Tricyclic Diterpenoids Selectively Suppress Androgen Receptor-Positive Prostate Cancer Cells

Androgen receptor (AR) is a viable therapeutic target for lethal castration-resistant prostate cancer (CRPC), because the continued progression of CRPC is mainly driven by the reactivation of AR transcriptional activity. The current FDA-approved AR antagonists binding to ligand binding domain (LBD) become ineffective in CRPC with AR gene amplification, LBD mutation, and the evolution of LBD-truncated AR splice variants. Encouraged by the fact that tricyclic aromatic diterpenoid QW07 has recently been established as a potential N-terminal AR antagonist, this study aims to explore the structure-activity relationship of tricyclic diterpenoids and their potential to suppress AR-positive cell proliferation. Dehydroabietylamine, abietic acid, dehydroabietic acid, and their derivatives were selected, since they have a similar core structure as QW07. Twenty diterpenoids were prepared for the evaluation of their antiproliferative potency on AR-positive prostate cancer cell models (LNCaP and 22Rv1) using AR-null cell models (PC-3 and DU145) as comparisons. Our data indicated that six tricyclic diterpenoids possess greater potency than enzalutamide (FDA-approved AR antagonist) towards LNCaP and 22Rv1 AR-positive cells, and four diterpenoids are more potent than enzalutamide against 22Rv1 AR-positive cells. The optimal derivative possesses greater potency (IC50 = 0.27 µM) and selectivity than QW07 towards AR-positive 22Rv1 cells.

[Research Progress in Androgen Receptor and Triple Negative Breast Cancer]

The research on androgen receptor (AR) in breast cancer is advancing.Although the prognostic value of AR in triple negative breast cancer (TNBC) is controversial,a variety of studies have demonstrated that the lack of AR expression exacerbates disease progression.Moreover,the TNBC subtype of AR(-) is more aggressive than that of AR(+) due to the lack of prognostic biomarkers and therapeutic targets.With the discovery and deepening research of novel therapeutic targets such as phosphatidylinositol 3-kinase/protein kinase B/mammalian target of rapamycin and S-phase kinase-associated protein 2 signaling pathways,as well as the emerging of immunotherapies,the treatment options for TNBC are increasing.Regarding the role of AR in TNBC,the studies about the tumor biology of AR(-)TNBC and novel biomarkers for improved management of the disease remain insufficient.In this review,we summarize the research progress of AR in TNBC,put forward avenues for future research on TNBC,and propose potential biomarkers and therapeutic strategies that warrant investigation.

Efficacy and safety of darolutamide in Black/African-American patients from the phase III ARAMIS study

Aim: Darolutamide significantly improved metastasis-free survival (MFS) and overall survival (OS) versus placebo in the phase III ARAMIS study. We evaluated outcomes in Black/African-American patients in ARAMIS. Materials & methods: Patients with nonmetastatic castration-resistant prostate cancer were randomized 2:1 to darolutamide (n = 955) or placebo (n = 554) plus androgen-deprivation therapy. The primary end point was MFS. Secondary end points included OS and safety. Results: In 52 (3.4%) Black/African-American patients, darolutamide improved MFS (median: not reached vs 12.4 months) and OS (3-year survival rates: 100 vs 71%) versus placebo. The safety profile of darolutamide in Black/African-American patients was consistent with that of all ARAMIS patients. Conclusion: In Black/African-American patients, darolutamide improved MFS and OS and was well tolerated, consistent with the overall ARAMIS population.

Darolutamide in hormone-sensitive and castration-resistant prostate cancer

Introduction: Important changes in the treatment of prostate cancer have taken place in recent years. Non-metastatic castration-resistant prostate cancer (nmCRPC) has been clinically delineated. In this setting, three drugs have been approved in high-risk disease: apalutamide, enzalutamide and darolutamide.Areas covered:This manuscript aims to profile darolutamide, its clinical development, pharmacologic properties, efficacy and safety. We presented the results of published clinical studies, but we also investigated ongoing ones.Expert opinion: An indirect comparison with the other two aforementioned drugs emerged. While the clinical efficacy is comparable, the toxicity profile is different for darolutamide, resulting in greater tolerance. We must wait for the results of the trials that study darolutamide in hormone-sensitive disease, both in the metastatic phase and in the localized phase. Clinical experience will also be important to determine ever more personalized treatments for patients.

