The role of epithelial plasticity in prostate cancer dissemination and treatment resistance

An Overview of Epithelial-to-Mesenchymal Transition and Mesenchymal-to-Epithelial Transition in Canine Tumors: How Far Have We Come?

Historically, pre-clinical and clinical studies in human medicine have provided new insights, pushing forward the contemporary knowledge. The new results represented a motivation for investigators in specific fields of veterinary medicine, who addressed the same research topics from different perspectives in studies based on experimental and spontaneous animal disease models. The study of different pheno-genotypic contexts contributes to the confirmation of translational models of pathologic mechanisms. This review provides an overview of EMT and MET processes in both human and canine species. While human medicine rapidly advances, having a large amount of information available, veterinary medicine is not at the same level. This situation should provide motivation for the veterinary medicine research field, to apply the knowledge on humans to research in pets. By merging the knowledge of these two disciplines, better and faster results can be achieved, thus improving human and canine health.

The Antileukemic and Anti-Prostatic Effect of Aeroplysinin-1 Is Mediated through ROS-Induced Apoptosis via NOX Activation and Inhibition of HIF-1a Activity

Aeroplysinin-1 is a brominated isoxazoline alkaloid that has exhibited a potent antitumor cell effect in previous reports. We evaluated the cytotoxicity of aeroplysinin-1 against leukemia and prostate cancer cells in vitro. This marine alkaloid inhibited the cell proliferation of leukemia Molt-4, K562 cells, and prostate cancer cells Du145 and PC-3 with IC₅₀ values of 0.12 ± 0.002, 0.54 ± 0.085, 0.58 ± 0.109 and 0.33 ± 0.042 µM, respectively, as shown by the MTT assay. Furthermore, in the non-malignant cells, CCD966SK and NR8383, its IC₅₀ values were 1.54 ± 0.138 and 6.77 ± 0.190 μM, respectively. In a cell-free system, the thermal shift assay and Western blot assay verified the binding affinity of aeroplysinin-1 to Hsp90 and Topo IIα, which inhibited their activity. Flow cytometry analysis showed that the cytotoxic effect of aeroplysinin-1 is mediated through mitochondria-dependent apoptosis induced by reactive oxygen species (ROS). ROS interrupted the cellular oxidative balance by activating NOX and inhibiting HIF-1α and HO-1 expression. Pretreatment with N-acetylcysteine (NAC) reduced Apl-1-induced mitochondria-dependent apoptosis and preserved the expression of NOX, HO-1, and HIF-1a. Our findings indicated that aeroplysinin-1 targeted leukemia and prostate cancer cells through multiple pathways, suggesting its potential application as an anti-leukemia and prostate cancer drug lead.

Genetic variants in epithelial-mesenchymal transition genes as predictors of clinical outcomes in localized prostate cancer

BACKGROUND

Epithelial-mesenchymal transition (EMT) plays a pivotal role in the progression of prostate cancer (PCa). However, little is known about genetic variants in the EMT pathway as predictors of aggressiveness, biochemical recurrence (BCR) and disease reclassification in localized PCa.

PATIENTS AND METHODS

In this multistage study, we evaluated 5186 single nucleotide polymorphisms (SNPs) from 264 genes related to EMT pathway to identify SNPs associated with PCa aggressiveness and BCR in the MD Anderson PCa (MDA-PCa) patient cohort (N = 1762), followed by assessment of the identified SNPs with disease reclassification in the active surveillance (AS) cohort (N = 392).

RESULTS

In the MDA-PCa cohort, 312 SNPs were associated with high D'Amico risk (P < 0.05), among which, 14 SNPs in 10 genes were linked to BCR risk. In the AS cohort, 2 of 14 identified SNPs (rs76779889 and rs7083961) in C-terminal Binding Proteins 2 gene were associated with reclassification risk. The associations of rs76779889 with different endpoints were: D'Amico high versus low, odds ratio [95% confidence interval (CI)] = 2.89 (1.32-6.34), P = 0.008; BCR, hazard ratio (HR) (95% CI) = 2.88 (1.42-5.85), P = 0.003; and reclassification, HR (95% CI) = 2.83 (1.40-5.74), P = 0.004. For rs7083961, the corresponding risk estimates were: D'Amico high versus low, odds ratio (95% CI) = 1.69 (1.12-2.57), P = 0.013; BCR, HR (95% CI) = 1.87 (1.15-3.02), P = 0.011 and reclassification, HR (95% CI) = 1.72 (1.09-2.72), P = 0.020. There were cumulative effects of these two SNPs on modulating these endpoints.

CONCLUSION

Genetic variants in EMT pathway may influence the risks of localized PCa's aggressiveness, BCR and disease reclassification, suggesting their potential role in the assessment and management of localized PCa.

Down-Regulation of DDR1 Induces Apoptosis and Inhibits EMT through Phosphorylation of Pyk2/MKK7 in DU-145 and Lncap-FGC Prostate Cancer Cell Lines

BACKGROUND

In cancer cells, re-activation of Epithelial-Mesenchymal Transition (EMT) program through Discoidin Domain Receptor1 (DDR1) leads to metastasis. DDR1-targeted therapy with siRNA might be a promising strategy for EMT inhibition. Therefore, the aim of this study was to investigate the effect of DDR1 knockdown in the EMT, migration, and apoptosis of prostate cancer cells. For this purpose, the expression of DDR1 was down regulated by the siRNA approach in LNcap-FGC and DU-145 prostate cancer cells.

METHODS

Immunocytochemistry was carried out for the assessment of EMT. E-cadherin, N-cadherin, Bax, Bcl2, and the phosphorylation level of Proline-rich tyrosine kinase 2 (Pyk2) and Map Kinase Kinase 7 (MKK7) was determined using the western blot. Wound healing assay was used to evaluate cell migration. Flow cytometry was employed to determine the apoptosis rate in siRNA-transfected cancer cells.

RESULTS

Our findings showed that the stimulation of DDR1 with collagen-I caused increased phosphorylation of Pyk2 and MKK7 signaling molecules that led to the induction of EMT and migration in DU-145 and LNcap- FGC cells. In contrast, DDR1 knockdown led to significant attenuation of EMT, migration, and phosphorylation levels of Pyk2 and MKK7. Moreover, DDR1 knockdown via induction of Bax expression and suppression of Bcl-2 expression induces apoptosis.

CONCLUSION

Collectively, our results indicate that the DDR1 targeting with siRNA may be beneficial for the inhibition of EMT and the induction of apoptosis in prostate cancer.

The role of microRNA-572 in the proliferation and chemotherapeutic treatment of prostate cancer

OBJECTIVE

MicroRNAs (miRNAs) regulate prostate tumorigenesis and progression by involving different molecular pathways. In this study, we examined the role of miR-572 in prostate cancer (PCa).

