Lineage Plasticity In Prostate Cancer Research Articles

Single-cell analysis of treatment-resistant prostate cancer: Implications of cell state changes for cell surface antigen–targeted therapies

Targeting cell surface molecules using radioligand and antibody-based therapies has yielded considerable success across cancers. However, it remains unclear how the expression of putative lineage markers, particularly cell surface molecules, varies in the process of lineage plasticity, wherein tumor cells alter their identity and acquire new oncogenic properties. A notable example of lineage plasticity is the transformation of prostate adenocarcinoma (PRAD) to neuroendocrine prostate cancer (NEPC)-a growing resistance mechanism that results in the loss of responsiveness to androgen blockade and portends dismal patient survival. To understand how lineage markers vary across the evolution of lineage plasticity in prostate cancer, we applied single-cell analyses to 21 human prostate tumor biopsies and two genetically engineered mouse models, together with tissue microarray analysis on 131 tumor samples. Not only did we observe a higher degree of phenotypic heterogeneity in castrate-resistant PRAD and NEPC than previously anticipated but also found that the expression of molecules targeted therapeutically, namely PSMA, STEAP1, STEAP2, TROP2, CEACAM5, and DLL3, varied within a subset of gene-regulatory networks (GRNs). We also noted that NEPC and small cell lung cancer subtypes shared a set of GRNs, indicative of conserved biologic pathways that may be exploited therapeutically across tumor types. While this extreme level of transcriptional heterogeneity, particularly in cell surface marker expression, may mitigate the durability of clinical responses to current and future antigen-directed therapies, its delineation may yield signatures for patient selection in clinical trials, potentially across distinct cancer types.

FOXA2 rewires AP-1 for transcriptional reprogramming and lineage plasticity in prostate cancer

FOXA family proteins act as pioneer factors by remodeling compact chromatin structures. FOXA1 is crucial for the chromatin binding of the androgen receptor (AR) in both normal prostate epithelial cells and the luminal subtype of prostate cancer (PCa). Recent studies have highlighted the emergence of FOXA2 as an adaptive response to AR signaling inhibition treatments. However, the role of the FOXA1 to FOXA2 transition in regulating cancer lineage plasticity remains unclear. Our study demonstrates that FOXA2 binds to distinct classes of developmental enhancers in multiple AR-independent PCa subtypes, with its binding depending on LSD1. Moreover, we reveal that FOXA2 collaborates with JUN at chromatin and promotes transcriptional reprogramming of AP-1 in lineage-plastic cancer cells, thereby facilitating cell state transitions to multiple lineages. Overall, our findings underscore the pivotal role of FOXA2 as a pan-plasticity driver that rewires AP-1 to induce the differential transcriptional reprogramming necessary for cancer cell lineage plasticity.

Comprehensive data mining reveals RTK/RAS signaling pathway as a promoter of prostate cancer lineage plasticity through transcription factors and CNV

Prostate cancer lineage plasticity is a key driver in the transition to neuroendocrine prostate cancer (NEPC), and the RTK/RAS signaling pathway is a well-established cancer pathway. Nevertheless, the comprehensive link between the RTK/RAS signaling pathway and lineage plasticity has received limited investigation. In particular, the intricate regulatory network governing the interplay between RTK/RAS and lineage plasticity remains largely unexplored. The multi-omics data were clustered with the coefficient of argument and neighbor joining algorithm. Subsequently, the clustered results were analyzed utilizing the GSEA, gene sets related to stemness, multi-lineage state datasets, and canonical cancer pathway gene sets. Finally, a comprehensive exploration of the data based on the ssGSEA, WGCNA, GSEA, VIPER, prostate cancer scRNA-seq data, and the GPSAdb database was conducted. Among the six modules in the clustering results, there are 300 overlapping genes, including 3 previously unreported prostate cancer genes that were validated to be upregulated in prostate cancer through RT-qPCR. Function Module 6 shows a positive correlation with prostate cancer cell stemness, multi-lineage states, and the RTK/RAS signaling pathway. Additionally, the 19 leading-edge genes of the RTK/RAS signaling pathway promote prostate cancer lineage plasticity through a complex network of transcriptional regulation and copy number variations. In the transcriptional regulation network, TP63 and FOXO1 act as suppressors of prostate cancer lineage plasticity, whereas RORC exerts a promoting effect. This study provides a comprehensive perspective on the role of the RTK/RAS pathway in prostate cancer lineage plasticity and offers new clues for the treatment of NEPC.

