reduction of lung tumor count (metastatic) and tumor mass (subcutaneous) and increased survival of animals monitored to 45 and 60 days, respectively. Examination of cellular activity indicated that ALOS4 produces inhibition of cell migration and adhesion in a concentration-dependent manner. Collectively, these results suggest that ALOS4 is a structurally-unique selective αvβ3 integrin ligand with potential anti-metastatic activity.

The role of the AR/ER ratio in ER-positive breast cancer patients

The significance of androgen receptor (AR) in breast cancer (BC) management is not fully defined, and it is still ambiguous how the level of AR expression influences oestrogen receptor-positive (ER+) tumours. The aim of the present study was to analyse the prognostic impact of AR/ER ratio, evaluated by immunohistochemistry (IHC), correlating this value with clinical, pathological and molecular characteristics. We retrospectively selected a cohort of 402 ER+BC patients. On each tumour, IHC analyses for AR, ER, PgR, HER2 and Ki67 were performed and AR+ cases were used to calculate the AR/ER value. A cut-off of ≥2 was selected using receiver-operating characteristic (ROC) curve analyses. RNA from 19 cases with AR/ER≥2 was extracted and used for Prosigna-PAM50 assays. Tumours with AR/ER≥2 (6%) showed more frequent metastatic lymph nodes, larger size, higher histological grade and lower PgR levels than cases with AR/ER<2. Multivariate analysis confirmed that patients with AR/ER≥2 had worse disease-free interval (DFI) and disease-specific survival (DSS) (hazard ratios (HR) = 4.96 for DFI and HR = 8.69 for DSS, both P ≤ 0.004). According to the Prosigna-PAM50 assay, 63% (12/19) of these cases resulted in intermediate or high risk of recurrence categories. Additionally, although all samples were positive for ER assessed by IHC, the molecular test assigned 47.4% (9/19) of BCs to intrinsic non-luminal subtypes. In conclusion, the AR/ER ratio ≥2 identifies a subgroup of patients with aggressive biological features and may represent an additional independent marker of worse BC prognosis. Moreover, the Prosigna-PAM50 results indicate that a significant number of cases with AR/ER≥2 could be non-luminal tumours.

Beyond the Matrix: The Many Non-ECM Ligands for Integrins

The traditional view of integrins portrays these highly conserved cell surface receptors as mediators of cellular attachment to the extracellular matrix (ECM), and to a lesser degree, as coordinators of leukocyte adhesion to the endothelium. These canonical activities are indispensable; however, there is also a wide variety of integrin functions mediated by non-ECM ligands that transcend the traditional roles of integrins. Some of these unorthodox roles involve cell-cell interactions and are engaged to support immune functions such as leukocyte transmigration, recognition of opsonization factors, and stimulation of neutrophil extracellular traps. Other cell-cell interactions mediated by integrins include hematopoietic stem cell and tumor cell homing to target tissues. Integrins also serve as cell-surface receptors for various growth factors, hormones, and small molecules. Interestingly, integrins have also been exploited by a wide variety of organisms including viruses and bacteria to support infectious activities such as cellular adhesion and/or cellular internalization. Additionally, the disruption of integrin function through the use of soluble integrin ligands is a common strategy adopted by several parasites in order to inhibit blood clotting during hematophagy, or by venomous snakes to kill prey. In this review, we strive to go beyond the matrix and summarize non-ECM ligands that interact with integrins in order to highlight these non-traditional functions of integrins.

Mechanisms of action of nonpeptide hormones on resveratrol-induced antiproliferation of cancer cells

