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A major challenge in clinical management of prostate cancer (PC) is to limit tumor growth and prevent metastatic spreading. Considerable efforts have been made to discover new compounds for PC therapy and recent years have seen promising progress in this field. Pharmacological approaches have been designed to achieve benefits in PC treatment and avoid the negative side effects resulting from administration of antagonists or agonists or new drugs. Nonetheless, the currently available therapies frequently induce resistance and PC progresses toward castration-resistant forms that can be caused by the androgen receptor reactivation and/or mutations, or derangement of signaling pathways. Preclinical and clinical findings have also shown that other nuclear receptors are frequently altered in PC. In this review, we focus on the role of estradiol/estradiol receptor (ER) axis, which controls PC growth and progression. Selective targeting of ER subtypes (α or β) may be an attractive way to limit the growth and spreading of prostatic cancer cells.

Nerve growth factor (NGF) is abundantly secreted by prostate cancer (PC) cells and However, the mechanism by which NGF signalling impinges on PC progression is still debated. In this report, we show that androgens and NGF both induce a reciprocal cross-talk between androgen receptor (AR) and tyrosine receptor kinase A (TrkA) in PC-derived LNCaP cells. The findings here collected point to the key role of this complex in promoting proliferation and motility of LNCaP cells upon challenging with androgens or NGF. Results obtained using the anti-androgen bicalutamide or GW441756, a specific inhibitor of TrkA, are in line with the idea that AR/TrkA cross-talk, now identified for the first time in PC cells, provides a rationale for interfering in PC progression through the use of combinatorial therapies, such as anti-androgens plus inhibitors of NGF receptor. Since androgen- or NGF-induced cell migration requires AR/filamin A association in various cell types, we also used the RH2025u stapled peptide, which specifically interrupts AR/filamin A complex assembly. At nanomolar concentration, the peptide inhibits LNCaP cell migration triggered by androgens or NGF, indicating that AR/filamin A complex is also utilized by NGF/TrkA axis to transmit motility signalling. In conclusion, we here report a novel link between extranuclear AR functions and PC progression, which relies on the receptor’s ability to intersect important signalling effectors or scaffolds, such as the NGF receptor or filamin A. In this context, the use of combinatorial therapies or new compounds selectively interfering in extranuclear AR functions might be envisaged when PC fails to respond to AR antagonists or tyrosine kinase inhibitors, commonly employed as single drugs in PC therapy.

Prostate cancer is one of the most commonly diagnosed cancers in men, and androgen deprivation therapy still represents the primary treatment for prostate cancer patients. This approach, however, frequently fails and patients develop castration-resistant prostate cancer, which is almost untreatable. Cancer cells are characterized by a hierarchical organization, and stem/progenitor cells are endowed with tumor-initiating activity. Accumulating evidence indicates that prostate cancer stem cells lack the androgen receptor and are, indeed, resistant to androgen deprivation therapy. In contrast, these cells express classical (α and/or ß) and novel (GPR30) estrogen receptors, which may represent new putative targets in prostate cancer treatment. In the present review, we discuss the still-debated mechanisms, both genomic and non-genomic, by which androgen and estradiol receptors (classical and novel) mediate the hormonal control of prostate cell stemness, transformation, and the continued growth of prostate cancer. Recent preclinical and clinical findings obtained using new androgen receptor antagonists, anti-estrogens, or compounds such as enhancers of androgen receptor degradation and peptides inhibiting non-genomic androgen functions are also presented. These new drugs will likely lead to significant advances in prostate cancer therapy.

Androgens stimulate neuronal differentiation of PC12 cells by nontranscriptional action of the endogenous androgen receptor (AR). AR is also required for NGF-induced neuritogenesis of PC12. Androgens or NGF trigger AR association with filamin and TrkA, TrkA interaction with PI3-K δ, and activation of PI3-K δ and Rac., Steroids and growth factors control neuronal development through their receptors under physiological and pathological conditions. We show that PC12 cells harbor endogenous androgen receptor (AR), whose inhibition or silencing strongly interferes with neuritogenesis stimulated by the nonaromatizable synthetic androgen R1881 or NGF. This implies a role for AR not only in androgen signaling, but also in NGF signaling. In turn, a pharmacological TrkA inhibitor interferes with NGF- or androgen-induced neuritogenesis. In addition, androgen or NGF triggers AR association with TrkA, TrkA interaction with PI3-K δ, and downstream activation of PI3-K δ and Rac in PC12 cells. Once associated with AR, filamin A (FlnA) contributes to androgen or NGF neuritogenesis, likely through its interaction with signaling effectors, such as Rac. This study thus identifies a previously unrecognized reciprocal cross-talk between AR and TrkA, which is controlled by β1 integrin. The contribution of FlnA/AR complex and PI3-K δ to neuronal differentiation by androgens and NGF is also novel. This is the first description of AR function in PC12 cells.