Abstract 6586: ORIC-944, a potent and selective allosteric PRC2 inhibitor with best-in-class properties, demonstrates combination synergy with AR pathway inhibitors in prostate cancer models

Abstract Polycomb repressive complex 2 (PRC2) dysregulation occurs in multiple tumor types and is associated with poor prognosis in patients with prostate cancer. In patients treated with androgen receptor pathway inhibitors (ARPI), emergence of tumor cell plasticity is associated with resistance to therapy. Dysregulation of epigenetic reprogramming factors, including PRC2, creates an environment that is permissive for such lineage plasticity. Inhibition of the PRC2 complex therefore may provide an opportunity to overcome or prevent the emergence of plasticity in prostate cancer. Notably, emerging clinical trial data has demonstrated the potential of ARPI and PRC2 inhibitor combination therapy to improve outcomes in patients with metastatic prostate cancer. PRC2 tri-methylates histone H3 at lysine 27 (H3K27me3), leading to long-term transcriptional silencing, a key mechanism regulating cellular functions such as cell growth and differentiation. Three core subunits comprise PRC2: the catalytic subunit enhancer of zeste homolog 2 (EZH2), suppressor of zeste 12 (SUZ12) and embryonic ectoderm development (EED). EED is essential for the histone methyltransferase activity of PRC2. First-generation PRC2 inhibitors, which target EZH2, exhibit poor drug properties, drug-drug interaction liabilities and short half-life requiring twice daily dosing at high doses in patients. We developed a second generation PRC2 inhibitor, ORIC-944, an allosteric inhibitor of PRC2 that binds the EED subunit. ORIC-944 is a potent, highly selective, orally bioavailable inhibitor with best-in-class properties. ORIC-944 demonstrated single agent tumor growth inhibition in a spectrum of in vivo prostate cancer models, including AR-positive, AR-mutant, ARv7, ARPI-responsive and ARPI-resistant models. In vitro analysis of the combination of ARPIs and ORIC-944 showed synergy in multiple prostate cancer cells, utilizing BLISS and other quantitative methods. In vivo studies revealed that ORIC-944 demonstrated increased efficacy in combination with ARPI, consistent with the in vitro synergy. RNA-seq analysis of transcriptional changes induced by ORIC-944 provided mechanistic insight into the role of PRC2 in prostate cancer lineage plasticity and combination response. These results position ORIC-944 as a best-in-class PRC2 inhibitor for evaluation in combination with ARPI in patients with metastatic prostate cancer. A phase 1b trial of ORIC-944 is ongoing (NCT05413421). Citation Format: Anneleen Daemen, Natalie Yuen, Amber Wang, Aleksandr Pankov, Livia Ulicna, Chelsea Chen, Frank L. Duong, Jason Long, Matthew A. Marx, James G. Christensen, Lori S. Friedman, Melissa R. Junttila. ORIC-944, a potent and selective allosteric PRC2 inhibitor with best-in-class properties, demonstrates combination synergy with AR pathway inhibitors in prostate cancer models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6586.

Novel insights into RB1 in prostate cancer lineage plasticity and drug resistance.

