Castration-resistant Patients Research Articles

Exploring the tumor genomic landscape of aggressive prostate cancer by whole-genome sequencing of tissue or liquid biopsies.

Treatment resistance remains a major issue in aggressive prostate cancer (PC), and novel genomic biomarkers may guide better treatment selection. Circulating tumor DNA (ctDNA) can provide minimally invasive information about tumor genomes, but the genomic landscape of aggressive PC based on whole-genome sequencing (WGS) of ctDNA remains incompletely characterized. Thus, we here performed WGS of tumor tissue (n = 31) or plasma ctDNA (n = 10) from a total of 41 aggressive PC patients, including 11 hormone-naïve, 15 hormone-sensitive, and 15 castration-resistant patients. Across all variant types, we found progressively more altered tumor genomic profiles in later stages of aggressive PC. The potential driver genes most frequently affected by single-nucleotide variants or insertions/deletions included the known PC-related genes TP53, CDK12, and PTEN and the novel genes COL13A1, KCNH3, and SENP3. Etiologically, aggressive PC was associated with age-related and DNA repair-related mutational signatures. Copy number variants most frequently affected 14q11.2 and 8p21.2, where no well-recognized PC-related genes are located, and also frequently affected regions near the known PC-related genes MYC, AR, TP53, PTEN, and BRCA1. Structural variants most frequently involved not only the known PC-related genes TMPRSS2 and ERG but also the less extensively studied gene in this context, PTPRD. Finally, clinically actionable variants were detected throughout all stages of aggressive PC and in both plasma and tissue samples, emphasizing the potential clinical applicability of WGS of minimally invasive plasma samples. Overall, our study highlights the feasibility of using liquid biopsies for comprehensive genomic characterization as an alternative to tissue biopsies in advanced/aggressive PC.

Abstract CT233: Serum thymidine kinase 1 levels as a predictive marker for castration resistance in metastatic prostate cancer

Abstract Introduction Thymidine kinase 1 (TK1) is an enzyme associated with the cell division cycle; its levels increase during the S-phase of the cell cycle and decrease during the M-phase. In cancer TK1 release is increased both by increased cell proliferation and cell death. Thus, serum concentration of TK1 reflects the tumor volume, proliferation rate, and extent of cell death. Serum Thymidine Kinase 1 (sTK1) enzyme has been used as a prognostic, predictive, and monitoring biomarker in leukemia, Hodgkin's and non-Hodgkin's lymphomas. Additionally, sTK1 enzyme levels have been elevated in breast cancer and prostate cancer. This study evaluated whether sTK1 predicts the risk of castration resistance in patients with metastatic prostate cancer undergoing androgen deprivation therapy (ADT). Materials and Methods sTK1 levels was measured in men diagnosed with metastatic prostate cancer at 3 time points; before the initiation of ADT, 6 months after the start of treatment, and within 6 months before the development of castration resistance. Samples at study visits of ESTO2 trial, which compares atorvastatin to placebo in combination with ADT. The trial intervention was blinded at analysis. Cox regression modeling was used to assess whether sTK1 values predict the risk of castration resistance. sTK1 was analyzed both as continuous and categorical variable, stratified by median value 0.12 ng/ml. The time from the initiation of ADT to the formation of castration resistance, death, or a general index date (May 31, 2023) was used as the time-metric. Results The study included serum samples from 70 patients, of which 23 had developed castration resistance by May 31,2023. The median follow-up time was 13 months. The sTK1 value measured before ADT initiation did not predict the risk of castration resistance (HR 0.91, 95% CI 0.62-1.35). However, sTK1 at 6 months after the initiation of ADT or up to a maximum of 6 months before formation of castration resistance did predict the risk (HR 1.5, 95% CI 1.07-2.1 and HR 1.79, 95% CI 1.16-2.76, respectively). sTK1 predicted the risk at both measurement points also when analyzed as categorical variable. sTK1 was predictive only among men with metastatic disease; sTK1 no longer predicted the risk of castration resistance who started ADT for biochemically recurrent, non-metastatic disease. Conclusions Our findings suggest that sTK1 value can be used to predict the risk of progression to castration resistance during ADT in metastatic prostate cancer. However, these findings need validation from larger datasets. Citation Format: Aino Siltari, Paavo Raittinen, Jarno Riikonen, Juha Koskimäki, Tomi Pakarainen, Mikael Anttinen, Otto Ettala, Teuvo Tammela, Stig Linder, Teemu J. Murtola. Serum thymidine kinase 1 levels as a predictive marker for castration resistance in metastatic prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr CT233.

11-Ketotestosterone and time to castration resistance in patients with recurrent non-metastatic prostate cancer receiving androgen deprivation therapy.

