Asian American Women's Experiences of Discrimination and Health Behaviors during the COVID-19 Pandemic

The COVID-19 pandemic exacerbated racism experienced by Asian Americans, especially women and older individuals. Little is known about how discriminatory experiences during the pandemic have influenced health behaviors among Asian Americans. Between 10/2021 and 6/2022, we surveyed 193 Asian American women in the San Francisco area. Participants were asked to report types of discrimination they experienced since March 2020. We explored bivariable associations of discrimination and changes in health behaviors and healthcare utilization. Most women were Chinese American (75%) and over 45-years-old (87%). The top three discriminatory experiences reported were being treated with less respect (60%), being treated unfairly at restaurants/stores (49%), and people acting as if they are better (47%). Chinese American women (vs. non-Chinese Asian American women) reported higher frequencies of being threatened/harassed (40% vs. 22%). Women who reported any discriminatory experience (vs. none) were more likely to report less physical exercise (42.7% vs. 26.3%) and canceling/rescheduling medical appointments (65.0% vs. 45.1%). Our findings begin to elucidate Asian American women's experiences of discrimination since the pandemic and provide evidence of the harmful impacts of anti-Asian racism on health behaviors.

Post-death Vesicles of Senescent Bone Marrow Mesenchymal Stromal Polyploids Promote Macrophage Aging and Breast Cancer

Potential systemic factors contributing to aging-associated breast cancer (BC) remain elusive. Here, we reveal that the polyploid giant cells (PGCs) that contain more than two sets of genomes prevailing in aging and cancerous tissues constitute 5-10% of healthy female bone marrow mesenchymal stromal cells (fBMSCs). The PGCs can repair DNA damage and stimulate neighboring cells for clonal expansion. However, dying PGCs in advanced-senescent fBMSCs can form "spikings" which are then separated into membraned mtDNA-containing vesicles (Senescent PGC-Spiking Bodies; SPSBs). SPSB-phagocytosed macrophages accelerate aging with diminished clearance on BC cells and protumor M2 polarization. SPSB-carried mitochondrial OXPHOS components are enriched in BC of elder patients and associated with poor prognosis. SPSB-incorporated breast epithelial cells develop aggressive characteristics and PGCs resembling the polyploid giant cancer cells (PGCCs) in clonogenic BC cells and cancer tissues. These findings highlight an aging BMSC-induced BC risk mediated by SPSB-induced macrophage dysfunction and epithelial cell precancerous transition.

SIGNIFICANCE

Mechanisms underlying aging-associated cancer risk remain unelucidated. This work demonstrates that polyploid giant cells (PGCs) in bone marrow mesenchymal stromal cells (BMSCs) from healthy female bone marrow donors can boost neighboring cell proliferation for clonal expansion. However, the dying-senescent PGCs in the advanced-senescent fBMSCs can form "spikings" which are separated into mitochondrial DNA (mtDNA)-containing spiking bodies (senescent PGC-spiking bodies; SPSBs). The SPSBs promote macrophage aging and breast epithelial cell protumorigenic transition and form polyploid giant cancer cells. These results demonstrate a new form of ghost message from dying-senescent BMSCs, that may serve as a systemic factor contributing to aging-associated immunosuppression and breast cancer risk.

Graphic Abstract

KSHV vIL-6 enhances inflammatory responses by epigenetic reprogramming

Kaposi sarcoma-associated herpesvirus (KSHV) inflammatory cytokine syndrome (KICS) is a newly described chronic inflammatory disease condition caused by KSHV infection and is characterized by high KSHV viral load and sustained elevations of serum KSHV-encoded IL-6 (vIL-6) and human IL-6 (hIL-6). KICS has significant immortality and greater risks of other complications, including malignancies. Although prolonged inflammatory vIL-6 exposure by persistent KSHV infection is expected to have key roles in subsequent disease development, the biological effects of prolonged vIL-6 exposure remain elusive. Using thiol(SH)-linked alkylation for the metabolic (SLAM) sequencing and Cleavage Under Target & Release Using Nuclease analysis (CUT&RUN), we studied the effect of prolonged vIL-6 exposure in chromatin landscape and resulting cytokine production. The studies showed that prolonged vIL-6 exposure increased Bromodomain containing 4 (BRD4) and histone H3 lysine 27 acetylation co-occupancies on chromatin, and the recruitment sites were frequently co-localized with poised RNA polymerase II with associated enzymes. Increased BRD4 recruitment on promoters was associated with increased and prolonged NF-κB p65 binding after the lipopolysaccharide stimulation. The p65 binding resulted in quicker and sustained transcription bursts from the promoters; this mechanism increased total amounts of hIL-6 and IL-10 in tissue culture. Pretreatment with the BRD4 inhibitors, OTX015 and MZ1, eliminated the enhanced inflammatory cytokine production. These findings suggest that persistent vIL-6 exposure may establish a chromatin landscape favorable for the reactivation of inflammatory responses in monocytes. This epigenetic memory may explain the greater risk of chronic inflammatory disease development in KSHV-infected individuals.

Virally encoded interleukin-6 facilitates KSHV replication in monocytes and induction of dysfunctional macrophages

Kaposi's sarcoma-associated herpesvirus (KSHV) is an oncogenic double-stranded DNA virus and the etiologic agent of Kaposi's sarcoma and hyperinflammatory lymphoproliferative disorders. Understanding the mechanism by which KSHV increases the infected cell population is crucial for curing KSHV-associated diseases. Using scRNA-seq, we demonstrate that KSHV preferentially infects CD14+ monocytes, sustains viral lytic replication through the viral interleukin-6 (vIL-6), which activates STAT1 and 3, and induces an inflammatory gene expression program. To study the role of vIL-6 in monocytes upon KSHV infection, we generated recombinant KSHV with premature stop codon (vIL-6(-)) and its revertant viruses (vIL-6(+)). Infection of the recombinant viruses shows that both vIL-6(+) and vIL-6(-) KSHV infection induced indistinguishable host anti-viral response with STAT1 and 3 activations in monocytes; however, vIL-6(+), but not vIL-6(-), KSHV infection promoted the proliferation and differentiation of KSHV-infected monocytes into macrophages. The macrophages derived from vIL-6(+) KSHV infection showed a distinct transcriptional profile of elevated IFN-pathway activation with immune suppression and were compromised in T-cell stimulation function compared to those from vIL-6(-) KSHV infection or uninfected control. Notably, a viral nuclear long noncoding RNA (PAN RNA), which is required for sustaining KSHV gene expression, was substantially reduced in infected primary monocytes upon vIL-6(-) KSHV infection. These results highlight the critical role of vIL-6 in sustaining KSHV transcription in primary monocytes. Our findings also imply a clever strategy in which KSHV utilizes vIL-6 to secure its viral pool by expanding infected monocytes via differentiating into longer-lived dysfunctional macrophages. This mechanism may facilitate KSHV to escape from host immune surveillance and to support a lifelong infection.

KSHV vIL-6 Enhances Inflammatory Responses by Epigenetic Reprogramming

Kaposi sarcoma-associated herpesvirus (KSHV) inflammatory cytokine syndrome (KICS) is a newly described chronic inflammatory disease condition caused by KSHV infection and is characterized by high KSHV viral load and sustained elevations of serum KSHV-encoded IL-6 (vIL-6) and human IL-6 (hIL-6). KICS has significant immortality and possesses greater risks of having other complications, which include malignancies. Although prolonged inflammatory vIL-6 exposure by persistent KSHV infection is expected to have key roles in subsequent disease development, the biological effects of prolonged vIL-6 exposure remain elusive. Using thiol-Linked Alkylation for the Metabolic Sequencing and Cleavage Under Target & Release Using Nuclease analysis, we studied the effect of prolonged vIL-6 exposure in chromatin landscape and resulting cytokine production. The studies showed that prolonged vIL-6 exposure increased Bromodomain containing 4 (BRD4) and histone H3 lysine 27 acetylation co-occupancies on chromatin, and the recruitment sites were frequently co-localized with poised RNAPII with associated enzymes. Increased BRD4 recruitment on promoters was associated with increased and prolonged NF-κB p65 binding after the lipopolysaccharide stimulation. The p65 binding resulted in quicker and sustained transcription bursts from the promoters; this mechanism increased total amounts of hIL-6 and IL-10 in tissue culture. Pretreatment with the BRD4 inhibitor, OTX015, eliminated the enhanced inflammatory cytokine production. These findings suggest that persistent vIL-6 exposure may establish a chromatin landscape favorable for the reactivation of inflammatory responses in monocytes. This epigenetic memory may explain the greater risk of chronic inflammatory disease development in KSHV-infected individuals.

KSHV uses viral IL6 to expand infected immunosuppressive macrophages

Kaposi's sarcoma-associated herpesvirus (KSHV) is an oncogenic double-stranded DNA virus and the etiologic agent of Kaposi's sarcoma and hyperinflammatory lymphoproliferative disorders. Understanding the mechanism by which KSHV increases the infected cell population is crucial for curing KSHV-associated diseases. Here we demonstrate that KSHV preferentially infects CD14 ⁺ monocytes and sustains viral replication through the viral (v)IL6-mediated activation of STAT1 and 3. Using vIL6-sufficient and vIL6-deficient recombinant KSHV, we demonstrated that vIL6 plays a critical role in promoting the proliferation and differentiation of KSHV-infected monocytes into macrophages. Those macrophages from vIL6-sufficient (wild type) KSHV infection showed a distinct transcriptional profile of elevated IFN-pathway activation with immune suppression and were compromised in T-cell stimulation function compared to those from vIL6-deficient KSHV infection or uninfected control. These results highlight a clever strategy, in which KSHV utilizes vIL6 to secure its initial viral pool by expanding infected dysfunctional macrophages. This mechanism also facilitates KSHV to escape from host immune surveillance to establish a lifelong infection.

Summary

KSHV causes multiple inflammatory diseases, however, the mechanism is not clear. Shimoda et al. demonstrate that KSHV preferentially infects monocytes and utilizes virally encoded IL6 to expand and deregulate infected monocytes. This helps the virus escape from host immune surveillance.

The essential roles of FXR in diet and age influenced metabolic changes and liver disease development: a multi-omics study

BACKGROUND

Aging and diet are risks for metabolic diseases. Bile acid receptor farnesoid X receptor (FXR) knockout (KO) mice develop metabolic liver diseases that progress into cancer as they age, which is accelerated by Western diet (WD) intake. The current study uncovers the molecular signatures for diet and age-linked metabolic liver disease development in an FXR-dependent manner.

