Castration-resistant prostate cancer: locking up the molecular escape routes

Evaluation of AR, AR-V7, and p160 family as biomarkers for prostate cancer: insights into the clinical significance and disease progression

PURPOSE

To assess the role of the p160 family, AR, and AR-V7 in different initial presentations of prostate cancer and their association with clinical endpoints related to tumor progression.

METHODS

The study sample comprises 155 patients who underwent radical prostatectomy and 11 healthy peripheral zone biopsies as the control group. Gene expression was quantified by qPCR from the tissue specimens. The statistical analysis investigated correlations between gene expression levels, associations with disease presence, and clinicopathological features. Additionally, ROC curves were applied for distinct PCa presentations, and time-to-event analysis was used for clinical endpoints.

RESULTS

The AR-V7 diagnostic performance for any PCa yielded an AUC of 0.77 (p < 0.05). For locally advanced PCa, the AR-V7 AUC was 0.65 (p < 0.05). Moreover, the metastasis group had a higher expression of SRC-1 than the non-metastatic group (p < 0.05), showing a shorter time to metastasis in the over-expressed group (p = 0.005). Patients with disease recurrence had super-expression of AR levels (p < 0.0005), with a shorter time-to-recurrence in the super-expression group (p < 0.0001).

CONCLUSION

Upregulation of SRC-1 indicates a higher risk of progression to metastatic disease in a shorter period, which warrants further research to be applied as a clinical tool. Additionally, AR may be used as a predictor for PCa recurrence. Furthermore, AR-V7 may be helpful as a diagnostic tool for PCa and locally advanced cancer, comparable with other investigated tools.

EGFR-mediated hyperacetylation of tubulin induced docetaxel resistance by downregulation of HDAC6 and upregulation of MCAK and PLK1 in prostate cancer cells

Docetaxel-based chemotherapy has generally been considered as one of the effective treatments for castration-resistant prostate cancer (PCa). However, clinical treatment with docetaxel often encounters a number of undesirable effects, including drug resistance. Tubulin isoforms have been previously examined for their resistance to docetaxel in many cancers, but their real mechanisms remained unclear. In this study, a series of docetaxel-resistant PC/DX cell sublines were established by chronically exposing PC3 to progressively increased concentrations of docetaxel. Western blotting results showed significantly higher expression of acetyl-tubulin, α-tubulin, β-tubulin, γ-tubulin, and βIII-tubulin in PC/DX25 than in parental PC3 cells. PC/DX25 with greater resistance to docetaxel had higher levels of acetyl-tubulin and mitotic centromere-associated kinesin (MCAK) than PC3 cells. This study found that docetaxel induced the expression of acetyl-tubulin and MCAK in PC3 cells at a dose- and time-dependent manner. Both mRNA and protein levels of histone deacetylase 6 (HDAC6) were significantly decreased in PC/DX25 compared with PC3 cells. PC3 increased the resistance to docetaxel by HDAC6 knockdown and Tubastatin A (HDAC6 inhibitor). Conversely, PC/DX25 reversed the sensitivity to docetaxel by MCAK knockdown. Notably, flow cytometry analysis revealed that MCAK knockdown induced significantly sub G1 fraction in PC/DX cells. Overexpression of polo-like kinase-1 increased the cell survival rate and resistance to docetaxel in PC3 cells. Moreover, epidermal growth factor receptor (EGFR) activation induced the upregulation of acetyl-tubulin in docetaxel-resistant PCa cells. These findings demonstrated that the EGFR-mediated upregulated expression of acetyl-tubulin played an important role in docetaxel-resistant PCa.

Clinical and molecular significance of the RNA m6A methyltransferase complex in prostate cancer

N⁶-methyladenosine (m⁶A) is the most abundant internal mRNA modification and is dynamically regulated through distinct protein complexes that methylate, demethylate, and/or interpret the m⁶A modification. These proteins, and the m⁶A modification, are involved in the regulation of gene expression, RNA stability, splicing and translation. Given its role in these crucial processes, m⁶A has been implicated in many diseases, including in cancer development and progression. Prostate cancer (PCa) is the most commonly diagnosed non-cutaneous cancer in men and recent studies support a role for m⁶A in PCa. Despite this, the literature currently lacks an integrated analysis of the expression of key components of the m⁶A RNA methyltransferase complex, both in PCa patients and in well-established cell line models. For this reason, this study used immunohistochemistry and functional studies to investigate the mechanistic and clinical significance of the METTL3, METTL14, WTAP and CBLL1 components of the m⁶A methyltransferase complex in PCa specimens and cell lines. Expression of METTL3 and CBLL1, but not METTL14 and WTAP, was associated with poorer PCa patient outcomes. Expression of METTL3, METTL14, WTAP and CBLL1 was higher in PCa cells compared with non-malignant prostate cells, with the highest expression seen in castrate-sensitive, androgen-responsive PCa cells. Moreover, in PCa cell lines, expression of METTL3 and WTAP was found to be androgen-regulated. To investigate the mechanistic role(s) of the m⁶A methyltransferase complex in PCa cells, short hairpin RNA (shRNA)-mediated knockdown coupled with next generation sequencing was used to determine the transcriptome-wide roles of METTL3, the catalytic subunit of the m⁶A methyltransferase complex. Functional depletion of METTL3 resulted in upregulation of the androgen receptor (AR), together with 134 AR-regulated genes. METTL3 knockdown also resulted in altered splicing, and enrichment of cell cycle, DNA repair and metabolic pathways. Collectively, this study identified the functional and clinical significance of four essential m⁶A complex components in PCa patient specimens and cell lines for the first time. Further studies are now warranted to determine the potential therapeutic relevance of METTL3 inhibitors in development to treat leukaemia to benefit patients with PCa.

The role of testosterone in men's health: is it time for a new approach?

PURPOSE

Because of many unanswered questions regarding men's health, a literature review was performed to better understand the role of testosterone and testosterone replacement therapy (TRT) in the management of hypogonadism and aging related prostate gland diseases (ARPGD) including prostate cancer (PCa) and benign prostatic hyperplasia (BPH) with lower urinary tract symptoms (LUTS).

METHODS

The PubMed database was screened for pertinent peer reviewed articles published during the last four decades that culminated in the positions and recommendations in this paper.

RESULTS

Hypogonadism seriously impacts men's health, and the diagnosis remains controversial. The incidence of ARPGD is projected to increase worldwide and treatment still has significant limitations. There is compelling evidence that lower, not higher, testosterone levels trigger the development of PCa and BPH through androgen receptor over-expression. TRT was found to be safe and effective in treating hypogonadism including in PCa survivors and those harboring PCa. There is also evidence that TRT might reduce the incidence and prevalence of ARPGD.

CONCLUSIONS AND RECOMMENDATIONS

This review synthesizes a wide-ranging compendium of basic science and clinical research that strongly encourages altering the present approach to diagnosing and treating men with hypogonadism and ARPGD. These findings underscore the importance of avoiding significant testosterone decline and support the use of TRT. Ten recommendations are offered as a framework for the way forward. It is now time for clinicians, payers, researchers, funding agencies, professional associations, and patient advocacy groups to embrace this new paradigm to increase longevity and improve the quality of life.

Phase I clinical trial of HC-1119 soft capsule in Chinese healthy adult male subjects: Pharmacokinetics and safety of single-dose proportionality and effects of food

BACKGROUND

Preclinical studies showed that HC-1119, a deuterated version of enzalutamide, could competitively inhibit androgen binding to androgen receptor by blocking the transmission of androgen receptor signaling pathway as enzalutamide, inducing apoptosis of prostate cancer cells and reducing the proliferation of prostate cancer cells. Animal pharmacokinetic studies also show that deuterization of enzalutamide as HC-1119 could retain the basic properties of mother drug, increases the stability of compounds to metabolic enzymes and the drug exposure in vivo, prolong the half-life and reduce the production of metabolites, which may lead to a better efficacy and safety of HC-1119 compared with enzalutamide.

METHODS

To evaluate the pharmacokinetics and safety of HC-1119 and the effects of food on pharmacokinetics in healthy adult Chinese men after single-dose administration of HC-1119. A total of 47 Chinese healthy adult male subjects received HC-1119 soft capsule at a single oral dose of 40, 80, or 160 mg followed on fasting or 160 mg after high-fat meal respectively. HC-1119 prototype and its metabolites M1 and M2 in plasma were collected individually in a total 23 time points. Pharmacokinetics were determined by sensitive LC/MS/MS for dose-proportionality study.

