Testosterone membrane-initiated action in breast cancer cells: Interaction with the androgen signaling pathway and EPOR

Androgen receptor: Structure, signaling, function and potential drug discovery biomarker in different breast cancer subtypes

The Androgen Receptor (AR) is emerging as an important factor in the pathogenesis of breast cancer (BC), which is the most common malignancy worldwide. >70 % of AR expression in primary and metastatic breast tumors has been observed which suggests that AR may be a new marker and a potential therapeutic target among AR-positive BC patients. Biological insight into AR-positive breast cancer reveals that AR may cross-talk with several vital signaling pathways, including key molecules and receptors. Downstream signaling of AR might also affect many clinically important pathways that are emerging as clinical targets in BC. AR exhibits different behaviors depending on the breast cancer molecular subtype. Preliminary clinical research using AR-targeted drugs, which have already been FDA-approved for prostate cancer (PC), has given promising results for AR-positive breast cancer patients. However, since AR positivity's prognostic and predictive value remains uncertain, it is difficult to identify and stratify patients who would benefit from AR-targeted therapies alone. Thus, the need of the hour is to target the androgen receptor as a monotherapy or in combination with other conventional therapies which has proven to be an effective clinical strategy for the treatment of prostate cancer patients, and these therapeutic strategies are increasingly being investigated in breast cancer. Therefore, in this manuscript, we review the role of AR in various cellular processes that promote tumorigenesis and aggressiveness, in different subtypes of breast cancer, as well as discuss ongoing efforts to target AR for the more effective treatment and prevention of breast cancer.

Androgens Modulate Bcl-2 Agonist of Cell Death (BAD) Expression and Function in Breast Cancer Cells

Androgen receptor (AR) expression in estrogen receptor-positive (ER+) breast cancer (BC) correlates with lower tumor grade and a better clinical outcome. Additionally, in normal mammary epithelium or ER+ BC preclinical models, androgens counteract basal/ER-dependent proliferation. Here, we report an additional mechanism, underlining the protective role exerted by AR. Specifically, the activation of intracellular AR upregulates the Bcl-2-family protein BAD, and TCGA database analyses show that in ER+ BC, BAD expression is associated with better disease-free survival. Ligand-activated AR influences its own and BAD cellular compartmentalization by enhancing levels in the nucleus, as well as in mitochondrial fractions. In both compartments, BAD exerts unconventional functions. In the nucleus, BAD and AR physically interact and, upon androgen stimulation, are recruited at the AP-1 and ARE sites within the cyclin D1 promoter region, contributing to explaining the anti-proliferative effect of androgens in BC cells. Androgens cause an enrichment in BAD and AR content in the mitochondria, correlated with a decrease in mitochondrial function. Thus, we have defined a novel mechanism by which androgens modulate BAD expression, its mitochondria localization, and nuclear content to force its ability to act as a cell cycle inhibitor, strengthening the protective role of androgen signaling in estrogen-responsive BCs.

New Antagonists of the Membrane Androgen Receptor OXER1 from the ZINC Natural Product Database

OXER1 (oxoeicosanoid receptor 1) was deorphanized in 1993 and found to be the specific receptor for the arachidonic acid metabolite 5-oxo-ETE. Recently, we have reported that androgen binds to this receptor also, being a membrane androgen receptor, triggering a number of its membrane-mediated actions (cell migration, apoptosis, cell proliferation, Ca²⁺ movements). In addition, our previous work suggested that a number of natural monomeric and oligomeric polyphenols interact with OXER1, acting similar to testosterone. Here, we interrogated the natural product chemical space and identified nine polyphenolic molecules with interesting in silico pharmacological activities as putative OXER1 antagonists. The molecule with the best pharmacokinetic-pharmacodynamic properties (ZINC15959779) was purchased and tested on OXER1, in prostate cancer cell cultures. It showed that it has actions similar to those of testosterone in inhibiting cAMP, while it had no action in intracellular Ca²⁺ mobilization or actin cytoskeleton rearrangement/migration. These results are discussed under the prism of structure-activity relationships and in silico models of the OXER1 binding groove. We suggest that these compounds, together with the previously reported (poly)phenolic compounds, can be lead structures for the exploration of the anti-inflammatory and antiproliferative effects of OXER1 antagonists.

