NanoLuc Binary Technology as a methodological approach: an important new tool for studying the localization of androgen receptor and androgen receptor splice variant V7 homo and heterodimers

BACKGROUND

The androgen/androgen receptor (AR)-signaling axis plays a central role in prostate cancer (PCa). Upon androgen-binding the AR dimerizes with another AR, and translocates into the nucleus where the AR-dimer activates/inactivates androgen-dependent genes. Consequently, treatments for PCa are commonly based on androgen deprivation therapy (ADT). The clinical benefits of ADT are only transitory and most tumors develop mechanisms allowing the AR to bypass its need for physiological levels of circulating androgens. Clinical failure of ADT is often characterized by the synthesis of a constitutively active AR splice variant, termed AR-V7. AR-V7 mRNA expression is considered as a resistance mechanism following ADT. AR-V7 no longer needs androgenic stimuli for nuclear entry and/or dimerization.

METHODS

Our goal was to mechanistically decipher the interaction between full-length AR (AR-FL) and AR-V7 in AR-null HEK-293 cells using the NanoLuc Binary Technology under androgen stimulation and deprivation conditions.

RESULTS

Our data point toward a hypothesis that AR-FL/AR-FL homodimers form in the cytoplasm, whereas AR-V7/AR-V7 homodimers localize in the nucleus. However, after androgen stimulation, all the AR-FL/AR-FL, AR-FL/AR-V7 and AR-V7/AR-V7 dimers were localized in the nucleus.

CONCLUSIONS

We showed that AR-FL and AR-V7 form heterodimers that localize to the nucleus, whereas AR-V7/AR-V7 dimers were found to localize in the absence of androgens in the nucleus.

Androgen Receptor-Interacting Proteins in Prostate Cancer Development and Therapy Resistance

Endocrine therapy for prostate cancer is based on the use of drugs that diminish androgen concentration and androgen receptor (AR) signaling inhibitors and is limited by the functional consequences of AR point mutations and increased expression of constitutively active receptors. Many coactivators (>280) interact with different AR regions. Most studies have determined the expression of coactivators and their effects in the presence of increasing concentrations of androgen or the antiandrogen enzalutamide. The p160 group of coactivators (SRC-1, SRC-2, and SRC-3) is highly expressed in prostate cancer and contributes to ligand-dependent activation of the receptor in models that represent therapy-sensitive and therapy-resistant cell lines. The transcriptional coactivators p300 and CREB-binding protein (CBP) are implicated in the regulation of a large number of cellular events, such as proliferation, apoptosis, migration, and invasion. AR coactivators also may predict biochemical and clinical recurrence. The AR coactivator expression, which is enhanced in enzalutamide resistance, includes growth regulating estrogen receptor binding 1 (GREB1) and GATA-binding protein 2 (GATA2). Several coactivators also activate AR-unrelated signaling pathways, such as those of insulin-like growth factors, which inhibit apoptosis in cancer cells. They are expressed in multiple models of resistance to therapy and can be targeted by various inhibitors in vitro and in vivo. The role of the glucocorticoid receptor in endocrine therapy-resistant prostate cancer has been documented previously. Specific coactivators may interact with the glucocorticoid receptor, thus contributing to therapy failure.

Cholinergic signaling via muscarinic M1 receptor confers resistance to docetaxel in prostate cancer

Docetaxel is the most commonly used chemotherapy for advanced prostate cancer (PC), including castration-resistant disease (CRPC), but the eventual development of docetaxel resistance constitutes a major clinical challenge. Here, we demonstrate activation of the cholinergic muscarinic M1 receptor (CHRM1) in CRPC cells upon acquiring resistance to docetaxel, which is manifested in tumor tissues from PC patients post- vs. pre-docetaxel. Genetic and pharmacological inactivation of CHRM1 restores the efficacy of docetaxel in resistant cells. Mechanistically, CHRM1, via its first and third extracellular loops, interacts with the SEMA domain of cMET and forms a heteroreceptor complex with cMET, stimulating a downstream mitogen-activated protein polykinase program to confer docetaxel resistance. Dicyclomine, a clinically available CHRM1-selective antagonist, reverts resistance and restricts the growth of multiple docetaxel-resistant CRPC cell lines and patient-derived xenografts. Our study reveals a CHRM1-dictated mechanism for docetaxel resistance and identifies a CHRM1-targeted combinatorial strategy for overcoming docetaxel resistance in PC.

Glucocorticoid treatment influences prostate cancer cell growth and the tumor microenvironment via altered glucocorticoid receptor signaling in prostate fibroblasts

Despite significant therapeutic advances in recent years, treatment of metastatic prostate cancer (PCa) remains palliative, owing to the inevitable occurrence of drug resistance. There is increasing evidence that epithelial glucocorticoid receptor (GR) signaling and changes in the tumor-microenvironment (TME) play important roles in this process. Since glucocorticoids (GCs) are used as concomitant medications in the course of PCa treatment, it is essential to investigate the impact of GCs on stromal GR signaling in the TME. Therefore, general GR mRNA and protein expression was assessed in radical prostatectomy specimens and metastatic lesions. Elevated stromal GR signaling after GC treatment resulted in altered GR-target gene, soluble protein expression, and in a morphology change of immortalized and primary isolated cancer-associated fibroblasts (CAFs). Subsequently, these changes affected proliferation, colony formation, and 3D-spheroid growth of multiple epithelial PCa cell models. Altered expression of extra-cellular matrix (ECM) and adhesion-related proteins led to an ECM remodeling. Notably, androgen receptor pathway inhibitor treatments did not affect CAF viability. Our findings demonstrate that GC-mediated elevated GR signaling has a major impact on the CAF secretome and the ECM architecture. GC-treated fibroblasts significantly influence epithelial tumor cell growth and must be considered in future therapeutic strategies.

MiRNA-mRNA integrative analysis reveals epigenetically regulated and prognostic miR-103a with a role in migration and invasion of carboplatin-resistant ovarian cancer cells that acquired mesenchymal-like phenotype

BACKGROUND

DNA methylation, histone modifications, and miRNAs affect ovarian cancer (OC) progression and therapy response.

PURPOSE

Identification of epigenetically downregulated miRNAs in drug-resistant OC cell lines with a possible role in drug resistance and/or drug-induced mesenchymal-like phenotype.

METHODS

MiRNA profiling was performed on parental and carboplatin-resistant OC cells, MES-OV and MES-OV CBP. RT-qPCR validation, epigenetic modulation and other CBP-resistant OC cell lines were used to select miRNAs of interest. The integration of miRNA-predicted target genes and differentially expressed genes (DEGs), pathway and functional analysis were used for forecasting their biological role. Data mining was performed to determine their possible prognostic and predictive values.

RESULTS

MiRNA profiling revealed 48 downregulated miRNAs in OC cells whose drug sensitivity and metastatic potential were impacted by epigenetic modulators. Of the fourteen selected, nine were validated as changed, and seven of these restored their expression upon treatment with epigenetic inhibitors. Only three had similar expression patterns in other OC cell lines. MiRNA-mRNA integrative analysis resulted in 56 target DEGs. Pathway analysis revealed that these genes are involved in cell adhesion, migration, and invasion. The functional analysis confirmed the role of miR-103a-3p, miR-17-5p and miR-107 in cell invasion, while data mining showed their prognostic and predictive values. Only miR-103a-3p was epigenetically regulated at the constitutive level.

CONCLUSION

High throughput miRNA and cDNA profiling coupled with pathway analysis and data mining delivered evidence for miRNAs which can be epigenetically regulated in drug-resistant, mesenchymal-like OC cells as possible markers to combat therapy-induced short overall survival and tumor metastatic potential.

