Integrated single-cell analysis defines the epigenetic basis of castration-resistant prostate luminal cells

Understanding prostate response to castration and androgen receptor signaling inhibitors (ARSI) is critical to improving long-term prostate cancer (PCa) patient survival. Here, we use a multi-omics approach on 229,794 single cells to create a mouse single-cell reference atlas for interpreting mouse prostate biology and castration response. Our reference atlas refines single-cell annotations and provides a chromatin context, which, when coupled with mouse lineage tracing, demonstrates that castration-resistant luminal cells are distinct from the pre-existent urethra-proximal stem/progenitor cells. Molecular pathway analysis and therapeutic studies further implicate AP1 (JUN/FOS), WNT/β-catenin, FOXQ1, NF-κB, and JAK/STAT pathways as major drivers of castration-resistant luminal populations with relevance to human PCa. Our datasets, which can be explored through an interactive portal (https://visportal.roswellpark.org/data/tang/), can aid in developing combination treatments with ARSI for advanced PCa patients.

RNASEH2B loss and PARP inhibition in advanced prostate cancer

BACKGROUND

Clinical trials have suggested antitumor activity from PARP inhibition beyond homologous recombination deficiency (HRD). RNASEH2B loss is unrelated to HRD and preclinically sensitizes to PARP inhibition. The current study reports on RNASEH2B protein loss in advanced prostate cancer and its association with RB1 protein loss, clinical outcome and clonal dynamics during treatment with PARP inhibition in a prospective clinical trial.

METHODS

Whole tumor biopsies from multiple cohorts of patients with advanced prostate cancer were interrogated using whole-exome sequencing (WES), RNA sequencing (bulk and single nucleus) and immunohistochemistry (IHC) for RNASEH2B and RB1. Biopsies from patients treated with olaparib in the TOPARP-A and TOPARP-B clinical trials were used to evaluate RNASEH2B clonal selection during olaparib treatment.

RESULTS

Shallow co-deletion of RNASEH2B and adjacent RB1, co-located at chromosome 13q14, was common, deep co-deletion infrequent, and gene loss associated with lower mRNA expression. In castration-resistant PC (CRPC) biopsies, RNASEH2B and RB1 mRNA expression correlated, but single nucleus RNA sequencing indicated discordant loss of expression. IHC studies showed that loss of the two proteins often occurred independently, arguably due to stochastic second allele loss. Pre- and post-treatment metastatic CRPC (mCRPC) biopsy studies from BRCA1/2 wildtype tumors, treated on the TOPARP phase II trial, indicated that olaparib eradicates RNASEH2B-loss tumor subclones.

CONCLUSION

PARP inhibition may benefit men suffering from mCRPC by eradicating tumor subclones with RNASEH2B loss.

TRIAL REGISTRATION

CLINICALTRIALS

gov NCT01682772FUNDING. AstraZeneca; Cancer Research UK; Medical Research Council; Cancer Research UK; Prostate Cancer UK; Movember Foundation; Prostate Cancer Foundation.

Genome-wide association analysis of eggshell color of an F2 generation population reveals candidate genes in chickens

Eggshell color is an important visual characteristic that affects consumer preferences for eggs. Eggshell color, which has moderate to high heritability, can be effectively enhanced through molecular marker selection. Various studies have been conducted on eggshell color at specific time points. However, few longitudinal data are available on eggshell color. Therefore, the objective of this study was to investigate eggshell color using the Commission International de L'Eclairage L*a*b* system with multiple measurements at different ages (age at the first egg and at 32, 36, 40, 44, 48, 52, 56, 60, 66, and 72 weeks) within the same individuals from an F2 resource population produced by crossing White Leghorn and Dongxiang Blue chicken. Using an Affymetrix 600 single nucleotide polymorphism (SNP) array, we estimated the genetic parameters of the eggshell color trait, performed genome-wide association studies (GWASs), and screened for the potential candidate genes. The results showed that pink-shelled eggs displayed a significant negative correlation between L* values and both a* and b* values. Genetic heritability based on SNPs showed that the heritability of L*, a*, and b* values ranged from 0.32 to 0.82 for pink-shelled eggs, indicating a moderate to high level of genetic control. The genetic correlations at each time point were mostly above 0.5. The major-effect regions affecting the pink eggshell color were identified in the 10.3-13.0 Mb interval on Gallus gallus chromosome 20, and candidate genes were selected, including SLC35C2, PCIF1, and SLC12A5. Minor effect polygenic regions were identified on chromosomes 1, 6, 9, 12, and 15, revealing 11 candidate genes, including MTMR3 and SLC35E4. Members of the solute carrier family play an important role in influencing eggshell color. Overall, our findings provide valuable insights into the phenotypic and genetic aspects underlying the variation in eggshell color. Using GWAS analysis, we identified multiple quantitative trait loci (QTLs) for pink eggshell color, including a major QTL on chromosome 20. Genetic variants associated with eggshell color may be used in genomic breeding programs.