209 Background: The contribution of 11-oxygenated androgens to disease progression in men receiving androgen deprivation therapy (ADT) for recurrent non-metastatic prostate cancer (PCa) remains unresolved. We hypothesized that evaluating circulating levels of 11-oxygenated androgens, such as the potent androgen receptor (AR) agonist 11-ketotestosterone (11KT), could serve as a potential predictor for the onset of castration resistance (CRPC). Methods: The multi-institutional prospective PROCURE cohort involves 2,026 patients who underwent radical prostatectomy for localized PCa. In this cohort, a subset of 145 patients who received ADT therapy for recurrent disease and had available plasma samples post-surgery were included in this study. The effect of therapy on steroid levels was assessed in paired samples obtained before and after the initiation of ADT (n=50), and samples from patients under combined ADT with AR pathway inhibitors, enzalutamide (n=10) and abiraterone (n =15). 11-oxygenated androgens (n=7) and canonical steroids, such as testosterone (T) and dihydrotestosterone (DHT), were quantified by mass spectrometry. Kaplan-Meier survival analyses were used to investigate relationships of androgen levels with the occurrence of CRPC. Results: 11-oxygenated androgens remained unaffected by ADT, which stands in contrast to the observed changes in T, DHT and other steroids. In men with castrated T levels, 11KT was the most abundant androgen. Elevated 11KT was associated with a sooner time to CRPC ( P=0.023). The 10-year CRPC event-free rate was 63% vs. 84% for 11KT levels above and below the median, respectively. The initiation of enzalutamide had no impact on 11-oxygenated androgen levels, whereas abiraterone significantly reduced 11KT levels owing to the adrenal origin of its precursor. Conclusions: Our findings indicate that 11KT is a significant component of the hormonal profile predictive of an earlier onset of CRPC and inhibition of its production by the CYP17A1 inhibitor abiraterone.

Metastatic prostate cancer is associated with distinct higher frequency of genetic mutations at diagnosis

Introduction and ObjectivesWe explored characteristic genetic mutations associated with metastatic prostate cancer (PCa) by comparing next generation sequencing (NGS) data between men with or without metastatic disease at diagnosis. MethodsWe queried the American Association for Cancer Research Project Genomics Evidence Neoplasia Information Exchange (GENIE) registry for men diagnosed with PCa. Patients were categorized into with (M1) or without metastatic disease (M0) groups. The difference in the frequency of genetic mutations between the two groups and the prognostic significance of the mutations were analyzed using SPSS V28. We included frequency rate of > 5% and P values < 0.05 were considered statistically significant to maintain over 95% true positive detection rate. ResultsOf a total of 10,580 patients with diagnosis of PCa in the dataset, we selected a study cohort of 1268 patients without missing data; 700 (55.2%) had nonmetastatic PCa, 421 (33.2%) and 147 (11.6%) patients had metastatic castration sensitive and resistant PCa respectively. The median age at diagnosis and serum prostate specific antigen (PSA) level for the entire cohort was 62.8 years (IQR 56.3–68.4) and 8.0 ng/ml (IQR 4.9–20.9) respectively. A vast majority of the cohort were of Caucasian ancestry (89.1%). Of a total of 561 genes sequenced, there were mutations in 79 genes (14.1%). The mutation frequency was significantly higher in M1PCa compared to M0PCa, 35.7% and 23.3%, respectively (P = <0.001). The median tumor mutational burden was also significantly higher in the samples from M1PCa (2.59 mut/MB) compared to M0PCa (1.96 mut/MB) (P < 0.001). Compared to M0PCa patients, M1PCa patients demonstrated significantly higher rate of genetic mutations; TP53 (38.73% vs. 17.71% P < 0.001), PTEN (25.70% vs. 11.71% P < 0.001), AR (17.25% vs. 1.43% P < 0.001), APC (11.8% vs. 4.43% P < 0.001), TMPRSS2 (31.5% vs. 11.14% P < 0.001), ERG (23.59% vs. 13.13% P < 0.001), FOXA1 (17.43% vs. 6.33% P < 0.001), MYC (8.45% vs. 2.29% P < 0.001), RB1 (10.39% vs. 2.43% P < 0.001) and CDK12 (8.45% vs. 1.31% P < 0.001). Of the various cellular signaling pathways, the androgen receptor signaling pathway was most often impacted. In the cohort with M1 disease, compared to men without genetic mutations the men with genetic mutations demonstrated worse survival (P = <0.001, log rank test). Compared to castration sensitive M1 patients, AR (57% vs. 4% P < 0.001), TP53 (50.7% vs. 34% P < 0.001), PTEN (35.2% vs. 22.1% P < 0.001), RB1(23.9% vs. 4.75% P < 0.001) were significantly more frequently mutated in castration resistant M1 patients. In contrast, mutations of SPOP (13.3% vs. 7.9% P < 0.001), FOXA1 (17.6% vs. 5.3% P < 0.001) and CDK12 (12% vs. 6.45% P < 0.001) were significantly more frequently found in castration sensitive M1 patients compared to castration resistant patients. ConclusionPatients with M1PCa demonstrated characteristic genetic mutations compared to M0PCa, which most often influenced androgen receptor signaling and is associated with worse survival. In addition, we identified distinct genetic mutations between castration sensitive and resistant M1PCa. These findings may be used to further our understanding and management of men with PCa.

