Castration-resistant prostate cancer: from new pathophysiology to new treatment targets

The natural compound periplogenin suppresses the growth of prostate carcinoma cells by directly targeting ATP1A1

Natural compounds constitute a major resource for the development of medicines for multiple diseases. While many natural compounds show strong biological activity, the mechanisms that confer clinical benefits are often elusive and have been attributed to multiple pathways. Periplogenin (PPG), a natural compound isolated from Cortex periplocae, exhibits strong anti-tumor activities in several human cancer cell lines. However, its molecular mode of action remained unclear. In this study, we leveraged a forward genetic screening approach in DU145 prostate cancer cells to uncover the molecular target of PPG using chemical mutagenesis. Next generation sequencing revealed that a single amino acid substitution at amino acid 804 in ATP1A1 (ATPase Na + /K + Transporting Subunit Alpha 1) confers resistance to the cytotoxic activity of PPG. Mechanistically, ATP1A1 T804 forms a hydrogen bond with PPG which is abolished by the T804A substitution in ATP1A1, resulting in resistance to PPG treatment in vitro. Importantly, in vivo, PPG strongly suppressed tumor development in a DU145 xenograft model whereas DU145 xenograft tumors carrying a ATP1A1-T804A mutation were largely unaffected by the treatment. These findings demonstrate that PPG suppresses the growth of DU145 prostate cancer cells in vitro and in vivo by directly binding to ATP1A1 and highlight the power of our unbiased forward genetic screening approach to uncover direct drug target structures at single amino acid resolution.

TrkA promotes MDM2-mediated AGPS ubiquitination and degradation to trigger prostate cancer progression

BACKGROUND

As a novel necrosis manner, ferroptosis has been increasingly reported to play a role in tumor progression and treatment, however, the specific mechanisms underlying its development in prostate cancer remain unclear. Growing evidence showed that peroxisome plays a key role in ferroptosis. Herein, we identified a novel mechanism for the involvement of ferroptosis in prostate cancer progression, which may provide a new strategy for clinical treatment of prostate cancer.

METHODS

Label-Free Mass spectrometry was used to screen and identify candidate proteins after ferroptosis inducer-ML210 treatment. Immunohistochemistry was undertaken to explore the protein expression of AGPS in prostate cancer tissues compared with normal tissues. Co-immunoprecipitation and GST pull-down were used to identify the directly binding of AGPS to MDM2 in vivo and in vitro. CCK8 assay and colony formation assay were used to illustrate the key role of AGPS in the progression of prostate cancer in vitro. The xenograft model was established to verify the key role of AGPS in the progression of prostate cancer in vivo.

RESULTS

AGPS protein expression was downregulated in prostate cancer tissues compared with normal tissues from the first affiliated hospital of Zhengzhou University dataset. Lower expression was correlated with poorer overall survival of patients compared to those with high expression of AGPS. In addition, AGPS can promote ferroptosis by modulating the function of peroxisome-resulting in the lower survival of prostate cancer cells. Furthermore, it was shown that AGPS can be ubiquitinated and degraded by the E3 ligase-MDM2 through the proteasomal pathway. Meanwhile, kinase TrkA can promote the combination of AGPS and MDM2 by phosphorylating AGPS at Y451 site. It was verified that kinase TrkA inhibitor-Larotrectinib can increase the susceptibility of prostate cancer cells to ferroptosis, which leads to the inhibition of prostate cancer proliferation to a great extent in vitro and in vivo.

CONCLUSION

Based on these findings, we proposed the combination of ferroptosis inducer and TrkA inhibitor to synergistically exert anti-tumor effects, which may provide a new strategy for the clinical treatment of prostate cancer.

TPM2 attenuates progression of prostate cancer by blocking PDLIM7-mediated nuclear translocation of YAP1

BACKGROUND

Prostate cancer (PCa) is a common malignant tumor of the genitourinary system. Clinical intervention in advanced PCa remains challenging. Tropomyosins 2 (TPM2) are actin-binding proteins and have been found as a biomarker candidate for certain cancers. However, no studies have explored the role of TPM2 in PCa and its regulatory mechanism.

METHODS

TPM2 expression was assessed in Gene Expression Omnibus (GEO) and the Cancer Genome Atlas (TCGA) PCa patient dataset. The effect of TPM2 on PCa progression was assessed in vitro and in vivo by quantifying proliferation, migration, invasion and tumor growth assays, and the mechanism of TPM2 in PCa progression was gradually revealed by Western blotting, immunoprecipitation, and immunofluorescence staining arrays.

RESULTS

TPM2 was found to be severely downregulated in tumor tissues of PCa patients compared with tumor-adjacent normal tissues. In vitro experiments revealed that TPM2 overexpression inhibited PCa cell proliferation, invasion and androgen-independent proliferation. Moreover, TPM2 overexpression inhibited the growth of subcutaneous xenograft tumors in vivo. Mechanistically, this effect was noted to be dependent on PDZ-binding motif of TPM2. TPM2 competed with YAP1 for binding to PDLIM7 through the PDZ-binding motif. The binding of TPM2 to PDLIM7 subsequently inhibited the nuclear transport function of PDLIM7 for YAP1. YAP1 sequestered in the cytoplasm phosphorylated at S127, resulting in its inactivation or degradation which in turn inhibited the expression of YAP1 downstream target genes.

CONCLUSIONS

This study investigated the role of TPM2, PDLIM7, and YAP1 in PCa progression and castration resistance. TPM2 attenuates progression of PCa by blocking PDLIM7-mediated nuclear translocation of YAP1. Accordingly, targeting the expression or functional modulation of TPM2, PDLIM7, or YAP1 has the potential to be an effective therapeutic approach to reduce PCa proliferation and prevent the progression of castration-resistant prostate cancer (CRPC).

The Mangrove-Derived Diterpenoid Diaporthe B Inhibits the Stemness and Increases the Efficacy of Docetaxel in Prostate Cancer PC-3 Cells

The absolute configuration of diaporthe B, a pimarane diterpene isolated from the mangrove derived endophytic fungus Eutypella sp #3E, was determined by a single-crystal x-ray diffraction study. The present study aimed to investigate the effects of diaporthe B on docetaxel-resistant prostate cancer PC-3 cells. Results of our studies showed that docetaxel-resistant PC-3 cells had higher sphere-forming efficiency and an increase in adherence to collagen-coated culture plates. The protein levels of cancer stem cell (CSC)-related markers CD44, CD133, and ALDH1A1 were higher in the docetaxel-resistant PC-3 cells than in the parental cells. Treatment with diaporthe B dose-dependently inhibited the growth and induced apoptosis in the resistant cells. Moreover, diaporthe B treatment decreased the sphere-forming efficiency and the adherence to collagen-coated plates in docetaxel-resistant PC-3 cells. Diaporthe B also decreased the protein levels of CSC-related markers CD44, CD133, and ALDH1A1 in the resistant cells. In addition, a combination of diaporthe B and docetaxel had a more potent effect on growth inhibition and apoptosis in the resistant cells than either agent alone. Our studies suggest that diaporthe B inhibits the stemness of prostate cancer cells and may have therapeutic potential for enhancing the efficacy of docetaxel in docetaxel-resistant prostate cancer cells.

Fatty Acid Metabolism Reprogramming in Advanced Prostate Cancer

Prostate cancer (PCa) is a carcinoma in which fatty acids are abundant. Fatty acid metabolism is rewired during PCa development. Although PCa can be treated with hormone therapy, after prolonged treatment, castration-resistant prostate cancer can develop and can lead to increased mortality. Changes to fatty acid metabolism occur systemically and locally in prostate cancer patients, and understanding these changes may lead to individualized treatments, especially in advanced, castration-resistant prostate cancers. The fatty acid metabolic changes are not merely reflective of oncogenic activity, but in many cases, these represent a critical factor in cancer initiation and development. In this review, we analyzed the literature regarding systemic changes to fatty acid metabolism in PCa patients and how these changes relate to obesity, diet, circulating metabolites, and peri-prostatic adipose tissue. We also analyzed cellular fatty acid metabolism in prostate cancer, including fatty acid uptake, de novo lipogenesis, fatty acid elongation, and oxidation. This review broadens our view of fatty acid switches in PCa and presents potential candidates for PCa treatment and diagnosis.