The Wnt-dependent master regulator NKX1-2 controls mouse pre-implantation development

Embryo size, specification, and homeostasis are regulated by a complex gene regulatory and signaling network. Here we used gene expression signatures of Wnt-activated mouse embryonic stem cell (mESC) clones to reverse engineer an mESC regulatory network. We identify NKX1-2 as a novel master regulator of preimplantation embryo development. We find that Nkx1-2 inhibition reduces nascent RNA synthesis, downregulates genes controlling ribosome biogenesis, RNA translation, and transport, and induces severe alteration of nucleolus structure, resulting in the exclusion of RNA polymerase I from nucleoli. In turn, NKX1-2 loss of function leads to chromosome missegregation in the 2- to 4-cell embryo stages, severe decrease in blastomere numbers, alterations of tight junctions (TJs), and impairment of microlumen coarsening. Overall, these changes impair the blastocoel expansion-collapse cycle and embryo cavitation, leading to altered lineage specification and developmental arrest.

Rarγ -Foxa1 signaling promotes luminal identity in prostate progenitors and is disrupted in prostate cancer

Retinoic acid (RA) signaling is a master regulator of vertebrate development with crucial roles in directing body axis orientation and tissue differentiation, including in the reproductive system. However, a mechanistic understanding of how RA signaling promotes cell lineage identity in different tissues is often missing. Here, leveraging prostate organoid technology, we demonstrated that RA signaling orchestrates the commitment of adult mouse prostate progenitors to glandular identity, epithelial barrier integrity, and ultimately, proper specification of the prostatic lumen. Mechanistically, RA-dependent RARγ activation promotes the expression of the pioneer factor Foxa1, which synergizes with the androgen pathway for proper luminal expansion, cytoarchitecture and function. FOXA1 nucleotide variants are common in human prostate and breast cancers and considered driver mutations, though their pathogenic mechanism is incompletely understood. Combining functional genetics experiments with structural modeling of FOXA1 folding and chromatin binding analyses, we discovered that FOXA1 F254E255 is a loss-of-function mutation leading to compromised transcriptional function and lack of luminal fate commitment of prostate progenitors. Overall, we define RA as a crucial instructive signal for glandular identity in adult prostate progenitors. We propose deregulation of vitamin A metabolism as a risk factor for benign and malignant prostate disease, and identified cancer associated FOXA1 indels affecting residue F254 as loss-of-function mutations promoting dedifferentiation of adult prostate progenitors. Summary: Retinoic acid signaling orchestrates luminal differentiation of adult prostate progenitors.

Meta-analyses of mouse and human prostate single-cell transcriptomes reveal widespread epithelial plasticity in tissue regression, regeneration, and cancer

Recent advances in single-cell RNA-sequencing (scRNA-seq) technology have facilitated studies of cell states and plasticity in tissue maintenance and cancer, including in the prostate. Here we present meta-analyses of multiple new and published scRNA-seq datasets to establish reference cell type classifications for the normal mouse and human prostate. Our analyses demonstrate transcriptomic similarities between epithelial cell states in the normal prostate, in the regressed prostate after androgen-deprivation, and in primary prostate tumors. During regression in the mouse prostate, all epithelial cells shift their expression profiles towards a proximal periurethral (PrU) state, demonstrating an androgen-dependent plasticity that is restored to normal during androgen restoration and regeneration. In the human prostate, we find progressive rewiring of transcriptional programs across epithelial cell types in benign prostate hyperplasia and treatment-naïve prostate cancer. Notably, we detect copy number variants predominantly within Luminal Acinar cells in prostate tumors, suggesting a bias in their cell type of origin, as well as a larger field of transcriptomic alterations in non-tumor cells. Finally, we observe that Luminal Acinar tumor cells in treatment-naïve prostate cancer display heterogeneous androgen receptor (AR) signaling activity, including a split between high-AR and low-AR profiles with similarity to PrU-like states. Taken together, our analyses of cellular heterogeneity and plasticity provide important translational insights into the origin and treatment response of prostate cancer.

