Citations

ABSTRACT Background Inflammation plays a critical role in cancer cell proliferation; however, the specific role of inflammasomes, multiprotein complexes that regulate inflammation‐associated signaling pathways, in prostate cancer (PCa) remains insufficiently explored. This study aims to characterize the expression of inflammasome‐related genes in PCa and evaluate their association with clinical outcomes. Methods De‐identified transcriptome data from the Decipher GRID RP, a cohort of 52,266 radical prostatectomy (RP) samples tested (2016–2024) with the Decipher prostate genomic classifier (Veracyte, San Diego, CA), were retrieved from the GRID registry (NCT02609269). Expression analysis of 34 genes involved in inflammatory pathways was conducted to associate their expression with clinical and genomic variables. Outcomes analyses were conducted on a retrospective cohort of 855 patients treated with RP (META855). Results Analysis of inflammasome gene expression in the GRID RP cohort revealed that most genes exhibit low baseline expression, whereas HSP90AB1, APP, TXN, and TXNIP demonstrate strong expression signals. Additionally, higher expression of most genes was associated with Gleason Grade Group 4–5 and very high Decipher scores. On survival analysis of the META855 cohort, higher expressions of AIM2 and HSP90AB1 were significantly associated with worse metastasis‐free survival. Conversely, both high and low expression levels of NLRP3 were associated with better metastasis‐free survival outcomes following RP compared to average expression. On multivariable Cox regression analysis, higher expressions of AIM2 (HR 1.75) and HSP90AB1 (HR 1.60) were significantly associated with shorter time to metastasis following RP. Conclusions There is molecular heterogeneity within pro‐inflammatory genes among patients with PCa. Our findings showed there is a potential association between the expression levels of certain inflammasomes, such as AIM2, HSP90AB1, and NLRP3, and oncological outcomes following RP.

392 Background: Cancer-associated fibroblasts (CAFs) are a major component of the tumor microenvironment, exerting both tumor-promoting and tumor-restrictive effects, and in some cases, dual roles. CAFs are heterogeneous and have been implicated in tumor progression, metastasis, and therapeutic resistance. Recent translational evidence suggests the existence of at least two CAF subtypes: CAV1+ CAFs and FAP+FN1+ CAFs. The clinical utility of subclassifying CAFs in prostate cancer remains undefined. In this study, we aimed to examine the correlation of CAF subtypes in localized prostate cancer with Decipher genomic classifier (GC) scores, Grade Group (GG), and the presence of adverse pathological features (APF). Methods: We retrieved de-identified transcriptomic and pathological data from 55,329 radical prostatectomy (RP) samples tested with the Decipher prostate genomic classifier (Veracyte, San Diego, CA) between 2016 and 2024, available through the GRID registry (NCT02609269). A subset of 855 patients (META855 cohort) treated with RP was utilized for outcomes analyses. CAF subtypes were defined based on the expression of key biomarkers (FN1, FAP, and CAV1), normalized to total CAF estimates. Correlation analyses and multivariable Cox regression models were performed to evaluate the association of CAF subtypes with GC scores, GG, APF. Metastasis-free survival (MFS) estimates were generated using Kaplan–Meier methodology. Results: FAP and FN1 normalized expressions were highly correlated (r=0.61) and weakly correlated with CAV1 suggesting that they represent two distinct subtypes of CAF. Samples with high expression (top 25%) of FN1 (FN1+) and FAP (FAP+) were enriched with very high Decipher (> 0.85, VHD) and GG4-5. As such, 37% and 32% of FAP+ were VHD and GG4-5 respectively compared to ~18% for low FAP(low 25%). While for FN+ 33.9% were VHD, and 31.5% GG4-5. Patients with FAP+FN1+, 42.5% and 37.1% were VHD, and had GG4-5. Samples with high CAV1 (CAV1+) were associated with lower rate of VHD (15.5%) or GG4-5 (20.8%) compared to low CAV1 (35.4% for VHD and 24.5% for GG4-5). When evaluating VHD in FAP+FN1+CAV1- subgroup, 58% were VHD compared to 6.4% in FAP-FN1-CAV1+. The 5-year MFS was 78% in FAP+FN1+CAV- compared to 96% in FAP-FN1-CAV1+ (p<0.01). When evaluating the biological implications of FAP+FN1+, we found that FAP and FN1 expression is highly correlated to angiogenesis and EMT pathways, radiation sensitivity signature (PORTOS). Conclusions: FAP+FN1+CAV- is a unique subset of CAFs that is associated with aggressive prostate cancer behavior. Our findings may lay the foundation for future efforts to modulate CAFs in localized prostate cancer with existing therapeutics targeting FAP or FN1.