Serrate RNA Effector Molecule (SRRT) Is Associated with Prostate Cancer Progression and Is a Predictor of Poor Prognosis in Lethal Prostate Cancer.

Arsenite-resistance protein 2, also known as serrate RNA effector molecule (ARS2/SRRT), is known to be involved in cellular proliferation and tumorigenicity. However, its role in prostate cancer (PCa) has not yet been established. We investigated the potential role of SRRT in 496 prostate samples including benign, incidental, advanced, and castrate-resistant patients treated by androgen deprivation therapy (ADT). We also explored the association of SRRT with common genetic aberrations in lethal PCa using immunohistochemistry (IHC) and performed a detailed analysis of SRRT expression using The Cancer Genome Atlas (TCGA PRAD) by utilizing RNA-seq, clinical information (pathological T category and pathological Gleason score). Our findings indicated that high SRRT expression was significantly associated with poor overall survival (OS) and cause-specific survival (CSS). SRRT expression was also significantly associated with common genomic aberrations in lethal PCa such as PTEN loss, ERG gain, mutant TP53, or ATM. Furthermore, TCGA PRAD data revealed that high SRRT mRNA expression was significantly associated with higher Gleason scores, PSA levels, and T pathological categories. Gene set enrichment analysis (GSEA) of RNAseq data from the TCGA PRAD cohort indicated that SRRT may play a potential role in regulating the expression of genes involved in prostate cancer aggressiveness. Conclusion: The current data identify the SRRT's potential role as a prognostic for lethal PCa, and further research is required to investigate its potential as a therapeutic target.

Using microfluidic models to evaluate whether monocyte preconditioning plays a role in tumor-associated macrophage mediated resistance to hormone therapy in men with prostate cancer.

228 Background: While men with metastatic castrate-resistant prostate cancer benefit greatly from 2nd generation androgen targeted therapies (ATTs), the utility of these therapies is inevitably limited by the development of resistance. Tumor associated macrophages (TAMs) are a myeloid immune cell population within the prostate tumor microenvironment (TME) that have been shown to play an integral role in development of ATT-resistance. However, the pathways that underlie TAM-mediated ATT resistance remain under investigation. In particular, many TAMs within the TME are derived from circulating monocytes and it is not yet clear whether the pathways driving TAM-mediated resistance are activated exclusively within the TME or if the activation of critical resistance pathways begins while the cells are circulating as monocytes. In this study, we utilized novel microscale technologies to investigate the transcriptome of monocytes and macrophages derived from patients progressing and responding to ATTs as well as the degree to which the macrophages promote ATT resistance in prostate tumor models. Methods: Primary monocytes were isolated from 22 men with prostate cancer who were either progressing or responding to 2ndgeneration ATTs. A portion of the monocytes from each patient were isolated for transcriptome analysis and the rest were differentiated into monocyte-derived macrophages (MDMs). MDMs were then cultured in monoculture or in co-culture with androgen-independent prostate tumor cells (22Rv1 and C42B). Each culture was then left untreated or treated with enzalutamide therapy. Following culture/treatment, each macrophage condition was isolated for transcriptome analysis and tumor cell populations from each condition were evaluated for treatment cytotoxicity. Results: Viability data from MDM-C42B co-culture demonstrated a 20% increase in tumor cell viability following enzalutamide treatment when C42B cells were cultured with primary MDMs from castrate-sensitive patients as compared to MDMs from castrate-resistant patients. Subsequent transcriptome analysis demonstrated key signatures in monocyte/macrophage populations that were associated ATT response. Conclusions: Leveraging a novel microfluidic culture platform known as Stacks, we were able to utilize primary, patient-derived cells to demonstrate that the role of TAMs in ATT resistance within the prostate TME is dependent, at least in part, on factors that are present prior to extravasation into the TME. Transcriptome analysis identified candidate pathways, which may be driving TAM-mediated differences in ATT response. These findings have the potential to lead to future use of circulating monocytes as a predictive biomarker as well as lead to the identification and targeting of ATT resistance pathways in patients.

Plasma Copy Number Alteration-Based Prognostic and Predictive Multi-Gene Risk Score in Metastatic Castration-Resistant Prostate Cancer.