AK-I-190, a New Catalytic Inhibitor of Topoisomerase II with Anti-Proliferative and Pro-Apoptotic Activity on Androgen-Negative Prostate Cancer Cells

Castration-resistant prostate cancer (CRPC) is a clinical challenge in treatment because of its aggressive nature and resistance to androgen deprivation therapy. Topoisomerase II catalytic inhibitors have been suggested as a strategy to overcome these issues. We previously reported AK-I-190 as a novel topoisomerase II inhibitor. In this study, the mechanism of AK-I-190 was clarified using various types of spectroscopic and biological evaluations. AK-I-190 showed potent topoisomerase II inhibitory activity through intercalating into DNA without stabilizing the DNA-enzyme cleavage complex, resulting in significantly less DNA toxicity than etoposide, a clinically used topoisomerase II poison. AK-I-190 induced G1 arrest and effectively inhibited cell proliferation and colony formation in combination with paclitaxel in an androgen receptor–negative CRPC cell line. Our results confirmed that topoisomerase II catalytic inhibition inhibited proliferation and induced apoptosis of AR-independently growing prostate cancer cells. These findings indicate the clinical relevance of topoisomerase II catalytic inhibitors in androgen receptor-negative prostate cancer.

miRNAs and androgen deprivation therapy for prostate cancer

Androgen deprivation therapy (ADT) is mainly used for the treatment of advanced, metastatic or recurrent prostate cancer (PCa). However, patients progress to ADT resistance and castration-resistant prostate cancer (CRPC) with a poor prognosis. Reliable validated markers of ADT resistance with proven clinical utility are necessary for timely correction of the therapy as well as for improvement of patient quality of life. MiRNAs involved in the ADT response and CRPC development via multiple mechanisms may act as biomarkers for patient outcomes. Available data on miRNAs associated with the ADT response (resistance and sensitivity) are summarized and analyzed in the manuscript, including analyses using bioinformatics resources. Molecular targets of miRNAs, as well as reciprocal relations between miRNAs and their targets, were studied using different databases. Special attention was dedicated to the mechanisms of ADT resistance and CRPC development, including testosterone, PI3K-AKT, VEGF pathways and associated genes. Several different approaches can be used to search for miRNAs associated with the ADT response, each of which focuses on the associated set of miRNAs - potential markers of ADT. The intersection of these approaches and combined analysis allowed us to select the most promising miRNA markers of the ADT response. Meta-analysis of the current data indicated that the selected 5 miRNAs (miRNAs - 125b, miR-21, miR-23b, miR-27b and miR-221) and 14 genes are involved in the regulation of key processes of CRPC development and represent the most promising predictors of the ADT response, further demonstrating their potential in combination therapy for advanced PCa.

PSMA-targeted arsenic nanosheets: a platform for prostate cancer therapy via ferroptosis and ATM deficiency-triggered chemosensitization

Ferroptosis, a newly recognized form of non-apoptotic cell death, has recently been introduced for effective cancer therapy. The reported ferroptosis-inducing nanomaterials mainly consisted of metal-based components. Herein, we designed an inorganic metal-free nanoplatform, PSMA-targeted arsenic nanosheets (PMANs), which simultaneously increased glutathione (GSH) consumption, suppressed solute carrier family 7 member 11 (SLC7A11) and glutathione-dependent peroxidase 4 (GPX4) expression, and promoted the generation of reactive oxygen species (ROS) and lipid peroxides (LPO). In addition, owing to the large surface area, PMANs efficiently transported doxorubicin (DOX) to prostate cancer for synergistic therapy. Surprisingly, we found that PMANs could sensitize prostate cancer cells to DOX through downregulating the expression of ataxia telangiectasia mutated (ATM), which further augmented the GPX4 downregulation-mediated ferroptotic tumoricidal effect. Given that arsenic trioxide has been routinely and successfully used in the clinical treatment of leukemia for a long time, we anticipate that PMANs will offer a promising strategy for prostate cancer therapy.

Improving Strategies in the Development of Protein-Downregulation-Based Antiandrogens

The androgen receptor (AR) plays a crucial role in the occurrence and development of prostate cancer (PCa), and its signaling pathway remains active in castration-resistant prostate cancer (CRPC) patients. The resistance against antiandrogen drugs in current clinical use is a major challenge for the treatment of PCa, and thus the development of new generations of antiandrogens is under high demand. Recently, strategies for downregulating the AR have attracted significant attention, given its potential in the discovery and development of new antiandrogens, including G-quadruplex stabilizers, ROR-γ inhibitors, AR-targeting proteolysis targeting chimeras (PROTACs), and other selective AR degraders (SARDs), which are able to overcome current resistance mechanisms such as acquired AR mutations, the expression of AR variable splices, or overexpression of AR. This review summarizes the various strategies for downregulating the AR protein, at either the mRNA or protein level, thus providing new ideas for the development of promising antiandrogen drugs.

MYBL2 disrupts the Hippo-YAP pathway and confers castration resistance and metastatic potential in prostate cancer

Rationale: Resistance to androgen-deprivation therapy (ADT) associated with metastatic progression remains a challenging clinical task in prostate cancer (PCa) treatment. Current targeted therapies for castration-resistant prostate cancer (CRPC) are not durable. The exact molecular mechanisms mediating resistance to castration therapy that lead to CRPC progression remain obscure. Methods: The expression of MYB proto-oncogene like 2 (MYBL2) was evaluated in PCa samples. The effect of MYBL2 on the response to ADT was determined by in vitro and in vivo experiments. The survival of patients with PCa was analyzed using clinical specimens (n = 132) and data from The Cancer Genome Atlas (n = 450). The mechanistic model of MYBL2 in regulating gene expression was further detected by subcellular fractionation, western blotting, quantitative real-time PCR, chromatin immunoprecipitation, and luciferase reporter assays. Results: MYBL2 expression was significantly upregulated in CRPC tissues and cell lines. Overexpression of MYBL2 could facilitate castration-resistant growth and metastatic capacity in androgen-dependent PCa cells by promoting YAP1 transcriptional activity via modulating the activity of the Rho GTPases RhoA and LATS1 kinase. Importantly, targeting MYBL2, or treatment with either the YAP/TAZ inhibitor Verteporfin or the RhoA inhibitor Simvastatin, reversed the resistance to ADT and blocked bone metastasis in CRPC cells. Finally, high MYBL2 levels were positively associated with TNM stage, total PSA level, and Gleason score and predicted a higher risk of metastatic relapse and poor prognosis in patients with PCa. Conclusions: Our results reveal a novel molecular mechanism conferring resistance to ADT and provide a strong rationale for potential therapeutic strategies against CRPC.

Ferroptosis Inducers Are a Novel Therapeutic Approach for Advanced Prostate Cancer

Ferroptosis is a type of programmed cell death induced by the accumulation of lipid peroxidation and lipid reactive oxygen species in cells. It has been recently demonstrated that cancer cells are vulnerable to ferroptosis inducers (FIN). However, the therapeutic potential of FINs in prostate cancer in preclinical settings has not been explored. In this study, we demonstrate that mediators of ferroptosis, solute carrier family 7 member 11, SLC3A2, and glutathione peroxidase, are expressed in treatment-resistant prostate cancer. We further demonstrate that treatment-resistant prostate cancer cells are sensitive to two FINs, erastin and RSL3. Treatment with erastin and RSL3 led to a significant decrease in prostate cancer cell growth and migration in vitro and significantly delayed the tumor growth of treatment-resistant prostate cancer in vivo, with no measurable side effects. Combination of erastin or RSL3 with standard-of-care second-generation antiandrogens for advanced prostate cancer halted prostate cancer cell growth and migration in vitro and tumor growth in vivo. These results demonstrate the potential of erastin or RSL3 independently and in combination with standard-of-care second-generation antiandrogens as novel therapeutic strategies for advanced prostate cancer. SIGNIFICANCE: These findings reveal that induction of ferroptosis is a new therapeutic strategy for advanced prostate cancer as a monotherapy and in combination with second-generation antiandrogens.

Antiandrogen abiraterone and docetaxel treatments affect Notch1, Jagged1 and Hes1 expressions in metastatic prostate cancer cells

BACKGROUND

Prostate cancer is the most common cancer in men. A Notch signaling pathway is an important pathway in cell proliferation, differentiation, and fate. However, currently, the effects of abiraterone based-anti-androgene therapy and docetaxel, the most commonly used standard chemotherapy in prostate cancer treatment, on Notch signaling pathway are unknown. This study aimed to investigate the effects of abiraterone acetate and docetaxel on the expression of Notch1, Jagged1 and Hes1 in prostate cancer cell lines.