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.

Targeting the androgen receptor in triple-negative breast cancer: current perspectives

Triple-negative breast cancer (TNBC) is an aggressive subtype associated with frequent recurrence and metastasis. Unlike hormone receptor-positive subtypes, treatment of TNBC is currently limited by the lack of clinically available targeted therapies. Androgen signaling is necessary for normal breast development, and its dysregulation has been implicated in breast tumorigenesis. In recent years, gene expression studies have identified a subset of TNBC that is enriched for androgen receptor (AR) signaling. Interference with androgen signaling in TNBC is promising, and AR-inhibiting drugs have shown antitumorigenic activity in preclinical and proof of concept clinical studies. Recent advances in our understanding of androgenic signaling in TNBC, along with the identification of interacting pathways, are allowing development of the next generation of clinical trials with AR inhibitors. As novel AR-targeting agents are developed and evaluated in clinical trials, it is equally important to establish a robust set of biomarkers for identification of TNBC tumors that are most likely to respond to AR inhibition.

Antagonizing effects of membrane-acting androgens on the eicosanoid receptor OXER1 in prostate cancer

Accumulating evidence during the last decades revealed that androgen can exert membrane initiated actions that involve signaling via specific kinases and the modulation of significant cellular processes, important for prostate cancer cell growth and metastasis. Results of the present work clearly show that androgens can specifically act at the membrane level via the GPCR oxoeicosanoid receptor 1 (OXER1) in prostate cancer cells. In fact, OXER1 expression parallels that of membrane androgen binding in prostate cancer cell lines and tumor specimens, while in silico docking simulation of OXER1 showed that testosterone could bind to OXER1 within the same grove as 5-OxoETE, the natural ligand of OXER1. Interestingly, testosterone antagonizes the effects of 5-oxoETE on specific signaling pathways and rapid effects such as actin cytoskeleton reorganization that ultimately can modulate cell migration and metastasis. These findings verify that membrane-acting androgens exert specific effects through an antagonistic interaction with OXER1. Additionally, this interaction between androgen and OXER1, which is an arachidonic acid metabolite receptor expressed in prostate cancer, provides a novel link between steroid and lipid actions and renders OXER1 as new player in the disease. These findings should be taken into account in the design of novel therapeutic approaches in prostate cancer.

Detection and functional portrayal of a novel class of dihydrotestosterone derived selective progesterone receptor modulators (SPRM)

In early pregnancy, abortion can be induced by blocking the actions of progesterone receptors (PR). However, the PR antagonist, mifepristone (RU38486), is rather unselective in clinical use because it also cross-reacts with other nuclear receptors. Since the ligand-binding domain of human progesterone receptor (hPR) and androgen receptor (hAR) share 54% identity, we hypothesized that derivatives of dihydrotestosterone (DHT), the cognate ligand for hAR, might also regulate the hPR. Compounds designed and synthesized in our laboratory were investigated for their affinities for hPRB, hAR, glucocorticoid receptor (hGRα) and mineralocorticoid receptor (hMR), using whole cell receptor competitive binding assays. Agonistic and antagonistic activities were characterized by reporter assays. Nuclear translocation was monitored using cherry-hPRB and GFP-hAR chimeric receptors. Cytostatic properties and apoptosis were tested on breast cancer cells (MCF7, T-47D). One compound presented a favorable profile with an apparent neutral hPRB antagonistic function, a selective cherry-hPRB nuclear translocation and a cytostatic effect. 3D models of human PR and AR with this ligand were constructed to investigate the molecular basis of selectivity. Our data suggest that these novel DHT-derivatives provide suitable templates for the development of new selective steroidal hPR antagonists.