Inactive PARP1 causes embryonic lethality and genome instability in a dominant-negative manner

PARP1 (poly-ADP ribose polymerase 1) is recruited and activated by DNA strand breaks, catalyzing the generation of poly-ADP-ribose (PAR) chains from NAD+. PAR relaxes chromatin and recruits other DNA repair factors, including XRCC1 and DNA Ligase 3, to maintain genomic stability. Here we show that, in contrast to the normal development of Parp1-null mice, heterozygous expression of catalytically inactive Parp1 (E988A, Parp1+/A) acts in a dominant-negative manner to disrupt murine embryogenesis. As such, all the surviving F1 Parp1+/A mice are chimeras with mixed Parp1+/AN (neoR retention) cells that act similarly to Parp1+/-. Pure F2 Parp1+/A embryos were found at Mendelian ratios at the E3.5 blastocyst stage but died before E9.5. Compared to Parp1-/- cells, genotype and expression-validated pure Parp1+/A cells retain significant ADP-ribosylation and PARylation activities but accumulate markedly higher levels of sister chromatid exchange and mitotic bridges. Despite proficiency for homologous recombination and nonhomologous end-joining measured by reporter assays and supported by normal lymphocyte and germ cell development, Parp1+/A cells are hypersensitive to base damages, radiation, and Topoisomerase I and II inhibition. The sensitivity of Parp1+/A cells to base damages and Topo inhibitors exceed Parp1-/- controls. The findings show that the enzymatically inactive PARP1 dominant negatively blocks DNA repair in selective pathways beyond wild-type PARP1 and establishes a crucial physiological difference between PARP1 inactivation vs. deletion. As a result, the expression of enzymatically inactive PARP1 from one allele is sufficient to abrogate murine embryonic development, providing a mechanism for the on-target side effect of PARP inhibitors used for cancer therapy.

NSD2 maintains lineage plasticity and castration-resistance in neuroendocrine prostate cancer

The clinical use of potent androgen receptor (AR) inhibitors has promoted the emergence of novel subtypes of metastatic castration-resistant prostate cancer (mCRPC), including neuroendocrine prostate cancer (CRPC-NE), which is highly aggressive and lethal 1 . These mCRPC subtypes display increased lineage plasticity and often lack AR expression 2-5 . Here we show that neuroendocrine differentiation and castration-resistance in CRPC-NE are maintained by the activity of Nuclear Receptor Binding SET Domain Protein 2 (NSD2) 6 , which catalyzes histone H3 lysine 36 dimethylation (H3K36me2). We find that organoid lines established from genetically-engineered mice 7 recapitulate key features of human CRPC-NE, and can display transdifferentiation to neuroendocrine states in culture. CRPC-NE organoids express elevated levels of NSD2 and H3K36me2 marks, but relatively low levels of H3K27me3, consistent with antagonism of EZH2 activity by H3K36me2. Human CRPC-NE but not primary NEPC tumors expresses high levels of NSD2, consistent with a key role for NSD2 in lineage plasticity, and high NSD2 expression in mCRPC correlates with poor survival outcomes. Notably, CRISPR/Cas9 targeting of NSD2 or expression of a dominant-negative oncohistone H3.3K36M mutant results in loss of neuroendocrine phenotypes and restores responsiveness to the AR inhibitor enzalutamide in mouse and human CRPC-NE organoids and grafts. Our findings indicate that NSD2 inhibition can reverse lineage plasticity and castration-resistance, and provide a potential new therapeutic target for CRPC-NE.

Immune mechanisms shape the clonal landscape during early progression of prostate cancer

Understanding the role of the immune microenvironment in modulating intratumor heterogeneity is essential for effective cancer therapies. Using multicolor lineage tracing in genetically engineered mouse models and single-cell transcriptomics, we show that slowly progressing tumors contain a multiclonal landscape of relatively homogeneous subpopulations within a well-organized tumor microenvironment. In more advanced and aggressive tumors, however, the multiclonal landscape develops into competing dominant and minor clones accompanied by a disordered microenvironment. We demonstrate that this dominant/minor landscape is associated with differential immunoediting, in which minor clones are marked by an increased expression of IFNγ-response genes and the T cell-activating chemokines Cxcl9 and Cxcl11. Furthermore, immunomodulation of the IFNγ pathway can rescue minor clones from elimination. Notably, the immune-specific gene signature of minor clones exhibits a prognostic value for biochemical recurrence-free survival in human prostate cancer. These findings suggest new immunotherapy approaches for modulating clonal fitness and tumor progression in prostate cancer.