METHODS

In vitro effects of abiraterone acetate and docetaxel were examined on Notch1, Jagged1, and Hes1 expression in LNCaP and PC3 PCa cell lines by immunofluorescence, Western blot, and qRT-PCR. MTT proliferation assay was used to evaluate cell proliferation and survival.

RESULTS

We found that in the treatment of PC3 cells with abiraterone acetate, docetaxel, and their combination, only mRNA expressions of Notch1, Jagged1 and Hes1 were affected compared to control, but these expression differences were not observed in protein expression. In LNCaP cells, abiraterone acetate and the combination groups reduced Notch1 protein expression. All treatment groups did not alter Jagged1 expression compared to control, but significantly increased the Hes1 gene and protein expression.

CONCLUSION

Our findings suggest that abiraterone and docetaxel treatments affects the expression of Notch signal pathway proteins. But these drugs especially cause significant upregulation in Hes1 expression in PCa cells. Therefore, co-application of Notch signaling inhibitors together with docetaxel and abiraterone chemotherapy, it was thought that decreased Hes1 expression could be stopped the deterioration of the prognosis of the patient.

MicroRNA-122 regulates docetaxel resistance of prostate cancer cells by regulating

Prostate cancer (PCa), an epithelial malignancy that occurs in the prostate, is the second leading cause of cancer death worldwide. MicroRNAs (miRs/miRNAs) are reported to have important applications in the field of cancer diagnosis and treatment. The present study aimed to investigate the function of miRNA-122 in the chemoresistance of PCa cells and the underlying mechanism. Significantly decreased miR-122 and increased pyruvate kinase (PKM2) levels were observed in docetaxel-resistant PCa cells, and PKM2 was negatively correlated with miR-122. MiR-122 mimic transfection in docetaxel-resistant LNCaP cells significantly inhibited cell proliferation, promoted apoptosis and decreased glucose uptake and lactate production, which was counteracted by PKM2 overexpression. Inhibition of miR-122 in LNCaP cells had an opposite effect to miR-122 mimic transfection. In addition, miR-122 mimic transfection significantly increased the sensitivity of docetaxel-resistant LNCaP cells to docetaxel, while inhibition of miR-122 significantly decreased the sensitivity of LNCaP cells to docetaxel. Luciferase reporter assays showed that miR-122 regulated PKM2 expression by binding to the 3'-untranslated region of PKM2. The results suggest that upregulation of miR-122 could enhance docetaxel sensitivity, inhibit cell proliferation and promote apoptosis in PCa cells,possibly through the downregulation of its target protein PKM2.

miR-103a-3p Suppresses Cell Proliferation and Invasion by Targeting Tumor Protein D52 in Prostate Cancer

Growing evidence points at an association between microRNAs and tumor development. Although dysregulation of microRNA-103a-3p (miR-103a-3p) in multiple human cancers has been reported, its expression in prostate cancer (PCa) remains unknown and there is currently no research on the relationship between miR-103a-3p and tumor protein D52 (TPD52) in PCa. Our aim in this study was to explore the effect and potential mechanism of miR-103a-3p in PCa. qRT-PCR was performed to detected the level of miR-103a-3p in PCa tissues and cells, and in normal tissues. Colony, wound-healing, invasion, proliferation, and apoptosis assays were performed in search miR-103a-3p effect in PCa. TargetScan was used to predict potential targets of miR-103a-3p. Additionally, dual-luciferase reporter, western blot, and immunofluorescence assays were performed to detected the target gene of miR-103a-3p. Finally, we explore the differences in tumor xenograft experiments between nude mice injected with stably miR-103a-3p expressing cells and those expressing a miR-negative control. Low level of miR-103a-3p was detected in PCa tissues and cells, when compared with normal tissues. Enhancement of miR-103a-3p significantly inhibited migration and invasion of PCa cells, and negatively regulated expression of the oncogenic tumor protein D52 (TPD52) through direct binding to its 3'-UTR. Interestingly, overexpression of TPD52 significantly attenuated the effect of mir-103a-3p on PCa. Our study provides the first evidence that miR-103a-3p directly targets TPD52 and inhibits the proliferation and invasion of PCa. This finding helps clarify the role of mir-103a-3p-TPD52 axis in PCa and may provide new therapeutic targets for the disease.

RNA-binding protein Musashi2 stabilizing androgen receptor drives prostate cancer progression

The androgen receptor (AR) pathway is critical for prostate cancer carcinogenesis and development; however, after 18‐24 months of AR blocking therapy, patients invariably progress to castration‐resistant prostate cancer (CRPC), which remains an urgent problem to be solved. Therefore, finding key molecules that interact with AR as novel strategies to treat prostate cancer and even CRPC is desperately needed. In the current study, we focused on the regulation of RNA‐binding proteins (RBPs) associated with AR and determined that the mRNA and protein levels of AR were highly correlated with Musashi2 (MSI2) levels. MSI2 was upregulated in prostate cancer specimens and significantly correlated with advanced tumor grades. Downregulation of MSI2 in both androgen sensitive and insensitive prostate cancer cells inhibited tumor formation in vivo and decreased cell growth in vitro, which could be reversed by AR overexpression. Mechanistically, MSI2 directly bound to the 3′‐untranslated region (UTR) of AR mRNA to increase its stability and, thus, enhanced its transcriptional activity. Our findings illustrate a previously unknown regulatory mechanism in prostate cancer cell proliferation regulated by the MSI2‐AR axis and provide novel evidence towards a strategy against prostate cancer.

Comparison of the roles of estrogens and androgens in breast cancer and prostate cancer

Breast cancer (BC) and prostate cancer (PC) are the second most common malignant tumors in women and men in western countries, respectively. The risks of death are 14% for BC and 9% for PC. Abnormal estrogen and androgen levels are related to carcinogenesis of the breast and prostate. Estradiol stimulates cancer development in BC. The effect of estrogen on PC is concentration-dependent, and estrogen can regulate androgen production, further affecting PC. Estrogen can also increase the risk of androgen-induced PC. Androgen has dual effects on BC via different metabolic pathways, and the role of the androgen receptor (AR) in BC also depends on cell subtype and downstream target genes. Androgen and AR can stimulate both primary PC and castration-resistant PC. Understanding the mechanisms of the effects of estrogen and androgen on BC and PC may help us to improve curative BC and PC treatment strategies.

Exosomes Derived from miR-143-Overexpressing MSCs Inhibit Cell Migration and Invasion in Human Prostate Cancer by Downregulating TFF3

Exosomes are membrane-enclosed nanovesicles that shuttle active cargoes, such as mRNAs and microRNAs (miRNAs), between different cells. Mesenchymal stem cells (MSCs) are able to migrate to the tumor sites and exert complex functions over tumor progress. We investigated the effect of human bone marrow-derived MSC (BMSC)-derived exosomal miR-143 on prostate cancer. During the co-culture experiments, we disrupted exosome secretion by the inhibitor GW4869 and overexpressed exosomal miR-143 using miR-143 plasmid. miR-143 was involved in the progression of prostate cancer via trefoil factor 3 (TFF3). Moreover, miR-143 was downregulated while TFF3 was upregulated in prostate cancer cells and tissues, and miR-143 was found to specifically inhibit TFF3 expression. Human MSC-derived exosomes enriched miR-143 and transferred miR-143 to prostate cancer cells. Furthermore, elevated miR-143 or exosome-miR-143 or silencing TFF3 inhibited the expression of TFF3, proliferating cell nuclear antigen (PCNA), matrix metalloproteinase (MMP)-2, and MMP-9 and PC3 cell proliferation, migration, invasion, and tumor growth, whereas it promoted apoptosis. In conclusion, hMSC-derived exosomal miR-143 directly and negatively targets TFF3 to suppress prostate cancer.

