PGC-1α drives small cell neuroendocrine cancer progression towards an ASCL1-expressing subtype with increased mitochondrial capacity

Adenocarcinomas from multiple tissues can converge to treatment-resistant small cell neuroendocrine (SCN) cancers comprised of ASCL1, POU2F3, NEUROD1, and YAP1 subtypes. We investigated how mitochondrial metabolism influences SCN cancer (SCNC) progression. Extensive bioinformatics analyses encompassing thousands of patient tumors and human cancer cell lines uncovered enhanced expression of PGC-1α, a potent regulator of mitochondrial oxidative phosphorylation (OXPHOS), across several SCNC types. PGC-1α correlated tightly with increased expression of the lineage marker ASCL1 through a positive feedback mechanism. Analyses using a human prostate tissue-based SCN transformation system showed that the ASCL1 subtype has heightened PGC-1α expression and OXPHOS activity. PGC-1α inhibition diminished OXPHOS, reduced SCNC cell proliferation, and blocked SCN prostate tumor formation. PGC-1α overexpression enhanced OXPHOS, tripled the SCN prostate tumor formation rate, and promoted commitment to the ASCL1 lineage. These findings reveal the metabolic heterogeneity among SCNC subtypes and identify PGC-1α-induced OXPHOS as a regulator of SCNC lineage plasticity.

Abstract 4104: Development of adoptive T-cell therapies to target heterogeneity of mCRPC

Metastatic castration resistant prostate cancer (mCRPC) remains a significant challenge with limited durable therapeutic responses, and innovative and effective treatment strategies are needed. Advanced mCRPC often comprises a heterogeneous population of prostate adenocarcinoma (PrAd) and neuroendocrine prostate cancer (NEPC), and current targeted therapies often result in transient anti-tumor responses. Chimeric antigen receptor (CAR) T-cell therapies are being actively investigated to target mCRPC, including CARs targeting antigens that are overexpressed in PrAd. Our group has developed a CAR T cell targeting the PrAd antigen, prostate stem cell antigen (PSCA), and have an ongoing phase 1 trial at City of Hope in patients with mCRPC. However, we anticipate that targeting NEPC in addition to PrAd will be required to achieve durable anti-tumor responses in patients. Here, we have developed novel dual-targeting approaches for the simultaneous treatment of both PrAd and NEPC. Our first approach optimizes a tandem CAR T-cell approach capable of targeting distinct antigens found on both PrAd and NEPC. Additionally, we are actively developing combinations of PSCA-CAR T-cells with secretable T-cell bispecific antibodies to target NEPC antigens. Our studies encompass the in vitro and in vivo safety and efficacy of CAR T-cells engineered to co-target PrAd and NEPC for the treatment of heterogeneous mCRPC.

Citation Format: Lupita S. Lopez, Nathanael Bangayan, Owen Witte, Saul J. Priceman. Development of adoptive T-cell therapies to target heterogeneity of mCRPC. [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 4104.

Transcriptional profiling of matched patient biopsies clarifies molecular determinants of enzalutamide-induced lineage plasticity

The androgen receptor (AR) signaling inhibitor enzalutamide (enza) is one of the principal treatments for metastatic castration-resistant prostate cancer (CRPC). Several emergent enza clinical resistance mechanisms have been described, including lineage plasticity in which the tumors manifest reduced dependency on the AR. To improve our understanding of enza resistance, herein we analyze the transcriptomes of matched biopsies from men with metastatic CRPC obtained prior to treatment and at progression (n = 21). RNA-sequencing analysis demonstrates that enza does not induce marked, sustained changes in the tumor transcriptome in most patients. However, three patients' progression biopsies show evidence of lineage plasticity. The transcription factor E2F1 and pathways linked to tumor stemness are highly activated in baseline biopsies from patients whose tumors undergo lineage plasticity. We find a gene signature enriched in these baseline biopsies that is strongly associated with poor survival in independent patient cohorts and with risk of castration-induced lineage plasticity in patient-derived xenograft models, suggesting that tumors harboring this gene expression program may be at particular risk for resistance mediated by lineage plasticity and poor outcomes.

Abstract 789: Elucidating transcriptional dynamics in neuroendocrine differentiation of advanced prostate cancer

Small cell carcinomas of the lung, bladder, and prostate share similar transcription patterns and drug sensitivities. Due to their high cellular plasticity, these cancers often escape treatment through a trans-differentiation from adenocarcinoma to the neuroendocrine state. We previously developed a pan small cell cancer in vitro/in vivo model named PARCB that can recapitulate this transition from primary patient tissues. To understand which transcription factors may be important in this transition, we conducted bulk and single cell RNA sequencing over time. We identified a developmental trajectory that is shared among all samples and is defined by stage-specific transcription factors. We plan to interrogate the role that these transcription factors play in the PARCB transformation assay. We performed ATAC sequencing to investigate how these transcription factors regulate these transitional states. Our study will provide a basic understanding of the transcriptional changes that occur during neuroendocrine differentiation and provide new potential therapeutic targets for small cell cancers.