[Deubiquitinating enzyme MINDY1 is an independent risk factor for the maintenance of stemness and poor prognosis in liver cancer cells]

Objective: To explore the key deubiquitinating enzymes that maintain the stemness of liver cancer stem cells and provide new ideas for targeted liver cancer therapy. Methods: The high-throughput CRISPR screening technology was used to screen the deubiquitinating enzymes that maintain the stemness of liver cancer stem cells. RT-qPCR and Western blot were used to analyze gene expression levels. Stemness of liver cancer cells was detected by spheroid-formation and soft agar colony formation assays. Tumor growth in nude mice was detected by subcutaneous tumor-bearing experiments. Bioinformatics and clinical samples were examined for the clinical significance of target genes. Results: MINDY1 was highly expressed in liver cancer stem cells. The expression of stem markers, the self-renewal ability of cells, and the growth of transplanted tumors were significantly reduced and inhibited after knocking out MINDY1, and its mechanism of action may be related to the regulation of the Wnt signaling pathway. The expression level of MINDY1 was higher in liver cancer tissues than that in adjacent tumors, which was closely related to tumor progression, and its high expression was an independent risk factor for a poor prognosis of liver cancer. Conclusion: The deubiquitinating enzyme MINDY1 promotes stemness in liver cancer cells and is one of the independent predictors of poor prognosis in liver cancer.

Abstract 472: HER2 as a therapeutic target in bladder cancer

Introduction: HER2 (encoded by the ERBB2 gene) is a member of the epidermal growth factor receptor (EGFR) family that exerts its activity through homo- or hetero-dimerization with other HER proteins. While multiple HER2-targeted therapies are FDA-approved for breast cancer, the clinical utility of targeting HER2 in bladder cancer patients remains undefined. We leveraged a prospective sequencing initiative and a new collection of patient-derived organoid (PDO) and xenograft (PDX) models to explore the prevalence of HER2 alterations in bladder cancers, its biologic role in bladder cancer pathogenesis and the potential clinical utility of HER2-targeted therapies.

Methods: To define the landscape of HER2 alterations in bladder cancer patients, we analyzed data generated by The Cancer Genome Atlas (TCGA) and patients enrolled in the prospective MSK-IMPACT sequencing cohort. To study the biology of HER2 alterations in a bladder cancer context, we generated PDO and PDX bladder cancer models, including ERBB2 amplified, ERBB2 hotspot mutated and ERBB2 wildtype models. Patient-derived models were characterized using a multiplatform approach and were used to study HER2 oncogenic dependence and sensitivity to multiple anti-HER2 targeted agents.

Results: The MSK-IMPACT assay revealed that ERBB2 alteration is common in bladder cancer, with a mutation frequency of 10.4% (breast cancer: 2.8%) and amplification frequency of 7.8% (breast cancer: 11.8%). ERBB2 alterations were more common in higher grade and stage bladder cancers. Among the HER2-altered PDOs, we identified some models with HER2 pathway dependence, similar to that observed in HER2 amplified breast cancer cell lines. However, most models had less dependence of downstream effector pathways such as AKT and ERK on HER2 signaling as compared to breast cancers. HER2-altered PDX models were significantly more sensitive to the HER2-targeted antibody-drug conjugate (ADC) trastuzumab deruxtecan (T-DXd) than to HER kinase inhibitor neratinib. We also observed a complete response of a HER2+ bladder cancer patient treated with T-DXd (based on PET at 7 weeks). Sensitivity to the T-DXd payload, an exatecan derivative (DXd), was found to play a key role in determining sensitivity of bladder cancer models to T-DXd.

Conclusion: Bladder cancer has higher ERBB2 mutation frequency than breast cancer, and HER2 alterations are more common in high grade and stage bladder cancers than in low-grade and non-invasive tumors, suggesting a role for HER2 in invasion and metastatic progression. The greater sensitivity of HER2 altered bladder cancer models to HER2-targeted ADC T-DXd and the complete response to T-DXd in a HER2+ bladder cancer patient provide justification for further clinical trials of HER2-targeted ADCs in bladder cancer. The sensitivity to ADC cytotoxic payload may be an important factor in determining patient response.

Citation Format: Xinran Tang, Ziyu Chen, Jasmine Thomas, Karan Nagar, John Christin, Naryan Rustgi, Sizhi Gao, Carissa Chu, Elisa De Stanchina, Michael F. Berger, Jonathan A. Coleman, Michael M. Shen, Hikmat A. Al-Ahmadie, Gopakumar V. Iyer, Kwanghee Kim, David B. Solit. HER2 as a therapeutic target in bladder cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 472.

