Novel therapeutics for the management of castration-resistant prostate cancer (CRPC)

Targeting CBX3 with a Dual BET/PLK1 Inhibitor Enhances the Antitumor Efficacy of CDK4/6 Inhibitors in Prostate Cancer

The development of castration-resistant prostate cancer (CRPC) is a significant factor that reduces life expectancy among patients with prostate cancer. Previously, it is reported that CDK4/6 inhibitors can overcome the resistance of CRPC to BET inhibitors by destabilizing BRD4, suggesting that the combination of CDK4/6 inhibitors and BET inhibitors is a promising approach for treating CRPC. In this study, candidates that affect the combined antitumor effect of CDK4/6 inhibitors and BET inhibitors on CRPC is aimed to examine. The data demonstrates that CBX3 is abnormally upregulated in CDK4/6 inhibitors-resistant cells. CBX3 is almost positively correlated with the cell cycle in multiple malignancies and is downregulated by BET inhibitors. Mechanistically, it is showed that CBX3 is transcriptionally upregulated by BRD4 in CRPC cells. Moreover, it is demonstrated that CBX3 modulated the sensitivity of CRPC to CDK4/6 inhibitors by binding with RB1 to release E2F1. Furthermore, it is revealed that PLK1 phosphorylated CBX3 to enhance the interaction between RB1 and CBX3, and desensitize CRPC cells to CDK4/6 inhibitors. Given that BRD4 regulates CBX3 expression and PLK1 affects the binding between RB1 and CBX3, it is proposed that a dual BRD4/PLK1 inhibitor can increase the sensitivity of CRPC cells to CDK4/6 inhibitors partially through CBX3.

Effect of tumor CD276 expression on infiltrating immune cells and clinicopathological features of prostate cancer

BACKGROUND

Advanced prostate cancer (PCa) is often resistant to immunotherapy. In this study, we examined the role of CD276 in mediating immunotherapeutic effects through changes in immune cell infiltration.

METHODS

Using transcriptomic and proteomic analyses, CD276 was identified as a potential target for immunotherapy. Subsequent in vivo and in vitro experiments confirmed its role as a potential mediator of immunotherapeutic effects.

RESULTS

Multi-omic analysis suggested that CD276 was identified as a key molecule regulating the immune microenvironment (IM). In vivo experiments revealed that CD276 knockdown was found to enhance CD8⁺ T cell infiltration into the IM. Immunohistochemical analysis of PCa samples further confirmed the same findings.

CONCLUSION

CD276 was found to inhibit the enrichment of CD8+ T cells in PCa. Thus, CD276 inhibitors may be potential targets for immunotherapy.

Squalene epoxidase metabolic dependency is a targetable vulnerability in castration-resistant prostate cancer

Considering the dismal prognosis of castration-resistant prostate cancer (CRPC), it is critical to identify novel therapeutic targets in this disease. Malignant cells have metabolic dependencies distinct from their healthy counterparts, resulting in therapeutic vulnerabilities. While PTEN and TP53 are the most frequently co-mutated or co-deleted driver genes in lethal CRPC, the metabolic dependencies underlying PTEN/p53 deficiency-driven CRPC for therapeutic intervention remain largely elusive. In this study, PTEN/p53 deficient tumors were determined to be reliant on cholesterol metabolism. Moreover, PTEN/p53 deficiency transcriptionally upregulated squalene epoxidase (SQLE) via activation of sterol regulatory element-binding protein 2 (SREBP2). In addition, PTEN deficiency enhanced the protein stability of SQLE by inhibiting the PI3K/Akt/GSK3β-mediated proteasomal pathway. Consequently, SQLE increased cholesterol biosynthesis to facilitate tumor cell growth and survival. Pharmacological blockade of SQLE with FR194738 profoundly suppressed the invasive program of CRPC. Collectively, these results demonstrate a synergistic relationship between SQLE and PTEN/p53 deficiency in CRPC development and progression. Therefore, pharmacological interventions targeting SQLE may hold promise for the treatment of CRPC patients.

