Aggressive Variant Prostate Cancer Research Articles

Germline APC (I1307K) mutation and clinical outcomes in prostate cancer.

139 Background: The germline I1307K mutation in the adenomatous polyposis coli (APC) gene is a well-known alteration identified in approximately 6% of the Ashkenazi Jewish population. This mutation confers an increased risk of developing colorectal and other cancers. We previously reported high prevalence of aggressive variant prostate cancer (AVPC) in patients with the germline APC (I1307K) mutation. Herein, we report a larger case control analysis evaluating the hypothesis that AVPC is enriched in these patients. Methods: We reviewed records from New York University, Johns Hopkins University and Sheba Medical Center to identify patients with the APC (I1307K) mutation. Eligibility criteria included the identification of the mutation either on germline or somatic tissue testing (when germline testing was not available). AVPC was defined using previously established criteria. Combined somatic alterations in two or more of following genes were assessed: RB1, TP53, PTEN. These somatic alterations have been previously associated with AVPC. We compared cases with 21 controls with APC frameshift mutations. For categorical variables, the odds ratios (OR) for cases compared to controls are provided with 95% confidence intervals (CI). Continuous variables were summarized with descriptive statistics and compared between the case and control groups using 2-sided nonparametric Wilcoxon Rank Sum tests. Results: From 2016-2022, 18 patients at 3 institutions with the germline APC (I1307K) mutation and 21 controls at NYU with frameshift APC mutations were identified. Median ages did not differ between cases (73.5 years) and controls (71 years). At the time of analysis 13 cases (72%) and 18 (86%) controls were alive (OR: 0.43, 95% CI: 0.09, 1.24). The odds of metastatic disease among cases is 2.03 times that of controls (95% CI: 0.56, 7.32). Median PSA at diagnosis was 8 ng/mL (0.4-780) in cases and 12 ng/mL (4.7-1500) in controls. The odds of small cell histology (either on initial or subsequent biopsy) was 18 times greater than in controls (5 cases; 28% and 1 control; 5%). The odds of clinically-defined AVPC was 9.5 times greater in cases than in controls (9 cases; 50% and 2 controls; 10%, 95% CI: 1.69-53.3). In patients with metastatic disease at diagnosis 7/10 cases (70%) vs 0/9 controls had AVPC. The odds of combined somatic alterations in two or more of RB1, TP53 or PTEN was 5.1 times greater in cases than in controls (4 cases; 22% and 1 control; 5%, 95% CI: 0.58, 56.73). Conclusions: Prostate cancers that develop in the presence of the germline APC (I1307K) mutation appear to be enriched for clinically-defined and molecularly-defined AVPC compared to patients with frameshift APC mutations. The odds of combined somatic alterations in two or more of RB1, TP53 and PTEN were more common in cases than in the controls. Larger studies to identify the impact of germline APC (I1307K) mutation in the somatic genomic and epigenomic landscape of prostate cancer are ongoing.

Randomized phase II study of olaparib (Ola) maintenance following cabazitaxel-carboplatin induction chemotherapy (CabCarb) in men with aggressive variant prostate cancer (AVPC).

196 Background: An aggressive subset of prostate cancers (AVPC) respond poorly to androgen signaling inhibitors, have limited therapeutic options and a dismal prognosis. Preclinical models of AVPC display functional alterations in DNA damage response (DDR) pathways linked to platinum and PARP inhibitor (PARPi) sensitivity. We hypothesized that PARPi (ola) maintenance following CabCarb would improve the progression free survival (PFS) of men with AVPC. We performed a tissue-rich randomized trial for men with AVPC to address this hypothesis and unravel the heterogeneity of AVPC by linking genomic and transcriptomic analyses with clinical outcomes. Methods: In a single-institution study, men with CRPC meeting ≥ 1 of 9 AVPC criteria and ECOG performance status (PS) of 0-2 received 6 cycles of Cab 20-25mg/m2 and Carbo (AUC 3-4). Men completing 6 cycles without progressive disease (PD) were randomized 2:1 to Ola 300mg BID vs. observation (Obs). The primary endpoint is to estimate PFS in those randomized and we aimed to detect a difference of 3.9 vs. 7.8 months. Subgroup comparisons between patients who had PD prior to randomization (platinum-resistant) vs. those randomized (platinum sensitive) were made with chi-square tests for categorical baseline characteristics, and Kruskal-Wallis test for continuous measures. Results: 96 patients started CabCarb. Their median age was 67 years (43-86), most were white/non-Hispanic (74%), had an ECOG score of 0 (64%), bone metastases (79%), and no prior docetaxel therapy (59%). Of the 96, 7 (7.3%) went off study for reasons unrelated to PD and 36 (37.5%) had PD prior to randomization. Patients with PD prior to randomization were more likely at baseline to have received prior docetaxel (59% vs. 29%; p=0.004), have bone metastases (92% vs. 71%; p=0.03), have lower hemoglobin (11.4 vs. 12. 4; p=0.02), higher LDH (359 vs. 260; p=0.01), lower albumin (4.0 vs. 4.2; p=0.04), and higher AlkPhos (181.5 vs. 98.5; p=0.01) compared to patients who went on to randomization. With a median follow up time of 38.9 months post randomization, the median PFS was 2.3 months (95% confidence interval: 1.3, 4.6 months) for Observation and 4.9 (3.5, 6.3) months with Olaparib (p=0.12). The median OS was 16.2 (6.8, 26.4) for observation and 15.3 (10.2, 28.4) months with Olaparib (p=0.56). Conclusions: These data highlight the heterogeneity within the AVPC subset. Ongoing molecular analyses of sequential liquid and tumor tissue will illuminate the underpinnings of this heterogeneity and identify targets for additional combinatorial strategies. Clinical trial information: NCT03263650 .