METHODS

The proliferation rates of LNCaP and PC-3 PCa cells were studied using MTT assays. Transwell migration and Matrigel invasion assays were performed to evaluate cell migration and invasion, respectively. Protein expression levels were examined using western blotting. Docetaxel-induced apoptosis was evaluated by Caspase-Glo3/7 assays. The putative miR-572 binding site in the phosphatase and tensin homolog (PTEN) 3' untranslated region (3' UTR) was assessed with dual-luciferase reporter assays. Additionally, miR-572 expression levels in human PCa tissues were examined by qRT-PCR assays.

RESULTS

Upregulation of miR-572 promoted proliferation, migration, and invasion of PCa cells. Overexpression of miR-572 decreased sensitivity of PCa cells to docetaxel treatment by reducing docetaxel-induced apoptosis. MiR-572 can regulate migration and invasion in PCa cells. Furthermore, miR-572 could regulate expression of PTEN and p-AKT in PCa cells by directly binding to the PTEN 3' UTR. MiR-572 expression levels were increased in human PCa tissues and associated with PCa stage.

CONCLUSIONS

miR-572 displayed essential roles in PCa tumor growth and its expression level may be used to predict docetaxel treatment in these tumors.

The role of S100A4 for bone metastasis in prostate cancer cells

BACKGROUND

Prostate cancers frequently metastasize to bone, where the best microenvironment for distant colonization is provided. Since osteotropic metastasis of prostate cancer is a critical determinant of patients' survival, searches for preventive measures are ongoing in the field. Therefore, it is important to dissect the mechanisms of each step of bone metastasis, including the epithelial-mesenchymal transition (EMT) and cross-talk between metastatic niches and cancer cells.

METHODS

In this study, we established a highly bone-metastatic subline of human prostate cancer cells by selecting bone-homing population of PC3 cells after cardiac injection of eight-week-old male BALB/c-nude mice. Then we assessed the proliferation, EMT characteristics, and migration properties of the subline (mtPC3) cells in comparison with the parental PC3 cells. To investigate the role of S100A4, we performed gene knock-down by lentiviral transduction, or treated cells with recombinant S100A4 protein or a S100A4-neutralizing antibody. The effect of cancer cells on osteoclastogenesis was evaluated after treatment of pre-osteoclasts with conditioned medium (CM) from cancer cells.

RESULTS

The mtPC3 cells secreted a markedly high level of S100A4 protein and showed elevated cell proliferation and mesenchymal properties. The increased proliferation and EMT traits of mtPC3 cells was inhibited by S100A4 knock-down, but was not affected by exogenous S100A4. Furthermore, S100A4 released from mtPC3 cells stimulated osteoclast development via the cell surface receptor RAGE. Down-regulation or neutralization of S100A4 in the CM of mtPC3 cells attenuated cancer-induced osteoclastogenesis.

CONCLUSION

Altogether, our results suggest that intracellular S100A4 promotes cell proliferation and EMT characteristics in tumor cells, and that secreted S100A4 activates osteoclastogenesis, contributing to osteolytic bone metastasis. Thus, S100A4 upregulation in cancer cells highly metastatic to bone might be a key element in regulating bone metastasis.

Regulation of carcinogenesis and mediation through Wnt/β-catenin signaling by 3,3'-diindolylmethane in an enzalutamide-resistant prostate cancer cell line

Enzalutamide (ENZ) is an important drug used to treat castration-resistant prostate cancer (CRPC), which inhibits androgen receptor (AR) signaling. Previous study showed that 3,3′-diindolylmethane (DIM) is an AR antagonist that also inhibits Wnt signaling and epithelial-mesenchymal transition (EMT). To investigate whether combined treatment with ENZ and DIM can overcome ENZ resistance by regulating Wnt signaling to inhibit AR signaling and EMT in ENZ-resistant prostate cancer cells, 22Rv1 cells were cultured in normal medium and treated with ENZ, DIM, and DIM with ENZ. Exposure of ENZ-resistant cells to both DIM and ENZ significantly inhibited cell proliferation without cytotoxicity and invasion in comparison with the control. DIM significantly increased the E-cadherin expression and inhibited the expressions of Vimentin and Fibronectin, subsequently inhibiting EMT. Co-treatment with ENZ and DIM significantly increased the expressions of GSK3β and APC and decreased the β-catenin protein expression, causing inhibition of Wnt signaling and AR expression, it also significantly decreased the AR-v7 expression and down-regulated AR signaling. Via suppression of Wnt and AR signaling, co-treatment increased the E-cadherin and decreased the Vimentin and Fibronectin RNA and protein expressions, then inhibited EMT. Co-treatment with DIM and ENZ regulated Wnt signaling to reduce not only the AR expression, but also the AR-v7 expression, indicating suppression of EMT that inhibits cancer cell proliferation, invasion and migration to ameliorate ENZ resistance.

Establishment of Acquired Cisplatin Resistance in Ovarian Cancer Cell Lines Characterized by Enriched Metastatic Properties with Increased Twist Expression

Ovarian cancer (OC) is the most lethal of the gynecologic cancers, and platinum-based treatment is a part of the standard first-line chemotherapy regimen. However, rapid development of acquired cisplatin resistance remains the main cause of treatment failure, and the underlying mechanism of resistance in OC treatment remains poorly understood. Faced with this problem, our aim in this study was to generate cisplatin-resistant (CisR) OC cell models in vitro and investigate the role of epithelial–mesenchymal transition (EMT) transcription factor Twist on acquired cisplatin resistance in OC cell models. To achieve this aim, OC cell lines OV-90 and SKOV-3 were exposed to cisplatin using pulse dosing and stepwise dose escalation methods for a duration of eight months, and a total of four CisR sublines were generated, two for each cell line. The acquired cisplatin resistance was confirmed by determination of 50% inhibitory concentration (IC₅₀) and clonogenic survival assay. Furthermore, the CisR cells were studied to assess their respective characteristics of metastasis, EMT phenotype, DNA repair and endoplasmic reticulum stress-mediated cell death. We found the IC₅₀ of CisR cells to cisplatin was 3–5 times higher than parental cells. The expression of Twist and metastatic ability of CisR cells were significantly greater than those of sensitive cells. The CisR cells displayed an EMT phenotype with decreased epithelial cell marker E-cadherin and increased mesenchymal proteins N-cadherin and vimentin. We observed that CisR cells showed significantly higher expression of DNA repair proteins, X-ray repair cross-complementing protein 1 (XRCC1) and poly (ADP-ribose) polymerases 1 (PARP1), with significantly reduced endoplasmic reticulum (ER) stress-mediated cell death. Moreover, Twist knockdown reduced metastatic ability of CisR cells by suppressing EMT, DNA repair and inducing ER stress-induced cell death. In conclusion, we highlighted the utilization of an acquired cisplatin resistance model to identify the potential role of Twist as a therapeutic target to reverse acquired cisplatin resistance in OC.

Prostate cancer liver metastasis: Dormancy and resistance to therapy

Liver metastasis causes nearly half of death from solid tumors. Metastatic lesions, to the liver in particular, can become detectable years or decades after primary tumor removal, leaving an uncertain long-term prognosis in patients. Prostate cancer (PCa), a prominent metastatic dormant cancer, has the worst prognosis when found in the liver compared to other metastatic sites. These metastatic nodules display a therapy resistance in the liver pro-metastatic microenvironment; the resistance appears to be conferred by both dormancy and independent of dormancy when the nodules emerge. Within the review, the molecular underpinnings of how the liver aids and protects PCa cells seeding, colonization and resistance will be discussed.

