The development of androgen-independent prostate cancer

The proteasome inhibitor, bortezomib, induces prostate cancer cell death by suppressing the expression of prostate-specific membrane antigen, as well as androgen receptor

The progression of primary prostate cancer (PC) is dependent on the androgen receptor (AR) and prostate‑specific membrane antigen (PSMA). Furthermore, the growth of PC cells is terminated with the downregulation of both AR and PSMA. In our preliminary experiments, it was also found that bortezomib (BZ; PS‑341) that inhibits 26S proteasome activity, acts as a downregulator of both PSMA and AR. In addition to evaluating the effects of BZ on protein expression, the present study evaluated and compared the anticancer effects of BZ on the growth of cells treated with BZ, docetaxel (DOC), or a combination of both. Western blot analysis was used to examine the expression levels of AR and PSMA. The knockdown effect of small interfering RNA (siRNA) and the drugs on the expression of either AR or PSMA was also evaluated. An MTT assay was performed in order to evaluate the inhibitory effects of the drugs on PC cells. The cell cycles were analyzed, and apoptotic cells were detected. The downregulation of AR and PSMA was observed using siRNA specific to AR or PSMA, and the inhibition of PSMA, as well as that of AR severely suppressed the growth of PC cells. The inhibitory effect of BZ alone on PSMA expression was similar to that of both AR‑ and PSMA‑specific siRNA, and this drug also induced the downregulation of AR and PSMA in PC cells. This phenomenon was confirmed even in cells transfected to overexpress PSMA. The apoptosis‑promoting effect of BZ on the cells was similar to that observed with BZ plus DOC, and more potent than that of DOC alone. BZ had the same inhibitory effect on the expression of AR and PSMA as did siRNA specific to AR or PSMA. On the whole, the findings of this study indicate that BZ may prove to be a promising chemotherapeutic agent and may be used as a molecularly targeted drug in the treatment of PC.

Testosterone-mediated activation of androgenic signalling sustains in vitro the transformed and radioresistant phenotype of rhabdomyosarcoma cell lines

PURPOSE

Rhabdomyosarcoma (RMS), the most common soft-tissue sarcoma in childhood, rarely affects adults, preferring male. RMS expresses the receptor for androgen (AR) and responds to androgen; however, the molecular action of androgens on RMS is unknown.

METHODS

Herein, testosterone (T) effects were tested in embryonal (ERMS) and alveolar (ARMS) RMS cell lines, by performing luciferase reporter assay, RT-PCR, and western blotting experiments. RNA interference experiments or bicalutamide treatment was performed to assess the specific role of AR. Radiation treatment was delivered to characterise the effects of T treatment on RMS intrinsic radioresistance.

RESULTS

Our study showed that RMS cells respond to sub-physiological levels of T stimulation, finally promoting AR-dependent genomic and non-genomic effects, such as the transcriptional regulation of several oncogenes, the phosphorylation-mediated post-transductional modifications of AR and the activation of ERK, p38 and AKT signal transduction pathway mediators that, by physically complexing or not with AR, participate in regulating its transcriptional activity and the expression of T-targeted genes. T chronic daily treatment, performed as for the hormone circadian rhythm, did not significantly affect RMS cell growth, but improved RMS clonogenic and radioresistant potential and increased AR mRNA both in ERMS and ARMS. AR protein accumulation was evident in ERMS, this further developing an intrinsic T-independent AR activity.

CONCLUSIONS

Our results suggest that androgens sustain and improve RMS transformed and radioresistant phenotype, and therefore, their therapeutic application should be avoided in RMS post puberal patients.

RNA-based markers in biopsy cores with atypical small acinar proliferation: Predictive effect of T2E fusion positivity and MMP-2 upregulation for a subsequent prostate cancer diagnosis

BACKGROUND

Atypical small acinar proliferation (ASAP) is a precursor lesion of prostate cancer (PC), and PC develops from this suspicious focus or an unsampled malignant gland nearby. However, PC-related molecular alterations that could guide the timing of repeat biopsies and help monitor PC risk in ASAP-diagnosed patients have not been investigated. The purpose of this study was to first investigate the expression of seven different PC-related RNAs that included serine 2 (TMPRSS2): erythroblastosis virus E26 oncogene homolog (ERG) gene (TMPRSS2-ERG, T2E) fusion, alpha-methylacyl-CoA racemase (AMACR), kallikrein related peptidase 3 (KLK3), androgen receptor (AR), prostate cancer specific antigen 3 (PCA3), and matrix metalloproteinases (MMP)-2 and 9.

METHODS

PC-related RNAs were evaluated using a real-time quantitative reverse transcription polymerase chain reaction (RT-qPCR) system in pathologically ASAP-diagnosed prostate biopsy cores from 55 patients presenting with a normal digital rectal examination and a PSA level of 4-10 ng/mL.

RESULTS

We detected that positive T2E fusion status (P = 0.013) and the expression of AMACR (P = 0.016), AR (P = 0.016) and MMP-2 (P = 0.013) were independently and significantly associated with PC risk in ASAP patients. There were also several statistically significant correlations between expression levels. Additionally, we demonstrated that T2E fusion positive ASAP patients with higher MMP-2 expression were more likely to be diagnosed with PC at a subsequent biopsy during the follow-up period (P = 0.003).

CONCLUSIONS

Although, more clinical validations are needed for the stratification of PC risk in ASAP-diagnosed biopsy cores, our current results indicate that the coexistence of T2E fusion positivity with MMP-2 upregulation may help clinicians adjust their biopsy timetable and/or assessment of PC risk in ASAP-diagnosed patients with a PSA level of 4-10 ng/mL.

Non-coding and coding genomic variants distinguish prostate cancer, castration-resistant prostate cancer, familial prostate cancer, and metastatic castration-resistant prostate cancer from each other

A considerable number of deposited variants has provided new possibilities for knowledge discovery in different types of prostate cancer. Here, we analyzed variants located on 3'UTR, 5'UTR, CDs, Intergenic, and Intronic regions in castration-resistant prostate cancer (8496 variants), familial prostate cancer (3241 variants), metastatic castration-resistant prostate cancer (3693 variants), and prostate cancer (16599 variants). Chromosome regions 10p15-p14 and 2p13 were highly enriched (P < 0.00001) for variants located in 3'UTR, 5'UTR, CDs, intergenic, and intronic regions in castration-resistant prostate cancer. In contrast, 10p15-p14, 10q23.3, 12q13.11, 13q12.3, 1q25, and 8p22 regions were enriched (P < 0.001) in familial prostate cancer. In metastatic castration-resistant prostate cancer, 10p15-p14, 10q23.3, 11q22-q23, 14q21.1, and 14q32.13 were highly variant regions (P < 0.001). Chromosome 2 and chromosome 1 hosted many enriched variant regions. AKR1C3, BRCA1, BRCA2, CHGA, CYP19A1, HOXB13, KLK3, and PTEN contained the highest number of 3'UTR, 5'UTR, CDs, Intergenic, and Intronic variants. Network analysis showed that these genes are upstream of important functions including prostate gland development, tumor recurrence, prostate cancer-specific survival, tumor progression, cancer mortality, long-term survival, cancer recurrence, angiogenesis, and AR. Interestingly, all of EGFR, JAK2, NR3C1, PDZD2, and SEMA3C genes had single nucleotide polymorphisms (SNP) in castration-resistant prostate cancer, consistent with high selection pressure on these genes during drug treatment and consequent resistance. High occurrence of variants in 3'UTRs suggests the importance of regulatory variants in different types of prostate cancer; an area that has been neglected compared with coding variants. This study provides a comprehensive overview of genomic regions contributing to different types of prostate cancer.