Simple SummaryAt a genomic level metastatic castrate resistant prostate cancer state is highly heterogeneous and no clear genome-based prognostic or predictive biomarkers exist in practice. We evaluated multiple copy number somatic alterations in two castrate resistant patient cohorts to determine if a genome-based risk score at the copy number level can predict clinical outcomes. The first cohort included patients in a prospective clinical-trial in which abiraterone acetate was given and the other comprised of a real-world hospital-registry. We extracted plasma cell free DNA in both cohorts and performed low pass whole genome sequencing. Copy number alterations were identified for 24 candidate genes and a final composite score developed from 11 genes. This risk score was able to predict survival in castrate resistant patients after adjusting for known clinical biomarkers. Additionally, the multi-gene copy number alteration based risk score algorithm also predicted if abiraterone acetate would be effective in castrate resistant patients.: BackgroundA plasma cell-free DNA (cfDNA) multi-gene copy number alteration (CNA)-based risk score was evaluated to predict clinical outcomes in metastatic castrate resistant prostate cancer (mCRPC) patients. Methods: Plasma specimens from two independent mCRPC patient cohorts (N = 88 and N = 92 patients) were used. A treatment-naïve mCRPC cohort (prospective clinical-trial cohort) included plasma samples before treatment with abiraterone acetate/prednisone and serially at 3-months. A separate real-world hospital-registry (RWHR) mCRPC cohort included a single blood sample collected prior to mCRPC treatments in 92 mCRPC patients following ADT failure. Low pass whole genome sequencing was performed on plasma cell-free DNA (cfDNA) and copy number alterations (CNAs) were identified for 24 candidate genes of interest. Associations of individual gene CNAs with 3 month primary resistance to therapy, progression-free survival (PFS) in the prospective trial cohort and overall survival (OS) in both cohorts was evaluated by Cox regression. A multi-gene risk score was determined for significantly associated candidate CNAs for predicting clinical outcomes. Clinical factors were included in the risk model for survival. Statistical significance for all tests was set at 0.05. Results: In the prospective trial cohort, patients responding to treatment were observed to have a significant copy number decrease in AR (p = 0.001) and COL22A1 (p = 0.037) at 3 months, while the non-responder group showed a significant CNA decrease in NKX3.1 (p = 0.027), ZBTB16 (p = 0.025) and CNA increases in PIK3CB (p = 0.006). Based on the significance level of each gene, CNAs in 11 of the 24 genes (AR, COL22A1, MYC, NCOR1, NKX3.1, NOTCH1, PIK3CA, PIK3CB, TMPRSS2, TP53, ZBTB16) were selected to develop a Cox-regression coefficient-based weighted multi-gene risk score for predicting mCRPC outcomes in both cohorts. A higher multi-gene risk score was observed to have poor OS in mCRPC patients in the prospective trial cohort (p = 0.00019) and for the RWHR cohort, (p < 0.0001). A higher risk score was also associated with poor PFS in the prospective cohort (p = 0.0043). Conclusions: A multi-gene CNAs-based risk score derived from plasma cfDNA may predict treatment response and prognosticate survival in mCRPC and warrants prospective validation of risk-based algorithms.

Establishment of a Novel Combined Nomogram for Predicting the Risk of Progression Related to Castration Resistance in Patients With Prostate Cancer

Background: The emergence of castration resistance is fatal for patients with prostate cancer (PCa); however, there is still a lack of effective means to detect the early progression. In this study, a novel combined nomogram was established to predict the risk of progression related to castration resistance. Methods: The castration-resistant prostate cancer (CRPC)-related differentially expressed genes (DEGs) were identified by R packages “limma” and “WGCNA” in GSE35988-GPL6480 and GSE70768-GPL10558, respectively. Relationships between DEGs and progression-free interval (PFI) were analyzed using the Kaplan–Meier method in TCGA PCa patients. A multigene signature was built by lasso-penalized Cox regression analysis, and assessed by the receiver operator characteristic (ROC) curve and Kaplan–Meier curve. Finally, the univariate and multivariate Cox regression analyses were used to establish a combined nomogram. The prognostic value of the nomogram was validated by concordance index (C-index), calibration plots, ROC curve, and decision curve analysis (DCA). Results: 15 CRPC-related DEGs were identified finally, of which 13 genes were significantly associated with PFI and used as the candidate genes for modeling. A two-gene (KIFC2 and BCAS1) signature was built to predict the risk of progression. The ROC curve indicated that 5-year area under curve (AUC) in the training, testing, and whole TCGA dataset was 0.722, 0.739, and 0.731, respectively. Patients with high-risk scores were significantly associated with poorer PFI (p < 0.0001). A novel combined nomogram was successfully established for individualized prediction integrating with T stage, Gleason score, and risk score. While the 1-year, 3-year, and 5-year AUC were 0.76, 0.761, and 0.762, respectively, the good prognostic value of the nomogram was also validated by the C-index (0.734), calibration plots, and DCA. Conclusion: The combined nomogram can be used to predict the individualized risk of progression related to castration resistance for PCa patients and has been preliminarily verified to have good predictive ability.

The role of chemotherapy in metastatic prostate cancer.

To summarize the role of chemotherapy and offer some guidance regarding the selection of chemotherapy in mPC. Patients with mHSPC have varied prognoses with testosterone suppression alone (androgen deprivation therapy, ADT) and differential responses to docetaxel with ADT. Patients with de novo and metachronous high-volume disease have a robust survival benefit with the addition of docetaxel to hormonal therapies. Patients with synchronous low-volume disease have a more modest survival benefit from docetaxel and there is no evidence of survival benefit with docetaxel in patients with metachronous low-volume disease. Integration of biomarkers may refine treatment selection regardless of volume of disease. Docetaxel and cabazitaxel also impart an OS benefit in patients with metastatic castration-resistant prostate cancer (mCRPC). The choice of chemotherapy in mCRPC depends on treatment received in mHSPC setting. Docetaxel remains the first line chemotherapy in castration-resistant patients who have not received it in mHSPC followed by cabazitaxel, otherwise cabazitaxel can be deployed without docetaxel retreatment. Chemotherapy is a key class of therapy for selected patients with mHSPC and mCRPC.