COVID-19-The Potential Beneficial Therapeutic Effects of Spironolactone during SARS-CoV-2 Infection

In March 2020, coronavirus disease 2019 (COVID-19) caused by SARS-CoV-2 was declared a global pandemic by the World Health Organization (WHO). The clinical course of the disease is unpredictable but may lead to severe acute respiratory infection (SARI) and pneumonia leading to acute respiratory distress syndrome (ARDS). It has been shown that pulmonary fibrosis may be one of the major long-term complications of COVID-19. In animal models, the use of spironolactone was proven to be an important drug in the prevention of pulmonary fibrosis. Through its dual action as a mineralocorticoid receptor (MR) antagonist and an androgenic inhibitor, spironolactone can provide significant benefits concerning COVID-19 infection. The primary effect of spironolactone in reducing pulmonary edema may also be beneficial in COVID-19 ARDS. Spironolactone is a well-known, widely used and safe anti-hypertensive and antiandrogenic medication. It has potassium-sparing diuretic action by antagonizing mineralocorticoid receptors (MRs). Spironolactone and potassium canrenoate, exerting combined pleiotropic action, may provide a therapeutic benefit to patients with COVID-19 pneumonia through antiandrogen, MR blocking, antifibrotic and anti-hyperinflammatory action. It has been proposed that spironolactone may prevent acute lung injury in COVID-19 infection due to its pleiotropic effects with favorable renin–angiotensin–aldosterone system (RAAS) and ACE2 expression, reduction in transmembrane serine protease 2 (TMPRSS2) activity and antiandrogenic action, and therefore it may prove to act as additional protection for patients at highest risk of severe pneumonia. Future prospective clinical trials are warranted to evaluate its therapeutic potential.

Mechanisms of Androgen Receptor Agonist- and Antagonist-Mediated Cellular Senescence in Prostate Cancer

The androgen receptor (AR) plays a leading role in the control of prostate cancer (PCa) growth. Interestingly, structurally different AR antagonists with distinct mechanisms of antagonism induce cell senescence, a mechanism that inhibits cell cycle progression, and thus seems to be a key cellular response for the treatment of PCa. Surprisingly, while physiological levels of androgens promote growth, supraphysiological androgen levels (SAL) inhibit PCa growth in an AR-dependent manner by inducing cell senescence in cancer cells. Thus, oppositional acting ligands, AR antagonists, and agonists are able to induce cellular senescence in PCa cells, as shown in cell culture model as well as ex vivo in patient tumor samples. This suggests a dual AR-signaling dependent on androgen levels that leads to the paradox of the rational to keep the AR constantly inactivated in order to treat PCa. These observations however opened the option to treat PCa patients with AR antagonists and/or with androgens at supraphysiological levels. The latter is currently used in clinical trials in so-called bipolar androgen therapy (BAT). Notably, cellular senescence is induced by AR antagonists or agonist in both androgen-dependent and castration-resistant PCa (CRPC). Pathway analysis suggests a crosstalk between AR and the non-receptor tyrosine kinase Src-Akt/PKB and the PI3K-mTOR-autophagy signaling in mediating AR-induced cellular senescence in PCa. In this review, we summarize the current knowledge of therapeutic induction and intracellular pathways of AR-mediated cellular senescence.