Pretreatment Neutrophil to Lymphocyte Ratio (NLR) Predicts Prognosis for Castration Resistant Prostate Cancer Patients Underwent Enzalutamide

Introduction

Nearly 80% of advanced prostate cancer patients respond to initial androgen deprivation therapy (ADT). However, ADT does not prevent the progression of prostate cancer over the long term, and the disease eventually progresses to castration-resistant prostate cancer (CRPC). Prior to the development of enzalutamide (ENZ) and abiraterone acetate, docetaxel was the only established treatment with life-prolongation for CRPC. ENZ is a second-generation anti-androgen receptor drug that has contributed to improving the prognosis of CRPC. Several studies have reported factors predicting the efficacy of ENZ; however, there are no confirmed biomarkers. The neutrophil-to-lymphocyte ratio (NLR) is an easily calculated biomarker that is associated with the prognosis of several solid malignancies. However, there were few studies investigated NLR for ENZ in patients with mCRPC. We examined the usefulness of the NLR as a predictive tool for ENZ.

Methods

We retrospectively examined a total of 106 CRPC patients who were treated with ENZ until September 2016 in Yokohama City University Hospital, Yokohama City University Medical Center, and National Cancer Center Hospital East. ENZ was routinely started as a dose of 160 mg per day; the dosage was reduced in some patients due to side effects. Drug holiday for 1-2 weeks or dose reduction to 80-120mg was done and no patients discontinued ENZ treatment due to adverse effects. ENZ was stopped when cancer progression was detected based on PSA elevation, radiographic findings, and deterioration of the patient's performance status. The cut-off NLRs for overall survival (OS) and cancer-specific survival (CSS) were determined based on the receiver-operator curves. Kaplan-Meier curves were used to analyze the factors associated with OS or CSS and a log-rank test was performed. A multivariate analysis was also performed to analyze the factors associated with the prognosis.

Results

We retrospectively reviewed 106 consecutive CRPC patients who were both treated with ENZ and were able to be counted before ENZ NLR. Cut-off point was 2.14 for both OS and CSS by receiver operator characteristic curve. The patients were then divided into the higher NLR group (≥2.14) and lower NLR group (<2.14). Multivariate analysis showed that NLR and predocetaxel chemotherapy were independent risk factors for both overall and cancer-specific survival.

Conclusions

The NLR might be a useful biomarker for predicting the prognosis of mCRPC patients who are treated with ENZ.

Bone Metastasis: Find Your Niche and Fit in

Metastasis to bones is determined by both intrinsic traits of metastatic tumor cells and properties appertaining to the bone microenvironment. Bone marrow niches are critical for all major steps of metastasis, including the seeding of disseminated tumor cells (DTCs) to bone, the survival of DTCs and microscopic metastases under dormancy, and the eventual outgrowth of overt metastases. In this review, we discuss the role of bone marrow niches in bone colonization. The emphasis is on complicated and dynamic nature of cancer cells-niche interaction, which may underpin the long-standing mystery of metastasis dormancy, and represent a therapeutic target for elimination of minimal residue diseases and prevention of life-taking, overt metastases.

Parameter identification of a model for prostate cancer treated by intermittent therapy

Adenocarcinoma is the most frequent cancer affecting the prostate walnut-size gland in the male reproductive system. Such cancer may have a very slow progression or may be associated with a "dark prognosis" when tumor cells are spreading very quickly. Prostate cancers have the particular properties to be marked by the level of prostate specific antigen (PSA) in blood which allows to follow its evolution. At least in its first phase, prostate adenocarcinoma is most often hormone-dependent and, consequently, hormone therapy is a possible treatment. Since few years, hormone therapy started to be provided intermittently for improving patient's quality of life. Today, durations of on- and off-treatment periods are still chosen empirically, most likely explaining why there is no clear benefit from the survival point of view. We therefore developed a model for describing the interaction between the tumor environment, the PSA produced by hormone-dependent and hormone-independent tumor cells, respectively, and the level of androgens. Model parameters were identified using a genetic algorithm applied to the PSA time series measured in a few patients who initially received prostatectomy and were then treated by intermittent hormone therapy (LHRH analogs and anti-androgen). The measured PSA time series is quite correctly reproduced by free runs over the whole follow-up. Model parameter values allow for distinguishing different types of patient (age and Gleason score) meaning that the model can be individualized. We thus showed that the long-term evolution of the cancer can be affected by durations of on- and off-treatment periods.

Development of a Transcriptional Amplification System Based on the PEG3 Promoter to Target Androgen Receptor-Positive and -Negative Prostate Cancer Cells

Localized prostate cancer (PCa) is often curable, whereas metastatic disease treated by castration inevitably progresses toward castration-resistant PCa (CRPC). Most CRPC treatments target androgen receptor (AR) signaling. However, not all CRPC cells rely on AR activity for survival and proliferation. With advances in immunotherapy and fluid biopsies for cancer management, expression systems specific for both AR-positive and -negative PCa are required for virus-based vaccines and cell imaging. To target both AR-responsive and non-responsive cells, we developed a three-step transcriptional amplification (3STA) system based on the progression elevated gene-3 (PEG3) promoter named PEG3AP1-3STA. Notably, we report on different genetic modifications that significantly improved PEG3 promoter's strength in PCa cells. Adenoviruses incorporating PEG3 promoter with and without transcriptional amplification systems were generated. The potential of PEG3AP1-3STA to target PCa cells was then evaluated in vitro and in vivo in androgen-responsive and non-responsive PCa cell lines. PEG3AP1-3STA was shown to be active in all PCa cell lines and not regulated by androgens, and its activity was amplified 97-fold compared to that of a non-amplified promoter. The PEG3AP1-3STA system can thus be used to target advanced AR+ and AR- cells for imaging or immunovirotherapy in advanced PCa.

Association of genetic variation of the six gene prognostic model for castration-resistant prostate cancer with survival

BACKGROUND

We previously identified a blood RNA transcript-based model consisting of six immune or inflammatory response genes (ABL2, SEMA4D, ITGAL, C1QA, TIMP1, and CDKN1A) that was prognostic for survival in cohorts of men with castration-resistant prostate cancer (CRPC). We investigated whether inherited variation in these six genes was associated with overall survival (OS) in men with CRPC.

METHODS

The test cohort comprised 600 patients diagnosed with CRPC between 1996 and 2011 at Dana-Farber Cancer Institute. Genotyping of 66 tagging single nucleotide polymorphisms (SNPs) spanning the six genes was performed on blood derived DNAs. For the top four SNPs (P < 0.05), validation was conducted in an independent cohort of 223 men diagnosed with CRPC between 2000 and 2014. Multivariable Cox regression adjusting for known prognostic factors estimated hazard ratios (HR) and 95% confidence intervals (CI) of the association of genetic variants with OS.

RESULTS

Two thirds of patients in both cohorts had metastases at CRPC diagnosis. Median OS from CRPC diagnosis was 3.6 (95%CI 3.3-4.0) years in the test cohort and 4.6 (95%CI 3.8-5.2) years in the validation cohort. Fifty-nine SNPs in Hardy-Weinberg equilibrium were analyzed. The major alleles of rs1318056 and rs1490311 in ABL2, and the minor alleles of rs2073917 and rs3764322 in ITGAL were associated with increased risk of death in the test cohort (adjusted-HRs 1.27-1.39; adjusted-p <0.05; false discovery rate <0.35). In the validation cohort, a similar association with OS was observed for rs1318056 in ABL2 (adjusted-HR 1.44; 95%CI 0.89-2.34) and rs2073917 in ITGAL (adjusted-HR 1.41; 95%CI 0.82-2.42). The associations did not reach statistical significance most likely due to the small sample size of the validation cohort (adjusted-p = 0.142 and 0.209, respectively). Additional eQTL analysis indicated that minor alleles of rs1318056 and rs1490311 in ABL2 are associated with a lower ABL2 expression in blood.

CONCLUSIONS

These findings corroborate our initial work on the RNA expression of genes involved in immunity and inflammation from blood and clinical outcome and suggest that germline polymorphisms in ABL2 and ITGAL may be associated with the risk of death in men with CRPC. Further studies are needed to validate these findings and to explore their functional mechanisms.