Clonal Evolution and Epithelial Plasticity in the Emergence of AR-Independent Prostate Carcinoma

In spite of an initial clinical response to androgen deprivation therapy (ADT), the majority of prostate cancer patients eventually develop castration-resistant prostate cancer (CRPC). Recent studies have highlighted the role of epithelial plasticity, including transdifferentiation and epithelial-to-mesenchymal transition (EMT), in the development of AR pathway-negative CRPC, a form of the disease that has increased in incidence after the introduction of potent AR inhibitors. In this review, we will discuss the switches between different cell fates that occur in response to AR blockade or acquisition of specific oncogenic mutations, such as those in TP53 and RB1, during the evolution to CRPC. We highlight the urgent need to dissect the mechanistic underpinnings of these transitions and identify novel vulnerabilities that can be targeted therapeutically.

Pharmacodynamic study of radium-223 in men with bone metastatic castration resistant prostate cancer

BACKGROUND

Radium-223 is a targeted alpha-particle therapy that improves survival in men with metastatic castration resistant prostate cancer (mCRPC), particularly in men with elevated serum levels of bone alkaline phosphatase (B-ALP). We hypothesized that osteomimicry, a form of epithelial plasticity leading to an osteoblastic phenotype, may contribute to intralesional deposition of radium-223 and subsequent irradiation of the tumor microenvironment.

METHODS

We conducted a pharmacodynamic study (NCT02204943) of radium-223 in men with bone mCRPC. Prior to and three and six months after radium-223 treatment initiation, we collected CTCs and metastatic biopsies for phenotypic characterization and CTC genomic analysis. The primary objective was to describe the impact of radium-223 on the prevalence of CTC B-ALP over time. We measured radium-223 decay products in tumor and surrounding normal bone during treatment. We validated genomic findings in a separate independent study of men with bone metastatic mCRPC (n = 45) and publicly accessible data of metastatic CRPC tissues.

RESULTS

We enrolled 20 men with symptomatic bone predominant mCRPC and treated with radium-223. We observed greater radium-223 radioactivity levels in metastatic bone tumor containing biopsies compared with adjacent normal bone. We found evidence of persistent Cellsearch CTCs and B-ALP (+) CTCs in the majority of men over time during radium-223 therapy despite serum B-ALP normalization. We identified genomic gains in osteoblast mimicry genes including gains of ALPL, osteopontin, SPARC, OB-cadherin and loss of RUNX2, and validated genomic alterations or increased expression at the DNA and RNA level in an independent cohort of 45 men with bone-metastatic CRPC and in 150 metastatic biopsies from men with mCRPC.

CONCLUSIONS

Osteomimicry may contribute in part to the uptake of radium-223 within bone metastases and may thereby enhance the therapeutic benefit of this bone targeting radiotherapy.

RPS7 promotes cell migration through targeting epithelial-mesenchymal transition in prostate cancer

OBJECTIVES

Small ribosomal protein subunit 7 (RPS7) is an important structural components of the ribosome involved in protein synthesis, previous studies demonstrated that RPS7 was associated with several malignancies, but the role of RPS7 in prostate cancer (PCa) remains unclear. To decipher such a puzzle, in the current study, we deciphered the role and mechanism of RPS7 during the progression of PCa.

MATERIAL AND METHODS

In this study, the expression of mRNA was performed by quantitative real-time PCR. The protein level was identified by Western blotting. Kaplan-Meier survival analysis was demonstrated the relation between the abnormal expression of RPS7 mRNA and the overall survival. Cell proliferation was assessed by MTT assay and cell counting, meanwhile, cell migration was checked by transwell assay.

RESULTS

RPS7 is higher expressed in PCa (p < 0.001), and the overexpression of RPS7 is closely associated with poor outcome of PCa patients after radical prostatectomy (p < 0.001). Inhibition the expression of RPS7 with a specific RPS7 siRNA could markedly attenuate prostate tumor growth and migration (p < 0.05). Mechanistic data reveals that inhibition of RPS7 could up-regulate the epithelial protein marker, E-cadherin (p < 0.05), and down-regulate the mesenchymal protein markers, such as N-cadherin and Snail (p < 0.001).

CONCLUSIONS

RPS7 is a newly verified tumor promoter in PCa, and promotes cell migration by targeting epithelial-to-mesenchymal transitionpathway. Thus, inhibition of RPS7-epithelial to-mesenchymal transition signaling might represent a prospective approach toward limiting prostate tumor progression.

Molecular Mechanisms Related to Hormone Inhibition Resistance in Prostate Cancer

Management of metastatic or advanced prostate cancer has acquired several therapeutic approaches that have drastically changed the course of the disease. In particular due to the high sensitivity of prostate cancer cells to hormone depletion, several agents able to inhibit hormone production or binding to nuclear receptor have been evaluated and adopted in clinical practice. However, despite several hormonal treatments being available nowadays for the management of advanced or metastatic prostate cancer, the natural history of the disease leads inexorably to the development of resistance to hormone inhibition. Findings regarding the mechanisms that drive this process are of particular and increasing interest as these are potentially related to the identification of new targetable pathways and to the development of new drugs able to improve our patients' clinical outcomes.

Centromere protein F (CENPF), a microtubule binding protein, modulates cancer metabolism by regulating pyruvate kinase M2 phosphorylation signaling

Prostate cancer (PC) is the most commonly diagnosed cancer in men and is the second leading cause of male cancer-related death in North America. Metabolic adaptations in malignant PC cells play a key role in fueling the growth and progression of the disease. Unfortunately, little is known regarding these changes in cellular metabolism. Here, we demonstrate that centromere protein F (CENPF), a protein associated with the centromere-kinetochore complex and chromosomal segregation during mitosis, is mechanically linked to altered metabolism and progression in PC. Using the CRISPR-Cas9 system, we silenced the gene for CENPF in human PC3 cells. These cells were found to have reduced levels of epithelial-mesenchymal transition markers and inhibited cell proliferation, migration, and invasion. Silencing of CENPF also simultaneously improved sensitivity to anoikis-induced apoptosis. Mass spectrometry analysis of tyrosine phosphorylated proteins from CENPF knockout (CENPFKO) and control cells revealed that CENPF silencing increased inactive forms of pyruvate kinase M2, a rate limiting enzyme needed for an irreversible reaction in glycolysis. Furthermore, CENPFKO cells had reduced global bio-energetic capacity, acetyl-CoA production, histone acetylation, and lipid metabolism, suggesting that CENPF is a critical regulator of cancer metabolism, potentially through its effects on mitochondrial functioning. Additional quantitative immunohistochemistry and imaging analyzes on a series of PC tumor microarrays demonstrated that CENPF expression is significantly increased in higher-risk PC patients. Based on these findings, we suggest the CENPF may be an important regulator of PC metabolism through its role in the mitochondria.