RESULTS

In subjects taking HC-1119 soft capsules on fasting, C_max of HC-1119 prototype increased dose-dependently. Either C_max and AUC_0-∞ of M1 or C_max of M2 showed statistically significant difference. Dose-proportionality evaluation showed linear pharmacokinetic characteristics in C_max of HC-1119 prototype, C_max and AUC_0-∞ of M2 in dose range of 40-160 mg. C_max of HC-1119 was significantly different between the two groups as 160 mg HC-1119 on fasting or after a high-fat diet respectively, while the other parameter were not. HC-1119 and its metabolites M1 and M2 showed a linear dynamic trend.

CONCLUSIONS

HC-1119 is expected to have lower clinical dose than the similar drug enzalutamide. The absorption of HC-1119 and the main pharmacokinetic parameters of HC-1119 and its metabolites M1 and M2 were not affected by high-fat diet. The clinical application of HC-1119 soft capsule in the later stage can be recommended for both fasting and postprandial. The safety and tolerance were good in this population.

The Impact of Palliative Transurethral Resection of the Prostate on the Prognosis of Patients With Bladder Outlet Obstruction and Metastatic Prostate Cancer: A Population-Matched Study

Objective: This study aimed to evaluate the survival outcomes of patients with bladder outlet obstruction (BOO) and metastatic prostate cancer (mPCa) after having a palliative transurethral resection of the prostate (pTURP) surgery. Methods: We identified patients with mPCa between 2004 and 2016 in the Surveillance, Epidemiology, and End Results (SEER) database. Patients who received pTURP and non-surgical therapy were identified. A propensity-score matching was introduced to balance the covariate. Kaplan-Meier analysis and COX regression were conducted to evaluate the overall survival (OS) and cancer-specific survival (CSS) outcomes. Results: A total of 36,003 patients were identified; 2,823 of them were in the pTURP group and 33,180 were in the non-surgical group. The survival curves of the overall cohort showed that the pTURP group was associated with worse outcomes in both OS (HR: 1.12, 95% CI: 1.07-1.18, p < 0.001) and CSS (HR: 1.08, 95% CI: 1.02-1.15, p = 0.004) compared with the non-surgical group. The mean survival time in the overall cohort of the pTURP group was shorter than the non-surgical group in both OS [35.13 ± 1.53 vs. 40.44 ± 0.59 months] and CSS [48.8 ± 1.27 vs. 55.92 ± 0.43 months]. In the matched cohort, the pTURP group had significantly lower survival curves for both OS (HR: 1.25, 95% CI: 1.16-1.35, p < 0.001) and CSS (HR: 1.23, 95% CI: 1.12-1.35, p < 0.001) than the non-surgical group. pTURP significantly reduced the survival months of the patients (36.49 ± 0.94 vs. 45.52 ± 1.23 months in OS and 50.1 ± 1.49 vs. 61.28 ± 1.74 months in CSS). In the multivariate COX analysis, pTURP increased the risk of overall mortality (HR: 1.19, 95% CI: 1.09-1.31, p < 0.001) and cancer-specific mortality CSS (HR: 1.23, 95% CI: 1.14-1.33, p < 0.001) compared with the non-surgical group. Conclusions: For mPCa patients with BOO, pTURP could reduce OS and CSS while relieving the obstruction.

Phase Ib study of patients with metastatic castrate-resistant prostate cancer treated with different sequencing regimens of atezolizumab and sipuleucel-T

Background

Combining an immune checkpoint inhibitor with a tumor vaccine may modulate the immune system to leverage complementary mechanisms of action that lead to sustained T-cell activation and a potent prolonged immunotherapeutic response in metastatic castration resistant prostate cancer (mCRPC).

Methods

Subjects with asymptomatic or minimally symptomatic mCRPC were randomly assigned in a 1:1 ratio to receive either atezolizumab followed by sipuleucel-T (Arm 1) or sipuleucel-T followed by atezolizumab (Arm 2). The primary endpoint was safety, while secondary endpoints included preliminary clinical activity such as objective tumor response and systemic immune responses that could identify key molecular and immunological changes associated with sequential administration of atezolizumab and sipuleucel-T.

Results

A total of 37 subjects were enrolled. The median age was 75.0 years, median prostate specific antigen (PSA) was 21.9 ng/mL, and subjects had a median number of three prior treatments. Most subjects (83.8%) had at least one treatment-related adverse event. There were no grade 4 or 5 toxicities attributed to either study drug. Immune-related adverse events and infusion reactions occurred in 13.5% of subjects, and all of which were grade 1 or 2. Of 23 subjects with Response Evaluation Criteria in Solid Tumors measurable disease, only one subject in Arm 2 had a partial response (PR) and four subjects overall had stable disease (SD) at 6 months reflecting an objective response rate of 4.3% and a disease control rate of 21.7%. T-cell receptor diversity was higher in subjects with a response, including SD. Immune response to three novel putative antigens (SIK3, KDM1A/LSD1, and PIK3R6) appeared to increase with treatment.

Conclusions

Overall, regardless of the order in which they were administered, the combination of atezolizumab with sipuleucel-T appears to be safe and well tolerated with a comparable safety profile to each agent administered as monotherapy. Correlative immune studies may suggest the combination to be beneficial; however, further studies are needed.

Trial registration number

NCT03024216.

Macrophage-derived cholesterol contributes to therapeutic resistance in prostate cancer

Castration-resistant prostate cancer (CRPC) is a lethal stage of disease in which androgen receptor (AR) signaling is persistent despite androgen deprivation therapy (ADT). Most studies have focused on investigating cell-autonomous alterations in CRPC, while the contributions of the tumor microenvironment are less well understood. Here we sought to determine the role of tumor-associated macrophages in CRPC, based upon their role in cancer progression and therapeutic resistance. In a syngeneic model that reflected the mutational landscape of CRPC, macrophage depletion resulted in a reduced transcriptional signature for steroid and bile acid synthesis, indicating potential perturbation of cholesterol metabolism. As cholesterol is the precursor of the five major types of steroid hormones, we hypothesized that macrophages were regulating androgen biosynthesis within the prostate tumor microenvironment. Macrophage depletion reduced androgen levels within prostate tumors and restricted androgen receptor (AR) nuclear localization in vitro and in vivo. Macrophages were also cholesterol-rich and were able to transfer cholesterol to tumor cells in vitro. AR nuclear translocation was inhibited by activation of Liver X Receptor (LXR)-β, the master regulator of cholesterol homeostasis. Consistent with these data, macrophage depletion extended survival during ADT and the presence of macrophages correlated with therapeutic resistance in patient-derived explants. Taken together, these findings support the therapeutic targeting of macrophages in CRPC.

Microfluidic Assessment of Drug Effects on Physical Properties of Androgen Sensitive and Non-Sensitive Prostate Cancer Cells

The identification and treatment of androgen-independent prostate cancer are both challenging and significant. In this work, high-throughput deformability cytometry was employed to assess the effects of two anti-cancer drugs, docetaxel and enzalutamide, on androgen-sensitive prostate cancer cells (LNCaP) and androgen-independent prostate cancer cells (PC-3), respectively. The quantified results show that PC-3 and LNCaP present not only different intrinsic physical properties but also different physical responses to the same anti-cancer drug. PC-3 cells possess greater stiffness and a smaller size than LNCaP cells. As the docetaxel concentration increases, PC-3 cells present an increase in stiffness and size, but LNCaP cells only present an increase in stiffness. As the enzalutamide concentration increases, PC-3 cells present no physical changes but LNCaP cells present changes in both cell size and deformation. These results demonstrated that cellular physical properties quantified by the deformability cytometry are effective indicators for identifying the androgen-independent prostate cancer cells from androgen-sensitive prostate cancer cells and evaluating drug effects on these two types of prostate cancer.

Prostate cancer and microfluids

Microfluidic systems aim to detect sample matter quickly with high sensitivity and resolution, on a small scale. With its increased use in medicine, the field is showing significant promise in prostate cancer diagnosis and management due, in part, to its ability to offer point-of-care testing. This review highlights some of the research that has been undertaken in respect of prostate cancer and microfluidics. Firstly, this review considers the diagnosis of prostate cancer through use of microfluidic systems and analyses the detection of prostate specific antigen, proteins, and circulating tumor cells to highlight the scope of current advancements. Secondly, this review analyses progressions in the understanding of prostate cancer physiology and considers techniques used to aid treatment of prostate cancer, such as the creation of a micro-environment. Finally, this review highlights potential future roles of microfluidics in assisting prostate cancer, such as in exosomal analysis. In conclusion, this review shows the vast scope and application of microfluidic systems and how these systems will ensure advancements to future prostate cancer management.