Prostate cancer is the second most common malignancy among men in the world, posing a serious threat to men's health and lives. RB1 is the first human tumor suppressor gene to be described, and it is closely associated with the development, progression, and suppression of a variety of tumors. It was found that the loss of RB1 is an early event in prostate cancer development and is closely related to prostate cancer development, progression and treatment resistance. This paper reviews the current status of research on the relationship between RB1 and prostate cancer from three aspects: RB1 and prostate cell lineage plasticity; biological behavior; and therapeutic resistance. Providing a novel perspective for developing new therapeutic strategies for RB1-loss prostate cancer.

ADORA2A-driven proline synthesis triggers epigenetic reprogramming in neuroendocrine prostate and lung cancers.

Cell lineage plasticity is one of the major causes for the failure of targeted therapies in various cancers. However, the driver and actionable drug targets in promoting cancer cell lineage plasticity are scarcely identified. Here, we found that a G protein-coupled receptor, ADORA2A, is specifically upregulated during neuroendocrine differentiation, a common form of lineage plasticity in prostate cancer and lung cancer following targeted therapies. Activation of the ADORA2A signaling rewires the proline metabolism via an ERK/MYC/PYCR cascade. Increased proline synthesis promotes deacetylases SIRT6/7-mediated deacetylation of histone H3 at lysine 27 (H3K27), and thereby biases a global transcriptional output toward a neuroendocrine lineage profile. Ablation of Adora2a in genetically engineered mouse models inhibits the development and progression of neuroendocrine prostate and lung cancers, and, intriguingly, prevents the adenocarcinoma-to-neuroendocrine phenotypic transition. Importantly, pharmacological blockade of ADORA2A profoundly represses neuroendocrine prostate and lung cancer growth in vivo. Therefore, we believe that ADORA2A can be used as a promising therapeutic target to govern the epigenetic reprogramming in neuroendocrine malignancies.

UP60 - Integrative proteomics analysis of lineage plasticity in prostate cancer using PDX models

UP60 - Integrative proteomics analysis of lineage plasticity in prostate cancer using PDX models

ASCL1 is activated downstream of the ROR2/CREB signaling pathway to support lineage plasticity in prostate cancer

Lineage plasticity is a form of therapy-induced drug resistance. In prostate cancer, androgen receptor (AR) pathway inhibitors potentially lead to the accretion of tumor relapse with loss of AR signaling and a shift from a luminal state to an alternate program. However, the molecular and signaling mechanisms orchestrating the development of lineage plasticity under the pressure of AR-targeted therapies are not fully understood. Here, a survey of receptor tyrosine kinases (RTKs) identifies ROR2 as the top upregulated RTK following AR pathway inhibition, which feeds into lineage plasticity by promoting stem-cell-like and neuronal networks. Mechanistically, ROR2 activates the ERK/CREB signaling pathway to modulate the expression of the lineage commitment transcription factor ASCL1. Collectively, our findings nominate ROR2 as a potential therapeutic target to reverse the ENZ-induced plastic phenotype and potentially re-sensitize tumors to AR pathway inhibitors.