Early upregulation of AR and steroidogenesis enzyme expression after 3 months of androgen-deprivation therapy

Background

Androgen deprivation therapy (ADT) is a standard treatment for advanced prostate cancer (PCa). However, PCa recurrence and progression rates during ADT are high. Until now, there has been no evidence regarding when progression begins. This study evaluated the gene expression of intraprostatic androgen receptor (AR) and steroidogenic enzymes in the early stages of ADT.

Methods

Prostate tissue samples were taken from PCa patients with urinary retention who received ADT (ADT-PCa; n = 10) and were further subgrouped into ADT ≤12 months (n = 4) and ADT > 12 months (n = 6). The ADT-PCa tissues were then compared with BPH (n = 12) and primary (no treatment) PCa tissues (n = 16). mRNA for gene expression analysis of AR and steroidogenic enzymes was extracted from formalin-fixed paraffin embedded (FFPE) tissues and analyzed by real-time PCR. Protein expression was evaluated by immunohistochemistry with specific antibodies.

Results

AR gene expression was higher in the ADT-PCa group than in the BPH or primary PCa group. Both the ADT ≤12 and > 12 months subgroups had significantly higher relative gene expression levels of AR (p < 0.01 and 0.03, respectively) than the primary PCa group. In the ADT-PCa group, AR protein expression showed an increasing trend in the ADT ≤12 months subgroup and was significantly elevated in the ADT > 12 months subgroup compared with the PCa group (100%; p < 0.01). Half (50%) of the patients in the ADT ≤12 months subgroup were found to have upregulation of AR, and one showed upregulation beginning at 3 months of ADT. A trend toward elevated relative gene expression of SRD5A3 was also apparent in the ADT groups.

Conclusion

AR and steroidogenic enzymes are upregulated in ADT-PCa patients as early as 3 months, without PSA elevation. Steroidogenic enzymes, particularly SRD5A3, were also upregulated before PSA rose.

ATM‑JAK‑PD‑L1 signaling pathway inhibition decreases EMT and metastasis of androgen‑independent prostate cancer

Castration-resistant prostate cancer (CRPC), also known as androgen-independent prostate cancer, frequently develops local and distant metastases, the underlying mechanisms of which remain undetermined. In the present study, surgical specimens obtained from patients with clinical prostate cancer were investigated, and it was revealed that the expression levels of ataxia telangiectasia mutated kinase (ATM) were significantly enhanced in prostate cancer tissues isolated from patients with CRPC compared with from patients with hormone-dependent prostate cancer. CRPC C4-2 and CWR22Rv1 cells lines were subsequently selected to establish prostate cancer models, and ATM knockout cells were established via lentivirus infection. The results of the present study demonstrated that the migration and epithelial-mesenchymal transition (EMT) of ATM knockout cells were significantly decreased, which suggested that ATM is closely associated with CRPC cell migration and EMT. To further investigate the mechanisms underlying this process, programmed cell death 1 ligand 1 (PD-L1) expression was investigated in ATM knockout cells. In addition, inhibitors of Janus kinase (JAK) and signal transducer and activator of transcription 3 (STAT3; Stattic) were added to C4-2-Sc and CWR22Rv1-Sc cells, and the results demonstrated that PD-L1 expression was significantly decreased following the addition of JAK inhibitor 1; however, no significant change was observed following the addition of Stattic. Furthermore, a PD-L1 antibody and JAK inhibitor 1 were added to C4-2-Sc and CWR22Rv1-Sc cells, and it was revealed that cell migration ability was significantly decreased and the expression of EMT-associated markers was effectively reversed. The results of the present study suggested that via inhibition of the ATM-JAK-PD-L1 signaling pathway, EMT, metastasis and progression of CRPC may be effectively suppressed, which may represent a novel therapeutic approach for targeted therapy for patients with CRPC.