Suppressed epithelial-mesenchymal transition and cancer stem cell properties mediate the anti-cancer effects of ethyl pyruvate via regulation of the AKT/nuclear factor-κB pathway in prostate cancer cells

Castration-resistant prostate cancer (CRPC) is a leading cause of mortality among cases of prostate cancer (PCa). Current treatment options for CRPC are limited. Ethyl pyruvate (EP), a lipophilic derivative of pyruvic acid, has been reported to have antitumor activities. In the present study, the efficacy of EP against PCa was investigated using two human PCa cell lines and a mouse xenograft tumor model. PC3 and CWR22RV1 cells were treated with EP, and cytotoxicity was evaluated via Cell Counting Kit-8 and colony formation assays, while cell cycle distribution was assessed by flow cytometry. Changes in cell migration and invasion caused by EP treatment were also evaluated with Transwell and wound healing assays, and changes in the expression of intracellular signaling pathway components were detected by western blotting. EP treatment reduced cell viability, induced G1 arrest, and activated the intrinsic apoptosis pathway. Additionally, the in vivo experiments revealed that EP administration markedly inhibited tumor growth. EP also reversed epithelial-mesenchymal transition and suppressed cancer stem cell properties in part through negative regulation of AKT/nuclear factor-κB signaling. These results indicate that EP has anticancer activity in vitro and in vivo, and is therefore a promising therapeutic agent for the treatment of PCa.

Juglone suppresses epithelial-mesenchymal transition in prostate cancer cells via the protein kinase B/glycogen synthase kinase-3β/Snail signaling pathway

Epithelial-mesenchymal transition (EMT) serves an important role in the metastasis of prostate cancer. Juglone is a natural compound isolated from plants that is reported to possess potent cytotoxic properties. However, there are no studies on the anti-EMT effect of juglone in prostate cancer, or its potential underlying mechanisms of action. In the present study, the effect of juglone on the EMT of prostate cancer cells was investigated. Transwell assays were used to demonstrate that juglone inhibits the migration and invasion of the prostate cancer (PC) LNCaP and LNCaP-AI cell lines. Results from western blot analysis demonstrated that juglone increases the expression of the epithelial marker E-cadherin while decreasing the expression of mesenchymal markers (N-cadherin and Vimentin) in a dose-dependent manner. The data from the present study also revealed that juglone downregulates the expression of Snail, a repressor of E-cadherin and an inducer of EMT. Furthermore, juglone prevented inactivation of glycogen synthase kinase-3β (GSK-3β), an endogenous inhibitor of Snail in a dose-dependent manner. Lithium chloride (LiCl), a GSK-3β inhibitor, prevented juglone-mediated downregulation of Snail expression and upregulation of E-cadherin. In addition, phosphorylation and subsequent activation of protein kinase B (Akt), which is known to phosphorylate GSK-3β at serine 9 (Ser9), leading to its inhibition, were significantly decreased by juglone in LNCaP and LNCaP-AI cells. Inhibition of the phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K)/Akt pathway by LY294002 augmented juglone-mediated GSK-3β activity by inhibiting Ser9 phosphorylation. These findings indicated that juglone suppresses EMT via the Akt/GSK-3β/Snail pathway, consequently decreasing the invasiveness of PC cells.

Epithelial-mesenchymal transition in prostate cancer: an overview

Prostate cancer is a main urological disease associated with significant morbidity and mortality. Radical prostatectomy and radiotherapy are potentially curative for localized prostate cancer, while androgen deprivation therapy is the initial systemic therapy for metastatic prostate disease. However, despite temporary response, most patients relapse and evolve into castration resistant cancer.

Epithelial-mesenchymal transition (EMT) is a complex gradual process that occurs during embryonic development and/or tumor progression. During this process, cells lose their epithelial characteristics and acquire mesenchymal features. Increasing evidences indicate that EMT promotes prostate cancer metastatic progression and it is closely correlated with increased stemness and drug resistance.

In this review, we discuss the main molecular events that directly or indirectly govern the EMT program in prostate cancer, in order to better define the role and the mechanisms underlying this process in prostate cancer progression and therapeutic resistance.

ITGB1-dependent upregulation of Caveolin-1 switches TGFβ signalling from tumour-suppressive to oncogenic in prostate cancer

Caveolin-1 (CAV1) is over-expressed in prostate cancer (PCa) and is associated with adverse prognosis, but the molecular mechanisms linking CAV1 expression to disease progression are poorly understood. Extensive gene expression correlation analysis, quantitative multiplex imaging of clinical samples, and analysis of the CAV1-dependent transcriptome, supported that CAV1 re-programmes TGFβ signalling from tumour suppressive to oncogenic (i.e. induction of SLUG, PAI-1 and suppression of CDH1, DSP, CDKN1A). Supporting such a role, CAV1 knockdown led to growth arrest and inhibition of cell invasion in prostate cancer cell lines. Rationalized RNAi screening and high-content microscopy in search for CAV1 upstream regulators revealed integrin beta1 (ITGB1) and integrin associated proteins as CAV1 regulators. Our work suggests TGFβ signalling and beta1 integrins as potential therapeutic targets in PCa over-expressing CAV1, and contributes to better understand the paradoxical dual role of TGFβ in tumour biology.

Metformin reverses prostate cancer resistance to enzalutamide by targeting TGF-β1/STAT3 axis-regulated EMT

Although the newly developed second-generation anti-androgen drug enzalutamide can repress prostate cancer progression significantly, it only extends the survival of prostate cancer patients by 4–6 months mainly due to the occurrence of enzalutamide resistance. Most of the previous studies on AR antagonist resistance have been focused on AR signaling. Therefore, the non-AR pathways on enzalutamide resistance remain largely unknown. By using C4-2, CWR22Rv1 and LNCaP cell lines, as well as mice bearing CWR22Rv1 xenografts treated with either enzalutamide or metformin alone or in combination, we demonstrated that metformin is capable of reversing enzalutamide resistance and restores sensitivity of CWR22Rv1 xenografts to enzalutamide. We showed that metformin alleviated resistance to enzalutamide by inhibiting EMT. Furthermore, based on the effect of metformin on the activation of STAT3 and expression of TGF-β1, we propose that metformin exerts its effects by targeting the TGF-β1/STAT3 axis. These findings suggest that combination of metformin with enzalutamide could be a more efficacious therapeutic strategy for the treatment of castration-resistant prostate cancer.

Biphasic malignant tumours of the abdominal cavity

Carcinosarcomas (CS) are uncommon, highly aggressive, biphasic tumours consisting of both sarcomatous and carcinomatous elements. They appear to originate from a common cell of origin, either via transformation from a single premature precursor or conversion of a mature epithelial cell through an epithelial-mesenchymal transition. CS should be considered a unique cancer subtype with cells typically displaying diffuse mitotic activity and widespread atypical mitoses predisposing to early metastasis and a tendency to local recurrence following resection. This review addresses the pathophysiology of CS and discusses its presentation, natural history and management at a variety of sites within the abdominal cavity and retroperitoneum.

