New advances of the androgen receptor in prostate cancer: report from the 1st International Androgen Receptor Symposium.

The androgen receptor (AR) is a crucial player in various aspects of male reproduction and has been associated with the development and progression of prostate cancer (PCa). Therefore, the protein is the linchpin of current PCa therapies. Despite great research efforts, the AR signaling pathway has still not been deciphered, and the emergence of resistance is still the biggest problem in PCa treatment. To discuss the latest developments in AR research, the "1st International Androgen Receptor Symposium" offered a forum for the exchange of clinical and scientific innovations around the role of the AR in prostate cancer (PCa) and to stimulate new collaborative interactions among leading scientists from basic, translational, and clinical research. The symposium included three sessions covering preclinical studies, prognostic and diagnostic biomarkers, and ongoing prostate cancer clinical trials. In addition, a panel discussion about the future direction of androgen deprivation therapy and anti-AR therapy in PCa was conducted. Therefore, the newest insights and developments in therapeutic strategies and biomarkers are discussed in this report.

Identification of genomic drivers for the therapeutic response of Cabozantinib in patients with metastatic renal cell carcinoma.

PURPOSE: Cabozantinib (CAB) as monotherapy or in combination with immune checkpoint inhibitors is used for systemic treatment of metastatic renal cell carcinoma (mRCC). However, little is known about predictors of treatment response to CAB. For this reason, known genomic drivers were examined to identify potential predictors of treatment response with CAB. METHODS: Twenty mRCC patients receiving monotherapy (≥ first-line) with CAB were prospectively included. DNA was extracted from archived primary tumors or metastatic tissue. Targeted DNA sequencing was performed using a gene panel including 328 genes (QIAseq Targeted DNA V3 Panel, Qiagen). The variant evaluation was performed using Varsome. The endpoints were treatment-failure-free-survival (TFFS) to CAB. RESULTS: 26% of patients received systemic RCC treatment as the primary option. Six patients were treated with CAB in first-line (1L) and 12 patients in ≥ 2L. The median follow-up after initiation of systemic treatment was 26.7 months (mo). The PBRM1 (7 alleles), SETD2 (7 alleles), VHL (11 alleles), and CHEK2 (14 alleles) genes were most frequently altered. The median time to TFFS was 10.5 mo (95% confidence interval (CI) 6.2-14.7 mo). There was a longer treatment response to CAB in patients with alterations of the SETD2 gene (SETD2 alteration median TFFS not reached vs. no SETD2 alterations 8.4 mo (95% CI 5.2-11.6 mo); p = 0.024). CONCLUSION: Pathogenic variant genes may indicate treatment response to systemic therapy in mRCC. Patients with alterations of the SETD2 gene show longer responses to CAB treatment.

The Androgen Hormone-Induced Increase in Androgen Receptor Protein Expression Is Caused by the Autoinduction of the Androgen Receptor Translational Activity.

The androgen receptor (AR) plays a central role in prostate, muscle, bone and adipose tissue. Moreover, dysregulated AR activity is a driving force in prostate cancer (PCa) initiation and progression. Consequently, antagonizing AR signalling cascades via antiandrogenic therapy is a crucial treatment option in PCa management. Besides, very high androgen levels also inhibit PCa cells' growth, so this effect could also be applied in PCa therapy. However, on the molecular and cellular level, these mechanisms have hardly been investigated so far. Therefore, the present study describes the effects of varying androgen concentrations on the viability of PCa cells as well as localization, transactivation, and protein stability of the AR. For this purpose, cell viability was determined via WST1 assay. Alterations in AR transactivity were detected by qPCR analysis of AR target genes. A fluorescent AR fusion protein was used to analyse AR localization microscopically. Changes in AR protein expression were detected by Western blot. Our results showed that high androgen concentrations reduce the cell viability in LNCaP and C4-2 cell lines. In addition, androgens have been reported to increase AR transactivity, AR localization, and AR protein expression levels. However, high androgen levels did not reduce these parameters. Furthermore, this study revealed an androgen-induced increase in AR protein synthesis. In conclusion, inhibitory effects on cell viability by high androgen levels are due to AR downstream signalling or non-genomic AR activity. Moreover, hormonal activation of the AR leads to a self-induced stabilization of the receptor, resulting in increased AR activity. Therefore, in clinical use, a therapeutic reduction in androgen levels represents a clinical target and would lead to a decrease in AR activity and, thus, AR-driven PCa progression.