Citation Format: Chia-Chun Chen, Kai Song, Wendy Tran, Matthew Obusan, Tyler Sugimoto, Katherine Sheu, Donghui Cheng, Grigor Varuzhanyan, Liang Wang, Lisa Ta, Zhiyuan Mao, Nathanael Bangayan, Jung-Wook Park, Thomas Graerber, Owen Witte. Elucidating transcriptional dynamics in neuroendocrine differentiation of 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 789.

Transcriptional profiling of matched biopsies reveals molecular determinants of enzalutamide resistance

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Background: Castration-resistant prostate cancer (CRPC) is the lethal form of the disease. One of the principal therapies in CRPC is the potent androgen receptor (AR) signaling inhibitor enzalutamide (enza). Most patients benefit from enza, but disease progression is nearly universal. A variety of resistance mechanisms have been described by comparing enza-naïve and enza-resistant tumors. However, these results are largely from different groups of patients and do not provide information on the changes induced by enza within a given patient. Lineage plasticity—most commonly-exemplified by loss of AR signaling and switch from a luminal to an alternate differentiation program—is a particularly aggressive resistance mechanism. Importantly, lineage plasticity appears to be increasing in incidence since more widespread use of potent AR signaling inhibitors such as enza. To improve our understanding of resistance mechanisms induced by enza treatment, we analyzed the transcriptomes of matched metastatic CRPC patient biopsies obtained prior to treatment and at the time of disease progression. Methods: All biopsies were obtained as part of the Stand Up 2 Cancer/Prostate Cancer Foundation-funded West Coast Dream Team, a prospective, IRB-approved protocol focused on understanding the biology of metastatic CRPC. We identified 21 patients for whom matched tumor biopsies with RNA-seq were available prior to starting treatment with enza and at the time of progression while still taking enza. Results: Our RNA-seq analysis demonstrates that the majority of progression tumors cluster with their baseline pair, suggesting that enza does not markedly change the tumor transcriptome in most cases. Three of 21 patients showed evidence of lineage plasticity at progression by gene expression analysis. By analyzing the RNA-seq data, we identified pathways linked to stemness that were more activated in baseline tumors from patients whose progression tumors underwent lineage plasticity. Furthermore, we identified a gene signature enriched in these baseline tumors that was associated with risk of lineage plasticity after enza treatment. We determined that high expression of this signature was strongly associated with poor survival from the time of AR signaling inhibitor treatment in independent patient samples, suggesting this signature is linked to poor patient outcome. Conclusions: Enza-resistant tumors are heterogeneous. Most tumors do not undergo significant transcriptional changes at progression vs. baseline. Matching recent reports, approximately 15% of tumors underwent lineage plasticity upon progression. Our work implicates a gene program that may predispose tumors to enza-induced lineage plasticity. Finally, the gene signature we identified may be a marker of lineage plasticity risk and tumor aggressiveness in CRPC prior to the initiation of AR signaling inhibitor therapy.

Development of allogeneic HSC-engineered iNKT cells for off-the-shelf cancer immunotherapy

Cell-based immunotherapy has become the new-generation cancer medicine, and "off-the-shelf" cell products that can be manufactured at large scale and distributed readily to treat patients are necessary. Invariant natural killer T (iNKT) cells are ideal cell carriers for developing allogeneic cell therapy because they are powerful immune cells targeting cancers without graft-versus-host disease (GvHD) risk. However, healthy donor blood contains extremely low numbers of endogenous iNKT cells. Here, by combining hematopoietic stem cell (HSC) gene engineering and in vitro differentiation, we generate human allogeneic HSC-engineered iNKT (AlloHSC-iNKT) cells at high yield and purity; these cells closely resemble endogenous iNKT cells, effectively target tumor cells using multiple mechanisms, and exhibit high safety and low immunogenicity. These cells can be further engineered with chimeric antigen receptor (CAR) to enhance tumor targeting or/and gene edited to ablate surface human leukocyte antigen (HLA) molecules and further reduce immunogenicity. Collectively, these preclinical studies demonstrate the feasibility and cancer therapy potential of AlloHSC-iNKT cell products and lay a foundation for their translational and clinical development.