Abstract PR008: Molecular determinants of prostate cancer lineage plasticity

Abstract Androgen deprivation therapy (ADT) has been an effective treatment for advanced prostate cancer (PCa) for decades because PCa retains the lineage specific dependence of normal prostate tissue on androgen receptor (AR) signaling. Unfortunately, nearly all patients will progress through ADT with castrate resistant prostate cancer (CRPC). CRPC is typically associated with reactivation of AR signaling despite ADT. However with widespread clinical deployment of potent AR signaling inhibitors, an increasing fraction of CRPCs (~20) are now observed to lose AR signaling activity and show gene expression patterns consistent with alternative lineage states. These lineage variants share clonal origin with the pre-existing adenocarcinoma, so some PCa cells have sufficient plasticity to reprogram to an AR independent lineage state like neuroendocrine prostate cancer (NEPC) that is recalcitrant to available therapies. The molecular determinants of prostate cancer lineage plasticity are incompletely defined, and this knowledge gap has hindered development of diagnostic and therapeutic approaches necessary to identify and treat prostate cancer lineage plasticity. We present results from experiments testing the contribution of EZH2 and NOTCH signaling to prostate cancer lineage plasticity and NEPC reprogramming. EZH2 expression is elevated in advanced PCa, particularly NEPC, suggesting it drives lineage reprogramming. However, using genetically engineered mice and organoids we find that EZH2 is not required for NEPC reprogramming that occurs in some PCa cells in the absence of the RB1 and TP53 tumor suppressor genes. EZH2 deficiency does alter multi-lineage prostate cancer plasticity, biasing development towards lineage variants observed clinically including amphicrine and double negative prostate cancer. In contrast, data from clinical specimens indicates NOTCH signaling activity declines in NEPC compared to AR+ CRPC. NOTCH signaling suppresses NEPC development in both organoids and genetically engineered mice, and loss of NOTCH signaling is required to maintain the NEPC lineage state. Constitutive NOTCH signaling biases PCa development towards unique lineage variants including AR positive metastatic PCa with luminal differentiation. These results identify EZH2 and NOTCH signaling as molecular determinants of PCa lineage plasticity and NEPC reprogramming with implications for ongoing efforts to target these molecules for PCa therapy. Citation Format: Kristine Wadosky, Sheng-Yu Ku, Yanqing Wang, Xiaojing Zhang, Jie Wang, Jianmin Wang, Himisha Beltran, David W. Goodrich. Molecular determinants of prostate cancer lineage plasticity [abstract]. In: Proceedings of the AACR Special Conference: Advances in Prostate Cancer Research; 2023 Mar 15-18; Denver, Colorado. Philadelphia (PA): AACR; Cancer Res 2023;83(11 Suppl):Abstract nr PR008.

Abstract IA016: Epigenetic crosstalk associated with prostate cancer lineage plasticity

Abstract Background: Prostate cancer arises as an androgen driven disease and therefore androgen receptor (AR) targeting therapies have been a major focus of prostate cancer treatment. Lineage plasticity, a process by which differentiated cells lose their identity and acquire alternative lineage programs, has recently been identified as an emerging mechanism of resistance to targeted therapies in prostate cancer. This plasticity can manifest as histologic transformation from an AR-positive prostate adenocarcinoma to neuroendocrine prostate cancer (NEPC). NEPC is clinically aggressive and prognosis is poor. Although NEPC tumors arise clonally from prostate adenocarcinoma and share genomic alterations, there is significant epigenetic deregulation during the transformation process. However, mechanistically, we still do not know how these epigenetic alterations arise and how best to leverage these alterations as a therapeutic opportunity. Methods: To model DNA methylation program associated with the transition from CRPC to NEPC, we performed reduced-representation bisulfite sequencing (RRBS) in a variety of clinically relevant models including a novel genetically engineered mouse model and patient-derived organoids/xenografts (PDO/X). We performed genetic (CRISPR/Cas9 technology) and pharmacologic inhibition of DNA methylation writers (DNMTs), erasures (TETs) and polycomb repressive complex 2 histone methyltransferase EZH2 to query their role in the establishment of the DNA methylation program. To assess EZH2 enzymatic activity, we performed H3K27me3 ChIP-seq in our murine and human models. Results: The transcriptome from adenocarcinoma or NEPC foci in our murine model closely resembled clinical CRPC or NEPC transcriptome, respectively. We also found increased expression of DNA methylation regulators (DNMT1/3B and TET1) in NEPC foci. A clinically relevant methylome signature based on murine model was found to segregate clinical samples into CRPC and NEPC subtypes which was also validated in androgen-deprived isogenic LNCaP cells as well as PDO/Xs. Interestingly, AR-target genes (e.g., FKBP5 and TMPRSS2) were found to be hypermethylated and downregulated while cell fate decision regulators (e.g., FOXA2 and SLIT2) and EZH2 targets were hypomethylated and upregulated in NEPC foci. While we found that genetic or pharmacologic inhibition of DNA methylation writers and erasures impacted the NEPC-associated DNA methylation program, inhibition of EZH2 resulted in significant alterations to the DNA methylation program. In turn, we also found that that DNMT inhibition led to equally significant alterations to EZH2 activity. Conclusion: Our data suggest that there is an interplay between EZH2 and DNA methylation that is associated with the molecular reprogramming associated with the progression from AR-positive adenocarcinoma towards NEPC as well as for the maintenance of the NEPC molecular program. More mechanistic studies are now needed to fully characterize this interplay and to determine if we can harness this synergy for therapeutic potential. Citation Format: David Rickman, Richa Singh, Varadha Balaji Venkadakrishnan, Yasutaka Yamada, Himisha Beltran. Epigenetic crosstalk associated with prostate cancer lineage plasticity [abstract]. In: Proceedings of the AACR Special Conference: Advances in Prostate Cancer Research; 2023 Mar 15-18; Denver, Colorado. Philadelphia (PA): AACR; Cancer Res 2023;83(11 Suppl):Abstract nr IA016.