Erythropoietin and cancer: the unintended consequences of anemia correction

Until 1990, erythropoietin (EPO) was considered to have a single biological purpose and action, the stimulation of red blood cell growth and differentiation. Slowly, scientific and medical opinion evolved, beginning with the discovery of an effect on endothelial cell growth in vitro and the identification of EPO receptors (EPORs) on neuronal cells. We now know that EPO is a pleiotropic growth factor that exhibits an anti-apoptotic action on numerous cells and tissues, including malignant ones. In this article, we present a short discussion of EPO, receptors involved in EPO signal transduction, and their action on non-hematopoietic cells. This is followed by a more detailed presentation of both pre-clinical and clinical data that demonstrate EPO’s action on cancer cells, as well as tumor angiogenesis and lymphangiogenesis. Clinical trials with reported adverse effects of chronic erythropoiesis-stimulating agents (ESAs) treatment as well as clinical studies exploring the prognostic significance of EPO and EPOR expression in cancer patients are reviewed. Finally, we address the use of EPO and other ESAs in cancer patients.

Perturbation of the Hematopoietic Profile by Anabolic Androgenic Steroids

Objective. The aim of this study was to investigate the hematopoietic profile in AAS abusers, during or short after their last abuse and approximately six months later. Moreover, we studied if supraphysiological doses of testosterone influence the concentration of hemoglobin and erythropoietin in healthy volunteers. Design and Methods. Subjects (N=31) were recruited through an antidoping hotline. The hematological profile was measured when the subjects entered the study and approximately 6 months later. Testosterone enanthate (500 mg) was administered to healthy volunteers (N=24). Gene expression was studied in human hek293 cells exposed to 1 μM testosterone. Results. Decreased levels of hemoglobin, erythrocyte volume fraction, and erythrocyte counts were observed after 6 months without the use of AAS. Results in volunteers show that hemoglobin increased 3% four and 15 days after testosterone administration, whereas EPO was significantly increased by 38% four days after dose. Agreeingly, in vitro study shows that testosterone induces the mRNA level of EPO with 65% after 24-hour exposure. Conclusion. These results indicate that supraphysiological doses of testosterone may cause a perturbation in the hematopoietic profile. This is of interest in relation to the adverse cardiovascular effects observed in AAS abusers.

Targeting membrane androgen receptors in tumors

INTRODUCTION

In the last decade androgen actions that are originated from non-genomic, rapid signaling have been described in a large number of cell models and tissues. These effects are initiated through the stimulation of membrane androgen-binding sites or receptors (mAR). Although the molecular identity of mARs remains elusive, their activation is known to trigger multiple non-genomic signaling cascades and to regulate numerous cell responses. In recent years specific interest is being paid to the role of mARs in tumors. Specifically, it was demonstrated that mAR activation by non-permeable testosterone conjugates induced potent anti-tumorigenic responses in prostate, breast, colon and glial tumors. In addition, in vivo animal studies further emphasized the potential clinical importance of these receptors.

AREAS COVERED

This review will summarize the current knowledge on the mAR-induced non-genomic, rapid androgen actions. It will focus on the molecular signaling pathways governed by mAR activation, discuss latest attempts to elucidate the molecular identity of mAR, address the plethora of cell responses initiated by mAR and evaluate the potential role of mAR and mAR-specific signaling as possible therapeutic targets in tumors.

EXPERT OPINION

mAR and mAR-induced specific signaling may represent novel therapeutic targets in tumors through the development of specific testosterone analogs.

Whole transcriptome analysis of the ERα synthetic fragment P295-T311 (ERα17p) identifies specific ERα-isoform (ERα, ERα36)-dependent and -independent actions in breast cancer cells