Enzalutamide plus androgen-deprivation therapy in hormone-sensitive prostate cancer: new perspectives from a current Phase III clinical trial

Prostate cancer is a major health issue with an incidence of 1,100,000 worldwide. Eventually, 20-40% of curatively treated patients will face a biochemical recurrence. Lately, the treatment options in metastasized hormone sensitive prostate cancer (mHSPC) were rapidly evolving after years of stagnation. Encouraging results in clinical trials of combination treatment of androgen deprivation therapy with either chemotherapy or second-generation hormonal treatment indicate a paradigm shift in this clinical scenario. In the light of this, the current review is focusing on the concept and initial results of the Phase III (ARCHES) trial investigating enzalutamide plus androgen deprivation therapy in mHSPC. Moreover, a comprehensive appraisal of the expanding landscape of systemic therapies for mHSPC is provided.

Syringaresinol as a novel androgen receptor antagonist against wild and mutant androgen receptors for the treatment of castration-resistant prostate cancer: molecular docking, in-vitro and molecular dynamics study

Phytoestrogens are dietary estrogens having similar structure as of estrogen. Some of these phytoestrogens are androgen receptor (AR) antagonists and exhibit preventive role in the prostate cancer. However, in androgen-independent prostate cancer (AIPC) the ARs were mutated (T877A, W741L, F876L, etc.) and these mutant ARs convert the antagonist to agonist. Our aim in this study is to find phytoestrogens that could function as an antagonist with wild and mutant ARs. The phytoestrogens were analyzed for binding affinity with wild and mutant ARs in agonist and antagonist conformations. The point mutations were carried out using Chimera. The antagonist AR conformation was modeled using Modeller. We hypothesize that the compounds having binding affinity with agonist AR conformation could not function as a full or pure antagonist. Most of the phytoestrogens have binding affinity with agonist AR conformation contradicting previous results. For example, genistein which is a widely studied isoflavone has known AR antagonist property. However, in our study, it had good binding affinity with agonist AR conformation. Hence, to confirm our hypothesis, we tested genistein in LNCaP (T877A mutant AR) cells by qPCR studies. The genistein functioned as an antagonist only in the presence of an androgen indicting a partial agonist type of activity. The in-vitro results supported our docking hypothesis. We applied this principle and found syringaresinol could function as an antagonist with wild and mutated ARs. Further, we carried out molecular dynamics for the hit molecule to confirm its antagonist binding mode with mutant AR.Communicated by Ramaswamy H. Sarma.

Darolutamide For Castration-Resistant Prostate Cancer

The treatment landscape of advanced prostate cancer continues to evolve rapidly, with newer and more active drugs being used in earlier phases of the disease based on improved overall survival. After adoption of docetaxel for metastatic castration-sensitive disease, large trials with next-generation androgen receptor-signaling inhibitors (abiraterone, enzalutamide and apalutamide) have demonstrate significant improvements in survival and important secondary endpoints. For non-metastatic castration-resistant prostate cancer, recent phase III placebo-controlled trials with enzalutamide, apalutamide and darolutamide all demonstrated benefits in improving metastasis-free survival. This review aims to summarize the clinical development of darolutamide, a novel next-generation androgen receptor antagonist, including preclinical data, clinical studies and the potential of darolutamide for the treatment of advanced prostate cancer. To date, darolutamide efficacy and tolerability has been demonstrated in the ARAMIS trial, which demonstrated an improvement in metastasis-free survival compared to placebo for non-metastatic castration-resistant prostate cancer patients with a rapid PSA doubling time. Ongoing studies will further evaluate the role of darolutamide in metastatic castration-sensitive prostate cancer in combination with docetaxel (ARASENS trial) and also in other stages of the disease.

Targeting prosurvival BCL2 signaling through Akt blockade sensitizes castration-resistant prostate cancer cells to enzalutamide

BACKGROUND

Prostate cancer that recurs after initial treatment inevitably progresses to castration-resistant prostate cancer (CRPC), the lethal stage of the disease. Despite improvements in outcomes from next generation androgen receptor (AR)-axis inhibitors, CRPC remains incurable. Therapeutic strategies to target AR antagonist resistance are urgently needed to improve outcomes for men with this lethal form of prostate cancer.