Biodistribution and Efficacy of Low Temperature-Sensitive Liposome Encapsulated Docetaxel Combined with Mild Hyperthermia in a Mouse Model of Prostate Cancer

PURPOSE

Low temperature sensitive liposome (LTSL) encapsulated docetaxel were combined with mild hyperthermia (40-42°C) to investigate in vivo biodistribution and efficacy against a castrate resistant prostate cancer.

METHOD

Female athymic nude mice with human prostate PC-3 M-luciferase cells grown subcutaneously into the right hind leg were randomized into six groups: saline (+/- heat), free docetaxel (+/- heat), and LTSL docetaxel (+/- heat). Treatment (15 mg docetaxel/kg) was administered via tail vein once tumors reached a size of 200-300 mm(3). Mice tumor volumes and body weights were recorded for up to 60 days. Docetaxel concentrations of harvested tumor and organ/tissue homogenates were determined by LC-MS. Histological evaluation (Mean vessel density, Ki67 proliferation, Caspase-3 apoptosis) of saline, free Docetaxel and LTSL docetaxel (+/- heat n = 3-5) was performed to determine molecular mechanism responsible for tumor cell killing.

RESULT

LTSL/heat resulted in significantly higher tumor docetaxel concentrations (4.7-fold greater compared to free docetaxel). Adding heat to LTSL Docetaxel or free docetaxel treatment resulted in significantly greater survival and growth delay compared to other treatments (p < 0.05). Differences in body weight between all Docetaxel treatments were not reduced by >10% and were not statistically different from each other. Molecular markers such as caspase-3 were upregulated, and Ki67 expression was significantly decreased in the chemo-hyperthermia group. Vessel density was similar post treatment, but the heated group had reduced vessel area, suggesting thermal enhancement in efficacy by reduction in functional perfusion.

CONCLUSION

This technique of hyperthermia sensitization and enhanced docetaxel delivery has potential for clinical translation for prostate cancer treatment.

Mechanism and Function of Angiogenin in Prostate Cancer

Angiogenin (ANG), the fifth member of the vertebrate-specific ribonuclease (RNase) A superfamily, is a secreted angiogenic ribonuclease strongly up-regulated in human prostate cancers. ANG is translocated to the nucleus in both prostate cancer epithelial cells and endothelial cells to exert its role in prostate cancer progression by mediating tumor angiogenesis, cancer cell survival and proliferation through rRNA biogenesis. ANG-stimulated rRNA is required not only for prostate intraepithelial neoplasia (PIN) formation, but also for androgen-independent growth of prostate cancer cells. Targeting ANG by various antagonists that inhibit its nuclear translocation, function and/or activity has proven to inhibit prostate cancer growth in animal models. Furthermore, the role of ANG in androgen independence has been firmly established, suggesting a strong rationale for therapeutically targeting ANG in the treatment of castration resistant prostate cancer.

Potential utility of cancer-specific biomarkers for assessing response to hormonal treatments in metastatic prostate cancer

Prostate cancer is the second leading cause of cancer death in men and there is an urgent clinical need to improve its detection and treatment. The introduction of prostate-specific antigen (PSA) as a biomarker for prostate cancer several decades ago represented an important step forward in our ability to diagnose this disease and offers the potential for earlier and more effective treatment. PSA measurements are now routinely conducted alongside digital rectal examination, with raised PSA levels leading to biopsy. PSA is also used to monitor disease and assess therapeutic response. However, there are some important limitations to its use, not least its lack of specificity for prostate cancer, and increased PSA screening may have resulted in overdiagnosis and overtreatment of early, low-risk prostate cancer. Therefore, there is a need for more specific and sensitive biomarkers for the diagnosis and monitoring of prostate cancer and treatment response; in particular, biomarkers of response to hormonal treatments in prostate cancer and predictive biomarkers to identify who is most likely to respond to these treatments. Here we review the current utilization of PSA and data on potentially more specific and sensitive biomarkers for the diagnosis and monitoring of prostate cancer: prostate cancer antigen 3 (PCA3) and the TMPRSS2-ERG fusion gene. A description of the design of an ongoing study of the 6-month extended release formulation of leuprorelin acetate (Eligard(®) 45 mg) will provide preliminary data on the potential utility of these new biomarkers for detecting therapeutic response after hormonal therapy.