Abiraterone Acetate Induces CREB1 Phosphorylation and Enhances the Function of the CBP-p300 Complex, Leading to Resistance in Prostate Cancer Cells

PURPOSE

Abiraterone acetate (AA), an inhibitor of cytochrome P450 17alpha-hydroxylase/17, 20 lyase, is an FDA-approved drug for advanced prostate cancer. However, not all patients respond to AA, and AA resistance ultimately develops in patients who initially respond. We aimed to identify AA resistance mechanisms in prostate cancer cells.

EXPERIMENTAL DESIGN

We established several AA-resistant cell lines and performed a comprehensive study on mechanisms involved in AA resistance development. RNA sequencing and phospho-kinase array screenings were performed to discover that the cAMP-response element CRE binding protein 1 (CREB1) was a critical molecule in AA resistance development.

RESULTS

The drug-resistant cell lines are phenotypically stable without drug selection, and exhibit permanent global gene expression changes. The phosphorylated CREB1 (pCREB1) is increased in AA-resistant cell lines and is critical in controlling global gene expression. Upregulation of pCREB1 desensitized prostate cancer cells to AA, while blocking CREB1 phosphorylation resensitized AA-resistant cells to AA. AA treatment increases intracellular cyclic AMP (cAMP) levels, induces kinases activity, and leads to the phosphorylation of CREB1, which may subsequently augment the essential role of the CBP/p300 complex in AA-resistant cells because AA-resistant cells exhibit a relatively higher sensitivity to CBP/p300 inhibitors. Further pharmacokinetics studies demonstrated that AA significantly synergizes with CBP/p300 inhibitors in limiting the growth of prostate cancer cells.

CONCLUSIONS

Our studies suggest that AA treatment upregulates pCREB1, which enhances CBP/p300 activity, leading to global gene expression alterations, subsequently resulting in drug resistance development. Combining AA with therapies targeting resistance mechanisms may provide a more effective treatment strategy.

Upregulation of potential regulatory signaling molecules correlate with androgen receptor splice variants AR-V7 and AR-V567es in prostate cancer metastasis

AIM

Androgen receptor splice variants (AR-Vs) produced by alternative splicing of the AR play an important role in the treatment resistance and progression of prostate cancer (PCa). In this study, two most common AR variants and how they associate with the inflammatory response (NF-Kβ) and regulatory transcriptional activity (HSP-27) genes were investigated in patients with PCa and metastatic PCa (Met-PCa).

METHODS

Our study was carried out with the whole blood obtained from 25 healthy control subjects, 25 PCa patients and 39 Met-PCa patients. We examined the expression levels of AR, AR-V7 and AR-V567es genes via Real-time PCR and those of HSP-27 and NF-Kβ via ELISA method.

RESULTS

AR, AR-V7 and AR-V567es expressions were observed in 84.61%, 64.1%, 23.07% of Met-PCa patients respectively. The expression levels of full-length AR and variants (AR-V7 and AR-V567es) were associated with the prostate cancer stage. In the Met-PCa, the expression levels of AR, AR-V7 and AR-V567es were associated with the Gleason Scores but not with the PSA levels. AR-V7 expression levels in stage T4 patients significantly increased. NF-Kβ and HSP-27 protein levels were significantly higher in Met-PCa patients.

DISCUSSION

Our findings highlight the targeting of the proteostasis and inflammation pathways through inhibiting HSP-27 and NF-Kβ. This might be a valuable strategy to overcome anti-androgen resistance and improve drug therapy in Met-PCa patients whose gene expression levels of AR-V7 and AR-V567es variants are high.

Inflammatory infiltration is associated with AR expression and poor prognosis in hormone naïve prostate cancer

BACKGROUND

Tumor microenvironment inflammatory infiltration is proposed as a protumorigenic mechanism for prostate cancer with proinflammatory cytokines stimulating androgen receptor (AR) activity. However, association with patient prognosis remains unclear. This study derives an inflammatory gene signature associated with AR expression and investigates CD3+ and CD8+ T-lymphocyte infiltration association with AR and prognosis.

METHODS

Gene profiling of inflammatory related genes was performed on 71 prostate biopsies. Immunohistochemistry on 243 hormone-naïve prostate cancers was performed for CD3, CD8, AR, and phosphorylated AR tumor expression.

RESULTS

Multiple proinflammatory genes were differentially expressed in association with high AR expression compared with low AR expression including PI3KCA and MAKP8 (adjusted P < .05). High CD3+ and high CD8+ infiltration associated with reduced cancer-specific survival (P = .018 and P = .020, respectively). High CD3+ infiltration correlated with high tumor cytoplasmic AR expression and if assessed together, they associated with reduced cancer-specific and 5-year survival from 90% to 56% (P = .000179). High CD8+ cytotoxic infiltration associated with high androgen-independent tumor nuclear AR serine 213 phosphorylation (correlation coefficient = 0.227; P = .003) and when assessed together associated with poor clinico-pathological features including perineural invasion (P = .001). Multiple genes involved in proinflammatory signaling pathways are upregulated in high AR expressing prostate samples.

CONCLUSION

T-lymphocyte infiltration in hormone-naïve disease associates with androgen-independent driven disease and provides possible therapeutic targets to reduce transformation from hormone-naïve to castrate-resistant disease.

Nuclear-mitochondrial crosstalk: On the role of the nuclear receptor liver receptor homolog-1 (NR5A2) in the regulation of mitochondrial metabolism, cell survival, and cancer

Liver receptor homolog-1 (LRH-1, NR5A2) is an orphan nuclear receptor with widespread activities in the regulation of development, stemness, metabolism, steroidogenesis, and proliferation. Many of the LRH-1-regulated processes target the mitochondria and associated activities. While under physiological conditions, a balanced LRH-1 expression and regulation contribute to the maintenance of a physiological equilibrium, deregulation of LRH-1 has been associated with inflammation and cancer. In this review, we discuss the role and mechanism(s) of how LRH-1 regulates metabolic processes, cell survival, and cancer in a nuclear-mitochondrial crosstalk, and evaluate its potential as a pharmacological target.

Successful management of prostate cancer with bulky pelvic lymph node metastases after rapid development of castration-resistant prostate cancer: a case report with review of the literature

The rapid development of castration-resistant prostate cancer (CRPC) is a poor prognostic sign for loco-regionally advanced prostate cancer. Non-metastatic CRPC (nmCRPC) with bulky regional lymph node metastases is extremely rare and difficult to treat clinically without reported case. We present a case of a 72-year-old man with locally advanced prostate cancer with bulky lymph node metastases (53 mm × 77 mm × 67 mm), developing nmCRPC after 9-month ADT treatment. Immunohistochemistry (IHC) tests found partially positive MUC1 and negative BRCA1 expression in the initial biopsy specimens. Next-generation sequence analysis on the blood specimen after CRPC predicted a good tolerance to docetaxel. According to the multidisciplinary team recommendations, he was administrated docetaxel 75 mg/m² on day 1 every 21 days for 6 cycles, and subsequently radiotherapy, with the delivery of a total dose of 67.5, 60-65 and 47.5 Gy in 25 fractions to the prostate, the enlarged lymph nodes and the whole pelvis respectively. Over a follow-up of 50 months, his disease has achieved good local control and he is alive without evidence of distant metastases or late adverse events. This case highlights individualized and multimodal therapy of intensification of systemic therapy and timely application of radiotherapy in such rare condition.

Radiation Therapy for Prostate Cancer

Randomized controlled trials provide evidence-driven clinical decision making in the management of newly diagnosed nonmetastatic and oligometastatic prostate cancer. Advances in technology (eg, multiparametric MRI, MR/transrectal ultrasound fusion biopsy, image-guided radiation therapy, stereotactic body radiation therapy) have transformed diagnosis and treatment of prostate cancer while improving cancer control and quality-of-life outcomes. Exciting breakthroughs are revealing possible new indications for radiotherapy, particularly with respect to oligometastatic prostate cancer. Ongoing studies using next-generation androgen receptor-targeted agents hold promise to continue to improve important clinical outcomes, including metastasis-free prostate cancer-specific and overall survival in addition to health-related quality of life.

Effects of vitamin D as a regulator of androgen intracrinology in LNCAP prostate cancer cells

Prostate cancer is initially treated via androgen deprivation therapy (ADT), a highly successful treatment in the initial pursuit of tumor regression, but commonly restricted by the eventual emergence of a more lethal 'castrate resistant' form of the disease. Intracrine pathways that utilize dehydroepiandrosterone (DHEA) or other circulatory precursor steroids, are thought to generate relevant levels of growth-stimulating androgens such as testosterone (T) and dihydrotestosterone (DHT). In this study, we explored the capacity of the active vitamin D hormone to interact and elicit changes upon this prostatic intracrine pathway at a metabolic level. We used androgen dependent LNCaP cells cultured under steroid-depleted conditions and assessed the impact of vitamin D-based compounds upon intracrine pathways that convert exogenously added DHEA to relevant metabolites, through Mass Spectrometry (MS). Changes in relevant metabolism-related gene targets were also assessed. Our findings confirm that exposure to vitamin D based compounds, within LNCaP cells, elicits measurable and significant reduction in the intracrine conversion of DHEA to T, DHT and other intermediate metabolites within the androgenic pathway. The aassessment and validation of the biological model and analytical platforms were performed by pharmacological manipulations of the SRD5α and HSD-17β enzymes. The data provides further confirmation for how a vitamin D-based regime may be used to counter intracrine mechanisms contributing to the emergence of castrate-resistant tumors.