Label-free isolation of prostate circulating tumor cells using Vortex microfluidic technology

There has been increased interest in utilizing non-invasive "liquid biopsies" to identify biomarkers for cancer prognosis and monitoring, and to isolate genetic material that can predict response to targeted therapies. Circulating tumor cells (CTCs) have emerged as such a biomarker providing both genetic and phenotypic information about tumor evolution, potentially from both primary and metastatic sites. Currently, available CTC isolation approaches, including immunoaffinity and size-based filtration, have focused on high capture efficiency but with lower purity and often long and manual sample preparation, which limits the use of captured CTCs for downstream analyses. Here, we describe the use of the microfluidic Vortex Chip for size-based isolation of CTCs from 22 patients with advanced prostate cancer and, from an enumeration study on 18 of these patients, find that we can capture CTCs with high purity (from 1.74 to 37.59%) and efficiency (from 1.88 to 93.75 CTCs/7.5 mL) in less than 1 h. Interestingly, more atypical large circulating cells were identified in five age-matched healthy donors (46-77 years old; 1.25-2.50 CTCs/7.5 mL) than in five healthy donors <30 years old (21-27 years old; 0.00 CTC/7.5 mL). Using a threshold calculated from the five age-matched healthy donors (3.37 CTCs/mL), we identified CTCs in 80% of the prostate cancer patients. We also found that a fraction of the cells collected (11.5%) did not express epithelial prostate markers (cytokeratin and/or prostate-specific antigen) and that some instead expressed markers of epithelial-mesenchymal transition, i.e., vimentin and N-cadherin. We also show that the purity and DNA yield of isolated cells is amenable to targeted amplification and next-generation sequencing, without whole genome amplification, identifying unique mutations in 10 of 15 samples and 0 of 4 healthy samples.

Induction of Mesenchymal-Epithelial Transitions in Sarcoma Cells

Phenotypic plasticity refers to a phenomenon in which cells transiently gain traits of another lineage. During carcinoma progression, phenotypic plasticity drives invasion, dissemination and metastasis. Indeed, while most of the studies of phenotypic plasticity have been in the context of epithelial-derived carcinomas, it turns out sarcomas, which are mesenchymal in origin, also exhibit phenotypic plasticity, with a subset of sarcomas undergoing a phenomenon that resembles a mesenchymal-epithelial transition (MET). Here, we developed a method comprising the miR-200 family and grainyhead-like 2 (GRHL2) to mimic this MET-like phenomenon observed in sarcoma patient samples.We sequentially express GRHL2 and the miR-200 family using cell transduction and transfection, respectively, to better understand the molecular underpinnings of these phenotypic transitions in sarcoma cells. Sarcoma cells expressing miR-200s and GRHL2 demonstrated enhanced epithelial characteristics in cell morphology and alteration of epithelial and mesenchymal biomarkers. Future studies using these methods can be used to better understand the phenotypic consequences of MET-like processes on sarcoma cells, such as migration, invasion, metastatic propensity, and therapy resistance.

Upregulation of FAM84B during prostate cancer progression

Although the FAM84B gene lies within chromosome 8q24, a locus frequently altered in prostate cancer (PC), its alteration during prostate tumorigenesis has not been well studied. We report here FAM84B upregulation in DU145 cell-derived prostate cancer stem-like cells (PCSLCs) and DU145 cell-produced lung metastases compared to subcutaneous xenograft tumors. FAM84B protein was detected in bone metastases and primary PCs. Nanostring examination of 7 pairs of tumor adjacent normal and PC tissues revealed elevations in FAM84B mRNA levels in all carcinomas. Furthermore, through analysis of FAM84B expression using large datasets within the Gene Expression Omnibus and OncomineTM database, we demonstrate significant increases in FAM84B mRNA in 343 primary PCs versus 181 normal tissues, and elevations in the FAM84B gene copy number (GCN) in 171 primary PCs versus 61 normal tissues. While FAM84B was not detected at higher levels via immunohistochemistry in high grade (Gleason score/GS 8-10) tumors compared to GS6-7 PCs, analyses of FAM84B mRNA and GCN using datasets within the cBioPortal database demonstrated FAM84B upregulation in 12% (67/549) of primary PCs and 18% (73/412) of metastatic castration resistant PCs (mCRPCs), and GCN increases in 4.8% (26/546) of primary PCs and 26% (121/467) of mCRPCs, revealing an association of the aforementioned changes with CRPC development. Of note, an increase in FAM84B expression was observed in xenograft CRPCs produced by LNCaP cells. Furthermore, FAM84B upregulation and GCN increases correlate with decreases in disease free survival and overall survival. Collectively, we demonstrate a novel association of FAM84B with PC tumorigenesis and CRPC progression.

EGFR-Based Immunoisolation as a Recovery Target for Low-EpCAM CTC Subpopulation

Circulating tumour cells (CTCs) play a key role in the metastasis process, as they are responsible for micrometastasis and are a valuable tool for monitoring patients in real-time. Moreover, efforts to develop new strategies for CTCs isolation and characterisation, and the translation of CTCs into clinical practice needs to overcome the limitation associated with the sole use of Epithelial Cell Adhesion Molecule (EpCAM) expression to purify this tumour cell subpopulation. CTCs are rare events in the blood of patients and are believed to represent the epithelial population from a primary tumour of epithelial origin, thus EpCAM immunoisolation is considered an appropriate strategy. The controversy stems from the impact that the more aggressive mesenchymal tumour phenotypes might have on the whole CTC population. In this work, we first characterised a panel of cell lines representative of tumour heterogeneity, confirming the existence of tumour cell subpopulations with restricted epithelial features and supporting the limitations of EpCAM-based technologies. We next developed customised polystyrene magnetic beads coated with antibodies to efficiently isolate the phenotypically different subpopulations of CTCs from the peripheral blood mononuclear cells (PBMCs) of patients with metastatic cancer. Besides EpCAM, we propose Epidermal Growth Factor Receptor (EGFR) as an additional isolation marker for efficient CTCs detection.

Mesenchymal-Epithelial Transition in Sarcomas Is Controlled by the Combinatorial Expression of MicroRNA 200s and GRHL2

Phenotypic plasticity involves a process in which cells transiently acquire phenotypic traits of another lineage. Two commonly studied types of phenotypic plasticity are epithelial-mesenchymal transition (EMT) and mesenchymal-epithelial transition (MET). In carcinomas, EMT drives invasion and metastatic dissemination, while MET is proposed to play a role in metastatic colonization. Phenotypic plasticity in sarcomas is not well studied; however, there is evidence that a subset of sarcomas undergo an MET-like phenomenon. While the exact mechanisms by which these transitions occur remain largely unknown, it is likely that some of the same master regulators that drive EMT and MET in carcinomas also act in sarcomas. In this study, we combined mathematical models with bench experiments to identify a core regulatory circuit that controls MET in sarcomas. This circuit comprises the microRNA 200 (miR-200) family, ZEB1, and GRHL2. Interestingly, combined expression of miR-200s and GRHL2 further upregulates epithelial genes to induce MET. This effect is phenocopied by downregulation of either ZEB1 or the ZEB1 cofactor, BRG1. In addition, an MET gene expression signature is prognostic for improved overall survival in sarcoma patients. Together, our results suggest that a miR-200, ZEB1, GRHL2 gene regulatory network may drive sarcoma cells to a more epithelial-like state and that this likely has prognostic relevance.