Evaluation of the aggressive variant prostate cancer molecular profile (AVPCm) in CLIA environments.

250 Background: 20-30% of prostate cancers respond poorly to androgen receptor (AR)-directed therapies and have an atypical, virulent course. The aggressive variant prostate cancers ( AVPC) encompass virulent androgen indifferent tumors and are characterized by combined defects in ≥ 2/3 of TP53, RB1, and PTEN (AVPC-m). Post-hoc analysis in a phase I/II trial indicated a benefit of carboplatin+cabazitaxel in men with AVPCm+ metastatic castrate resistant prostate cancer (mCRPC). We assess the feasibility of detecting the AVPCm in CLIA-certified environments. Methods: Men with progression of mCRPC undergoing biopsies for standard molecular profiling at MD Anderson Cancer Center (MDACC) were eligible. TP53, RB1, and PTEN expression was assessed by immunohistochemistry (IHC) and read by 2 pathologists independently. Next generation sequencing of solid tumor DNA (stDNA) and circulating tumor DNA (ctDNA) was performed on the MDACC Molecular Diagnostics Laboratory and the University of Washington OncoPlex ctDNA platforms respectively . Results: Of 64 eligible patients, 49 (77%), 37 (58%), and 54 (84%) had results reported for IHC, stDNA, and ctDNA respectively. Concordance of IHC reads between pathologists was variable: Kappa 0.78, 0.67, and 0.91 for TP53, RB1, and PTEN respectively. 36 (66.7%) ctDNA samples had low tumor content, such that false negatives could not be excluded. AVPC-m was detected in 14 (29%) of patients by IHC per the original reading pathologist, 2 (5%) by stDNA NGS, and 7 (39%) by ctDNA NGS. Median turnaround times for IHC, stDNA and ctDNA were 12 (2-35), 28 (12-56) and 16 (11-56) days respectively. Conclusions: We show the operational characteristics of the AVPCm detection using CLIA certified assays. IHC detected a greater proportion of patients with AVPCm+ tumors than stDNA, likely due, partly, to the challenges of copy number loss detection. ctDNA detected the greatest proportion of AVPCm+ tumors but was not evaluable in two thirds of patients. These data serve to inform the design of clinical trials using AVPCm as a criterion for patient selection or stratification. [Table: see text]

Salvage Chemotherapy with Cisplatin, Ifosfamide, and Paclitaxel in Aggressive Variant of Metastatic Castration-Resistant Prostate Cancer.

Significant progress has been achieved in the treatment of metastatic castration-resistant prostate cancer (mCRPC). However, results in patients with aggressive variant prostate cancer (AVPC) have been disappointing. Here, we report retrospectively collected data from intensively pretreated AVPC patients (n = 17; 88.2% visceral metastases; 82% elevation of neuroendocrine markers) treated with salvage chemotherapy consisting of cisplatin, ifosfamide, and paclitaxel (TIP). At the interim analysis, 60% of patients showed radiographic response or stable disease (PFS = 2.5 months; OS = 6 months). In men who responded to chemotherapy, an OS > 15 months was observed. Preclinical analyses confirmed the high activity of the TIP regimen, especially in docetaxel-resistant prostate cancer cells. This effect was primarily mediated by increased cisplatin sensitivity in the emergence of taxane resistance. Proteomic and functional analyses identified a lower DNA repair capacity and cell cycle machinery deficiency to be causative. In contrast, paclitaxel showed inconsistent effects, partially antagonizing cisplatin and ifosfamide in some AVPC models. Consequently, paclitaxel has been excluded from the TIP combination for future patients. In summary, we report for the first time the promising efficacy of TIP as salvage therapy in AVPC. Our preclinical data indicate a pivotal role for cisplatin in overcoming docetaxel resistance.

The Emergence of Cancer Stem Cells in Early Diagnosed Prostate Cancer

The Emergence of Cancer Stem Cells in Early Diagnosed Prostate Cancer

Activation of neural lineage networks and ARHGEF2 in enzalutamide-resistant and neuroendocrine prostate cancer and association with patient outcomes

BackgroundTreatment-emergent neuroendocrine prostate cancer (NEPC) after androgen receptor (AR) targeted therapies is an aggressive variant of prostate cancer with an unfavorable prognosis. The underlying mechanisms for early neuroendocrine differentiation are poorly defined and diagnostic and prognostic biomarkers are needed.MethodsWe performed transcriptomic analysis on the enzalutamide-resistant prostate cancer cell line C4-2B MDVR and NEPC patient databases to identify neural lineage signature (NLS) genes. Correlation of NLS genes with clinicopathologic features was determined. Cell viability was determined in C4-2B MDVR and H660 cells after knocking down ARHGEF2 using siRNA. Organoid viability of patient-derived xenografts was measured after knocking down ARHGEF2.ResultsWe identify a 95-gene NLS representing the molecular landscape of neural precursor cell proliferation, embryonic stem cell pluripotency, and neural stem cell differentiation, which may indicate an early or intermediate stage of neuroendocrine differentiation. These NLS genes positively correlate with conventional neuroendocrine markers such as chromogranin and synaptophysin, and negatively correlate with AR and AR target genes in advanced prostate cancer. Differentially expressed NLS genes stratify small-cell NEPC from prostate adenocarcinoma, which are closely associated with clinicopathologic features such as Gleason Score and metastasis status. Higher ARGHEF2, LHX2, and EPHB2 levels among the 95 NLS genes correlate with a shortened survival time in NEPC patients. Furthermore, downregulation of ARHGEF2 gene expression suppresses cell viability and markers of neuroendocrine differentiation in enzalutamide-resistant and neuroendocrine cells.ConclusionsThe 95 neural lineage gene signatures capture an early molecular shift toward neuroendocrine differentiation, which could stratify advanced prostate cancer patients to optimize clinical treatment and serve as a source of potential therapeutic targets in advanced prostate cancer.