The Oncogenic Protein Kinase/ATPase RIOK1 Is Up-Regulated via the c-myc/E2F Transcription Factor Axis in Prostate Cancer

The atypical protein kinase/ATPase RIO kinase (RIOK)-1 is involved in pre-40S ribosomal subunit production, cell-cycle progression, and protein arginine N-methyltransferase 5 methylosome substrate recruitment. RIOK1 overexpression is a characteristic of several malignancies and is correlated with cancer stage, therapy resistance, poor patient survival, and other prognostic factors. However, its role in prostate cancer (PCa) is unknown. In this study, the expression, regulation, and therapeutic potential of RIOK1 in PCa were examined. RIOK1 mRNA and protein expression were elevated in PCa tissue samples and correlated with proliferative and protein homeostasis-related pathways. RIOK1 was identified as a downstream target gene of the c-myc/E2F transcription factors. Proliferation of PCa cells was significantly reduced with RIOK1 knockdown and overexpression of the dominant-negative RIOK1-D324A mutant. Biochemical inhibition of RIOK1 with toyocamycin led to strong antiproliferative effects in androgen receptor-negative and -positive PCa cell lines with EC50 values of 3.5 to 8.8 nmol/L. Rapid decreases in RIOK1 protein expression and total rRNA content, and a shift in the 28S/18S rRNA ratio, were found with toyocamycin treatment. Apoptosis was induced with toyocamycin treatment at a level similar to that with the chemotherapeutic drug docetaxel used in clinical practice. In summary, the current study indicates that RIOK1 is a part of the MYC oncogene network, and as such, could be considered for future treatment of patients with PCa.

Mass Spectrometry-Based Biomarkers to Detect Prostate Cancer: A Multicentric Study Based on Non-Invasive Urine Collection without Prior Digital Rectal Examination

(1) Background: Prostate cancer (PCa) is the most frequently diagnosed cancer in men. Wide application of prostate specific antigen test has historically led to over-treatment, starting from excessive biopsies. Risk calculators based on molecular and clinical variables can be of value to determine the risk of PCa and as such, reduce unnecessary and invasive biopsies. Urinary molecular studies have been mostly focusing on sampling after initial intervention (digital rectal examination and/or prostate massage). (2) Methods: Building on previous proteomics studies, in this manuscript, we aimed at developing a biomarker model for PCa detection based on urine sampling without prior intervention. Capillary electrophoresis coupled to mass spectrometry was applied to acquire proteomics profiles from 970 patients from two different clinical centers. (3) Results: A case-control comparison was performed in a training set of 413 patients and 181 significant peptides were subsequently combined by a support vector machine algorithm. Independent validation was initially performed in 272 negative for PCa and 138 biopsy-confirmed PCa, resulting in an AUC of 0.81, outperforming current standards, while a second validation phase included 147 PCa patients. (4) Conclusions: This multi-dimensional biomarker model holds promise to improve the current diagnosis of PCa, by guiding invasive biopsies.

Multicentric validation of diagnostic tests based on BC-116 and BC-106 urine peptide biomarkers for bladder cancer in two prospective cohorts of patients

BACKGROUND

Non-invasive urine-based biomarkers can potentially improve current diagnostic and monitoring protocols for bladder cancer (BC). Here we assess the performance of earlier published biomarker panels for BC detection (BC-116) and monitoring of recurrence (BC-106) in combination with cytology, in two prospectively collected patient cohorts.

METHODS

Of the 602 patients screened for BC, 551 were found eligible. For the primary setting, 73 patients diagnosed with primary BC (n = 27) and benign urological disorders, including patients with macroscopic haematuria, cystitis and/or nephrolithiasis (n = 46) were included. In total, 478 patients under surveillance were additionally considered (83 BC recurrences; 395 negative for recurrence). Urine samples were analysed with capillary electrophoresis-mass spectrometry. The biomarker score was estimated via support vector machine-based software.

RESULTS

Validation of BC-116 biomarker panel resulted in 89% sensitivity and 67% specificity (AUCBC-116 = 0.82). A diagnostic score based on cytology and BC-116 resulted in good (AUCNom116 = 0.85) but not significantly better performance (P = 0.5672). A diagnostic score including BC-106 and cytology was evaluated (AUCNom106 = 0.82), significantly outperforming both cytology (AUCcyt = 0.72; P = 0.0022) and BC-106 (AUCBC-106 = 0.67; P = 0.0012).

CONCLUSIONS

BC-116 biomarker panel is a useful test for detecting primary BC. BC-106 classifier integrated with cytology showing >95% negative predictive value, might be useful for decreasing the number of cystoscopies during surveillance.

Toll-Like Receptor 3 Overexpression Induces Invasion of Prostate Cancer Cells, whereas Its Activation Triggers Apoptosis

Toll-like receptor 3 (TLR3) is an endosomal receptor expressed in several immune and epithelial cells. Recent studies have highlighted its expression also in solid tumors, including prostate cancer (PCa), and described its role mainly in the proinflammatory response and induction of apoptosis. It has been found up-regulated in some castration-resistant prostate cancers. However, the role of TLR3 in prostate cancer progression remains largely unknown. We have experimentally demonstrated that exogenous TLR3 activation in PCa cell lines leads to the significant induction of secretion of the cytokines IL-6, IL-8, and interferon-β, depending on the model and chemoresistance status. Transcriptomic analysis of TLR3-overexpressing cells revealed a functional program that is enriched for genes involved in the regulation of cell motility, migration, and tumor invasiveness. Increased motility, migration, and invasion in TLR3-overexpressing cell line were confirmed by several in vitro assays and using an orthotopic prostate xenograft model in vivo. Furthermore, TLR3-ligand induced apoptosis via cleavage of caspase-3/7 and poly (ADP-ribose) polymerase, predominantly in TLR3-overexpressing cells. We conclude that TLR3 may be involved in prostate cancer progression and metastasis; however, it might also represent an Achilles heel of PCa, which can be exploited for targeted therapy.

Inhibition of Cyclin-Dependent Kinase 8/Cyclin-Dependent Kinase 19 Suppresses Its Pro-Oncogenic Effects in Prostate Cancer

Progression of prostate cancer (PCa) is characterized by metastasis and castration resistance after response to androgen deprivation. Therapeutic options are limited, causing high morbidity and lethality. Recent work reported pro-oncogenic implications of the Mediator subunits cyclin-dependent kinase (CDK) 8 and 19 for the progression of PCa. The current study explored the underlying molecular mechanisms of CDK8/CDK19 and tested effects of novel CDK8/CDK19 inhibitors. PC3, DU145, LNCaP, and androgen-independent LNCaP Abl were used for in vitro experiments. Two inhibitors and CDK19 overexpression were used to modify CDK8/CDK19 activity. MTT assay, propidium iodide staining, wound healing assay, Boyden chamber assay, and adhesion assay were used to investigate cell viability, cell cycle, migration, and adhesion, respectively. Peptide-kinase screen using the PamGene platform was conducted to identify phosphorylated targets. Combining CDK8/CDK19 inhibitors with anti-androgens led to synergistic antiproliferative effects and sensitized androgen-independent cells to bicalutamide. CDK8/CDK19 inhibition resulted in reduced migration and increased collagen I-dependent adhesion. Phosphorylation of multiple peptides linked to cancer progression was identified to be dependent on CDK8/CDK19. In summary, this study substantially supports recent findings on CDK8/CDK19 in PCa progression. These findings contribute to a better understanding of underlying pro-oncogenic effects, which is needed to develop CDK8/CDK19 as a therapeutic target in PCa.