A SIX1 degradation inducer blocks excessive proliferation of prostate cancer.

Prostate cancer (PC) remains a great medical challenge due to its high incidence and the development of castration resistance in patients treated with androgen deprivation therapy. Deubiquitinases, the enzymes that specifically hydrolyze ubiquitin chains on their substrates, were recently proposed as a serious of critical therapeutic targets for cancer treatment. Our previous study has been reported that the ubiquitin specific peptidase 1 (USP1) functionally acts as a deubiquitinase of sine oculis homeobox homolog 1 (SIX1) and contributes to the proliferation and castration resistance of PC. The stabilization of SIX1 by USP1 partially depends on the status of glucose-regulated protein 75 (GRP75). In this study, we aimed to identify a SIX1 degradation inducer via inhibiting the USP1-SIX1 axis. we screened a range of kinase inhibitors and showed that SNS-032 is the best candidate to trigger the ubiquitinated degradation of SIX1. SNS-032 not only restrains activity of the USP1-SIX1 axis and cell cycle progression, but also results in apoptosis of PC cells. Moreover, the combination of SNS-032 and enzalutamide synergistically induces apoptosis and downregulates expression of USP1, SIX1, and AR/AR-V7 in AR-V7 highly expressed 22Rv1 cells. Overall, our findings may develop a novel and effective strategy to overcome castration resistance in PC for the identification of a SIX1 degradation inducer via targeting the USP1-SIX1 axis.

Phase II Trial of SBRT and Androgen Deprivation for Oligometastases in Prostate Cancer

SBRT-SG 05 is a collaborative (SBRT-SG, GICOR and SEOR) prospective multicenter phase II trial testing SBRT and androgen deprivation therapy (ADT) in oligorecurrent prostate cancer patients.Prostate cancer patients (hormone-sensitive or castration-resistant) in an oligorecurrent stage defined as less than 5 bone or lymph node metastases by Choline PET-CT or/and WB-DWI-MRI, after primary treatment, were assigned to receive ADT and SBRT (Vertebral metastases: 1 × 16-18Gy or 3 × 8-9Gy; lymph node metastases: 3 × 10-11 Gy or 6 × 7,5Gy; non-spinal bone metastases: 1 × 16Gy or 3 × 10Gy). Inclusion criteria included: more than 1 year from primary treatment to biochemical recurrence and PSA doubling time greater than 2 months. A minimum of 24 months of LhRh analogues from the time of the enrollment was required and concomitant treatment with chemotherapy, abiraterone or enzalutamide was not allowed. Oncologic outcomes defined by PCWG3 were evaluated separately for hormone-sensitive and castration-resistant patients, using Kaplan-Meier competing risks, and Cox regression. Toxicity was prospectively evaluated according to CTCAE.v4 criteria.From 07/2014 to 12/2019, 81 patients from 14 Spanish centers were recruited with a total of 117 oligometastases treated, 67 in lymph nodes, 43 in non--spinal bones and 7 in spinal bones. 14 patients were recruited in a castration-resistance status. Median follow-up was 41 months, (range 18 - 72 months). 13 hormone-sensitive (19,4%) and 8 castration-resistant (57,1%) oligorecurrent patients presented distant disease progression. Median distant progression-free survival (DPFS) was 54,2 months (IC95% = 48,2 - 60,3). 18 of the patients who progressed (85,7%) were treated with SBRT for the new lesions, 7 of them presented a subsequent distant progression (38,9%), with a median of second DPFS of 24,4 months (95% CI = 23,7 - 25,2). In the castration resistant subgroup, median DPFS was 33,5 months (range 14,8 - 52,1), 42,9% of them were free from distant disease progression at last follow-up, without the need to start second generation hormonal treatment. Tolerance and toxicity profiles were excellent, none of the patients developed toxicity ≥G3 or symptoms related to local progression of the disease.Combination of SBRT and ADT is a safe treatment approach with favorable clinical outcomes for hormone-sensitive and castration-resistant prostate cancer patients. Validation studies are needed in castration-resistant patients. ClinicalTrials.gov Identifier: NCT02192788.