Oxime bond-linked daunorubicin-GnRH-III bioconjugates exert antitumor activity in castration-resistant prostate cancer cells via the type I GnRH receptor

It is well established that gonadotropin-releasing hormone receptors (GnRH-R) are expressed in different types of cancers, including castration-resistant prostate cancer (CRPC) and mediate the antiproliferative effect of GnRH analogs. Thus, these compounds are employed as targeting moieties to selectively deliver chemotherapeutic agents to cancer cells. GnRH-III, the decapeptide isolated from the sea lamprey brain, has lower potency than GnRH in stimulating gonadotropin secretion, but it exerts antiproliferative effects on many tumors expressing the GnRH-R. GnRH-III-based peptides are considered promising targeting moieties for the preparation of anticancer drug delivery systems. These studies were aimed at i) evaluating the antitumor activity of two cytotoxic oxime bond-linked daunorubicin (Dau)-GnRH-III derivative bioconjugates (Dau-GnRH-III, in which daunorubicin was coupled to the 8Lys in the native form of GnRH-III, and Dau-[4Lys(Ac)]-GnRH-III, in which daunorubicin was attached to the 8Lys of a GnRH-III derivative where 4Ser was replaced by an acetylated lysine) on CRPC cells; and ii) to elucidate the involvement of the classical GnRH-R (type I GnRH-R) in this antitumor activity. Our results demonstrated that both Dau-GnRH-III and Dau-[4Lys(Ac)]-GnRH-III were rapidly internalized into DU145 prostate cancer cells and exerted a significant cytostatic effect. Both bioconjugates increased the levels of the active form of caspase-3, indicating the involvement of apoptosis in their antitumor activity. The antiproliferative effect of both Dau-GnRH-III and Dau-[4Lys(Ac)]-GnRH-III was counteracted by the simultaneous treatment of the cells with Antide, an antagonist of the GnRH-R. Moreover, after silencing the type I GnRH-R the antitumor activity of both bioconjugates was completely abolished. These data demonstrate that in CRPC cells, daunorubicin-GnRH-III derivative bioconjugates: i) inhibit tumor cell proliferation, by triggering the apoptosis process; ii) exert their antitumor effect through the activation of the type I GnRH-R expressed on these cells. Cytotoxic-GnRH-III derivative may represent promising targeted chemotherapeutics for the treatment of CRPC patients.

A hormone-dependent feedback-loop controls androgen receptor levels by limiting MID1, a novel translation enhancer and promoter of oncogenic signaling

BACKGROUND

High androgen receptor (AR) level in primary tumour predicts increased prostate cancer (PCa)-specific mortality. Furthermore, activations of the AR, PI3K, mTOR, NFκB and Hedgehog (Hh) signaling pathways are involved in the fatal development of castration-resistant prostate cancer during androgen ablation therapy. MID1, a negative regulator of the tumor-suppressor PP2A, is known to promote PI3K, mTOR, NFκB and Hh signaling. Here we investigate the interaction of MID1 and AR.

METHODS

AR and MID1 mRNA and protein levels were measured by qPCR, Western blot and immunohistochemistry. Co-immunoprecipitation followed by PCR and RNA-pull-down followed by Western blot was used to investigate protein-mRNA interaction, chromatin-immunoprecipitation followed by next-generation sequencing for identification of AR chromatin binding sites. AR transcriptional activity and activity of promoter binding sites for AR were analyzed by reporter gene assays. For knockdown or overexpression of proteins of interest prostate cancer cells were transfected with siRNA or expression plasmids, respectively.