Future Aspects of CDK5 in Prostate Cancer: From Pathogenesis to Therapeutic Implications

Cyclin-dependent kinase 5 (CDK5) is a unique member of the cyclin-dependent kinase family. CDK5 is activated by binding with its regulatory proteins, mainly p35, and its activation is essential in the development of the central nervous system (CNS) and neurodegeneration. Recently, it has been reported that CDK5 plays important roles in regulating various biological and pathological processes, including cancer progression. Concerning prostate cancer, the androgen receptor (AR) is majorly involved in tumorigenesis, while CDK5 can phosphorylate AR and promotes the proliferation of prostate cancer cells. Clinical evidence has also shown that the level of CDK5 is associated with the progression of prostate cancer. Interestingly, inhibition of CDK5 prevents prostate cancer cell growth, while drug-triggered CDK5 hyperactivation leads to apoptosis. The blocking of CDK5 activity by its small interfering RNAs (siRNA) or Roscovitine, a pan-CDK inhibitor, reduces the cellular AR protein level and triggers the death of prostate cancer cells. Thus, CDK5 plays a crucial role in the growth of prostate cancer cells, and AR regulation is one of the important pathways. In this review paper, we summarize the significant studies on CDK5-mediated regulation of prostate cancer cells. We propose that the CDK5–p35 complex might be an outstanding candidate as a diagnostic marker and potential target for prostate cancer treatment in the near future.

miR-221-5p regulates proliferation and migration in human prostate cancer cells and reduces tumor growth in vivo

Background

Despite latest advances in prostate cancer (PCa) therapy, PCa remains the third-leading cause of cancer-related death in European men. Dysregulation of microRNAs (miRNAs), small non-coding RNA molecules with gene expression regulatory function, has been reported in all types of epithelial and haematological cancers. In particular, miR-221-5p alterations have been reported in PCa.

Methods

miRNA expression data was retrieved from a comprehensive publicly available dataset of 218 PCa patients (GSE21036) and miR-221-5p expression levels were analysed. The functional role of miR-221-5p was characterised in androgen- dependent and androgen- independent PCa cell line models (C4–2 and PC-3M-Pro4 cells) by miR-221-5p overexpression and knock-down experiments. The metastatic potential of highly aggressive PC-3M-Pro4 cells overexpressing miR-221-5p was determined by studying extravasation in a zebrafish model. Finally, the effect of miR-221-5p overexpression on the growth of PC-3M-Pro4luc2 cells in vivo was studied by orthotopic implantation in male Balb/cByJ nude mice and assessment of tumor growth.

Results

Analysis of microRNA expression dataset for human primary and metastatic PCa samples and control normal adjacent benign prostate revealed miR-221-5p to be significantly downregulated in PCa compared to normal prostate tissue and in metastasis compared to primary PCa. Our in vitro data suggest that miR-221-5p overexpression reduced PCa cell proliferation and colony formation. Furthermore, miR-221-5p overexpression dramatically reduced migration of PCa cells, which was associated with differential expression of selected EMT markers. The functional changes of miR-221-5p overexpression were reversible by the loss of miR-221-5p levels, indicating that the tumor suppressive effects were specific to miR-221-5p. Additionally, miR-221-5p overexpression significantly reduced PC-3M-Pro4 cell extravasation and metastasis formation in a zebrafish model and decreased tumor burden in an orthotopic mouse model of PCa.

Conclusions

Together these data strongly support a tumor suppressive role of miR-221-5p in the context of PCa and its potential as therapeutic target.

Electronic supplementary material

The online version of this article (10.1186/s12885-019-5819-6) contains supplementary material, which is available to authorized users.

The LACOG-0415 phase II trial: abiraterone acetate and ADT versus apalutamide versus abiraterone acetate and apalutamide in patients with advanced prostate cancer with non-castration testosterone levels

BACKGROUND

Testosterone suppression is the standard treatment for advanced prostate cancer, and it is associated with side-effects that impair patients' quality of life, like sexual dysfunction, osteoporosis, weight gain, and increased cardiovascular risk. We hypothesized that abiraterone acetate with prednisone (AAP) and apalutamide, alone or in combination, can be an effective hormonal therapy also possibly decreasing castration-associated side effects.

METHODS

Phase II, open-label, randomized, efficacy trial of abiraterone acetate plus prednisone (AAP) and Androgen Deprivation Therapy (ADT) versus apalutamide versus the combination of AAP (without ADT) and apalutamide. Key eligibility criteria are confirmed prostate adenocarcinoma; biochemical relapse after definitive treatment (PSA ≥ 4 ng/ml and doubling time less than 10 months, or PSA ≥ 20 ng/ml); newly diagnosed locally advanced or metastatic prostate cancer; asymptomatic to moderately symptomatic regarding bone symptoms. Patients with other histology besides adenocarcinoma or previous use of hormonal therapy or chemotherapy were excluded.

DISCUSSION

There is an urgent need to study and validate regimens such as new hormonal agents that may add benefit to castration with an acceptable safety profile. We aim to evaluate if apalutamide in monotherapy or in combination with AAP is an effective and safety hormonal treatment that can spare patients of androgen deprivation therapy.

TRIAL REGISTRATION

This trial was registered in ClinicalTrials.gov on October 16, 2017, under Identifier: NCT02867020.

External validation and newly development of a nomogram to predict overall survival of abiraterone-treated, castration-resistant patients with metastatic prostate cancer

Abiraterone acetate is approved for the treatment of castration-resistant prostate cancer (CRPC); however, its effects vary. An accurate prediction model to identify patient groups that will benefit from abiraterone treatment is therefore urgently required. The Chi model exhibits a good profile for risk classification, although its utility for the chemotherapy-naive group is unclear. This study aimed to externally validate the Chi model and develop a new nomogram to predict overall survival (OS). We retrospectively analyzed a cohort of 110 patients. Patients were distributed among good-, intermediate-, and poor-risk groups, according to the Chi model. The good-, intermediate-, and poor-risk groups had a sample size of 59 (53.6%), 34 (30.9%), and 17 (15.5%) in our dataset, and a median OS of 48.4, 29.1, and 10.5 months, respectively. The C-index of external validation of Chi model was 0.726. Univariate and multivariate analyses identified low hemoglobin concentrations (<110 g l⁻¹), liver metastasis, and a short time interval from androgen deprivation therapy to abiraterone initiation (<36 months) as predictors of OS. Accordingly, a new nomogram was developed with a C-index equal to 0.757 (95% CI, 0.678–0.836). In conclusion, the Chi model predicted the prognosis of abiraterone-treated, chemotherapy-naive patients with mCRPC, and we developed a new nomogram to predict the overall survival of this group of patients with less parameters.

The importance of targeting intracrinology in prostate cancer management

Accumulating evidence has shown that intracrinology in prostate cancer (PCa) has a pivotal role in survival of cancer cell. PCa cells are able to produce androgens from different androgen precursors, such as dehydroepiandrosterone, thereby maintaining androgen receptor signaling. Several drugs have been developed that target intracrinology, some of which are now being used as standard treatment for the so-called castrate-resistant prostate cancer (CRPC) patients. Recently, the US FDA approval has changed the indication of drugs targeting intracrinology, e.g., abiraterone and enzalutamide where it evolved from post-chemotherapy CRPC to hormone-naive metastatic PCa cases. This approval raises question whether those drugs can also be used as the first-line treatment in localized stage PCa cases. In addition, development of additional drugs targeting major components of intracrinology is ongoing. Application of these new drugs and administration of combinations of existing drugs will ultimately lead to an increase in the efficacy of such treatments as well as to reduce the toxicity of the therapy and to prevent the risk of resistance.

Androgen receptor: what we know and what we expect in castration-resistant prostate cancer

Androgen deprivation therapy is an important therapy for prostate cancer (PCa) in aging men. Under the background of castration, it is inevitable that prostate cancer will develop into castration-resistant prostate cancer (CRPC), which has a high mortality rate, after 2-3 years. Androgen receptor (AR) plays a key role in PCa development and is essential to CRPC. More recent research studies have reported that the development of CRPC is largely due to altered mechanisms related to AR, so it is important for us to understand the roles of AR and detailed AR-related mechanisms in CRPC. The multiple AR-related mechanisms promoting the development of CRPC are as follows: (1) enhanced transformation and increased synthesis of intratumoral androgen; (2) AR overexpression, which enables CRPC to be hypersensitive to low levels of androgen; (3) AR cofactors, which enhanced AR transactivation; (4) AR-spliced variants, which mediated downstream gene expression without androgen; (5) the interaction between the AR pathway and classic tumor-related pathways; and» (6) AR mutations, which reduced AR specificity and enhanced AR transcription.