Integrated single-cell analysis defines the epigenetic basis of castration-resistant prostate luminal cells

Understanding prostate response to castration and androgen receptor signaling inhibitors (ARSI) is critical to improving long-term prostate cancer (PCa) patient survival. Here we use a multi-omics approach on 229,794 single cells to create a mouse single-cell reference atlas better suited to interpreting mouse prostate biology and castration response. Our reference atlas refines single-cell annotations and provides chromatin context, which, when coupled with mouse lineage tracing demonstrates that the castration-resistant luminal cells are distinct from the pre-existent urethra-proximal stem/progenitor cells. Molecular pathway analysis and therapeutic studies further implicate JUN/FOS, WNT/B-Catenin, FOXQ1, NFkB, and JAK/STAT pathways as the major drivers of castration-resistant luminal populations with high relevance to human PCa. Importantly, we demonstrate the utility of our datasets, which can be explored through an interactive portal (https://visportal.roswellpark.org/data/tang/), to aid in developing novel combination treatments with ARSI for advanced PCa patients.

B7-H3 as a Therapeutic Target in Advanced Prostate Cancer

BACKGROUND

B7-H3 is a cell surface immunomodulatory glycoprotein overexpressed in prostate cancers (PCs). Understanding its longitudinal expression at emergence of castration resistance and association with tumour genomics are critical to the development of and patient selection for B7-H3 targeted therapies.

OBJECTIVE

To characterise B7-H3 expression in same-patient hormone-sensitive (HSPC) and castration-resistant (CRPC) PC biopsies, associating this with PC genomics, and to evaluate the antitumour activity of an anti-B7-H3 antibody-drug conjugate (ADC) in human CRPC in vitro and in vivo.

DESIGN, SETTING, AND PARTICIPANTS

We performed immunohistochemistry and next-generation sequencing on a cohort of 98 clinically annotated CRPC biopsies, including 72 patients who also had HSPC biopsies for analyses. We analysed two CRPC transcriptome and exome datasets, and PC scRNASeq datasets. PC organoids (patient-derived xenograft [PDX]-derived organoids [PDX-Os]) were derived from PDXs generated from human CRPC biopsies.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

We evaluated B7-H3 mRNA expression in relation to a panel of 770 immune-related genes, compared B7-H3 protein expression between same-patient HSPC and CRPC biopsies, determined associations with PC genomic alterations, and evaluated the antitumour activity of DS-7300a, a topoisomerase-1 inhibitor payload anti-B7-H3 ADC, in human PC cell lines, organoids (PDX-Os), and xenografts (PDXs) of different histologies, B7-H3 expressions, and genomics.

RESULTS AND LIMITATIONS

B7-H3 was among the most highly expressed immunomodulatory genes in CRPCs. Most CRPCs (93%) expressed B7-H3, and in patients who developed CRPC, B7-H3 expression was frequently expressed at the time of HSPC diagnosis (97%). Conversion from B7-H3 positive to negative, or vice versa, during progression from HSPC to CRPC was uncommon. CRPC with neuroendocrine features were more likely to be B7-H3 negative (28%) than adenocarcinomas. B7-H3 is overexpressed in tumours with defective DNA repair gene (ATM and BRCA2) alterations and is associated with ERG expression, androgen receptor (AR) expression, and AR activity signature. DS7300a had antitumour activity against B7-H3 expressing human PC models including cell lines, PDX-Os, and PDXs of adenocarcinoma and neuroendocrine histology.

CONCLUSIONS

The frequent overexpression of B7-H3 in CRPC compared with normal tissue and other B7 family members implicates it as a highly relevant therapeutic target in these diseases. Mechanisms driving differences in B7-H3 expression across genomic subsets warrant investigation for understanding the role of B7-H3 in cancer growth and for the clinical development of B7-H3 targeted therapies.

PATIENT SUMMARY

B7-H3, a protein expressed on the surface of the most lethal prostate cancers, in particular those with specific mutations, can be targeted using drugs that bind B7-H3. These findings are relevant for the development of such drugs and for deciding which patients to treat with these new drugs.

Compensating for gyroradius effects in beamlines with small Helmholtz coils

Measurements of lighter, low-energy charged particles in a laboratory beamline are complicated due to the influence of Earth's magnetic field. Rather than nulling out the Earth's magnetic field over the entire facility, we present a new way to correct particle trajectories using much more spatially limited Helmholtz coils. This approach is versatile and easy to incorporate in a wide range of facilities, including the existing ones, enabling measurements of low-energy charged particles in a laboratory beamline.