382 Background: Androgen receptor signaling drives prostate cancer (PC) progression, and genes involved in androgen production, uptake, and conversion (APUC) are key therapeutic targets. We previously defined a 6-APUC gene set ( HSD3B1, HSD3B2, CYP3A43, CYP11A1, CYP11B1, and CYP17A1 ), that identified metastatic PC with favorable prognosis and predict docetaxel benefit. However, the expression landscape and clinical relevance of APUC genes have not been interrogated in localized PC. Methods: We analyzed the expression of 21 APUC genes in 55,329 radical prostatectomy tumor samples that underwent Decipher prostate genomic classifier (GC) testing (Veracyte Inc) between 2016-2024. Baseline clinical/pathologic factors were retrieved from Decipher GRID database (NCT02609269). Associations between gene expression quartiles with PathoGenomic Risk Factors (PGRF) including Very High Decipher score >0.85 (VHD), Grade Group (GG) 4-5, LNI and SVI were examined. Associations with distant metastatic (DM) outcomes and metastasis free survival (MFS) were evaluated using logistic regression in Mayo545 and Cox regression in Meta855 RP cohorts, respectively. Results: High expression of SRD5A2 was associated with favorable PGRF (lower odds ratio (OR), p<0.0001), lower rate of development of DM (OR 0.36, p<0.05), and longer MFS (Hazard ratio (HR) 0.51, p<0.05). HSD17B6 showed similar results for PGRF (lower OR, p<0.0001), DM (OR 0.58, p<0.05) and longer MFS (HR 0.39, p<0.05) despite being associated with GG4-5 and SVI+ in samples with VHD. In contrast, high expression of SRD5A3 and HSD17B10 had high OR for PGRFs (p<0.0001). High expression of SLCO2B1 , an androgen uptake gene, had the strongest association with GG4-5 and SVI/LNI (p<0.001 for both). We noted that SRD5A2 lacked correlation with SRD5A1 and SRD5A3 , which instead correlated with each other. Compared to all APUC genes, SRD5A2 had limited correlations with almost all APUC genes, including ones that exhibited robust cross correlation with each other . Similar to our prior finding, most APUC genes demonstrated negative correlation with AR expression and AR activity signatures. Key outcomes were validated based on transcriptomic data from 492 samples from TCGA database. Conclusions: Comprehensive analysis of 21 APUC genes in over 55,000 PC identified distinct, context-dependent associations with metastatic outcomes and clinical and molecular risk factors. Notably, high SRD5A2 expression was associated with lower odds of high-risk features and metastatic outcomes, whereas SRD5A1 and SRD5A3 linked to adverse outcomes, suggesting critical yet divergent roles among 5-alpha-reductase family members. These findings underscoring androgen-metabolic heterogeneity and highlighting SRD5A2 as a potential biomarker of indolent biology in localized prostate cancer.