Bisphenol A (BPA) belongs to the class of chemicals known as endocrine disruptors and has been also involved in the pathogenesis and progression of endocrine related cancer such as breast and prostate cancers. Here, we have investigated the effect of BPA in human prostate cancer LNCaP cells and in human non-transformed epithelial prostate EPN cells. Our data showed that BPA induces the down regulation of cyclin D1 expression and the upregulation of the cell cycle inhibitors p21 and p27, leading to cell cycle arrest. Interestingly, we found that the BPA anti-proliferative response depends on a strong and rapid activation of epidermal growth factor receptor (EGFR), which stimulates ERK-dependent pathway. This, in turn, induces expression of p53 and its phosphorylation on residue Ser15, which is responsible for cell cycle arrest. EGFR activation occurs upon a cross talk with androgen (AR) and estradiol receptor-β (ERβ) which are known to bind BPA. Altogether, these findings show a novel signaling pathway in which EGFR activation plays a key role on BPA-induced cell cycle inhibition through a pathway involving AR and ERβ/EGFR complexes, ERK and p53. Our results provide new insights for understanding the molecular mechanisms in human prostate cancer. On the other, they could allow the development of new compounds that may be used to overcome human prostate cancer resistance to endocrine therapy in promising target therapeutic approaches.

Endocrine disrupting chemicals (EDCs) are man-made substances widespread in the environment that include, among many others, bisphenol A (BPA), organochlorinated pesticides and hormone derivatives detectable in meat from animals raised in concentrated animal feeding operations. Increasing evidence indicates that EDCs have a negative impact on human health as well as on male and female fertility. They may also be associated with some endocrine diseases and increased incidence of breast and prostate cancer. This review aims to summarize available data on the (potential) impact of some common EDCs, focusing particularly on BPA, prostate cancer and their mechanisms of action. These compounds interfere with normal hormone signal pathway transduction, resulting in prolonged exposure of receptors to stimuli or interference with cellular hormone signaling in target cells. Understanding the effects of BPA and other EDCs as well as their molecular mechanism(s) may be useful in sensitizing the scientific community and the manufacturing industry to the importance of finding alternatives to their indiscriminate use.

Resistance to hormone therapy and disease progression is the major challenge in clinical management of prostate cancer (PC). Drugs currently used in PC therapy initially show a potent antitumor effects, but PC gradually develops resistance, relapses and spreads. Most patients who fail primary therapy and have recurrences eventually develop castration-resistant prostate cancer (CRPC), which is almost incurable. The nerve growth factor (NGF) acts on a variety of non-neuronal cells by activating the NGF tyrosine-kinase receptor, tropomyosin receptor kinase A (TrkA). NGF signaling is deregulated in PC. In androgen-dependent PC cells, TrkA mediates the proliferative action of NGF through its crosstalk with the androgen receptor (AR). Epithelial PC cells, however, acquire the ability to express NGF and TrkA, as the disease progresses, indicating a role for NGF/TrkA axis in PC progression and androgen-resistance. We here report that once activated by NGF, TrkA mediates proliferation, invasiveness and epithelial-mesenchymal transition (EMT) in various CRPC cells. NGF promotes organoid growth in 3D models of CRPC cells, and specific inhibition of TrkA impairs all these responses. Thus TrkA represents a new biomarker to target in CRPC.