The DNA methylation landscape of advanced prostate cancer

Although DNA methylation is a key regulator of gene expression, the comprehensive methylation landscape of metastatic cancer has never been defined. Through whole-genome bisulfite sequencing paired with deep whole-genome and transcriptome sequencing of 100 castration-resistant prostate metastases, we discovered alterations affecting driver genes only detectable with integrated whole-genome approaches. Notably, we observed that 22% of tumors exhibited a novel epigenomic subtype associated with hyper-methylation and somatic mutations in TET2, DNMT3B, IDH1, and BRAF. We also identified intergenic regions where methylation is associated with RNA expression of the oncogenic driver genes AR, MYC and ERG. Finally, we showed that differential methylation during progression preferentially occurs at somatic mutational hotspots and putative regulatory regions. This study is a large integrated study of whole-genome, whole-methylome and whole-transcriptome sequencing in metastatic cancer and provides a comprehensive overview of the important regulatory role of methylation in metastatic castration-resistant prostate cancer.

The comprehensive methylation landscape of metastatic castration-resistant prostate cancer (mCRPC) identifies new phenotypic subtypes: Results from the West Coast Prostate Cancer Dream Team (WCDT)

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Background: While recent studies have delineated the genomic landscape of mCRPC, its epigenomic landscape has not been as well characterized. The goal of this study was to define the comprehensive methylation landscape of mCRPC. Methods: mCRPC patients (pts) underwent a metastasis biopsy as part of a multi-institutional study (NCT02432001). Deep whole-genome bisulfite sequencing (mean depth 46x) was performed on fresh frozen tissue from 100 mCRPC patients; data was paired with deep whole-genome and transcriptome sequencing from the same samples. Unbiased hierarchical clustering of the mCRPC methylome was undertaken, and the survival of patients in each cluster was calculated using the Kaplan Meier method. Results: Unbiased hierarchical clustering revealed several distinct subtypes. 22% of mCRPC samples exhibited a novel epigenomic subtype associated with hyper-methylation. This hypermethylated (HM) cluster was significantly associated with somatic mutations in genes known to be involved in methylation, eg TET2 and DNMT3B, as well as in genes in which mutations have been associated with hyper-methylation in other cancer types ( IDH1 in glioblastoma and BRAF in colon cancer). mCRPC survival was 56.1 mos in pts with HM cancers compared to 35.6 mos in non-HM (p = .055). Methylome clustering also identified a unique cluster comprised of all patients with treatment-induced small cell/neuroendocrine cancer, a subtype previously associated with poor survival. Conclusions: This integrated study of whole-genome, whole methylome and whole-transcriptome sequencing provides the first comprehensive overview of the important regulatory role of methylation in metastatic castration-resistant prostate cancer, and has identified at least two distinct subtypes. The clinical and therapeutic implications of methylation subtypes should be explored in future studies. Clinical trial information: NCT02432001 .

Genomic Hallmarks and Structural Variation in Metastatic Prostate Cancer

While mutations affecting protein-coding regions have been examined across many cancers, structural variants at the genome-wide level are still poorly defined. Through integrative deep whole-genome and -transcriptome analysis of 101 castration-resistant prostate cancer metastases (109X tumor/38X normal coverage), we identified structural variants altering critical regulators of tumorigenesis and progression not detectable by exome approaches. Notably, we observed amplification of an intergenic enhancer region 624 kb upstream of the androgen receptor (AR) in 81% of patients, correlating with increased AR expression. Tandem duplication hotspots also occur near MYC, in lncRNAs associated with post-translational MYC regulation. Classes of structural variations were linked to distinct DNA repair deficiencies, suggesting their etiology, including associations of CDK12 mutation with tandem duplications, TP53 inactivation with inverted rearrangements and chromothripsis, and BRCA2 inactivation with deletions. Together, these observations provide a comprehensive view of how structural variations affect critical regulators in metastatic prostate cancer.

Motor-cognitive dual-task performance: effects of a concurrent motor task on distinct components of visual processing capacity

Dual tasking, or the simultaneous execution of two continuous tasks, is frequently associated with a performance decline that can be explained within a capacity sharing framework. In this study, we assessed the effects of a concurrent motor task on the efficiency of visual information uptake based on the 'theory of visual attention' (TVA). TVA provides parameter estimates reflecting distinct components of visual processing capacity: perceptual threshold, visual processing speed, and visual short-term memory (VSTM) storage capacity. Moreover, goodness-of-fit values and bootstrapping estimates were derived to test whether the TVA-model is validly applicable also under dual task conditions, and whether the robustness of parameter estimates is comparable in single- and dual-task conditions. 24 subjects of middle to higher age performed a continuous tapping task, and a visual processing task (whole report of briefly presented letter arrays) under both single- and dual-task conditions. Results suggest a decline of both visual processing capacity and VSTM storage capacity under dual-task conditions, while the perceptual threshold remained unaffected by a concurrent motor task. In addition, goodness-of-fit values and bootstrapping estimates support the notion that participants processed the visual task in a qualitatively comparable, although quantitatively less efficient way under dual-task conditions. The results support a capacity sharing account of motor-cognitive dual tasking and suggest that even performing a relatively simple motor task relies on central attentional capacity that is necessary for efficient visual information uptake.