Specific classification and new therapeutic targets for neuroendocrine prostate cancer: A patient-based, diagnostic study.

Objective: Neuroendocrine prostate cancer (NEPC) is an aggressive variant of prostate cancer (PC) that may arise de novo or in patients previously treated with hormonal therapies for prostate adenocarcinoma as a mechanism of resistance. In our investigation, there appeared to be a strong correlation between neuroendocrine differentiation prostate cancer (NEDPC) and NEPC. The objectives of this study included exploring whether NEDPC is an intermediate stage in the progression of high-risk prostate cancer (HRPC) to NEPC and identifying risk factors and new targets associated with survival in the treatment of NEPC. Methods: The selected prostate cancer patients were progressed to high-risk and characterized by neuroendocrine. We collected the clinical data and characteristics of patients with three types of cancer: the incidence of metastasis, site and time of metastasis, recurrence rate, related treatment methods, etc. The similarity and differences of the three groups were compared through experiment and database. Results: By analyzing the clinical data and immunohistochemical results, we found that there seems to be a clinical feature of neuroendocrine differentiation (NED) status in between when patients progress from PC to NEPC. Finding novel treatment targets would therefore be beneficial by taking into account NEDPC as the stage of PC progression prior to NEPC. The metastasis-free survival curve and the immunohistochemical results are informing us that NEDPC can be a pre-state for diagnosing NEPC. Conclusion: NEPC is a late PC symptom that is frequently disregarded and has a bad prognosis. Finding novel treatment targets would therefore be beneficial by taking into account NEDPC as the stage of PC progression prior to NEPC.

Genotype-to-Phenotype Associations in the Aggressive Variant Prostate Cancer Molecular Profile (AVPC-m) Components.

Simple SummaryWe treat prostate cancer like it is one disease, but it is clear that it behaves like different diseases in different patients, with some having excellent responses to hormonal therapies and prolonged survivals, and others having virulent, aggressive courses and short survivals. These differences reflect different tumor biologies and therapeutic sensitivities, but the absence of molecular markers that identify each of these subsets makes it difficult to develop treatments specific to each. We found that alterations in two or more of the tumor suppressors TP53, RB1 and PTEN characterize the more virulent prostate cancers, and that patients with this molecular profile (called the aggressive variant prostate cancer molecular profile) appear to benefit more from combination chemotherapies than those without. The alterations in these markers can be determined either by staining tumor tissues or by examining their DNA. In this study, we used 28 mouse models of the human disease to assess the performance of various assays in determining these alterations. We found that although both staining and DNA sequencing are complementary, staining (which is a broadly available technique) is likely sufficient to make these determinations. Our results will inform the use of this molecular signature in clinical research and clinical practice.The aggressive variant prostate cancer molecular profile (AVPC-m), composed of combined defects in TP53, RB1 and PTEN, characterizes a subset of prostate cancers linked to androgen indifference and platinum sensitivity. To contribute to the optimization of the AVPC-m assessment for inclusion in prospective clinical trials, we investigated the status of the AVPC-m components in 28 patient tumor-derived xenografts (PDXs) developed at MDACC. We subjected single formalin-fixed, paraffin-embedded (FFPE) blocks from each PDX to immunohistochemistry (IHC), targeted next-generation genomic sequencing (NGS) and Clariom-S Affymetrix human microarray expression profiling. Standard validated IHC assays and a 10% labeling index cutoff resulted in high reproducibility across three separate laboratories and three independent readers for all tumor suppressors, as well as strong correlations with loss-of-function transcriptional scores (LOF-TS). Adding intensity assessment to labeling indices strengthened the association between IHC results and LOF-TS for TP53 and RB1, but not for PTEN. For TP53, genomic alterations determined by NGS had slightly higher agreement scores with LOF-TS than aberrant IHC, while for RB1 and PTEN, NGS and IHC determinations resulted in similar agreement scores with LOF-TS. Nonetheless, our results indicate that the AVPC-m components can be assessed reproducibly by IHC using various widely available standardized assays.

Elevated serum CEA is associated with liver metastasis and distinctive circulating tumor DNA alterations in patients with castration-resistant prostate cancer.