Microfluidic-Based Mechanical Phenotyping of Androgen-Sensitive and Non-sensitive Prostate Cancer Cells Lines

Cell mechanical properties have been identified to characterize cells pathologic states. Here, we report our work on high-throughput mechanical phenotyping of androgen-sensitive and non-sensitive human prostate cancer cell lines based on a morphological rheological microfluidic method. The theory for extracting cells' elastic modulus from their deformation and area, and the used experimental parameters were analyzed. The mechanical properties of three types of prostate cancer cells lines with different sensitivity to androgen including LNCaP, DU145, and PC3 were quantified. The result shows that LNCaP cell was the softest, DU145 was the second softest, and PC3 was the stiffest. Furthermore, atomic force microscopy (AFM) was used to verify the effectiveness of this high-throughput morphological rheological method.

Androgen upregulates the palmitoylation of eIF3L in human prostate LNCaP cells

Background: Prostate cancer is the second leading cause of cancer-related deaths in Western countries. Most patients diagnosed with advanced prostate cancer can be treated with the main treatment: androgen deprivation therapy (ADT). The androgen receptor (AR) signaling axis plays a pivotal role in the progression of prostate cancer. However, most patients can ultimately progress to the castration-resistant prostate cancer (CRPC) stage within 2 years. At this stage, drugs targeting the AR signaling axis, including enzalutamide and abiraterone acetate, cannot prevent the progression of prostate cancer, thus predicting a poor prognosis. The molecular mechanism lies in the aberrant AR reactivation, which exhibits an adaptive response to ADT, such as the presence of AR splice variants. Thus, CRPC treatment remains a challenge. Purpose: In addition to the AR axis, a mechanism leading to this progression should be determined. The present study mainly compared palmitoylated proteins between androgen-treated LNCaP cells and non-treated LNCaP cells by palmitoylome profiling, to illustrate the changes at proteomic levels. Materials and methods: To screen the androgen-induced palmitoylated proteins, we conducted proteomic experiments using clickable palmitate probe (Alk-C16) between three individual pairs of androgen-treated and non-treated LNCaP cells. Results: We identified 4351 unique peptides corresponding to 835 proteins, among them a number of these identified proteins were palmitoylated proteins, particularly eIF3L. Androgen treatment significantly increased the palmitoylation level of eIF3L, an individual subunit of eIF3. As an initiation factor, eIF3L plays a pivotal role in the translation of mRNAs encoding growth-promoting proteins by enhancing translation rates, thus controlling cell proliferation. Conclusion: In this study, we demonstrated that the regulation of eIF3L palmitoylation may provide new directions for the therapy of prostate cancer. Moreover, the increased level of androgen-induced eIF3L may be used as a biomarker for the diagnosis of early-stage prostate cancer.

A prospective genome-wide study of prostate cancer metastases reveals association of wnt pathway activation and increased cell cycle proliferation with primary resistance to abiraterone acetate-prednisone

Background

Genomic aberrations have been identified in metastatic castration-resistant prostate cancer (mCRPC), but molecular predictors of resistance to abiraterone acetate/prednisone (AA/P) treatment are not known.

Patients and methods

In a prospective clinical trial, mCRPC patients underwent whole-exome sequencing (n = 82) and RNA sequencing (n = 75) of metastatic biopsies before initiating AA/P with the objective of identifying genomic alterations associated with resistance to AA/P. Primary resistance was determined at 12 weeks of treatment using criteria for progression that included serum prostate-specific antigen measurement, bone and computerized tomography imaging and symptom assessments. Acquired resistance was determined using the end point of time to treatment change (TTTC), defined as time from enrollment until change in treatment from progressive disease. Associations of genomic and transcriptomic alterations with primary resistance were determined using logistic regression, Fisher's exact test, single and multivariate analyses. Cox regression models were utilized for determining association of genomic and transcriptomic alterations with TTTC.

Results

At 12 weeks, 32 patients in the cohort had progressed (nonresponders). Median study follow-up was 32.1 months by which time 58 patients had switched treatments due to progression. Median TTTC was 10.1 months (interquartile range: 4.4-24.1). Genes in the Wnt/β-catenin pathway were more frequently mutated and negative regulators of Wnt/β-catenin signaling were more frequently deleted or displayed reduced mRNA expression in nonresponders. Additionally, mRNA expression of cell cycle regulatory genes was increased in nonresponders. In multivariate models, increased cell cycle proliferation scores (≥ 50) were associated with shorter TTTC (hazard ratio = 2.11, 95% confidence interval: 1.17-3.80; P = 0.01).

Conclusions

Wnt/β-catenin pathway activation and increased cell cycle progression scores can serve as molecular markers for predicting resistance to AA/P therapy.

Effect of docetaxel on the regulation of proliferation and apoptosis of human prostate cancer cells

Prostate cancer is a common type of malignancy. Given the complexity of prostate cancer and the pressing challenge of chemoresistance, the current study was conducted to investigate the effect of docetaxel (Doc) on androgen receptor (AR)‑dependent and AR‑independent prostate cancers cells. Subsequent experiments were designed to explore the mechanism underlying the Doc‑induced apoptosis. Three different human prostate cancer cell lines, namely PC‑3, LNCaP and DU‑145, were exposed to various concentrations of Doc. The cytotoxic effects of Doc were evaluated by an MTT assay, while apoptosis and cell cycle distribution were determined by flow cytometric analysis of cells stained with Annexin V‑FITC and propidium iodide. Western blot assay was also used to measure the protein levels of B‑cell lymphoma 2 (Bcl‑2), Bcl‑2‑associated death promoter (Bad), total protein kinase B (Akt), phospho‑Akt and caspase‑3/9. Doc induced cytotoxicity in all three cell lines in a dose‑dependent manner. The half maximal inhibitory concentration values for the effect of Doc on PC‑3, DU‑145 and LNCaP cells were 3.72, 4.46 and 1.13 nM, respectively. Furthermore, the results indicated a significant difference in Doc sensitivity between AR‑dependent and AR‑independent prostate cancer cells. Evaluation of key gene expression at protein levels revealed a notable decrease in antiapoptotic Bcl‑2 and p‑Akt levels, along with a significant increase in pro‑apoptotic Bad, caspase‑3 and caspase‑9 levels. Therefore, Doc may induce cell apoptosis in prostate cancer via various pathways.

Androgen receptor expression reduces stemness characteristics of prostate cancer cells (PC3) by repression of CD44 and SOX2

Studies have shown that a subgroup of tumor cells possess stemness characteristics having self-renewal capacity and the ability to form new tumors. We sought to identify the plausible stemness factor that determines the "molecular signature" of prostate cancer (PCa) cells derived from different metastases (PC3, PCa2b, LNCaP, and DU145) and whether androgen receptor (AR) influences the maintenance of stemness features. Here we show sex-determining region Y (SRY)-box 2 (SOX2) as a putative stem cell marker in PC3 PCa cells and not in DU145, PCa2b, or LNCaP cells. PCa2b and PC3 cells were derived from bone metastases. PCa2b cells which are positive for the AR failed to demonstrate the expression of either cluster of differentiation 44 (CD44) or SOX2. Knockdown (KD) of AR in these cells did not affect the expression of either CD44 or SOX2. Conversely, PC3 cells, which are negative for AR, expressed both CD44 and SOX2. However, the expression of AR downregulated the expression of both CD44 and SOX2 in PC3 cells. CD44 regulates SOX2 expression as KD of CD44 and reduces SOX2 levels considerably. SOX2 KD attenuated not only the expression of SNAIL and SLUG but also the migration and tumorsphere formation in PC3 cells. Collectively, our findings underscore a novel role of CD44 signaling in the maintenance of stemness and progression of cancer through SOX2 in AR-independent PC3 cells. SOX2 has a role in the regulation of expression of SNAIL and SLUG. SOX2 could be a potential therapeutic target to thwart the progression of SOX2-positive cancer cells or recurrence of androgen-independent 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.