RESULTS

The microtubule-associated MID1 protein complex associates with AR mRNA via purine-rich trinucleotide repeats, expansions of which are known to correlate with ataxia and cancer. The level of MID1 directly correlates with the AR protein level in PCa cells. Overexpression of MID1 results in a several fold increase in AR protein and activity without major changes in mRNA-levels, whereas siRNA-triggered knockdown of MID1 mRNA reduces AR-protein levels significantly. Upregulation of AR protein by MID1 occurs via increased translation as no major changes in AR protein stability could be observed. AR on the other hand, regulates MID1 via several functional AR binding sites in the MID1 gene, and, in the presence of androgens, exerts a negative feedback loop on MID1 transcription. Thus, androgen withdrawal increases MID1 and concomitantly AR-protein levels. In line with this, MID1 is significantly over-expressed in PCa in a stage-dependent manner.

CONCLUSION

Promotion of AR, in addition to enhancement of the Akt-, NFκB-, and Hh-pathways by sustained MID1-upregulation during androgen deprivation therapy provides a powerful proliferative scenario for PCa progression into castration resistance. Thus MID1 represents a novel, multi-faceted player in PCa and a promising target to treat castration resistant prostate cancer.

The effects of nonspecific HIF1α inhibitors on development of castrate resistance and metastases in prostate cancer

Expression of hypoxia-inducible factor (HIF)1α increases the risk of castrate-resistant prostate cancer (CRPC) and metastases in patients on androgen deprivation therapy (ADT) for prostate cancer (PC). We aimed to investigate the effects of nonspecific HIF1α inhibitors (Digoxin, metformin, and angiotensin-2 receptor blockers) on development of CRPC and metastases while on ADT. A retrospective review of prospectively collected medical records was conducted of all men who had continuous ADT as first-line therapy for CRPC at the Austin Hospital from 1983 to 2011. Association between HIF1α inhibitor medications and time to develop CRPC was investigated using actuarial statistics. Ninety-eight patients meeting the criteria were identified. Eighteen patients (21.4%) were treated with the nonspecific HIF1α inhibitors. Both groups had similar characteristics, apart from patients on HIF1α inhibitors being older (70 years vs. 63.9 years). The median CRPC-free survival was longer in men using HIF1α inhibitors compared to those not on inhibitors (6.7 years vs. 2.7 years, P = 0.01) and there was a 71% reduction in the risk of developing CRPC (HR 0.29 [95% CI 0.10-0.78] P = 0.02) after adjustment for Gleason score, age, and prostate-specific antigen (PSA). The median metastasis-free survival in men on HIF1α inhibitors was also significantly longer compared to those on no inhibitors (5.1 years vs. 2.6 years, P = 0.01) with an 81% reduction in the risk of developing metastases (HR 0.19 [CI 0.05-0.76] P = 0.02) after adjustment for Gleason score, age, and PSA. Nonspecific HIF1α inhibitors appear to increase the progression-free survival and reduce the risk of developing CRPC and metastases in patients on continuous ADT.

Prolonged exposure to (R)-bicalutamide generates a LNCaP subclone with alteration of mitochondrial genome

Advanced prostate cancers, initially sensitive to androgen deprivation therapy, frequently progress to the castration-resistant prostate cancer phenotype (CRPC) through mechanisms not yet fully understood. In this study we investigated mitochondrial involvement in the establishment of refractoriness to hormone therapy. Two human prostate cancer cell lines were used, the parental LNCaP and the resistant LNCaP-Rbic, the latter generated after continuous exposure to 20 μM of (R)-bicalutamide, the active enantiomer of Casodex®. We observed a significant decrease in mtDNA content and a lower expression of 8 mitochondria-encoded gene transcripts involved in respiratory chain complexes in both cell lines. We also found that (R)-bicalutamide differentially modulated dynamin-related protein (Drp-1) expression in LNCaP and LNCaP-Rbic cells. These data seem to indicate that the androgen-independent phenotype in our experimental model was due, at least in part, to alterations in mitochondrial dynamics and to a breakdown in the Drp-1-mediated mitochondrial network.