Prostate cancer (PC) represents the most common type of cancer among males and is the second leading cause of cancer death in men in Western society. Current options for PC therapy remain unsatisfactory, since they often produce uncomfortable long-term side effects, such as impotence (70%) and incontinence (5–20%) even in the first stages of the disease. Light-triggered therapies, such as photodynamic therapy, have the potential to provide important advances in the treatment of localized and partially metastasized prostate cancer. We have designed a novel molecular conjugate (DR2) constituted of a photosensitizer (pheophorbide a, Pba), connected to a nonsteroidal anti-androgen molecule through a small pegylated linker. This study aims at investigating whether DR2 represents a valuable approach for PC treatment based on light-induced production of single oxygen and nitric oxide (NO) in vitro. Besides being able to efficiently bind the androgen receptor (AR), the 2-trifluoromethylnitrobenzene ring on the DR2 backbone is able to release cytotoxic NO under the exclusive control of light, thus augmenting the general photodynamic effect. Although DR2 is similarly internalized in cells expressing different levels of androgen receptor, the AR ligand prevents its efflux through the ABCG2-pump. In vitro phototoxicity experiments demonstrated the ability of DR2 to kill cancer cells more efficiently than Pba, while no dark toxicity was observed. Overall, the presented approach is very promising for further development of AR-photosensitizer conjugates in the multimodal photodynamic treatment of prostate cancer.

The androgen receptor (AR) mediates differentiation, proliferation and transformation of target tissues. These processes require a crosstalk between epithelial and stromal cells. Prostate cancer (PCa) represents a major cause of cancer-related mortality in men, and is often associated with deregulation of androgen/AR axis. Clinical and molecular findings have highlighted the role of epithelial AR in PCa progression. In contrast, the functions of AR in mesenchymal cells are still unclear. We previously reported that low androgen concentration (1 pM) triggers interaction of AR with the Src tyrosine kinase and PI3-K, thus driving cell cycle progression in fibroblasts. In contrast, stimulation of fibroblasts and fibrosarcoma cells with physiological (10 nM) androgen concentration leads to interaction of AR with full-length filamin A (FLNa) and does not trigger DNA synthesis. On the basis of these findings, we re-examined the role of androgen/AR axis in fibroblasts and human fibrosarcoma HT1080 cells. Recently, we obtained two original and integrated findings on the decision of mesenchymal cells to undergo reversible quiescence and migrate upon stimulation with 10 nM androgens (Castoria et al. 2011 and 2014). This decision is dependent upon the interaction of AR with FLNa. Once assembled, the bipartite AR/FLNa complex recruits a1-integrin and triggers Rac1 activation, thereby enhancing on the one hand cell motility. On the other, Rac 1 activation triggers its downstream effector DYRK 1B, which phosphorylates Ser10 of p27. Stabilization of p27 and cell quiescence then follow. These results strengthen and extend our studies, adding a new and exciting piece to the complex puzzle of signaling networks activated by androgens in target cells. Our findings might have implications for current approaches to AR-related diseases.

Prostate cancer is the major cause of cancer-related death among the male population of Western society, and androgen deprivation therapy represents the first line in prostate cancer treatment. However, although androgen receptor expression is maintained throughout the various stages of prostate cancer, androgen deprivation therapy frequently fails. Clinical studies have demonstrated that different androgen/androgen receptor signalling pathways operate in target tissues. Androgen receptor stimulates growth and transformation of target cells, but under certain conditions slows down their proliferation. In this review we discuss the role of androgen receptor in controlling different functions of mesenchymal and transformed mesenchymal cells. Findings here presented support the role of androgen receptor in suppressing proliferation and stimulating migration of stromal cells, with implications for current approaches to cancer therapy.

The androgen receptor (AR), a ligand-regulated nuclear transcription factor, mediates differentiation and proliferation of target tissues. Its action is frequently associated with human proliferative diseases, mainly the prostate cancer. We have recently analyzed in mouse embryo NIH3T3 fibroblasts and human fibrosarcoma HT1080 cells the molecular basis and the biological role of AR interaction with the full-length filamin A (FLNa), an actin-cross-linking protein. Here, we describe a procedure revealing the AR/FLNa complex in stromal cells. Upon physiological (10 nM) androgen stimulation of quiescent NIH3T3 cells, FLNa co-immunoprecipitates with AR and co-localizes with the receptor at intermediate actin filaments. The AR/FLNa complex specifically regulates AR extranuclear functions leading to Rac1 activation and consequent cell motility. This complex adds a new and unexpected piece to the growing evidence of the role of signalling effectors, scaffolds, and cytoskeletal proteins in the rapid androgen action and in progression of hormone-dependent cancers.