METHODS

Apoptosis and BCL2 family signaling were characterized in cell line models of CRPC. Quantitative real-time polymerase chain reaction and Western blot analysis were used to determine BCL2 expression levels. Drug sensitivity was determined by proliferation, survival and apoptosis analysis. Protein-protein interactions were evaluated by coimmunoprecipitation followed by Western blot detection.

RESULTS

In the present study, we identify antiapoptotic BCL2 protein signaling as a mechanism of resistance to AR antagonist enzalutamide. In CRPC cell line models, we found that BCL-xL and MCL-1 proteins block apoptosis through binding and sequestering proapoptotic proteins BIM and BAX, resulting in cell survival in response to enzalutamide. Treatment with BH3-mimetics targeting BCL-xL or MCL-1 disrupts these interactions and activates apoptosis, sensitizing CRPC cells to enzalutamide. Importantly, we demonstrate that PI3K/Akt signaling is activated in response to enzalutamide and mediates apoptosis evasion through inactivation of BAD, a BH3-only protein that activates proapoptotic signlaing through inhbition of BCL-xL. Inhibition of Akt activates BAD, resulting in increased apoptosis and sensitivity to enzalutamide, demonstrating an alternative therapeutic strategy to target drug resistance.

CONCLUSIONS

These results demonstrate that CRPC cells employ multiple mechanisms to mediate apoptosis evasion through BCL2 signaling, suggesting this pathway is critical for survival. This study provides a strong preclinical rationale for developing therapeutic strategies to target antiapoptotic BCL2 signaling in combination with AR antagonists to improve treatment options for patients with advanced prostate cancer.

Chemistry and biology for the small molecules targeting characteristics of cancer cells

Despite the marked progress of cancer research, cancer is the predominant cause of death in Japan, and therefore development of effective therapeutic drugs is expected. Chemical biology is a research field utilizing small molecules to investigate biological phenomena. One of the most important aims of chemical biology is to find the small molecules, and natural products are ideal screening sources due to their structural diversity. Therefore, natural product screening based on the progress of chemical biology prompted us to find small molecules targeting cancer characteristics. Another contribution of chemical biology is to facilitate the target identification of small molecule. Therefore, among a variety of methods to uncover protein function, chemical biology is a remarkable approach in which small molecules are used as probes to elucidate protein functions related to cancer development.

ABBREVIATIONS

EGF: Epidermal growth factor; PDGF: Platelet-derived growth factor; CRPC: Castration-resistant prostate cancer; AR: Androgen receptor; FTase: Farnesyl transferase; 5-LOX: 5-Lipoxygenase; LT: Leukotriene; CysLT1: Cysteinyl leukotriene receptor 1; GPA: Glucopiericidin A; PA: Piericidin A; XN: Xanthohumol; VCP: Valosin-containing protein; ACACA: Acetyl-CoA carboxylase-α.

Androgen receptor antagonists for prostate cancer therapy

Androgen deprivation is the mainstay therapy for metastatic prostate cancer (PCa). Another way of suppressing androgen receptor (AR) signaling is via AR antagonists or antiandrogens. Despite being frequently prescribed in clinical practice, there is conflicting evidence concerning the role of AR antagonists in the management of PCa. In the castration-resistant settings of PCa, docetaxel has been the only treatment option for decades. With recent evidence that castration-resistant PCa is far from AR-independent, there has been an increasing interest in developing new AR antagonists. This review gives a concise overview of the clinically available antiandrogens and the experimental AR antagonists that tackle androgen action with a different approach.

Potential targets in the discovery of new hair growth promoters for androgenic alopecia

INTRODUCTION

Androgenic alopecia (AGA) is the major type of scalp hair loss affecting 60 - 70% of the population worldwide. It is caused by two potent androgens, namely testosterone (T) and 5α-dihydrotestosterone (5α-DHT). Till date, only two FDA-approved synthetic drugs, minoxidil and finasteride, are used to cure AGA with only 35 and 48% success, respectively; therefore, a search for new drug based on the mechanism of androgens action is still needed.