Pain questionnaire performance in advanced prostate cancer: comparative results from two international clinical trials

PURPOSE

To compare pain assessment questionnaires commonly used in advanced prostate cancer trials and to determine the psychometric characteristics and longitudinal relationships by contrasting questionnaire data from two international phase 2 trials.

METHODS

Scores from the Present Pain Intensity (PPI) question of the McGill Pain Questionnaire, the pain intensity scale of the Brief Pain Inventory (BPI), and the Functional Assessment of Cancer Therapy-Prostate (FACT-P) were analyzed using Pearson correlation, intraclass correlation coefficient, and Cronbach's α, respectively. Concordance was evaluated with Cohen's kappa coefficient and McNemar test at baseline (n = 224) and two subsequent observations.

RESULTS

PPI and FACT-P scores were associated with the BPI score at baseline for Trials 1 and 2: PPI r = 0.66 and 0.80, respectively (P < 0.001); FACT-P (pain scale) r = -0.76 and -0.82, respectively (P < 0.001). However, concordance analysis revealed that the BPI identified pain (score > 0) at higher rates than the PPI: at baseline, BPI: 89 % (64/72) and 77 % (95/124), PPI: 68 % (49/72) and 64 % (79/124) [Trials 1 and 2, respectively; McNemar test (P < 0.001) for both studies]. The FACT-P pain scale identified pain similarly to the BPI pain intensity scale; longitudinal analysis produced comparable findings. All pain scales met standard psychometric acceptability criteria, but the BPI and FACT-P performed better than the PPI.

CONCLUSIONS

Data suggest the BPI pain intensity and FACT-P pain scales are better than the PPI question at capturing the pain experience among patients with advanced prostate cancer. Additional comparative research is needed in larger population samples.

The combination of plumbagin with androgen withdrawal causes profound regression of prostate tumors in vivo

BACKGROUND

Hormonal ablation is the standard treatment for disseminated androgen-dependent prostate cancer. Although tumor growth is controlled at first, the tumor invariably recurs in the form of castration-resistant prostate cancer. This study assessed the efficacy of a new therapeutic strategy that combines plumbagin, a naturally occurring naphthoquinone, with androgen ablation.

METHODS

Viewing microscopy chambers were placed in the dorsal skinfold of mice. Syngeneic prostate tissue was grafted within the chambers and allowed to vascularize. H2B-GFP/PTEN-P2 prostate cancer cells were co-implanted on top of the grafted prostate tissue. Androgen ablation was achieved using surgical castration. Intact and castrated mice were administered plumbagin or sham treatment. Tumor growth, mitosis and apoptosis were monitored in real-time using fluorescent Intra-Vital Microscopy. The mechanism of action of plumbagin was explored using human and mouse prostate cancer cells.

RESULTS

Whereas both plumbagin and castration alone impeded tumor growth, only the combination of plumbagin and castration caused profound tumor regression in vivo, mostly due to increased apoptosis of the tumor cells. The cytotoxicity of plumbagin was not affected by androgens in vitro, suggesting that microenvironmental factors not present in culture play a crucial role in the combination effect. Plumbagin-induced cell death was mediated, at least in part, by activation of ERK and was due to generation of reactive oxygen species, because it was abolished by the anti-oxidant N-acetyl-L-cysteine.

CONCLUSION

Androgen deprivation in combination with plumbagin may provide a significant improvement over androgen deprivation alone and deserves further evaluation.