Abstract Background Prostate cancer is a heterogeneous disease comprising diverse cell types within the tumor microenvironment that support cancer cell survival. Using single cell and spatial transcriptomics, we previously identified subpopulations of treatment-persistent cancer cells exhibiting regenerative properties and a distinct molecular signature. Herein, we aimed to characterize the locked ‘Persist’ signature (PS) and its association with outcomes in a large cohort of non-metastatic prostate cancer tumors. Methods Patients with non-metastatic prostate cancer that underwent Decipher prostate genomic classifier and whole-transcriptome profiling on biopsy (BX, n=146,941) and radical prostatectomy (RP, n=55,329) specimens between October 2016 and February 2024 were included (Veracyte Inc., San Diego, CA, USA). Baseline clinical and pathological data from deidentified patients as well as signature scores were retrieved from the Decipher Genomic Resource for Intelligent Discovery (GRID) registry (Clinical Trials identifier: NCT02609269). The PS score based on the expression of 17 genes was calculated for all samples. Results PS was significantly associated with adverse clinical and pathological variables. In biopsy sample, PS was higher in cases with worse T3/4 clinical stage, Grade group (GG4-5), and high/very high NCCN risk (p&lt;0.001 for all). In RP sample, PS was significantly higher in patients with GG4-5, extraprostatic extension, seminal vesicle invasion and lymph node involvement (p&lt;0.001 for all). PS was also higher in patients with very high Decipher (&gt;0.85) in both BX and RP (p&lt;0.001 for both). When evaluating the prognosis of PS in multiple retrospective cohorts, PS in biopsy was prognostic of adverse pathology features at RP. PS was also prognostic of distance metastasis (DM) in multiple RP cohorts with long-term follow up (META855). In the ARNEO trial testing apalutamide in addition to ADT as neo-adjuvant treatment prior RP, PS was prognostic of early recurrence. In the Stampede trial, PS was prognostic of progression free survival, PCSM and OS in both non-metastatic and metastatic disease. When associating PS with other GRID signatures, PS was higher in samples with homologous recombination deficiency, TP53 mutations, Luminal B and luminal proliferating subtypes. On the other hand, PS was lower in samples with low androgen receptor-activity, RB-loss and neuroendocrine-like tumors. Finally, PS was positively correlated with radiation sensitivity signatures. Conclusions Persist is a novel molecular signature associated with more aggressive tumor characteristics. Future studies aim to further examine beyond this signature potential to identify patients at risk of aggressive prostate cancer, and understand what the optimal treatments for those with treatment-persistent prostate cancer cells are. Citation Format: Francesco Ballesio, Sinja Taavitsainen, Mohammed Alshalalfa, Antti Kiviaho, Mazlina Ismail, Reetta Nätkin, Alexander Giesen, Thomas Munro, James A. Proudfoot, Hyunnam Ryu, Elai Davicioni, Matthew C. Cooperberg, R. Jeffrey. Karnes, Ruochen Jiang, Steven Joniau, Gerhardt Attard, Frank Claessens, Matti Nykter, Alfonso Urbanucci. Persist: a molecular signature for prostate cancer patients with preexisting treatment-persistent cells associated with aggressive disease [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Innovations in Prostate Cancer Research and Treatment; 2026 Jan 20-22; Philadelphia PA. Philadelphia (PA): AACR; Cancer Res 2026;86(2_Suppl):Abstract nr B079.

202 Background: While several PARP inhibitors are approved in combination with hormonal therapies for metastatic castrate resistant prostate cancer (CRPC), their use in castrate sensitive prostate cancer (CSPC) is understudied. We previously reported that olaparib monotherapy (without ADT) shows significant clinical activity in BRCA2 -altered patients with biochemically recurrent (BCR) prostate cancer. Here, we explored prognostic and predictive PARP-related mRNA biomarkers derived from primary prostate tumors. Methods: We characterized the expression of 16 PARP transcripts using a cohort of 52,266 radical prostatectomy (RP) specimens (2016-2024) undergoing Decipher prostate genomic classifier testing (Veracyte Inc). Transcriptome-wide mRNA expression data as well as baseline clinical/pathologic factors were retrieved from the Decipher GRID database (NCT02609269). Associations between high PARP expression (top 25%), baseline factors, and gene signatures were examined using logistic regression. We assessed the association between PARP expression and distant metastases in 3 retrospective cohorts (n= 545, 855, and 325). Finally, we evaluated PARP expression in our prior phase II trial (NCT03047135, n=39) of olaparib monotherapy in the setting of BCR following RP. Results: Higher mRNA levels of PARP1 , 2 , 8 and 14 showed strong associations (all P <0.001) with known adverse prognostic factors such as very-high Decipher score (>0.85), high Gleason grade (GG5) and non-organ confined disease (EPE, SVI and LNI), while higher PARP6 and 7 expression were associated with more favorable disease characteristics. High PARP1 expression was positively correlated with DNA-repair deficiency (r=0.77) and tumor immune microenvironment (r=0.62) signatures. In 3 independent retrospective cohorts of intermediate-high risk PCa patients, higher PARP1 expression was strongly associated with development of distant metastases after RP (HR 1.70, 1.81, and 1.67 respectively; all P <0.05). Finally, in our phase II trial of patients with BCR who received olaparib monotherapy, PARP1 (but not PARP2 ) expression from RP was 1.5-fold higher in samples with BRCA2 mutations (median 0.416 vs 0.276, P =0.01) and was associated with overall improved PSA progression-free survival (continuous variable, HR 0.55, P =0.01) and longer time to next systemic treatment (continuous variable, HR 0.66, P =0.02). Conclusions: High PARP1 mRNA expression, measured at RP, is associated with aggressive disease biology and greater risk of metastasis. However, high PARP1 (but not PARP2 ) levels are associated with improved response to PARP inhibition in the setting of BCR prostate cancer. Future trials testing PARP (including PARP1-selective) inhibitors in the CSPC space should consider measuring PARP1 mRNA levels in addition to BRCA1/2 mutation status. Clinical trial information: NCT02609269 , NCT03047135 .