BackgroundElevated serum carcinoembryonic antigen (CEA) is used to identify “treatment emergent” forms of castration‐resistant prostate cancer (CRPC) such as aggressive variant prostate cancer (AVPC). However, its individual utility as a prognostic marker and the genetic alterations associated with its expression have not been extensively studied in CRPC.MethodsThis study retrospectively analyzed clinical outcomes and circulating tumor DNA profiles in 163 patients with CRPC and elevated or normal serum CEA. These same patients were then classified as AVPC or non‐AVPC and compared to determine the uniqueness of CEA‐associated gene alterations.ResultsPatients with elevated CEA demonstrated higher rates of liver metastasis (37.5% vs. 19.1%, p = 0.02) and decreased median overall survival from CRPC diagnosis (28.7 vs. 73.2 mo, p < 0.0001). In addition, patients with elevated CEA were more likely to harbor copy number amplifications (CNAs) in AR, PIK3CA, MYC, BRAF, CDK6, MET, CCNE1, KIT, RAF1, and KRAS. Based on variant allele frequency we also defined “clonal” single‐nucleotide variants (SNVs) thought to be driving disease progression in each patient and found that CEA expression was negatively correlated with clonal AR SNVs and positively correlated with clonal TP53 SNVs. Of these genetic associations, only the increases in clonal TP53 SNVs and KRAS amplifications were recapitulated among patients with AVPC when compared to patients without AVPC.ConclusionsTogether these findings suggest that CEA expression in CRPC is associated with aggressive clinical behavior and gene alterations distinct from those in AVPC.

Abstract 2896: DLL3-targeted T cell engager therapy (HPN328) for neuroendocrine prostate cancer

Abstract Background: Neuroendocrine Prostate Cancer (NEPC) is an aggressive variant of prostate cancer that can arise de novo or emerge during prostate cancer progression as a mechanism of therapy resistance. The development of effective therapies for patients with NEPC is a clinical unmet need. Delta-Like Ligand 3 (DLL3) is a negative regulator of Notch signaling and aberrantly expressed on the cell surface in the majority of NEPC and other small cell carcinomas. HPN328 is a DLL3-targeted Tri-specific T cell Activating Construct (TriTAC) that binds to DLL3 on tumor cells, CD3 on T cells, and human serum albumin. Here, we evaluated the specificity and anti-tumor activity of HPN328 in NEPC preclinical models. Methods: Immunohistochemistry (IHC) was used to evaluate DLL3 expression in prostate cancer preclinical models. We co-cultured DLL3-positive and DLL3-negative tumor cells in vitro with either human PBMCs or T cells and used CellTiter-Glo and live-cell imaging to examine tumor cell viability after the exposure to HPN328. We conducted flow cytometry to examine T cell activation. Patient-derived organoid xenografts were used to determine the anti-tumor activity of HPN328 in vivo and we applied digital spatial profiling (Nanostring) to examine effects on immune cell infiltration. Results: HPN328 suppressed cell growth and induced cell death in DLL3-positive prostate cancer organoid cell line models at a range of 0.7nM - 10nM with the presence of human T cells. Flow cytometry analysis illustrated that T cell activation markers, such as CD25, were upregulated in a dose- and time-dependent manner. In vivo studies demonstrated robust anti-tumor activity of HPN328 in causing tumor regression and stable disease after stopping the treatment in DLL3-positive models, but not in DLL3-negative models. Sustained anti-tumor effects were observed without adverse events in mice. Conclusions: The DLL3-targeted TriTAC HPN328 demonstrates robust and specific anti-tumor activity in DLL3-positive NEPC preclinical models in vitro and in vivo. T cell engagers targeting DLL3 represent a promising therapeutic strategy for NEPC. Acknowledgements: This research is funded by a Helen Trailblazers Award from the Helen Gurley Brown Foundation/DFCI Presidential Initiative (H.B.). Citation Format: Sheng-Yu Ku, Yasutaka Yamada, Patrick Ng, Laura Sun, Himisha Beltran. DLL3-targeted T cell engager therapy (HPN328) for neuroendocrine prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2896.

Abstract 818: New targets in prostate cancer: Nuclear localization of galectin-1 in androgen receptor indifferent prostate cancer

Abstract Currently, no morphological characteristics have been described in clinical specimens to delineate an androgen receptor (AR)-active from an AR-inactive phenotype in AR-expressing aggressive variant prostate cancer (AVPC). 36 localized and 51 metastatic prostate cancer (CaP) samples were analyzed - 19 (37.3%) of the metastases were in the bone, 20 (39.2%) were in the lung, while the rest were in other areas such as brain, lymph node, bladder, etc). Expression level of Gal-1 was graded individually in the nucleus and the cytoplasm of both primary and metastatic tissues. Very low Gal-1 expression was observed in epithelial cells of benign prostate, while stromal staining was strong. Localized prostate tumors obtained from prostatectomy samples showed strong gal-1 expression in the epithelial cells, but remarkably the Gal-1 staining was confined to the cytoplasm. In contrast, in metastatic tumors many nuclei stained for Gal-1. Among localized tumors, Kaplan-Meier curves showed a significant increase in metastasis formation (p=0.022) and decreased overall survival (p=0.015) among those expressing nuclear Gal-1 (n=16) compared to those with no nuclear Gal-1 (n=20). Whereas cytoplasmic Gal-1 negatively correlated with patient age (R=-0.51, p=0.008) and PSA (R=-0.41, p=0.006), and positively correlated with Ki67 (R=0.35, p=0.014), the expression of nuclear Gal-1 correlated strongly with the expression of NE markers including chromogranin A (R=0.32, p=0.031). Significantly, nuclear Gal-1 was expressed in AVPC models but not in those derived from localized tissues. Significantly, androgen deprivation, including treatment with AR antagonists, resulted in nuclear localization of Gal-1. We adapted the powerful one-bead-two-compound (OB2C) combinatorial library method for the discovery of synthetic small molecule death ligands against cancer cells in an ultra-high throughput fashion. One of these benzimidazole-based ligands, LLS80, was active against tumor cells at low micromolar IC50. Pull-down assay followed by LC MS/MS indicated that galectin-1 is the target protein of LLS80, which induced apoptosis preferentially in AVPC cells expressing high level of Gal-1. LLS80 has all the indicators of being a good therapeutic agent: (i) LLS80 has a low in vitro IC50 in AVPC cells, (ii) it shows significant in vivo anti-tumor efficacy using xenograft models, (iii) it is a novel small molecule that can penetrate AVPC cells, (iv) it can synergize with enzalutamide in vivo and in vitro, (v) it inhibits a known therapeutic target, Gal-1, and (vi) low toxicity. Treatment with LLS80 (2 µM) prevented AR antagonist-induced Gal-1 nuclear localization, and also downregulated NE markers in AVPC models of CaP progression. We conclude that nuclear Gal-1 is a novel marker of AVPC. Citation Format: Maria Malvina Tsamouri, Salma Siddiqui, Blythe P. Durbin-Johnson, Kit S. Lam, Ruiwu Liu, Paramita M. Ghosh. New targets in prostate cancer: Nuclear localization of galectin-1 in androgen receptor indifferent prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 818.