Wnt/Beta-Catenin Signaling and Prostate Cancer Therapy Resistance

Metastatic or locally advanced prostate cancer (PCa) is typically treated with androgen deprivation therapy (ADT). Initially, PCa responds to the treatment and regresses. However, PCa almost always develops resistance to androgen deprivation and progresses to castrate-resistant prostate cancer (CRPCa), a currently incurable form of PCa. Wnt/β-Catenin signaling is frequently activated in late stage PCa and contributes to the development of therapy resistance. Although activating mutations in the Wnt/β-Catenin pathway are not common in primary PCa, this signaling cascade can be activated through other mechanisms in late stage PCa, including cross talk with other signaling pathways, growth factors and cytokines produced by the damaged tumor microenvironment, release of the co-activator β-Catenin from sequestration after inhibition of androgen receptor (AR) signaling, altered expression of Wnt ligands and factors that modulate the Wnt signaling, and therapy-induced cellular senescence. Research from genetically engineered mouse models indicates that activation of Wnt/β-Catenin signaling in the prostate is oncogenic, enables castrate-resistant PCa growth, induces an epithelial-to-mesenchymal transition (EMT), promotes neuroendocrine (NE) differentiation, and confers stem cell-like features to PCa cells. These important roles of Wnt/β-Catenin signaling in PCa progression underscore the need for the development of drugs targeting this pathway to treat therapy-resistant PCa.

Neural Transcription Factors in Disease Progression

Progression to the malignant state is fundamentally dependent on transcriptional regulation in cancer cells. Optimum abundance of cell cycle proteins, angiogenesis factors, immune evasion markers, etc. is needed for proliferation, metastasis or resistance to treatment. Therefore, dysregulation of transcription factors can compromise the normal prostate transcriptional network and contribute to malignant disease progression.The androgen receptor (AR) is considered to be a key transcription factor in prostate cancer (PCa) development and progression. Consequently, androgen pathway inhibitors (APIs) are currently the mainstay in PCa treatment, especially in castration-resistant prostate cancer (CRPC). However, emerging evidence suggests that with increased administration of potent APIs, prostate cancer can progress to a highly aggressive disease that morphologically resembles small cell carcinoma, which is referred to as neuroendocrine prostate cancer (NEPC), treatment-induced or treatment-emergent small cell prostate cancer. This chapter will review how neuronal transcription factors play a part in inducing a plastic stage in prostate cancer cells that eventually progresses to a more aggressive state such as NEPC.

An Overview of the Polymorphisms of Circadian Genes Associated With Endocrine Cancer

A major consequence of the world industrialized lifestyle is the increasing period of unnatural light in environments during the day and artificial lighting at night. This major change disrupts endogenous homeostasis with external circadian cues, which has been associated to higher risk of diseases affecting human health, mainly cancer among others. Circadian disruption promotes tumor development and accelerate its fast progression. The dysregulation mechanisms of circadian genes is greatly affected by the genetic variability of these genes. To date, several core circadian genes, also called circadian clock genes, have been identified, comprising the following: ARNTL, CLOCK, CRY1, CRY2, CSNK1E, NPAS2, NR1D1, NR1D2, PER1, PER2, PER3, RORA, and TIMELESS. The polymorphic variants of these circadian genes might contribute to an individual's risk to cancer. In this short review, we focused on clock circadian clock-related genes, major contributors of the susceptibility to endocrine-dependent cancers through affecting circadian clock, most likely affecting hormonal regulation. We examined polymorphisms affecting breast, prostate and ovarian carcinogenesis, in addition to pancreatic and thyroid cancer. Further study of the genetic composition in circadian clock-controlled tumors will be of great importance by establishing the foundation to discover novel genetic biomarkers for cancer prevention, prognosis and target therapies.

The Impact of Intermittent Androgen Suppression Therapy in Prostate Cancer Modeling

Previous studies on prostate cancer modeling under hormonal therapy successfully fit clinical serum androgen data, under the assumption that the levels of intracellular and serum androgen are similar. However, such an assumption may not hold throughout the course of treatment. In this paper, we propose a model that directly accounts for serum androgen and its interaction with intracellular androgen. We establish biological links between the model and clinical data, and discuss in detail parameter ranges and the initialization of model variables. We further investigate parameter sensitivity over time, which gauges the maximum effect of varying each parameter and allows us to fix some parameters, to increase the robustness of the parameter fitting process. By relying on the characteristics of intermittent androgen suppression therapy (IAS), we employ a two-part weighted error function for fitting. We also carry out mathematical analyses to study the dynamic aspects of the system with different androgen thresholds. We find that the proposed model shows superior forecasting ability, compared to its predecessor. Furthermore, we demonstrate the impact of androgen on the dynamics of the androgen-dependent and -independent cancer cells, which suggests the discrete description of androgen dependency may not give a realistic characterization of the cancer population. We show that IAS has certain characteristics that need to be considered for parameter estimation. Our results demonstrate that the model and the fitting scheme are viable for similar applications of prostate cancer modeling under hormonal therapy.

Identification of SEPTIN12 as a novel target of the androgen and estrogen receptors in human testicular cells

SEPTIN12 (SEPT12) is a testis-enriched gene that is downregulated in the testis of infertile men with severe spermatogenic defects. While SEPT12 is involved in spermatogenic failure and sperm motility disorder, SEPT12 transcriptional regulation is still unknown. Here we report the promoter region of SEPT12 as a 245 bp segment upstream of the transcription start site. One androgen receptor (AR) and two estrogen receptor α (ERα) binding sites in this region were initially identified by bioinformatics prediction and confirmed by chromatin immunoprecipitation assay. Truncated ERα or AR binding sites decreased the promoter activity, which indicated that the ERα and AR are essential for the SEPT12 promoter. On the other hand, the promoter activity was enhanced by the treatment with 17β-estradiol (E2) and 5α-dihydrotestosterone (5α-DHT). Thus, one androgen and two estrogen hormone responsive elements located in the promoter of SEPT12 gene can regulate SEPT12 expression. Two single nucleotide polymorphisms (SNPs), rs759992 T > C and rs3827527 C > T, were observed in the SEPT12 gene promoter region and were able to decrease the promoter activity. In conclusion, the current work identified the promoter of the human SEPT12 gene and provided key evidence about its transcriptional regulation via E2 and 5α-DHT. Since SEPT12 has an important role in spermatogenesis, SEPT12 expression analysis can be developed as a potential tool for the assessment of environmental or food pollution by hormones or for the evaluation of the risk of endocrine-disrupting chemicals (EDCs) in general.

MicroRNA-135a induces prostate cancer cell apoptosis via inhibition of STAT6

Clinical management of metastatic prostate cancer remains a challenge. Activation of apoptosis signaling pathways via signal transducer and activator of transcription 6 (STAT6) has been hypothesized to be a therapeutic strategy for patients with metastatic prostate cancer. The ONCOMINE^® prostate cancer database and two Gene Expression Omnibus datasets (Gene Series 40026 and 21032) were re-analyzed to determine the expression levels of STAT6 and microRNA (miR)-135a in prostate cancer. The current study investigated the induced overexpression of miR-135a in prostate cancer cell lines to detect its function in prostate cell apoptosis using Hoechst staining and fluorescence-activated cell sorting and examined the expression levels of STAT6 and its DNA binding ability using western blotting and an electrophoretic mobility shift assay. In analysis of the ONCOMINE^® database, STAT6 expression levels in prostate cancer tissue were higher compared with those in normal prostate gland tissue and were associated with the overall survival rate and biochemical relapse rate following radical prostatectomy. Additionally, there was an inverse correlation between miR-135a and STAT6 expression levels in prostate cancer cell lines. miR-135a was able to induce prostate cancer cell apoptosis via targeting STAT6 mRNA and subsequently repressing protein expression and phosphorylation, which also altered the transcriptional factor function of STAT6 through its DNA-binding capabilities. In conclusion, miR-135a may function as a tumor-suppressing miRNA in prostate cancer and its anti-oncogenic activity may involve the direct targeting and inhibition of STAT6.