Targeting Adaptive Pathways in Metastatic Treatment-Resistant Prostate Cancer: Update on the Stand Up 2 Cancer/Prostate Cancer Foundation-Supported West Coast Prostate Cancer Dream Team

The Stand Up 2 Cancer/Prostate Cancer Foundation-funded West Coast Dream Team project is a prospective multi-institutional study focused on acquiring metastatic castration-resistant prostate cancer (mCRPC) biopsy tissue at the time of resistance to abiraterone or enzalutamide. It is the first large-scale study designed to analyze mCRPC tissue specifically in this patient population. Study accrual is on target, with 261 out of a planned 300 metastatic tumor biopsies performed by August 2016. Paired biopsies have been completed in 42 patients, with paired genomic data before and after therapy obtained in 26 cases. Accrual is expected to be complete by December 2016.

Abstract 5183: Identification and characterization of wild type kinases driving prostate cancer metastasis

Despite numerous oncogenic alterations implicated in metastatic prostate cancer, mutations or DNA amplifications of kinases are rare. We previously demonstrated that 1) expression of wild type (wt) Src in combination with the androgen receptor synergizes to produce aggressive prostate adenocarcinoma, 2) tyrosine phosphorylation increases with prostate cancer stage, and 3) the phosphoproteomic profile of metastatic prostate cancer is different from localized disease. However, the question still remains as to whether wt kinases can drive prostate cancer metastasis and should be regarded as therapeutic targets. To identify wt kinases driving prostate cancer metastasis, we performed phospho-tyrosine, threonine and serine peptide enrichment and quantitative mass spectrometry on metastatic prostate cancer tissues obtained at rapid autopsy. Analysis of this phosphoproteomic dataset combined with bioinformatic analyses of genomic datasets identified ∼140 kinases differentially expressed or activated in prostate cancer metastases. To determine which of these kinases function to promote prostate cancer metastasis, we developed an in vitro and in vivo metastasis screen. Out of 140 kinases, 20 kinases promote resistance to anoikis in vitro and metastatic colonization in vivo. Positive kinases include Src, Lyn, and EGFR which have been previously reported to be important in prostate cancer metastasis and thus provide strength to the validity of our screen. In addition we identified kinases with uncharacterized roles in prostate cancer metastasis and of particular interest, several of these kinases promote bone metastasis. We expect our findings will improve our understanding of the mechanistic role of kinase activation in prostate cancer and identify promising new therapeutic targets for metastatic disease.

Citation Format: Claire Faltermeier, Justin Drake, Peter Clark, Bryan Smith, Colleen Mathis, Yang Zong, Carmen Volpe, Owen Witte. Identification and characterization of wild type kinases driving prostate cancer metastasis. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5183. doi:10.1158/1538-7445.AM2015-5183

Abstract 4985: Notch1 as a key mediator in promoting advanced castration-resistant prostate cancer

The first line of treatment for men with advanced prostate cancers is androgen deprivation therapy. However, the disease commonly relapses in its lethal metastatic form referred to as castration-resistant prostate cancer (CRPC). CRPC is the primary cause of prostate cancer specific mortality in men. Current therapies including chemotherapeutic agents improve median overall survival by only few months. The mechanisms that distinguish clinically localized indolent tumors from lethal CRPC are unclear. Here we demonstrate that ectopic expression of Notch1 promotes progression to poorly differentiated carcinoma when combined with pathways that are altered in advanced disease but are insufficient to drive aggressive prostate cancer alone. Notch1 driven tumors are resistant to androgen deprivation. Transcriptional profiling reveals that these tumors display features of epithelial to mesenchymal transition, a morphological change associated with tumor aggressiveness and metastasis. Our study provides the first functional evidence that Notch1 signaling axis is a key mediator in promoting advanced prostate cancer and may represent a new therapeutic target for the advanced disease.

Note: This abstract was not presented at the meeting.

Citation Format: Tanya Stoyanova, Claire Faltermeier, Bryan Smith, Andrew Goldstein, Xi Zhang, Justin Drake, John Lee, Sandra Orellana, Steven Blum, Donghui Cheng, Kenneth Pienta, Jiaoti Huang, Owen Witte. Notch1 as a key mediator in promoting advanced castration-resistant prostate cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4985. doi:10.1158/1538-7445.AM2015-4985

Abstract 3021: Roles of EMT on stem cell properties of prostate stem and cancer cells during castration-resistant prostate cancer progression