KMT2C methyltransferase domain regulated INK4A expression suppresses prostate cancer metastasis

BACKGROUND

Frequent truncation mutations of the histone lysine N-methyltransferase KMT2C have been detected by whole exome sequencing studies in various cancers, including malignancies of the prostate. However, the biological consequences of these alterations in prostate cancer have not yet been elucidated.

METHODS

To investigate the functional effects of these mutations, we deleted the C-terminal catalytic core motif of Kmt2c specifically in mouse prostate epithelium. We analysed the effect of Kmt2c SET domain deletion in a Pten-deficient PCa mouse model in vivo and of truncation mutations of KMT2C in a large number of prostate cancer patients.

RESULTS

We show here for the first time that impaired KMT2C methyltransferase activity drives proliferation and PIN formation and, when combined with loss of the tumour suppressor PTEN, triggers loss of senescence, metastatic dissemination and dramatically reduces life expectancy. In Kmt2c-mutated tumours we show enrichment of proliferative MYC gene signatures and loss of expression of the cell cycle repressor p16^INK4A. In addition, we observe a striking reduction in disease-free survival of patients with KMT2C-mutated prostate cancer.

CONCLUSIONS

We identified truncating events of KMT2C as drivers of proliferation and PIN formation. Loss of PTEN and KMT2C in prostate cancer results in loss of senescence, metastatic dissemination and reduced life expectancy. Our data demonstrate the prognostic significance of KMT2C mutation status in prostate cancer patients. Inhibition of the MYC signalling axis may be a viable treatment option for patients with KMT2C truncations and therefore poor prognosis.

Artesunate Inhibits the Growth Behavior of Docetaxel-Resistant Prostate Cancer Cells

Novel therapeutic strategies are urgently needed for advanced metastatic prostate cancer (PCa). Phytochemicals used in Traditional Chinese Medicine seem to exhibit tumor suppressive properties. Therefore, the therapeutic potential of artesunate (ART) on the progressive growth of therapy-sensitive (parental) and docetaxel (DX)-resistant PCa cells was investigated. Parental and DX-resistant PCa cell lines DU145, PC3, and LNCaP were incubated with artesunate (ART) [1-100 µM]. ART-untreated and ‘non-cancerous’ cells served as controls. Cell growth, proliferation, cell cycle progression, cell death and the expression of involved proteins were evaluated. ART, dose- and time-dependently, significantly restricted cell growth and proliferation of parental and DX-resistant PCa cells, but not of ‘normal, non-cancerous’ cells. ART-induced growth and proliferation inhibition was accompanied by G0/G1 phase arrest and down-regulation of cell cycle activating proteins in all DX-resistant PCa cells and parental LNCaP. In the parental and DX-resistant PC3 and LNCaP cell lines, ART also promoted apoptotic cell death. Ferroptosis was exclusively induced by ART in parental and DX-resistant DU145 cells by increasing reactive oxygen species (ROS). The anti-cancer activity displayed by ART took effect in all three PCa cell lines, but through different mechanisms of action. Thus, in advanced PCa, ART may hold promise as a complementary treatment together with conventional therapy.

Validation of diagnostic nomograms based on CE-MS urinary biomarkers to detect clinically significant prostate cancer

PURPOSE

Prostate cancer (PCa) is one of the most common cancers and one of the leading causes of death worldwide. Thus, one major issue in PCa research is to accurately distinguish between indolent and clinically significant (csPCa) to reduce overdiagnosis and overtreatment. In this study, we aim to validate the usefulness of diagnostic nomograms (DN) to detect csPCa, based on previously published urinary biomarkers.

METHODS

Capillary electrophoresis/mass spectrometry was employed to validate a previously published biomarker model based on 19 urinary peptides specific for csPCa. Added value of the 19-biomarker (BM) model was assessed in diagnostic nomograms including prostate-specific antigen (PSA), PSA density and the risk calculator from the European Randomized Study of Screening. For this purpose, urine samples from 147 PCa patients were collected prior to prostate biopsy and before performing digital rectal examination (DRE). The 19-BM score was estimated via a support vector machine-based software based on the pre-defined cutoff criterion of - 0.07. DNs were subsequently developed to assess added value of integrative diagnostics.

RESULTS

Independent validation of the 19-BM resulted in an 87% sensitivity and 65% specificity, with an AUC of 0.81, outperforming PSA (AUC _PSA: 0.64), PSA density (AUC _PSAD: 0.64) and ERSPC-3/4 risk calculator (0.67). Integration of 19-BM with the rest clinical variables into distinct DN, resulted in improved (AUC range: 0.82-0.88) but not significantly better performances over 19-BM alone.

CONCLUSION

19-BM alone or upon integration with clinical variables into DN, might be useful for detecting csPCa by decreasing the number of biopsies.

Manuscript Title: Analysis of tripartite motif (TRIM) family gene expression in prostate cancer bone metastases

Tripartite motif (TRIM) family proteins are post-translational protein modifiers with E3-ubiquitin ligase activity, thereby involved in various biological processes. The molecular mechanisms driving prostate cancer (PCa) bone metastasis (BM) are incompletely understood, and targetable genetic alterations are lacking in the majority of cases. Therefore, we aimed to explore the expression and potential functional relevance of 71 TRIM members in bone metastatic PCa. We performed transcriptome analysis of all human TRIM family members and 770 cancer-related genes in 29 localized PCa and 30 PCa BM using Nanostring. KEGG, STRING and Ubibrowser were used for further bioinformatic gene correlation and pathway enrichment analyses. Compared to localized tumors, six TRIMs are under-expressed while nine TRIMs are over-expressed in BM. The differentially expressed TRIM proteins are linked to TNF-, TGFβ-, PI3K/AKT- and HIF-1-signaling, and to features such as proteoglycans, platelet activation, adhesion and ECM-interaction based on correlation to cancer-related genes. The identification of TRIM-specific E3-ligase-substrates revealed insight into functional connections to oncogenes, tumor suppressors and cancer-related pathways including androgen receptor- and TGFβ signaling, cell cycle regulation and splicing. In summary, this is the first study that comprehensively and systematically characterizes the expression of all TRIM members in PCa BM. Our results describe post-translational protein modification as an important regulatory mechanism of oncogenes, tumor suppressors, and pathway molecules in PCa progression. Therefore, this study may provide evidence for novel therapeutic targets, in particular for the treatment or prevention of BM.

IL-4 Counteracts the Cytotoxic Effects of Peripheral Blood Mononuclear Cells on Hormone-sensitive Prostate Cancer Cells

BACKGROUND/AIM

Proinflammatory cytokines play an essential role in the development and progression of prostate cancer (PCa). Especially interleukine (IL-)6 is involved in the development of aggressive PCa. Peripheral blood mononuclear cells (PBMC) have been reported to interact with cancer cells and subsequently lead to increased production of pro-inflammatory cytokines. However, the role of anti-nflammatory cytokines, such as IL-4 is still largely unexplored in prostate cancer. In the present study, we investigated the effects of IL-4 on PBMC co-cultured with PCa cells.

MATERIALS AND METHODS

PBMC were co-culured with the PCa cell lines LNCaP and LNCaP-IL6+. To avoid cell-cell contact, cancer and immune cells were separated using cell culture inserts with a 0.4 μm pore size membrane. Cell growth was assessed using the [3-(4, 5-dimethylthiazol-2-yl)-2, 5 diphenyl tetrazolium bromide] (MTT) assay. Cytokine levels were measured using a BD™Cytometric Bead Array.