Abstract 1326: Second generation androgen receptor signaling inhibitor resistant neuroendocrine like prostate cancer: A mechanistic study

Abstract Background:Failure of castration resistant prostate cancer patients to Androgen Receptor Signaling Inhibitor (ARSI) poses a major challenge in terms of therapeutic development. The heterogeneous nature of prostate cancer makes it difficult to stratify the treatment modalities. A multitude of variable pathological and genetic alterations induced by systemic treatment adds further to the therapeutic complexity. Upon continued exposure to enzalutamide (ARSI), nearly 15-20% of castration resistant patients advance towards a highly aggressive neuroendocrine like phenotype with concomitant functional loss of RB1 and TP53 and persistent AR expression in some. Elucidation of the underlying mechanism of resistance among this aggressive subset of patients is of utmost importance to clinically stratify the treatment options and target these advanced neuroendocrine like patients, who currently lack specific treatment approaches. The following study aims to identify the molecular signature responsible for driving this enzalutamide resistant neuroendocrine like development. Objective:The primary objective of the study is to identify the molecular mechanism behind ARSI induced neuroendocrine like Prostate cancer development. Methods:We have developed two cell line model systems. C4-2 has been genetically modified to develop a simultaneous genetic loss of RB1 and TP53 (DKD). C4-2B has been kept on continued exposure to Enzalutamide to develop Enzalutamide Resistant (C4-2BER). C4-2BER maintains AR expression while DKD loses AR expression, resembling different stages in neuroendocrine like development. Using Western Blot and RT PCR analysis the neuroendocrine like background of these resistant cell line models has been characterized. We performed an RNA-Seq with C4-2B and its resistant model C4-2BER and further downstream analysis through gene ontology and GSEA were performed. Results:Model system characterization study revealed neuroendocrine like characteristics and gene expression. Genetic analysis revealed an upregulation of multiple genes in C4-2BER in comparison to its parental C4-2B, which is comparable to patient dataset available online. GSEA analysis revealed several neuronal biology related pathways to be prominently upregulated among C4-2BER. Further analysis revealed that expression of WT1, which binds near most of these upregulated genes, is downregulated in C4-2BER. Conclusions:The downregulation of WT1 is noted during progression from CRPC towards enzalutamide resistant neuroendocrine development in C4-2BER, which is in turn accompanied with various epigenetic changes. Understanding such pattern of changes and identifying the underlying molecular signature would help elucidate the targets behind treatment induced neuroendocrine characteristics from a therapeutic point of view. Citation Format: Sreyashi Bhattacharya, Ridwan Islam, Sanika Bodas, Navatha Polavaram, Kaustubh Datta, Samikshan Dutta. Second generation androgen receptor signaling inhibitor resistant neuroendocrine like prostate cancer: A mechanistic study [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1326.

SEOM clinical guidelines for the treatment of advanced prostate cancer (2020)

The treatment of advanced prostate cancer has evolved due to recent advances in molecular research and new drug development. Dynamic aberrations in the androgen receptor, DNA repair genes, PTEN-PI3K, and other pathways drive the behavior of advanced prostate cancer allowing a better selection of therapies in each patient. Tumor testing for BRCA1 and BRCA2 is recommended for patients with metastatic prostate cancer, also considering a broad panel to guide decisions and genetic counseling. In symptomatic metastatic patients, castration should be stared to palliate symptoms and prolong survival. In high-risk or high-volume metastatic hormone-naïve patients, castration should be combined with docetaxel, abiraterone, enzalutamide or apalutamide. Radiotherapy to the primary tumor combined with systemic therapy is recommended in low-volume mHNPC patients. In patients with non-metastatic castration-resistant tumors, risk stratification can define the frequency of imaging. Adding enzalutamide, darolutamide or apalutamide to these patients prolongs metastasis-free and overall survival, but potential adverse events need to be taken into consideration. The choice of docetaxel, abiraterone or enzalutamide for treating metastatic castration-resistant patients depends on previous therapies, with cabazitaxel being also recommended after docetaxel. Olaparib is recommended in BRCA1/BRCA2 mutated castration-resistant patients after progression on at least one new hormonal therapy. Aggressive variants of prostate cancer respond to platinum-based chemotherapy. To optimize treatment efficiency, oncologists should incorporate all of these advances into an overall therapeutic strategy.

Genomic mutation profiling using liquid biopsy in Korean patients with prostate cancer: Circulating tumor DNA mutation predicts the development of castration resistance.

PurposeTo investigate germline and somatic mutation profiles in Korean patients with prostate cancer using liquid biopsy and solid tissue testing and to evaluate the prognostic value of circulating tumor DNA (ctDNA) in predicting castration resistance in patients with metastatic hormone-sensitive prostate cancer (mHSPC).Materials and MethodsPlasma samples from 56 prostate cancer patients were subjected to next-generation sequencing (NGS) to identify germline mutations and ctDNA analysis using liquid biopsy to detect somatic mutations. Additionally, paired solid cancer tissues from 18 patients were subject to NGS to detect somatic mutations. The clinical parameters and ctDNA profiles of patients with mHSPC were analyzed to evaluate the prognostic value of ctDNA mutations with respect to predicting castration resistance using Cox proportional hazards regression analysis.ResultsGermline mutations occurred in 3.6% of the patients in this cohort, with mutations identified in RAD50 (1.8%) and BRCA1 (1.8%). Somatic mutations detected by liquid biopsy and solid tissue testing were common in TP53 (12.5%), PIK3CA (3.6%), and TMPRSS2-ERG (3.6%). Of the 18 patients with paired tissue testing, two patients had at least one identical somatic mutation in both the liquid biopsy and solid tissue testing. In patients with mHSPC, the presence of ctDNA mutations could independently predict the castration resistance development (hazard ratio, 13.048; 95% confidential interval, 1.109–153.505; p=0.041).ConclusionsKorean patients with prostate cancer showed a relatively low germline mutation rate compared to other ethnicities. The ctDNA mutations detected by liquid biopsy can predict the development of castration resistance in patients with mHSPC.