Comprehensive Evaluation of Multiple Approaches Targeting ABCB1 to Resensitize Docetaxel-Resistant Prostate Cancer Cell Lines.

Docetaxel (DTX) is a mainstay in the treatment of metastatic prostate cancer. Failure of DTX therapy is often associated with multidrug resistance caused by overexpression of efflux membrane transporters of the ABC family such as the glycoprotein ABCB1. This study investigated multiple approaches targeting ABCB1 to resensitize DTX-resistant (DTXR) prostate cancer cell lines. In DU145 DTXR and PC-3 DTXR cells as well as age-matched parental controls, the expression of selected ABC transporters was analyzed by quantitative PCR, Western blot, flow cytometry and immunofluorescence. ABCB1 effluxing activity was studied using the fluorescent ABCB1 substrate rhodamine 123. The influence of ABCB1 inhibitors (elacridar, tariquidar), ABCB1-specific siRNA and inhibition of post-translational glycosylation on DTX tolerance was assessed by cell viability and colony formation assays. In DTXR cells, only ABCB1 was highly upregulated, which was accompanied by a strong effluxing activity and additional post-translational glycosylation of ABCB1. Pharmacological inhibition and siRNA-mediated knockdown of ABCB1 completely resensitized DTXR cells to DTX. Inhibition of glycosylation with tunicamycin affected DTX resistance partially in DU145 DTXR cells, which was accompanied by a slight intracellular accumulation and decreased effluxing activity of ABCB1. In conclusion, DTX resistance can be reversed by various strategies with small molecule inhibitors representing the most promising and feasible approach.

Impact of Androgen Receptor Activity on Prostate-Specific Membrane Antigen Expression in Prostate Cancer Cells.

Prostate-specific membrane antigen (PSMA) is an essential molecular regulator of prostate cancer (PCa) progression coded by the FOLH1 gene. The PSMA protein has become an important factor in metastatic PCa diagnosis and radioligand therapy. However, low PSMA expression is suggested to be a resistance mechanism to PSMA-based imaging and therapy. Clinical studies revealed that androgen receptor (AR) inhibition increases PSMA expression. The mechanism has not yet been elucidated. Therefore, this study investigated the effect of activation and inhibition of androgen signaling on PSMA expression levels in vitro and compared these findings with PSMA levels in PCa patients receiving systemic therapy. To this end, LAPC4, LNCaP, and C4-2 PCa cells were treated with various concentrations of the synthetic androgen R1881 and antiandrogens. Changes in FOLH1 mRNA were determined using qPCR. Open access databases were used for ChIP-Seq and tissue expression analysis. Changes in PSMA protein were determined using western blot. For PSMA staining in patients' specimens, immunohistochemistry (IHC) was performed. Results revealed that treatment with the synthetic androgen R1881 led to decreased FOLH1 mRNA and PSMA protein. This effect was partially reversed by antiandrogen treatment. However, AR ChIP-Seq analysis revealed no canonical AR binding sites in the regulatory elements of the FOLH1 gene. IHC analysis indicated that androgen deprivation only resulted in increased PSMA expression in patients with low PSMA levels. The data demonstrate that AR activation and inhibition affects PSMA protein levels via a possible non-canonical mechanism. Moreover, analysis of PCa tissue reveals that low PSMA expression rates may be mandatory to increase PSMA by androgen deprivation.

Interleukin-4 induces a CD44high /CD49bhigh PC3 subpopulation with tumor-initiating characteristics.