Ex vivo Culture and Lentiviral Transduction of Benign Prostatic Hyperplasia (BPH) Samples

To assess oncogenic potential, classical transformation assays are based on cell line models. However, cell line based models do not reflect the complexity of human tissues. We thus developed an inducible expression system for gene expression in ex vivo human tissues, which maintain native tissue architecture, such as epithelia and stroma. To validate the system, we transduced and expressed known tumor suppressors (p53, p33ING1b), oncoproteins (RasV12, p47ING3), or controls (empty vector, YFP) in ex vivo prostate tissues, then assessed proliferation by immunohistochemistry of markers (H3S10^phos). Herein, we describe how to generate lentiviral vectors and particules, successfully transduce human prostate tissues, induce exogenous gene expression, and assess cellular proliferation.

Mechanisms of Lysophosphatidic Acid-Mediated Lymphangiogenesis in Prostate Cancer

Prostate cancer (PCa) is the most common noncutaneous cancer in men worldwide. One of its major treatments is androgen deprivation therapy, but PCa frequently relapses as aggressive castration resistant local tumors and distal metastases. Hence, the development of novel agents or treatment modalities for advanced PCa is crucial. Many tumors, including PCa, first metastasize to regional lymph nodes via lymphatic vessels. Recent findings demonstrate that the bioactive lipid lysophosphatidic acid (LPA) promotes PCa progression by regulating vascular endothelial growth factor-C (VEGF-C), a critical mediator of tumor lymphangiogenesis and lymphatic metastasis. Many of the underlying molecular mechanisms of the LPA–VEGF-C axis have been described, revealing potential biomarkers and therapeutic targets that may aid in the diagnosis and treatment of advanced PCa. Herein, we review the literature that illustrates a functional role for LPA signaling in PCa progression. These discoveries may be especially applicable to anti-lymphangiogenic strategies for the prevention and therapy of metastatic PCa.

Plasma androgen receptor and serum chromogranin A in advanced prostate cancer

Recently, mixed forms between adenocarcinoma and neuroendocrine prostate cancer (NEPC) have emerged that are characterized by persistent androgen receptor (AR)-signalling and elevated chromogranin A (CgA) levels. The main aim of this study was to analyze castration-resistant prostate cancer (CRPC) patients treated with abiraterone or enzalutamide, assessing progression-free/overall survival (PFS/OS) in association with circulating AR and CgA. AR aberrations were analyzed by droplet digital PCR in pre-treatment plasma samples collected from two biomarker protocols [197 patients from a retrospective study (REC 2192/2013) and 59 from a prospective trial (REC 6798/2015)]. We subdivided patients into three groups according to CgA by receiver-operating characteristic (ROC) curves. In the primary cohort, plasma AR gain and mutations (p.L702H/p.T878A) were detected in 78 (39.6%) and 16 (8.1%) patients, respectively. We observed a significantly worse PFS/OS in patients with higher-CgA than in patients with normal-CgA, especially those with no AR-aberrations. Multivariable analysis showed AR gain, higher-CgA and LDH levels as independent predictors of PFS [hazard ratio (HR) = 2.16, 95% confidence interval (95% CI) 1.50-3.12, p < 0.0001, HR = 1.73, 95% CI 1.06-2.84, p = 0.026, and HR = 2.13, 95% CI 1.45-3.13, p = 0.0001, respectively) and OS (HR = 1.72, 95% CI 1.15-2.57, p = 0.008, HR = 3.63, 95% CI 2.13-6.20, p < 0.0001, and HR = 2.31, 95% CI 1.54-3.48, p < 0.0001, respectively). These data were confirmed in the secondary cohort. Pre-treatment CgA detection could be useful to identify these mixed tumors and would seem to have a prognostic role, especially in AR-normal patients. This association needs further evaluation in larger prospective cohorts.

Effects of non-steroidal anti-inflammatory drug-activated gene-1 on Ganoderma lucidum polysaccharides-induced apoptosis of human prostate cancer PC-3 cells

Ganoderma lucidum polysaccharides (GLP) has been demonstrated to elicit antitumorigenic and proapoptotic activities in cancer; however, the molecular mechanisms underlying the anticancer effects of GLP have yet to be elucidated. Non-steroidal anti-inflammatory drug-activated gene-1 (NAG-1) has been reported to exert proapoptotic effects and therefore, may serve an important role in cancer prevention. The present study aimed to elucidate the molecular mechanism by which GLP stimulates anticancer activity in human prostate cancer (PCa) PC-3 cells. In addition, the role of NAG-1 in GLP-induced cancer inhibition was examined. The results of the present study demonstrated that GLP significantly inhibited cell viability in a time- and dose-dependent manner in PC-3 cells. Flow cytometry indicated that GLP induced late apoptosis, which was accompanied by poly (ADP-ribose) polymerase 1 (PARP) cleavage, and inhibition of pro-caspase-3, -6 and -9 protein expression. Furthermore, it was observed that the expression levels of NAG-1, and its transcriptional factor early growth response-1, were upregulated in a time- and dose-dependent manner upon GLP treatment. The results of a luciferase assay demonstrated that GLP induced the promoter activity of NAG-1, thus indicating that NAG-1 may be transcriptionally regulated by GLP. The secretion of NAG-1 proteins into the cell culture medium was also upregulated upon GLP treatment. Furthermore, inhibition of NAG-1 expression by small interfering RNA significantly, but not completely, prevented GLP-induced apoptosis, and reversed the effects of GLP on PARP and pro-caspase expression. It was further demonstrated that GLP inhibited the phosphorylation of protein kinase B and mitogen-activated protein kinase/extracellular signal-regulated kinase signaling in PC-3 cells. The present study is the first, to the best of our knowledge, to report that GLP may induce apoptosis of PCa cells, which is partially mediated through NAG-1 induction. The present findings may be helpful in elucidating the anticancer mechanisms of GLP through NAG-1 induction for its chemopreventive potential in PCa.

Elevation of androgen receptor promotes prostate cancer metastasis by induction of epithelial-mesenchymal transition and reduction of KAT5

Androgen receptor (AR), an androgen‐activated transcription factor, belongs to the nuclear receptor superfamily. AR plays an important role in the development and progression of prostate cancer (PCa). However, the role of AR in PCa metastasis is not fully understood. To investigate the role of AR in PCa metastasis, we examined AR expression level in primary and metastatic PCa by analyzing gene array data of 378 primary prostate tumors and 120 metastatic prostate tumors from Oncomine, as well as carrying out immunohistochemical (IHC) staining of 56 prostate cancer samples. Expression of mRNA and protein of AR as well as its target gene prostate‐specific antigen (PSA) was much higher in metastatic prostate tumors than in primary prostate tumors. Knockdown of AR with siRNA or treating with anti‐androgen Casodex reduced migration and invasion ability of C4‐2B PCa cells. Knockdown of AR increased protein expression of E‐cadherin and AR coregulator KAT5 but reduced expression of epithelial‐mesenchymal transition (EMT) marker proteins Slug, Snail, MMP‐2, vimentin, and β‐catenin. Knockdown of KAT5 increased migration of C4‐2B cells, whereas overexpression of KAT5 suppressed cell migration. KAT5 knockdown rescues the suppressive effect of AR knockdown on migration of C4‐2B cells. Gene expression level of AR and KAT5 showed a negative correlation. PCa patients with higher AR expression or lower KAT5 expression correlated with shorter recurrence‐free survival. Our study suggested that elevation of AR expression and AR signaling in prostate tumors promotes PCa metastasis by induction of EMT and reduction of KAT5.

Revisiting the roles of VHR/DUSP3 phosphatase in human diseases

Protein tyrosine phosphatases have long been considered key regulators of biological processes and are therefore implicated in the origins of various human diseases. Heterozygosity, mutations, deletions, and the complete loss of some of these enzymes have been reported to cause neurodegenerative diseases, autoimmune syndromes, genetic disorders, metabolic diseases, cancers, and many other physiological imbalances. Vaccinia H1-related phosphatase, also known as dual-specificity phosphatase 3, is a protein tyrosine phosphatase enzyme that regulates the phosphorylation of the mitogen-activated protein kinase signaling pathway, a central mediator of a diversity of biological responses. It has been suggested that vaccinia H1-related phosphatase can act as a tumor suppressor or tumor-promoting phosphatase in different cancers. Furthermore, emerging evidence suggests that this enzyme has many other biological functions, such as roles in immune responses, thrombosis, hemostasis, angiogenesis, and genomic stability, and this broad spectrum of vaccinia H1-related phosphatase activity is likely the result of its diversity of substrates. Hence, fully identifying and characterizing these substrate-phosphatase interactions will facilitate the identification of pharmacological inhibitors of vaccinia H1-related phosphatase that can be evaluated in clinical trials. In this review, we describe the biological processes mediated by vaccinia H1-related phosphatase, especially those related to genomic stability. We also focus on validated substrates and signaling circuitry with clinical relevance in human diseases, particularly oncogenesis.