The androgen receptor (AR), a ligand-regulated nuclear transcription factor, mediates differentiation and proliferation of target tissues. Its action is frequently associated with human proliferative diseases, mainly the prostate cancer. We have recently analyzed in mouse embryo NIH3T3 fibroblasts and human fibrosarcoma HT1080 cells the molecular basis and the biological role of AR interaction with the full-length filamin A (FLNa), an actin-cross-linking protein. Here, we describe a procedure revealing the AR/FLNa complex in stromal cells. Upon physiological (10 nM) androgen stimulation of quiescent NIH3T3 cells, FLNa co-immunoprecipitates with AR and co-localizes with the receptor at intermediate actin filaments. The AR/FLNa complex specifically regulates AR extranuclear functions leading to Rac1 activation and consequent cell motility. This complex adds a new and unexpected piece to the growing evidence of the role of signalling effectors, scaffolds, and cytoskeletal proteins in the rapid androgen action and in progression of hormone-dependent cancers.

The androgen receptor (AR) represents the primary target for prostate cancer (PC) treatment even when the disease progresses toward androgen-independent (AIPC) or castration-resistant (CRPC) forms. Because small chemical changes in the structure of nonsteroidal AR ligands determine the pharmacological responses of AR, we developed a novel stereoselective synthetic strategy that allows sterically hindered C2-substituted bicalutamide analogues to be obtained. Biological and theoretical evaluations demonstrate that C2-substitution with benzyl and phenyl moieties is a new, valuable option toward improving pan-antagonist behavior. Among the synthesized compounds, (R)-16m, when compared to casodex, (R)-bicalutamide, and enzalutamide, displayed very promising in vitro activity toward five different prostate cancer cell lines, all representative of CPRC and AIPC typical mutations. Despite being less active than (R)-bicalutamide, (R)-16m also displayed marked in vivo antitumor activity on VCaP xenografts and thus it may serve as starting point for developing novel AR pan-antagonists.

Background Hormones and growth factors influence the proliferation and invasiveness of human mesenchymal tumors. The highly aggressive human fibrosarcoma HT1080 cell line harbors classical androgen receptor (AR) that responds to androgens triggering cell migration in the absence of significant mitogenesis. As occurs in many human cancer cells, HT1080 cells also express epidermal growth factor receptor (EGFR). Experimental Findings: We report that the pure anti-androgen Casodex inhibits the growth of HT1080 cell xenografts in immune-depressed mice, revealing a novel role of AR in fibrosarcoma progression. In HT1080 cultured cells EGF, but not androgens, robustly increases DNA synthesis. Casodex abolishes the EGF mitogenic effect, implying a crosstalk between EGFR and AR. The mechanism underlying this crosstalk has been analyzed using an AR-derived small peptide, S1, which prevents AR/Src tyrosine kinase association and androgen-dependent Src activation. Present findings show that in HT1080 cells EGF induces AR/Src Association, and the S1 peptide abolishes both the assembly of this complex and Src activation. The S1 peptide inhibits EGF-stimulated DNA synthesis, cell matrix metalloproteinase-9 (MMP-9) secretion and invasiveness of HT1080 cells. Both Casodex and S1 peptide also prevent DNA synthesis and migration triggered by EGF in various human cancer-derived cells (prostate, breast, colon and pancreas) that express AR. Conclusion This study shows that targeting the AR domain involved in AR/Src association impairs EGF signaling in human fibrosarcoma HT1080 cells. The EGF-elicited processes inhibited by the peptide (DNA synthesis, MMP-9 secretion and invasiveness) cooperate in increasing the aggressive phenotype of HT1080 cells. Therefore, AR represents a new potential therapeutic target in human fibrosarcoma, as supported by Casodex inhibition of HT1080 cell xenografts. The extension of these findings in various human cancer-derived cell lines highlights the conservation of this process across divergent cancer cells and identifies new potential targets in the therapeutic approach to human cancers.