Nonpeptide hormones, such as thyroid hormone, dihydrotestosterone, and estrogen, have been shown to stimulate cancer proliferation via different mechanisms. Aside from their cytosolic or membrane-bound receptors, there are receptors on integrin α_v β₃ for nonpeptide hormones. Interaction between hormones and integrin α_v β₃ can induce signal transduction and eventually stimulate cancer cell proliferation. Resveratrol induces inducible COX-2-dependent antiproliferation via integrin α_v β₃ . Resveratrol and hormone-induced signals are both transduced by activated extracellular-regulated kinases 1 and 2 (ERK1/2); however, hormones promote cell proliferation, while resveratrol induces antiproliferation in cancer cells. Hormones inhibit resveratrol-stimulated phosphorylation of p53 on Ser15, resveratrol-induced nuclear COX-2 accumulation, and formation of p53-COX-2 nuclear complexes. Subsequently, hormones impair resveratrol-induced COX-2-/p53-dependent gene expression. The inhibitory effects of hormones on resveratrol action can be blocked by different antagonists of specific nonpeptide hormone receptors but not integrin α_v β₃ blockers. Results suggest that nonpeptide hormones inhibit resveratrol-induced antiproliferation in cancer cells downstream of the interaction between ligand and receptor and ERK1/2 activation to interfere with nuclear COX-2 accumulation. Thus, the surface receptor sites for resveratrol and nonpeptide hormones are distinct and can induce discrete ERK1/2-dependent downstream antiproliferation biological activities. It also indicates the complex pathways by which antiproliferation is induced by resveratrol in various physiological hormonal environments. .

Mechanisms of dihydrotestosterone action on resveratrol-induced anti-proliferation in breast cancer cells with different ERα status

Dihydrotestosterone (DHT) has been shown to promote breast cancer growth via different mechanisms. In addition to binding to ERα, the DHT membrane receptor exists on integrin αvβ3. Resveratrol induces p53-dependent apoptosis via plasma membrane integrin αvβ3. Resveratrol and DHT signals are both transduced by activated ERK1/2; however, DHT promotes cell proliferation in cancer cells, whereas resveratrol is pro-apoptotic. In this study, we examined the mechanism by which DHT inhibits resveratrol-induced apoptosis in human ERα positive (MCF-7) and negative (MDA-MB-231) breast cancer cells. DHT inhibited resveratrol-stimulated phosphorylation of Ser-15 of p53 in a concentration-dependent manner. These effects of DHT on resveratrol action were blocked by an ERα antagonist, ICI 182,780, in MCF-7 breast cancer cells. DHT inhibited resveratrol-induced nuclear complex of p53-COX-2 formation which is required p53-dependent apoptosis. ChIP studies of COX-2/p53 binding to DNA and expression of p53-responsive genes indicated that DHT inhibited resveratrol-induced p53-directed transcriptional activity. In addition, DHT did inhibit resveratrol-induced COX-2/p53-dependent gene expression. These results suggest that DHT inhibits p53-dependent apoptosis in breast cancer cells by interfering with nuclear COX-2 accumulation which is essential for stimulation of apoptotic pathways. Thus, the surface receptor sites for resveratrol and DHT are discrete and activate ERK1/2-dependent downstream effects on apoptosis that are distinctive. These studies provide new insights into the antagonizing effects of resveratrol versus DHT, an important step toward better understanding and eventually treating breast cancer. It also indicates the complex pathways by which apoptosis is induced by resveratrol in DHT-depleted and -repleted environments.

Avβ3 integrin: Pathogenetic role in osteotropic tumors

The interplay of cancer cells and accessory cells within the microenvironment drives signals regulating the proliferation, migration and skeleton colonization. Osteotropism of tumor cells depends on chemokine activation, production of soluble factors and defective gene expression that cooperate within the metastatic niche to the bone resorbing functions of osteoclasts. Adhesion of cancer cells to the extracellular matrix is regulated by integrins as αvβ3 that enhances their invasiveness, pro-tumor angiogenesis and skeleton invasion. Therefore, αvβ3 signaling is implicated in enhancing osteotropism of breast and prostate cancers as well as of multiple myeloma. Targeting of αvβ3 has been adopted to restrain the tumor progression in several cancer models leading to improvement of overall survival as effect of the reduction of both tumor burden and osteotropism by malignant cells. Here, we review both the role of αvβ3 in malignant osteoclastogenesis and its potential targeting to restrain the bone colonization by skeleton invading cancers.