Pro- and anti-inflammatory cytokines may influence proliferation, migration, invasion, and other cellular events of prostate cancer (PCa) cells. The hyaluronan receptor CD44, which is regulated by Interleukin (IL)-4, is a prostate basal cell marker. CD44high /CD49bhigh expressing cells have been demonstrated to have tumor-initiating characteristics. Here, we aimed to analyze the effects of long-term IL-4 treatment on CD44/CD49b expression, migration, proliferation, and clonogenic potential of basal-like PCa cells. To this end PC3 cells were treated over 30 passages with 5 ng/mL IL-4 (PC3-IL4) resulting in an increased population of CD44high expressing cells. This was concurrent with a clonal outgrowth of cuboid-shaped cells, with increased size and light absorbance properties. Flow cytometry revealed that the PC3-IL4 CD44high expressing subpopulation corresponds to the CD49bhigh population. Isolation of the PC3-IL4 CD44high /CD49bhigh subpopulation via fluorescence-associated cell sorting showed increased migrative, proliferative, and clonogenic potential compared to the CD44low /CD49blow subpopulation. In conclusion, IL-4 increases a PC3 subpopulation with tumor-initiating characteristics. Thus, IL-4, similar to other cytokines may be a regulator of tumor-initiation and hence, may present a suitable therapy target in combination with current treatment options.

Therapy escape mechanisms in the malignant prostate.

Androgen receptor (AR) is the main target for prostate cancer therapy. Clinical approaches for AR inactivation include chemical castration, inhibition of androgen synthesis and AR antagonists (anti-androgens). However, treatment resistance occurs for which an important number of therapy escape mechanisms have been identified. Herein, we summarise the current knowledge of molecular mechanisms underlying therapy resistance in prostate cancer. Moreover, the tumour escape mechanisms are arranged into the concepts of target modification, bypass signalling, histologic transformation, cancer stem cells and miscellaneous mechanisms. This may help researchers to compare and understand same or similar concepts of therapy resistance in prostate cancer and other cancer types.

Modulation of the Prostate Cancer Resistance Factor Hsp27 by the Chemotherapeutic Drugs Abiraterone, Cabazitaxel, Docetaxel and Enzalutamide.

BACKGROUND/AIM: The cytoprotective heat shock protein 27 (HSP27) acts as a protein chaperone, antioxidant, and apoptosis regulator and is involved in cytoskeletal remodeling in prostate cancer. This study was designed to assess the effect of prostate cancer therapeutics on HSP27 to identify drugs that may benefit from an HSP27 inhibitor combination therapy. MATERIALS AND METHODS: Cell counting was utilized to assess drug treatment efficiency. Changes in protein levels after drug treatment were assessed using western blot analysis. RESULTS: Abiraterone, cabazitaxel, docetaxel and enzalutamide significantly reduced cell proliferation in LNCaP and PC3 cells. Treatment with abiraterone and enzalutamide led to a significant reduction in HSP27 protein levels. In contrast, treatment with cabazitaxel and docetaxel did not change the HSP27 protein levels. CONCLUSION: Treatment with abiraterone and enzalutamide reduces HSP27 protein in an AR-independent manner and thus suppresses HSP27-correlated resistance mechanisms. However, docetaxel and cabazitaxel do not alter HSP27 protein levels, so that taxanes' efficacy may be enhanced by combining them with HSP27-inhibiting drugs.

Utilization of sperm cryopreservation in patients with testicular cancer.

PURPOSE: We assessed factors that affect the utilization of sperm cryopreservation before 2021, when patients covered expenses, and the influence on quality of life. METHODS: Between 2011 and 2021, testicular cancer survivors (TCS) at our clinic completed a questionnaire, including EORTC QLQ-TC26, covering sperm cryopreservation, sociodemographic details, post-treatment births, and artificial insemination. RESULTS: After 5.7 ± 3.0 years, 279 participants (64%) responded to the questionnaire. Among them, 33% (91/279) of testicular cancer survivors chose sperm cryopreservation prior to treatment, with 11% (10/91) using it for insemination. Conversely, 2% (3/188) without cryopreservation reported unfulfilled desire to have children. Univariate analysis showed TCS with cryopreservation were younger (30.6 ± 7.1 (35 (21-59)) vs. 42.4 ± 10.9 (48 (22-81)) years; p = 0.001), had a lower BMI (24.2 ± 3.3 vs. 26.6 ± 4.6 kg/m2; p = 0.009) and a lower Charlson Score (> 3: 36% vs. 60%; p < 0.001). Multivariate analysis revealed older age (≥ 37 years: OR 13.1 (5.5-31.2), p < 0.001) and lower education (middle school or less: OR 3.3 (1.6-6.9), p = 0.001) as independent factors associated with not undergoing cryopreservation. Regarding quality of life, multivariate analysis identified a lower infertility anxiety score (OR 4.3 (2.0-9.0), p < 0.001) and higher age (≥ 44 years: OR 5.4 (2.6-11.3); p < 0.001) as predictors for the absence of prior cryopreservation. CONCLUSIONS: Age and education seem to impact the choice of undergoing paid sperm cryopreservation. Urologists should inform testicular cancer patients about costs and coverage. Importantly, the occurrence of unmet desires for parenthood is minimal among those who forego cryopreservation.