Androgen ablation remains the mainstay of treatment for men with advanced and metastatic prostate cancer. However, despite the introduction of new generation anti-androgens, a majority of men succumb to castration resistant prostate cancer (CRPC). The molecular mechanisms governing the emergence of treatment resistance in CRPC patients are not well understood. Recent experience suggests that tumor regeneration from castration-resistant stem-like cells induce resistance to hormonal therapy. Therefore, elucidating novel targets essential for driving stem-like activity is critical to prevent and defeat CRPC. It has been shown that normal and cancer stem cells exploit normal development process of epithelial-mesenchymal transition (EMT) to survive and metastasize, and that EMT confer stem cell properties to more differentiated cancer cell progeny in breast and other cancers. However, it is unclear if EMT is linked with stem cells in normal and malignant prostate. Our lab has reported that N-cadherin, a marker of EMT, is upregulated after neoadjuvant hormone ablation and in CRPC and is sufficient to cause metastasis and CRPC. Therapeutic targeting of N-cadherin by novel N-cadherin antibody inhibited metastatic and CRPC progression. The cell population displaying N-cadherin co-expressed a number of stem cell-associated genes in CRPC models. Here, we verified EMT linked to stem cells in both normal prostate and CRPC. We found in LAPC-9 CRPC tumors, the cell population expressing N-cadherin behaved like stem cells with enhanced sphere-forming ability, which could be specifically inhibited by novel N-cadherin antibody 2A9. We isolated stem-like CD49fhi/Trop2hi cells from prostatectomy specimens and found that forced N-cadherin expression promoted sphere formation of those cells. Our evaluation of gene expression in N-cadherin-positive prostate cancer cell lines and CRPC tumors demonstrated that N-cadherin expression activated common EMT transcriptional regulators including Zeb1. We asked if Zeb1 regulated stem cell properties in normal and malignant prostate. We found that forced Zeb1 expression induced EMT with enhanced cell invasiveness in LNCaP human prostate cancer cells. However, Zeb1 overexpression inhibited cell proliferation and CRPC tumor growth of LNCaP. Zeb1 overexpression also surprisingly inhibited sphere formation of normal stem/progenitor cells from prostatectomy specimens. Our data suggest that Zeb1-regulated EMT promotes both quiescence and invasiveness in normal and malignant prostate in which the quiescent cells may survive and play a role in treatment resistance, while N-cadherin mediates stem cell proliferation and self-renewal. Our research will likely provide useful information of EMT-related biomarkers for preventing and developing efficient therapeutics to combat the treatment resistance to new generation anti-androgens.

Citation Format: Shu Lin, Evelyn Kono, Joyce Yamashiro, Sean Lee, Owen Witte, Andrew Goldstein, Robert E. Reiter. Roles of EMT on stem cell properties of prostate stem and cancer cells during castration-resistant prostate cancer progression. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3021. doi:10.1158/1538-7445.AM2014-3021

The molecular and pathway characterization of patients with metastatic castration resistant prostate cancer (mCRPC) refractory to therapy with abiraterone acetate or enzalutamide: Preliminary results from the SU2C/PCF/AACR West Coast Prostate Cancer Dream Team (WCDT)

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Background: Progressive metastatic castration resistant prostate cancer (mCRPC) has historically been challenging to biopsy and characterize on a molecular basis because of its bone tropism. Since mechanisms of resistance to androgen signaling inhibitors such as enzalutamide or abiraterone are not fully understood, both an unbiased and a targeted assessment of the molecular landscape of these patients is required. Methods: Patients (pts) with mCRPC undergo biopsy at one of five West Coast Prostate Cancer Dream Team (WCDT) clinical sites, using a uniform biopsy protocol, following central radiologic review. Tissue is both frozen, and formalin fixed/paraffin embedded (FFPE). Frozen tissue undergoes laser capture microdissection (LCM) for RNA seq, DNA seq, and array comparative genomic hybridization (aCGH). An RNA seq process was developed that allows using extremely small quantities of RNA (approximately 1 ng). FFPE tissue undergoes a CLIA-certified assessment of a 37-gene mutational panel, FISH for AR, and IHC for PTEN. Peripheral blood is collected for miRNA, immune responses, and CTC analysis including aCGH. Pathway assessment integrating clinical, RNA seq, DNA seq, aCGH data is undertaken using PARADIGM analysis. Results: Thirty six of 300 planned mCRPC pts have undergone a metastasis biopsy: 17 from bone, eight from liver, one from lung, and 10 from distant lymph nodes. Tumor is present in around 75% of the frozen specimens. To date, LCM has been undertaken in 11 samples, with RNA seq done in six, DNA whole exome seq in one, aCGH in four. FFPE tissue has been evaluated by mutational panel sequencing (n=9), FISH for AR (n=11), and IHC for PTEN (n=13). CTC have been isolated in 33 pts. aCGH has been successfully undertaken in paired CTC and biopsy specimens. Expression data from patients with full RNA sequencing have been analyzed by PARADIGM, with top disrupted pathways identified. Conclusions: Biopsies of mCRPC, including from bony sites, can be undertaken and used for molecular and pathway analysis. Sufficient tissue for unbiased and targeted assessment can be obtained. Linkage of results from these studies to the clinical characteristics of these patients will reveal important insights into mechanisms of resistance.