Troglitazone inhibits the migration and invasion of PC-3 human prostate cancer cells by upregulating E-cadherin and glutathione peroxidase 3

Troglitazone (TGZ) is a synthetic peroxisome proliferator-activated receptor γ (PPARγ) ligand that exhibits potential antitumor effects on a number of cancer subtypes, including prostate cancer. However, little is known about the effect of TGZ on metastasis in prostate cancer. The aim of the present study was to determine the inhibitory effect and mechanism underlying TGZ on cell growth, migration and invasion using the prostate cancer PC-3 cell line. Cellular migration and invasion were evaluated by performing a wound healing assay and Matrigel assay, respectively. The expression levels of mRNA and protein were determined by reverse transcription-quantitative polymerase chain reaction and western blotting. The results demonstrated that TGZ dose-dependently inhibited cell migration and invasion of PC-3 cells. The present study also revealed that TGZ increased the mRNA and protein levels of E-cadherin and glutathione peroxidase 3 (GPx3) in human prostate cancer PC-3 cells. In addition, GW9662, a PPARγ antagonist, attenuated the increased mRNA and protein levels of E-cadherin and GPx3, suggesting that the PPARγ-dependent signaling pathway was involved. Taken together, these results suggested that the anti-migration and anti-invasion effect of TGZ on PC-3 prostate cancer cells is, at least in part, mediated via upregulation of E-cadherin and GPx3. The present study also concluded that PPARγ may be used as a potential remedial target for the prevention and treatment of prostate cancer cell invasion and metastasis.

Androgen receptor mutations in patients with castration-resistant prostate cancer treated with apalutamide

Background

Mutations in the androgen receptor (AR) ligand-binding domain (LBD), such as F877L and T878A, have been associated with resistance to next-generation AR-directed therapies. ARN-509-001 was a phase I/II study that evaluated apalutamide activity in castration-resistant prostate cancer (CRPC). Here, we evaluated the type and frequency of 11 relevant AR-LBD mutations in apalutamide-treated CRPC patients.

Patients and methods

Blood samples from men with nonmetastatic CRPC (nmCRPC) and metastatic CRPC (mCRPC) pre- or post-abiraterone acetate and prednisone (AAP) treatment (≥6 months' exposure) were evaluated at baseline and disease progression in trial ARN-509-001. Mutations were detected in circulating tumor DNA using a digital polymerase chain reaction-based method known as BEAMing (beads, emulsification, amplification and magnetics) (Sysmex Inostics' GmbH).

Results

Of the 97 total patients, 51 had nmCRPC, 25 had AAP-naïve mCRPC, and 21 had post-AAP mCRPC. Ninety-three were assessable for the mutation analysis at baseline and 82 of the 93 at progression. The overall frequency of detected AR mutations at baseline was 7/93 (7.5%) and at progression was 6/82 (7.3%). Three of the 82 (3.7%) mCRPC patients (2 AAP-naïve and 1 post-AAP) acquired AR F877L during apalutamide treatment. At baseline, 3 of the 93 (3.2%) post-AAP patients had detectable AR T878A, which was lost after apalutamide treatment in 1 patient who continued apalutamide treatment for 12 months.

Conclusions

The overall frequency of detected mutations at baseline (7.5%) and progression (7.3%) using the sensitive BEAMing assay was low, suggesting that, based on this assay, AR-LBD mutations such as F877L and T878A are not common contributors to de novo or acquired resistance to apalutamide.

ClinicalTrials.gov identifier

NCT01171898.

Baseline prostate-specific antigen levels following treatment with abiraterone acetate as a prognostic factor in castration-resistant prostate cancer

The aim of the present study was to investigate the prognostic factors associated with progression-free survival (PFS) and overall survival (OS) times in patients with castration-resistant prostate cancer (CRPC) who received treatment with abiraterone acetate (AA) in routine clinical settings. A total of 93 patients treated with AA between September 2014 and February 2017 were selected and their medical records were analyzed retrospectively. The median PFS time of docetaxel (DTX)-naïve patients was 171 days, and that of post-DTX patients was 56 days. The OS time of DTX-naïve patients did not reach the median. The median OS time of post-DTX patients was 761 days. Multivariate analyses identified baseline prostate-specific antigen (PSA) level prior to treatment with AA and the PSA response rate as independent prognostic factors for PFS time, and baseline PSA prior to treatment with AA as the only independent prognostic factor for OS time. The results of the present study indicate that the baseline PSA level prior to treatment with AA is a notable prognostic factor in patients with CRPC.

TGF-β signal rewiring sustains epithelial-mesenchymal transition of circulating tumor cells in prostate cancer xenograft hosts

Activation of TGF-β signaling is known to promote epithelial-mesenchymal transition (EMT) for the development of metastatic castration-resistant prostate cancer (mCRPC). To determine whether targeting TGF-β signaling alone is sufficient to mitigate mCRPC, we used the CRISPR/Cas9 genome-editing approach to generate a dominant-negative mutation of the cognate receptor TGFBRII that attenuated TGF-β signaling in mCRPC cells. As a result, the delicate balance of oncogenic homeostasis is perturbed, profoundly uncoupling proliferative and metastatic potential of TGFBRII-edited tumor xenografts. This signaling disturbance triggered feedback rewiring by enhancing ERK signaling known to promote EMT-driven metastasis. Circulating tumor cells displaying upregulated EMT genes had elevated biophysical deformity and an increase in interactions with chaperone macrophages for facilitating metastatic extravasation. Treatment with an ERK inhibitor resulted in decreased aggressive features of CRPC cells in vitro. Therefore, combined targeting of TGF-β and its backup partner ERK represents an attractive strategy for treating mCRPC patients.

Natural history of castration-resistant prostate cancer in sub-Saharan African black men: a single-centre study of Nigerian men

Purpose

Native sub-Saharan African black men (SSBM) are disproportionately impacted by higher stage and incurable forms of prostate cancer (PCa). This study evaluates the natural history and survival of a cohort of SSBM with castration-resistant prostate cancer (CRPC).

Methods

A retrospective study of patients with CRPC as defined by the Prostate Cancer Working Group 2 managed at a centre in sub-Saharan Africa between January 2011 and December 2015 was conducted. The principal endpoint was overall survival (OS). Potential prognostic variables were evaluated using Cox proportional hazard regression models.

Results

A total of 48 patients were identified. Median (IQR) age and prostate-specific antigen (PSA) at diagnosis were 70 (64-74.5) years and 42 (8.0-123.6) ng/mL, respectively. Only 15 (31.3%) patients received docetaxel and one patient each received the novel drugs enzalutamide and abiraterone. Twenty-eight patients (58.3%) died during follow-up with a median OS of 11 (95% CI: 8-14) months. Docetaxel chemotherapy and ECOG performance status were found to be prognostic (docetaxel use: hazard ratio 0·25, 95% CI 0·10-0·67, p = 0·006; ECOG 0-2: 0·26, 0·11-0·62, p = 0·003).

Conclusion

This study of SSBM with CRPC revealed a mainly unmodulated clinical course with poor access to active treatments and poor survival. Improving access to new active therapies would improve survival.

Phenethyl isothiocyanate in combination with dibenzoylmethane inhibits the androgen-independent growth of prostate cancer cells

This study investigates the inhibitory effect of PEITC and DBM in combination on the progression of androgen-dependent VCaP prostate tumors to androgen independence.

Bone marrow mesenchymal stem cells participate in prostate carcinogenesis and promote growth of prostate cancer by cell fusion in vivo

The tumor microenvironment is comprised of diverse stromal cells that contribute towards tumor progression. As a result, there has been a growing interest in the role of bone marrow derived cells (BMDCs) in cancer progression. However, the role of BMDCs in prostate cancer (PCa) progression still remains unclear. In this study, we established GFP bone marrow transplanted TRAMP and MUN-induced prostate cancer models, in order to investigate the role of BMDCs in prostate cancer progression. By tracing GFP positive cells, we observed that BMDCS were recruited into mouse prostate tissues during tumorigenesis. GFP+/Sca-1+/CD45− BMDCs were significantly increased in the MNU-induced PCa group, as compared to the citrated-treated control group (2.67 ± 0.25% vs 0.67 ± 0.31%, p = 0.006). However, there were no significant differences found in GFP+/Sca-1+/CD45+ cell populations between the two groups (0.27 ± 0.15% vs 0.10 ± 0.10%, p = 0.334). Moreover, co-grafting of bone marrow mesenchymal stem cells (BMMSCs) and RM1 cells were found to promote RM1 tumor growth in vivo, and cell fusion was observed in RM-1+BMMSCs xenografts. Therefore, the data suggests that BMDCs can be recruited to the prostate during carcinogenesis, and that BMMSCs may promote the growth of PCa.