Reduced Arginyltransferase 1 is a driver and a potential prognostic indicator of prostate cancer metastasis

Most prostate cancer cases remain indolent for long periods of time, but metastatic progression quickly worsens the prognosis and leads to mortality. However, little is known about what promotes the metastasis of prostate cancer and there is a lack of effective prognostic indicators, making it immensely difficult to manage options for treatment or surveillance. Arginyltransferase 1 (Ate1) is the enzyme mediating post-translational protein arginylation, which has recently been identified as a master regulator affecting many cancer-relevant pathways including stress response, cell cycle checkpoints, and cell migration/adhesion. However, the precise role of Ate1 in cancer remains unknown. In this study, we found the occurrence of metastasis of prostate cancer is inversely correlated with the levels of Ate1 protein and mRNA in the primary tumor. We also found that metastatic prostate cancer cell lines have a reduced level of Ate1 protein compared to non-metastatic cell lines, and that a depletion of Ate1 drives prostate cancer cells towards more aggressive pro-metastatic phenotypes without affecting proliferation rates. Furthermore, we demonstrated that a reduction of Ate1 can result from chronic stress, and that shRNA-reduced Ate1 increases cellular resistance to stress, and drives spontaneous and stress-induced genomic mutations. Finally, by using a prostate orthotropic xenograft mouse model, we found that a reduction of Ate1 was sufficient to enhance the metastatic phenotypes of prostate cancer cell line PC-3 in vivo. Our study revealed a novel role of Ate1 in suppressing prostate cancer metastasis, which has a profound significance for establishing metastatic indicators for prostate cancer, and for finding potential treatments to prevent its metastasis.

The impact of transcription on metabolism in prostate and breast cancers

Metabolic dysregulation is regarded as an important driver in cancer development and progression. The impact of transcriptional changes on metabolism has been intensively studied in hormone-dependent cancers, and in particular, in prostate and breast cancer. These cancers have strong similarities in the function of important transcriptional drivers, such as the oestrogen and androgen receptors, at the level of dietary risk and epidemiology, genetics and therapeutically. In this review, we will focus on the function of these nuclear hormone receptors and their downstream impact on metabolism, with a particular focus on lipid metabolism. We go on to discuss how lipid metabolism remains dysregulated as the cancers progress. We conclude by discussing the opportunities that this presents for drug repurposing, imaging and the development and testing of new therapeutics and treatment combinations.

5'-Chloro-2,2'-dihydroxychalcone and related flavanoids as treatments for prostate cancer

Several flavonoids and their biosynthetic precursor chalcones were designed and synthesized to improve the biological effects of the lead compound 2'-hydroxyflavonone against androgen receptor (AR)-dependent transcriptional stimulation. Newly synthesized chalcones 19 and 26 suppressed AR-dependent transcription as well as DHT-dependent growth stimulation at a low micromolar level. These compounds were also effective against ligand-independent constitutively active mutant AR derived from castration-resistant PCa (CRPC). Compounds 19 and 26 showed broad spectrum antiproliferative activity at 5-10 μM against multiple tumor cell lines including androgen-independent and taxane-resistant prostate cancer as well as a multidrug-resistant subline. Mode of action studies suggested that 19 induced sub-G1 accumulation in PC-3 cells by disrupting the microtubule network without affecting cell cycle progression. Furthermore, the in vivo effectiveness of chalcone 19 was confirmed in a xenograft model antitumor assay. Thus, chalcone 19 has the potential to be a bifunctional lead for treatment of AR-dependent PCa at lower doses as well as AR-independent PCa, including CRPC, at higher doses.

Survivin and Sox9: Potential Stem Cell Markers in Canine Normal, Hyperplastic, and Neoplastic Canine Prostate

Canine prostatic carcinoma is a relevant model for human prostatic carcinoma. Survivin is proposed as a biomarker of malignancy in human prostatic cancer. Sox9 is a stem cell marker required for prostate development and expressed in several adult tissues. The aims of the present study were to evaluate the patterns and expression levels of 2 putative stem cell markers, survivin and Sox9, in canine benign prostatic hyperplasia (BPH) and prostatic carcinoma to investigate their potential as stem cell markers. Immunohistochemistry with specific antibodies was performed on 3 samples of normal prostate gland, 18 samples of canine BPH, and 16 samples of prostatic carcinoma. The basal cell layer of normal and hyperplastic prostatic lobules had nuclear Sox9 immunolabeling and nuclear and rarely cytoplasmic survivin immunostaining, identifying them as potential stem cell markers. Significantly more frequent survivin and Sox9 expression (≥10% of nuclei) was observed in prostatic carcinoma as compared with BPH. The potential coexpression of survivin with Sox9, androgen receptor, and p63 was also investigated in selected BPH and prostatic carcinoma cases with immunofluorescence, and a partial colocalization was observed. Results indicate that Sox9 and survivin could be considered markers of stemness in canine prostate cells. Given its role in proliferation, cells in the basal cell layer with nuclear survivin expression are likely to be transit-amplifying cells that maintain some stem cell proprieties.

Cytotoxic effect of Kalanchoe flammea and induction of intrinsic mitochondrial apoptotic signaling in prostate cancer cells

ETHNOPHARMACOLOGICAL IMPORTANCE

Kalanchoe flammea Stapf (Crassulaceae) is a medicinal plant grown in the South of Mexico (State of Tabasco), which is commonly used in traditional medicine for the treatment of fever, wounds, inflammation, and cancer.

AIM OF THE STUDY

To establish the potential of K. flammea for the treatment of prostate cancer, evaluating its cytotoxic activity, its probable mechanism of action, and carrying out some toxicological safety studies.

MATERIALS AND METHODS

The cytotoxic activity of the ethyl acetate extract of K. flammea (Kf-EtOAc) was evaluated in several cell lines of prostate cancer by MTT viability assay. The cellular death mechanism was studied by evaluating the translocation of phosphatidylserine (Annexin V); overproduction of reactive oxygen species [2'-7'-Dichlorodihydrofluorescein diacetate (DCFH-DA) assay]; release of Cytochrome C; activation of caspase-3 and -9, and regulation of Bcl-2, XIAP, and PKCε proteins by Western Blot analysis. For the evaluation of the safety of Kf-EtOAc, the Ames test, Micronucleus assay, and acute toxicity study were determined.

RESULTS

Kf-EtOAc exhibited selective cytotoxic activity against prostate cell lines as follows: PC-3, LNCaP, and PrEC (IC₅₀ = 1.36 ± 0.05; 2.06 ± 0.02, and 127.05 ± 0.07 μg/mL, respectively). The F82-P2 fraction (rich in coumaric acid and palmitic acid) obtained by bioassay-guided fractionation of Kf-EtOAc also demonstrated selective cytotoxic activity against PC-3 cells (IC₅₀ = 1.05 ± 0.06 μg/mL). Kf-EtOAc induces apoptosis by the intrinsic pathway; this mechanism of cell death was confirmed after observing that the extract produces phosphatidylserine translocation, overproduction of reactive oxygen species, release of Cytochrome C at mitochondrial level, and activation of caspase-3 and -9. It was also observed that Kf-EtOAc produces significant downregulation of apoptosis-related proteins Bcl-2, XIAP, and PKCε and induces DNA fragmentation and cell cycle arrest. In addition, Kf-EtOAc is non-genotoxic in vitro by Ames test and non-genotoxic in vivo by Micronucleus assay, and no signs of toxicity or death were reported after the administration of a single acute exposure of 2000 mg/kg.