Androgen receptor variant-driven prostate cancer: clinical implications and therapeutic targeting

While there are myriad mechanisms of primary and acquired resistance to conventional and next-generation hormonal therapies in prostate cancer, the potential role of androgen receptor splice variants (AR-Vs) has recently gained momentum. AR-Vs are abnormally truncated isoforms of the androgen receptor (AR) protein that lack the COOH-terminal domain but retain the NH2-terminal domain and DNA-binding domain and are thus constitutively active even in the absence of ligands. Although multiple preclinical studies have previously implicated AR-Vs in the development of castration resistance as well as resistance to abiraterone and enzalutamide, recent technological advances have made it possible to reliably detect and quantify AR-Vs from human clinical tumor specimens including blood samples. Initial clinical studies have now shown that certain AR-Vs, in particular AR-V7, may be associated with resistance to abiraterone and enzalutamide but not taxane chemotherapies when detected in circulating tumor cells. Efforts are now underway to clinically validate AR-V7 as a relevant treatment-selection biomarker in the context of other key genomic aberrations in men with metastatic castration-resistant prostate cancer. Additional efforts are underway to therapeutically target both AR and AR-Vs either directly or indirectly. Whether AR-Vs represent drivers of castration-resistant prostate cancer, or whether they are simply passenger events associated with aggressive disease or clonal heterogeneity, will ultimately be answered only through these types of clinical trials.

Snail promotes resistance to enzalutamide through regulation of androgen receptor activity in prostate cancer

Treatment with androgen-targeted therapies can induce upregulation of epithelial plasticity pathways. Epithelial plasticity is known to be important for metastatic dissemination and therapeutic resistance. The goal of this study is to elucidate the functional consequence of induced epithelial plasticity on AR regulation during disease progression to identify factors important for treatment-resistant and metastatic prostate cancer. We pinpoint the epithelial plasticity transcription factor, Snail, at the nexus of enzalutamide resistance and prostate cancer metastasis both in preclinical models of prostate cancer and in patients. In patients, Snail expression is associated with Gleason 9-10 high-risk disease and is strongly overexpressed in metastases as compared to localized prostate cancer. Snail expression is also elevated in enzalutamide-resistant prostate cancer cells compared to enzalutamide-sensitive cells, and downregulation of Snail re-sensitizes enzalutamide-resistant cells to enzalutamide. While activation of Snail increases migration and invasion, it is also capable of promoting enzalutamide resistance in enzalutamide-sensitive cells. This Snail-mediated enzalutamide resistance is a consequence of increased full-length AR and AR-V7 expression and nuclear localization. Downregulation of either full-length AR or AR-V7 re-sensitizes cells to enzalutamide in the presence of Snail, thus connecting Snail-induced enzalutamide resistance directly to AR biology. Finally, we demonstrate that Snail is capable of mediating-resistance through AR even in the absence of AR-V7. These findings imply that increased Snail expression during progression to metastatic disease may prime cells for resistance to AR-targeted therapies by promoting AR activity in prostate cancer.

A ZEB1-miR-375-YAP1 pathway regulates epithelial plasticity in prostate cancer

MicroRNA-375 (miR-375) is frequently elevated in prostate tumors and cell-free fractions of patient blood, but its role in genesis and progression of prostate cancer is poorly understood. In this study, we demonstrated that miR-375 is inversely correlated with epithelial-mesenchymal transition signatures (EMT) in clinical samples and can drive mesenchymal-epithelial transition (MET) in model systems. Indeed, miR-375 potently inhibited invasion and migration of multiple prostate cancer lines. The transcription factor YAP1 was found to be a direct target of miR-375 in prostate cancer. Knockdown of YAP1 phenocopied miR-375 overexpression, and overexpression of YAP1 rescued anti-invasive effects mediated by miR-375. Furthermore, transcription of the miR-375 gene was shown to be directly repressed by the EMT transcription factor, ZEB1. Analysis of multiple patient cohorts provided evidence for this ZEB1-miR-375-YAP1 regulatory circuit in clinical samples. Despite its anti-invasive and anti-EMT capacities, plasma miR-375 was found to be correlated with circulating tumor cells in men with metastatic disease. Collectively, this study provides new insight into the function of miR-375 in prostate cancer, and more broadly identifies a novel pathway controlling epithelial plasticity and tumor cell invasion in this disease.

Regulation of a TGF-β1-CD147 self-sustaining network in the differentiation plasticity of hepatocellular carcinoma cells

Cellular plasticity has an important role in the progression of hepatocellular carcinoma (HCC). In this study, the involvement of a TGF-β1-CD147 self-sustaining network in the regulation of the dedifferentiation progress was fully explored in HCC cell lines, hepatocyte-specific basigin/CD147-knockout mice and human HCC tissues. We demonstrated that TGF-β1 stimulation upregulated CD147 expression and mediated the dedifferentiation of HCC cells, whereas all-trans-retinoic acid induced the downregulation of CD147 and promoted differentiation in HCC cells. Overexpression of CD147 induced the dedifferentiation and enhanced the malignancy of HCC cells, and increased the transcriptional expression of TGF-β1 by activating β-catenin. CD147-induced matrix metalloproteinase (MMP) production activated pro-TGF-β1. The activated TGF-β1 signaling subsequently repressed the HNF4α expression via Smad-Snail1 signaling and enhanced the dedifferentiation progress. Hepatocyte-specific basigin/CD147-knockout mice decreased the susceptibility to N-nitrosodiethylamine-induced tumorigenesis by suppressing TGF-β1-CD147 signaling and inhibiting dedifferentiation in hepatocytes during tumor progression. CD147 was positively correlated with TGF-β1 and negatively correlated with HNF4α in human HCC tissues. Positive CD147 staining and lower HNF4α levels in tumor tissues were significantly associated with poor survival of patients with HCC. The overexpression of HNF4α and Smad7 and the deletion of CD147 by lentiviral vectors jointly reprogrammed the expression profile of hepatocyte markers and attenuated malignant properties including proliferation, cell survival and tumor growth of HCC cells. Our results highlight the important role of the TGF-β1-CD147 self-sustaining network in driving HCC development by regulating differentiation plasticity, which provides a strong basis for further investigations of the differentiation therapy of HCC targeting TGF-β1 and CD147.