Expression of androgen receptor and its association with estrogen receptor and androgen receptor downstream proteins in normal/benign breast luminal epithelium

The androgen receptor (AR) is strongly expressed in the majority of breast carcinomas, but its role in breast hormonal carcinogenesis is not clear. We believe a better knowledge of the biology of normal/benign breast tissue will be the key to understanding this process. Using standard immunohistochemical staining on consecutive sections and dual immunohistochemical labeling, we studied the expression pattern of AR and estrogen receptor (ER) in normal/benign breast luminal epithelial cells. We found that most of the AR-positive cells are also ER positive, about 10% of the cells are AR-positive only, whereas ER-positive only cells are uncommon, a distribution pattern of hormone receptor expression similar to what was revealed in invasive breast carcinomas. Whereas the expression of AR downstream proteins, such as prostate-specific antigen and gross cystic disease fluid protein, was either negative or unrelated to the AR status. We conclude that AR and ER expression status in invasive breast carcinomas reflects that of their progenitor cells in terminal duct lobular units. Our study did not reveal the expression of AR downstream proteins in normal/benign luminal epithelial cells at the regular immunohistochemistry level.

Recurrence of differentiated thyroid carcinoma during full TSH suppression: is the tumor now thyroid hormone dependent?

Well-standardized primary treatment and long-term management of differentiated thyroid carcinoma (DTC) include lowering or suppression of host thyrotropin (TSH) with exogenous L-thyroxine (T₄). This treatment recognizes the trophic action of TSH on DTC cells. Suppression of endogenous TSH with T₄ is continued in recurrent disease. However, T₄ can induce proliferation of follicular and papillary thyroid carcinoma cell lines and of other human carcinoma cells. The proliferative mechanism is initiated at a cell surface receptor for T₄ on integrin αvβ3, a receptor by which the hormone also inhibits p53-dependent apoptosis in tumor cells. In recurrent DTC with satisfactory suppression of endogenous TSH, we discuss here the possibility that the tumor is no longer TSH dependent and that T₄ has become a critical growth factor for the cancer.

Nanotetrac targets integrin αvβ3 on tumor cells to disorder cell defense pathways and block angiogenesis

The extracellular domain of integrin αvβ3 contains a receptor for thyroid hormone and hormone analogs. The integrin is amply expressed by tumor cells and dividing blood vessel cells. The proangiogenic properties of thyroid hormone and the capacity of the hormone to promote cancer cell proliferation are functions regulated nongenomically by the hormone receptor on αvβ3. An L-thyroxine (T4) analog, tetraiodothyroacetic acid (tetrac), blocks binding of T4 and 3,5,3'-triiodo-L-thyronine (T3) by αvβ3 and inhibits angiogenic activity of thyroid hormone. Covalently bound to a 200 nm nanoparticle that limits its activity to the cell exterior, tetrac reformulated as Nanotetrac has additional effects mediated by αvβ3 beyond the inhibition of binding of T4 and T3 to the integrin. These actions of Nanotetrac include disruption of transcription of cell survival pathway genes, promotion of apoptosis by multiple mechanisms, and interruption of repair of double-strand deoxyribonucleic acid breaks caused by irradiation of cells. Among the genes whose expression is suppressed by Nanotetrac are EGFR, VEGFA, multiple cyclins, catenins, and multiple cytokines. Nanotetrac has been effective as a chemotherapeutic agent in preclinical studies of human cancer xenografts. The low concentrations of αvβ3 on the surface of quiescent nonmalignant cells have minimized toxicity of the agent in animal studies.

Evidence of androgen action in endometrial and ovarian cancers

Endometrial cancer (EC) and ovarian cancer are common gynaecological malignancies. The impact of androgen action in these cancers is poorly understood; however, there is emerging evidence to suggest that targeting androgen signalling may be of therapeutic benefit. Epidemiological evidence suggests that there is an increased risk of EC associated with exposure to elevated levels of androgens, and genetic variants in genes related to both androgen biosynthesis and action are associated with an increased risk of both EC and ovarian cancer. Androgen receptors (ARs) may be a potential therapeutic target in EC due to reported anti-proliferative activities of androgens. By contrast, androgens may promote growth of some ovarian cancers and anti-androgen therapy has been proposed. Introduction of new therapies targeting ARs expressed in EC or ovarian cancer will require a much greater understanding of the impacts of cell context-specific AR-dependent signalling and how ARs can crosstalk with other steroid receptors during progression of disease. This review considers the evidence that androgens may be important in the aetiology of EC and ovarian cancer with discussion of evidence for androgen action in normal and malignant endometrial and ovarian tissue.