CONCLUSION

K. flammea is a potential candidate for the development of new drugs for the treatment of prostate cancer. However, to propose their use in clinical trials, additional studies are required to understand their pharmacokinetic behavior, as well as the development of a suitable pharmaceutical form.

Simultaneous Delivery of Electrostatically Complexed Multiple Gene-Targeting siRNAs and an Anticancer Drug for Synergistically Enhanced Treatment of Prostate Cancer

Simultaneous silencing of multiple apoptosis-related genes is an attractive approach to treat cancer. In this article, we present a multiple gene-targeting siRNA/drug delivery system for prostate cancer treatment with a high efficiency. Bcl-2, survivin, and androgen receptor genes involved in the cell apoptosis pathways were chosen as silencing targets with three different siRNAs. The colloidal nanocomplex delivery system (<10 nm in size) was formulated electrostatically between anionic siRNAs and a cationic drug (BZT), followed by encapsulation with the Pluronic F-68 polymer. The formulated nanocomplex system exhibited sufficient stability against nuclease-induced degradation, leading to successful intracellular delivery for the desired therapeutic performance. Silencing of targeted genes and apoptosis induction were evaluated in vitro on human prostate LNCaP-LN3 cancer cells by using various biological analysis tools (e.g., real-time PCR, MTT cell viability test, and flow cytometry). It was demonstrated that when the total loaded siRNA amounts were kept the same in the nanocomplexes, the simultaneous silencing of triple genes with co-loaded siRNAs (i.e., Bcl-2, survivin, and AR-targeting siRNAs) enhanced BZT-induced apoptosis of cancer cells more efficiently than the silencing of each single gene alone, offering a novel way of improving the efficacy of gene therapeutics including anticancer drug.

Combination Therapies Using Metformin and/or Valproic Acid in Prostate Cancer: Possible Mechanistic Interactions

Prostate cancer (PCa) is the most frequent cancer in men. The evolution from local PCa to castration-resistant PCa, an end-stage of disease, is often associated with changes in genes such as p53, androgen receptor, PTEN, and ETS gene fusion products. Evidence is accumulating that repurposing of metformin (MET) and valproic acid (VPA) either when used alone, or in combination, with another therapy, could potentially play a role in slowing down PCa progression. This review provides an overview of the application of MET and VPA, both alone and in combination with other drugs for PCa treatment, correlates the responses to these drugs with common molecular changes in PCa, and then describes the potential for combined MET and VPA as a systemic therapy for prostate cancer, based on potential interacting mechanisms.

Clinical Development of Darolutamide: A Novel Androgen Receptor Antagonist for the Treatment of Prostate Cancer

Prostate cancer (PC) is the second most common cancer in men and is the fifth leading cause of cancer-related deaths among men. Androgen receptor (AR) signaling plays a key role in PC tumor growth and progression, with androgens stimulating PC proliferation and survival. Castration-resistant PC (CRPC) is characterized by increasing levels of prostate-specific antigen or radiographic progression despite androgen-deprivation therapy (ADT). In most patients, castration resistance results from aberrations in AR or the AR signaling pathway. Up to one-third of patients with localized high-risk PC will have disease progression on local therapy and develop CRPC. This review summarizes the key clinical data, including ongoing trials, for hormonal therapies in CRPC and provides an overview of the clinical development of darolutamide, a novel, nonsteroidal AR antagonist currently in phase III development for the treatment of nonmetastatic CRPC and metastatic hormone-sensitive PC. In phase I/II trials, darolutamide has demonstrated a favorable safety profile, antitumor activity, and significant decreases in prostate-specific antigen in patients with metastatic CRPC. In the phase III ARAMIS (NCT02200614; A Multinational, Randomized, Double-Blind, Placebo-Controlled, Phase III Efficacy and Safety Study of Darolutamide [ODM-201] in Men With High-Risk Non-metastatic Castration-Resistant Prostate Cancer) study, metastasis-free survival is being evaluated in men with nonmetastatic CRPC who will receive ADT in combination with darolutamide or placebo. The ARASENS (NCT02799602; A Randomized, Double-Blind, Placebo Controlled Phase III Study of Darolutamide [ODM-201] Versus Placebo in Addition to Standard Androgen Deprivation Therapy and Docetaxel in Patients With Metastatic Hormone Sensitive Prostate Cancer) study is a placebo-controlled trial assessing whether the addition of darolutamide to ADT and docetaxel significantly prolongs overall survival in men with metastatic hormone-sensitive PC.

Therapeutic Potential of Leelamine, a Novel Inhibitor of Androgen Receptor and Castration-Resistant Prostate Cancer

Clinical management of castration-resistant prostate cancer (CRPC) resulting from androgen deprivation therapy remains challenging. CRPC is driven by aberrant activation of androgen receptor (AR) through mechanisms ranging from its amplification, mutation, post-translational modification, and expression of splice variants (e.g., AR-V7). Herein, we present experimental evidence for therapeutic vulnerability of CRPC to a novel phytochemical, leelamine (LLM), derived from pine tree bark. Exposure of human prostate cancer cell lines LNCaP (an androgen-responsive cell line with mutant AR), C4-2B (an androgen-insensitive variant of LNCaP), and 22Rv1 (a CRPC cell line with expression of AR-Vs), and a murine prostate cancer cell line Myc-CaP to plasma achievable concentrations of LLM resulted in ligand-dependent (LNCaP) and ligand-independent (22Rv1) growth inhibition in vitro that was accompanied by downregulation of mRNA and/or protein levels of full-length AR as well as its splice variants, including AR-V7. LLM treatment resulted in apoptosis induction in the absence and presence of R1881. In silico modeling followed by luciferase reporter assay revealed a critical role for noncovalent interaction of LLM with Y739 in AR activity inhibition. Substitution of the amine group with an isothiocyanate functional moiety abolished AR and cell viability inhibition by LLM. Administration of LLM resulted in 22Rv1 xenograft growth suppression that was statistically insignificant but was associated with a significant decrease in Ki-67 expression, mitotic activity, expression of full-length AR and AR-V7 proteins, and secretion of PSA. This study identifies a novel chemical scaffold for the treatment of CRPC. Mol Cancer Ther; 17(10); 2079-90. ©2018 AACR.

RNA sequencing reveals upregulation of a transcriptomic program associated with stemness in metastatic prostate cancer cells selected for taxane resistance

Patients with metastatic castration-resistant prostate cancer (mCRPC) develop resistance to conventional therapies including docetaxel (DTX). Identifying molecular pathways underlying DTX resistance is critical for developing novel combinatorial therapies to prevent or reverse this resistance. To identify transcriptomic signatures associated with acquisition of chemoresistance we profiled gene expression in DTX-sensitive and -resistant mCRPC cells using RNA sequencing (RNA-seq). PC3 and DU145 cells were selected for DTX resistance and this phenotype was validated by immunoblotting using DTX resistance markers (e.g. clusterin, ABCB1/P-gp, and LEDGF/p75). Overlapping genes differentially regulated in the DTX-sensitive and -resistant cells were ranked by Gene Set Enrichment Analysis (GSEA) and validated to correlate transcript with protein expression. GSEA revealed that genes associated with cancer stem cells (CSC) (e.g., NES, TSPAN8, DPPP, DNAJC12, and MYC) were highly ranked and comprised 70% of the top 25 genes differentially upregulated in the DTX-resistant cells. Established markers of epithelial-to-mesenchymal transition (EMT) and CSCs were used to evaluate the stemness of adherent DTX-resistant cells (2D cultures) and tumorspheres (3D cultures). Increased formation and frequency of cells expressing CSC markers were detected in DTX-resistant cells. DU145-DR cells showed a 2-fold increase in tumorsphere formation and increased DTX resistance compared to DU145-DR 2D cultures. These results demonstrate the induction of a transcriptomic program associated with stemness in mCRPC cells selected for DTX resistance, and strengthen the emerging body of evidence implicating CSCs in this process. In addition, they provide additional candidate genes and molecular pathways for potential therapeutic targeting to overcome DTX resistance.