[Change of the LHRH analogue in progressive castration-refractory prostate cancer]

INTRODUCTION

Medicinal or surgical castration remains the treatment of choice in metastatic, hormone-naive prostate cancer; however, 2-12% of patients never reach the target serum levels for medicinal castration. We analyzed the therapeutic efficacy of triptorelin pamoate (TP) as salvage treatment due to its higher potency than endogenous luteinizing hormone-releasing hormone (LHRH). The amino acid sequence of TP is identical to that of endogenous LHRH except for position 6 where L-glycine is replaced by D-tryptophane rendering the synthetic moiety less susceptible to cleavage by proteolytic enzymes.

PATIENTS AND METHODS

In this study 36 patients with prostate-specific antigen (PSA) progression following first line complete androgen blockade and antiandrogen (ADT) withdrawal were retrospectively analyzed. All patients demonstrated no or minimal metastatic disease. The PSA levels, PSA doubling time (PSADT), PSA velocity (PSAV) and testosterone serum concentrations were correlated with the therapeutic response. All patients received TP at a dose of 11.5 mg at 3-month intervals until documented progression.

RESULTS

The mean patient age was 69.2 years (range 52-79 years), the mean PSA level was 23.4 ng/ml (8.7-53.1 ng/ml) and the mean PSADT was 9.2 months (2.9-15.4 months). Mean testosterone serum concentration was 38.67 ng/dl (21-76 ng/dl), the mean time between start of ADT and progression was 42.4 months (13-76 months) and the median time was 46.8 months (16-82 months). A PSA decrease of ≥50% was reached in 9 out of 36 (25%) patients, 3 out of 36 (13.9%) patients each demonstrated stable PSA levels and a prolongation of PSADT from 6.2 to 9.8 months. Mean progression-free survival (PFS) was 21.4 weeks (7-53 weeks). PSA-responders exhibited a PFS of 53.2 weeks (26-64 weeks) as compared to 28 weeks (17-35 weeks) in nonresponders. PSA responders demonstrated significantly higher testosterone serum concentrations of 48.3 ng/dl (29-76 ng/dl) as compared to nonresponders with 32.6 ng/dl (21-62 ng/dl, p=0.02). Mean follow-up was 31.4 months (27-39 months), overall survival was 80.5% and cancer-specific survival was 88.9%.

CONCLUSION

Changing the LHRH analogue in castration-refractory prostate cancer (CRPC) with testosterone serum concentrations at or above the castration level results in a temporary PSA response. This treatment option might be included in the therapeutic algorithm of CRPC. Although the PFS is short it allows the continuation of a treatment option with minimal side effects in a mere palliative situation. The data underline the need for continuous monitoring of testosterone during treatment with LHRH analogues.

Aldo-keto reductase family 1 member C3 (AKR1C3) is a biomarker and therapeutic target for castration-resistant prostate cancer

Current endocrine treatment for advanced prostate cancer does not result in a complete ablation of adrenal androgens. Adrenal androgens can be metabolized by prostate cancer cells, which is one of the mechanisms associated with progression to castration-resistant prostate cancer (CRPC). Aldo-keto reductase family 1 member C3 (AKR1C3) is a steroidogenic enzyme that plays a crucial role in the conversion of adrenal androgen dehydroepiandrosterone (DHEA) into high-affinity ligands for the androgen receptor (testosterone [T] and dihydrotestosterone [DHT]). The aim of this study was to examine whether AKR1C3 could be used as a marker and therapeutic target for CRPC. AKR1C3 mRNA and protein levels were upregulated in CRPC tissue, compared with benign prostate and primary prostate cancer tissue. High AKR1C3 levels were found only in a subset of CRPC patients. AKR1C3 can be used as a biomarker for active intratumoral steroidogenesis and can be measured in biopsy or transurethral resection of the prostate specimens. DuCaP (a CRPC cell line that has high AKR1C3 expression levels) used and converted DHEA under hormone-depleted conditions into T and DHT. The DHEA-induced growth of DuCaP could be antagonized by indomethacine, an inhibitor of AKR1C3. This study indicates that AKR1C3 can be considered a therapeutic target in a subgroup of patients with high AKR1C3 expression.