Application of a rapid, simple, and accurate adenovirus-based method to compare PET reporter gene/PET reporter probe systems

PURPOSE

This study aims to use a simple, quantitative method to compare the HSV1sr39TK/(18) F-FHBG PET reporter gene/PET reporter probe (PRG/PRP) system with PRGs derived from human nucleoside kinases.

PROCEDURES

The same adenovirus vector is used to express alternative PRGs. Equal numbers of vectors are injected intravenously into mice. After PRP imaging, quantitative hepatic PET signals are normalized for transduction by measuring hepatic viral genomes.

RESULTS

The same adenovirus vector was used to express equivalent amounts of HSV1sr39TK, mutant human thymidine kinase 2 (TK2-DM), and mutant human deoxycytidine kinase (dCK-A100VTM) in mouse liver. HSV1sr39TK expression was measured with (18) F-FHBG, TK2-DM and dCK-A100VTM with (18) F-L-FMAU. TK2-DM/(18) F-L-FMAU and HSV1sr39TK/(18) F-FHBG had equivalent sensitivities; dCK-A100VTM/(18) F-L-FMAU was twice as sensitive as HSV1sr39TK/(18) F-FHBG.

CONCLUSIONS

The human PRG/PRP sensitivities are comparable and/or better than HSV1sr39TK/(18) F-FHBG. However, for clinical use, identification of the best PRP substrate for each enzyme, characterization of probe distribution, and consequences of overexpressing nucleoside kinases must be evaluated.

Abstract 5539: Low levels of estrogen sensitize PTEN-deficient endometrial tumors to poly-ADP ribose polymerase (PARP) inhibition in vivo

Prior in vitro work suggests that PARP inhibition can destroy tumor cells with defects in homologous recombination resulting from loss of PTEN. Clinical trials have tested the efficacy of this strategy in BRCA mutant ovarian tumors. This approach has not been reported in endometrial carcinomas in vivo. Loss of PTEN tumor suppressor function is the most common genetic alteration associated with endometrial cancer that is the leading gynecologic cancer in the U.S. We hypothesized that oral administration of the PARP inhibitor AZD2281 (Olaparib) would be an effective therapeutic strategy for treating endometrial carcinomas resulting from PTEN loss. This hypothesis was tested in a mouse model for endometrial cancer established by our group. Uterine epithelia were harvested from PTENloxP/loxP mice, dissociated and infected with a Cre lentivirus resulting in PTEN deletion in uterine epithelia. These cells were combined with wild type stroma and placed subrenally in SCID mice resulting in formation of endometrial tumors that accurately recapitulate human disease. After tumor establishment (8 weeks), mice were divided into two cohorts: Group 1 was subjected to a continuous supply of estrogen and Group 2 was deprived of estrogen. Ten SCID mice were treated with a PARP inhibitor, AZD2281, administered orally for 3 weeks while the other 10 SCID mice were treated with vehicle in both hormonal conditions. At completion of therapy, tumors were harvested and analyzed. Forty mice were included in this preclinical trial. AZD2281 was successful in achieving a significant reduction in tumor size in a low estrogenic hormonal milieu. In striking contrast, no response to AZD2281 was seen in tumors exposed to high levels of estrogen. Hormonal deprivation resulted in a 20-fold increase in circulating levels of AZD2281 concomitant with increased inhibition of PARP enzyme activity at the tumor bed. Low levels of estrogen sensitize PTEN deficient tumors to PARP inhibition via two potential mechanisms: 1) down-regulation of key components of the homologous recombination pathway in low compared to high levels of estrogen and 2) a significant increase in the serum concentration of AZD2281 coupled with increased efficacy of PARP inhibition at the tumor bed. We suspect that withdrawal of estrogen results in a decrease in homologous recombination proteins and an increase in circulating levels of AZD2281 by decreasing its metabolism. The net result is greater circulating levels and effectiveness of PARP inhibitors in estrogen deprived treated mice. The results of this preclinical trial suggest that orally administered PARP inhibitors in a low estrogenic hormonal milieu can be effective in targeting PTEN-null endometrial tumors. Extension of this work to a clinical trial can result in personalizing therapies for women afflicted with endometrial cancer using well tolerated orally administered therapeutic agents.