ERα17p is a peptide corresponding to the sequence P295LMIKRSKKNSLALSLT311 of the estrogen receptor alpha (ERα) and initially found to interfere with ERα-related calmodulin binding. ERα17p was subsequently found to elicit estrogenic responses in E2-deprived ERα-positive breast cancer cells, increasing proliferation and ERE-dependent gene transcription. Surprisingly, in E2-supplemented media, ERα17p-induced apoptosis and modified the actin network, influencing cell motility. Here, we report that ERα17p internalizes in breast cancer cells (T47D, MDA-MB-231, SKBR3) and induces a massive early (3 h) transcriptional activity. Remarkably, about 75% of significantly modified transcripts were also modified by E2, confirming the pro-estrogenic profile of ERα17p. The different ER spectra of the used cell lines allowed us to identify a specific ERα17p signature related to ERα as well as its variant ERα36. With respect to ERα, the peptide activates nuclear (cell cycle, cell proliferation, nucleic acid and protein synthesis) and extranuclear signaling pathways. In contrast, through ERα36, it mainly triggers inhibitory actions on inflammation. This is the first work reporting a detailed ERα36-specific transcriptional signature. In addition, we report that ERα17p-induced transcripts related to apoptosis and actin modifying effects of the peptide are independent from its estrogen receptor(s)-related actions. We discuss our findings in view of the potential use of ERα17p as a selective peptidomimetic estrogen receptor modulator (PERM).

Correlation between erythropoietin receptor(s) and estrogen and progesterone receptor expression in different breast cancer cell lines

Erythropoietin (EPO) receptor (EPOR) expression in breast cancer has been shown to correlate with the expression of estrogen receptor (ESR) and progesterone receptor (PGR) and to be associated with the response to tamoxifen in ESR+/PGR+ tumors but not in ESR- tumors. In addition, the correlation between EPOR and G protein-coupled estrogen receptor 1 [GPER; also known as G protein-coupled receptor 30 (GPR30)] has been reported, suggesting the prognostic potential of EPOR expression. Moreover, the involvement of colony stimulating factor 2 receptor, β, low‑affinity (CSF2RB) and ephrin type-B receptor 4 (EPHB4) as EPOR potential receptor partners in cancer has been indicated. This study analyzed the correlation between the expression of genes for EPO, EPOR, CSF2RB, EPHB4, ESR, PGR and GPER in the MCF-7, MDA-MB-361, T-47D, MDA-MB-231, Hs578Bst, SKBR3, MCF-10A and Hs578T cell lines. The cell lines were also treated with recombinant human EPO (rHuEPO) in order to determine its ability to activate the Jak/STAT5, MAPK and PI3K signaling pathways and modify cell growth characteristics. Expression analysis stratified the cell lines in 2 main clusters, hormone-dependent cell lines expressing ESR and PGR and a hormone-independent cluster. A significant correlation was observed between the expression levels of ESR and PGR and their expression was also associated with that of GPER. Furthermore, the expression of GPER was associated with that of EPOR, suggesting the connection between this orphan G protein and EPO signaling. A negative correlation between EPOR and CSF2RB expression was observed, questioning the involvement of these two receptors in the hetero-receptor formation. rHuEPO treatment only influenced the hormone-independent cell lines, since only the MDA-MB-231, SKBR3 and Hs578T cells responded to the treatment. The correlation between the expression of the analyzed receptors suggests that the receptors may interact in order to activate signaling pathways or to evade their inhibition. Therefore, breast cancer classification upon ESR, PGR and human epidermal growth factor receptor 2 (HER2) may not be sufficient for the selection of suitable treatment protocol. The expression of EPOR, GPER and EPHB4 may be considered as additional classification factors.

Immunohistochemical study of pElk-1 expression in human breast cancer: association with breast cancer biologic profile and clinicopathologic features

BACKGROUND

Recently an increased interest on Elk1 protein and its role in breast cancer evolution has been noted. This protein is an element of the Ets family of transcription factors and it has been involved in a number of important cell processes through the activation of different genes, in a number of normal tissues as well as in many malignancies.

METHODS

One hundred and seventy (n = 170) cases of operable breast cancer (invasive ductal, lobular and mixed type breast carcinomas) were randomly selected and investigated for the expression of pElk-1, Ki-67 and Cyclin D1 using immunohistochemistry. Our findings were correlated with tumors' clinicopathologic data and biologic profile.