The circadian clock in cancer development and therapy

Most aspects of mammalian function display circadian rhythms driven by an endogenous clock. The circadian clock is operated by genes and comprises a central clock in the brain that responds to environmental cues and controls subordinate clocks in peripheral tissues via circadian output pathways. The central and peripheral clocks coordinately generate rhythmic gene expression in a tissue-specific manner in vivo to couple diverse physiological and behavioral processes to periodic changes in the environment. However, with the industrialization of the world, activities that disrupt endogenous homeostasis with external circadian cues have increased. This change in lifestyle has been linked to an increased risk of diseases in all aspects of human health, including cancer. Studies in humans and animal models have revealed that cancer development in vivo is closely associated with the loss of circadian homeostasis in energy balance, immune function, and aging, which are supported by cellular functions important for tumor suppression including cell proliferation, senescence, metabolism, and DNA damage response. The clock controls these cellular functions both locally in cells of peripheral tissues and at the organismal level via extracellular signaling. Thus, the hierarchical mammalian circadian clock provides a unique system to study carcinogenesis as a deregulated physiological process in vivo. The asynchrony between host and malignant tissues in cell proliferation and metabolism also provides new and exciting options for novel anticancer therapies.

Moving toward personalized medicine in castration-resistant prostate cancer

Recent advances in research technologies have allowed improved molecular characterization of castration-resistant prostate cancer (CRPC). These efforts hold promise for development of therapies that target alterations unique to an individual patient's prostate cancer. Targets include androgens and the androgen receptor pathway, pathways associated with hormone-resistant disease, and the immune system. In aggregate, this will allow physicians to choose treatments based on a particular tumor profile. As these approaches are developed, CRPC treatment is becoming an example of truly personalized medicine.

From sequence to molecular pathology, and a mechanism driving the neuroendocrine phenotype in prostate cancer

The current paradigm of cancer care relies on predictive nomograms which integrate detailed histopathology with clinical data. However, when predictions fail, the consequences for patients are often catastrophic, especially in prostate cancer where nomograms influence the decision to therapeutically intervene. We hypothesized that the high dimensional data afforded by massively parallel sequencing (MPS) is not only capable of providing biological insights, but may aid molecular pathology of prostate tumours. We assembled a cohort of six patients with high-risk disease, and performed deep RNA and shallow DNA sequencing in primary tumours and matched metastases where available. Our analysis identified copy number abnormalities, accurately profiled gene expression levels, and detected both differential splicing and expressed fusion genes. We revealed occult and potentially dormant metastases, unambiguously supporting the patients' clinical history, and implicated the REST transcriptional complex in the development of neuroendocrine prostate cancer, validating this finding in a large independent cohort. We massively expand on the number of novel fusion genes described in prostate cancer; provide fresh evidence for the growing link between fusion gene aetiology and gene expression profiles; and show the utility of fusion genes for molecular pathology. Finally, we identified chromothripsis in a patient with chronic prostatitis. Our results provide a strong foundation for further development of MPS-based molecular pathology.

[Role of chemotherapy in castration-resistant prostate cancer: are there new approaches?]

Chemotherapy options for the treatment of metastatic castration-resistant prostate cancer (CRPC) have been very limited for many decades. Until 2004, only mitoxantrone was approved, providing palliation, but no survival benefit. With the introduction of docetaxel, the landscape of chemotherapy for CRPC changed substantially. Prednisone and three-weekly docetaxel showed an overall survival (OS) benefit compared to mitoxantrone plus prednisone, in addition to a significant improvement of quality of life and pain reduction. Further strategies to treat CRPC with chemotherapy include reinduction with docetaxel in responding patients and the use of cabazitaxel, a novel semi-synthetic microtubule inhibitor, in the docetaxel-refractory population. This review article is meant to guide physicians through the optimal use of chemotherapy in CRPC patients in daily clinical practice.