"The management of hormone-refractory prostate cancer represents a major challenge in the therapy of this tumor, and identification of novel androgen receptor antagonists is needed to render treatment more effective. We analyzed the activity of two novel androgen receptor antagonists, (S)-11 and (R)-9, in in vitro and in vivo experimental models of hormone-sensitive or castration-resistant prostate cancer (CRPC). In vitro experiments were performed on LNCaP, LNCaP-AR, LNCaP-Rbic and VCaP human prostate cancer cells. Cytotoxic activity was assessed by SRB and BrdU uptake, AR transactivation by luciferase reporter assay and PSA levels by Real Time RT-PCR and ELISA assays. Cell cycle progression-related markers were evaluated by western blot. In vivo experiments were performed on SCID mice xenografted with cells with different sensitivity to hormonal treatment. In hormone-sensitive LNCaP and LNCaP-AR cells, the latter expressing high androgen receptor levels, (R)-9 and (S)-11 exhibited a higher cytotoxic effect compared to that of the reference compound ((R)-bicalutamide), also in the presence of the synthetic androgen R1881. Furthermore, the cytotoxic effect produced by (R)-9 was higher than that of (S)-11 in the two hormone-resistant LNCaP-AR and VCaP cells. A significant reduction in PSA levels was observed after exposure to both molecules. Moreover, (S)-11 and (R)-9 inhibited DNA synthesis by blocking the androgen-induced increase in cyclin D1 protein levels. In vivo studies on the toxicological profile of (R)-9 did not reveal the presence of adverse events. Furthermore, (R)-9 inhibited tumor growth in various in vivo models, especially LNCaP-Rbic xenografts, representative of recurrent disease. Our in vitro results highlight the antitumor activity of the two novel molecules (R)-9 and (S)-11, making them a potentially attractive option for the treatment of CRPC.. . "

In this chapter we aim to draw the attention of potential readers to several aspects of our research on non-genomic action of sex steroid hormones that have not as yet been fully investigated and might offer interesting developments in future studies. The first aspect concerns the dependence of phenotype on hormone concentration. The second, regards the analysis of mechanisms responsible for the simultaneous stimulation of cell migration and inhibition of proliferation. Besides its physiological relevance, the migration-proliferation dichotomy might also be involved in the intermediate stages of progression from hormone dependency to hormone independency in breast and prostate cancers. Thirdly, the increasing number of non-reproductive cells that respond to steroid hormones through receptor-mediated non-genomic action in the absence of receptor-dependent transcription challenges the classic model of steroid hormone action as restricted to classic cell types rather than valid for all steroid target cells. Cross talk between membrane receptors and nuclear steroid receptors regulates nuclear steroid receptor action. An additional cross talk occurring between membrane receptors and extra-nuclear steroid receptors modulates to a great extent the intensity of growth factor signaling. The observed convergence of steroid-stimulated steroid receptor heterodimers on signaling pathways enhances signaling and offers new flexibility in the use of steroid antagonists. Surprisingly, steroid receptor nuclear export is a crucial step in the proliferative response mediated by non-genomic action of steroid receptors. Finally, receptor association with signaling effectors and scaffold proteins is the key event that initiates non-genomic proliferative, anti-apoptotic and migratory programs. It is therefore a promising target for novel anti-cancer therapy. Each of these aspects has been analyzed in several cell types and in relation to different biological effects. Much more work is required to fully evaluate their role in hormone action and their application in cancer therapy.

Cellular responses to signals require the action of a myriad of protein networks, which are regulated by protein/protein associations [1]. Rapid actions of steroid hormones are also subject to this regulation. They induce direct association of steroid receptors with different proteins (e.g., growth factor receptors, signaling effectors, scaffold proteins, transcription factors). These multi-molecular complexes drive signaling activation and finally trigger basic hormonal effects. Receptor/protein associations are attracting increased interest concerning their role in hormone action as well as their potential use as therapeutic targets in hormonal diseases.

In addition to stimulating gene transcription, sex steroids trigger rapid, non-genomic responses in the extra-nuclear compartment of target cells. These events take place within seconds or minutes after hormone administration and do not require transcriptional activity of sex steroid receptors. Depending on cell systems, activation of extra-nuclear signaling pathways by sex steroids fosters cell cycle progression, prevents apoptosis, leads to epigenetic modifications and increases cell migration through cytoskeleton changes. These findings have raised the question of intracellular localization of sex steroid receptors mediating these responses. During the past years, increasing evidence has shown that classical sex steroid receptors localized in the extra-nuclear compartment or close to membranes of target cells induce these events. The emerging picture is that a process of bidirectional control between signaling activation and sex steroid receptor localization regulates the outcome of hormonal responses in target cells. This mechanism ensures cell cycle progression in estradiol-treated breast cancer cells, and its derangement might occur in progression of human proliferative diseases. These findings will be reviewed here together with unexpected examples of the relationship between sex steroid receptor localization, signaling activation and biological responses in target cells. We apologize to scientists whose reports are not mentioned or extensively discussed owing to space limitations.