Citation Format: Daniel Y. Paik, Miguel Rosales, Deanna Janzen, Brian Yep, Donghui Cheng, Owen Witte, Huseyin Kayadibi, Kym Faull, Sanaz Memarzadeh. Low levels of estrogen sensitize PTEN-deficient endometrial tumors to poly-ADP ribose polymerase (PARP) inhibition in vivo. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 5539. doi:10.1158/1538-7445.AM2013-5539

Role of Ikaros in hematopoiesis and tumor suppression: Selective functions of individual zinc fingers within the DNA-binding domain of Ikaros. (42.3)

Ikaros, a C2H2 zinc finger transcription factor, is a critical regulator of hematopoiesis and tumor suppression in the lymphoid lineage. The C2H2 zinc finger is the most prevalent DNA-binding motif in mammals, with DNA-binding domains usually containing more tandem fingers than are needed for stable sequence-specific DNA recognition. To examine the reason for the frequent presence of multiple zinc fingers, and to investigate in greater depth the role of Ikaros in hematopoiesis and tumor suppression, we generated mice lacking finger 1 or finger 4 of the 4-finger DNA-binding domain of Ikaros. Each mutant strain exhibited a specific subset of the phenotypes observed with Ikaros null mice. Of particular relevance, fingers 1 and 4 contributed to distinct stages of B- and T-cell development and finger 4 was selectively required for tumor suppression in thymocytes and in a new model of BCR-ABL+ acute lymphoblastic leukemia. These results, combined with transcriptome profiling and DNA-binding analysis, reveal that different subsets of fingers within multi-finger transcription factors can modulate binding to different target sequences and regulate distinct target genes and biological functions. These novel mutant strains provide a powerful tool to elucidate Ikaros' role in hematopoiesis and tumor suppression. Furthermore, this study demonstrates that selective mutagenesis can facilitate efforts to elucidate the functions and mechanisms of action of this prevalent class of factors.

Abstract 4839: Adoptive cell transfer of transgenic T cells elicited a two-wave antitumor cellular immune response consisted of engineered and endogenous T lymphocytes with different sets of functions

Background: Adoptive cell transfer (ACT) of transgenic T lymphocytes expressing tumor antigen specific T cell receptor (TCR) can mediate an objective response in 30%-50% of the metastatic melanoma patients and result in long term tumor regression in certain subjects. However, little is known about the fate of engineered T cells once transferred and the dynamics of host immunity, important for understanding the biological mechanism of the therapy and differing long term efficacy between patients. Methods: We designed a comprehensive study that monitored the transgenic and endogenous immune response in 8 metastatic melanoma patients over 8-10 time points in an ACT therapy of transgenic F5 MART-1 TCR T cells, using newly developed, highly multiplexed clinical immune diagnostics methods (Ma, C. et al. Nature Medicine 17, 738-743 (2011)): (1) The abundance of 35 melanoma antigen specific T cell subsets was enumerated by peptide/MHC tetramer microarrays. (2) The functional performance of 6 phenotypically defined T cell subsets was evaluated via the quantitation of 19 functional proteins secreted from single cells, utilizing a clinical single cell barcode microchip coupled with florescent activated cell sorting. (3) A panel of 37 blood proteins incorporating melanoma associated markers, cytokines and chemokines were measured by an ELISA-like assay. Results: The change of blood marker abundance reflected the general course of the therapy, from pre-conditioning, immune system recovery, immune response, to tumor remission. Furthermore, we found that the TCR engineered T cells sustained a 2-3 week duration anti-tumor response in all patients and secreted large quantities of granzyme B, MIP-1α and MIP-1α. However, this first wave infused immune response vanished rapidly in terms of the number of polyfunctional cells and the amount of cytokines secreted. After day 30 a second wave anti-tumor immunity emerged, incorporating a rebound of the MART-1 TCR engineered population and a new endogenous multi-clonal melanoma specific T cell response. Both groups of cells secreted IFN-γ and TNF-α; however, later they shifted to inhibitory and non-specific functions, such as TGF-β, IL-10 and IL-13. The patient with the most endogenous melanoma specific T cell populations emerged and the strongest functions in the second wave response showed the most effective long term tumor control; weaker second wave response was associated with weaker therapeutic efficacy. Conclusions: The melanoma-specific T cells within the ACT went through a process of in vivo functional changes that correlated with clinical antitumor activity. The appearance and the persistence of the second wave immune response featured by engineered and newly appeared endogenous anti-tumor cellular immunity provided indications of long term therapeutic efficacy.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4839. doi:1538-7445.AM2012-4839

Lin-Sca-1+CD49fhigh stem/progenitors are tumor-initiating cells in the Pten-null prostate cancer model

We have shown previously that Pten deletion leads to the expansion of subset of prostate cancer cells positive for CK5 and p63. Although this subpopulation may be involved in tumor initiation or progression, studies to date have not functionally validated this hypothesis. Using in vitro sphere-forming assay and in vivo prostate reconstitution assay, we show here the presence of a tumor-initiating subpopulation in the Pten prostate cancer mouse model. Specifically, we show that the Lin(-)Sca-1(+)CD49f(high) (LSC) subpopulation overlaps with CK5(+);p63(+) cells and is significantly increased during prostate cancer initiation and progression and after castration. Mutant spheres mimic the structural organization of the epithelial compartment in the Pten-null primary tumor. Sorted LSC cells from either Pten-null spheres or primary tumors are able to regenerate prostate epithelial structure with cancerous morphology, closely mimicking that of primary cancers. Therefore, the LSC subpopulation is capable of initiating a cancerous phenotype that recapitulates the pathology seen in the primary lesions of the Pten mutant prostate model.