410 Background: Inflammasomes are multiprotein complexes that regulate inflammation-associated signaling pathways. Although inflammation plays a crucial role in cancer cell proliferation, the specific role of inflammasomes in prostate cancer (PCa) remains underexplored. This study aims to elucidate the expression of inflammasome-related genes in PCa and assess their association with clinical outcomes. Methods: De-identified transcriptome data from a cohort of 52,266 radical prostatectomy (RP) samples tested (2016-2024) with the Decipher prostate genomic classifier (Veracyte, San Diego, CA) were retrieved from the GRID registry (NCT02609269). Expression analysis focused on 33 genes involved in inflammatory pathways. Outcomes analysis was conducted on a retrospective cohort of 855 patients treated with RP (META855), using Cox regression analysis, adjusting for baseline pathological characteristics. Results: Analysis of baseline gene expression in the GRID RP cohort revealed that most genes exhibit low baseline expression, whereas HSP90AB1, APP, TXN, and TXNIP demonstrate strong expression signals. Higher expression of most genes was associated with higher rate of Gleason grade group 4 or 5 in the GRID RP cohort. On survival analysis of the META855 cohort, higher expression (top 25%) of AIM2 and HSP90AB1 were associated with worse metastasis-free survival (p<0.05 for both). Conversely, both high and low expression levels of NLRP3 were associated with better metastasis-free survival outcomes following RP compared to average expression (p<0.05). On multivariable Cox regression analysis, adjusting for grade group, seminal vesicle involvement, lymph node involvement, and margin status, higher expression of AIM1 (HR 1.75) and HSP90AB1 (HR 1.60) were significantly associated with shorter time to metastasis following RP (p<0.05 for both). Conclusions: There is a molecular heterogeneity within pro-inflammatory genes among patients with PCa.Our findings showed thathigher expression of HSP90AB1 is linked to poorer oncological outcomes, whereas both high and low expression levels of NLRP3 are associated with better outcomes following RP.Further refinement is required to build a robust signature, along with external validation of these findings in other cohorts.

Abstract Metastasis accounts for the overwhelming majority of cancer deaths. In prostate cancer and many other solid tumors, progression to metastasis is associated with drastically reduced survival outcomes, yet the mechanisms behind this progression remain largely unknown. ATPase family AAA domain containing 2 (ATAD2) is an epigenetic reader of acetylated histones that is overexpressed in multiple cancer types and usually associated with poor patient outcomes. However, the functional role of ATAD2 in cancer progression and metastasis has been relatively understudied. Here, we employ genetically engineered mouse models of prostate cancer bone metastasis, as well as multiple independent human cohorts, to show that ATAD2 is highly enriched in bone metastasis compared with primary tumors and significantly associated with the development of metastasis. We show that ATAD2 expression is associated with MYC pathway activation in patient datasets and that, at least in a subset of tumors, MYC and ATAD2 can regulate each other’s expression. Using functional studies on mouse bone metastatic cell lines and innovative organ-on-a-chip bone invasion assays, we establish a functional role for ATAD2 inhibition in reducing prostate cancer metastasis and growth in bone. Implications: Our study highlights ATAD2 as a driver of prostate cancer progression and metastasis and suggests it may constitute a promising novel therapeutic target.

337 Background: Current risk stratification schema have limited prognostic performance in predicting outcome within National Comprehensive Cancer Network (NCCN) high-risk to very high-risk prostate cancer. Methods: Two multicenter high-risk cohorts were used for training (n = 214) and validation (n = 151) of a novel RNA microarray-based integrated clinical-genomic Classifier Optimized for Outcome in High-risk Prostate cancer (COOHP) to classify patients as COOHP favorable high-risk, standard high-risk, or very high-risk. Cox analysis was used to model metastasis-free survival (MFS), prostate cancer-specific survival (PCSS), and overall survival (OS). Model performance was compared to prior sub-classification systems using time-dependent c-indices. Results: Among NCCN high/very high-risk patients in the training cohort, 11% were classified as COOHP favorable high-risk, 70% as COOHP standard high-risk, and 18% as COOHP very high-risk. Patients with COOHP favorable high-risk disease had better rates of 5-year MFS compared to those with COOHP standard high-risk disease (94% vs 76%, hazard ratio [HR] 0.10, p = 0.02), and patients with COOHP very high-risk disease had worse 5-year MFS compared to those with COOHP standard high-risk disease (34% vs 76%, HR 3.5, p < 0.0001). Similarly, patients with COOHP very high-risk disease had worse 10-year PCSS compared to those with COOHP standard high-risk disease (36% vs 82%, HR 4.4, p < 0.0001). The c-indices for 5-year MFS and 10-year PCSS in the training cohort were 0.80 and 0.74, significantly improved compared to prior clinical and clinical-genomic risk stratification systems (0.62-0.69 for 5-year MFS and 0.56-0.63 for 10-year PCSS). These results were consistent in the validation cohort, where 5-year MFS significantly varied among the three COOHP subgroups (100% vs 89% vs 79%, p = 0.020), as did 10-year OS (100% vs 71% vs 53%, p = .040). Conclusions: A clinical-genomic risk stratification system specifically designed to discriminate prognosis in high-risk prostate cancer better identified favorable high-risk and very high-risk subsets of disease compared to prior clinical and clinical-genomic stratification systems.