Abstract B013: KLF5 drives basal cell identity to promote prostate cancer lineage plasticity

Abstract The purpose of this study was to characterize the phenotypes and drivers of therapy-induced lineage plastic castration resistant prostate cancer (CRPC). Since the majority of primary prostate cancer presents with a luminal cell identity, which relies on androgen receptor (AR) signaling for growth and survival, AR-targeted therapies have become an effective method of slowing progression. However, CRPC cells can develop resistance through reduced or lost dependence on AR. These cells can transition their identity to neuroendocrine CRPC (NEPC), which lacks AR and expresses neuroendocrine lineage specific markers like chromogranin A. More frequently, these cells display transition to a cell identity that lacks AR and neuroendocrine markers and has been termed double-negative CRPC (DNPC). Identifying effective therapeutic targets to treat or prevent DNPC remains a significant clinical challenge. By utilizing prostate cancer cell lines, patient derived xenografts (PDX), and publicly available data from clinical CRPC specimens, we have identified an upregulation in basal cell identity in a subset of CRPC in response to AR-targeted therapies. Additionally, we show that the stem cell transcription factor KLF5, which is highly expressed in healthy prostate basal cells, is uniquely upregulated in CRPC subtypes displaying basal cell identity. In a cell line model of DNPC, we found that knockdown of KLF5 decreased the expression of genes that define basal cell identity. From these results, we conclude that AR-targeted therapies, while effective at targeting luminal-like adenocarcinoma, promote upregulation of KLF5 which can drive a basal cell identity and AR independence. These studies nominate KLF5 signaling as a potential therapeutic target to block the emergence of basal identity, inhibit prostate cancer lineage plasticity, and increase the durability of AR-targeted therapies. Citation Format: Samuel P. Pitzen, Yinjie Qiu, Sarah Munro, Scott M. Dehm. KLF5 drives basal cell identity to promote prostate cancer lineage plasticity [abstract]. In: Proceedings of the AACR Special Conference: Advances in Prostate Cancer Research; 2023 Mar 15-18; Denver, Colorado. Philadelphia (PA): AACR; Cancer Res 2023;83(11 Suppl):Abstract nr B013.

Abstract B017: Lineage-specific PRC2 targets and response to EZH2 inhibition in neuroendocrine prostate cancer