Epigenetic Regulation of Chromatin in Prostate Cancer

Epigenetics refers to mitotically/meiotically heritable mechanisms that regulate gene transcription without a need for changes in the DNA code. Covalent modifications of DNA, in the form of methylation, and histone post-translational modifications, in the form of acetylation and methylation, constitute the epigenetic code of a cell. Both DNA and histone modifications are highly dynamic and often work in unison to define the epigenetic state of a cell. Most epigenetic mechanisms regulate gene transcription by affecting localized/genome-wide transitions between heterochromatin and euchromatin states, thereby altering the accessibility of the transcriptional machinery and in turn, reduce/increase transcriptional output. Altered chromatin structure is associated with cancer progression, and epigenetic plasticity primarily governs the resistance of cancer cells to therapeutic agents. In this chapter, we specifically focus on regulators of histone methylation and acetylation, the two well-studied chromatin post-translational modifications, in the context of prostate cancer.

Targeting the BRD4-HOXB13 Coregulated Transcriptional Networks with Bromodomain-Kinase Inhibitors to Suppress Metastatic Castration-Resistant Prostate Cancer

Resistance to androgen receptor (AR) antagonists is a significant problem in the treatment of castration-resistant prostate cancers (CRPC). Identification of the mechanisms by which CRPCs evade androgen deprivation therapies (ADT) is critical to develop novel therapeutics. We uncovered that CRPCs rely on BRD4-HOXB13 epigenetic reprogramming for androgen-independent cell proliferation. Mechanistically, BRD4, a member of the BET bromodomain family, epigenetically promotes HOXB13 expression. Consistently, genetic disruption of HOXB13 or pharmacological suppression of its mRNA and protein expression by the novel dual-activity BET bromodomain-kinase inhibitors directly correlates with rapid induction of apoptosis, potent inhibition of tumor cell proliferation and cell migration, and suppression of CRPC growth. Integrative analysis revealed that the BRD4-HOXB13 transcriptome comprises a proliferative gene network implicated in cell-cycle progression, nucleotide metabolism, and chromatin assembly. Notably, although the core HOXB13 target genes responsive to BET inhibitors (HOTBIN10) are overexpressed in metastatic cases, in ADT-treated CRPC cell lines and patient-derived circulating tumor cells (CTC) they are insensitive to AR depletion or blockade. Among the HOTBIN10 genes, AURKB and MELK expression correlates with HOXB13 expression in CTCs of mCRPC patients who did not respond to abiraterone (ABR), suggesting that AURKB inhibitors could be used additionally against high-risk HOXB13-positive metastatic prostate cancers. Combined, our study demonstrates that BRD4-HOXB13-HOTBIN10 regulatory circuit maintains the malignant state of CRPCs and identifies a core proproliferative network driving ADT resistance that is targetable with potent dual-activity bromodomain-kinase inhibitors.

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.

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.

Profiling Prostate Cancer Therapeutic Resistance

The major challenge in the treatment of patients with advanced lethal prostate cancer is therapeutic resistance to androgen-deprivation therapy (ADT) and chemotherapy. Overriding this resistance requires understanding of the driving mechanisms of the tumor microenvironment, not just the androgen receptor (AR)-signaling cascade, that facilitate therapeutic resistance in order to identify new drug targets. The tumor microenvironment enables key signaling pathways promoting cancer cell survival and invasion via resistance to anoikis. In particular, the process of epithelial-mesenchymal-transition (EMT), directed by transforming growth factor-β (TGF-β), confers stem cell properties and acquisition of a migratory and invasive phenotype via resistance to anoikis. Our lead agent DZ-50 may have a potentially high efficacy in advanced metastatic castration resistant prostate cancer (mCRPC) by eliciting an anoikis-driven therapeutic response. The plasticity of differentiated prostate tumor gland epithelium allows cells to de-differentiate into mesenchymal cells via EMT and re-differentiate via reversal to mesenchymal epithelial transition (MET) during tumor progression. A characteristic feature of EMT landscape is loss of E-cadherin, causing adherens junction breakdown, which circumvents anoikis, promoting metastasis and chemoresistance. The targetable interactions between androgens/AR and TGF-β signaling are being pursued towards optimized therapeutic regimens for the treatment of mCRPC. In this review, we discuss the recent evidence on targeting the EMT-MET dynamic interconversions to overcome therapeutic resistance in patients with recurrent therapeutically resistant prostate cancer. Exploitation of the phenotypic landscape and metabolic changes that characterize the prostate tumor microenvironment in advanced prostate cancer and consequential impact in conferring treatment resistance are also considered in the context of biomarker discovery.

Nuclear Receptor LRH-1 Functions to Promote Castration-Resistant Growth of Prostate Cancer via Its Promotion of Intratumoral Androgen Biosynthesis

Targeting of steroidogenic enzymes (e.g., abiraterone acetate targeting CYP17A1) has been developed as a novel therapeutic strategy against metastatic castration-resistant prostate cancer (CRPC). However, resistance to steroidal inhibitors inevitably develops in patients, the mechanisms of which remain largely unknown. Liver receptor homolog-1 (LRH-1, NR5A2) is a nuclear receptor, originally characterized as an important regulator of some liver-specific metabolic genes. Here, we report that LRH-1, which exhibited an increased expression pattern in high-grade prostate cancer and CRPC xenograft models, functions to promote de novo androgen biosynthesis via its direct transactivation of several key steroidogenic enzyme genes, elevating intratumoral androgen levels and reactivating AR signaling in CRPC xenografts as well as abiraterone-treated CRPC tumors. Pharmacologic inhibition of LRH-1 activity attenuated LRH-1-mediated androgen deprivation and anti-androgen resistance of prostate cancer cells. Our findings not only demonstrate the significant role of LRH-1 in the promotion of intratumoral androgen biosynthesis in CRPC via its direct transcriptional control of steroidogenesis, but also suggest targeting LRH-1 could be a potential therapeutic strategy for CRPC management.Significance: These findings not only demonstrate the significant role of the nuclear receptor LRH-1 in the promotion of intratumoral androgen biosynthesis in CRPC via its direct transcriptional control of steroidogenesis, but also suggest targeting LRH-1 could be a potential therapeutic strategy for CRPC management. Cancer Res; 78(9); 2205-18. ©2018 AACR.

Blockade of ACK1/TNK2 To Squelch the Survival of Prostate Cancer Stem-like Cells

Prostate cancer stem-like cells (PCSCs) are not only enriched in the CD44⁺PSA^-/lo subpopulation but also employ androgen-independent signaling mechanisms for survival. CD44⁺ PCSCs defy androgen deprivation, resist chemo- and radiotherapy and are highly tumorigenic. Human prostate tissue microarray (TMA) staining revealed an increased membranous staining of CD44 in the luminal compartment in higher grade G7-G9 tumors versus staining of the basal layer in benign hyperplasia. To uncover tyrosine kinase/s critical for the survival of the CD44⁺PSA^-/lo subpopulation, we performed an unbiased screen targeting 87 tyrosine kinases with gene specific siRNAs. Among a subset of tyrosine kinases crucial for PCSC survival, was a non-receptor tyrosine kinase, ACK1/TNK2, a critical regulator of castration resistant prostate cancer (CRPC) growth. Consistently, activated ACK1 as measured by phosphorylation at Tyr284 was significant in the CD44⁺PSA^-/lo population. Conversely, pharmacological inhibition by ACK1 inhibitor, (R)-9bMS mitigated CD44⁺PSA^-/lo sphere formation, overcame resistance to radiation-induced cell death, induced significant apoptosis in PCSCs and inhibited CD44⁺PSA^-/lo xenograft tumor growth in castrated mice suggesting dependency of PCSCs on ACK1 for survival. Thus, blockade of ACK1/TNK2 could be a new therapeutic modality to target recalcitrant PCSCs.

Androgen Receptor-CaMKK2 Axis in Prostate Cancer and Bone Microenvironment

The skeletal system is of paramount importance in advanced stage prostate cancer (PCa) as it is the preferred site of metastasis. Complex mechanisms are employed sequentially by PCa cells to home to and colonize the bone. Bone-resident PCa cells then recruit osteoblasts (OBs), osteoclasts (OCs), and macrophages within the niche into entities that promote cancer cell growth and survival. Since PCa is heavily reliant on androgens for growth and survival, androgen-deprivation therapy (ADT) is the standard of care for advanced disease. Although it significantly improves survival rates, ADT detrimentally affects bone health and significantly increases the risk of fractures. Moreover, whereas the majority patients with advanced PCa respond favorably to androgen deprivation, most experience a relapse of the disease to a hormone-refractory form within 1-2 years of ADT. The tumor adapts to surviving under low testosterone conditions by selecting for mutations in the androgen receptor (AR) that constitutively activate it. Thus, AR signaling remains active in PCa cells and aids in its survival under low levels of circulating androgens and additionally allows the cancer cells to manipulate the bone microenvironment to fuel its growth. Hence, AR and its downstream effectors are attractive targets for therapeutic interventions against PCa. Ca²⁺/calmodulin-dependent protein kinase kinase 2 (CaMKK2), was recently identified as a key downstream target of AR in coordinating PCa cell growth, survival, and migration. Additionally, this multifunctional serine/threonine protein kinase is a critical mediator of bone remodeling and macrophage function, thus emerging as an attractive therapeutic target downstream of AR in controlling metastatic PCa and preventing ADT-induced bone loss. Here, we discuss the role played by AR-CaMKK2 signaling axis in PCa survival, metabolism, cell growth, and migration as well as the cell-intrinsic roles of CaMKK2 in OBs, OCs, and macrophages within the bone microenvironment.