OncoLoop: A Network-Based Precision Cancer Medicine Framework

Prioritizing treatments for individual patients with cancer remains challenging, and performing coclinical studies using patient-derived models in real time is often unfeasible. To circumvent these challenges, we introduce OncoLoop, a precision medicine framework that predicts drug sensitivity in human tumors and their preexisting high-fidelity (cognate) model(s) by leveraging drug perturbation profiles. As a proof of concept, we applied OncoLoop to prostate cancer using genetically engineered mouse models (GEMM) that recapitulate a broad spectrum of disease states, including castration-resistant, metastatic, and neuroendocrine prostate cancer. Interrogation of human prostate cancer cohorts by Master Regulator (MR) conservation analysis revealed that most patients with advanced prostate cancer were represented by at least one cognate GEMM-derived tumor (GEMM-DT). Drugs predicted to invert MR activity in patients and their cognate GEMM-DTs were successfully validated in allograft, syngeneic, and patient-derived xenograft (PDX) models of tumors and metastasis. Furthermore, OncoLoop-predicted drugs enhanced the efficacy of clinically relevant drugs, namely, the PD-1 inhibitor nivolumab and the AR inhibitor enzalutamide.

SIGNIFICANCE

OncoLoop is a transcriptomic-based experimental and computational framework that can support rapid-turnaround coclinical studies to identify and validate drugs for individual patients, which can then be readily adapted to clinical practice. This framework should be applicable in many cancer contexts for which appropriate models and drug perturbation data are available. This article is highlighted in the In This Issue feature, p. 247.

Platr4 is an early embryonic lncRNA that exerts its function downstream on cardiogenic mesodermal lineage commitment

The mammalian genome encodes thousands of long non-coding RNAs (lncRNAs), many of which are developmentally regulated and differentially expressed across tissues, suggesting their potential roles in cellular differentiation. Despite this expression pattern, little is known about how lncRNAs influence lineage commitment at the molecular level. Here, we demonstrate that perturbation of an embryonic stem cell/early embryonic lncRNA, pluripotency-associated transcript 4 (Platr4), directly influences the specification of cardiac-mesoderm-lineage differentiation. We show that Platr4 acts as a molecular scaffold or chaperone interacting with the Hippo-signaling pathway molecules Yap and Tead4 to regulate the expression of a downstream target gene, Ctgf, which is crucial to the cardiac-lineage program. Importantly, Platr4 knockout mice exhibit myocardial atrophy and valve mucinous degeneration, which are both associated with reduced cardiac output and sudden heart failure. Together, our findings provide evidence that Platr4 is required in cardiac-lineage specification and adult heart function in mice.

Abstract 1596: Genomic heterogeneity as a barrier to precision oncology in urothelial cancer

Background: Precision oncology relies on the accurate molecular characterization of individual cancer patients at the time of treatment initiation. However, tumor molecular profiles are not static, and cancers continually evolve because of ongoing mutagenesis and clonal selection, with actionable genomic alterations potentially gained or lost during disease progression.

Methods: To define the concordance of potentially actionable genomic alterations between primary and metastatic disease sites in patients with urothelial cancer and to identify drivers of metastatic disease progression, we performed an integrated analysis of clinical and genomic data from 2,199 urothelial carcinoma patients (2,732 tumor and 331 plasma cfDNA samples) prospectively profiled at Memorial Sloan Kettering Cancer Center (MSKCC) from 2014 to 2021. Paired primary and metastatic tumor samples from individual patients were sequenced with MSK-IMPACT and/or whole-exome sequencing (WES). Plasma samples were analyzed using the MSK-ACCESS cfDNA platform.

Results: Among potentially actionable mutations (defined as OncoKB level 1-4), ERBB2 and ARID1A were associated with higher tumor grade and stage (p-value <0.001, p-value = 0.03 respectively). WES analysis of primary and metastatic tumor sites was consistent with early branched evolution with on average 42% of mutations shared between disease sites. Among chromatin-modifying genes, ARID1A has a discordant rate of 15.8%. In the 6 discordant cases, ARID1A mutation was seen exclusively in the metastatic tumor samples. This suggests a role for ARID1A mutations in metastatic disease progression. While known and likely oncogenic mutations were more likely to be concordant than variants of unknown functional significance, we observed a high degree of mutational discordance among potentially actionable genomic alterations with 23% discordant between primary and metastatic disease sites. 24% of mutations were exclusively identified by plasma cell-free DNA sequencing. Actionable mutations in cell-free DNA were more likely to be concordant with metastatic tumor biopsies than tumor tissue collected from the primary tumor site.