Gender effect in experimental models of human medulloblastoma: does the estrogen receptor β signaling play a role?

Background

The male-to-female sex ratio for medulloblastoma (MB) is approximately 1.5∶1, female gender being also a favorable prognostic factor. This study aimed at evaluating the impact of gender on MB tumorigenesis.

Methods

In vitro activity of 17β-estradiol (E₂), DPN [2,3-bis(4-hydroxyphenyl)-propionitrile, a selective estrogen receptor β (ERβ)-agonist], PPT [4,4′,4″-(4-Propyl-[1H]-pyrazole-1,3,5-triyl) trisphenol, a selective ERα-agonist] or DHT (5 alpha-dihydrotestosterone) was evaluated in three human MB cell lines. D283 Med cells were transplanted into athymic mice.

Results

A significant expression of ERβ, with little or no ERα, and low AR (androgen receptor) was found in MB cell lines. The compounds tested did not affect cell proliferation. In vivo, we observed a significantly lower growth of D283 Med in nude female mice compared to males. At microscopic examination, tumors from females showed a shift towards differentiation, as evaluated by lower nestin, and higher NSE (neuron-specific enolase) and GFAP (glial fibrillary acidic protein) expression compared to males. Tumors from females also showed lower Ki67 and p53 expression. The wild-type ERβ protein (ERβ1) was lost in male tumors, while it was a permanent feature in females, and a strong negative correlation was found between Ki67 and ERβ1 expression. Conversely, tumor levels of ERβ2 and ERβ5 did not significantly differ between genders. Increased levels of cyclin-dependent kinase inhibitor p21 were observed in females, suggesting that estrogen may decrease tumor growth through blocking cell cycle progression. An inhibition of the insulin-like growth factor I (IGF-I) signaling was also evident in females.

Conclusion

We provides mechanistic evidence supporting the idea that ERβ1 signaling may have pro-differentiation and tumor suppressive function in medulloblastomas.

Revising the role of the androgen receptor in breast cancer

Breast cancer (BC) is traditionally viewed as an oestrogen-dependent disease in which the androgen receptor (AR) is inhibitory, counteracting the oncogenic activity of oestrogen receptor α (ERα (ESR1)). Most probably as a result of this crosstalk, the AR has prognostic value in ER-positive disease, with AR positivity reported to correlate with a better prognosis. Activation of the AR pathway has been previously used as a therapeutic strategy to treat BC, but its usage declined following the introduction of the anti-oestrogen tamoxifen. More recently, it has been demonstrated that a subset of triple-negative BCs (molecular apocrine) are dependent upon androgen signalling for growth and therapies that inhibit androgen signalling, currently used for the treatment of prostate cancer, e.g. the antiandrogen bicalutamide and the CYP17 inhibitor abiraterone acetate are undergoing clinical trials to investigate their efficacy in this BC subtype. This review summarises the current knowledge of AR activity in BC.

Thyroid: biological actions of 'nonclassical' thyroid hormones

Thyroid hormones (THs) are produced by the thyroid gland and converted in peripheral organs by deiodinases. THs regulate cell functions through two distinct mechanisms: genomic (nuclear) and nongenomic (non-nuclear). Many TH effects are mediated by the genomic pathway--a mechanism that requires TH activation of nuclear thyroid hormone receptors. The overall nongenomic processes, emerging as important accessory mechanisms in TH actions, have been observed at the plasma membrane, in the cytoplasm and cytoskeleton, and in organelles. Some products of peripheral TH metabolism (besides triiodo-L-thyronine), now termed 'nonclassical THs', were previously considered as inactive breakdown products. However, several reports have recently shown that they may have relevant biological effects. The recent accumulation of knowledge on how classical and nonclassical THs modulate the activity of membrane receptors, components of the mitochondrial respiratory chain, kinases and deacetylases, opened the door to the discovery of new pathways through which they act. We reviewed the current state-of-the-art on the actions of the nonclassical THs, discussing the role that these endogenous TH metabolites may have in the modulation of thyroid-related effects in organisms with differing complexity, ranging from nonmammals to humans.