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.

Targeting the glutamine metabolism to suppress cell proliferation in mesenchymal docetaxel-resistant prostate cancer.

Docetaxel (DX) serves as a palliative treatment option for metastatic prostate cancer (PCa). Despite initial remission, acquired DX resistance is inevitable. The mechanisms behind DX resistance have not yet been deciphered, but a mesenchymal phenotype is associated with DX resistance. Mesenchymal phenotypes have been linked to metabolic rewiring, obtaining most ATP production by oxidative phosphorylation (OXPHOS) powered substantially by glutamine (Gln). Likewise, Gln is known to play an essential role in modulating bioenergetic, redox homeostasis and autophagy. Herein, investigations of Gln deprivation on DX-sensitive and -resistant (DR) PCa cells revealed that the DR cell sub-lines were susceptible to Gln deprivation. Mechanistically, Gln deprivation reduced OXPHOS and ATP levels, causing a disturbance in cell cycle progression. Genetic and chemical inhibition of the Gln-metabolism key protein GLS1 could validate the Gln deprivation results, thereby representing a valid therapeutic target. Moreover, immunohistological investigation of GLS1 revealed a high-expressing GLS1 subgroup post-docetaxel failure, exhibiting low overall survival. This subgroup presents an intriguing opportunity for targeted therapy focusing on glutamine metabolism. Thus, these findings highlight a possible clinical rationale for the chemical inhibition of GLS1 as a therapeutic strategy to target mesenchymal DR PCa cells, thereby delaying accelerated tumour progression.

ALDH1A1 drives prostate cancer metastases and radioresistance by interplay with AR- and RAR-dependent transcription.

Rationale: Current therapies for metastatic osseous disease frequently fail to provide a durable treatment response. To date, there are only limited therapeutic options for metastatic prostate cancer, the mechanisms that drive the survival of metastasis-initiating cells are poorly characterized, and reliable prognostic markers are missing. A high aldehyde dehydrogenase (ALDH) activity has been long considered a marker of cancer stem cells (CSC). Our study characterized a differential role of ALDH1A1 and ALDH1A3 genes as regulators of prostate cancer progression and metastatic growth. Methods: By genetic silencing of ALDH1A1 and ALDH1A3 in vitro, in xenografted zebrafish and murine models, and by comparative immunohistochemical analyses of benign, primary tumor, and metastatic specimens from patients with prostate cancer, we demonstrated that ALDH1A1 and ALDH1A3 maintain the CSC phenotype and radioresistance and regulate bone metastasis-initiating cells. We have validated ALDH1A1 and ALDH1A3 as potential biomarkers of clinical outcomes in the independent cohorts of patients with PCa. Furthermore, by RNAseq, chromatin immunoprecipitation (ChIP), and biostatistics analyses, we suggested the molecular mechanisms explaining the role of ALDH1A1 in PCa progression. Results: We found that aldehyde dehydrogenase protein ALDH1A1 positively regulates tumor cell survival in circulation, extravasation, and metastatic dissemination, whereas ALDH1A3 plays the opposite role. ALDH1A1 and ALDH1A3 are differentially expressed in metastatic tumors of patients with prostate cancer, and their expression levels oppositely correlate with clinical outcomes. Prostate cancer progression is associated with the increasing interplay of ALDH1A1 with androgen receptor (AR) and retinoid receptor (RAR) transcriptional programs. Polo-like kinase 3 (PLK3) was identified as a transcriptional target oppositely regulated by ALDH1A1 and ALDH1A3 genes in RAR and AR-dependent manner. PLK3 contributes to the control of prostate cancer cell proliferation, migration, DNA repair, and radioresistance. ALDH1A1 gain in prostate cancer bone metastases is associated with high PLK3 expression. Conclusion: This report provides the first evidence that ALDH1A1 and PLK3 could serve as biomarkers to predict metastatic dissemination and radiotherapy resistance in patients with prostate cancer and could be potential therapeutic targets to eliminate metastasis-initiating and radioresistant tumor cell populations.