Abstract Lineage plasticity is an emerging mechanism of treatment-resistance in prostate cancer, which can manifest clinically as histologic transformation from prostate adenocarcinoma to small-cell neuroendocrine prostate cancer (NEPC). NEPC is associated with poor prognosis, and new treatment strategies are urgently needed. Epigenetic dysregulation has been implicated as a key driver of prostate cancer lineage plasticity, mediated in part by EZH2. EZH2 is a component of the polycomb repressive complex (PRC2) regulating the transcriptional repressive mark H3K27me3. EZH2 also controls cell-fate determination during normal development via bivalent promoters bearing both repressive H3K27me3 and active H3K4me3 marks. EZH2 is targetable, and several EZH2 inhibitors are in clinical development; these trials are currently in biomarker-unselected prostate cancer populations. A thorough understanding of the mechanism of action of EZH2 is imperative for predicting optimal response to EZH2i and for the development of robust combination treatment strategies. Cell viability studies across a diverse panel of prostate cancer models representing adenocarcinoma and NEPC indicated variable responses to tazemetostat (EZH2i) treatment. The castration-resistant prostate adenocarcinoma (CRPC) cell line LNCaP-abl showed a greater than 50% reduction in cell viability upon EZH2i (5uM) while LNCaP and 22Rv1 showed moderate response with 15-25% reduction in cell viability. However, none of our 5 NEPC patient-derived models showed significant response to EZH2i which was also validated in vivo. Hierarchical clustering of RNA-seq profiles of responder and non-responder models revealed distinct cell-type specific EZH2 targets and clusters of genes that may be associated with response to EZH2i. Approximately 15% of the EZH2 targets in the NEPC organoid WCM154 carried bivalency in their promoters including neuronal lineage determining genes such as ASCL1 and LHX2. Gene set enrichment analysis of EZH2 targets bearing bivalency in NEPC revealed association with neurogenesis and cell proliferation pathways. Further upregulation of neuronal-lineage PRC2 targets in NEPC models upon EZH2i may provide justification for lack of lineage reversal and maintenance of terminal differentiation. While there is evidence that EZH2i leads to lineage reversion in adeno-to-NEPC transitioning preclinical models, our data shows that EZH2i was associated with modest response in NEPC models and did not revert lineage plasticity. Our results provide insights into a potential role for bivalent promoters in EZH2-mediated lineage reprogramming and sustenance of terminal differentiation upon EZH2i in NEPC. Understanding lineage-specific action of EZH2i may inform biomarkers in ongoing clinical trials. Genes and pathways dysregulated because of their bivalency might also be exploited as potential candidates to be co-targeted with EZH2i. Citation Format: Varadha Balaji Venkadakrishnan, Richa Singh, Yasutaka Yamada, Kei Mizuno, Adam G. Presser, Sheng-Yu Ku, Henry Long, David Rickman, Himisha Beltran. Lineage-specific PRC2 targets and response to EZH2 inhibition in neuroendocrine prostate cancer [abstract]. In: Proceedings of the AACR Special Conference: Advances in Prostate Cancer Research; 2023 Mar 15-18; Denver, Colorado. Philadelphia (PA): AACR; Cancer Res 2023;83(11 Suppl):Abstract nr B017.

Abstract 4753: LSD1 &8211mediated FOXA2/AP1 transcription program drives lineage plasticity in prostate cancer