Estrogen receptor beta as a novel target of androgen receptor action in breast cancer cell lines

INTRODUCTION

The two isoforms of estrogen receptor (ER) alpha and beta play opposite roles in regulating proliferation and differentiation of breast cancers, with ER-alpha mediating mitogenic effects and ER-beta acting as a tumor suppressor. Emerging data have reported that androgen receptor (AR) activation inhibits ER-positive breast cancer progression mainly by antagonizing ER-alpha signaling. However, to date no studies have specifically evaluated a potential involvement of ER-beta in the inhibitory effects of androgens.

METHODS

ER-beta expression was examined in human breast cancer cell lines using real-time PCR, Western blotting and small interfering RNA (siRNA) assays. Mutagenesis studies, electromobility shift assay (EMSA) and chromatin immunoprecipitation (ChIP) analysis were performed to assess the effects of mibolerone/AR on ER-beta promoter activity and binding.

RESULTS

In this study, we demonstrate that mibolerone, a synthetic androgen ligand, up-regulates ER-beta mRNA and protein levels in ER-positive breast cancer cells. Transient transfection experiments, using a vector containing the human ER-beta promoter region, show that mibolerone increases basal ER-beta promoter activity. Site-directed mutagenesis and deletion analysis reveal that an androgen response element (ARE), TGTTCT motif located at positions -383 and -377, is critical for mibolerone-induced ER-beta up-regulation in breast cancer cells. This occurs through an increased recruitment of AR to the ARE site within the ER-beta promoter region, along with an enhanced occupancy of RNA polymerase II. Finally, silencing of ER-beta gene expression by RNA interference is able to partially reverse the effects of mibolerone on cell proliferation, p21 and cyclin D1 expression.

CONCLUSIONS

Collectively, these data provide evidence for a novel mechanism by which activated AR, through an up-regulation of ER-beta gene expression, inhibits breast cancer cell growth.

Cancer Cell Gene Expression Modulated from Plasma Membrane Integrin αvβ3 by Thyroid Hormone and Nanoparticulate Tetrac

Integrin αvβ3 is generously expressed by cancer cells and rapidly dividing endothelial cells. The principal ligands of the integrin are extracellular matrix proteins, but we have described a cell surface small molecule receptor on αvβ3 that specifically binds thyroid hormone and thyroid hormone analogs. From this receptor, thyroid hormone (l-thyroxine, T4; 3,5,3'-triiodo-l-thyronine, T3) and tetraiodothyroacetic acid (tetrac) regulate expression of specific genes by a mechanism that is initiated non-genomically. At the integrin, T4 and T3 at physiological concentrations are pro-angiogenic by multiple mechanisms that include gene expression, and T4 supports tumor cell proliferation. Tetrac blocks the transcriptional activities directed by T4 and T3 at αvβ3, but, independently of T4 and T3, tetrac modulates transcription of cancer cell genes that are important to cell survival pathways, control of the cell cycle, angiogenesis, apoptosis, cell export of chemotherapeutic agents, and repair of double-strand DNA breaks. We have covalently bound tetrac to a 200 nm biodegradable nanoparticle that prohibits cell entry of tetrac and limits its action to the hormone receptor on the extracellular domain of plasma membrane αvβ3. This reformulation has greater potency than unmodified tetrac at the integrin and affects a broader range of cancer-relevant genes. In addition to these actions on intra-cellular kinase-mediated regulation of gene expression, hormone analogs at αvβ3 have additional effects on intra-cellular protein-trafficking (cytosol compartment to nucleus), nucleoprotein phosphorylation, and generation of nuclear coactivator complexes that are relevant to traditional genomic actions of T3. Thus, previously unrecognized cell surface-initiated actions of thyroid hormone and tetrac formulations at αvβ3 offer opportunities to regulate angiogenesis and multiple aspects of cancer cell behavior.