RESULTS

Activated Elk1 is positively associated with ER (p-value: 0.018) and also shows a positive association of with Cyclin D1 (p-value: <0.001). No relationship was noted between pElk1 and Ki67 (p-value: 0.213). Luminal A and B Her-2 negative breast cancer subtypes were showing greater pElk-1 immunoreactivity compared to Her-2 and Basal breast cancer subtypes, and also a higher staining intensity. No association of the molecule with other clinicopathologic characteristics (tumor size, stage, histological type or lymph node metastases) or disease adverse events (local recurrence, metastasis or death) was evidenced.

CONCLUSIONS

Our findings offer a new perspective for the role of pElk-1 in breast neoplasia suggesting a direct relation of this molecule to tumor biology and a putative target of personalized breast cancer therapies, although its prognostic/discriminant role is not supported.

Is the haematopoietic effect of testosterone mediated by erythropoietin? The results of a clinical trial in older men

The stimulatory effects of testosterone on erythropoiesis are very well known, but the mechanisms underlying the erythropoietic action of testosterone are still poorly understood, although erythropoietin has long been considered a potential mediator. A total of 108 healthy men >65 years old with serum testosterone concentration <475 ng/dL were recruited by direct mailings to alumni of the University of Pennsylvania and Temple University, and randomized to receive a 60-cm(2) testosterone or placebo patch for 36 months. Ninety-six subjects completed the trial. We used information and stored serum specimens from this trial to test the hypothesis that increasing testosterone increases haemoglobin by stimulating erythropoietin production. We used information of 67 men, 43 in the testosterone group and 24 in the placebo group who had banked specimens available for assays of testosterone, haemoglobin and erythropoietin at baseline and after 36 months. The original randomized clinical study was primarily designed to verify the effects of testosterone on bone mineral density. The primary outcome of this report was to investigate whether or not transdermal testosterone increases haemoglobin by increasing erythropoietin levels. The mean age ± SD of the 67 subjects at baseline was 71.8 ± 4.9 years. Testosterone replacement therapy for 36 months, as compared with placebo, induced a significant increase in haemoglobin (0.86 ± 0.31 g/dL, p = 0.01), but no change in erythropoietin levels (-0.24 ± 2.16 mIU/mL, p = 0.91). Included time-varying measure of erythropoietin did not significantly account for the effect of testosterone on haemoglobin (Treatment-by-time: β = 0.93, SE = 0.33, p = 0.01). No serious adverse effect was observed. Transdermal testosterone treatment of older men for 36 months significantly increased haemoglobin, but not erythropoietin levels. The haematopoietic effect of testosterone does not appear to be mediated by stimulation of erythropoietin production.

ERα36, a new variant of the ERα is expressed in triple negative breast carcinomas and has a specific transcriptomic signature in breast cancer cell lines

Triple negative breast cancer is deprived of estrogen receptor alpha (ERα), progesterone receptor (PR) and HER-2 protein. It constitutes the most heterogeneous and aggressive group of breast carcinomas, for which identification of novel characteristics and characterization of putative targets becomes very demanding. In the present work we have assayed the expression of ERα36, a recently identified ERα variant of 36kDa, in a series of triple negative breast cancers, in relation to the clinical behavior and other clinico-pathological features of the tumors. While widely expressed within the cytoplasm in almost all tumors, we found that exclusively the membrane/submembrane expression of the receptor exhibits a correlation with patient's survival. Moreover, membrane ERα36 correlates in an inverse manner with the expression of miRNA210, a pro-angiogenic miR, with high prognostic relevance in triple negative carcinomas. A thorough transcriptomic, pharmacological-based approach in breast cancer cell lines, revealed an early (direct) transcriptional signature of the receptor activation, related to immune system processes and T-cell differentiation, RNA biosynthesis, regulation of metabolism, VEGF signaling and regulation of the cell cycle, with a down-regulation of CREB, NFκB and STATs transcription factors. Finally, ERα36 expression is not limited within breast cancer epithelial linen, but is equally identified in tumor vasculature, peritumoral fat tissue, lymphocytic infiltrate and stromal fibroblasts. In light of the above, ERα36 could represent a major counterpart in triple negative breast cancer.