PIAS1 is increased in human prostate cancer and enhances proliferation through inhibition of p21.

Prostate cancer development and progression are associated with alterations in expression and function of elements of cytokine networks, some of which can activate multiple signaling pathways. Protein inhibitor of activated signal transducers and activators of transcription (PIAS)1, a regulator of cytokine signaling, may be implicated in the modulation of cellular events during carcinogenesis. This study was designed to investigate the functional significance of PIAS1 in models of human prostate cancer. We demonstrate for the first time that PIAS1 protein expression is significantly higher in malignant areas of clinical prostate cancer specimens than in normal tissues, thus suggesting a growth-promoting role for PIAS1. Expression of PIAS1 was observed in the majority of tested prostate cancer cell lines. In addition, we investigated the mechanism by which PIAS1 might promote prostate cancer and found that down-regulation of PIAS1 leads to decreased proliferation and colony formation ability of prostate cancer cell lines. This decrease correlates with cell cycle arrest in the G0/G1 phase, which is mediated by increased expression of p21(CIP1/WAF1). Furthermore, PIAS1 overexpression positively influences cell cycle progression and thereby stimulates proliferation, which can be mechanistically explained by a decrease in the levels of cellular p21. Taken together, our data reveal an important new role for PIAS1 in the regulation of cell proliferation in prostate cancer.

Epithelial-to-mesenchymal transition leads to docetaxel resistance in prostate cancer and is mediated by reduced expression of miR-200c and miR-205.

Docetaxel is a standard chemotherapy for patients with metastatic prostate cancer. However, the response is rather limited and not all of the patients benefit from this treatment. To uncover key mechanisms of docetaxel insensitivity in prostate cancer, we have established docetaxel-resistant sublines. In this study, we report that docetaxel-resistant cells underwent an epithelial-to-mesenchymal transition during the selection process, leading to diminished E-cadherin levels and up-regulation of mesenchymal markers. Screening for key regulators of an epithelial phenotype revealed a significantly reduced expression of microRNA (miR)-200c and miR-205 in docetaxel-resistant cells. Transfection of either microRNA (miRNA) resulted in re-expression of E-cadherin. Functional assays confirmed reduced adhesive and increased invasive and migratory abilities. Furthermore, we detected an increased subpopulation with stem cell-like properties in resistant cells. Tissue microarray analysis revealed a reduced E-cadherin expression in tumors after neoadjuvant chemotherapy. Low E-cadherin levels could be linked to tumor relapse. The present study uncovers epithelial-to-mesenchymal transition as a hallmark of docetaxel resistance. Therefore, we suggest that this mechanism is at least in part responsible for chemotherapy failure, with implications for the development of novel therapeutics.

Metabolic changes during prostate cancer development and progression.

Metabolic reprogramming has been recognised as a hallmark in solid tumours. Malignant modification of the tumour's bioenergetics provides energy for tumour growth and progression. Otto Warburg first reported these metabolic and biochemical changes in 1927. In prostate cancer (PCa) epithelial cells, the tumour metabolism also changes during development and progress. These alterations are partly driven by the androgen receptor, the key regulator in PCa development, progress, and survival. In contrast to other epithelial cells of different entities, glycolytic metabolism in prostate cells sustains physiological citrate secretion in the normal prostatic epithelium. In the early stages of PCa, citrate is utilised to power oxidative phosphorylation and fuel lipogenesis, enabling tumour growth and progression. In advanced and incurable castration-resistant PCa, a metabolic shift towards choline, amino acid, and glycolytic metabolism fueling tumour growth and progression has been described. Therefore, even if the metabolic changes are not fully understood, the altered metabolism during tumour progression may provide opportunities for novel therapeutic strategies, especially in advanced PCa stages. This review focuses on the main differences in PCa's metabolism during tumourigenesis and progression highlighting glutamine's role in PCa.