AREAS COVERED

Relevant literature was reviewed to identify current therapeutic targets and treatments for AGA. The potential targets are classified into three categories: i) 5α-reductase; ii) androgen receptor and iii) growth-factor-producing genes related to hair growth.

EXPERT OPINION

Relevant assay systems using the right targets are required in order to obtain specific and effective drugs for AGA treatment. It is unlikely that single targeted agents will be sufficient for treating AGA, and therefore, it would be a challenge to obtain compounds with multiple activities.

Enzalutamide (Xtandi) for patients with metastatic, resistant prostate cancer

OBJECTIVE

To review the pharmacology and pharmacokinetics, and to evaluate the clinical efficacy, safety, and place in therapy of enzalutamide for the treatment of castration-resistant prostate cancer (CRPC).

DATA SOURCES

A literature search through PubMed (1984 to November 2013; English language) was performed using the following keywords: MDV3100, androgen deprivation therapy, enzalutamide, CRPC, and androgen receptor antagonist. Searches were limited to published studies in humans.

STUDY SELECTION AND DATA EXTRACTION

All articles in English identified from reviews, abstracts, presentations, and clinical trials of enzalutamide in humans were selected and included.

DATA SYNTHESIS

Enzalutamide is an oral, nonsteroidal second-generation androgen receptor antagonist that is Food and Drug Administration-approved for the treatment of metastatic CRPC in men who were previously treated with docetaxel. Enzalutamide was superior to placebo for increasing median survival from 13.6 months to 18.4 months. Enzalutamide was well tolerated at a dose of 160 mg, with minor adverse events such as fatigue, diarrhea, musculoskeletal pain, and hot flashes. Patients with increased risk of seizure should not take enzalutamide.

CONCLUSIONS

Enzalutamide is effective to slow progression of metastatic CRPC, to reduce prostate-specific antigen (PSA) levels, to decrease time to progression of PSA, to increase time to first skeletal-related events, and to increase quality of response rate. Enzalutamide was given at 160 mg/d for a median of 8 cycles of administration. Clinical trials are currently being conducted to observe if enzalutamide will be useful for treatment of other cancers and for early administration in prostate cancer.

Therapeutic leads for castrate resistant prostate cancer

Castrate resistant prostate cancer (CRPC) is associated with increased androgen receptor (AR) signaling often brought about by elevated intratumoral androgen biosynthesis and AR amplification. Inhibition of androgen biosynthesis and/or AR antagonism should be efficacious in the treatment of CRPC. AKR1C3 catalyzes the formation of potent AR ligands from inactive precursors and is one of the most upregulated genes in CRPC. AKR1C3 inhibitors should not inhibit the related isoforms, AKR1C1 and AKR1C2 that are involved in 5α-dihydrotestosterone inactivation in the prostate. We have previously developed a series of flufenamic acid analogs as potent and selective AKR1C3 inhibitors [Adeniji, A. O. et al., J. Med. Chem.2012, 55, 2311]. Here we report the X-ray crystal structure of one lead compound 3-((4-(trifluoromethyl)phenyl) amino)benzoic acid (1) in complex with AKR1C3. Compound 1 adopts a similar binding orientation as flufenamic acid, however, its phenylamino ring projects deeper into a subpocket and confers selectivity over the other AKR1C isoforms. We exploited the observation that some flufenamic acid analogs also act as AR antagonists and synthesized a second generation inhibitor, 3-((4-nitronaphthalen-1-yl)amino)benzoic acid (2). Compound 2 retained nanomolar potency and selective inhibition of AKR1C3 but also acted as an AR antagonist. It inhibited 5α-dihydrotestosterone stimulated AR reporter gene activity with an IC(50)=4.7 μM and produced a concentration dependent reduction in androgen receptor levels in prostate cancer cells. The in vitro and cell-based effects of compound 2 make it a promising lead for development of dual acting agent for CRPC. To illuminate the structural basis of AKR1C3 inhibition, we also report the crystal structure of the AKR1C3·NADP(+)·2 complex, which shows that compound 2 forms a unique double-decker structure with AKR1C3.