GABA promotes gastrin-releasing peptide secretion in NE/NE-like cells: Contribution to prostate cancer progression

In prostate cancer (PCa), neuroendocrine cells (NE) have been associated with the progression of the disease due to the secretion of neuropeptides that are capable of diffusing and influence surrounding cells. The GABAergic system is enriched in NE-like cells, and contributes to PCa progression. Additionally, γ-aminobutyric acid (GABA) stimulates the secretion of gastrin-releasing peptide (GRP) in peripheral organs. For the first time, in this study we show the role of GABA and GABA_B receptor 1 (GABBR1) expression in GRP secretion in NE-like prostate cancer cells. We demonstrated an increase in GRP levels in NE-like cell medium treated with GABA_B receptor agonist. Moreover, the blocking of this receptor inhibited GABA-induced GRP secretion. The invasive potential of PC3 cells was enhanced by either GRP or conditioned medium of NE-like cells treated with GABA. Additionally, we confirmed a positive correlation between GABA and GRP levels in the serum of PCa patients with NE markers. Finally, using public available data sets, we found a negative correlation between GABBR1 and androgen receptor (AR) expression, as well as a strong positive correlation between GABBR1 and enolase 2. These results suggest that GABA via GABBR1 induces GRP secretion in NE like cells involved in PCa progression.

Testosterone, prolactin, and oncogenic regulation of the prostate gland. A new concept: Testosterone-independent malignancy is the development of prolactin-dependent malignancy!

Hormone-independent malignancy is a major issue of morbidity and deaths that confronts prostate cancer. Despite decades of research, the oncogenic and hormonal implications in the development and progression of prostate malignancy remain mostly speculative. This is largely due to the absence and/or lack of consideration by contemporary clinicians and biomedical investigators regarding the established implications of the co-regulation of testosterone and prolactin in the development, maintenance, metabolism and functions of the prostate gland. Especially relevant is the major metabolic function of production of high levels of citrate by the peripheral zone acinar epithelial cells. Citrate production, along with growth and proliferation by these cells, is regulated by co-existing testosterone and prolactin signaling pathways; and by the oncogenic down-regulation of ZIP1 transporter/zinc/citrate in the development of malignancy. These relationships had not been considered in the issues of hormonedependent malignancy. This review provides the relevant background that has established the dual role of testosterone and prolactin regulation of the prostate gland; which is essential to address the implications in the oncogenic development and progression of hormone-dependent malignancy. The oncogenic factor along with testosterone-dependent and prolactin-dependent relationships leads to the plausible concept that androgen ablation for the treatment of testosteronedependent malignancy results in the development of prolactindependent malignancy; which is testosterone-independent malignancy. Consequently, both testosterone ablation and prolactin ablation are required to prevent and/or abort terminal hormonedependent prostate cancer.

Taxane resistance in castration-resistant prostate cancer: mechanisms and therapeutic strategies

Despite its good initial response and significant survival benefit in patients with castration-resistant prostate cancer (CRPC), taxane therapy inevitably encounters drug resistance in all patients. Deep understandings of taxane resistant mechanisms can significantly facilitate the development of new therapeutic strategies to overcome taxane resistance and improve CRPC patient survival. Multiple pathways of resistance have been identified as potentially crucial areas of intervention. First, taxane resistant tumor cells typically have mutated microtubule binding sites, varying tubulin isotype expression, and upregulation of efflux transporters. These mechanisms contribute to reducing binding affinity and availability of taxanes. Second, taxane resistant tumors have increased stem cell like characteristics, indicating higher potential for further mutation in response to therapy. Third, the androgen receptor pathway is instrumental in the proliferation of CRPC and multiple hypotheses leading to this pathway reactivation have been reported. The connection of this pathway to the AKT pathway has received significant attention due to the upregulation of phosphorylated AKT in CRPC. This review highlights recent advances in elucidating taxane resistant mechanisms and summarizes potential therapeutic strategies for improved treatment of CRPC.

The interplay between AR, EGF receptor and MMP-9 signaling pathways in invasive prostate cancer

Background

Metastatic Prostate cancer (PCa) cells have gained survival and invasive advantages. Epidermal growth factor (EGF) receptor is a receptor tyrosine kinase, which may mediate signalling to promote progression and invasion of various cancers. In this study, we uncovered the molecular mechanisms underlying the interconnection among the androgen receptor (AR), matrix metalloproteinase-9 (MMP9) and EGFR in promoting PCa progression.

Methods

Immunohistochemical analysis of the tissue microarrays consisting of primary and metastatic PCa tissues was performed. The clinical importance of EGFR and its association with survivals were analyzed using three cohorts from MSKCC Prostate Oncogenome Project dataset (For primary tumors, n = 181; for metastatic tumors n = 37) and The Cancer Genome Atlas Prostate Adenocarcinoma Provisional dataset (n = 495). Targeted overexpression or inhibition of the proteins of interests was introduced into PCa cell lines. Treatment of PCa cell lines with the compounds was conducted. Immunoblot analysis was performed.

Results

We showed that AR, MMP-9 and EGFR are interconnect factors, which may cooperatively promote PCa progression. Altered EGFR expression was associated with poor disease-free survival in PCa patients. Induced overexpression of AR led to an increase in the expression of EGFR, p-GSK-3β and decrease in p27 expression in PCa cell lines in the presence of androgen stimulation. Overexpression of MMP9 significantly induced EGFR expression in PCa cells. Inhibition of PIP5K1α, a lipid kinase that acts upstream of PI3K/AKT greatly reduced expressions of AR, MMP-9 and EGFR.

Conclusions

Our findings also suggest that PCa cells may utilize AR, EGFR and MMP-9 pathways in androgen-dependent as well as in castration-resistant conditions. Our data suggest a new therapeutic potential to block cancer metastasis by targeting AR, EGFR and MMP-9 pathways in subsets of PCa patients.

V-ATPase-dependent repression of androgen receptor in prostate cancer cells

Prostate Cancer (PCa) is the most commonly diagnosed cancer and the third leading cause of death for men in the United States. Suppression of androgen receptor (AR) expression is a desirable mechanism to manage PCa. Our studies showed that AR expression was reduced in LAPC4 and LNCaP PCa cell lines treated with nanomolar concentrations of the V-ATPase inhibitor concanamycin A (CCA). This treatment decreased PSA mRNA levels, indicative of reduced AR activity. V-ATPase-dependent repression of AR expression was linked to defective endo-lysosomal pH regulation and reduced AR expression at the transcriptional level. CCA treatment increased the protein level and nuclear localization of the alpha subunit of the transcription factor HIF-1 (HIF-1α) in PCa cells via decreased hydroxylation and degradation of HIF-1α. The addition of iron (III) citrate restored HIF-1α hydroxylation and decreased total HIF-1α levels in PCa cells treated with CCA. Moreover, iron treatment partially rescued CCA-mediated AR repression. Dimethyloxalylglycine (DMOG), which prevents HIF-1α degradation independently of V-ATPase, also decreased AR levels, supporting our hypothesis that HIF-1α serves as a downstream mediator in the V-ATPase-AR axis. We propose a new V-ATPase-dependent mechanism to inhibit androgen receptor expression in prostate cancer cells involving defective endosomal trafficking of iron and the inhibition of HIF-1 α-subunit turnover.

A Novel Use of Olaparib for the Treatment of Metastatic Castration-Recurrent Prostate Cancer

Although mortality from prostate cancer has declined over the past 20 years as a result of early detection and treatment, the 5-year survival rate for men with prostate cancer who develop metastatic disease is only 29%. Current treatment options for metastatic castration-recurrent prostate cancer (mCRPC) are associated with toxicity and a limited durable response; therefore, additional lines of efficacious and minimally toxic therapy are needed. Olaparib, a poly(adenosine 5'-diphosphate) ribose polymerase (PARP) inhibitor, received a U.S. Food and Drug Administration breakthrough therapy designation in January 2016 for the treatment of patients with BRCA1/2 or ATM gene-mutated mCRPC based on results of a compelling phase II trial of olaparib in patients with advanced castration-resistant prostate cancer (TOPARP-A). This study found that men with mCRPC and genetic mutations in DNA damage repair genes had an overall response rate of nearly 90% with olaparib treatment. In this review, we describe current therapies for mCRPC, the rationale for anti-PARP therapies, the pharmacology of olaparib for prostate cancer, clinical trials of olaparib for mCRPC, our clinical experience with olaparib for prostate cancer at a comprehensive cancer center, and future directions of olaparib for the treatment of mCRPC. Olaparib may constitute a promising treatment to prolong survival in patients with mCRPC, with an acceptable adverse effect profile. As the role of PARP inhibition in prostate cancer and other malignancies becomes further elucidated, olaparib may be shown to be beneficial for other patient populations.