METHODS

Wild-type (WT) and FXR KO male mice, either on a healthy control diet (CD) or a WD, were euthanized at the ages of 5, 10, or 15 months. Hepatic transcriptomics, liver, serum, and urine metabolomics as well as microbiota were profiled.

RESULTS

WD intake facilitated hepatic aging in WT mice. In an FXR-dependent manner, increased inflammation and reduced oxidative phosphorylation were the primary pathways affected by WD and aging. FXR has a role in modulating inflammation and B cell-mediated humoral immunity which was enhanced by aging. Moreover, FXR dictated neuron differentiation, muscle contraction, and cytoskeleton organization in addition to metabolism. There were 654 transcripts commonly altered by diets, ages, and FXR KO, and 76 of them were differentially expressed in human hepatocellular carcinoma (HCC) and healthy livers. Urine metabolites differentiated dietary effects in both genotypes, and serum metabolites clearly separated ages irrespective of diets. Aging and FXR KO commonly affected amino acid metabolism and TCA cycle. Moreover, FXR is essential for colonization of age-related gut microbes. Integrated analyses uncovered metabolites and bacteria linked with hepatic transcripts affected by WD intake, aging, and FXR KO as well as related to HCC patient survival.

CONCLUSION

FXR is a target to prevent diet or age-associated metabolic disease. The uncovered metabolites and microbes can be diagnostic markers for metabolic disease.

A Genomically and Clinically Annotated Patient-Derived Xenograft Resource for Preclinical Research in Non-Small Cell Lung Cancer

Patient-derived xenograft (PDX) models are an effective preclinical in vivo platform for testing the efficacy of novel drugs and drug combinations for cancer therapeutics. Here we describe a repository of 79 genomically and clinically annotated lung cancer PDXs available from The Jackson Laboratory that have been extensively characterized for histopathologic features, mutational profiles, gene expression, and copy-number aberrations. Most of the PDXs are models of non-small cell lung cancer (NSCLC), including 37 lung adenocarcinoma (LUAD) and 33 lung squamous cell carcinoma (LUSC) models. Other lung cancer models in the repository include four small cell carcinomas, two large cell neuroendocrine carcinomas, two adenosquamous carcinomas, and one pleomorphic carcinoma. Models with both de novo and acquired resistance to targeted therapies with tyrosine kinase inhibitors are available in the collection. The genomic profiles of the LUAD and LUSC PDX models are consistent with those observed in patient tumors from The Cancer Genome Atlas and previously characterized gene expression-based molecular subtypes. Clinically relevant mutations identified in the original patient tumors were confirmed in engrafted PDX tumors. Treatment studies performed in a subset of the models recapitulated the responses expected on the basis of the observed genomic profiles. These models therefore serve as a valuable preclinical platform for translational cancer research.

SIGNIFICANCE

Patient-derived xenografts of lung cancer retain key features observed in the originating patient tumors and show expected responses to treatment with standard-of-care agents, providing experimentally tractable and reproducible models for preclinical investigations.

Multiomic analysis for optimization of combined focal and immunotherapy protocols in murine pancreatic cancer

Background: Although combination immunotherapies incorporating local and systemic components have shown promising results in treating solid tumors, varied tumor microenvironments (TMEs) can impact immunotherapeutic efficacy. Method: We designed and evaluated treatment strategies for breast and pancreatic cancer combining magnetic resonance-guided focused ultrasound (MRgFUS) ablation and antibody therapies. With a combination of single-cell sequencing, spectral flow cytometry, and histological analyses, we profiled an immune-suppressed KPC (Kras^+/LSL-G12D; Trp53^+/LSL-R172H; Pdx1-Cre) pancreatic adenocarcinoma (MT4) model and a dense epithelial neu deletion (NDL) HER2⁺ mammary adenocarcinoma model with a greater fraction of lymphocytes, natural killer cells and activated dendritic cells. We then performed gene ontology analysis, spectral and digital cytometry to assess the immune response to combination immunotherapies and correlation with survival studies. Result: Based on gene ontology analysis, adding ablation to immunotherapy enriched immune cell migration pathways in the pancreatic cancer model and extensively enriched wound healing pathways in the breast cancer model. With CIBERSORTx digital cytometry, aCD40 + aPD-1 immunotherapy combinations enhanced dendritic cell activation in both models. In the MT4 TME, adding the combination of aCD40 antibody and checkpoint inhibitors (aPD-1 and aCTLA-4) with ablation was synergistic, increasing activated natural killer cells and T cells in distant tumors. Furthermore, ablation with immunotherapy upregulated critical Ly6c myeloid remodeling phenotypes that enhance T-cell effector function and increased granzyme and protease encoding genes by as much as 100-fold. Ablation combined with immunotherapy then extended survival in the MT4 model to a greater extent than immunotherapy alone. Conclusion: In summary, TME profiling informed a successful multicomponent treatment protocol incorporating ablation and facilitated differentiation of TMEs in which ablation is most effective.

A distinct subpopulation of leukemia initiating cells in acute precursor B lymphoblastic leukemia: quiescent phenotype and unique transcriptomic profile

In leukemia, a distinct subpopulation of cancer-initiating cells called leukemia stem cells (LSCs) is believed to drive population expansion and tumor growth. Failing to eliminate LSCs may result in disease relapse regardless of the amount of non-LSCs destroyed. The first step in targeting and eliminating LSCs is to identify and characterize them. Acute precursor B lymphoblastic leukemia (B-ALL) cells derived from patients were incubated with fluorescent glucose analog 2-(N-(7-Nitrobenz-2-oxa-1, 3-diazol-4-yl) Amino)-2-Deoxyglucose (NBDG) and sorted based on NBDG uptake. Cell subpopulations defined by glucose uptake were then serially transplanted into mice and evaluated for leukemia initiating capacity. Gene expression profiles of these cells were characterized using RNA-Sequencing (RNA-Seq). A distinct population of NBDG-low cells was identified in patient B-ALL samples. These cells are a small population (1.92% of the entire leukemia population), have lower HLA expression, and are smaller in size (4.0 to 7.0 μm) than the rest of the leukemia population. All mice transplanted with NBDG-low cells developed leukemia between 5 and 14 weeks, while those transplanted with NBDG-high cells did not develop leukemia (p ≤ 0.0001-0.002). Serial transplantation of the NBDG-low mouse model resulted in successful leukemia development. NBDG-medium (NBDG-med) populations also developed leukemia. Interestingly, comprehensive molecular characterization of NBDG-low and NBDG-med cells from patient-derived xenograft (PDX) models using RNA-Seq revealed a distinct profile of 2,162 differentially-expressed transcripts (DETs) (p<0.05) with 70.6% down-regulated in NBDG-low cells. Hierarchical clustering of DETs showed distinct segregation of NBDG-low from NBDG-med and NBDG-high groups with marked transcription expression alterations in the NBDG-low group consistent with cancer survival. In conclusion, A unique subpopulation of cells with low glucose uptake (NBDG-low) in B-ALL was discovered. These cells, despite their quiescence characteristics, once transplanted in mice, showed potent leukemia initiating capacity. Although NBDG-med cells also initiated leukemia, gene expression profiling revealed a distinct signature that clearly distinguishes NBDG-low cells from NBDG-med and the rest of the leukemia populations. These results suggest that NBDG-low cells may represent quiescent LSCs. These cells can be activated in the appropriate environment in vivo, showing leukemia initiating capacity. Our study provides insight into the biologic mechanisms of B-ALL initiation and survival.

Pharmacogenetic Gene-Drug Associations in Pediatric Burn and Surgery Patients

Management of critically ill patients requires simultaneous administration of many medications. Treatment for patient comorbidities may lead to drug-drug interactions which decrease drug efficacy or increase adverse reactions. Current practices rely on a one-size-fits-all dosing approach. Pharmacogenetic testing is generally reserved for addressing problems rather than used proactively to optimize care. We hypothesized that burn and surgery patients will have one or more genetic variants in drug metabolizing pathways used by one or more medications administered during the patient's hospitalization. The aim of this study was to determine the frequency of variants with abnormal function in the primary drug pathways and identify which medications may be impacted. Genetic (19 whole exome and 11 whole genome) and medication data from 30 pediatric burn and surgery patients were analyzed to identify pharmacogene-drug associations. Nineteen patients were identified with predicted altered function in one or more of the following genes: CYP2C9, CYP2C19, CYP2D6, and CYP3A4. The majority had decreased function, except for several patients with CYP2C19 rapid or ultrarapid variants. Some drugs administered during hospitalization that rely on these pathways include hydrocodone, oxycodone, methadone, ibuprofen, ketorolac, celecoxib, diazepam, famotidine, diphenhydramine, and glycopyrrolate. Approximately one-third of the patients tested had functionally impactful genotypes in each of the primary drug metabolizing pathways. This study suggests that genetic variants may in part explain the vast variability in drug efficacy and suggests that future pharmacogenetics research may optimize dosing regimens.

Abstract 6314: TME subtype impacts response to combined thermal ablation and immunotherapy

The tumor microenvironment (TME) subtype is a critical factor when combining immunotherapy with tumor debulking strategies such as ultrasound ablation. To understand the effects of the TME subtype, we studied two multi-site murine cancer models, an immune-suppressed KPC (Kras+/LSL-G12D; Trp53+/LSL-R172H; Pdx1-Cre) pancreatic adenocarcinoma (MT4) model and a neu deletion HER2+ (NDL) mammary adenocarcinoma model with a larger naïve lymphocyte population. After profiling the two models with histology and single-cell sequencing, we designed immunotherapy combinations with Magnetic Resonance-guided Focused Ultrasound (MRgFUS) thermal ablation that were specific to each TME subtype. To understand the impact of the molecular and cellular differences upon each model, we characterized the treatment effect with transcriptomic analysis and digital cytometry. We found that combining MRgFUS ablation with immunotherapy reduced tumor growth and extended survival by at least 2-fold in the MT4 pancreatic cancer model. Gene set enrichment analysis (GSEA) of bulk RNA sequencing data indicated that the combination of ablation with immunotherapy preferentially enriched functional annotations for leukocyte migration in the MT4 model and wound healing and inflammatory cytokines in the NDL model (e.g. for IL6: 1.6 fold increase in MT4 vs 10.3 fold in NDL tumors). We then particularly focused on whether dendritic cell (DC) activation and CD4 T cell populations could be enhanced when ablating pancreatic tumors. By CIBERSORTx digital cytometry, aCD40 + aPD-1 combinations increased the presence of activated DCs in MT4 tumors by 2.4-fold. Activated DCs were also increased by CP4 (aCD40 + aPD-1 + CTLA-4) alone 1.7 fold or in combination with ablation in both treated (2.4 fold) and distant (2.2 fold) lesions. Ablation combined with aPD-1 alone did not significantly impact DCs in the MT4 model. In addition, CD4 lymphocytes increased 5 and 8 fold in treated and distant tumors by ablation combined with CP4 in the MT4 model. Taken together, inflammatory cytokines were preferentially elevated by ablation in a dense epithelial breast cancer as compared with a pancreatic tumor model. Further, the results suggest that aCD40 immunotherapy retains efficacy when combined with thermal ablation in pancreatic tumors. This work can inform clinical translation of ablative and immunotherapy combination protocols.