Newly Diagnosed Metastatic Prostate Cancer: Has the Paradigm Changed?

Androgen deprivation therapy (ADT) has been conventional treatment of newly diagnosed metastatic prostate cancer for more than 70 years. However, all patients eventually become castration-resistant and a significant proportion of life span is spent in the castration-resistant state. Prospective randomized control trials have incorporated early chemotherapy along with ADT based on the hypothesis that a significant level of resistance to ADT already exists in newly diagnosed metastatic prostate cancer and ADT exhibits synergistic antitumor activity with taxanes. We discuss the changing landscape of management of patients with newly diagnosed metastatic prostate cancer based on recently published landmark randomized trials.

Androgen-independent LNCaP cells are a subline of LNCaP cells with a more aggressive phenotype and androgen suppresses their growth by inducing cell cycle arrest at the G1 phase

Androgen deprivation therapy (ADT, surgical or chemical castration) is the mainstay treatment for metastatic prostate cancer (PCa); however, patients ineluctably relapse despite extremely low androgen levels. This evolution of PCa indicates its lethal progression. In this study, to mimic the traits of clinical PCa progression in vitro, we investigated the alterations in the cell biological characteristics in androgen-independent LNCaP cells (LNCaP-AI cells) compared with LNCaP cells. We also examined the effects of androgen on LNCaP and LNCaP-AI cell proliferation, androgen receptor (AR) expression and prostate-specific antigen (PSA) secretion. Furthermore, AR was silenced in the LNCaP and LNCaP-AI cells to detect the roles taht AR plays in cell growth, apoptosis and PSA secretion. We found that prolonged androgen ablation increased the LNCaP-AI cell growth rate and cell invasiveness, and induced epithelial-mesenchymal transition in the LNCaP-AI cells. Moreover, despite the fact that the LNCaP and LNCaP-AI cells expressed equal amounts of AR protein, androgen induced a greater secretion of PSA in the LNCaP-AI cells than in the LNCaP cells. The proliferation of the LNCaP-AI cells was not dependent on, but was suppressed by androgen, which led to arrest at the G1 phase. Conversely, androgen significantly increased LNCaP cell proliferation by promoting the G1-S transition. Moreover, the silencing of AR suppressed LNCaP and LNCaP-AI cell growth by inducing cell cycle arrest at the G1 phase rather than promoting apoptosis, and reduced PSA secretion. On the whole, our data suggest that LNCaP-AI cells have a more more aggressive phenotype compared with the LNCaP cells; AR remains a critical factor in the LNCaP-AI cells, and androgen suppresses LNCaP-AI cell growth by blocking the cell cycle at the G1 phase.

Evaluation of Newly Developed Chemical Castration Method: Changes in Hormone Gene Expression of Hypothalamic-Pituitary Axis

Surgical castration (also known as orchidectomy, ORX) has been frequently performed to avoid uncontrolled breeding. However, it has some serious disadvantages. Several laboratories have developed chemical castration methods, using bilateral intratesticular injection (BITI) of simple chemical solutions. The present study was undertaken to compare the effects of ORX and of hypertonic saline BITI on the androgen-sensitive tissues such as pituitary and hypothalamus. Serum testosterone (T) levels of ORX animals and hypertonic saline BITI animals (SAL) after 4 weeks of the manipulations exhibited significantly drops as compared with the levels of intact animals (Intact:ORX:SAL = 7.74± 1.31:1.34±0.19:1.28±0.18 ng/ml, p<0.001). Both ORX and BITI method induced similar stimulatory effects on the pituitary gonadotropin subunits and hypothalamic KiSS-1 gene expressions. In contrast, the effects of ORX and hypertonic saline BITI on hypothalamic GnRH gene expression were different from these gene expressions, shown an inverse relationship between the two groups (Intact:ORX:SAL = 1:0.45±0.06:1:2.07±0.41:1.51±0.37 AU; ORX, p<0.001; SAL, p<0.05). In conclusion, we provided evidence that hypertonic saline BITI method has equivalent efficacy of T depletion to surgical castration in rats. The present study suggests the hypertonic saline BITI could be a promising substitute to conventional surgical castration.

A Simple PSA-Based Computational Approach Predicts the Timing of Cancer Relapse in Prostatectomized Patients

Recurrences of prostate cancer affect approximately one quarter of patients who have undergone radical prostatectomy. Reliable factors to predict time to relapse in specific individuals are lacking. Here, we present a mathematical model that evaluates a biologically sensible parameter (α) that can be estimated by the available follow-up data, in particular by the PSA series. This parameter is robust and highly predictive for the time to relapse, also after administration of adjuvant androgen deprivation therapies. We present a practical computational method based on the collection of only four postsurgical PSA values. This study offers a simple tool to predict prostate cancer relapse. Cancer Res; 76(17); 4941-7. ©2016 AACR.

LncRNA GAS5 Inhibits Cellular Proliferation by Targeting P27Kip1

Recent studies have demonstrated that long noncoding RNAs (lncRNA) have important roles in cancer biology, and that the downregulation of lncRNA growth arrest-specific transcript 5 (GAS5) has been reported in a variety of human cancers. However, its role in prostate cancer is largely unknown. This study aims to investigate the biological role and underlying mechanism of GAS5 on proliferation in prostate cancer. The results demonstrate that GAS5 expression is significantly decreased in prostate cancer cells compared with prostate epithelial cells. Ectopic expression of GAS5 inhibited cell proliferation and induced a cell-cycle arrest in G₀-G₁ phase, whereas GAS5 knockdown promoted the G₁-S phase transition. Subsequent analysis demonstrated that P27^Kip1, a known regulator of cell cycle, was positively regulated by GAS5 and upregulation of GAS5 increased its promoter activity. E2F1, an important transcription factor, was shown to bind directly to and activate the P27^Kip1 promoter. In addition, GAS5 interacted with E2F1 and enhanced the binding of E2F1 to the P27^Kip1 promoter. Collectively, these findings determine that GAS5 functions as a tumor suppressor in prostate cancer development and progression via targeting P27^Kip1Implications: This study reveals a molecular pathway involving lncRNA GAS5/E2F1/P27^Kip1 which regulates cell proliferation and could be a potential therapeutic target in prostate cancer. Mol Cancer Res; 15(7); 789-99. ©2017 AACR.

Differential expression of AP-1 transcription factors in human prostate LNCaP and PC-3 cells: role of Fra-1 in transition to CRPC status

Androgen receptor (AR) signaling axis plays a vital role in the development of prostate and critical in the progression of prostate cancer. Androgen withdrawal initially regresses tumors but eventually develops into aggressive castration-resistant prostate cancer (CRPC). Activator Protein-1 (AP-1) transcription factors are most likely to be associated with malignant transformation in prostate cancer. Hence, to determine the implication of AR and AP-1 in promoting the transition of prostate cancer to the androgen-independent state, we used AR-positive LNCaP and AR-negative PC-3 cells as an in vitro model system. The effect of dihydrotestosterone or anti-androgen bicalutamide on the cell proliferation and viability was assessed by MTT assay. Expression studies on AR, marker genes-PSA, TMPRSS2, and different AP-1 factors were analyzed by semi-quantitative RT-PCR and expressions of AR and Fra-1 proteins were analyzed by Western blotting. Dihydrotestosterone induced the cell proliferation in LNCaP with no effect on PC-3 cells. Bicalutamide decreased the viability of both LNCaP and PC-3 cells. Dihydrotestosterone induced the expression of AR, PSA, c-Jun, and Fra-1 in LNCaP cells, and it was c-Jun and c-Fos in case of PC-3 cells, while bicalutamide decreased their expression. In addition, constitutive activation and non-regulation of Fra-1 by bicalutamide in PC-3 cells suggested that Fra-1, probably a key component, involved in transition of aggressive androgen-independent PC-3 cells with poor prognosis.