Abstract 2270: Hyperlipidemia promotes aggressive variant prostate cancer via RNA-binding protein Quaking

Abstract Introduction: Hyperlipidemia has been associated with increased risk of advanced stage and high Gleason grade prostate cancer (PCa), yet the underlying mechanism is not completely understood. Quaking (QKI) is an RNA-binding protein (RBP) that regulate lipid metabolism. For PCa, QKI overexpression has been associated with increased chance of metastatic recurrence. Method: We performed RNA sequencing of prostate cancer tissues of hyperlipidemia (n = 12) and normolipidemia (n=32). Tissue samples were acquired by MRI-US fusion targeted biopsy. DESeq2 and GSEA was used to identify differently expressed genes and enriched genesets. A web-based RBP motif screening tool TRANSITE was utilized to identify active RBPs in hyperlipidemia-associated PCa. Results: PCa samples of hyperlipidemia patients exhibited poorer histology than normolipidemia PCA. RNA sequencing found that hyperlipidemia-associated PCa is enriched of Myc-regulated genes as well as interferon or innate immunity-associated genes. Interestingly, hyperlipidemia-associated PCa gene expression signature identified PCa samples devoid of common PCa genetic alterations - TMPRSS2-ERG fusion and PTEN deletion/mutation. RBP motif screening found QKI as one of the top enriched RBP in hyperlipidemia-associated PCa transcriptome. In a separate a consecutive radical prostatectomy series (n=190), we found that QKI-high (immunohistochemistry staining score 2-3) tumors had significantly higher serum cholesterol than QKI-low (score 0-1) tumors. Overexpression and knockdown experiments proved that QKI is responsible of rapid cell proliferation and interferon-related inflammatory gene expressions, In silico analysis predicted QKI overexpressing cancer cells are susceptive to stain-mediated ferroptosis-like cell death. Mechanistically, QKI regulates expression of acyl-CoA synthetase long-chain family member 4 (ACSL4), which dictates the sensitivity of QKI overexpressing cells to ferroptosis. Conclusion: Hyperlipidemia was associated with aggressive pathologic characteristics of PCa without TMPRSS2-ERG fusion or PTEN deletion/mutation, and high tissue expression of QKI, an RNA-binding protein. QKI overexpression in PCa increased sensitivity to ACSL4-mediated ferroptosis by statins. This explains the epidemiological associations between hyperlipidemia and PCa, and will guide molecular subtype-driven drug repurposing studies. Citation Format: Hyun Ho Han, Jin Sol Sung, Dong Wook Song, Cheol Keun Park, Nam Hoon Cho, Young Deuk Choi, Woo Jin Ko. Hyperlipidemia promotes aggressive variant prostate cancer via RNA-binding protein Quaking [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2270.

Abstract 1957: Dissecting CTC phenotypic heterogeneity for predictive biomarker identification and its association with clonal lineage through single-cell multi-omic profiling