Pleiotropic Devitalization of Renal Cancer Cells by Non-Invasive Physical Plasma: Characterization of Molecular and Cellular Efficacy.

Renal cell carcinoma (RCC) is the third most common urological tumor and has an extremely poor prognosis after metastasis has occurred. Therapeutic options are highly restricted, primarily due to resistance to classical chemotherapeutics. The development of new, innovative therapeutic procedures is thus of great urgency. In the present study, the influence of non-invasive physical plasma (NIPP) on malignant and non-malignant renal cells is characterized. The biological efficacy of NIPP has been demonstrated in malignant renal cell lines (786-O, Caki-1) and non-malignant primary human renal epithelial cells (HREpC). The cell responses that were experimentally examined were cell growth (cell number determination, calculation of growth rate and doubling time), cell motility (scratch assay, invasiveness assay), membrane integrity (uptake of fluorescent dye, ATP release), and induction of apoptosis (TUNEL assay, caspase-3/7 assay, comet assay). A single NIPP treatment of the malignant cells significantly inhibited cell proliferation, invasiveness, and metastasis. This treatment has been attributed to the disruption of membrane functionality and the induction of apoptotic mechanisms. Comparison of NIPP sensitivity of malignant 786-O and Caki-1 cells with non-malignant HREpC cells showed significant differences. Our results suggest that renal cancer cells are significantly more sensitive to NIPP than non-malignant renal cells. Treatment with NIPP could represent a promising innovative option for the therapy of RCC and might supplement established treatment procedures. Of high clinical relevance would be the chemo-sensitizing properties of NIPP, which could potentially allow a combination of NIPP treatment with low-dose chemotherapy.

PD-L1 mRNA Detection in Immunohistochemically Negative Patients: A Complementary Method for a Better Treatment Selection?

BACKGROUND/AIM: PD-L1 inhibitors have been approved for cisplatin-ineligible urothelial cancer patients relapsing after radical cystectomy. A prerequisite for therapy is a positive PD-L1 expression in the tumor tissue, whereas no options are available for patients with negative PD-L1 status. However, studies revealed that many PD-L1-negative patients also responded to PD-L1 therapy. This study investigated the feasibility of PD-L1 mRNA complementary RNA in situ hybridization (RNAish) analysis to detect PD-L1-responders independent of PD-L1 protein status. MATERIALS AND METHODS: Immunohistochemistry and RNA in situ hybridization were used to assess PD-L1 protein and mRNA in radical cystectomy tissue from patients with advanced and metastasized urothelial cancer. RESULTS: In this study, PD-L1 protein and mRNA were detected in ≥90% of the examined tissue. Positive PD-L1 mRNA expression (≥1%) on TC and IC could be evaluated in 77% and 31% of the cases, respectively. Moreover, scatterplot analysis revealed a PD-L1 mRNA positive and PD-L1 protein negative subpopulation. According to the CPS score, positive PD-L1 protein expression could be evaluated in 88% and positive PD-L1 mRNA expression in 71% of the cases. Scatterplot analysis of the CPS scores revealed a CPS protein negative but CPS mRNA positive small subpopulation. CONCLUSION: The feasibility of RNAish on formalin-fixed tissue could be proven. Moreover, complementary PD-L1 RNAish identified a sub-population of PD-L1 protein-negative and PD-L1 mRNA-positive patients, which may benefit from PD-L1 therapy.

Physiological and Genetically Engineered Expression Modulation Methods Do Not Affect Cellular Levels of the Heat Shock Protein HSP60 in Prostate Cancer Cells.