RESULTS

Cell viability of LNCaP cells decreased massively when cells were co-cultured with PBMC. Pre-incubation with IL-4 could partly rescue the observed effect of cell viability of LNCaP cells co-cultured with PBMC. In contrast, cell viability of the LNCaP-IL6+ cell line was not affected when co-cultured with PBMC.

CONCLUSION

IL-4 counteracts the cytotoxic effects of PBMC on hormone-sensitive LNCaP cells and is involved in the immune escape and development of aggressive phenotypes of PCa.

Response to Androgens and Androgen Receptor Antagonists in the Presence of Cytokines in Prostate Cancer

Simple Summary

Prostate cancer is the most frequently diagnosed non-cutaneous tumor in men in the Western world. Therapy for non-organ confined prostate cancer includes anti-androgens such as bicalutamide, enzalutamide and darolutamide. The androgen receptor is expressed during tumor initiation and progression. Androgen receptor could be activated by interleukins, which are produced by blood cells and adjacent stroma. These cytokines may affect response of tumor cells to anti-androgenic drugs, which are commonly used in prostate cancer therapy. There are several experimental studies showing an effect of anti-cytokine therapies in prostate cancer. However, the clinical translation is limited and more clinical trials are needed to improve action of anti-androgens in prostate cells which are stimulated by cytokines.

Abstract

Non-steroidal anti-androgens have a major role in the treatment of non-localized prostate cancer. Interleukins are involved in the regulation of many cellular functions in prostate cancer and also modify cellular response to anti-androgens. A specific role of selected IL is presented in this review. IL-8 is a cytokine expressed in prostate cancer tissue and microenvironment and promotes proliferation and androgen receptor-mediated transcription. In contrast, IL-1 displays negative effects on expression of androgen receptor and its target genes. A subgroup of prostate cancers show neuroendocrine differentiation, which may be in part stimulated by androgen ablation. A similar effect was observed after treatment of cells with IL-10. Another cytokine which is implicated in regulation of androgenic response is IL-23, secreted by myeloid cells. Most studies on androgens and IL were carried out with IL-6, which acts through the signal transducer and activator of the transcription (STAT) factor pathway. IL-6 is implicated in resistance to enzalutamide. Activation of the STAT-3 pathway is associated with increased cellular stemness. IL-6 activation of the androgen receptor in some prostate cancers is associated with increased growth in vitro and in vivo. Molecules such as galiellalactone or niclosamide have an inhibitory effect on both androgen receptor and STAT-3 pathways.

MYC-Mediated Ribosomal Gene Expression Sensitizes Enzalutamide-resistant Prostate Cancer Cells to EP300/CREBBP Inhibitors

Patients with advanced prostate cancer are frequently treated with the antiandrogen enzalutamide. However, resistance eventually develops in virtually all patients, and various mechanisms have been associated with this process. The histone acetyltransferases EP300 and CREBBP are involved in regulation of cellular events in advanced prostate cancer. This study investigated the role of EP300/CREBBP inhibitors in enzalutamide-resistant prostate cancer. EP300/CREBBP inhibitors led to the same inhibition of androgen receptor activity in enzalutamide-resistant and -sensitive cells. However, enzalutamide-resistant cells were more sensitive to these inhibitors in viability assays. As indicated by the RNA-sequencing-based pathway analysis, genes related to the ribosome and MYC activity were significantly altered upon EP300/CREBBP inhibitor treatment. EP300/CREBBP inhibitors led to the down-regulation of ribosomal proteins RPL36 and RPL29. High-level ribosomal proteins amplifications and MYC amplifications were observed in castration-resistant prostate cancer samples of the publicly available Stand Up to Cancer data set. An inhibitor of RNA polymerase I-mediated transcription was used to evaluate the functional implications of these findings. The enzalutamide-resistant cell lines were more sensitive to this treatment. In addition, the migration rate of enzalutamide-resistant cells was strongly inhibited by this treatment. Taken together, the current data show that EP300/CREBBP inhibitors affect the MYC/ribosomal protein axis in enzalutamide-resistant cells and may have promising therapeutic implications.

miRNA as Regulators of Prostate Carcinogenesis and Endocrine and Chemoresistance

More therapy options are available for advanced prostate cancer, including novel inhibitors of androgen synthesis, anti-androgens, chemotherapeutics and targeted therapies. Although patients ´ survival has been improved, management of castration therapy-resistant prostate cancer remains a challenge. Regulation of cellular events in cancer by small non-coding miRNAs is, therefore, an area of special interest. Overexpression of selected miRNA may lead to androgen independence and prostate cancer progression. miRNA may be considered also a biomarker in patients with prostate cancer. In contrast, diminished expression of tumor-suppressive miRNA in prostate cancer leads to enhanced proliferation, reduced apoptosis, increased migration, invasion and epithelial- to-mesenchymal transition. miRNA may be directly involved in the regulation of chemosensitivity in prostate cancer. Experimental overexpression of selected miRNA in chemoresistant prostate cancer leads to the inhibition of cellular stemness and epithelial-to-mesenchymal transition. Reduction of tumor-suppressive miRNA may also lead to hyperactivity of signaling pathways such as that of the epidermal growth factor receptor and mitogen-activated protein kinase. Although considerable progress on miRNA research in prostate cancer has been achieved, therapeutic effects could be improved on the basis of the development of novel delivery methods.

The "COVID-19 Pandemic Gap" and Its Influence on Oncologic Outcomes of Bladder Cancer

Simple Summary

The COVID-19 pandemic has had a major impact on the entire healthcare system, resulting in severe restrictions of nonemergency clinical services, as well as in the clinical practice of uro-oncology. We performed a retrospective analysis to evaluate outcomes of the COVID-19 pandemic resulting from delayed diagnosis, staging, and treatment of bladder cancer. We showed that the COVID-19 pandemic led to a deferred oncological diagnosis and treatment of bladder cancer. More attention is required to avoid adverse outcomes, with increased rates of advanced and aggressive tumors in patients with primary bladder cancer. Moreover, timely treatment is compulsory in those patients.

Abstract

Coronavirus-19 (COVID-19)-induced effects on deferred diagnosis and treatment of bladder cancer (BC) patients are currently not clarified. The aim of this study was to evaluate outcomes of the COVID-19 pandemic by considering its effects on tumor stage and grade, and to create feasible clinical triage decisions. A retrospective single-center analysis of all patients who underwent diagnostic and surgical procedures due to BC, during January 2019 and December 2020, was performed. Due to COVID-19 lockdowns, significantly fewer (diagnostic and therapeutic) endoscopic procedures were performed in the first 6 months of 2020 compared to 2019 (p = 0.002). In patients with a primary diagnosis of BC, a significant increase of high-grade tumors (p < 0.001), as well as advanced tumor stages (p = 0.014), were noticed during 2020 in comparison to 2019. On the contrary, patients with recurrent BC undergoing risk-adapted surveillance, depending on previous tumor histology, showed no adverse outcomes regarding tumor stage and grade when comparing the pre COVID-19 era with 2020. Thus, more awareness in clinical urologic practice is mandatory to avoid adverse consequences, with increased rates of advanced and aggressive tumors in patients with primary BC. In recurrent BC, an individual risk stratification in order to avoid worse outcomes during the COVID-19 pandemic seems to be justified.