Early membrane initiated transcriptional effects of estrogens in breast cancer cells: First pharmacological evidence for a novel membrane estrogen receptor element (ERx)

The complexity of estrogen actions mainly relies to the presence of different identified receptors (ERα, ERβ, their isoforms, and GPR30/GPER) and their discrete cellular distribution. Depending on the localization of the receptor that mediates estrogen effects, nuclear and extra-nuclear actions have been described. The latter can trigger a number of signaling events leading also to transcriptional modifications. In an attempt to clarify the nature of the receptor(s) involved in the membrane initiated effect of estrogens on gene expression, we performed a whole transcriptome analysis of breast cancer cell lines with different receptor profiles (T47D, MCF7, MDA-MB-231, SK-BR-3). A pharmacological approach was conducted with the use of estradiol (E(2)) or membrane-impermeable E(2)-BSA in the absence or presence of a specific ERα-β or GPR30/GPER antagonist. Our results clearly show that in addition to the ERα isoforms and/or GPR30/GPER that mainly mediate the transcriptional effect of E(2)-BSA, there is a specific transcriptional signature (found in T47D and MCF-7 cells) suggesting the presence of an unidentified membrane ER element (ERx). Analysis of its signature and phenotypic verification revealed that important cell function such as apoptosis, transcriptional regulation, and growth factor signaling are associated with ERx.

Interplay of estrogen receptors and GPR30 for the regulation of early membrane initiated transcriptional effects: A pharmacological approach

Estrogens exert their effect through ERα and ERβ intracellular transcription factors and rapid, usually membrane-initiated receptors, influencing cytosolic signaling and transcription. The nature of extranuclear estrogen elements has not been elucidated so far; classical or alternatively transcribed ER isoforms (ERα36, ERα46) anchored to the plasma membrane and GPR30 (GPER1) have been reported to exert early estrogen actions. Here, we used E2-BSA, an impermeable estradiol analog for a transcriptome analysis in four GREP1 positive breast cancer cell lines with different estrogen receptor profiles (T47D, MCF-7, MDA-MB-231 and SKBR3) in order to evaluate GPER1 transcriptional effects. Early effects of E2-BSA were assayed after 3h of incubation, in the absence/presence of ICI182,780 (ER-inhibitor) or G15 (GREP1-specific inhibitor). E2-BSA specifically modified 277-549 transcripts in the different cell lines. Two different clusters of transcripts could be identified: (1) the majority of transcripts were inhibited by both ICI182,780 and G15, suggesting an interaction of E2-BSA with a common ER-related element, or a direct ER-GPER1 interaction; (2) a small number of G15-only modified transcripts, in two cell lines (T47D and SKBR3 cells), indicative of specific GPER1-related effects. The latter transcripts were significantly related to pathways including FOXA2/FOXA3 transcription factor networks, RNA-Polymerases Transcription Regulation and lipid metabolism, while ICI/G15 inhibited transcripts affected pathways related to apoptosis, erythropoietin signaling, metabolic effects through the citric acid cycle, IL-4 and IL-5 mediated events and homologous DNA recombination. Finally, we review the current literature of GPER1 actions, in view of our results of ER-dependent and independent GPER1-modified pathways.

Contrasting effect of recombinant human erythropoietin on breast cancer cell response to cisplatin induced cytotoxicity

Background

Human recombinant erythropoietin (rHuEpo) that is used for the treatment of the chemotherapy-induced anaemia in cancer patients was shown to cause detrimental effects on the course of disease due to increased adverse events inflicting patient’s survival, potentially related to rHuEpo-induced cancer progression. In this study, we elucidate the effect of rHuEpo administration on breast cancer cell proliferation and gene expression after cisplatin (cDDP) induced cytotoxicity.

Materials and methods

Two breast carcinoma models, MCF-7 and MDA-MB-231 cell lines, were used differing in oestrogen (ER) and progesterone (PR) receptors and p53 status. Cells were cultured with or without rHuEpo for 24 h or 9 weeks and their growth characteristics after cDDP treatment were assessed together with expression of genes involved in the p53-signaling pathway.