Abstract Background: While castration-resistant PCa (CRPC) can be further treated with second-generation androgen deprivation therapies (ADTs), the tumor can quickly generate resistance through multiple mechanisms. One critical mechanism is that tumor cells can progress to AR-indifferent stem cell-like (SCL-PCa or SCLPC) or neuroendocrine-like CRPC (NE-PCa or NEPC) through lineage plasticity. However, the underlying molecular basis remains to be determined, and clinical treatment options for these aggressive CRPC subtypes are currently limited. FOXA1 and FOXA2, which are members of the FOXA (Forkhead Box A) protein family, are pioneer transcription factors. While FOXA1 is well known for its function as a critical pioneer factor of AR and pivotal for maintaining AR signaling, the molecular function of FOXA2 in PCa cells is poorly understood despite that FOXA2 is known to be overexpressed in NEPC. Moreover, since FOXA2, like FOXA1, is currently undruggable in the clinic, there is an urgent need to decipher the molecular basis for the chromatin binding of FOXA2 and identify druggable targets that regulate FOXA2 binding and activity in the aggressive FOXA2-positive CRPC. Methods: In the current study, we first examined the role of FOXA2 in tumorigenesis and metastasis by using various in vitro and in vivo assays including mouse subcutaneous injection and zebrafish embryo injection approaches. We then conducted integrated whole genomic transcriptome and cistrome analyses in SCLPC and NEPC cell line models to characterize the activity of FOXA2 on chromatin and to identify its collaborating transcription factors that may play specific functions in promoting SCLPC or NEPC using a series of biochemical and bioinformatic approaches. Results: We found that FOXA2 silencing decreased the growth and metastasis of SCLPC and NEPC cells. Importantly, we discovered that FOXA2 chromatin binding is tightly associated with binding of JUN family proteins (primarily c-Jun) and FOXA2 silencing dramatically interrupted the global chromatin binding of c-Jun and FOSL1. The transcription targets of FOXA2/AP-1 are highly enriched for neuroendocrine and plasticity associated genes and associated with poor clinical outcomes. Furthermore, we also found that FOXA2 chromatin binding is globally enhanced by an epigenetic factor LSD1, and LSD1 inhibition can repress FOXA2/AP-1 activity in multiple CRPC models. Conclusion: Overall, our data indicate that FOXA2 functions to maintain tumor growth and metastasis in SCLPC and NEPC models. Mechanistically, FOXA2 can act as a pioneer factor of AP-1 (c-Jun/FOSL1) and reprogram AP-1 transcription activity. This FOXA2/AP-1 axis is regulated by LSD1 via demethylating FOXA2 protein and LSD1 inhibition represses FOXA2-dependent CRPC tumor progression. These findings provide novel mechanistic insights into the molecular mechanisms for PCa lineage plasticity and treatment resistance. Citation Format: Zifeng Wang, Mingyu Liu, Songqi Zhang, Muqing Li, Susan Patalano, Jill A. Macoska, Dong Han, Shuai Gao, Hansen He, Changmeng Cai. LSD1 &8211mediated FOXA2/AP1 transcription program drives lineage plasticity in prostate 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 4753.

FOXA2 Promotes Prostate Cancer Lineage Plasticity through KIT.

FOXA2 drives the adeno-to-neuroendocrine lineage transition in prostate cancer through KIT activation.

FOXA2 drives lineage plasticity and KIT pathway activation in neuroendocrine prostate cancer.

Prostate cancer adeno-to-neuroendocrine lineage transition has emerged as a mechanism of targeted therapeutic resistance. Identifying the direct molecular drivers and developing pharmacological strategies using clinical-grade inhibitors to overcome lineage transition-induced therapeutic resistance are imperative. Here, using single-cell multiomics analyses, we investigate the dynamics of cellular heterogeneity, transcriptome regulation, and microenvironmental factors in 107,201 cells from genetically engineered mouse prostate cancer samples with complete time series of tumor evolution seen in patients. We identify that FOXA2 orchestrates prostate cancer adeno-to-neuroendocrine lineage transition and that Foxa2 expression is significantly induced by androgen deprivation. Moreover, Foxa2 knockdown induces the reversal of adeno-to-neuroendocrine transition. The KIT pathway is directly regulated by FOXA2 and specifically activated in neuroendocrine prostate cancer (NEPC). Pharmacologic inhibition of KIT pathway significantly suppresses mouse and human NEPC tumor growth. These findings reveal that FOXA2 drives adeno-to-neuroendocrine lineage plasticity in prostate cancer and provides a potential pharmacological strategy for castration-resistant NEPC.

5 Oral - Lineage plasticity in prostate cancer depends on FGFR and JAK/STAT inflammatory signaling

Background: The inherent plasticity of tumor cells provides a mechanism of resistance to molecularly targeted therapies, exemplified by adeno-to-neuroendocrine lineage transitions in prostate and lung cancer. Here we investigate the root cause of lineage plasticity following Trp53 and Rb1 loss in genetically engineered mouse models, murine and patient-derived organoid cultures, and patient biospecimens with castrate-resistant prostate cancer.