Conclusions: In sum, our analysis of patient-matched primary and metastatic urothelial carcinomas revealed a high degree of lesion-to-lesion genomic heterogeneity that may be a barrier to precision oncology approaches for this disease. Our data also provide a rationale for the use of cell-free DNA sequencing to guide targeted therapy selection in patients with metastatic urothelial cancer.

Citation Format: Ziyu Chen, Timothy N. Clinton, Soonbum Park, Andrew T. Lenis, Mark Donoghue, Jonathan E. Rosenberg, Bajorin F. Dean, Min Y. Teo, Bernard H. Bochner, Irina Ostrovnaya, Eugene J. Pietzak, Gopakumar V. Iyer, Sizhi Gao, Wenhuo Hu, Michael M. Shen, Michael F. Berger, Hikmat A. Al-Ahmadie, Corinne T. Abate-Shen, David B. Solit. Genomic heterogeneity as a barrier to precision oncology in urothelial 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 1596.

Abstract 2807: HER3 is an actionable target in advanced prostate cancer

Background: ERBB signaling is implicated in castration resistant prostate cancer (CRPC), but so far clinical trials of ERBB targeting drugs failed to demonstrate antitumor activity. We elected to re-investigate ERBB receptors in endocrine treatment-resistant lethal PC, hypothesizing that targeting ERBB receptors merits further evaluation in metastatic CRPC (mCRPC).

Design: We analyzed matching, same-patient, formalin-fixed paraffin-embedded (FFPE) treatment-naïve, castration-sensitive PC (CSPC) samples (n=88), and mCRPC biopsies (n=51), from patients treated at The Royal Marsden Hospital, UK. Samples were stained for HER2 and HER3 protein, by immunohistochemistry (IHC), data was generated through digital image analysis and results were analyzed against clinical characteristics and outcome data. Moreover, we treated HER3 high (CP50) and low (CP142) expressing patient derived xenograft (PDX) models with anti-HER3 antibody-drug conjugate (HER3-ADC) U3-1402 (10mg/Kg), IgG-ADC (MAAA-9289, 10mg/Kg), anti-HER3 antibody Patritumab (U3-1287, 10mg/Kg) and 10mM acetate buffer-5% sorbitol-pH 5.5 as vehicle control, in vitro and in vivo. In vitro cell growth inhibitory activity was monitored for 7-days with endpoint assay luminescence. In vivo efficacy was evaluated comparing tumor volumes, measured every 2-3 days. Statistical significance was analyzed using ANOVA with Dunnett’s multiple comparisons correction test.

Results: Membranous HER2 (mHER2) and HER3 (mHER3) proteins were detectable in both CSPC and mCRPC biopsies, with HER3 being highly expressed in many tumors. The median optical density (OD) for mHER3 expression at diagnosis was 2958.0; PC with high mHER3 expression (> median OD; n=44) had a significantly shorter median time to CRPC (20.3 vs 14.2 months; p=0.016) and worse overall survival (OS) (79.0 vs 48.8 months; p=0.04) compared to CSPC with low mHER3 (≤ median; n=44). mHER2 staining did not associate with outcome. U3-1402 demonstrated in vivo potent and sustained antitumor activity in CP50, without inducing any body weight loss or apparent toxicity. Additionally, no tumor regrowth was observed up to 60-days following the end of dosing. This anti-HER3-ADC had minimal antitumor activity in CP142, highlighting the relevance of high HER3 expression as a functional therapeutic target.

Conclusion: HER3 is commonly expressed in advanced PC and has clinical relevance in this setting. Our data indicate that HER3 is a valid target for clinical trials for men suffering from high HER3 expressing advanced PC.