Abstract Background: The mutation, selection, and adaptation of tumor cells along disease progression exhibits a spectrum of phenotypic and genotypic heterogeneity. The importance of distinguishing phenotypic states of CTC in addition to genomic alterations has been addressed for identifying predictive biomarkers and understanding CTC biology. Current liquid biopsy usually relies on only one phenotypic state of CTCs without further genomic validation of cancer cell identity. Here, we developed HDSCA3.0, a multi-omic platform, which could distinguish various phenotypic states of CTCs followed by genomic characterization. Methods: Paired peripheral blood (PB) and bone marrow aspirate (BMA) samples were collected prospectively from 80 metastatic castrate resistant prostate cancer (mCRPC) patients for retrospective analysis. Seventy-nine of them were part of Cabazitaxel With or Without Carboplatin Trial (NCT01505868) and one independent index patient was included with aggressive disease and unfavorable prognosis. CTCs were detected, classified, enumerated through a four-channel immunostaining assay (DAPI|Cytokeratin|Vimentin|CD45/CD31) and a computational pipeline followed by manual curation, and subjected to single-cell copy-number profiling for clonality analysis and aggressive variant prostate cancer molecular signature (AVPC-MS) detection i.e. 2+ defects in PTEN, RB1, and TP53 genes. Results: CTC subtypes were categorized from Cytokeratin-positive rare cell groups based on the presence of mesenchymal features and platelet attachment. Of 79 trial cases, 77 (97.5%) had CTCs, 24 (30.4%) were positive for platelet-coated CTCs (pc.CTCs) and 25 (38.5%) of 65 sequenced patients exhibited AVPC-MS in CTCs. Survival analysis indicated that the presence of pc.CTCs identified the subset of patients who were AVPC-MS-positive with the worst prognosis. In AVPC-MS-negative patients, its presence showed significant survival improvement from combination therapy. In index patient, we uniquely identified genetically clonal mesenchymal-like CTCs (mes.CTCs) and their presence was significantly associated with one subclone emerged along clonal lineage. Meanwhile, differences of CTC abundance and phenotypic diversity were observed between paired PB and BMA as well as genomic variations. Conclusion: Our findings suggest pc.CTCs and AVPC-MS in CTCs as a multi-omic predictive biomarker to stratify mCRPC subpopulations with the worst prognosis and the most significant benefit of additional platinum therapy and illustrate a robust approach to analyze intra-patient CTC genotypic and phenotypic heterogeneity and association. Citation Format: Shoujie Chai, Nicholas Matsumoto, Ryan Storgard, Chen-Ching Peng, Ana Aparicio, Benjamin Ormseth, Kate Rappard, Cunningham Kate, Anand Kolatkar, Rafael Nevarez, Kai Han Tu, Ching-Ju Hsu, Amin Naghdloo, Paymaneh Malihi, Liya Xu, Paul Corn, Amado Zurita-Saavedra, James Hicks, Carmen Ruiz-Velasco, Peter Kuhn. Dissecting CTC phenotypic heterogeneity for predictive biomarker identification and its association with clonal lineage through single-cell multi-omic profiling [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1957.

A phase 1/2 multicenter investigator-initiated trial of DKN-01 as monotherapy or in combination with docetaxel for the treatment of metastatic castration-resistant prostate cancer (mCRPC).

5048 Background: Dickkopf-1 (DKK1) is a secreted Wnt signaling modulator that is upregulated in prostate cancers with low androgen receptor (AR) expression and co-occurring mutations in Wnt signaling family genes. DKN-01, a potent humanized monoclonal antibody (IgG4) with neutralizing activity against DKK1, delays prostate cancer growth in pre-clinical DKK1-expressing models in an NK cell dependent manner. These data provided the rationale for a prospective clinical trial testing DKN-01 in patients with mCRPC and elevated DKK1. Here, we report the safety and efficacy results of the phase 1 dose escalation cohorts. Methods: This is an investigator-initiated parallel-arm non-randomized phase 1/2 clinical trial testing DKN-01 alone or in combination with docetaxel 75 mg/m2 for men with mCRPC who progressed on ≥1 AR signaling inhibitor. Eligible patients who had progressed on or were intolerant of docetaxel were assigned to the monotherapy cohort whereas taxane-naïve patients were assigned to the DKN-01 plus docetaxel combination cohort. DKK1 status was determined by RNA in-situ expression. The primary endpoint of the phase 1 dose escalation cohorts was safety, characterized by dose-limiting toxicity (DLT). A secondary endpoint of the study was to correlate anti-tumor activity, DKK1 expression (cutoff H-score ≥ 1), and clinical evidence of aggressive variant prostate cancer (AVPC). Results: 13 pts were enrolled in the completed phase 1 portion of this study – 7 patients in the monotherapy cohort and 6 patients in the combination cohort. No DLTs were observed at DKN-01 300mg or 600mg dose levels as monotherapy or in combination with docetaxel. No treatment-related serious adverse events occurred in either cohort. A best overall response of stable disease occurred in 2 out of 7 patients in the monotherapy cohort. In the combination cohort, all 5 evaluable patients had a partial response (PR) – 3 confirmed and 2 unconfirmed. All evaluable combination patients had ≥ 50% reduction in either PSA or CEA. Confirmed PRs in the combination cohort were observed in both DKK1 low (DKK1 H-score &lt; 1) and high expressing tumors (H-score ≥1), including in 2 out of 3 patients with AVPC. Conclusions: DKN-01 600mg was well tolerated and selected as the recommended phase 2 dose as monotherapy and in combination with docetaxel. DKN-01 in combination with docetaxel showed promising clinical activity in prostate cancers regardless of DKK1 expression and was particularly promising in patients with AVPC. Further accrual into the phase 2 portion of this study is ongoing alongside preclinical and correlative studies aiming to investigate the mechanism of action of this combination therapeutic strategy. Clinical trial information: NCT03837353.

DynAMo: A dynamic allocation modular sequential trial of approved and promising therapies in men with metastatic CRPC.