Lynch Syndrome: Its Impact on Urothelial Carcinoma

Lynch syndrome, known as hereditary nonpolyposis colorectal cancer (HNPCC), is an autosomal-dominant familial cancer syndrome with an increased risk for urothelial cancer (UC). Mismatch repair (MMR) deficiency, due to pathogenic variants in MLH1, MSH2, MSH6, and PMS2, and microsatellite instability, are known for development of Lynch syndrome (LS) associated carcinogenesis. UC is the third most common cancer type in LS-associated tumors. The diversity of germline variants in the affected MMR genes and their following subsequent function loss might be responsible for the variation in cancer risk, suggesting an increased risk of developing UC in MSH2 mutation carriers. In this review, we will focus on LS-associated UC of the upper urinary tract (UUT) and bladder, their germline profiles, and outcomes compared to sporadic UC, the impact of genetic testing, as well as urological follow-up strategies in LS. In addition, we present a case of metastatic LS-associated UC of the UUT and bladder, achieving complete response during checkpoint inhibition since more than 2 years.

Thyroid and androgen receptor signaling are antagonized by μ-Crystallin in prostate cancer

Androgen deprivation therapy (ADT) remains a key approach in the treatment of prostate cancer (PCa). However, PCa inevitably relapses and becomes ADT resistant. Besides androgens, there is evidence that thyroid hormone thyroxine (T4) and its active form 3,5,3'-triiodo-L-thyronine (T3) are involved in the progression of PCa. Epidemiologic evidences show a higher incidence of PCa in men with elevated thyroid hormone levels. The thyroid hormone binding protein μ-Crystallin (CRYM) mediates intracellular thyroid hormone action by sequestering T3 and blocks its binding to cognate receptors (TRα/TRβ) in target tissues. We show in our study that low CRYM expression levels in PCa patients are associated with early biochemical recurrence and poor prognosis. Moreover, we found a disease stage-specific expression of CRYM in PCa. CRYM counteracted thyroid and androgen signaling and blocked intracellular choline uptake. CRYM inversely correlated with [18F]fluoromethylcholine (FMC) levels in positron emission tomography/magnetic resonance imaging of PCa patients. Our data suggest CRYM as a novel antagonist of T3- and androgen-mediated signaling in PCa. The role of CRYM could therefore be an essential control mechanism for the prevention of aggressive PCa growth.

Assessment of STAT5 as a potential therapy target in enzalutamide-resistant prostate cancer

Despite enzalutamide's efficacy in delaying the progression of metastatic castration-resistant prostate cancer (CRPC), resistance to this anti-androgen inevitably occurs. Several studies have revealed that the signal transducer and activator of transcription (STAT) 5 plays a role in tumour progression and development of drug resistance such as enzalutamide. Data mining revealed heterogeneous expression of STAT5 in enzalutamide-treated mCRPC patients and enzalutamide-resistant prostate cancer (PCa). Isobologram analysis revealed that the STAT5 inhibitor pimozide combined with enzalutamide has? additive and synergistic inhibitory effects on cell viability in the used models. Functional analysis with siRNA-mediated STAT5 knockdown yielded divergent results. The LNCaP-derived cell line MR49F could be resensitised to enzalutamide by siRNA-mediated STAT5b-knock-down. In contrast, neither STAT5a nor STAT5b knockdown resensitised enzalutamide-resistant LAPC4-EnzaR cells to enzalutamide. In conclusion, our results indicate that STAT5 may be a possible target in a subgroup of enzalutamide-resistant PCa. However, based on the data presented here, a general role of STAT5 in enzalutamide-resistance and its potential as a therapeutic target could not be shown.

The CHK1 inhibitor MU380 significantly increases the sensitivity of human docetaxel-resistant prostate cancer cells to gemcitabine through the induction of mitotic catastrophe

As treatment options for patients with incurable metastatic castration-resistant prostate cancer (mCRPC) are considerably limited, novel effective therapeutic options are needed. Checkpoint kinase 1 (CHK1) is a highly conserved protein kinase implicated in the DNA damage response (DDR) pathway that prevents the accumulation of DNA damage and controls regular genome duplication. CHK1 has been associated with prostate cancer (PCa) induction, progression, and lethality; hence, CHK1 inhibitors SCH900776 (also known as MK-8776) and the more effective SCH900776 analog MU380 may have clinical applications in the therapy of PCa. Synergistic induction of DNA damage with CHK1 inhibition represents a promising therapeutic approach that has been tested in many types of malignancies, but not in chemoresistant mCRPC. Here, we report that such therapeutic approach may be exploited using the synergistic action of the antimetabolite gemcitabine (GEM) and CHK1 inhibitors SCH900776 and MU380 in docetaxel-resistant (DR) mCRPC. Given the results, both CHK1 inhibitors significantly potentiated the sensitivity to GEM in a panel of chemo-naïve and matched DR PCa cell lines under 2D conditions. MU380 exhibited a stronger synergistic effect with GEM than clinical candidate SCH900776. MU380 alone or in combination with GEM significantly reduced spheroid size and increased apoptosis in all patient-derived xenograft 3D cultures, with a higher impact in DR models. Combined treatment induced premature mitosis from G1 phase resulting in the mitotic catastrophe as a prestage of apoptosis. Finally, treatment by MU380 alone, or in combination with GEM, significantly inhibited tumor growth of both PC339-DOC and PC346C-DOC xenograft models in mice. Taken together, our data suggest that metabolically robust and selective CHK1 inhibitor MU380 can bypass docetaxel resistance and improve the effectiveness of GEM in DR mCRPC models. This approach might allow for dose reduction of GEM and thereby minimize undesired toxicity and may represent a therapeutic option for patients with incurable DR mCRPC.

ZEB1: A Critical Regulator of Cell Plasticity, DNA Damage Response, and Therapy Resistance

The predominant way in which conventional chemotherapy kills rapidly proliferating cancer cells is the induction of DNA damage. However, chemoresistance remains the main obstacle to therapy effectivity. An increasing number of studies suggest that epithelial-to-mesenchymal transition (EMT) represents a critical process affecting the sensitivity of cancer cells to chemotherapy. Zinc finger E-box binding homeobox 1 (ZEB1) is a prime element of a network of transcription factors controlling EMT and has been identified as an important molecule in the regulation of DNA damage, cancer cell differentiation, and metastasis. Recent studies have considered upregulation of ZEB1 as a potential modulator of chemoresistance. It has been hypothesized that cancer cells undergoing EMT acquire unique properties that resemble those of cancer stem cells (CSCs). These stem-like cells manifest enhanced DNA damage response (DDR) and DNA repair capacity, self-renewal, or chemoresistance. In contrast, functional experiments have shown that ZEB1 induces chemoresistance regardless of whether other EMT-related changes occur. ZEB1 has also been identified as an important regulator of DDR by the formation of a ZEB1/p300/PCAF complex and direct interaction with ATM kinase, which has been linked to radioresistance. Moreover, ATM can directly phosphorylate ZEB1 and enhance its stability. Downregulation of ZEB1 has also been shown to reduce the abundance of CHK1, an effector kinase of DDR activated by ATR, and to induce its ubiquitin-dependent degradation. In this perspective, we focus on the role of ZEB1 in the regulation of DDR and describe the mechanisms of ZEB1-dependent chemoresistance.

p300 is upregulated by docetaxel and is a target in chemoresistant prostate cancer

Administration of the microtubule inhibitor docetaxel is a common treatment for metastatic castration-resistant prostate cancer (mCRPC) and results in prolonged patient overall survival. Usually, after a short period of time chemotherapy resistance emerges and there is urgent need to find new therapeutic targets to overcome therapy resistance. The lysine-acetyltransferase p300 has been correlated to prostate cancer (PCa) progression. Here, we aimed to clarify a possible function of p300 in chemotherapy resistance and verify p300 as a target in chemoresistant PCa. Immunohistochemistry staining of tissue samples revealed significantly higher p300 protein expression in patients who received docetaxel as a neoadjuvant therapy compared to control patients. Elevated p300 expression was confirmed by analysis of publicly available patient data, where significantly higher p300 mRNA expression was found in tissue of mCRPC tumors of docetaxel-treated patients. Consistently, docetaxel-resistant PCa cells showed increased p300 protein expression compared to docetaxel-sensitive counterparts. Docetaxel treatment of PCa cells for 72 h resulted in elevated p300 expression. shRNA-mediated p300 knockdown did not alter colony formation efficiency in docetaxel-sensitive cells, but significantly reduced clonogenic potential of docetaxel-resistant cells. Downregulation of p300 in docetaxel-resistant cells also impaired cell migration and invasion. Taken together, we showed that p300 is upregulated by docetaxel, and our findings suggest that p300 is a possible co-target in treatment of chemoresistant PCa.