Treatment with abiraterone in metastatic castration-resistant prostate cancer patients progressing after docetaxel: a retrospective study

The aim of this study was to evaluate abiraterone's efficacy in Italian patients affected with metastatic prostate cancer progressing after treatment with docetaxel. We conducted a retrospective analysis of 60 patients. Prostate-specific antigen (PSA) reduction in serum was the primary endpoint for evaluating the efficacy of abiraterone in combination with prednisone treatment, whereas reduced pain, safety, progression-free survival, response rate, and overall survival (OS) were secondary endpoints. A significant correlation was noticed between PSA response and OS. Further, the Index Bravais-Pearson (r) correlation allowed us to observe a significant negative interdependence between PSA response and reduction in pain of 0.57 (95% confidence interval: -0.30 to 0.80) (P=0.005). Meanwhile, regression analysis revealed that PSA levels are predictive of OS. There was a positive correlation with OS, which showed a value of R to 0.50 with a slope of 1.44 (P=0.0021). Abiraterone is a well-tolerated and effective treatment modality for patients affected with metastatic castration-resistant prostate cancer. The drug has a better tolerability profile, gives significant pain relief, and increases the survival rate.

Impact of abiraterone on patient-related outcomes in metastatic castration-resistant prostate cancer: current perspectives

Abiraterone acetate has established a major role in the treatment paradigm of metastatic castration-resistant prostate cancer ever since pivotal trials, COU-AA-301 and COU-AA-302, have shown benefit in both the second-line and first-line (post- and pre-chemotherapy) setting, respectively, with improvement in overall survival as well as secondary end points such as prostate-specific antigen (PSA) and radiographic response rates, time to PSA progression, and progression-free survival. There has been a lot of interest and emphasis in the evaluation of patient-related outcomes (PROs) as it relates to quality of life, pain, adverse events, fatigue, and among others, in the use of different agents that have been shown to improve survival. This review examines the companion PROs in conjunction with abiraterone acetate use. This is particularly relevant since PROs are increasingly viewed as a key metric for drug label claims in granting approval across regulatory agencies, including the US Food and Drug Administration and the European Medicines Agency.

Abiraterone Acetate for Treatment of Metastatic Castration-resistant Prostate Cancer in Chemotherapy-naive Patients: An Italian Analysis of Patients' Satisfaction

INTRODUCTION

Abiraterone acetate (AA) gives a significant improvement in survival for patients with metastatic castration-resistant prostate cancer (mCRPC) before and after chemotherapy and has a favorable effect on patients' health-related quality of life and pain. Only a few studies have investigated patient-reported outcomes (PROs) in AA treatment for mCRPC. The aim of this study was to investigate patients' satisfaction in men affected by mCRPC treated with AA.

MATERIALS AND METHODS

This was a retrospective analysis of a database of consecutive chemonaive patients with progressive mCRPC. Patients were treated with AA until disease progression, death, or unacceptable toxicity. Evaluation was performed at baseline and every 4 weeks by means of physical examination and laboratory studies. Eastern Cooperative Oncology Group score, pain symptoms, treatment-related toxicity, prostate-specific antigen (PSA), and overall and progression-free survival were recorded. Satisfaction with treatment was investigated at 6 months by means of a 4-point arbitrary scale.

RESULTS

One-hundred twenty-eight patients were enrolled. Patients' satisfaction with treatment was "greatly improved" in 36.1% of patients and "improved" in 32.4% of them. Patients with higher satisfaction had lower baseline and final PSA values (P < .05), lower PSA levels at 12 weeks (P = .080), and less pain symptoms and lower Brief Pain Inventory scores (P = .001). Satisfaction with treatment was significantly correlated with baseline PSA level (P = .018), presence of pain (P = .007), duration of androgen deprivation therapy >12 months (P = .025), and number of hormonal manipulations (P = .051). Progression-free survival significantly correlated with patient satisfaction (P < .001).

CONCLUSION

AA is safe and well tolerated in chemonaive mCRPC patients, ensures good oncological and PROs. Patient's satisfaction is a predictor of progression-free survival.

Phase 2 Study of the Safety and Antitumor Activity of Apalutamide (ARN-509), a Potent Androgen Receptor Antagonist, in the High-risk Nonmetastatic Castration-resistant Prostate Cancer Cohort

BACKGROUND

Apalutamide is a potent androgen receptor (AR) antagonist that targets the AR ligand-binding domain and prevents AR nuclear translocation, DNA binding, and transcription of AR gene targets.

OBJECTIVE

To evaluate the activity and safety of apalutamide in patients with high-risk nonmetastatic castration-resistant prostate cancer (nmCRPC).

DESIGN, SETTING, AND PARTICIPANTS

We conducted a multicenter phase 2 study of nmCRPC patients with a high risk for progression (prostate-specific antigen [PSA] ≥8 ng/ml or PSA doubling time [PSA DT] ≤10 mo).

INTERVENTION

Patients received 240mg/d apalutamide while continuing on androgen-deprivation therapy.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

Primary end point was 12-wk PSA response (Prostate Cancer Working Group 2 criteria). Secondary end points included safety, time to PSA progression (TTPP), and metastasis-free survival (MFS).

RESULTS AND LIMITATIONS

A total of 51 patients were enrolled; four patients with metastatic disease were excluded from the efficacy analysis. Patient characteristics included median age, 71 yr; Eastern Cooperative Oncology Group performance status 0 (76%); Gleason score ≤7 (57%); median PSA 10.7 ng/ml; and PSA DT ≤10 mo (45%). At median follow-up of 28.0 mo, 18 patients (35%) remained in the study. Overall, 89% of patients had ≥50% PSA decline at 12 wk. Median TTPP was 24.0 mo (95% confidence interval [CI], 16.3 mo-not reached [NR]); median MFS was NR (95% CI, 33.4 mo-NR). Most of the patients discontinued study treatment (n=33) due to disease progression (n=11 [22%]) or adverse events (AEs) (n=9 [18%]). The most common AE was fatigue (any grade, n=31 [61%]) although grade ≥3 fatigue was uncommon (n=2 [4%]). These represent the first apalutamide nmCRPC patient clinical data.

CONCLUSIONS

In high-risk nmCRPC patients, apalutamide was safe with robust activity based on durable PSA responses and disease control.

PATIENT SUMMARY

Antitumor activity and the safety of apalutamide in patients with nonmetastatic castration-resistant prostate cancer support continued development in this setting.

TRIAL REGISTRATION

ClinicalTrials.gov identifier NCT01171898.

Insulin Receptor Isoform Variations in Prostate Cancer Cells

Men who develop prostate cancer (PCa) increasingly have one of the co-morbidities associated with a Western lifestyle that are characterized by hyperinsulinemia, hyperglycemia and increased expression of insulin-like growth factors-I (IGF-I) and IGF-II. Each have been associated with poor prognosis and more aggressive cancers that exhibit increased metabolism and increased glucose uptake. The insulin receptor (IR) has two splice isoforms IR-A and IR-B: IR-A has a higher affinity for IGF-II comparable to that for insulin, whereas the IR-B isoform predominantly just binds to insulin. In this study, we assessed alterations in the IR-A and IR-B isoform ratio and associated changes in cell proliferation and migration of PCa cell lines following exposure to altered concentrations of glucose and treatment with IGF-II and insulin. We observed that where IR-B predominated insulin had a greater effect on migration than IGF-II and IGF-II was more effective when IR-A was the main isoform. With regard to proliferation IGF-II was more effective than insulin regardless of which isoform was dominant. We assessed the abundance of the IR isoforms both in vivo and in vitro and observed that the majority of the tissue samples and cell lines expressed more IR-A than IR-B. Alterations in the isoforms in response to changes in their hormonal milieu could have a profound impact on how malignant cells behave and play a role in promoting carcinogenesis. A greater understanding of the mechanisms underlying changes in alternative splicing of the IR may provide additional targets for future cancer therapies.