Indirect comparison between abiraterone acetate and enzalutamide for the treatment of metastatic castration-resistant prostate cancer: a systematic review

This study was designed to evaluate the efficacy, tolerability, and sequential administration of abiraterone acetate (AA) and enzalutamide (Enz) for metastatic castration-resistant prostate cancer (mCRPC). A literature search was performed with PubMed, Embase, and Web of Science databases to identify relevant studies. Reviewed literature included published phase III trials of AA or Enz in mCRPC and studies regarding their sequential administration. Given the difference in control arms in AA (active comparator) and Enz (true placebo) randomized phase III studies, indirect comparisons between AA and Enz in mCRPC showed no statistically significant difference in overall survival in prechemotherapy and postchemotherapy settings (HR: 0.90, 95% CI, 0.73-1.11; HR: 0.85, 95% CI, 0.68-1.07). Compared with AA, Enz may better outperform control arms in treating mCRPC both before and after chemotherapy regarding secondary endpoints based on indirect comparisons: time to prostate-specific antigen (PSA) progression (HR: 0.34, 95% CI, 0.28-0.42; HR: 0.40, 95% CI, 0.30-0.53), radiographic progression-free survival (HR: 0.37, 95% CI, 0.28-0.48; HR: 0.61, 95% CI, 0.50-0.74), and PSA response rate (OR: 18.29, 95% CI, 11.20-29.88; OR: 10.69, 95% CI, 3.92-29.20). With regard to the effectiveness of Enz following AA or AA following Enz, recent retrospective case series reported overall survival and secondary endpoints for patients with mCRPC progression after chemotherapy. However, confirmatory head-to-head trials are necessary to determine the optimal sequencing of these agents.

Profiling adrenal 11β-hydroxyandrostenedione metabolites in prostate cancer cells, tissue and plasma: UPC2-MS/MS quantification of 11β-hydroxytestosterone, 11keto-testosterone and 11keto-dihydrotestosterone

Adrenal C₁₉ steroids serve as precursors to active androgens in the prostate. Androstenedione (A4), 11β-hydroxyandrostenedione (11OHA4) and 11β-hydroxytestosterone (11OHT) are metabolised to potent androgen receptor (AR) agonists, dihydrotestosterone (DHT), 11-ketotestosterone (11KT) and 11-ketodihydrotestosterone (11KDHT). The identification of 11OHA4 metabolites, 11KT and 11KDHT, as active androgens has placed a new perspective on adrenal C11-oxy C₁₉ steroids and their contribution to prostate cancer (PCa). We investigated adrenal androgen metabolism in normal epithelial prostate (PNT2) cells and in androgen-dependent prostate cancer (LNCaP) cells. We also analysed steroid profiles in PCa tissue and plasma, determining the presence of the C₁₉ steroids and their derivatives using ultra-performance liquid chromatography (UHPLC)- and ultra-performance convergence chromatography tandem mass spectrometry (UPC²-MS/MS). In PNT2 cells, sixty percent A4 (60%) was primarily metabolised to 5α-androstanedione (5αDIONE) (40%), testosterone (T) (10%), and androsterone (AST) (10%). T (30%) was primarily metabolised to DHT (10%) while low levels of A4, 5αDIONE and 3αADIOL (≈20%) were detected. Conjugated steroids were not detected and downstream products were present at <0.05μM. Only 20% of 11OHA4 and 11OHT were metabolised with the former yielding 11keto-androstenedione (11KA4), 11KDHT and 11β-hydroxy-5α-androstanedione (11OH-5αDIONE) and the latter yielding 11OHA4, 11KT and 11KDHT with downstream products <0.03μM. In LNCaP cells, A4 (90%) was metabolised to AST-glucuronide via the alternative pathway while T was detected as T-glucuronide with negligible conversion to downstream products. 11OHA4 (80%) and 11OHT (60%) were predominantly metabolised to 11KA4 and 11KT and in both assays more than 50% of 11KT was detected in the unconjugated form. In tissue, we detected C11-oxy C₁₉ metabolites at significantly higher levels than the C₁₉ steroids, with unconjugated 11KDHT, 11KT and 11OHA4 levels ranging between 13 and 37.5ng/g. Analyses of total steroid levels in plasma showed significant levels of 11OHA4 (≈230-440nM), 11KT (≈250-390nM) and 11KDHT (≈19nM). DHT levels (<0.14nM) were significantly lower. In summary, 11β-hydroxysteroid dehydrogenase type 2 activity in PNT2 cells was substantially lower than in LNCaP cells, reflected in the conversion of 11OHA4 and 11OHT. Enzyme substrate preferences suggest that the alternate pathway is dominant in normal prostate cells. Glucuronidation activity was not detected in PNT2 cells and while all T derivatives were efficiently conjugated in LNCaP cells, 11KT was not. Substantial 11KT levels were also detected in both PCa tissue and plasma. 11OHA4 therefore presents a significant androgen precursor and its downstream metabolism to 11KT and 11KDHT as well as its presence in PCa tissue and plasma substantiate the importance of this adrenal androgen.

Androgen receptor antagonists compromise T cell response against prostate cancer leading to early tumor relapse

Surgical and medical androgen deprivation therapy (ADT) is a cornerstone for prostate cancer treatment, but relapse usually occurs. We herein show that orchiectomy synergizes with immunotherapy, whereas the more widely used treatment of medical ADT involving androgen receptor (AR) antagonists suppresses immunotherapy. Furthermore, we observed that the use of medical ADT could unexpectedly impair the adaptive immune responses through interference with initial T cell priming rather than in the reactivation or expansion phases. Mechanistically, we have revealed that inadvertent immunosuppression might be potentially mediated by a receptor shared with γ-aminobutyric acid. Our data demonstrate that the timing and dosing of antiandrogens are critical to maximizing the antitumor effects of combination therapy. This study highlights an underappreciated mechanism of AR antagonist-mediated immunosuppression and provides a new strategy to enhance immune response and prevent the relapse of advanced prostate cancer.

Crk II silencing down-regulates IGF-IR and inhibits migration and invasion of prostate cancer cells

Crk (C10 regulator of kinase) adaptor proteins are highly expressed in many types of human cancers and often contribute to aggressive cancer phenotypes. Crk II, a member of CRK family, has been reported to regulate cell migration and metastasis in breast cancer cells. However, its role in other cancer types has not been reported. In this study, we investigated the molecular function of Crk II in prostate cancer (PCa) cells (CWR-22rv1) in vitro and using a mouse tumor model. Results showed that Crk II knockdown by shRNA-mediated silencing (Crk II-shRNA) in the PCa cells significantly inhibited both cancer cell migration and invasion in cell culture study. Crk II-shRNA cancer cells also significantly decreased colony formation in vitro, but had no significant reduction of tumor volume after 4 weeks of cancer cell xenografting in vivo when compared to the scramble control. Interestingly, Crk II-shRNA cancer cells showed a greatly reduced level of insulin-like growth factor 1 receptor (IGF-1R) and decreased signaling of the IGF-1R/PI3K/Akt axis upon IGF-1 ligand stimulation. A close interaction between Crk II and IGF-1R was demonstrated upon co-immunoprecipitation of IGF-1R with Crk II protein. Further, treatment of cells with either proteosomal degradation or protein synthesis inhibitor showed higher proportion of ubiquitin-associated IGF-1R and faster degradation of IGF-1R in Crk II-shRNA cells in comparison with that in the control cancer cells. Taken together, these data suggest that Crk II plays an important role in the regulation of IGF-1R protein stability and affects downstream of IGF-1R signaling pathways. Therefore, targeting Crk-II can block IGF-1R growth signaling and suppress cancer cell invasion and progression.

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Blocking Crk II inhibited cancer cell migration, invasion, and colony formation.

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Knockdown Crk II decreased IGF-1R protein and its downstream signaling.

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Crk II knockdown increased ubiquitination and degradation of IGF-1R.

Implication of NPM1 phosphorylation and preclinical evaluation of the nucleoprotein antagonist N6L in prostate cancer

Despite the advent of several new treatment options over the past years, advanced/metastatic prostate carcinoma (PCa) still remains incurable, which justifies the search for novel targets and therapeutic molecules. Nucleophosmin (NPM1) is a shuttling nucleoprotein involved in tumor growth and its targeting could be a potential approach for cancer therapy. We previously demonstrated that the multivalent pseudopeptide N6L binds to NPM1 potently affecting in vitro and in vivo tumor cell growth of various tumor types as well as angiogenesis. Furthermore, NPM1 binds to androgen receptor (AR) and modulate its activity. In this study, we first investigated the implication of the NPM1 and its Thr199 and Thr234/237 phosphorylated forms in PCa. We showed that phosphorylated forms of NPM1 interact with androgen receptor (AR) in nucleoplasm. N6L treatment of prostate tumor cells led to inhibition of NPM1 phosphorylation in conjunction with inhibition of AR activity. We also found that total and phosphorylated NPM1 were overexpressed in castration-resistant PCa. Assessment of the potential therapeutic role of N6L in PCa indicated that N6L inhibited tumor growth both in vitro and in vivo when used either alone or in combination with the standard-of-care first- (hormonotherapy) and second-line (docetaxel) treatments for advanced PCa. Our findings reveal the role of Thr199 and Thr234/237 phosphorylated NPM1 in PCa progression and define N6L as a new drug candidate for PCa therapy.