Activation of AR sensitizes breast carcinomas to NVP-BEZ235's therapeutic effect mediated by PTEN and KLLN upregulation

NVP-BEZ235 is a newly developed dual PI3K/mTOR inhibitor, being tested in multiple clinical trials, including breast cancer. NVP-BEZ235 selectively induces cell growth inhibition in a subset, but not all, breast cancer cell lines. However, it remains a challenge to distinguish between sensitive and resistant tumors, particularly in the pretreatment setting. Here, we used ten breast cancer cell lines to compare NVP-BEZ235 sensitivity and in the context of androgen receptor (AR) activation during NVP-BEZ235 treatment. We also used female SCID mice bearing breast tumor xenografts to investigate the beneficial effect of dihydrotestosterone/NVP-BEZ235 combination treatment compared with each alone. We found that AR-positive breast cancer cell lines are much more sensitive to NVP-BEZ235 compared with AR-negative cells, regardless of PTEN or PI3KCA status. Reintroducing AR expression in NVP-BEZ235 nonresponsive AR-negative cells restored the response. DHT/NVP-BEZ235 combination not only resulted in a more significant growth inhibition than either drug alone, but also achieved tumor regression and complete responses for AR(+)/ER(+) tumors. This beneficial effect was mediated by dihydrotestosterone (DHT)-induced PTEN and KLLN expression. Furthermore, DHT could also reverse NVP-BEZ235-induced side effects such as skin rash and weight loss. Our data suggest that AR expression may be an independent predictive biomarker for response to NVP-BEZ235. AR induction could add benefit during NVP-BEZ235 treatment in patients, especially with AR(+)/ER(+) breast carcinomas.

Adjunctive input to the nuclear thyroid hormone receptor from the cell surface receptor for the hormone

At thyroid hormone response elements on specific genes, complexes of nuclear thyroid hormone receptors (TRs) and 3,5,3'-triiodo-L-thyronine (T(3)), coactivator or corepressor nucleoproteins, and histone acetylases or deacetylases mediate genomic effects of the hormone. Nongenomic effects of the hormone are those whose initiation does not primarily depend upon formation of the TR-T(3) complex. Among the nongenomic effects of thyroid hormone are a set of actions initiated at a cell surface receptor on integrin αvβ3 that are relevant to a) intracellular trafficking of proteins, including TRβ1, b) serine phosphorylation and acetylation of this nuclear receptor, c) assembly within the nucleus of complexes of coactivators and corepressor, and d) transcription of specific genes, including that for TRβ1. These actions initiated at αvβ3 are reviewed here and appear to be adjunctive to the genomic actions of the TR-T(3) complex.

Thyroid hormones and mitochondria: with a brief look at derivatives and analogues

Thyroid hormones (TH) have a multiplicity of effects. Early in life, they mainly affect development and differentiation, while later on they have particularly important influences over metabolic processes in almost all tissues. It is now quite widely accepted that thyroid hormones have two types of effects on mitochondria. The first is a rapid stimulation of respiration, which is evident within minutes/hours after hormone treatment, and it is probable that extranuclear/non-genomic mechanisms underlie this effect. The second response occurs one to several days after hormone treatment, and leads to mitochondrial biogenesis and to a change in mitochondrial mass. The hormone signal for the second response involves both T3-responsive nuclear genes and a direct action of T3 at mitochondrial binding sites. T3, by binding to a specific mitochondrial receptor and affecting the transcription apparatus, may thus act in a coordinated manner with the T3 nuclear pathway to regulate mitochondrial biogenesis and turnover. Transcription factors, coactivators, corepressors, signaling pathways and, perhaps, all play roles in these mechanisms. This review article focuses chiefly on TH, but also looks briefly at some analogues and derivatives (on which the data is still somewhat patchy). We summarize data obtained recently and in the past to try to obtain an updated picture of the current research position concerning the metabolic effects of TH, with particular emphasis on those exerted via mitochondria.