Regulation of metastasis-promoting LOXL2 gene expression by antitumor microRNAs in prostate cancer

Our recent studies of microRNA (miRNA) expression signatures of prostate cancer (PCa) showed that six miRNAs (specifically, miR-26a, miR-26b, miR-29a, miR-29b, miR-29c and miR-218) were markedly reduced in cancer tissues. Moreover, ectopic expression of these miRNAs suppressed PCa cell aggressiveness, indicating that these miRNAs acted in concert to regulate genes that promoted metastasis. Genome-wide gene expression analysis and in silico database analysis identified a total of 35 candidate genes that promoted metastasis and were targeted by these 6 miRNAs. Using luciferase reporter assays, we showed that the lysyl oxidase-like 2 (LOXL2) gene was directly controlled by these tumor-suppressive miRNAs in PCa cells. Overexpression of LOXL2 was confirmed in PCa tissues and knockdown of the LOXL2 gene markedly inhibited the migration and invasion of PCa cells. Aberrant expression of LOXL2 enhanced migration and invasion of PCa cells. Downregulation of antitumor miRNAs might disrupt the tightly controlled RNA networks found in normal cells. New insights into the novel molecular mechanisms of PCa pathogenesis was revealed by antitumor miRNA-regulated RNA networks.

Inhibition of hedgehog signaling improves the anti-carcinogenic effects of docetaxel in prostate cancer

The establishment of docetaxel-based chemotherapeutic treatments has improved the survival of castration-resistant prostate cancer (CRPC) patients. However, most patients develop resistance supporting the development of therapy. The current study was undertaken to establish the therapeutic benefit to target hedgehog signaling cascade using GDC-0449 to improve the efficacy of chemotherapeutic drug, docetaxel. Here, we show that the combination of GDC-0449 plus docetaxel inhibited the proliferation of WPE1-NB26 cells and PC3 cells via a blockade of G1 and G2M phases. The combined treatment significantly inhibited PC cell migration in vitro. Moreover, the apoptotic effect induced by GDC-0449 plus docetaxel on PC3 cells was mediated, at least partly, via the mitochondrial membrane depolarization, H₂O₂ production and caspase cascade activation. Interestingly, GDC-0449 was effective at inhibiting the prostasphere formation, inducing the prostasphere disintegration and apoptotic death of side population (SP) from PC3 cells and reversing the resistance of SP cells to docetaxel. In addition, GDC-0449 plus docetaxel also have shown a greater anti-tumoral growth inhibitory effect on PC3 cell xenografts. These findings support the use of the hedgehog inhibitor GDC-0449, which is currently in clinical trials, for improving the anticarcinogenic efficacy of docetaxel-based chemotherapeutic treatments against locally advanced, AI and metastatic PC.

A prognostic index model for predicting overall survival in patients with metastatic castration-resistant prostate cancer treated with abiraterone acetate after docetaxel

A prognostic index model was developed, composed of six readily available and assessable factors and categorizing patients with metastatic castration-resistant prostate cancer treated with abiraterone–prednisone into distinct prognostic risk groups. This model could be useful for determining patient prognosis for follow-up, monitoring and patient stratification for clinical trials.

Background

Few prognostic models for overall survival (OS) are available for patients with metastatic castration-resistant prostate cancer (mCRPC) treated with recently approved agents. We developed a prognostic index model using readily available clinical and laboratory factors from a phase III trial of abiraterone acetate (hereafter abiraterone) in combination with prednisone in post-docetaxel mCRPC.

Patients and methods

Baseline data were available from 762 patients treated with abiraterone–prednisone. Factors were assessed for association with OS through a univariate Cox model and used in a multivariate Cox model with a stepwise procedure to identify those of significance. Data were validated using an independent, external, population-based cohort.

Results

Six risk factors individually associated with poor prognosis were included in the final model: lactate dehydrogenase > upper limit of normal (ULN) [hazard ratio (HR) = 2.31], Eastern Cooperative Oncology Group performance status of 2 (HR = 2.19), presence of liver metastases (HR = 2.00), albumin ≤4 g/dl (HR = 1.54), alkaline phosphatase > ULN (HR = 1.38) and time from start of initial androgen-deprivation therapy to start of treatment ≤36 months (HR = 1.30). Patients were categorized into good (n = 369, 46%), intermediate (n = 321, 40%) and poor (n = 107, 13%) prognosis groups based on the number of risk factors and relative HRs. The C-index was 0.70 ± 0.014. The model was validated by the external dataset (n = 286).

Conclusion

This analysis identified six factors used to model survival in mCRPC and categorized patients into three distinct risk groups. Prognostic stratification with this model could assist clinical practice decisions for follow-up and monitoring, and may aid in clinical trial design.

Trial registration numbers

NCT00638690.

Expression of store-operated channel components in prostate cancer: the prognostic paradox

In vitro studies in prostate cancer (PCa) cell lines have suggested a key and complex role of the store-operated channels (SOCs) in major cancer hallmarks, including proliferation, apoptosis, and migration. In the present study, we investigated in vivo the expression of the SOC components transient receptor potential canonical (TRPC) 1, TRPC4, Orai1, and stromal interaction molecule 1 (STIM1), during all stages of PCa progression, and evaluated their prognostic impact in clinically localized cancer (CLC). The expressions of TRPC1, TRPC4, Orai1, STIM1, and the androgen receptor and the proliferation marker Ki-67 were evaluated by immunohistochemistry on tissue microarrays containing samples of normal prostate tissues (n=91), prostatic intraepithelial neoplasia (n=61), CLC surgically treated (n=238), and castration-resistant prostate cancer (CRPC; n=45). All markers significantly increased in CLC compared with normal tissues and (for Orai1 and STIM1) in advanced pT3 tumors compared with pT2. In contrast, their expression decreased in CRPC, particularly for Orai1. In CLC, staining for TRPC1, Orai1 and STIM1 correlated with androgen receptor expression, and TRPC1 status was associated with lower proliferation and longer recurrence-free survival, after adjusting for classical prognostic markers. Although increased SOC expression during PCa progression supports a role in cancer cell migration, the inverse association between TRPC1 and biochemical relapse suggests a protective effect in CLC. Moreover, the dramatic down-regulation of Orai1 in CRPC supports its role in apoptosis at this stage of the disease. These results call for caution when considering SOCs as potential therapeutic targets for PCa.

MicroRNA expression signature of castration-resistant prostate cancer: the microRNA-221/222 cluster functions as a tumour suppressor and disease progression marker

Background:

Our present study of the microRNA (miRNA) expression signature in castration-resistant prostate cancer (CRPC) revealed that the clustered miRNAs microRNA-221 (miR-221) and microRNA-222 (miR-222) are significantly downregulated in cancer tissues. The aim of this study was to investigate the functional roles of miR-221 and miR-222 in prostate cancer (PCa) cells.

Methods:

A CRPC miRNA signature was constructed by PCR-based array methods. Functional studies of differentially expressed miRNAs were analysed using PCa cells. The association between miRNA expression and overall survival was estimated by the Kaplan–Meier method. In silico database and genome-wide gene expression analyses were performed to identify molecular targets regulated by the miR-221/222 cluster.

Results:

miR-221 and miR-222 were significantly downregulated in PCa and CRPC specimens. Kaplan–Meier survival curves showed that low expression of miR-222 predicted a short duration of progression to CRPC. Restoration of miR-221 or miR-222 in cancer cells revealed that both miRNAs significantly inhibited cancer cell migration and invasion. Ecm29 was directly regulated by the miR-221/222 cluster in PCa cells.

Conclusions:

Loss of the tumour-suppressive miR-221/222 cluster enhanced migration and invasion in PCa cells. Our data describing targets regulated by the tumour-suppressive miR-221/222 cluster provide insights into the mechanisms of PCa and CRPC progression.

Comparative analysis of the effectiveness of abiraterone before and after docetaxel in patients with metastatic castration-resistant prostate cancer

AIM: To study the efficacy and safety of abiraterone in patients with and without prior chemotherapy.

METHODS: The databases including PubMed and abstracts presented at the American Society of Clinical Oncology meetings up to April 2014 were systematically searched. Eligible studies included randomized controlled trials (RCTs) in which abiraterone plus prednisone was compared to placebo plus prednisone in metastatic castration-resistant prostate cancer (CRPC) patients. The summary incidence, relative risk, hazard ratio and 95%CI were calculated using random or fixed-effects models. Heterogeneity test was performed to test between-study differences in efficacy and toxicity.