Development of a Novel c-MET-Based CTC Detection Platform

Amplification of the MET oncogene is associated with poor prognosis, metastatic dissemination, and drug resistance in many malignancies. We developed a method to capture and characterize circulating tumor cells (CTC) expressing c-MET using a ferromagnetic antibody. Immunofluorescence was used to characterize cells for c-MET, DAPI, and pan-CK, excluding CD45(+) leukocytes. The assay was validated using appropriate cell line controls spiked into peripheral blood collected from healthy volunteers (HV). In addition, peripheral blood was analyzed from patients with metastatic gastric, pancreatic, colorectal, bladder, renal, or prostate cancers. CTCs captured by c-MET were enumerated, and DNA FISH for MET amplification was performed. The approach was highly sensitive (80%) for MET-amplified cells, sensitive (40%-80%) for c-MET-overexpressed cells, and specific (100%) for both c-MET-negative cells and in 20 HVs. Of 52 patients with metastatic carcinomas tested, c-MET CTCs were captured in replicate samples from 3 patients [gastric, colorectal, and renal cell carcinoma (RCC)] with 6% prevalence. CTC FISH demonstrated that MET amplification in both gastric and colorectal cancer patients and trisomy 7 with gain of MET gene copies in the RCC patient. The c-MET CTC assay is a rapid, noninvasive, sensitive, and specific method for detecting MET-amplified tumor cells. CTCs with MET amplification can be detected in patients with gastric, colorectal, and renal cancers.

IMPLICATIONS

This study developed a novel c-MET CTC assay for detecting c-MET CTCs in patients with MET amplification and warrants further investigation to determine its clinical applicability. Mol Cancer Res; 14(6); 539-47. ©2016 AACR.

Homeostatic Signaling by Cell-Cell Junctions and Its Dysregulation during Cancer Progression

The transition of sessile epithelial cells to a migratory, mesenchymal phenotype is essential for metazoan development and tissue repair, but this program is exploited by tumor cells in order to escape the confines of the primary organ site, evade immunosurveillance, and resist chemo-radiation. In addition, epithelial-to-mesenchymal transition (EMT) confers stem-like properties that increase efficiency of colonization of distant organs. This review evaluates the role of cell–cell junctions in suppressing EMT and maintaining a quiescent epithelium. We discuss the conflicting data on junctional signaling in cancer and recent developments that resolve some of these conflicts. We focus on evidence from breast cancer, but include other organ sites where appropriate. Current and potential strategies for inhibition of EMT are discussed.

AR-V7 and prostate cancer: The watershed for treatment selection?

The androgen receptor (AR) plays a key role in progression to metastatic castration-resistant prostate cancer (mCRPC). Despite the recent progress in targeting persistent AR activity with the next-generation hormonal therapies (abiraterone acetate and enzalutamide), resistance to these agents limits therapeutic efficacy for many patients. Several explanations for response and/or resistance to abiraterone acetate and enzalutamide are emerging, but growing interest is focusing on importance of AR splice variants (AR-Vs) and in particular of AR-V7. Increasing evidences highlight the concept that variant expression could be used as a potential predictive biomarker and a therapeutic target in advanced prostate cancer. Therefore, understanding the mechanisms of treatment resistance or sensitivity can help to achieve a more effective management of mCRPC, increasing clinical outcomes and representing a promising and engaging area of prostate cancer research.

HDAC inhibition impedes epithelial-mesenchymal plasticity and suppresses metastatic, castration-resistant prostate cancer

PI3K/AKT and RAS/MAPK pathway co-activation in the prostate epithelium promotes both epithelial-mesenchymal transition (EMT) and metastatic castration-resistant prostate cancer (mCRPC), which is currently incurable. To study the dynamic regulation of the EMT process, we developed novel genetically-defined cellular and in vivo model systems from which epithelial, EMT, and mesenchymal-like tumor cells with Pten deletion and Kras activation can be isolated. When cultured individually, each population has the capacity to regenerate all three tumor cell populations, indicative of epithelial-mesenchymal plasticity. Despite harboring the same genetic alterations, mesenchymal-like tumor cells are resistant to PI3K and MAPK pathway inhibitors, suggesting that epigenetic mechanisms may regulate the EMT process, as well as dictate the heterogeneous responses of cancer cells to therapy. Among differentially expressed epigenetic regulators, the chromatin remodeling protein HMGA2 is significantly upregulated in EMT and mesenchymal-like tumors cells, as well as in human mCRPC. Knockdown of HMGA2, or suppressing HMGA2 expression with the histone deacetylase (HDAC) inhibitor LBH589, inhibits epithelial-mesenchymal plasticity and stemness activities in vitro and dramatically reduces tumor growth and metastasis in vivo through successful targeting of EMT and mesenchymal-like tumor cells. Importantly, LBH589 treatment in combination with castration prevents mCRPC development and significantly prolongs survival following castration by enhancing p53 and AR acetylation and in turn sensitizing castration-resistant mesenchymal-like tumor cells to ADT. Taken together, these findings demonstrate that cellular plasticity is regulated epigenetically, and that mesenchymal-like tumor cell populations in mCRPC that are resistant to conventional and targeted therapies can be effectively treated with the epigenetic inhibitor LBH589.

Prostate Cancer Stem-like Cells Contribute to the Development of Castration-Resistant Prostate Cancer

Androgen deprivation therapy (ADT) has been the standard care for patients with advanced prostate cancer (PC) since the 1940s. Although ADT shows clear benefits for many patients, castration-resistant prostate cancer (CRPC) inevitably occurs. In fact, with the two recent FDA-approved second-generation anti-androgens abiraterone and enzalutamide, resistance develops rapidly in patients with CRPC, despite their initial effectiveness. The lack of effective therapeutic solutions towards CRPC largely reflects our limited understanding of the underlying mechanisms responsible for CRPC development. While persistent androgen receptor (AR) signaling under castration levels of serum testosterone (<50 ng/mL) contributes to resistance to ADT, it is also clear that CRPC evolves via complex mechanisms. Nevertheless, the physiological impact of individual mechanisms and whether these mechanisms function in a cohesive manner in promoting CRPC are elusive. In spite of these uncertainties, emerging evidence supports a critical role of prostate cancer stem-like cells (PCSLCs) in stimulating CRPC evolution and resistance to abiraterone and enzalutamide. In this review, we will discuss the recent evidence supporting the involvement of PCSLC in CRPC acquisition as well as the pathways and factors contributing to PCSLC expansion in response to ADT.

Evaluation of an epithelial plasticity biomarker panel in men with localized prostate cancer

BACKGROUND

Given the potential importance of epithelial plasticity (EP) to cancer metastasis, we sought to investigate biomarkers related to EP in men with localized prostate cancer (PC) for the association with time to PSA recurrence and other clinical outcomes after surgery.

METHODS

Men with localized PC treated with radical prostatectomy at the Durham VA Medical Center and whose prostatectomy tissues were included in a tissue microarray (TMA) linked to long-term outcomes. We performed immunohistochemical studies using validated antibodies against E-cadherin and Ki-67 and mesenchymal biomarkers including N-cadherin, vimentin, SNAIL, ZEB1 and TWIST. Association studies were conducted for each biomarker with baseline clinical/pathologic characteristics an risk of PSA recurrence over time.