Nuclear monomeric integrin αv in cancer cells is a coactivator regulated by thyroid hormone

Thyroid hormone induces tumor cell and blood vessel cell proliferation via a cell surface receptor on heterodimeric integrin αvβ3. We investigated the role of thyroid hormone-induced internalization of nuclear integrin αv monomer. Physiological concentration of thyroxine (free T4, 10(-10) M), but not 3,5,3'-triiodo-l-thyronine (T3), induced cellular internalization and nuclear translocation of integrin αv monomer in human non-small-cell lung cancer (H522) and ovarian carcinoma (OVCAR-3) cells. T4 did not complex with integrin αv monomer during its internalization. The αv monomer was phosphorylated by activated ERK1/2 when it heterodimerized with integrin β3 in vitro. Nuclear αv complexed with transcriptional coactivator proteins, p300 and STAT1, and with corepressor proteins, NCoR and SMRT. Nuclear αv monomer in T4-exposed cells, but not integrin β3, bound to promoters of specific genes that have important roles in cancer cells, including estrogen receptor-α, cyclooxygenase-2, hypoxia-inducible factor-1α, and thyroid hormone receptor β1 in chromatin immunoprecipitation assay. In summary, monomeric αv is a novel coactivator regulated from the cell surface by thyroid hormone for the expression of genes involved in tumorigenesis and angiogenesis. This study also offers a mechanism for modulation of gene expression by thyroid hormone that is adjunctive to the nuclear hormone receptor (TR)-T3 pathway.

Androgen receptor-induced tumor suppressor, KLLN, inhibits breast cancer growth and transcriptionally activates p53/p73-mediated apoptosis in breast carcinomas

Androgen receptor (AR) expression by immunohistochemistry correlates with better prognosis and survival among breast cancer patients. We and others have shown that AR inhibits proliferation and induces apoptosis in breast cancer cells. However, the mechanism of AR's anti-tumor effect in breast cancer is still not fully understood. Our recent study indicates that AR upregulates expression of tumor suppressor gene PTEN by promoter activation in breast cancer. KLLN, encoding KLLN protein, is a newly identified gene, which shares a bidirectional promoter with PTEN and is transcribed in the opposite direction. So far, the function of KLLN has never been studied in tumorigenesis. Here, we define KLLN as a tumor suppressor in breast carcinomas, which inhibits tumor growth and invasiveness. After analyzing 188 normal breast and 1247 malignant breast cancer tissues, we observed the loss of KLLN in multiple breast cancer subtypes and this decreased KLLN expression associates with tumor progression and increasing histological grade in invasive carcinomas. We characterize KLLN, for the first time, as a transcription factor, directly promoting the expression of TP53 and TP73, with consequent elevated apoptosis and cell cycle arrest in breast cancer cells. We demonstrate, in vitro and in murine xenograph models, that both KLLN and PTEN are AR-target genes, mediating androgen-induced growth inhibition and apoptosis in breast cancer cells. Our observations suggest that KLLN might be used as a potential prognostic marker and novel therapy target for breast carcinomas.

Recent developments in antiandrogens and selective androgen receptor modulators

The androgens testosterone and dihydrotestosterone play an essential role in the development and maintenance of primary and secondary male characteristics. Androgens bind to a specific androgen receptor (AR), a ligand-dependent transcription factor which controls the expression of a large number of downstream target genes. The AR is an essential player in early and late prostate cancer, and may also be involved in some forms of breast cancer. It also represents a drug target for the treatment of hypogonadism. Recent studies furthermore indicate that targeting the AR in pathologies such as frailty syndrome, cachexia or polycystic ovary syndrome may have clinical benefit. Numerous AR ligands with very different pharmacological properties have been identified in the last 40 years and helped to treat several of these diseases. However, progress still needs to be made in order to find compounds with an improved profile with regard to efficacy, differentiation and side-effects. This will only be achieved through a better understanding of the mechanisms involved in normal and aberrant AR signaling.

Combined QM/MM study of thyroid and steroid hormone analogue interactions with αvβ3 integrin

Recent biochemical studies have identified a cell surface receptor for thyroid and steroid hormones that bind near the arginine-glycine-aspartate (RGD) recognition site on the heterodimeric αvβ3 integrin. To further characterize the intermolecular interactions for a series of hormone analogues, combined quantum mechanical and molecular mechanical (QM/MM) methods were used to calculate their interaction energies. All calculations were performed in the presence of either calcium (Ca(2+)) or magnesium (Mg(2+)) ions. These data reveal that 3,5'-triiodothyronine (T(3)) and 3,5,3',5'-tetraiodothyroacetic acid (T(4)ac) bound in two different modes, occupying two alternate sites, one of which is along the Arg side chain of the RGD cyclic peptide site. These orientations differ from those of the other ligands whose alternate binding modes placed the ligands deeper within the RGD binding pocket. These observations are consistent with biological data that indicate the presence of two discrete binding sites that control distinct downstream signal transduction pathways for T(3).