Citation Format: Susana Miranda, Veronica Gil, Ruth Riisnaes, Bora Gurel, Mariantonietta D’Ambrosio, Alessandro Vasciaveo, Mateus Crespo, Ana Ferreira, Daniela Brina, Martina Troiani, Adam Sharp, Beshara Sheehan, Rossitza Christova, George Seed, Ines Figueiredo, Maryou Lambros, David Dolling, Jan Rekowski, Abdullah Alajati, Matthew Clarke, Rita Pereira, Penny Flohr, Gemma Fowler, Gunther Boysen, Semini Sumanasuriya, Diletta Bianchini, Pasquale Rescigno, Caterina Aversa, Nina Tunariu, Christina Guo, Alec Paschalis, Claudia Bertan, Lorenzo Buroni, Jian Ning, Suzanne Carreira, Paul Workman, Amanda Swain, Andrea Califano, Michael M. Shen, Andrea Alimonti, Antje Neeb, SU2C/PCF International Prostate Cancer Dream Team, Jonathan Welti, Wei Yuan, Johann de Bono. HER3 is an actionable target in advanced 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 2807.

Intra-epithelial non-canonical Activin A signaling safeguards prostate progenitor quiescence

The healthy prostate is a relatively quiescent tissue. Yet, prostate epithelium overgrowth is a common condition during aging, associated with urinary dysfunction and tumorigenesis. For over thirty years, TGF-β ligands have been known to induce cytostasis in a variety of epithelia, but the intracellular pathway mediating this signal in the prostate, and its relevance for quiescence, have remained elusive. Here, using mouse prostate organoids to model epithelial progenitors, we find that intra-epithelial non-canonical Activin A signaling inhibits cell proliferation in a Smad-independent manner. Mechanistically, Activin A triggers Tak1 and p38 ΜAPK activity, leading to p16 and p21 nuclear import. Spontaneous evasion from this quiescent state occurs upon prolonged culture, due to reduced Activin A secretion, a condition associated with DNA replication stress and aneuploidy. Organoids capable to escape quiescence in vitro are also able to implant with increased frequency into immunocompetent mice. This study demonstrates that non-canonical Activin A signaling safeguards epithelial quiescence in the healthy prostate, with potential implications for the understanding of cancer initiation, and the development of therapies targeting quiescent tumor progenitors.

Heterogeneity and complexity of the prostate epithelium: New findings from single-cell RNA sequencing studies

The recent advent of single-cell RNA-sequencing technology has provided new fundamental insights into the heterogeneity of the prostate epithelium. Several independent studies have described extensive heterogeneity of the luminal epithelial compartment, including a major division between a novel population of luminal cells located in the proximal region of the prostate ducts versus luminal cells located more distally. Proximal luminal cells as well as novel periurethral cells display increased progenitor potential in organoid culture and tissue reconstitution assays, but not in lineage-tracing analyses during prostate homeostasis, suggesting context-dependent plasticity of these populations. Here we describe and synthesize recent findings regarding the epithelial cell populations in the mouse prostate, draw comparisons to the human prostate, and address the relevance of these findings to prostate diseases and cancer.

Modeling tumor plasticity in organoid models of human cancer

Due to its inherent plasticity and heterogeneity, cancer is a difficult disease to model both in vitro and in vivo. However, recent advances in organoid technology hold great promise for future research into the mechanisms underlying tumor plasticity in human cancers.

HER3 Is an Actionable Target in Advanced Prostate Cancer

It has been recognized for decades that ERBB signaling is important in prostate cancer, but targeting ERBB receptors as a therapeutic strategy for prostate cancer has been ineffective clinically. However, we show here that membranous HER3 protein is commonly highly expressed in lethal prostate cancer, associating with reduced time to castration resistance (CR) and survival. Multiplex immunofluorescence indicated that the HER3 ligand NRG1 is detectable primarily in tumor-infiltrating myelomonocytic cells in human prostate cancer; this observation was confirmed using single-cell RNA sequencing of human prostate cancer biopsies and murine transgenic prostate cancer models. In castration-resistant prostate cancer (CRPC) patient-derived xenograft organoids with high HER3 expression as well as mouse prostate cancer organoids, recombinant NRG1 enhanced proliferation and survival. Supernatant from murine bone marrow-derived macrophages and myeloid-derived suppressor cells promoted murine prostate cancer organoid growth in vitro, which could be reversed by a neutralizing anti-NRG1 antibody and ERBB inhibition. Targeting HER3, especially with the HER3-directed antibody-drug conjugate U3-1402, exhibited antitumor activity against HER3-expressing prostate cancer. Overall, these data indicate that HER3 is commonly overexpressed in lethal prostate cancer and can be activated by NRG1 secreted by myelomonocytic cells in the tumor microenvironment, supporting HER3-targeted therapeutic strategies for treating HER3-expressing advanced CRPC. SIGNIFICANCE: HER3 is an actionable target in prostate cancer, especially with anti-HER3 immunoconjugates, and targeting HER3 warrants clinical evaluation in prospective trials.