Citation Format: James Wang, Brett Z. Fite, Aris Kare, Bo Wu, Marina N. Raie, Spencer Tumbale, Ryan R. Davis, Clifford G. Tepper, Katherine Ferrara. TME subtype impacts response to combined thermal ablation and immunotherapy [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 6314.

KSHV episome tethering sites on host chromosomes and regulation of latency-lytic switch by CHD4

Kaposi sarcoma-associated herpesvirus (KSHV) establishes a latent infection in the cell nucleus, but where KSHV episomal genomes are tethered and the mechanisms underlying KSHV lytic reactivation are unclear. Here, we study the nuclear microenvironment of KSHV episomes and show that the KSHV latency-lytic replication switch is regulated via viral long non-coding (lnc)RNA-CHD4 (chromodomain helicase DNA binding protein 4) interaction. KSHV episomes localize with CHD4 and ADNP proteins, components of the cellular ChAHP complex. The CHD4 and ADNP proteins occupy the 5'-region of the highly inducible lncRNAs and terminal repeats of the KSHV genome together with latency-associated nuclear antigen (LANA). Viral lncRNA binding competes with CHD4 DNA binding, and KSHV reactivation sequesters CHD4 from the KSHV genome, which is also accompanied by detachment of KSHV episomes from host chromosome docking sites. We propose a model in which robust KSHV lncRNA expression determines the latency-lytic decision by regulating LANA/CHD4 binding to KSHV episomes.

KSHV transactivator-derived small peptide traps coactivators to attenuate MYC and inhibits leukemia and lymphoma cell growth

In herpesvirus replicating cells, host cell gene transcription is frequently down-regulated because important transcriptional apparatuses are appropriated by viral transcription factors. Here, we show a small peptide derived from the Kaposi's sarcoma-associated herpesvirus transactivator (K-Rta) sequence, which attenuates cellular MYC expression, reduces cell proliferation, and selectively kills cancer cell lines in both tissue culture and a xenograft tumor mouse model. Mechanistically, the peptide functions as a decoy to block the recruitment of coactivator complexes consisting of Nuclear receptor coactivator 2 (NCOA2), p300, and SWI/SNF proteins to the MYC promoter in primary effusion lymphoma cells. Thiol(SH)-linked alkylation for the metabolic sequencing of RNA (SLAM seq) with target-transcriptional analyses further confirm that the viral peptide directly attenuates MYC and MYC-target gene expression. This study thus provides a unique tool to control MYC activation, which may be used as a therapeutic payload to treat MYC-dependent diseases such as cancers and autoimmune diseases.

ARVib suppresses growth of advanced prostate cancer via inhibition of androgen receptor signaling

Targeting androgen signaling with the second-generation anti-androgen drugs, such as enzalutamide (Enza), abiraterone (Abi), apalutamide (Apal), and darolutamide (Daro), is the mainstay for the treatment of castration-resistant prostate cancer (CRPC). While these treatments are effective initially, resistance occurs frequently. Continued expression of androgen receptor (AR) and its variants such as AR-V7 despite AR-targeted therapy contributes to treatment resistance and cancer progression in advanced CRPC patients. This highlights the need for new strategies blocking continued AR signaling. Here, we identify a novel AR/AR-V7 degrader (ARVib) and found that ARVib effectively degrades AR/AR-V7 protein and attenuates AR/AR-V7 downstream target gene expression in prostate cancer cells. Mechanistically, ARVib degrades AR/AR-V7 protein through the ubiquitin-proteasome pathway mediated by HSP70/STUB1 machinery modulation. ARVib suppresses HSP70 expression and promotes STUB1 nuclear translocation, where STUB1 binds to AR/AR-V7 and promotes its ubiquitination and degradation. ARVib significantly inhibits resistant prostate tumor growth and improves enzalutamide treatment in vitro and in vivo. These data suggest that ARVib has potential for development as an AR/AR-V7 degrader to treat resistant CRPC.

Novel Patient Metastatic Pleural Effusion-Derived Xenograft Model of Renal Medullary Carcinoma Demonstrates Therapeutic Efficacy of Sunitinib

Background

Renal medullary carcinoma (RMC) is a rare but aggressive tumor often complicated by early lung metastasis with few treatment options and very poor outcomes. There are currently no verified RMC patient-derived xenograft (PDX) mouse models established from metastatic pleural effusion (PE) available to study RMC and evaluate new therapeutic options.

Methods

Renal tumor tissue and malignant PE cells from an RMC patient were successfully engrafted into 20 NOD.Cg-Prkdc^scid Il2rg^tm1Wjl/SzJ (NSG) mice. We evaluated the histopathological similarity of the renal tumor and PE PDXs with the original patient renal tumor and PE, respectively. We then evaluated the molecular integrity of the renal tumor PDXs between passages, as well as the PE PDX compared to two generations of renal tumor PDXs, by microarray analysis. The therapeutic efficacy of sunitinib and temsirolimus was tested in a serially-transplanted generation of 27 PE PDX mice.

Results

The pathologic characteristics of the patient renal tumor and patient PE were retained in the PDXs. Gene expression profiling revealed high concordance between the two generations of renal tumor PDXs (RMC-P0 vs. RMC-P1, r=0.865), as well as between the first generation PE PDX and each generation of the renal tumor PDX (PE-P0 vs. RMC-P0, r=0.919 and PE-P0 vs. RMC-P1, r=0.843). A low number (626) of differentially-expressed genes (DEGs) was seen between the first generation PE PDX and the first generation renal tumor PDX. In the PE-P1 xenograft, sunitinib significantly reduced tumor growth (p<0.001) and prolonged survival (p=0.004) compared to the vehicle control.

Conclusions

A metastatic PE-derived RMC PDX model was established and shown to maintain histologic features of the patient cancer. Molecular integrity of the PDX models was well maintained between renal tumor and PE PDX as well as between two successive renal tumor PDX generations. Using the PE PDX model, sunitinib demonstrated therapeutic efficacy for RMC. This model can serve as a foundation for future mechanistic and therapeutic studies for primary and metastatic RMC.

Immune modulation resulting from MR-guided high intensity focused ultrasound in a model of murine breast cancer

High intensity focused ultrasound (HIFU) rapidly and non-invasively destroys tumor tissue. Here, we sought to assess the immunomodulatory effects of MR-guided HIFU and its combination with the innate immune agonist CpG and checkpoint inhibitor anti-PD-1. Mice with multi-focal breast cancer underwent ablation with a parameter set designed to achieve mechanical disruption with minimal thermal dose or a protocol in which tumor temperature reached 65 °C. Mice received either HIFU alone or were primed with the toll-like receptor 9 agonist CpG and the checkpoint modulator anti-PD-1. Both mechanical HIFU and thermal ablation induced a potent inflammatory response with increased expression of Nlrp3, Jun, Mefv, Il6 and Il1β and alterations in macrophage polarization compared to control. Furthermore, HIFU upregulated multiple innate immune receptors and immune pathways, including Nod1, Nlrp3, Aim2, Ctsb, Tlr1/2/4/7/8/9, Oas2, and RhoA. The inflammatory response was largely sterile and consistent with wound-healing. Priming with CpG attenuated Il6 and Nlrp3 expression, further upregulated expression of Nod2, Oas2, RhoA, Pycard, Tlr1/2 and Il12, and enhanced T-cell number and activation while polarizing macrophages to an anti-tumor phenotype. The tumor-specific antigen, cytokines and cell debris liberated by HIFU enhance response to innate immune agonists.

Short-term organoid culture for drug sensitivity testing of high-grade serous carcinoma

OBJECTIVE

Cancer patient-derived organoids (PDOs) grow as three dimensional (3D) structures in the presence of extracellular matrix and have been found to represent the original tumor's genetic complexity. In addition, PDOs can be grown and subjected to drug sensitivity testing in a shorter time course and with lesser expense than patient-derived xenograft models. Many patients with recurrent ovarian cancer develop malignant effusions that become refractory to chemotherapy. Since these same patients often present for palliative aspiration of ascites or pleural effusions, there is a potential opportunity to obtain tumor specimens in the form of multicellular spheroids (MCS) present in malignant effusion fluids. Our objective was to develop a short duration culture of MCS from ovarian cancer malignant effusions in conditions selected to support organoid growth and use them as a platform for empirical drug sensitivity testing.

METHODS

In this study, malignant effusion specimens were collected from patients with high-grade serous ovarian carcinoma (HGSOC). MCS were recovered and subjected to culture conditions designed to support organoid growth. In a subset of specimens, RNA-sequencing was performed at two time points during the short-term culture to determine changes in transcriptome in response to culture conditions. Organoid induction was also characterized in these specimens using Ki67 staining and histologic analysis. Drug sensitivity testing was performed on all specimens.

RESULTS

Our model describes organoids formed within days of primary culture, which can recapitulate the histological features of malignant ascites fluid and can be expanded for at least 6 days. RNA-seq analysis of four patient specimens showed that within 6 days of culture, there was significant up-regulation of genes related to cellular proliferation, epithelial-mesenchymal transition, and KRAS signaling pathways. Drug sensitivity testing identified several agents with therapeutic potential.