The stem cell inhibitor salinomycin decreases colony formation potential and tumor-initiating population in docetaxel-sensitive and docetaxel-resistant prostate cancer cells

BACKGROUND

Prostate cancer (PCa) is one of the most frequently diagnosed tumors in men. In general, therapies for localized PCa are curative. However, treatment of advanced PCa is considered palliative since development of therapy resistance occurs rapidly. It has been shown that tumor-initiating cells are likely involved in therapy resistance. They are not eliminated by conventional therapies and thereby lead to tumor progression and relapse. The aim of this study was to evaluate the effects of the known stem cell inhibitor salinomycin on this critical subpopulation of cells.

METHODS

Expression of the cell surface markers CD24 and CD44 was assessed by immunofluorescence and fluorescence-activated cell sorting. Colony formation efficiency and classification of colony types with varying tumor-initiating potential (holoclones, meroclones, and paraclones) were analyzed in an automated way by the newly developed CATCH-colonies software in the absence or presence of salinomycin.

RESULTS

Automated high-resolution colony formation analysis consistently identified the various colony types in a broad range of PCa cell lines. Serial clonogenic assays confirmed that holoclones show the highest colony formation potential and maintain their tumor-initiating capacity over multiple rounds. Furthermore, holoclones showed high expression of CD44, while CD24 was not expressed in these clones, thus representing the well-described tumor-initiating CD24^- /CD44^high population. Salinomycin decreased the CD24^- /CD44^high population in both docetaxel-sensitive PC3 and docetaxel-resistant (DR) PC3-DR. Moreover, treatment of PC3, DU145, PC3-DR, and DU145-DR with salinomycin led to a significant reduction in the colony formation potential by targeting the colonies with high tumor-initiating potential.

CONCLUSIONS

Taken together, we demonstrated that salinomycin specifically targets the tumor-initiating cell population in docetaxel-sensitive and docetaxel-resistant PCa cells and may represent a potential therapeutic approach for the treatment of advanced PCa.

Amplification of 7p12 Is Associated with Pathologic Nonresponse to Neoadjuvant Chemotherapy in Muscle-Invasive Bladder Cancer

Pathologic downstaging (pDS) to neoadjuvant chemotherapy (NAC) is one of the most important predictors of survival in muscle-invasive bladder cancer (MIBC). The use of NAC is limited as pDS is only achieved in 30% to 40% of cases and predictive biomarkers are still lacking. We performed a comprehensive immunomolecular biomarker analysis to characterize the role of immune cells and inhibitory checkpoints, genome-wide frequencies of copy number alterations, mutational signatures in whole exome, and tumor mutational burden in predicting NAC response. Our retrospective study included 23 primary MIBC patients who underwent NAC, followed by radical cystectomy. pDS to NAC was a significant prognostic factor for better recurrence-free survival (P < 0.001), with a median time to recurrence of 41.2 versus 5.5 months in nonresponders. DNA damage repair alterations were noticed in 38.1% (n = 8), confirming a positive correlation with high tumor mutational burden (P = 0.007). Chromosomal 7p12 amplification, including the genes HUS1, EGFR, ABCA13, and IKZF1, predicted nonresponse in patients with a sensitivity, a negative predictive value, and a specificity of 71.4%, 87.5%, and 100%, respectively. Total count of CD3⁺ T cells/mm² tumor was a significant predictor of NAC response. In conclusion, 7p12 amplification may predict nonresponse to NAC and worse survival in MIBC. Multicenter, prospective trials with sufficient statistical power may further fortify these findings.

Abstract 1020: p300 and CBP targeting in castration therapy resistant prostate cancer

p300 and CBP interact with transcription factors and other proteins via their histone acetyltransferase domain (HAT) and a bromodomain (Bd). In prostate cancer, p300 and CBP act as oncogenes and are commonly upregulated. p300 and CBP are valid targets for therapy due to their function as androgen receptor (AR) coactivators and involvement in castration resistance. Revealing downstream pathways and their function in cancer cell proliferation and resistance should further identify potential novel therapeutic targets. The effect of the p300/CBP HAT inhibitor C646 and the Bd inhibitor ICBP-112 on viability was tested. To this end several human PCa cell lines with different AR expression levels and resistance status were used. The resistant cells were derived from DUCaP, LAPC4 and LNCaP cells chronically treated with Enzalutamide (DUCaP ENZA, LAPC4 ENZA and LNCaP ABL ENZA). Resistance was verified by viability assay. Regulation of AR downstream targets was studied by qRT-PCR and Western blot. Gene expression in the different DUCaP and LNCaP sublines after inhibitor treatment was analyzed with RNAseq. Both inhibitors exhibited IC50 values on viability at micromolar concentrations with a significantly lesser effect on androgen-insensitive PC3 cells compared to AR sensitive cells. Significantly increased sensitivity to inhibitors was observed in enzalutamide-resistant DUCaP ENZA, LAPC4 ENZA and LNCaP ABL ENZA cell lines relative to parental cells: respectively 1.83- (*), 2- (*) and 2.7-fold (*) for C646 and not significant, 1.8- (p&lt;0.1) and 1.56-fold (*) for ICBP-112. Moreover, ICBP-112 treatment of DUCaP cells significantly reduced expression of the AR target genes FKBP5, PSA and TMPRSS2 0.6- (**), 0.57- (**) and 0.37-fold (***) respectively. Similar results were obtained with DUCaP ENZA cells 0.46- (*), 0.45- (*) and 0.57-fold (ns) for FKBP5, PSA and TMPRSS2, respectively. Whilst less pronounced, this regulation was also observed at the protein level. Similar results were obtained with C646. RNAseq results suggest multiple changes in sublines after chronic enzalutamide treatment in DUCaP and LNCaP cells. Inhibition of p300 and CBP reduced androgen-, myc- and parts of an EMT-signature, which are likely involved in the development of enzalutamide resistance. Taken together, C646 and ICBP-112 are effective inhibitors of AR dependent PCa. Furthermore, differences between cell lines suggest that the AR background and other factors influence the inhibitor effectivity. A significantly increased effect of the HAT and Bd inhibitors in CRPC suggests an important role for p300/CBP in CRPC.

Citation Format: Tobias Furlan, Natalie Sampson, Frédéric R. Santer, Zoran Culig. p300 and CBP targeting in castration therapy resistant prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1020.