RESULTS

Two hundred and five men contributed TMA tissue and had long-term follow-up (median 11 years). Forty-three percent had PSA recurrence; three died of PC. The majority had high E-cadherin expression (86%); 14% had low/absent E-cadherin expression. N-cadherin was rarely expressed (<4%) and we were unable to identify an E-to-N-cadherin switch as independently prognostic. No associations with clinical risk group, PSA recurrence or Gleason sum were noted for SNAIL, ZEB1, vimentin or TWIST, despite heterogeneous expression between patients. We observed an association of higher Ki-67 expression with Gleason sum (P=0.043), National Comprehensive Cancer Network risk (P=0.013) and PSA recurrence (hazard ratio 1.07, P=0.016).

CONCLUSIONS

The expression of EP biomarkers in this cohort of men with a low risk of PC-specific mortality was not associated with aggressive features or PSA relapse after surgery.

Using circulating tumor cells to inform on prostate cancer biology and clinical utility

Substantial advances in the molecular biology of prostate cancer have led to the approval of multiple new systemic agents to treat men with metastatic castration-resistant prostate cancer (mCRPC). These treatments encompass androgen receptor directed therapies, immunotherapies, bone targeting radiopharmaceuticals and cytotoxic chemotherapies. There is, however, great heterogeneity in the degree of patient benefit with these agents, thus fueling the need to develop predictive biomarkers that are able to rationally guide therapy. Circulating tumor cells (CTCs) have the potential to provide an assessment of tumor-specific biomarkers through a non-invasive, repeatable "liquid biopsy" of a patient's cancer at a given point in time. CTCs have been extensively studied in men with mCRPC, where CTC enumeration using the Cellsearch® method has been validated and FDA approved to be used in conjunction with other clinical parameters as a prognostic biomarker in metastatic prostate cancer. In addition to enumeration, more sophisticated molecular profiling of CTCs is now feasible and may provide more clinical utility as it may reflect tumor evolution within an individual particularly under the pressure of systemic therapies. Here, we review technologies used to detect and characterize CTCs, and the potential biological and clinical utility of CTC molecular profiling in men with metastatic prostate cancer.

Cellular Plasticity in Prostate Cancer Bone Metastasis

Purpose. Experimental data suggest that tumour cells can reversibly transition between epithelial and mesenchymal states (EMT and MET), a phenomenon known as cellular plasticity. The aim of this review was to appraise the clinical evidence for the role of cellular plasticity in prostate cancer (PC) bone metastasis. Methods. An electronic search was performed using PubMed for studies that have examined the differential expression of epithelial, mesenchymal, and stem cell markers in human PC bone metastasis tissues. Results. The review included nineteen studies. More than 60% of the studies used ≤20 bone metastasis samples, and there were several sources of heterogeneity between studies. Overall, most stem cell markers analysed, except for CXCR4, were positively expressed in bone metastasis tissues, while the expression of EMT and MET markers was heterogeneous between and within samples. Several EMT and stemness markers that are involved in osteomimicry, such as Notch, Met receptor, and Wnt/β pathway, were highly expressed in bone metastases. Conclusions. Clinical findings support the role of cellular plasticity in PC bone metastasis and suggest that epithelial and mesenchymal states cannot be taken in isolation when targeting PC bone metastasis. The paper also highlights several challenges in the clinical detection of cellular plasticity.

Are androgen receptor variants a substitute for the full-length receptor?

Androgen receptor splice variants (AR-Vs)--which are expressed in castration-resistant prostate cancer (CRPC) cell lines and clinical samples--lack the C-terminal ligand-binding domain and are constitutively active. AR-Vs are, therefore, resistant to traditional androgen deprivation therapy (ADT). AR-Vs are induced by several mechanisms, including ADT, and might contribute to the progression of CRPC and resistance to ADT. AR-Vs could represent a novel therapeutic target for prostate cancer, especially in CRPC.

Epithelial plasticity in prostate cancer: principles and clinical perspectives

Over the past decade, the capacity of cancer cells to oscillate between epithelial and mesenchymal phenotypes, termed epithelial plasticity (EP), has been demonstrated to play a critical role in metastasis. This phenomenon may be particularly important for prostate cancer (PC) progression, since recent studies have revealed interplay between EP and signaling by the androgen receptor (AR) oncoprotein. Moreover, EP appears to play a role in dictating the response to therapies for metastatic PC. This review will evaluate preclinical and clinical evidence for the relevance of EP in PC progression and consider the potential of targeting and measuring EP as a means to treat and manage lethal forms of the disease.

SRC: marker or actor in prostate cancer aggressiveness

A key question for urologic practitioners is whether an apparently organ-confined prostate cancer (PCa) is actually aggressive or not. The dilemma is to specifically identify among all prostate tumors the very aggressive high-grade cancers that will become life-threatening by developing extra-prostatic invasion and metastatic potential and the indolent cancers that will never modify a patient's life expectancy. A choice must be made between several therapeutic options to achieve the optimal personalized management of the disease that causes as little harm as possible to patients. Reliable clinical, biological, or pathological markers that would enable distinctions to be made between aggressive and indolent PCas in routine practice at the time of initial diagnosis are still lacking. The molecular mechanisms that explain why a PCa is aggressive or not are also poorly understood. Among the potential markers and/or actors in PCa aggressiveness, Src and other members of the Src kinase family, are valuable candidates. Activation of Src-dependent intracellular pathways is frequently observed in PCa. Indeed, Src is at the cross-roads of several pathways [including androgen receptor (AR), TGFbeta, Bcl-2, Akt/PTEN or MAPK, and ERK …], and is now known to influence some of the cellular and tissular events that accompany tumor progression: cell proliferation, cell motility, invasion, epithelial-to-mesenchymal transition, resistance to apoptosis, angiogenesis, neuroendocrine differentiation, and metastatic spread. Recent work even suggests that Src could also play a part in PCa initiation in coordination with the AR. The aim of this review is to gather data that explore the links between the Src kinase family and PCa progression and aggressiveness.

Biologic and clinical significance of androgen receptor variants in castration resistant prostate cancer

As prostate cancer (PCa) progresses to the lethal castration resistant and metastatic form, genetic and epigenetic adaptation, clonal selection, and evolution of the tumor microenvironment contribute to the emergence of unique biological characteristics under the selective pressure of external stresses. These stresses include the therapies applied in the clinic or laboratory and the exposures of cancers to hormonal, paracrine, or autocrine stimuli in the context of the tumor micro- and macro-environment. The androgen receptor (AR) is a key gene involved in PCa etiology and oncogenesis, including disease development, progression, response to initial hormonal therapies, and subsequent resistance to hormonal therapies. Alterations in the AR signaling pathway have been observed in certain selection contexts and contribute to the resistance to agents that target hormonal regulation of the AR, including standard androgen deprivation therapy, antiandrogens such as enzalutamide, and androgen synthesis inhibition with abiraterone acetate. One such resistance mechanism is the synthesis of constitutively active AR variants lacking the canonical ligand-binding domain. This review focuses on the etiology, characterization, biological properties, and emerging data contributing to the clinical characteristics of AR variants, and suggests approaches to full-length AR and AR variant biomarker validation, assessment, and systemic targeting in the clinic.