CONCLUSIONS

Short duration organoid culture of MCS from HGSOC malignant effusions can be used as a platform for empiric drug sensitivity testing. These ex vivo models may be helpful in screening new or existing therapeutic agents prior to individualized treatment options.

High frequency of the PNPLA3 rs738409 [G] single-nucleotide polymorphism in Hmong individuals as a potential basis for a predisposition to chronic liver disease

BACKGROUND

An exploratory study was performed to determine the prevalence of the patatin-like phospholipase domain-containing protein 3 (PNPLA3) rs78409 [G] allele among the Hmong as a risk factor for nonalcoholic fatty liver disease (NAFLD). NAFLD/nonalcoholic steatohepatitis is the world's most common chronic liver disease and is expected to replace viral hepatitis as the leading cause of cirrhosis and potential precursor to hepatocellular carcinoma (HCC). Of all populations in California, the Hmong experience the highest risk of death from HCC and the highest prevalence of metabolic syndrome risk factors among Asians that predispose them to NAFLD. Here a genetic explanation was sought for the high rates of chronic liver disease among the Hmong. The literature pointed to the PNPLA3 rs738409 [G] allele as a potential genetic culprit.

METHODS

Cell-free DNA was isolated from 26 serum samples previously collected in community settings. Quantitative polymerase chain reaction-based single-nucleotide polymorphism (SNP) genotyping was performed with a validated TaqMan SNP genotyping assay, and results were analyzed with TaqMan Genotyper software.

RESULTS

The PNPLA3 rs738409 [C>G] variant occurred at a frequency of 0.46 (12 of 26; 95% confidence interval, 0.27-0.67). This carrier rate would rank the Hmong as the third highest population in the 1000 Genomes Project.

CONCLUSIONS

Although this small sample size limits the generalizability, the high frequency rates of this allele along with the presence of metabolic syndrome risk factors warrant further studies into the etiology of NAFLD among the Hmong. Cancer 2018;124:1583-9. © 2018 American Cancer Society.

Abstract 4842: Overcoming EGFR and ERK-mediated resistance to enzalutamide in castration-resistant prostate cancer

The present project was undertaken to determine whether the activation of the EGFR family (EGFR/ErbB2/ErbB3/ErbB4) and its downstream signaling effector ERK1/2 plays a role in enzalutamide resistance and whether treatment with ErbB or ERK inhibitors overcome this resistance. C4-2B (enzalutamide sensitive) and 22Rv1 (partially enzalutamide resistant) cell lines cultured for prolonged periods in enzalutamide, developed resistance to this drug (C4-2B/MDVR and 22Rv1/MDVR, respectively). Whole genome comparison of enza-resistant to parental lines demonstrated that the ErbB signaling network was significantly upregulated in the enza-resistant lines. Comparison of various enza-sensitive and resistant lines demonstrated a strong correlation between phosphorylation at EGFR(Y1068) and enza resistance. Inhibition of EGFR, but not that of ErbB2 or ErbB3 prevented cell viability. The EGFR inhibitors erlotinib and dacomitinib, but not the ErbB2 inhibitor lapatinib, suppressed viability in combination with enzalutamide. We hypothesized that enza-resistant tumors expressing higher levels of EGFR would be more responsive to erlotinib. To test this hypothesis, we compared the effects of erlotinib and enzalutamide, individually or in combination, in organelles from PDX tumors expressing high or low EGFR levels. Significantly, tumors expressing high EGFR, but not those expressing low EGFR, were responsive to the combination. Finally, we investigated the cause for greater efficacy with erlotinib compared to lapatinib in PCa. Comparison of the effects of different ligands revealed that while both lapatinib and erlotinib inhibited EGFR phosphorylation, only erlotinib but not lapatinib was able to inhibit EGF-induced ERK phosphorylation. This indicated an important role for ERK in the mediation of EGFR ligand induced enzalutamide resistance. Continuous culture of enza-sensitive C4 cells in enzalutamide resulted in the development of ERK phosphorylation in these PTEN-null cells that normally do not express phosphorylated ERK, and the newly ERK phosphorylated cells also were more susceptible to erlotinib as well. In support of a role for ERK in mediating the effects of EGFR activation in enza-resistant cells, inhibition of EGFR but not ErbB2 or ErbB3 inhibited ERK phosphorylation, and the ERK inhibitor ulitertinib inhibited viability of enza-resistant lines. We conclude that enzalutamide treatment causes an increase in EGFR ligands that result in the phosphorylation of EGFR at Y1068, which further resulted in phosphorylation of ERK. EGFR inhibitors that prevent ERK phosphorylation were effective in suppressing viability of enza-resistant CRPC cells, whereas ErbB2 inhibitors that did not affect ERK phosphorylation were unable to affect cell viability. These results demonstrate why certain ErbB inhibitors failed to affect enza-resistant CRPC tumors but provide encouragement for others.

Citation Format: Thomas M. Steele, Maitreyee K. Jathal, Salma Siddiqui, Sisi Qin, Clifford G. Tepper, Ralph W. deVere White, Manish Kohli, Liewei Wang, Allen C. Gao, Paramita M. Ghosh. Overcoming EGFR and ERK-mediated resistance to enzalutamide in castration-resistant prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4842.

A Syngeneic ErbB2 Mammary Cancer Model for Preclinical Immunotherapy Trials

In order to develop a practical model of breast cancer, with in vitro and syngeneic, immune-intact, in vivo growth capacity, we established a primary cell line derived from a mammary carcinoma in the transgenic FVB/N-Tg(MMTV-ErbB2*)NDL2-5Mul mouse, referred to as "NDL^UCD". The cell line is adapted to standard cell culture and can be transplanted into syngeneic FVB/N mice. The line maintains a stable phenotype over multiple in vitro passages and rounds of in vivo transplantation. NDL^UCD tumors in FVB/N mice exhibit high expression of ErbB2 and ErbB3 and signaling molecules downstream of ErbB2. The syngeneic transplant tumors elicit an immune reaction in the adjacent stroma, detected and characterized using histology, immunophenotyping, and gene expression. NDL^UCD cells also express PD-L1 in vivo and in vitro, and in vivo transplants are reactive to anti-immune checkpoint therapy with responses conducive to immunotherapy studies. This new NDL^UCD cell line model is a practical alternative to the more commonly used 4T1 cells, and our previously described FVB/N-Tg(MMTV-PyVT)634Mul derived Met-1^fvb2 and FVB/NTg(MMTV-PyVT^Y315F/Y322F) derived DB-7^fvb2 cell lines. The NDL^UCD cells have, so far, remained genetically and phenotypically stable over many generations, with consistent and reproducible results in immune intact preclinical cohorts.

Inhibition of mitochondrial respiration prevents BRAF-mutant melanoma brain metastasis

Melanoma patients carry a high risk of developing brain metastases, and improvements in survival are still measured in weeks or months. Durable disease control within the brain is impeded by poor drug penetration across the blood-brain barrier, as well as intrinsic and acquired drug resistance. Augmented mitochondrial respiration is a key resistance mechanism in BRAF-mutant melanomas but, as we show in this study, this dependence on mitochondrial respiration may also be exploited therapeutically. We first used high-throughput pharmacogenomic profiling to identify potentially repurposable compounds against BRAF-mutant melanoma brain metastases. One of the compounds identified was β-sitosterol, a well-tolerated and brain-penetrable phytosterol. Here we show that β-sitosterol attenuates melanoma cell growth in vitro and also inhibits brain metastasis formation in vivo. Functional analyses indicated that the therapeutic potential of β-sitosterol was linked to mitochondrial interference. Mechanistically, β-sitosterol effectively reduced mitochondrial respiratory capacity, mediated by an inhibition of mitochondrial complex I. The net result of this action was increased oxidative stress that led to apoptosis. This effect was only seen in tumor cells, and not in normal cells. Large-scale analyses of human melanoma brain metastases indicated a significant role of mitochondrial complex I compared to brain metastases from other cancers. Finally, we observed completely abrogated BRAF inhibitor resistance when vemurafenib was combined with either β-sitosterol or a functional knockdown of mitochondrial complex I. In conclusion, based on its favorable tolerability, excellent brain bioavailability, and capacity to inhibit mitochondrial respiration, β-sitosterol represents a promising adjuvant to BRAF inhibitor therapy in patients with, or at risk for, melanoma brain metastases.

Obatoclax, a BH3 Mimetic, Enhances Cisplatin-Induced Apoptosis and Decreases the Clonogenicity of Muscle Invasive Bladder Cancer Cells via Mechanisms That Involve the Inhibition of Pro-Survival Molecules as Well as Cell Cycle Regulators

Several studies by our group and others have determined that expression levels of Bcl-2 and/or Bcl-xL, pro-survival molecules which are associated with chemoresistance, are elevated in patients with muscle invasive bladder cancer (MI-BC). The goal of this study was to determine whether combining Obatoclax, a BH3 mimetic which inhibits pro-survival Bcl-2 family members, can improve responses to cisplatin chemotherapy, the standard of care treatment for MI-BC. Three MI-BC cell lines (T24, TCCSuP, 5637) were treated with Obatoclax alone or in combination with cisplatin and/or pre-miR-34a, a molecule which we have previously shown to inhibit MI-BC cell proliferation via decreasing Cdk6 expression. Proliferation, clonogenic, and apoptosis assays confirmed that Obatoclax can decrease cell proliferation and promote apoptosis in a dose-dependent manner. Combination treatment experiments identified Obatoclax + cisplatin as the most effective treatment. Immunoprecipitation and Western analyses indicate that, in addition to being able to inhibit Bcl-2 and Bcl-xL, Obatoclax can also decrease cyclin D1 and Cdk4/6 expression levels. This has not previously been reported. The combined data demonstrate that Obatoclax can inhibit cell proliferation, promote apoptosis, and significantly enhance the effectiveness of cisplatin in MI-BC cells via mechanisms that likely involve the inhibition of both pro-survival molecules and cell cycle regulators.