Epithelial mesenchymal transition and resistance in endocrine-related cancers

Epithelial to mesencyhmal transition (EMT) has a central role in tumor metastasis and progression. EMT is regulated by several growth factors and pro-inflammatory cytokines. The most important role in this regulation could be attributed to transforming growth factor-β (TGF-β). In breast cancer, TGF-β effect on EMT could be potentiated by Fos-related antigen, oncogene HER2, epidermal growth factor, or mitogen-activated protein kinase kinase 5 - extracellular-regulated kinase signaling. Several microRNAs in breast cancer have a considerable role either in potentiation or in suppression of EMT thus acting as oncogenic or tumor suppressive modulators. At present, possibilities to target EMT are discussed but the results of clinical translation are still limited. In prostate cancer, many cellular events are regulated by androgenic hormones. Different experimental results on androgenic stimulation or inhibition of EMT have been reported in the literature. Thus, a possibility that androgen ablation therapy leads to EMT thus facilitating tumor progression has to be discussed. Novel therapy agents, such as the anti-diabetic drug metformin or selective estrogen receptor modulator ormeloxifene were used in pre-clinical studies to inhibit EMT in prostate cancer. Taken together, the results of pre-clinical and clinical studies in breast cancer may be helpful in the process of drug development and identify potential risk during the early stage of that process.

Centrosomal Proteins in Urothelial Tumors: New Pathways in Disease Pathogenesis

This commentary highlights the article by Li et al that identified the centrosomal protein 72 as a biomarker for prognosis of urothelial cancer.

Pathophysiology of Benign Prostatic Hyperplasia and Benign Prostatic Enlargement: A Mini-Review

Benign prostatic hyperplasia (BPH), benign prostatic enlargement (BPE) and lower urinary tract symptoms (LUTS) belong to the most frequent diseases in ageing men. Beyond the 6th decade of life, more than 30% of men suffer from moderate to severe LUTS requiring intervention. The pathophysiology of BPH/BPE is still incompletely understood. The dominant role of the androgen system and the androgen receptor is well defined. Androgen receptors are expressed in BPH tissue in which they are activated by the potent androgen dihydrotestosterone. Synthesis of dihydrotestosterone is under control of the 5α-reductase enzyme, activity of which is antagonized by finasteride and dutasteride. More recently, the impact of prostatic inflammation and metabolic parameters particularly for the development of BPE and LUTS has increasingly been recognized. A better understanding of the pathophysiology is a prerequisite for the development of novel, more effective medical treatment options.

Movember GAP1 PDX project: An international collection of serially transplantable prostate cancer patient-derived xenograft (PDX) models

BACKGROUND

While it has been challenging to establish prostate cancer patient-derived xenografts (PDXs), with a take rate of 10-40% and long latency time, multiple groups throughout the world have developed methods for the successful establishment of serially transplantable human prostate cancer PDXs using a variety of immune deficient mice. In 2014, the Movember Foundation launched a Global Action Plan 1 (GAP1) project to support an international collaborative prostate cancer PDX program involving eleven groups. Between these Movember consortium members, a total of 98 authenticated human prostate cancer PDXs were available for characterization. Eighty three of these were derived directly from patient material, and 15 were derived as variants of patient-derived material via serial passage in androgen deprived hosts. A major goal of the Movember GAP1 PDX project was to provide the prostate cancer research community with a summary of both the basic characteristics of the 98 available authenticated serially transplantable human prostate cancer PDX models and the appropriate contact information for collaborations. Herein, we report a summary of these PDX models.

METHODS

PDX models were established in immunocompromised mice via subcutaneous or subrenal-capsule implantation. Dual-label species (ie, human vs mouse) specific centromere and telomere Fluorescence In Situ Hybridization (FISH) and immuno-histochemical (IHC) staining of tissue microarrays (TMAs) containing replicates of the PDX models were used for characterization of expression of a number of phenotypic markers important for prostate cancer including AR (assessed by IHC and FISH), Ki67, vimentin, RB1, P-Akt, chromogranin A (CgA), p53, ERG, PTEN, PSMA, and epithelial cytokeratins.

RESULTS

Within this series of PDX models, the full spectrum of clinical disease stages is represented, including androgen-sensitive and castration-resistant primary and metastatic prostate adenocarcinomas as well as prostate carcinomas with neuroendocrine differentiation. The annotated clinical characteristics of these PDXs were correlated with their marker expression profile.

CONCLUSION

Our results demonstrate the clinical relevance of this series of PDXs as a platform for both basic science studies and therapeutic discovery/drug development. The present report provides the prostate cancer community with a summary of the basic characteristics and a contact information for collaborations using these models.

The STAT3 Inhibitor Galiellalactone Reduces IL6-Mediated AR Activity in Benign and Malignant Prostate Models

IL6/STAT3 signaling is associated with endocrine therapy resistance in prostate cancer, but therapies targeting this pathway in prostate cancer were unsuccessful in clinical trials so far. The mechanistic explanation for this phenomenon is currently unclear; however, IL6 has pleiotropic effects on a number of signaling pathways, including the androgen receptor (AR). Therefore, we investigated IL6-mediated AR activation in prostate cancer cell lines and ex vivo primary prostate tissue cultures in order to gain a better understanding on how to inhibit this process for future clinical trials. IL6 significantly increased androgen-dependent AR activity in LNCaP cells but importantly did not influence AR activity at castrate androgen levels. To identify the underlying mechanism, we investigated several signaling pathways but only found IL6-dependent changes in STAT3 signaling. Biochemical inhibition of STAT3 with the small-molecule inhibitor galiellalactone significantly reduced AR activity in several prostate and breast cancer cell lines. We confirmed the efficacy of galiellalactone in primary tissue slice cultures from radical prostatectomy samples. Galiellalactone significantly reduced the expression of the AR target genes PSA (P < 0.001), TMPRSS2 (P < 0.001), and FKBP5 (P = 0.003) in benign tissue cultures (n = 24). However, a high heterogeneity in the response of the malignant samples was discovered, and only a subset of tissue samples (4 out of 10) had decreased PSA expression upon galiellalactone treatment. Taken together, this finding demonstrates that targeting the IL6/STAT3 pathway with galiellalactone is a viable option to decrease AR activity in prostate tissue that may be applied in a personalized medicine approach.

Systems Oncology: Bridging Pancreatic and Castrate Resistant Prostate Cancer

Large investments by pharmaceutical companies in the development of new antineoplastic drugs have not been resulting in adequate advances of new therapies. Despite the introduction of new methods, technologies, translational medicine and bioinformatics, the usage of collected knowledge is unsatisfactory. In this paper, using examples of pancreatic ductal adenocarcinoma (PaC) and castrate-resistant prostate cancer (CRPC), we proposed a concept showing that, in order to improve applicability of current knowledge in oncology, the re-clustering of clinical and scientific data is crucial. Such an approach, based on systems oncology, would include bridging of data on biomarkers and pathways between different cancer types. Proposed concept would introduce a new matrix, which enables combining of already approved therapies between cancer types. Paper provides a (a) detailed analysis of similarities in mechanisms of etiology and progression between PaC and CRPC, (b) diabetes as common hallmark of both cancer types and (c) knowledge gaps and directions of future investigations. Proposed horizontal and vertical matrix in cancer profiling has potency to improve current antineoplastic therapy efficacy. Systems biology map using Systems Biology Graphical Notation Language is used for summarizing complex interactions and similarities of mechanisms in biology of PaC and CRPC.

Correction Alternative mechanisms of miR-34a regulation in cancer

The PDF and HTML versions of the article have been updated to include the Creative Commons Attribution 4.0 International License information.