RESULTS: A total of two phase III RCTs were included in our analysis, with metastatic CPRC patients before (n = 1088) and after chemotherapy (n = 1195). Prior chemotherapy did not significantly alter the effect of abiraterone on overall survival (P = 0.92) and prostate-specific antigen (PSA) progression-free survival (P = 0.13), but reduced its effect on radiographic-progression-free survival (P = 0.04), objective response rate (P < 0.001), and PSA response rate (P < 0.001). Prior chemotherapy significantly increased the specific risk of fluid retention and edema (P < 0.001) and hypokalemia (P < 0.001), but decreased the risk of all-grade hypertension (P < 0.001) attributable to abiraterone. There was no significant difference of cardiac disorders associated with abiraterone between the two settings (P = 0.58).

CONCLUSION: Prior chemotherapy may reduce the effectiveness of abiraterone in patients with metastatic CRPC.

The microRNA-23b/27b/24-1 cluster is a disease progression marker and tumor suppressor in prostate cancer

Our recent study of microRNA (miRNA) expression signatures in prostate cancer (PCa) has revealed that all members of the miR-23b/27b/24-1 cluster are significantly downregulated in PCa tissues. The aim of this study was to investigate the effectiveness of these clustered miRNAs as a disease progression marker and to determine the functional significance of these clustered miRNAs in PCa. Expression of the miR-23b/27b/24-1 cluster was significantly reduced in PCa tissues. Kaplan-Meier survival curves showed that low expression of miR-27b predicted a short duration of progression to castration-resistant PCa. Gain-of-function studies using mature miR-23b, miR-27b, and miR-24-1 significantly inhibited cell proliferation, migration and invasion in PCa cells (PC3 and DU145). To identify the molecular targets of these miRNAs, we carried out gene expression and in silico database analyses. GOLM1 was directly regulated by miR-27b in PCa cells. Elucidation of the molecular targets and pathways regulated by the tumor-suppressive microRNAs should shed light on the oncogenic and metastatic processes in PCa.

MicroRNA-26a/b directly regulate La-related protein 1 and inhibit cancer cell invasion in prostate cancer

Our past studies of microRNA (miRNA) expression signatures of cancers including prostate cancer (PCa) revealed that microRNA-26a and microRNA-26b (miR-26a and miR-26b) were significantly downregulated in cancer tissues. In the present study, we found that restoration of miR-26a or miR-26b significantly inhibited PCa cell invasion. Gene expression data and in silico analysis showed that the gene encoding La-related protein 1 (LARP1) was a putative candidate of miR-26a and miR-26b regulation. Moreover, luciferase reporter assays revealed that LARP1 was a direct target of both miR-26a and miR-26b. Overexpression of LARP1 was observed in PCa clinical specimens and knockdown of LARP1 inhibited cancer cell migration. Therefore, LARP1 acted as an oncogene in PCa cells. Moreover, 'ribosome', 'RNA transport' and 'mTOR signaling pathway' were identified as LARP1-regulated pathways. Our present data suggested that loss of tumor-suppressive miR-26a and miR-26b enhanced cancer cell invasion in PCa through direct regulation of oncogenic LARP1. Elucidation of the molecular networks regulated by tumor-suppressive miRNAs will provide insights into the molecular mechanisms of PCa oncogenesis and metastasis.

Anticancer activity of Acanthopanax trifoliatus (L) Merr extracts is associated with inhibition of NF-kB activity and decreased Erk1/2 and Akt phosphorylation

Acanthopanax trifoliatus (L) Merr (AT) is commonly used as an herbal medicine and edible plant in some areas of China and other Asian countries. AT is thought to have anticancer effects, but potential mechanisms remain unknown. To assess the anticancer properties of AT, we exposed prostate cancer cells to AT extracts and assessed cell proliferation and signaling pathways. An ethanol extract of AT was suspended in water followed by sequential extraction with petroleum ether, ethyl acetate and n-butanol. PC-3 cells were treated with different concentrations of each extract and cell viability was determined by the MTT and trypan blue exclusion assays. The ethyl acetate extract of the ethanol extract had a stronger inhibitory effect on growth and a stronger stimulatory effect on apoptosis than any of the other extracts. Mechanistic studies demonstrated that the ethyl acetate extract suppressed the transcriptional activity of NF-kB, increased the level of caspase-3, and decreased the levels of phospho-Erk1/2 and phospho-Akt. This is the first report on the anticancer activity of AT in cultured human prostate cancer cells. The results suggest that AT can provide a plant-based medicine for the treatment or prevention of prostate cancer.

Serum follicle-stimulating hormone levels predict time to development of castration-resistant prostate cancer

INTRODUCTION

Treatment of advancing prostate cancer focuses on blocking the activation of the androgen receptor with resultant prolonged perturbation of the hypothalamic-pituitary-gonadal axis. Androgen deprivation therapy (ADT) is marked, however, by eventual progression to castration- resistant prostate cancer (CRPC). Emerging evidence has postulated that follicle-stimulating hormone (FSH) may lead to proliferative and mutagenic responses of prostate cancer. We investigated the association of serum FSH and time to castration resistance.

METHODS

This was a single-centre retrospective study assessing serum FSH levels of patients undergoing ADT for advancing prostate cancer. The primary outcome was time of ADT initiation to the development of CRPC. For each patient on treatment and with castrate levels of testosterone, the maximum FSH value between ADT commencement and CRPC was identified and recorded. FSH was analyzed as a continuous and categorical variable. Cox multivariate regression in a step-wise fashion was used to explore the association between FSH levels and time to CRPC.

RESULTS

From a database of 323 prostate cancer patients actively managed with ADT, 103 men had a documented FSH value while castrate, with 45 men progressing to CRPC. The mean ± standard deviation maximum FSH value of these patients was 6.66 ± 4.22 mIU/mL (range: 1.5-28.1). The mean duration from ADT commencement to CRPC was 3.03 ± 0.34 years (range: 0.36-9.71). Univariate analysis suggested a trend of a negative correlation between FSH values and time to castrate resistance. A FSH value of less than or equal to the lowest tertile (4.8 mIU/mL) was associated with a longer time to CRPC (hazard ratio 0.46; p = 0.006). In the Cox regression analysis, elevated FSH was associated with a shorter duration time to CRPC (p = 0.03).

CONCLUSIONS

This retrospective, single-centre study would suggest there may be an association between serum FSH levels and time to CRPC for men treated palliatively with ADT for advancing prostate cancer. Further clinical investigation in a larger cohort of men is required to determine any clinical utility of FSH as a biomarker of progression or target for therapy.

MicroRNA-205 inhibits cancer cell migration and invasion via modulation of centromere protein F regulating pathways in prostate cancer

OBJECTIVES

To investigate the functional roles of microRNA-205 in the modulation of novel cancer pathways in prostate cancer cells.

METHODS

Functional studies of microRNA-205 were carried out to investigate cell proliferation, migration and invasion in prostate cancer cell lines (PC3 and DU145) by restoration of mature microRNA. In silico database and genome-wide gene expression analyses were carried out to identify molecular targets and pathways mediated by microRNA-205. Loss-of-function studies were applied to microRNA-205 target genes.

RESULTS

Restoration of microRNA-205 in cancer cell lines significantly inhibited cancer cell migration and invasion. Our data showed that the centromere protein F gene was overexpressed in prostate cancer clinical specimens and was a direct target of microRNA-205 regulation. Silencing of centromere protein F significantly inhibited cancer cell migration and invasion. Furthermore, MCM7, an oncogenic gene functioning downstream of centromere protein F, was identified by si-centromere protein F transfectants in prostate cancer cells.

CONCLUSIONS

Loss of tumor-suppressive microRNA-205 seems to enhance cancer cell migration and invasion in prostate cancer through direct regulation of centromere protein F. Our data describing pathways regulated by tumor-suppressive microRNA-205 provide new insights into the potential mechanisms of prostate cancer oncogenesis and metastasis.

Radium-223 dichloride for metastatic castration-resistant prostate cancer: the urologist's perspective

Radium-223 dichloride (radium-223) is an important therapeutic option for the treatment of patients with castration-resistant prostate cancer, symptomatic bone metastases, and no visceral disease. The unique mechanism of action of this first-in-class alpha-emitting radiopharmaceutical underlies its favorable safety profile and low incidence of myelosuppression. In the pivotal phase 3 ALpharadin in SYMptomatic Prostate CAncer Patients study, radium-223 reduced the risk of death by 30% and prolonged time to first symptomatic skeletal event by 5.8 months. This article summarizes current guidelines and clinical studies that led to the approval of radium-223 as an overall survival therapy, and discusses the urologist's perspective on using radium-223 in clinical practice.