KDM8/JMJD5 as a dual coactivator of AR and PKM2 integrates AR/EZH2 network and tumor metabolism in CRPC

During the evolution into castration or therapy resistance, prostate cancer cells reprogram the androgen responses to cope with the diminishing level of androgens, and undergo metabolic adaption to the nutritionally deprived and hypoxia conditions. AR (androgen receptor) and PKM2 (pyruvate kinase M2) have key roles in these processes. We report in this study, KDM8/JMJD5, a histone lysine demethylase/dioxygnase, exhibits a novel property as a dual coactivator of AR and PKM2 and as such, it is a potent inducer of castration and therapy resistance. Previously, we showed that KDM8 is involved in the regulation of cell cycle and tumor metabolism in breast cancer cells. Its role in prostate cancer has not been explored. Here, we show that KDM8's oncogenic properties in prostate cancer come from its direct interaction (1) with AR to affect androgen response and (2) with PKM2 to regulate tumor metabolism. The interaction with AR leads to the elevated expression of androgen response genes in androgen-deprived conditions. They include ANCCA/ATAD2 and EZH2, which are directly targeted by KDM8 and involved in sustaining the survival of the cells under hormone-deprived conditions. Notably, in enzalutamide-resistant cells, the expressions of both KDM8 and EZH2 are further elevated, so are neuroendocrine markers. Consequently, EZH2 inhibitors or KDM8 knockdown both resensitize the cells toward enzalutamide. In the cytosol, KDM8 associates with PKM2, the gatekeeper of pyruvate flux and translocates PKM2 into the nucleus, where the KDM8/PKM2 complex serves as a coactivator of HIF-1α to upregulate glycolytic genes. Using shRNA knockdown, we validate KDM8's functions as a regulator for both androgen-responsive and metabolic genes. KDM8 thus presents itself as an ideal therapeutic target for metabolic adaptation and castration-resistance of prostate cancer cells.

Identification of integrin drug targets for 17 solid tumor types

Integrins are contributors to remodeling of the extracellular matrix and cell migration. Integrins participate in the assembly of the actin cytoskeleton, regulate growth factor signaling pathways, cell proliferation, and control cell motility. In solid tumors, integrins are involved in promoting metastasis to distant sites, and angiogenesis. Integrins are a key target in cancer therapy and imaging. Integrin antagonists have proven successful in halting invasion and migration of tumors. Overexpressed integrins are prime anti-cancer drug targets. To streamline the development of specific integrin cancer therapeutics, we curated data to predict which integrin heterodimers are pausible therapeutic targets against 17 different solid tumors. Computational analysis of The Cancer Genome Atlas (TCGA) gene expression data revealed a set of integrin targets that are differentially expressed in tumors. Filtered by FPKM (Fragments Per Kilobase of transcript per Million mapped reads) expression level, overexpressed subunits were paired into heterodimeric protein targets. By comparing the RNA-seq differential expression results with immunohistochemistry (IHC) data, overexpressed integrin subunits were validated. Biologics and small molecule drug compounds against these identified overexpressed subunits and heterodimeric receptors are potential therapeutics against these cancers. In addition, high-affinity and high-specificity ligands against these integrins can serve as efficient vehicles for delivery of cancer drugs, nanotherapeutics, or imaging probes against cancer.

Distinct immune signatures in directly treated and distant tumors result from TLR adjuvants and focal ablation

Both adjuvants and focal ablation can alter the local innate immune system and trigger a highly effective systemic response. Our goal is to determine the impact of these treatments on directly treated and distant disease and the mechanisms for the enhanced response obtained by combinatorial treatments.

Methods: We combined RNA-sequencing, flow cytometry and TCR-sequencing to dissect the impact of immunotherapy and of immunotherapy combined with ablation on local and systemic immune components.

Results: With administration of a toll-like receptor agonist agonist (CpG) alone or CpG combined with same-site ablation, we found dramatic differences between the local and distant tumor environments, where the directly treated tumors were skewed to high expression of F4/80, Cd11b and Tnf and the distant tumors to enhanced Cd11c, Cd3 and Ifng. When ablation was added to immunotherapy, 100% (n=20/20) of directly treated tumors and 90% (n=18/20) of distant tumors were responsive. Comparing the combined ablation-immunotherapy treatment to immunotherapy alone, we find three major mechanistic differences. First, while ablation alone enhanced intratumoral antigen cross-presentation (up to ~8% of CD45⁺ cells), systemic cross-presentation of tumor antigen remained low. Combining same-site ablation with CpG amplified cross-presentation in the draining lymph node (~16% of CD45⁺ cells) compared to the ablation-only (~0.1% of CD45⁺ cells) and immunotherapy-only cohorts (~10% of CD45⁺ cells). Macrophages and DCs process and present this antigen to CD8⁺ T-cells, increasing the number of unique T-cell receptor rearrangements in distant tumors. Second, type I interferon (IFN) release from tumor cells increased with the ablation-immunotherapy treatment as compared with ablation or immunotherapy alone. Type I IFN release is synergistic with toll-like receptor activation in enhancing cytokine and chemokine expression. Expression of genes associated with T-cell activation and stimulation (Eomes, Prf1 and Icos) was 27, 56 and 89-fold higher with ablation-immunotherapy treatment as compared to the no-treatment controls (and 12, 32 and 60-fold higher for immunotherapy-only treatment as compared to the no-treatment controls). Third, we found that the ablation-immunotherapy treatment polarized macrophages and dendritic cells towards a CD169 subset systemically, where CD169⁺ macrophages are an IFN-enhanced subpopulation associated with dead-cell antigen presentation.

Conclusion: While the local and distant responses are distinct, CpG combined with ablative focal therapy drives a highly effective systemic immune response.

Oncolytic Reactivation of KSHV as a Therapeutic Approach for Primary Effusion Lymphoma

Primary effusion lymphoma (PEL) is an aggressive subtype of non-Hodgkin lymphoma caused by Kaposi's sarcoma-associated herpesvirus (KSHV) infection. Currently, treatment options for patients with PEL are limited. Oncolytic viruses have been engineered as anticancer agents and have recently shown increased therapeutic promise. Similarly, lytic activation of endogenous viruses from latently infected tumor cells can also be applied as a cancer therapy. In theory, such a therapeutic strategy would induce oncolysis by viral replication, while simultaneously stimulating an immune response to viral lytic cycle antigens. We examined the combination of the FDA-approved drug ingenol-3-angelate (PEP005) with epigenetic drugs as a rational therapeutic approach for KSHV-mediated malignancies. JQ1, a bromodomain and extra terminal (BET) protein inhibitor, in combination with PEP005, not only robustly induced KSHV lytic replication, but also inhibited IL6 production from PEL cells. Using the dosages of these agents that were found to be effective in reactivating HIV (as a means to clear latent virus with highly active antiretroviral therapy), we were able to inhibit PEL growth in vitro and delay tumor growth in a PEL xenograft tumor model. KSHV reactivation was mediated by activation of the NF-κB pathway by PEP005, which led to increased occupancy of RNA polymerase II onto the KSHV genome. RNA-sequencing analysis further revealed cellular targets of PEP005, JQ1, and the synergistic effects of both. Thus, combination of PEP005 with a BET inhibitor may be considered as a rational therapeutic approach for the treatment of PEL. Mol Cancer Ther; 16(11); 2627-38. ©2017 AACR.

The Phosphatidylinositol 3-Kinase Pathway as a Potential Therapeutic Target in Bladder Cancer

Purpose: Activation of the PI3K pathway occurs in over 40% of bladder urothelial cancers. The aim of this study is to determine the therapeutic potential, the underlying action, and the resistance mechanisms of drugs targeting the PI3K pathway.Experimental Design: Urothelial cancer cell lines and patient-derived xenografts (PDXs) were analyzed for alterations of the PI3K pathway and for their sensitivity to the small-molecule inhibitor pictilisib alone and in combination with cisplatin and/or gemcitabine. Potential predictive biomarkers for pictilisib were evaluated, and RNA sequencing was performed to explore drug resistance mechanisms.Results: The bladder cancer cell line TCCSUP, which harbors a PIK3CA E545K mutation, was sensitive to pictilisib compared to cell lines with wild-type PIK3CA Pictilisib exhibited stronger antitumor activity in bladder cancer PDX models with PI3KCA H1047R mutation or amplification than the control PDX model. Pictilisib synergized with cisplatin and/or gemcitabine in vitro, significantly delayed tumor growth, and prolonged survival compared with single-drug treatment in the PDX models. The phosphorylation of ribosomal protein S6 correlated with response to pictilisib both in vitro and in vivo, and could potentially serve as a biomarker to predict response to pictilisib. Pictilisib activated the compensatory MEK/ERK pathway that likely contributed to pictilisib resistance, which was reversed by cotreatment with the RAF inhibitor sorafenib. RNA sequencing of tumors resistant to treatment suggested that LSP1 downregulation correlated with drug resistance.Conclusions: These preclinical results provide new insights into the therapeutic potential of targeting the PI3K pathway for the treatment of bladder cancer. Clin Cancer Res; 23(21); 6580-91. ©2017 AACR.

The androgen receptor is a negative regulator of eIF4E phosphorylation at S209: implications for the use of mTOR inhibitors in advanced prostate cancer

The anti-androgen bicalutamide is widely used in the treatment of advanced prostate cancer (PCa) in many countries, but its effect on castration resistant PCa (CRPC) is limited. We previously showed that resistance to bicalutamide results from activation of mechanistic target of rapamycin (mTOR). Interestingly, clinical trials testing combinations of the mTOR inhibitor RAD001 with bicalutamide were effective in bicalutamide-naïve CRPC patients, but not in bicalutamide-pre-treated ones. Here we investigate causes for their difference in response. Evaluation of CRPC cell lines identified resistant vs sensitive in-vitro models, and revealed that increased eIF4E(S209) phosphorylation is associated with resistance to the combination. We confirmed using a human-derived tumor-xenograft mouse model that bicalutamide pre-treatment is associated with an increase in eIF4E(S209) phosphorylation. Thus, AR suppressed eIF4E phosphorylation, while the use of anti-androgens relieved this suppression, thereby triggering its increase. Additional investigation in human prostatectomy samples showed that increased eIF4E phosphorylation strongly correlated with the cell proliferation marker Ki67. SiRNA-mediated knock-down of eIF4E sensitized CRPC cells to RAD001+bicalutamide, while eIF4E overexpression induced resistance. Inhibition of eIF4E phosphorylation by treatment with CGP57380 (an inhibitor of MAPK interacting serine-threonine kinases Mnk1/2, the eIF4E upstream kinase) or inhibitors of ERK1/2, the upstream kinase regulating Mnk1/2, also sensitized CRPC cells to RAD001+bicalutamide. Examination of downstream targets of eIF4E-mediated translation, including survivin, demonstrated that eIF4E(S209) phosphorylation increased cap-independent translation whereas its inhibition restored cap-dependent translation which could be inhibited by mTOR inhibitors. Thus, our results demonstrate that while combinations of AR and mTOR inhibitors were effective in suppressing tumor growth by inhibiting both AR-induced transcription and mTOR-induced cap-dependent translation, pre-treatment with AR antagonists including bicalutamide increased eIF4E phosphorylation that induced resistance to combinations of AR and mTOR inhibitors by inducing cap-independent translation. We conclude that this resistance can be overcome by inhibiting eIF4E phosphorylation with Mnk1/2 or ERK1/2 inhibitors.