Oncolytic activity of the rhabdovirus VSV-GP against prostate cancer

Oncolytic viruses, including the oncolytic rhabdovirus VSV-GP tested here, selectively infect and kill cancer cells and are a promising new therapeutic modality. Our aim was to study the efficacy of VSV-GP, a vesicular stomatitis virus carrying the glycoprotein of lymphocytic choriomeningitis virus, against prostate cancer, for which current treatment options still fail to cure metastatic disease. VSV-GP was found to infect 6 of 7 prostate cancer cell lines with great efficacy. However, susceptibility was reduced in one cell line with low virus receptor expression and in 3 cell lines after interferon alpha treatment. Four cell lines had developed resistance to interferon type I at different levels of the interferon signaling pathway, resulting in a deficient antiviral response. In prostate cancer mouse models, long-term remission was achieved upon intratumoral and, remarkably, also upon intravenous treatment of subcutaneous tumors and bone metastases. These promising efficacy data demonstrate that treatment of prostate cancer with VSV-GP is feasible and safe in preclinical models and encourage further preclinical and clinical development of VSV-GP for systemic treatment of metastatic prostate cancer.

Abstract 2001: Transcriptional integrator p300 in human prostate tumor-initiating cells

Introduction

p300 is a well-known coactivator of the androgen receptor (AR) and has been shown to play an important role in prostate cancer (PCa). The expression of p300 has been correlated to tumor volume and PCa progression. Therefore, we hypothesize that p300 may play an important role in tumor-initiating cells and therapy resistance. Due to its multifunctional role p300 may serve as a promising new therapeutic target for treatment of PCa. Ultimately, it is our aim to find new innovative therapeutic targets for castration resistant PCa.

Material & Methods

The tumor-initiating capacity of the AR-negative PCa cell lines PC3 and Du145, as well as primary prostate epithelial cells was characterized by seeding a limiting number of cells per flask. Colony formation efficiency, colony type and detailed morphological information about each colony were determined by an automated pipeline that we have developed. Stable cell lines with doxycycline inducible p300 sh RNAs were generated by lentiviral transduction. Knockdown of p300 was verified by Western Blot and reduced p300 activity was confirmed by measuring histone h3 acetylation.

Results

In concordance with the literature we identified three colony types (holo-, mero- and paraclones) in PC3 and Du145 cell lines as well as primary PCa cells. Serial clonogenic assays confirmed in both cell lines that holoclones show the highest colony formation potential and maintain their tumor-initiating capacity over numerous rounds. In PC3 we detected 10% and in Du145 30% holoclones. Under optimal growth conditions p300 was detected in all colony types, however no differences in protein expression of p300 as well as on mRNA level were observed. Knockdown of p300 did not alter colony formation efficiency or the relative distribution of colony types.

Conclusion

Taken together, we confirmed the presence of tumor-initiating holoclones in PCa cell lines and primary prostate epithelial cells and established stable cell lines with inducible knockdown of p300. In contrast to several other types of malignancies, p300 has no specific role in regulation of stemness in our PCa models at the tested conditions. As a next step we will determine the effects of p300 knockdown during chemotherapy and radiation therapy to evaluate if p300 depletion may enhance the treatment efficacy and which role p300 plays in therapy resistance.

Citation Format: Martina Gruber, Florian Handle, Zoran Culig. Transcriptional integrator p300 in human prostate tumor-initiating cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2001.

Olaparib is effective in combination with, and as maintenance therapy after, first-line endocrine therapy in prostate cancer cells

A number of prostate cancer (PCa)‐specific genomic aberrations (denominated BRCAness genes) have been discovered implicating sensitivity to PARP inhibition within the concept of synthetic lethality. Recent clinical studies show favorable results for the PARP inhibitor olaparib used as single agent for treatment of metastatic castration‐resistant PCa. Using 2D and 3D cell culture models mimicking the different treatment and progression stages of PCa, we evaluated a potential use for olaparib in combination with first‐line endocrine treatments, androgen deprivation, and complete androgen blockade, and as a maintenance therapy following on from endocrine therapy. We demonstrate that the LNCaP cell line, possessing multiple aberrations in BRCAness genes, is sensitive to olaparib. Additive effects of olaparib combined with endocrine treatments in LNCaP are noted. In contrast, we find that the TMPRSS2:ERG fusion‐positive cell lines VCaP and DuCaP do not show signs of synthetic lethality, but are sensitive to cytotoxic effects caused by olaparib. In consequence, additive effects of olaparib with endocrine therapy were not observable in these cell lines, showing the need for synthetic lethality in combination treatment regimens. Additionally, we show that PCa cells remain sensitive to olaparib treatment after initial androgen deprivation implicating a possible use of olaparib as maintenance therapy. In sum, our preclinical data recommend olaparib as a synthetic lethal treatment option in combination or sequenced to first‐line endocrine therapy for PCa patients with diagnosed BRCAness.

Interleukin-6 and prostate cancer: Current developments and unsolved questions

Interleukin (IL)-6 is a pro-inflammatory cytokine that is expressed in prostate tumors and in the stromal tumor micro-enviroment. It is known to regulate proliferation, apoptosis, angiogenesis, and differentiation. The signaling pathway of Janus kinase and signal transducer and activator of transcription (STAT)3, which is activated by IL-6, is in the focus of scientific investigations for improved treatment approaches. Different effects of IL-6 and/or STAT3 on tumor cell growth have been observed in human and murine prostate cancer (PCa) models. Experimental therapies have been proposed in order to block the IL-6/STAT3 signaling pathway. In this context, the anti-IL-6 antibody siltuximab (CNTO 328) has been demonstrated to inhibit growth of prostate tumors in vitro and in vivo and delays progression towards castration resistance. However, clinically, the anti-IL-6 antibody was not successful as a monotherapy in phase II studies in patients with metastatic PCa. IL-6 is implicated in regulation of cellular stemness by increasing phosphorylation of STAT3. The cytokine has also a role in development of resistance to the non-steroidal anti-androgen enzalutamide. Endogenous inhibitors of IL-6 are suppressors of cytokine signaling and protein inhibitors of activated STAT. Although they inhibit signal transduction through STAT3, they may also exhibit anti-apoptotic effects. On the basis of complexity of IL-6 action in PCa, an individualized approach is needed to identify patients who will benefit from anti-IL-6 therapy in combination with standard treatments.

Critical role of androgen receptor level in prostate cancer cell resistance to new generation antiandrogen enzalutamide

Enzalutamide is an androgen receptor (AR) inhibitor approved for therapy of metastatic castration resistant prostate cancer. However, clinical application revealed that 30 to 40% of patients acquire resistance after a short period of treatment. Currently, the molecular mechanisms underlying such resistances are not completely understood, partly due to a lack of model systems. In the present study we established three different cellular models of enzalutamide resistance including a cell line with wild type AR (LAPC4), DuCaP cells which overexpress wild-type AR, as well as a cell which has been adapted to long term androgen ablation (LNCaP Abl) and harbors the AR T878A mutation. After 10 months of cultivation, sustained growth in the presence of enzalutamide was achieved. When compared to controls, resistant cells exhibit significantly decreased sensitivity to enzalutamide as measured with ³[H]thymidine incorporation and WST assay. Moreover, these cell models exhibit partly re-activated AR signaling despite presence of enzalutamide. In addition, we show that enzalutamide resistant cells are insensitive to bicalutamide but retain considerable sensitivity to abiraterone. Mechanistically, enzalutamide resistance was accompanied by increased AR and AR-V7 mRNA and protein expression as well as AR gene amplification, while no additional AR mutations have been identified.