5059 Background: Response to androgen signaling inhibitors is highly variable and dictates prognosis in castration resistant prostate cancer (CRPC). The development of effective combinations for CRPC has been hampered by the absence of biomarkers to identify its distinct biological subsets, obligating the homogeneous application of therapies to a heterogeneous disease in clinical trials. We previously defined the aggressive variant prostate cancers as a framework for the study of those with poor responses to androgen signaling inhibitors (dubbed ‘androgen indifferent’) and observed improved outcomes in this subset when carboplatin was added to cabazitaxel (CABCARB). In contrast, results of prospective trials suggested that anti-CTLA-4 therapy may benefit patients with androgen responsive disease. We hypothesized that said combinations applied to subsets defined by early marker declines to androgen ablation would improve overall survival (OS) over historical data in unselected CRPC. Methods: In an open-label, phase II trial (NCT02703623), men with mCRPC received abiraterone and apalutamide (ABIpAPA; Mod 1). At week 8, patients had either a ‘satisfactory’ (S) decline in PSA (≥ 50% from baseline) and CTC (≤5/7.5mL) or ‘unsatisfactory’ (US). S patients ( Mod 2) were randomized to continue ABIpAPA alone ( 2A) or with up to 4 cycles of ipilimumab (IPI, 2B). US patients ( Mod 3) continued ABIpAPA with up to 10 cycles of CABCARB. Thereafter patients continued ABIpAPA until progression. OS was calculated from entry into Mod 2 or 3. Based on historical data, the estimated median OS for men in Mod 2 and Mod 3 were 36 and 16 months respectively. Results: 195 men with CRPC were enrolled between May 2016 and August 2019. 128 (67%) were allocated to S of which 64 each were randomized to receive IPI vs. not. 3 went off study during Mod 1 without clinical decline. Of 64 patients allocated to US, 59 were treated with CABCARB on study . Men in US were more likely to have had de novo metastasis (33% vs 59%, p &lt; 0.001), RECIST measurable disease (23% vs 42%, p = 0.01), and liver metastases (3% vs 13%, p = 0.01). Differences in baseline circulating markers between the groups are shown in Table 1. Serious adverse events were reported for 3 (4.7%), 21 (33%), and 6 (10.2%) patients for M od 2A, 2B, and 3 respectively. One death due to neutropenic sepsis occurred in Mod 3. At a median follow-up of 48 months, the median (95% CI) OS in Mod2A was 44.3 (38.1, 47.7) months, 41.4 (33.3 months, not reached) in Mod 2B, and 18.7 (14.3, 36.3) months in Mod 3. Conclusions: These data substantiate the impact of underlying biology on CRPC patient outcomes and the urgent need for biomarkers that can enable the development of therapies specific to each subset. Correlative studies to identify said biomarkers will be presented. Clinical trial information: NCT02703623.

Multiple metastases of androgen indifferent prostate cancer in the urinary tract: two case reports and a literature review

BackgroundProstate cancer (PC) is mainly known to metastasize to bone, lung and liver, but isolated metastases of prostate cancer, including ductal carcinoma, in the urinary tract are very rare. We describe two patients with nodular masses in the urinary tract (the anterior urethra or the urinary bladder) that were found on cystoscopy during treatment of castration-resistant prostate cancer.Case presentationIn both cases, the pathological diagnosis from transurethral tumor resection showed that they were androgen indifferent prostate cancer (AIPC), including aggressive variant prostate cancer (AVPC) in Case 1 and treatment-induced neuroendocrine differentiation prostate cancer (NEPC) in Case 2. In Case 1, Loss of genetic heterozygosity (LOH) of BRCA2 and gene amplification of KRAS was identified from the urethra polyps. In Case 2, homozygous deletion was observed in PTEN, and LOH without mutation was observed in RB1.ConclusionThese are the first reports of two cases of urinary tract metastasis of AIPC.

Role of MicroRNAs in Neuroendocrine Prostate Cancer.

Therapy-induced neuroendocrine prostate cancer (t-NEPC/NEPC) is an aggressive variant of prostate cancer (PCa) that frequently emerges in castration-resistant prostate cancer (CRPC) under the selective pressure of androgen receptor (AR)-targeted therapies. This variant is extremely aggressive, metastasizes to visceral organs, tissues, and bones despite low serum PSA, and is associated with poor survival rates. It arises via a reversible trans-differentiation process, referred to as ‘neuroendocrine differentiation’ (NED), wherein PCa cells undergo a lineage switch and exhibit neuroendocrine features, characterized by the expression of neuronal markers such as enolase 2 (ENO2), chromogranin A (CHGA), and synaptophysin (SYP). The molecular and cellular mechanisms underlying NED in PCa are complex and not clearly understood, which contributes to a lack of effective molecular biomarkers for diagnosis and therapy of this variant. NEPC is thought to derive from prostate adenocarcinomas by clonal evolution. A characteristic set of genetic alterations, such as dual loss of retinoblastoma (RB1) and tumor protein (TP53) tumor suppressor genes and amplifications of Aurora kinase A (AURKA), NMYC, and EZH2, has been reported to drive NEPC. Recent evidence suggests that microRNAs (miRNAs) are important epigenetic players in driving NED in advanced PCa. In this review, we highlight the role of miRNAs in NEPC. These studies emphasize the diverse role that miRNAs play as oncogenes and tumor suppressors in driving NEPC. These studies have unveiled the important role of cellular processes such as the EMT and cancer stemness in determining NED in PCa. Furthermore, miRNAs are involved in intercellular communication between tumor cells and stromal cells via extracellular vesicles/exosomes that contribute to lineage switching. Recent studies support the promising potential of miRNAs as novel diagnostic biomarkers and therapeutic targets for NEPC.