Identification of mutations, gene expression changes and fusion transcripts by whole transcriptome RNAseq in docetaxel resistant prostate cancer cells

Docetaxel has been the standard first-line therapy in metastatic castration resistant prostate cancer. The survival benefit is, however, limited by either primary or acquired resistance. In this study, Du145 prostate cancer cells were converted to docetaxel-resistant cells Du145-R and Du145-RB by in vitro culturing. Next generation RNAseq was employed to analyze these cell lines. Forty-two genes were identified to have acquired mutations after the resistance development, of which thirty-four were found to have mutations in published sequencing studies using prostate cancer samples from patients. Fourteen novel and 2 previously known fusion genes were inferred from the RNA-seq data, and 13 of these were validated by RT-PCR and/or re-sequencing. Four in-frame fusion transcripts could be transcribed into fusion proteins in stably transfected HEK293 cells, including MYH9-EIF3D and LDLR-RPL31P11, which were specific identified or up-regulated in the docetaxel resistant DU145 cells. A panel of 615 gene transcripts was identified to have significantly changed expression profile in the docetaxel resistant cells. These transcriptional changes have potential for further study as predictive biomarkers and as targets of docetaxel treatment.

Survival Outcomes of Concurrent Treatment with Docetaxel and Androgen Deprivation Therapy in Metastatic Castration-Resistant Prostate Cancer

PURPOSE

Docetaxel-based chemotherapy (DTX) improves overall survival (OS) of men with metastatic castration-resistant prostate cancer (mCRPC). Considering the potential existence of androgen receptors that remain active at this stage, we aimed to assess the impact of the combined use of androgen deprivation therapy (ADT) with DTX for mCRPC.

MATERIALS AND METHODS

We performed a single-institutional retrospective analysis of patients with mCRPC who received either DTX alone (DTX group, n=21) or concurrent DTX and ADT (DTX+ADT group, n=26) between August 2006 and February 2014. All patients received DTX doses of 75 mg/m² every three weeks for at least three cycles. In the DTX+ADT group, all patients used luteinizing hormone releasing hormone agonist continuously as a concurrent ADT.

RESULTS

The median follow-up period was 24.0 months (interquartile range 12.0-37.0) for the entire cohort. The median radiographic progression-free survival (rPFS) was 9.0 months and 6.0 months in the DTX+ADT and DTX groups, respectively (log-rank p=0.036). On multivariable Cox regression analysis, concurrent administration of ADT was the only significant predictor of rPFS [hazard ratio (HR)=0.525, 95% confidence intervals (CI) 0.284-0.970, p=0.040]. The median OS was 42.0 and 38.0 months in the DTX+ADT and DTX groups, respectively (log-rank p=0.796). On multivariable analysis, hemoglobin level at the time of DTX initiation was associated with OS (HR=0.532, 95% CI 0.381-0.744, p<0.001).

CONCLUSION

In chemotherapy-naive patients with mCRPC, the combined use of ADT with DTX improved rPFS. Our result suggests that the concurrent administration of ADT and DTX is superior to DTX alone.

Downregulation of c-SRC kinase CSK promotes castration resistant prostate cancer and pinpoints a novel disease subclass

SRC kinase is activated in castration resistant prostate cancer (CRPC), phosphorylates the androgen receptor (AR), and causes its ligand-independent activation as a transcription factor. However, activating SRC mutations are exceedingly rare in human tumors, and mechanisms of ectopic SRC activation therefore remain largely unknown. Performing a functional genomics screen, we found that downregulation of SRC inhibitory kinase CSK is sufficient to overcome growth arrest induced by depriving human prostate cancer cells of androgen. CSK knockdown led to ectopic SRC activation, increased AR signaling, and resistance to anti-androgens. Consistent with the in vitro observations, stable knockdown of CSK conferred castration resistance in mouse xenograft models, while sensitivity to the tyrosine kinase inhibitor dasatinib was retained. Finally, CSK was found downregulated in a distinct subset of CRPCs marked by AR amplification and ETS2 deletion but lacking PTEN and RB1 mutations. These results identify CSK downregulation as a principal driver of SRC activation and castration resistance and validate SRC as a drug target in a molecularly defined subclass of CRPCs.

Association of AR-V7 and Prostate-Specific Antigen RNA Levels in Blood with Efficacy of Abiraterone Acetate and Enzalutamide Treatment in Men with Prostate Cancer

PURPOSE

We evaluated the association of PSA and androgen receptor splice variant-7 (AR-V7) transcript levels in patients' blood with time to treatment failure (TTF) and overall survival (OS) with abiraterone acetate and/or enzalutamide treatment in castration-resistant prostate cancer (CRPC) patients.

EXPERIMENTAL DESIGN

RNA levels of AR-V7 and PSA in peripheral blood collected before treatment were quantified using droplet digital-PCR in retrospective cohorts treated with abiraterone acetate (N = 81) or enzalutamide (N = 51) for CRPC. Multivariable Cox regression adjusted for known prognostic factors was used for analyses.

RESULTS

PSA transcripts were detected in 57% of abiraterone acetate-treated patients and in 63% of enzalutamide-treated patients. PSA-positive patients had a shorter TTF than PSA-negative patients [adjusted HR = 2.27 (95% confidence interval (CI) 1.26-4.10) and 2.60 (95% CI, 1.19-5.69); P = 0.006 and 0.017 in abiraterone acetate and enzalutamide cohorts, respectively]. Patients with a higher-AR-V7 transcript level had a shorter TTF with abiraterone acetate and enzalutamide in univariate analysis (median 8.0 months vs. 15.6 months, P = 0.046 in abiraterone acetate-cohort and 3.6 months vs. 5.6 months; P = 0.050 in enzalutamide cohort). In multivariable models, the association with TTF remained significant in the enzalutamide cohort (adjusted HR = 2.02; 95% CI, 1.01-4.05; P = 0.048), but statistically insignificant in the abiraterone acetate cohort. In both cohorts, we observed potential prognostic value of both PSA and AR-V7 RNA expression on OS; patients with detectable PSA transcripts and high AR-V7 predicted the poorest OS.

CONCLUSIONS

PSA and AR-V7 transcripts in blood potentially serve as biomarkers predicting TTF and OS with abiraterone acetate or enzalutamide treatment. If validated prospectively, their detection could be facilitated without isolation of circulating tumor cells. Clin Cancer Res; 23(3); 726-34. ©2016 AACR.

Loss of exogenous androgen dependence by prostate tumor cells is associated with elevated glucuronidation potential

Prostate epithelial cells control the potency and availability of androgen hormones in part by inactivation and elimination. UDP-glucose dehydrogenase (UGDH) catalyzes the NAD(+)-dependent oxidation of UDP-glucose to UDP-glucuronate, an essential precursor for androgen inactivation by the prostate glucuronidation enzymes UGT2B15 and UGT2B17. UGDH expression is androgen stimulated, which increases the production of UDP-glucuronate and fuels UGT-catalyzed glucuronidation. In this study, we compared the glucuronidation potential and its impact on androgen-mediated gene expression in an isogenic LNCaP model for androgen-dependent versus castration-resistant prostate cancer. Despite significantly lower androgen-glucuronide output, LNCaP 81 castration-resistant tumor cells expressed higher levels of UGDH, UGT2B15, and UGT2B17. However, the magnitude of androgen-activated UGDH and prostate-specific antigen (PSA) expression, as well as the androgen receptor (AR)-dependent repression of UGT2B15 and UGT2B17, was blunted several-fold in these cells. Consistent with these results, the ligand-activated binding of AR to the PSA promoter and subsequent transcriptional activation were also significantly reduced in castration-resistant cells. Analysis of the UDP-sugar pools and flux through pathways downstream of UDP-glucuronate production revealed that these glucuronidation precursor metabolites were channeled through proteoglycan and glycosaminoglycan biosynthetic pathways, leading to increased surface expression of Notch1. Knockdown of UGDH diminished Notch1 and increased glucuronide output. Overall, these results support a model in which the aberrant partitioning of UDP-glucuronate and other UDP-sugars into alternative pathways during androgen deprivation contributes to the loss of prostate tumor cell androgen sensitivity by promoting altered cell surface proteoglycan expression.