Human and feline adipose-derived mesenchymal stem cells have comparable phenotype, immunomodulatory functions, and transcriptome

Background

Adipose-derived mesenchymal stem cells (ASCs) are a promising cell therapy to treat inflammatory and immune-mediated diseases. Development of appropriate pre-clinical animal models is critical to determine safety and attain early efficacy data for the most promising therapeutic candidates. Naturally occurring diseases in cats already serve as valuable models to inform human clinical trials in oncologic, cardiovascular, and genetic diseases. The objective of this study was to complete a comprehensive side-by-side comparison of human and feline ASCs, with an emphasis on their immunomodulatory capacity and transcriptome.

Methods

Human and feline ASCs were evaluated for phenotype, immunomodulatory profile, and transcriptome. Additionally, transwells were used to determine the role of cell-cell contact in ASC-mediated inhibition of lymphocyte proliferation in both humans and cats.

Results

Similar to human ASCs, feline ASCs were highly proliferative at low passages and fit the minimal criteria of multipotent stem cells including a compatible surface protein phenotype, osteogenic capacity, and normal karyotype. Like ASCs from all species, feline ASCs inhibited mitogen-activated lymphocyte proliferation in vitro, with or without direct ASC-lymphocyte contact. Feline ASCs mimic human ASCs in their mediator secretion pattern, including prostaglandin E2, indoleamine 2,3 dioxygenase, transforming growth factor beta, and interleukin-6, all augmented by interferon gamma secretion by lymphocytes. The transcriptome of three unactivated feline ASC lines were highly similar. Functional analysis of the most highly expressed genes highlighted processes including: 1) the regulation of apoptosis; 2) cell adhesion; 3) response to oxidative stress; and 4) regulation of cell differentiation. Finally, feline ASCs had a similar gene expression profile to noninduced human ASCs.

Conclusions

Findings suggest that feline ASCs modulate lymphocyte proliferation using soluble mediators that mirror the human ASC secretion pattern. Uninduced feline ASCs have similar gene expression profiles to uninduced human ASCs, as revealed by transcriptome analysis. These data will help inform clinical trials using cats with naturally occurring diseases as surrogate models for human clinical trials in the regenerative medicine arena.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-017-0528-z) contains supplementary material, which is available to authorized users.

Microdose-Induced Drug-DNA Adducts as Biomarkers of Chemotherapy Resistance in Humans and Mice

We report progress on predicting tumor response to platinum-based chemotherapy with a novel mass spectrometry approach. Fourteen bladder cancer patients were administered one diagnostic microdose each of [¹⁴C]carboplatin (1% of the therapeutic dose). Carboplatin-DNA adducts were quantified by accelerator mass spectrometry in blood and tumor samples collected within 24 hours, and compared with subsequent chemotherapy response. Patients with the highest adduct levels were responders, but not all responders had high adduct levels. Four patient-derived bladder cancer xenograft mouse models were used to test the possibility that another drug in the regimen could cause a response. The mice were dosed with [¹⁴C]carboplatin or [¹⁴C]gemcitabine and the resulting drug-DNA adduct levels were compared with tumor response to chemotherapy. At least one of the drugs had to induce high drug-DNA adduct levels or create a synergistic increase in overall adducts to prompt a corresponding therapeutic response, demonstrating proof-of-principle for drug-DNA adducts as predictive biomarkers. Mol Cancer Ther; 16(2); 376-87. ©2016 AACR.

Reprogramming metabolism by histone methyltransferase NSD2 drives endocrine resistance via coordinated activation of pentose phosphate pathway enzymes

Metabolic reprogramming such as the aerobic glycolysis or Warburg effect is well recognized as a common feature of tumorigenesis. However, molecular mechanisms underlying metabolic alterations for tumor therapeutic resistance are poorly understood. Through gene expression profiling analysis we found that histone H3K36 methyltransferase NSD2/MMSET/WHSC1 expression was highly elevated in tamoxifen-resistant breast cancer cell lines and clinical tumors. IHC analysis indicated that NSD2 protein overexpression was associated with the disease recurrence and poor survival. Ectopic expression of NSD2 wild type, but not the methylase-defective mutant, drove endocrine resistance in multiple cell models and xenograft tumors. Mechanistically, NSD2 was recruited to and methylated H3K36me2 at the promoters of key glucose metabolic enzyme genes. Its overexpression coordinately up-regulated hexokinase 2 (HK2) and glucose-6-phosphate dehydrogenase (G6PD), two key enzymes of glycolysis and the pentose phosphate pathway (PPP), as well as TP53-induced glycolysis regulatory phosphatase TIGAR. Consequently, NSD2-driven tamoxifen-resistant cells and tumors displayed heightened PPP activity, elevated NADPH production, and reduced ROS level, without significantly altered glycolysis. These results illustrate a coordinated, epigenetic activation of key glucose metabolic enzymes in therapeutic resistance and nominate methyltransferase NSD2 as a potential therapeutic target for endocrine resistant breast cancer.

Decreased expression of let-7c is associated with non-response of muscle-invasive bladder cancer patients to neoadjuvant chemotherapy

The identification and development of biomarkers which predict response of muscle invasive bladder cancer (MIBC) patients to neoadjuvant chemotherapy would likely increase usage of this treatment option and thereby improve patient survival rates. MiRNA array and qRT-PCR validation was used to identify miRNA which are associated with response to neoadjuvant chemotherapy. RNA was extracted from a total of 41 archival, fully annotated, MIBC patient diagnostic biopsies (20 chemo-responders and 21 non-responders (response is defined as > 5 year survival rate and being pT0 post-chemotherapy)). Microarray and qPCR identified let-7c as being differentially expressed in chemo-responder versus non-responder patients. Patients with higher let-7c expression levels had significantly higher odds of responding to chemotherapy (p = 0.023, OR 2.493, 95% CI 1.121, 5.546), and assessment of let-7c levels allowed for prediction of patient response (AUC 0.72, positive predictive value 59%). Decreased let-7c was associated with MIBC incidence (p < 0.001), and significantly correlated with other related miRNA including those that were not differentially expressed between responders and non-responders. The combined data indicate let-7c plays a role in mediating chemoresistance to neoadjuvant chemotherapy in MIBC patients, and is a modest, yet clinically meaningful, predictor of patient response.

miR-124 and Androgen Receptor Signaling Inhibitors Repress Prostate Cancer Growth by Downregulating Androgen Receptor Splice Variants, EZH2, and Src

miR-124 targets the androgen receptor (AR) transcript, acting as a tumor suppressor to broadly limit the growth of prostate cancer. In this study, we unraveled the mechanisms through which miR-124 acts in this setting. miR-124 inhibited proliferation of prostate cancer cells in vitro and sensitized them to inhibitors of androgen receptor signaling. Notably, miR-124 could restore the apoptotic response of cells resistant to enzalutamide, a drug approved for the treatment of castration-resistant prostate cancer. We used xenograft models to examine the effects of miR-124 in vivo when complexed with polyethylenimine-derived nanoparticles. Intravenous delivery of miR-124 was sufficient to inhibit tumor growth and to increase tumor cell apoptosis in combination with enzalutamide. Mechanistic investigations revealed that miR-124 directly downregulated AR splice variants AR-V4 and V7 along with EZH2 and Src, oncogenic targets that have been reported to contribute to prostate cancer progression and treatment resistance. Taken together, our results offer a preclinical rationale to evaluate miR-124 for cancer treatment.

Development and Characterization of Bladder Cancer Patient-Derived Xenografts for Molecularly Guided Targeted Therapy

BACKGROUND

The overarching goal of this project is to establish a patient-derived bladder cancer xenograft (PDX) platform, annotated with deep sequencing and patient clinical information, to accelerate the development of new treatment options for bladder cancer patients. Herein, we describe the creation, initial characterization and use of the platform for this purpose.

METHODS AND FINDINGS

Twenty-two PDXs with annotated clinical information were established from uncultured unselected clinical bladder cancer specimens in immunodeficient NSG mice. The morphological fidelity was maintained in PDXs. Whole exome sequencing revealed that PDXs and parental patient cancers shared 92-97% of genetic aberrations, including multiple druggable targets. For drug repurposing, an EGFR/HER2 dual inhibitor lapatinib was effective in PDX BL0440 (progression-free survival or PFS of 25.4 days versus 18.4 days in the control, p = 0.007), but not in PDX BL0269 (12 days versus 13 days in the control, p = 0.16) although both expressed HER2. To screen for the most effective MTT, we evaluated three drugs (lapatinib, ponatinib, and BEZ235) matched with aberrations in PDX BL0269; but only a PIK3CA inhibitor BEZ235 was effective (p<0.0001). To study the mechanisms of secondary resistance, a fibroblast growth factor receptor 3 inhibitor BGJ398 prolonged PFS of PDX BL0293 from 9.5 days of the control to 18.5 days (p<0.0001), and serial biopsies revealed that the MAPK/ERK and PIK3CA-AKT pathways were activated upon resistance. Inhibition of these pathways significantly prolonged PFS from 12 day of the control to 22 days (p = 0.001). To screen for effective chemotherapeutic drugs, four of the first six PDXs were sensitive to the cisplatin/gemcitabine combination, and chemoresistance to one drug could be overcome by the other drug.

CONCLUSION

The PDX models described here show good correlation with the patient at the genomic level and known patient response to treatment. This supports further evaluation of the PDXs for their ability to accurately predict a patient's response to new targeted and combination strategies for bladder cancer.