Heteronemin, a Marine Sesterterpenoid-Type Metabolite, Induces Apoptosis in Prostate LNcap Cells via Oxidative and ER Stress Combined with the Inhibition of Topoisomerase II and Hsp90

Heteronemin, a marine sesterterpenoid-type natural product, possesses diverse bioactivities, especially antitumor effect. Accumulating evidence shows that heteronemin may act as a potent anticancer agent in clinical therapy. To fully understand the antitumor mechanism of heteronemin, we further explored the precise molecular targets in prostate cancer cells. Initially, heteronemin exhibited potent cytotoxic effect against LNcap and PC3 prostate cancer cells with IC₅₀ 1.4 and 2.7 &mu;M after 24 h, respectively. In the xenograft animal model, the tumor size was significantly suppressed to about 51.9% in the heteronemin-treated group in comparison with the control group with no significant difference in the mice body weights. In addition, the results of a cell-free system assay indicated that heteronemin could act as topoisomerase II (topo II) catalytic inhibitor through the elimination of essential enzymatic activity of topoisomerase II&alpha; expression. We found that the use of heteronemin-triggered apoptosis by 20.1⁻68.3%, caused disruption of mitochondrial membrane potential (MMP) by 66.9⁻99.1% and promoted calcium release by 1.8-, 2.0-, and 2.1-fold compared with the control group in a dose-dependent manner, as demonstrated by annexin-V/PI, rhodamine 123 and Fluo-3 staining assays, respectively. Moreover, our findings indicated that the pretreatment of LNcap cells with an inhibitor of protein tyrosine phosphatase (PTPi) diminished growth inhibition, oxidative and Endoplasmic Reticulum (ER) stress, as well as activation of Chop/Hsp70 induced by heteronemin, suggesting PTP activation plays a crucial rule in the cytotoxic activity of heteronemin. Using molecular docking analysis, heteronemin exhibited more binding affinity to the N-terminal ATP-binding pocket of Hsp90 protein than 17-AAG, a standard Hsp90 inhibitor. Finally, heteronemin promoted autophagy and apoptosis through the inhibition of Hsp 90 and topo II as well as PTP activation in prostate cancer cells. Taken together, these multiple targets present heteronemin as an interesting candidate for its future development as an antiprostatic agent.

Elevated phospholipase D activity in androgen-insensitive prostate cancer cells promotes both survival and metastatic phenotypes

Prostate cells are hormonally driven to grow and divide. Typical treatments for prostate cancer involve blocking activation of the androgen receptor by androgens. Androgen deprivation therapy can lead to the selection of cancer cells that grow and divide independently of androgen receptor activation. Prostate cancer cells that are insensitive to androgens commonly display metastatic phenotypes and reduced long-term survival of patients. In this study we provide evidence that androgen-insensitive prostate cancer cells have elevated PLD activity relative to the androgen-sensitive prostate cancer cells. PLD activity has been linked with promoting survival in many human cancer cell lines; and consistent with the previous studies, suppression of PLD activity in the prostate cancer cells resulted in apoptotic cell death. Of significance, suppressing the elevated PLD activity in androgen resistant prostate cancer lines also blocked the ability of these cells to migrate and invade Matrigel™. Since survival signals are generally an early event in tumorigenesis, the apparent coupling of survival and metastatic phenotypes implies that metastasis is an earlier event in malignant prostate cancer than generally thought. This finding has implications for screening strategies designed to identify prostate cancers before dissemination.

Diverse AR-V7 cistromes in castration-resistant prostate cancer are governed by HoxB13

The constitutively active androgen receptor (AR) splice variant 7 (AR-V7) plays an important role in the progression of castration-resistant prostate cancer (CRPC). Although biomarker studies established the role of AR-V7 in resistance to AR-targeting therapies, how AR-V7 mediates genomic functions in CRPC remains largely unknown. Using a ChIP-exo approach, we show AR-V7 binds to distinct genomic regions and recognizes a full-length androgen-responsive element in CRPC cells and patient tissues. Remarkably, we find dramatic differences in AR-V7 cistromes across diverse CRPC cells and patient tissues, regulating different target gene sets involved in CRPC progression. Surprisingly, we discover that HoxB13 is universally required for and colocalizes with AR-V7 binding to open chromatin across CRPC genomes. HoxB13 pioneers AR-V7 binding through direct physical interaction, and collaborates with AR-V7 to up-regulate target oncogenes. Transcriptional coregulation by HoxB13 and AR-V7 was further supported by their coexpression in tumors and circulating tumor cells from CRPC patients. Importantly, HoxB13 silencing significantly decreases CRPC growth through inhibition of AR-V7 oncogenic function. These results identify HoxB13 as a pivotal upstream regulator of AR-V7-driven transcriptomes that are often cell context-dependent in CRPC, suggesting that HoxB13 may serve as a therapeutic target for AR-V7-driven prostate tumors.

AIRE promotes androgen-independent prostate cancer by directly regulating IL-6 and modulating tumor microenvironment

Early stage prostate cancers are dependent on androgens for their growth and survival and androgen withdrawal causes them to regress. Progressive prostate cancers eventually acquire androgen independence rendering anti-androgen therapy ineffective. However, the factors leading to this have not been adequately addressed. This study shows that AIRE finds differential expression in androgen-dependent and -independent prostate cancer cells. AIRE expression is more in androgen-independent cells due to its regulation by transcription factor Elk-1. These enhanced levels of AIRE modulate the prostate tumor microenvironment by transcriptionally activating a malignancy gene IL-6 in androgen-independent cells. Additionally, AIRE prevents the cancer cells from anticancer drug-induced death and enhances their invasiveness. Moreover, AIRE by modulating the cytokine milieu skews the tumor-associated macrophage polarization towards M2 phenotype with increased CD206 and CD163 expression. Subcutaneous mouse model of prostate cancer revealed AIRE^+/+ mice forming a palpable tumor and presents lymphadenopathy however, only a small benign tumor is observed in AIRE^−/− mice and lymph nodes appear normal in size. In conclusion, our findings suggest AIRE as a probable factor in promoting prostate cancer progression.

The microbiome in prostate inflammation and prostate cancer

BACKGROUND

The human microbiome may influence prostate cancer initiation and/or progression through both direct and indirect interactions. To date, the majority of studies have focused on direct interactions including the influence of prostate infections on prostate cancer risk and, more recently, on the composition of the urinary microbiome in relation to prostate cancer. Less well understood are indirect interactions of the microbiome with prostate cancer, such as the influence of the gastrointestinal or oral microbiota on pro- or anti-carcinogenic xenobiotic metabolism, and treatment response.

METHODS

We review the literature to date on direct and indirect interactions of the microbiome with prostate inflammation and prostate cancer.

RESULTS

Emerging studies indicate that the microbiome can influence prostate inflammation in relation to benign prostate conditions such as prostatitis/chronic pelvic pain syndrome and benign prostatic hyperplasia, as well as in prostate cancer. We provide evidence that the human microbiome present at multiple anatomic sites (urinary tract, gastrointestinal tract, oral cavity, etc.) may play an important role in prostate health and disease.

CONCLUSIONS

In health, the microbiome encourages homeostasis and helps educate the immune system. In dysbiosis, a systemic inflammatory state may be induced, predisposing remote anatomical sites to disease, including cancer. The microbiome's ability to affect systemic hormone levels may also be important, particularly in a disease such as prostate cancer that is dually affected by estrogen and androgen levels. Due to the complexity of the potential interconnectedness between prostate cancer and the microbiome, it is vital to further explore and understand the relationships that are involved.