BACKGROUND/AIM: Heat shock proteins (HSP) play a crucial role in the cellular responses during stressful conditions. In addition, HSP are involved in the regulation of a variety of important signaling pathways and processes as well as many pathological conditions, including cancer. In prostate cancer (PC), HSP60 is associated with poor differentiation and prognostic clinical parameters, such as high Gleason score, initial serum prostate-specific antigen levels, and lower cancer-specific survival. In this study, we investigated the regulation of HSP60 protein in PC. MATERIALS AND METHODS: LNCaP or PC3 cells were treated with androgens or transfected with vectors containing microRNA-1 (miR-1), HSP60, HSP60-specific short-hairpin RNA (shHSP60), or a miR-1 inhibitor. The change in HSP60 protein levels was examined using Western blot. RESULTS: Treatment of PC cells with androgens did not alter the HSP60 protein levels. Modulation of miR-1 levels in LNCaP cells also did not affect the HSP60 protein. Furthermore, HSP60 levels could not be modified by overexpression or short hairpin RNA. CONCLUSION: It was found that neither physiological factors, such as androgens and the HSP60-specific miR-1, nor overexpression and knockdown systems could influence the HSP60 protein levels. These results suggest an essential role of HSP60 in PC cells, as its protein expression status is regulated very precisely.

Influence of Androgen Deprivation Therapy on the PD-L1 Expression and Immune Activity in Prostate Cancer Tissue.

Immune checkpoint inhibitors have become a promising new therapy for cancer treatment. However, due to prostate cancer's high heterogeneity and immune-suppressive tumour microenvironment, clinical trials with immune checkpoint inhibitors for prostate cancer resulted in low or no response. This descriptive and retrospective study investigates the influence of androgen deprivation therapy (ADT) on PD-L1 expression and CD8+ T-cell tumour infiltration and activity in primary prostate cancer tissue. Therefore, immunohistochemistry was used to assess PD-L1, CD8+ T-cell, and the immune activation marker Granzyme B (GrB) in PCa tissue before and under ADT. In line with previous studies, few prostate cancer tissues showed PD-L1 expression and CD8+ T-cell infiltration. However, PD-L1 expression levels on tumour cells or infiltrating immune cells above 5% generated an immune-suppressive tumour microenvironment harbouring hypofunctional CD8+ T-cells. Moreover, analysis of a longitudinal patient cohort before and under ADT revealed that ADT increased hypofunctional CD8+ T cells in the tumour area suggesting a tumour immune milieu optimal for targeting with immunotherapy.

Acquired resistance to irradiation or docetaxel is not associated with cross-resistance to cisplatin in prostate cancer cell lines.

PURPOSE: Platinum chemotherapy can be considered to treat metastatic castration-resistant prostate cancer (mCRPC) with features of neuroendocrine differentiation. However, platinum compounds are generally only applied after the failure of multiple prior-line treatment options. This study investigated whether acquired resistance against ionizing radiation or docetaxel chemotherapy-two commonly applied treatment modalities in prostate cancer-influences the cisplatin (CDDP) tolerance in mCRPC cell line models. METHODS: Age-matched parental as well as radio- or docetaxel-resistant DU145 and PC-3 cell lines were treated with CDDP and their sensitivity was assessed by measurements of growth rates, viability, apoptosis, metabolic activity and colony formation ability. RESULTS: The data suggest that docetaxel resistance does not influence CDDP tolerance in all tested docetaxel-resistant cell lines. Radio-resistance was associated with sensitization to CDDP in PC-3, but not in DU145 cells. In general, DU145 cells tolerated higher CDDP concentrations than PC-3 cells regardless of acquired resistances. Furthermore, non-age-matched treatment-naïve PC-3 cells exhibited significantly different CDDP tolerances. CONCLUSION: Like patients, different mCRPC cell lines exhibit significant variability regarding CDDP tolerance. The presented in vitro data suggest that previous radiation treatment may be associated with a moderate sensitization to CDDP in an isogenic and age-matched setting. Therefore, previous radiotherapy or docetaxel chemotherapy might be no contraindication against initiation of platinum chemotherapy in selected mCRPC patients.