Got MLL? Definitive hematopoiesis requires MLL gene expression

A manuscript by Ernst and colleagues in the March 2004 issue of Developmental Cell demonstrates that following hematopoietic stem cell appearance in the AGM, expression of the MLL transcription factor is required for their subsequent differentiation.

The role of Bcr-Abl in chronic myeloid leukemia and stem cell biology

Hematopoietic stem cells, the critical target cells in chronic myeloid leukemia (CML), are difficult to study owing to their rarity. An in vitro differentiation model was used to examine the role of the Bcr-Abl tyrosine kinase in the pathogenesis of CML. A tetracycline-regulated promoter was developed to drive Bcr-Abl expression in differentiating embryonal stem cells. Enforced Bcr-Abl expression was sufficient to increase the number of multilineage progenitors. Myeloid progenitors were expanded in particular and erythroid development was suppressed, consistent with the phenotype of CML. A complementary approach was used to investigate the effect of specifically blocking Bcr-Abl-deregulated tyrosine kinase activity in transformed cells. For this purpose a fusion "escort/phosphatase" was created that binds to Bcr-Abl and effectively inhibits kinase activity in vitro and in vivo. Loss of function was demonstrated by growth inhibition of bcr-abl-transformed fibroblasts, reacquisition of growth factor dependence by Bcr-Abl-expressing hematopoietic cells, and normalization of erythroid differentiation in a human CML line. These studies reaffirm the central role of stem cell biology in understanding the causes and possible treatments for CML, and suggest that direct targeting and inhibition of Bcr-Abl kinase activity is a valid therapeutic approach to treating this disease.

The University of California, Los Angeles/Jennifer Jones Simon Foundation symposium on prostate cancer and epithelial cell biology: bringing together basic scientists and clinicians in the fight against advanced prostate cancer

Prostate cancer is the most common solid tumor in American men and is the second most common cause of cancer deaths. Although surgery and radiation therapy are effective for the treatment of organ-confined cancer, there is no effective treatment that is currently available for patients who have metastatic disease. Antiandrogen therapy is only palliative, and chemotherapy has largely been ineffective. However, recent advances in the understanding of the molecular biology of prostate cancer have lead to the development of new treatment strategies for metastatic cancer, including gene-based therapies, immunotherapies, and antiangiogenesis-based therapy. In association with the Jonsson Comprehensive Cancer Center and the University of California, Los Angeles Department of Urology, the Jennifer Jones Simon Foundation assembled 30 of the world's experts in prostate cancer research to review the most recent advances in the study of prostate cancer, with the hope that the resulting discussions would facilitate the rapid translation of new discoveries from the laboratory bench to the clinic.

Protein binding and signaling properties of RIN1 suggest a unique effector function

Human RIN1 was first characterized as a RAS binding protein based on the properties of its carboxyl-terminal domain. We now show that full-length RIN1 interacts with activated RAS in mammalian cells and defines a minimum region of 434 aa required for efficient RAS binding. RIN1 interacts with the "effector domain" of RAS and employs some RAS determinants that are common to, and others that are distinct from, those required for the binding of RAF1, a known RAS effector. The same domain of RIN1 that binds RAS also interacts with 14-3-3 proteins, extending the similarity between RIN1 and other RAS effectors. When expressed in mammalian cells, the RAS binding domain of RIN1 can act as a dominant negative signal transduction blocker. The amino-terminal domain of RIN1 contains a proline-rich sequence similar to consensus Src homology 3 (SH3) binding regions. This RIN1 sequence shows preferential binding to the ABL-SH3 domain in vitro. Moreover, the amino-terminal domain of RIN1 directly associates with, and is tyrosine phosphorylated by, c-ABL. In addition, RIN1 encodes a functional SH2 domain that has the potential to activate downstream signals. These data suggest that RIN1 is able to mediate multiple signals. A differential pattern of expression and alternate splicing indicate several levels of RIN1 regulation.

Genetic analysis of tyrosine kinase function in B cell development

B lymphopoiesis is regulated by multiple signals from stromal cell contact, soluble cytokines, antigen, and T helper cells. In vitro and biochemical experiments have implicated tyrosine kinases as key components of many of these signaling pathways. Genetic analysis of the role of these tyrosine kinases has been facilitated by recent advance in transgenic and gene targeting technology as well as by the identification of the genetic basis of several human and murine immune deficiencies. This review discusses the effect of gain and loss of function mutations of selected tyrosine kinases and their regulators and substrates on B cell development and function.