Abstract 5242: Utilization of next-generation sequencing to identify clinically-relevant mutations in cell-free circulating tumor DNA from patients with advanced pancreatic cancer

Pancreatic cancer is a uniquely lethal malignancy characterized by frequent mutations in KRAS, CDKN2A, SMAD4, TP53 and many other genes. Molecular characterization is complicated by relatively few patients presenting with surgically resectable disease, frequent absence of metastases in easily accessible sites, and short patient survival. We have shown that KRAS mutation can be detected in cell-free, circulating tumor DNA (ctDNA) isolated from the plasma in a subset of patients and is associated with poor prognosis. The ability to simultaneously detect multiple pancreatic cancer-specific mutations in ctDNA would open a new avenue for detection of clinically-relevant mutations. We collected blood from 28 patients with advanced pancreatic cancer prior to treatment on a phase II clinical trial of pharmacodynamically separated gemcitabine and erlotinib. DNA was extracted from both plasma and available matched FFPE tumor specimens and evaluated with the GeneRead DNA QuantiMIZE System (Qiagen). The mutation status of 160 commonly-mutated genes was determined using an amplicon sequencing assay. Sequencing libraries were prepared from DNA samples (40 ng input) by targeted enrichment of exonic regions using the Qiagen GeneRead Human Comprehensive Cancer Panel, which encompasses &gt;744 kb genomic content with ∼8,000 amplicons. Next-generation sequencing (NGS) was performed on the Illumina MiSeq for validation analyses of a subset of matched tumor-ctDNA samples, and subsequently on the Illumina HiSeq 2500 for ultra-deep sequencing (1,000X) of the entire sample set. Read mapping, variant discovery, and functional annotation were performed with the Qiagen GeneRead Variant Calling Pipeline. The technical success of this sequencing assay for ctDNA, as well as FFPE DNA, was demonstrated by the resulting data meeting the expected NGS quality standards, including a high percentage of mappable reads (∼90%). In addition, the integrity of the sequencing data obtained from ctDNA samples was supported by detection of 82-94% of the variants found in each matched tumor. Somatic, non-synonymous variants were identified in 29 different genes and at allele frequencies typically &lt;0.5. While 52-68% of the mutations identified in the tumor specimen could also be detected in the cell-free ctDNA, not all mutations of potential clinical relevance in tumor specimens were detected in the ctDNA specimens. Updated results from ultra-deep NGS analysis will be presented. The results demonstrate the feasibility of using a new targeted NGS assay for the simultaneous identification of mutations in 160 cancer-related genes in ctDNA. The sensitivity and specificity of variant identification achieved with this technique are potentially clinically relevant, and its optimization could provide a true liquid biopsy for molecular characterization of pancreatic cancer.

Citation Format: Clifford G. Tepper, Ryan R. Davis, Stephenie Y. Liu, Rebekah A. Tsai, Irene M. Hutchins, Philip C. Mack, Thomas J. Semrad. Utilization of next-generation sequencing to identify clinically-relevant mutations in cell-free circulating tumor DNA from patients with advanced pancreatic 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 5242. doi:10.1158/1538-7445.AM2015-5242

Abnormal Mammary Development in 129:STAT1-Null Mice is Stroma-Dependent

Female 129:Stat1-null mice (129S6/SvEvTac-Stat1^tm1Rds homozygous) uniquely develop estrogen-receptor (ER)-positive mammary tumors. Herein we report that the mammary glands (MG) of these mice have altered growth and development with abnormal terminal end buds alongside defective branching morphogenesis and ductal elongation. We also find that the 129:Stat1-null mammary fat pad (MFP) fails to sustain the growth of 129S6/SvEv wild-type and Stat1-null epithelium. These abnormalities are partially reversed by elevated serum progesterone and prolactin whereas transplantation of wild-type bone marrow into 129:Stat1-null mice does not reverse the MG developmental defects. Medium conditioned by 129:Stat1-null epithelium-cleared MFP does not stimulate epithelial proliferation, whereas it is stimulated by medium conditioned by epithelium-cleared MFP from either wild-type or 129:Stat1-null females having elevated progesterone and prolactin. Microarrays and multiplexed cytokine assays reveal that the MG of 129:Stat1-null mice has lower levels of growth factors that have been implicated in normal MG growth and development. Transplanted 129:Stat1-null tumors and their isolated cells also grow slower in 129:Stat1-null MG compared to wild-type recipient MG. These studies demonstrate that growth of normal and neoplastic 129:Stat1-null epithelium is dependent on the hormonal milieu and on factors from the mammary stroma such as cytokines. While the individual or combined effects of these factors remains to be resolved, our data supports the role of STAT1 in maintaining a tumor-suppressive MG microenvironment.

Abstract 4036: Drug repurposing to treat melanoma brain metastases

Despite recent therapeutic advances in the management of patients with metastatic melanoma, brain metastases remain an intractable problem. It has proven difficult to identify and target single genes or pathways critical to brain metastasis formation. In this work we set out to explore a more global and preventive treatment approach to melanoma brain metastases within an established xenograft model of human melanoma. Mice were injected intracardially under ultrasound guidance and followed for six weeks with whole-body BLI and brain MRI. Tumor-bearing brains, adrenals, ovaries, and femurs were harvested and enzymatically dissociated before three tumor cell samples from each organ were flow-sorted and subjected to RNA sequencing. We developed a combined workflow of several independent computational and statistical analyses based on differential expression, and defined a brain metastasis gene signature of 54 upregulated and 54 downregulated genes. We then queried the Connectivity Map database using our 108-gene signature for candidate drugs, i.e. drugs that induce an opposite gene expression profile in various cancer cell lines. Three of the top ten drugs, already in use for other clinical conditions, showed significant efficacy in monolayer proliferation assays and colony forming assays with two brain-tropic melanoma cell lines and one brain-tropic lung cancer cell line. To examine these results in vivo, we used a highly standardized and predictive model system with automated MRI-based quantification of nanoparticle-labeled cells in the mouse brain following intracardiac injection of human melanoma cells. Treatment was started shortly after verification of comparable tumor cell exposure in the mouse brains and animals were monitored with whole-body BLI and brain MRI. Preliminary results showed promising therapeutic effects with respect to brain metastatic burden and survival, as well as acceptable toxicity profiles. We are currently validating these results on a larger scale in vivo, in other models, as well as applying systems biology and network modeling approaches to explore the fundamental mechanisms of action. Together, our results demonstrate a previously unrecognized potential for drug repurposing in the treatment of patients at risk of developing melanoma brain metastases or with clinically occult micrometastatic disease. Finding new uses for old drugs can greatly expedite translation to clinical practice; thus, further investigations are warranted to determine the safety, tolerability, and efficacy of these therapies.

Citation Format: Terje Sundstrøm, Jobin K. Varughese, Francisco Azuaje, Kjell Petersen, Clifford G. Tepper, Elizabeth Ingham, Lisa Even, Sarah Tam, Kai Ove Skaftnesmo, Morten Lund-Johansen, Rolf Bjerkvig, Katherine W. Ferrara, Frits A. Thorsen. Drug repurposing to treat melanoma brain metastases. [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 4036. doi:10.1158/1538-7445.AM2014-4036

The chromatin modification by SUMO-2/3 but not SUMO-1 prevents the epigenetic activation of key immune-related genes during Kaposi's sarcoma associated herpesvirus reactivation

BACKGROUND

SUMOylation, as part of the epigenetic regulation of transcription, has been intensively studied in lower eukaryotes that contain only a single SUMO protein; however, the functions of SUMOylation during mammalian epigenetic transcriptional regulation are largely uncharacterized. Mammals express three major SUMO paralogues: SUMO-1, SUMO-2, and SUMO-3 (normally referred to as SUMO-1 and SUMO-2/3). Herpesviruses, including Kaposi's sarcoma associated herpesvirus (KSHV), seem to have evolved mechanisms that directly or indirectly modulate the SUMO machinery in order to evade host immune surveillance, thus advancing their survival. Interestingly, KSHV encodes a SUMO E3 ligase, K-bZIP, with specificity toward SUMO-2/3 and is an excellent model for investigating the global functional differences between SUMO paralogues.

RESULTS

We investigated the effect of experimental herpesvirus reactivation in a KSHV infected B lymphoma cell line on genomic SUMO-1 and SUMO-2/3 binding profiles together with the potential role of chromatin SUMOylation in transcription regulation. This was carried out via high-throughput sequencing analysis. Interestingly, chromatin immunoprecipitation sequencing (ChIP-seq) experiments showed that KSHV reactivation is accompanied by a significant increase in SUMO-2/3 modification around promoter regions, but SUMO-1 enrichment was absent. Expression profiling revealed that the SUMO-2/3 targeted genes are primarily highly transcribed genes that show no expression changes during viral reactivation. Gene ontology analysis further showed that these genes are involved in cellular immune responses and cytokine signaling. High-throughput annotation of SUMO occupancy of transcription factor binding sites (TFBS) pinpointed the presence of three master regulators of immune responses, IRF-1, IRF-2, and IRF-7, as potential SUMO-2/3 targeted transcriptional factors after KSHV reactivation.

CONCLUSION

Our study is the first to identify differential genome-wide SUMO modifications between SUMO paralogues during herpesvirus reactivation. Our findings indicate that SUMO-2/3 modification near protein-coding gene promoters occurs in order to maintain host immune-related gene unaltered during viral reactivation.

Enhancing the effectiveness of androgen deprivation in prostate cancer by inducing Filamin A nuclear localization

As prostate cancer (CaP) is regulated by androgen receptor (AR) activity, metastatic CaP is treated with androgen deprivation therapy (ADT). Despite initial response, patients on ADT eventually progress to castration-resistant CaP (CRPC), which is currently incurable. We previously showed that cleavage of the 280 kDa structural protein Filamin A (FlnA) to a 90 kDa fragment, and nuclear localization of the cleaved product, sensitized CRPC cells to ADT. Hence, treatment promoting FlnA nuclear localization would enhance androgen responsiveness. Here, we show that FlnA nuclear localization induced apoptosis in CRPC cells during ADT, identifying it as a treatment tool in advanced CaP. Significantly, the natural product genistein combined polysaccharide (GCP) had a similar effect. Investigation of the mechanism of GCP-induced apoptosis showed that GCP induced FlnA cleavage and nuclear localization and that apoptosis resulting from GCP treatment was mediated by FlnA nuclear localization. Two main components of GCP are genistein and daidzein: the ability of GCP to induce G2 arrest was due to genistein whereas sensitivity to ADT stemmed from daidzein; hence, both were needed to mediate GCP's effects. FlnA cleavage is regulated by its phosphorylation; we show that ADT enhanced FlnA phosphorylation, which prevented its cleavage, whereas GCP inhibited FlnA phosphorylation, thereby sensitizing CaP cells to ADT. In a mouse model of CaP recurrence, GCP, but not vehicle, impeded relapse following castration, indicating that GCP, when administered with ADT, interrupted the development of CRPC. These results demonstrate the efficacy of GCP in promoting FlnA nuclear localization and enhancing androgen responsiveness in CaP.