Interaction of purinergic receptors with GPCRs, ion channels, tyrosine kinase and steroid hormone receptors orchestrates cell function

Extracellular purines and pyrimidines have emerged as key regulators of a wide range of physiological and pathophysiological cellular processes acting through P1 and P2 cell surface receptors. Increasing evidence suggests that purinergic receptors can interact with and/or modulate the activity of other classes of receptors and ion channels. This review will focus on the interactions of purinergic receptors with other GPCRs, ion channels, receptor tyrosine kinases, and steroid hormone receptors. Also, the signal transduction pathways regulated by these complexes and their new functional properties are discussed.

Overlapping nongenomic and genomic actions of thyroid hormone and steroids

Nuclear receptors for thyroid hormone and steroids are members of a receptor superfamily with similar molecular organization, but discrete transcriptional functions that define genomic actions of these nonpeptide hormones. Nongenomic actions of thyroid hormone and estrogens and androgens are initiated outside the nucleus, at receptors in the plasma membrane or in cytoplasm; these actions are largely regarded to be unique to the respective hormones. However, there is an increasing number of descriptions of overlapping nongenomic and genomic effects of thyroid hormone and estrogens and testosterone. These effects are concentrated in tumor cells, where, for example, estrogens and thyroid hormone have similar mitogen-activate protein kinase (MAPK)-dependent proliferative actions on ERα-positive human breast cancer cells, and where dihydrotestosterone also can stimulate proliferation. Steroids and thyroid hormone have similar anti-apoptotic effects in certain tumors. But thyroid hormone and steroids also have overlapping or interacting nongenomic and genomic actions in heart and brain cells. These various effects of thyroid hormone and estrogens and androgens are reviewed here and their possible clinical consequences are enumerated.

Role of membrane dynamics processes and exogenous molecules in cellular resveratrol uptake: consequences in bioavailability and activities

In the fields of nutrition prevention and therapy treatment, numerous studies have reported interesting properties of trans-resveratrol (RSV), a natural polyphenol against pathologies such as vascular diseases, cancers, viral infections and neurodegenerative processes. These beneficial effects are supported by more studies showing the pleiotropic actions of RSV. Nevertheless, a crucial question concerning these effects is how the polyphenol, when applied to an organism, gains access to its targets. In this review, we focus on the biochemical and biological parameters involved in RSV transport, particularly the role of the phospholipid bilayer in RSV uptake (passive diffusion, carrier-mediated transport) and of exogenous molecules modulating RSV transport and effects. The dynamic processes of the plasma membrane reveal the importance of the role of lipid composition in the fluidity, the lipid rafts in RSV endocytosis and the ATP-binding cassette transporters in RSV efflux. Specific membrane receptors such as integrin αvβ3 contribute to RSV uptake and to activate signalling pathways involved in apoptosis. We discuss the role of intracellular receptors (i.e. aryl-hydrocarbon and estrogen receptors). In addition, circulating molecules (i.e. albumin, haemoglobin, fatty acids, lipoproteins) play a role as RSV carriers. Finally, we developed a hypothesis concerning the relation between RSV uptake and its biological activities.

Negative regulation of parathyroid hormone-related protein expression by steroid hormones

Elevated parathyroid hormone-related protein (PTHrP) is responsible for humoral hypercalcemia of malignancy (HHM), which is of clinical significance in treatment of terminal patients with malignancies. Steroid hormones were known to cause suppression of PTHrP expression. However, detailed studies linking multiple steroid hormones to PTHrP expression are lacking. Here we studied PTHrP expression in response to steroid hormones in four cell lines with excessive PTHrP production. Our study established that steroid hormones negatively regulate PTHrP expression. Vitamin D receptor, estrogen receptor α, glucocorticoid receptor, and progesterone receptor, were required for repression of PTHrP expression by the cognate ligands. A notable exception was the androgen receptor, which was dispensable for suppression of PTHrP expression in androgen-treated cells. We propose a pathway(s) involving nuclear receptors to suppress PTHrP expression.