Androgen receptor signaling-targeted therapy and taxane chemotherapy induce visceral metastasis in castration-resistant prostate cancer.

Visceral metastasis (VM), an important poor prognostic factor of prostate cancer (PC), is not commonly observed in castration sensitive status but is often observed after castration-resistant progression. However, the site, timing of emergence, and incidence of VM in castration-resistant patients have not yet been fully elucidated. Demographic, surgical, pathological, and follow-up data of PC patients treated at Kanazawa University Hospital between January 2000 and December 2016 were retrospectively analyzed using their medical charts. From this data, risk factors of VM and survival of patients with VM were elucidated. Of 1364 patients, 21 (1.5%) had VM at diagnosis. Of 179 (13.1%) castration-resistant patients, 55 experienced emergence of new VM during treatment course. Incidence of new VM, especially nonlung, such as liver and adrenal metastases, increased significantly in proportion with the number of prescribed treatments. Multivariate analysis revealed that T stage, M stage, age, and treatment history with androgen receptor (AR) signaling-targeted agents and/or taxanes significantly increased the risk of VM. Compared with the group with VM at diagnosis, survival after diagnosis of VM following treatment was significantly shorter. Although sequential use of new AR signaling-targeted agents and taxanes for castration-resistant PC (CRPC) is a standard treatment strategy, it often results in development of VM. Elucidating the mechanisms of VM are essential to improve survival in patients with CRPC.

572 - Prognostic significance of time to castration resistance in patients with metastatic castration-sensitive prostate cancer

572 - Prognostic significance of time to castration resistance in patients with metastatic castration-sensitive prostate cancer

Abstract B08: Tumor-educated platelets for early prostate cancer diagnosis, and therapy stratification in patients with metastasized castration resistant prostate cancer

Abstract One in every ten men diagnosed with prostate cancer will have metastases at some point, causing the high mortality of prostate cancer. Only earlier diagnosis has the chance to save those lives. However, correct therapy stratification may prolong the life of the patients without severely reducing the quality of life, thereby possibly turning a deadly disease into a chronic disease. For this to happen, we need predictive biomarkers that can be employed to longitudinally follow the disease in order to identify vulnerabilities and to monitor acquired resistance for personalized medicine. Using the platelet-enriched fraction of a blood sample, we here show that we can use the ability of platelets to sequester material during circulation to provide information derived from the tumor. This information could be used for early detection of prostate cancer. By using the platelet test in combination with PSA measurements, we may be able to rule out a majority of the false negatives associated with the PSA test. Furthermore, the platelet platform can be used in synergy with other biomarker sources such as circulating tumor DNA or protein biomarkers, providing the possibility to predict and monitor outcome of abiraterone therapy, and providing alternatives to the nonfunctional therapy by guiding therapy switching, in metastatic castration-resistant patients. Citation Format: Lee-Ann Tjon-Kon-Fat, Linda Köhn, Myron Best, Marie Lundholm, Thomas Wurdinger, Anders Widmark, Camilla Thellenberg-Karlsson, Pernilla Wikström, Jonas Nilsson. Tumor-educated platelets for early prostate cancer diagnosis, and therapy stratification in patients with metastasized castration resistant prostate cancer [abstract]. In: Proceedings of the AACR Special Conference on Advances in Liquid Biopsies; Jan 13-16, 2020; Miami, FL. Philadelphia (PA): AACR; Clin Cancer Res 2020;26(11_Suppl):Abstract nr B08.

Extragonadal Steroids Contribute Significantly to Androgen Receptor Activity and Development of Castration Resistance in Recurrent Prostate Cancer after Primary Therapy.

Beyond testosterone, several steroids contribute to the activation of the androgen receptor pathway, but their relative contributions to the activation of the androgen receptor signaling axis in patients with castrated prostate cancer remain unknown. Serum levels of 9 steroids were measured by mass spectrometry from continuously castrated patients of the PR.7 study (219) and from the PCA24 cohort (116). For each steroid standard curves for dose dependent prostate specific antigen promoter activation were built in castration sensitive (LAPC4) and resistant (VCaP) prostate cancer models. Standard curves were used to determine the androgen receptor activation potency for each steroid measurement from patients in these trials. In LAPC4 and VCaP cells testosterone, dihydrotestosterone and androstenedione induced androgen receptor transcriptional activity, while dehydroepiandrosterone, 5alpha-androstan-3beta,17beta-diol, androstenediol and androsterone stimulated androgen receptor only in VCaP cells. Extragonadal steroids were responsible for 34% (LAPC4) and 88% (VCaP) of the serum total androgen receptor transcriptional activity found in castrated cases. The total androgen receptor transcriptional activity secondary to testosterone, dihydrotestosterone and androstenedione was associated with time to castration resistance in patients from the PR.7 study (HR 2.17, 95% CI 1.12-4.23, p=0.02) in multivariate analysis using the castration sensitive model (LAPC4). Androgen receptor transcriptional activity of extragonadal androstenedione was the only steroid statistically associated with time to castration resistance in univariate analysis (HR 1.89, 95% CI 1.04-3.44, p=0.036). Extragonadal steroids contribute significantly to the androgen receptor axis activation at castration levels of testosterone in recurrent nonmetastatic prostate cancer and these sustain the development of castration resistance after primary local treatment.