295 Background: While 18F-fluciclovine PET/CT is approved in the US and recommended by the NCCN, prostate-specific membrane antigen (PSMA) PET/CT is more common in Europe/Australia and recommended by the EAU. Less is known about the biology of lesions detected by either modality. 18F-fluciclovine PET relies on radiotracer uptake by amino acid transporters LAT1-4 and ASCT1-2. PSMA PET is dependent on surface expression of PSMA. We compared relative expression of PSMA and fluciclovine transporter genes in radical prostatectomy (RP) samples to determine their distribution across subtypes and correlation with outcomes. Methods: Gene expression data of 19,102 RP samples were analyzed using the Affymetrix Human Exon 1.0 ST microarray. 1,135 patients had long term follow up. Associations between expression of PSMA and fluciclovine transporter genes (LAT1-4 and ASCT1-2) and pathologic variables, molecular subtypes, and clinical outcomes were conducted. Results: All fluciclovine transporter genes (LAT 1-4, ASCT1-2) were expressed at lower levels than PSMA (p <0.0001). PSMA expression was positively correlated with genomic risk score and pathologic Gleason score (p<0.0001), but LAT2-3 and ASCT2 were inversely correlated with genomic risk in primary tumors (p<0.0001) and less expressed in GS 9-10 tumors (p<0.0001). PSMA expression was associated with worse metastasis-free survival (MFS) (HR 1.45, p=0.001) and lymph node involvement (HR 2.14, p<0.0001). Expression of LAT2, LAT3, ASCT2 expression was associated with better MFS (HR 0.85, 0.63, 0.74, p<0.0001-0.04). After multivariable adjustment, PSMA expression remained independently prognostic of poorer MFS (HR 1.3, p=0.028). Luminal B subtype was notable for PSMA overexpression; Luminal A was enriched in ASCT2 and LAT2 (p<0.0001). PSMA expression did not correlate with ERG fusion prostate cancers, but LAT2, ASCT1, and ASCT2 were overexpressed in ERG fusion negative tumors (p<0.0001). Conclusions: PSMA expression is associated with more aggressive disease and poorer clinical outcomes than fluciclovine transporter genes in localized prostate cancer. Molecular subtypes of prostate cancer vary in PSMA and fluciclovine transporter gene expression.

BackgroundThe progression of prostate cancer is a complex, multistep process that involves molecular alterations in cells of the tumor and the microenvironment, with associated interactions between the stroma and epithelium. Genomic expression analyses of stromal infiltration markers were performed to determine the significance thereof in prostate cancer.MethodsGenome‐wide expression profiles of formalin‐fixed, paraffin‐embedded radical prostatectomy samples were evaluated from a prospective registry cohort (n = 5239) and 3 retrospective institutional cohorts (n = 1135). Two independent stromal gene expression signatures implied stromal infiltration. Cox proportional hazards regression defined the association between stromal infiltration expression and metastasis‐free survival (MFS).ResultsStromal expression scores were correlated with stromal signature genes and with other key stromal markers (CAV1, VIM, and TAGLN), basal activity, and CD3 and CD4 immune biomarkers (r > 0.5 for all). The top decile of stromal expression was associated with high genomic risk scores (Decipher ≥ 0.6) , high Cancer of the Prostate Risk Assessment–Postsurgical scores, Gleason 9 to 10 disease, and a higher risk for metastasis (hazard ratio, 2.35; 95% CI, 1.37‐4.02; P = .001). A higher stromal infiltration score was also associated with decreased expression of DNA repair genes and higher radiation sensitivity genomic scores. Postoperative radiation therapy (RT) was associated with an MFS benefit for patients with high stromal scores, but not for patients with low stromal scores (Pinteraction = .02).ConclusionsExpression of stromal infiltration markers is correlated with prostate cancer aggressiveness/progression and may be predictive of a response to RT. Stromal infiltration markers should be studied and considered for incorporation into clinical prognostication and decision making.