Results

Short-term exposure of breast cancer cells to rHuEpo lowers their proliferation and reduces cDDP cytotoxic potency. In contrast, long-term exposure of MCF-7 cells to rHuEpo increases proliferation and predisposes MCF-7 cells to cDDP cytotoxicity, but has no effect on MDA-MB-231 cells. MDA-MB-231 cells show altered level of ERK phosphorylation, indicating involvement of MAPK signalling pathway. Gene expression analysis of p53-dependent genes and bcl-2 gene family members confirmed differences between long and short-term rHuEpo effects, indicating the most prominent changes in BCL2 and BAD expression.

Conclusions

Proliferation and survival characteristics of MCF-7 cells are reversely modulated by the length of the rHuEpo exposure. On the other hand, MDA-MB-231 cells are almost irresponsive to long-term rHuEpo, supposedly due to the mutated p53 and ER(+)/PR(−) status. The p53 and ER/PR status may predict tumour response on rHuEpo and cDDP treatment.

Novel oligomeric proanthocyanidin derivatives interact with membrane androgen sites and induce regression of hormone-independent prostate cancer

Prostate cancer is the most common malignancy among men in Western societies, and current therapeutic approaches are evolving to manage growth, recurrence, and mortality neoplasia. Membrane androgen receptors (mARs) have been characterized in human prostate cancer, being preferentially expressed in tumor rather than benign gland areas. Furthermore, mAR agonists (protein-conjugated testosterone) decrease in vitro prostate cancer cell growth and induce apoptosis, whereas in vivo they regress growth of tumor xenografts alone or in combination with taxane drugs. In this respect, targeting mARs might be a novel therapeutic approach in prostate cancer. In our search for new small-molecule ligands of mAR, we report that flavanol dimers B1-B4 (oligomeric procyanidins) decrease in vitro growth of the androgen-sensitive (LnCaP) and androgen-resistant (DU145) human prostate cancer cell lines in the following order: B3 = B4 > B2 ≫ B1 (LnCaP) and B2 ≫ B3 = B4 ≫ B1 (DU145). Some of these analogs were previously shown to trigger signaling cascades similar to testosterone-bovine serum albumin (BSA) conjugate. Galloylation does not confer an additional advantage; however, oleylation increases the dimers' antiproliferative potency by a factor of 100. In addition, we report that B2, oleylated or not, displaces testosterone from mARs with an IC(50) value at the nanomolar range and induces DU145 tumor xenograft regression by 50% (testosterone-BSA 40%). In this respect, oleylated B2 is a potent small-molecule agonist of mAR and could be a novel therapeutic agent for advanced prostate cancer, especially when taking into account the absence of androgenic actions and (liver) toxicity.

Testosterone membrane-initiated action in breast cancer cells: Interaction with the androgen signaling pathway and EPOR

Membrane-initiated androgen actions have now been acknowledged, even though a specific binding site has not been biochemically characterized yet. Recent data indicate that testosterone-BSA, a non-permeable testosterone analog, can exert specific actions in breast cancer cell lines, including proper transcriptional effects, independent of the intracellular androgen sites. In the present work we explore the effects of testosterone-BSA in two specifically modified pathways, revealed by early trascriptome analysis, namely the non-genotropic androgen signaling and the HIF1alpha pathway. We provide evidence that p38 MAPK and PI3K/Akt/NFkappaB and/or Rho/Actin pathways are directly involved in testosterone-induced apoptosis, while the JNK/c-JUN pathway is involved in membrane site-initiated transcription. Furthermore we show that membrane-acting androgens modify the transcription of the erythropoietin receptor (EPOR), leading to erythropoietin-initiated actions. Interestingly, association of recombinant human erythropoietin (rHuEPO) together with testosterone-BSA protects cells from apoptosis, through discrete signaling events. The effect of testosterone-BSA is exerted through the classical erythropoietin promoter, while rHuEPO decreases the transcription of EPOR acting on a newly identified regulatory/promoter region, upstream of its known promoter. These results suggest a new interaction of membrane-acting androgen with EPOR and should be taken into account in the pharmaceutical manipulations of breast cancer patients.