Prognostic Value of Germline DNA Repair Gene Mutations in De Novo Metastatic and Castration-Sensitive Prostate Cancer.

Germline DNA damage repair gene mutations (gDDRm) have been found in approximately 12% of patients with metastatic prostate cancer (mPCa). Previous studies of the clinical impact of gDDRm have mainly been in the setting of metastatic castration-resistant prostate cancer (mCRPC). This study aimed to determine the prognostic value of gDDRm in de novo metastatic and castration-sensitive prostate cancer (mCSPC). We retrospectively collected the records of 139 consecutive men with de novo mCSPC who initially received systemic therapies following guidelines. This included 128 patients who underwent genetic testing at our center and 11 patients referred to our center after being identified as gDDRm carriers. Time to mCRPC was collected. Kaplan-Meier and log-rank analysis were used to analyze the association between gDDRm and clinical outcomes. Survival outcomes were adjusted using multivariable Cox regression models. Of the 139 patients with de novo mCSPC, 28 gDDRm carriers were identified. Median time progressing to mCRPC was significantly shorter in patients carrying gDDRm than in those without mutations (8.3 vs 13.2 months; hazard ratio [HR], 2.37; p < .001). Moreover, median progression time was almost halved in BRCA2 carriers (6.3 vs. 13.2 months; HR, 3.73; p < .001). Subgroup analysis revealed that the presence of gDDRm indicated poor therapy response regardless of disease volume and prostate-specific antigen nadir within the first 7 months. Presence of gDDRm remained independently associated with increased risk of progression to mCRPC in multivariate analysis (adjusted HR, 1.98; p = .006). Our study suggested that positive gDDRm status predicted rapid progression to castration resistance in patients with de novo mCSPC. We propose identifying gDDRm status at the time of diagnosis for mCSPC patients, considering it is the first step of tailoring individualized treatment. In addition, DNA repair genes were a good therapeutic target for poly (ADP-ribose) polymerase inhibitors, and our results call for more frontline targeted therapy trials in gDDRm carriers to prolong the progression time. Results of this study suggested that positive germline DNA damage repair gene mutation (gDDRm) status predicted earlier progression to castration resistance in patients with de novo metastatic and castration-sensitive prostate cancer (mCSPC). These findings indicated the importance of intense therapy for some subgroups of mCSPC, especially for mCSPC harboring gDDRm with low-volume disease. Moreover, gDDRm was a good therapeutic target for poly (ADP-ribose) polymerase inhibitors, and these findings call for more molecular marker driven trials moving to the mTNPC setting.

Combined targeting of EGFR and HER2 against prostate cancer stem cells

ABSTRACTProgression of prostate cancer has been associated with EGFR and HER2 activation and to tumor-initiating cells contribution toward chemotherapy resistance. We investigated the efficacy of a dual intervention against EGFR and HER2 to deplete the tumor-initiating cells, optimize the chemotherapy management and prevent the progression of castration-resistant prostate cancer (CRPC) cells. Using DU145, PC3, and 22Rv1 CRPC cell lines, biochemical analysis revealed activation of EGFR, HER2, MAPK, and STAT3 in DU145 and 22Rv1, and AKT and SRC in DU145 and PC-3. pSTAT3 nuclear staining was observed in DU145 xenografts and in 12 out of 14 CRPC specimens. The in vivo dual targeting of ErbB receptors with Cetuximab and Trastuzumab combined with chemotherapy caused an effective antitumor response in DU145 xenografted mice displaying STAT3 activation; conversely PC-3 bearing mice experienced tumor relapse. The potentiating of in vivo cytotoxic effect in DU145 model was accompanied by a significant decrease of prostatosphere-forming capacity assessed in vitro on residual tumor cells. Additionally, combined treatment in vitro with Cetuximab, Trastuzumab and chemotherapy negatively affected DU145 and 22Rv1 sphere formation, suggesting the critical function of ErbB receptors for tumor-initiating cells proliferation; no effect on PC-3 clonogenic potential was observed, indicating that other receptors than EGFR and HER2 may sustain PC3 tumor-initiating cells. These findings provided the preclinical evidence that the dual inhibition of EGFR and HER2 by targeting tumor-initiating cells may improve the efficacy of the current chemotherapy regimen, bringing benefits especially to castration-resistant patients with activated STAT3, and preventing disease progression.