Cytokines drive prostate cancer lineage plasticity.

Lineage plasticity is a critical mechanism of therapeutic resistance in cancer. In a recent issue of Science, Chan and colleagues demonstrate that early lineage plasticity in prostate cancer is driven by JAK-STAT inflammatory cytokine signaling.

Lineage plasticity in prostate cancer: Looking beyond intrinsic alterations

Emergence of small cell prostate cancer is linked to the plasticity of tumour cells and avoidance of environmental pressures. This process is thought to be reversable, however to-date evidence of this has been demonstrated in small-cell prostate cancer. To study the plasticity of prostate tumours, we look to clinical cohorts of patients covering the spectra of malignancy subtypes and utilise in vitro and in vivo models of disease progression. Current models have assisted in the understanding of the extremities of this plasticity, elucidating internal mechanisms and adaptations to stressors through transition to altered cell states. By interrogating the tumour microenvironment and earlier time points, we are beginning to form a deeper understanding of the full spectra of tumour plasticity. It could be proffered that this deeper understanding will lead to better patient outcome, with earlier interventions more likely to reverse plasticity and prevent trans-differentiation to the aggressive, small cell phenotype.

Lineage plasticity in prostate cancer depends on JAK/STAT inflammatory signaling.

Drug resistance in cancer is often linked to changes in tumor cell state or lineage, but the molecular mechanisms driving this plasticity remain unclear. Using murine organoid and genetically engineered mouse models, we investigated the causes of lineage plasticity in prostate cancer and its relationship to antiandrogen resistance. We found that plasticity initiates in an epithelial population defined by mixed luminal-basal phenotype and that it depends on increased Janus kinase (JAK) and fibroblast growth factor receptor (FGFR) activity. Organoid cultures from patients with castration-resistant disease harboring mixed-lineage cells reproduce the dependency observed in mice by up-regulating luminal gene expression upon JAK and FGFR inhibitor treatment. Single-cell analysis confirms the presence of mixed-lineage cells with increased JAK/STAT (signal transducer and activator of transcription) and FGFR signaling in a subset of patients with metastatic disease, with implications for stratifying patients for clinical trials.

The driver role of JAK-STAT signalling in cancer stemness capabilities leading to new therapeutic strategies for therapy- and castration-resistant prostate cancer.

BackgroundLineage plasticity in prostate cancer (PCa) has emerged as an important mechanism leading to the onset of therapy‐ and castration‐resistant PCa (t‐CRPC), which is closely associated with cancer stem cell (CSC) activity. This study is to identify critical driver(s) with mechanism of action and explore new targeting strategy.MethodsVarious PCa cell lines with different genetic manipulations were subjected to in vitro prostasphere assay, cell viability assay and in vivo stemness potential. In addition, bioinformatic analyses such as Ingenuity pathway and Gene Set Enrichment Analysis were carried out to determine clinical relevance. The in vivo anti‐tumour activity of JAK or STAT1 inhibitors was examined in clinically relevant t‐CRPC model.ResultsWe demonstrated the role of interferon‐related signalling pathway in promoting PCa stemness, which correlated with significant elevation of interferon related DNA damage resistance signature genes in metastatic PCa. Inhibition of JAK‐STAT1 signalling suppresses the in vitro and in vivo CSC capabilities. Mechanistically, IFIT5, a unique downstream effector of JAK‐STAT1 pathway, can facilitate the acquisition of stemness properties in PCa by accelerating the turnover of specific microRNAs (such as miR‐128 and ‐101) that can target several CSC genes (such as BMI1, NANOG, and SOX2). Consistently, knocking down IFIT5 in t‐CRPC cell can significantly reduce in vitro prostasphere formation as well as decrease in vivo tumour initiating capability.ConclusionsThis study provides a critical role of STAT1‐IFIT5 in the acquisition of PCSC and highlights clinical translation of JAK or STAT1 inhibitors to prevent the outgrowth of t‐CRPC.