Combined impact of lipidomic and genetic aberrations on clinical outcomes in metastatic castration-resistant prostate cancer

BackgroundBoth changes in circulating lipids represented by a validated poor prognostic 3-lipid signature (3LS) and somatic tumour genetic aberrations are individually associated with worse clinical outcomes in men with metastatic castration-resistant prostate cancer (mCRPC). A key question is how the lipid environment and the cancer genome are interrelated in order to exploit this therapeutically. We assessed the association between the poor prognostic 3-lipid signature (3LS), somatic genetic aberrations and clinical outcomes in mCRPC.MethodsWe performed plasma lipidomic analysis and cell-free DNA (cfDNA) sequencing on 106 men with mCRPC commencing docetaxel, cabazitaxel, abiraterone or enzalutamide (discovery cohort) and 94 men with mCRPC commencing docetaxel (validation cohort). Differences in lipid levels between men ± somatic genetic aberrations were assessed with t-tests. Associations between the 3LS and genetic aberrations with overall survival (OS) were examined using Kaplan-Meier methods and Cox proportional hazard models.ResultsThe 3LS was associated with shorter OS in the discovery (hazard ratio [HR] 2.15, 95% confidence interval [CI] 1.4-3.3, p < 0.001) and validation cohorts (HR 2.32, 95% CI 1.59–3.38, p < 0.001). Elevated plasma sphingolipids were associated with AR, TP53, RB1 and PI3K aberrations (p < 0.05). Men with both the 3LS and aberrations in AR, TP53, RB1 or PI3K had shorter OS than men with neither in both cohorts (p ≤ 0.001). The presence of 3LS and/or genetic aberration was independently associated with shorter OS for men with AR, TP53, RB1 and PI3K aberrations (p < 0.02). Furthermore, aggressive-variant prostate cancer (AVPC), defined as 2 or more aberrations in TP53, RB1 and/or PTEN, was associated with elevated sphingolipids. The combination of AVPC and 3LS predicted for a median survival of ~12 months. The relatively small sample size of the cohorts limits clinical applicability and warrants future studies.ConclusionsElevated circulating sphingolipids were associated with AR, TP53, RB1, PI3K and AVPC aberrations in mCRPC, and the combination of lipid and genetic abnormalities conferred a worse prognosis. These findings suggest that certain genotypes in mCRPC may benefit from metabolic therapies.

Germline APC (I1307K) mutation and clinical outcomes in prostate cancer.

144 Background: The germline I1307K mutation in the adenomatous polyposis coli (APC) gene is a well known alteration identified in approximately 6% of the Ashkenazi Jewish population. Individuals with this mutation have an increased risk of developing colorectal and other cancers. The implications of the APC (I1307K) mutation in patients with prostate cancer are unknown. We sought to determine the clinical outcomes of patients with prostate cancer and the germline APC (I1307K) mutation. Methods: We retrospectively reviewed records from New York University and Johns Hopkins University to identify patients with the APC (I1307K) mutation. Eligibility criteria included the identification of the mutation either on germline or somatic tissue testing (when germline testing was not available). Aggressive variant prostate cancer (AVPC) was defined using previously established criteria including: presence of small cell histology, presence of exclusively visceral metastases, bulky prostate mass or lymphadenopathy, low PSA with high-volume ( &gt; 20) bone metastases, neuroendocrine marker positivity or short interval ( &lt; 6 months) to castration resistance. Combined somatic alterations in two or more of following genes were assessed: RB1, TP53, PTEN. These somatic alterations have been previously associated with AVPC. Descriptive statistics were used to summarize patient data. Results: From 2016-2021, 13 patients with the germline APC (I1307K) mutation were identified. At the time of analysis 9 (69%) patients were alive. Most patients (7; 54%) had metastatic disease at presentation. Median PSA at diagnosis was 0.4 ng/mL (range: 0.4-20 ng/mL). The median time to castration resistance among those receiving hormonal therapy was 9 months (range: 3-13 months). Presence of small cell histology was found on initial biopsy in 3 patients and on subsequent biopsy in 1 additional patient (31% overall). Bulky prostate mass or lymphadenopathy was found in 3 (23%) patients. There were 2 (15%) patients who had low PSA with high-volume bone metastases. Four (31%) patients had radiographic progression with no concordant PSA increase. Clinically-defined AVPC was found in 7 (54%) patients and in 100% of those patients with metastatic disease. Combined somatic alterations in two or more of RB1, TP53 or PTEN were identified in 3 (23%) patients. Conclusions: Prostate cancers that develop in the presence of the germline APC (I1307K) mutation appear to be enriched for clinically-defined and molecularly-defined AVPC. Several of these patients demonstrated small cell histology and PSA-independent progression, higher than the expected background rate. This raises the hypothesis that the germline APC (I1307K) mutation influences the somatic genomic and/or epigenomic landscape of prostate cancer. Larger studies to validate the increased risk of AVPC in APC (I1307K) carriers, and to elucidate the somatic alteration landscape in these patients, are ongoing.

Chemotherapy in metastatic castration-resistant prostate cancer: Current scenario and future perspectives.

Taxanes - docetaxel and cabazitaxel - are the most active chemotherapy drugs currently used for the treatment of metastatic castration-resistant prostate cancer (mCRPC). However, despite a good initial response and survival benefit, nearly all patients eventually develop resistance, which is an important barrier to long-term survival. Resistance to taxanes is also associated with cross-resistance to androgen receptor signaling inhibitors (ARSIs). Unfortunately, other than platinum-based treatments, which have demonstrated some benefit in a subset of patients with Aggressive Variant Prostate Cancer (AVPC), few therapeutic options are available to patients progressing to taxanes. Hence, more research is required to determine whether platinum-based chemotherapy will confer a survival benefit in mCRPC, and the identification of predictive biomarkers and the clinical evaluation of platinum compounds in molecularly selected patients is an urgent but unmet clinical need. The present review focuses on the current status of chemotherapy treatments in mCRPC, interactions with androgen deprivation therapy (ADT) and novel ARSIs, and the main mechanisms of resistance. We will examine the impact of platinum-based treatments in mCRPC and summarize the known predictive biomarkers of platinum response. Finally, future approaches and avenues will be discussed.