Modeling truncated AR expression in a natural androgen responsive environment and identification of RHOB as a direct transcriptional target

Recent studies identifying putative truncated androgen receptor isoforms with ligand-independent activity have shed new light on the acquisition of androgen depletion independent (ADI) growth of prostate cancer. In this study, we present a model system in which a C-terminally truncated variant of androgen receptor (TC-AR) is inducibly expressed in LNCaP, an androgen-dependent cell line, which expresses little truncated receptor. We observed that when TC-AR is overexpressed, the endogenous full length receptor (FL-AR) is transcriptionally downmodulated. This in essence allows us to “replace” FL-AR with TC-AR and compare their individual properties in exactly the same genetic and cellular background, which has not been performed before. We show that the TC-AR translocates to the nucleus, activates transcription of AR target genes in the absence of DHT and is sufficient to confer ADI growth to the normally androgen dependent LNCaP line. We also show that while there is significant overlap in the genes regulated by FL- and TC-AR there are also differences in the respective suites of target genes with each AR form regulating genes that the other does not. Among the genes uniquely activated by TC-AR is RHOB which is shown to be involved in the increased migration and morphological changes observed in LN/TC-AR, suggesting a role of RHOB in the regulation of androgen-independent behavior of prostate cancer cells.

Abstract C11: Using GCP to improve initial response to androgen deprivation in prostate cancer

Recurrent prostate cancer (PCa) is treated with androgen deprivation therapy (ADT, chemical castration), but patients on this treatment frequently relapse, indicative of the advent of castration resistant prostate cancer (CRPC). Due to the multifocal nature of the disease, any one treatment may not affect all pathways altered in CRPC; therefore, we set out to delay CRPC by increasing the apoptotic rate during ADT. We previously published that Filamin A (FlnA) is localized to the nucleus in androgen-dependent cells, whereas its expression is lost from the nucleus in CRPC. Restoration of FlnA nuclear expression induced apoptosis in the absence of androgens. We now show that genistein combined polysaccharide (GCP), a combination of isoflavones, can induce FlnA translocation to the nucleus. GCP and its main component genistein previously failed to prevent progression in pre-prostatectomy patients with low-grade PCa. However, our new data, both in vitro and in an animal model, show that GCP impedes relapse following castration, and induces apoptosis in PCa cells undergoing ADT, by promoting FlnA cleavage and nuclear translocation. Investigation of the mechanism of GCP's effects on FlnA showed that ADT phosphorylates FlnA and prevents its cleavage, whereas GCP inhibits FlnA phosphorylation, thereby promoting its cleavage and nuclear translocation. Additional data show that nuclear localization of FlnA induces apoptosis during ADT by preventing androgen receptor (AR) stabilization and by suppression of the ErbB3/PI3K/Akt axis. Taken together, our results identify GCP as a putative therapeutic module to prolong the effectiveness of ADT in patients with metastatic prostate cancer.

Citation Format: Benjamin A. Mooso, Maria Mudryj, Ralph W. deVere White, Paramita M. Ghosh, Rosalinda M. Savoy, Jean P. Cheung, Ruth L. Vinall, Clifford G. Tepper, Yu Wang, Salma Siddiqui, Roble G. Bedolla, Margarita Mikhailova. Using GCP to improve initial response to androgen deprivation in prostate cancer [abstract]. In: Proceedings of the AACR Special Conference on Advances in Prostate Cancer Research; 2012 Feb 6-9; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2012;72(4 Suppl):Abstract nr C11.

Protein arginine methyltransferase 1-directed methylation of Kaposi sarcoma-associated herpesvirus latency-associated nuclear antigen

The Kaposi sarcoma-associated herpesvirus (KSHV) latency-associated nuclear antigen (LANA) is a multifunctional protein with roles in gene regulation and maintenance of viral latency. Post-translational modification of LANA is important for functional diversification. Here, we report that LANA is subject to arginine methylation by protein arginine methyltransferase 1 in vitro and in vivo. The major arginine methylation site in LANA was mapped to arginine 20. This site was mutated to either phenylalanine (bulky hydrophobic, constitutive methylated mimetic) or lysine (positively charged, non-arginine methylatable) residues. The significance of the methylation in LANA function was examined in both the isolated form and in the context of the viral genome through the generation of recombinant KSHV. In addition, authentic LANA binding sites on the KSHV episome in naturally infected cells were identified using a whole genome KSHV tiling array. Although mutation of the methylation site resulted in no significant difference in KSHV LANA subcellular localization, we found that the methylation mimetic mutation resulted in augmented histone binding in vitro and increased LANA occupancy at identified LANA target promoters in vivo. Moreover, a cell line carrying the methylation mimetic mutant KSHV showed reduced viral gene expression relative to controls both in latency and in the course of reactivation. These results suggest that residue 20 is important for modulation of a subset of LANA functions and properties of this residue, including the hydrophobic character induced by arginine methylation, may contribute to the observed effects.

Dual blockade of PKA and NF-κB inhibits H2 relaxin-mediated castrate-resistant growth of prostate cancer sublines and induces apoptosis

We previously demonstrated that H2 relaxin (RLN2) facilitates castrate-resistant (CR) growth of prostate cancer (CaP) cells through PI3K/Akt/β-catenin-mediated activation of the androgen receptor (AR) pathway. As inhibition of this pathway caused only ~50% reduction in CR growth, the goal of the current study was to identify additional RLN2-activated pathways that contribute to CR growth. Next-generation sequencing-based transcriptome and gene ontology analyses comparing LNCaP stably transfected with RLN2 versus LNCaP-vector identified differential expression of genes associated with cell proliferation (12.7% of differentially expressed genes), including genes associated with the cyclic adenosine monophosphate/protein kinase A (cAMP/PKA) and nuclear factor-kappaB (NF-κB) pathways. Subsequent molecular analyses confirmed that the cAMP/PKA and NF-κB pathways play a role in facilitating H2 relaxin-mediated CR growth of CaP cells. Inhibition of PKA-attenuated RLN2-mediated AR activity inhibited proliferation and caused a small but significant increase in apoptosis. Combined inhibition of the PKA and NF-κB signaling pathways via inhibition of PKA and Akt induced significant apoptosis and dramatically reduced clonogenic potential, outperforming docetaxel, the standard of care treatment for CR CaP. Immunohistochemical analysis of tissue microarrays in combination with multispectral quantitative imaging comparing RLN2 levels in patients with benign prostatic hyperplasia (BPH), prostatic intraepithelial neoplasia, and CaP determined that RLN2 is significantly upregulated in CaP vs BPH (p = 0.002). The combined data indicate RLN2 overexpression is frequent in CaP patients and provides a growth advantage to CaP cells. A near-complete inhibition of RLN2-induced CR growth can be achieved by simultaneous blockade of both pathways.

Recombinant origin of the retrovirus XMRV

The retrovirus XMRV (xenotropic murine leukemia virus-related virus) has been detected in human prostate tumors and in blood samples from patients with chronic fatigue syndrome, but these findings have not been replicated. We hypothesized that an understanding of when and how XMRV first arose might help explain the discrepant results. We studied human prostate cancer cell lines CWR22Rv1 and CWR-R1, which produce XMRV virtually identical to the viruses recently found in patient samples, as well as their progenitor human prostate tumor xenograft (CWR22) that had been passaged in mice. We detected XMRV infection in the two cell lines and in the later passage xenografts, but not in the early passages. In particular, we found that the host mice contained two proviruses, PreXMRV-1 and PreXMRV-2, which share 99.92% identity with XMRV over >3.2-kilobase stretches of their genomes. We conclude that XMRV was not present in the original CWR22 tumor but was generated by recombination of two proviruses during tumor passaging in mice. The probability that an identical recombinant was generated independently is negligible (~10(-12)); our results suggest that the association of XMRV with human disease is due to contamination of human samples with virus originating from this recombination event.

Abstract 5040: Dysregulation of the mTOR/AKT pathway in serum tumor DNA correlates with primary and acquired resistances to erlotinib in advanced NSCLC patients

Non-small cell lung cancer (NSCLC) is the most common and lethal cancer worldwide. Erlotinib, an oral epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI), is the first molecularly targeted agent that has demonstrated modest yet comparable survival benefit to chemotherapy in unselected patients with advanced NSCLC after failing first-line chemotherapy. However, all patients eventually die from disease progression and a cure does not currently exist, even in patients with NSCLC tumors harboring EGFR TKI-sensitive EGFR mutations and achieving an initially dramatic tumor response. We previously demonstrated that dysregulation of the EGFR/mTOR/AKT signaling pathway contributes primarily to the acquired resistance to erlotinib in an erlotinib-resistant clone H3255R#2 (EGFRWT/WT), which was derived from the parental, erlotinib-sensitive human lung adenocarcinoma cell line H3255 (EGFRL858R/WT). To gain further molecular insights into the resistance mechanisms, we explored genome-wide alterations in genomic DNA (gDNA) from erlotinib-resistant cells as compared to parental cells using the Affymetrix Human SNP 6.0 array platform, which contains approximately one million probes for the detection of single nucleotide polymorphisms (SNPs) and copy number variants (CNVs). We found that significant alterations were simultaneously present in several core functional pathways, including ErbB, mTOR/AKT, apoptosis, and cell cycle, as well as EMT, stem cell and metastasis related genes. Selected targets have been validated in vitro. Serum tumor DNA has emerged as an easily accessible and stable source of tumor biospecimens for advanced NSCLC patients and has been used for detecting somatic mutations in EGFR and K-Ras genes either directly or amplified by high fidelity whole genome amplification technology. We further determined whether this genome-wide array-based platform could be used to clinically assess the drug resistance mechanisms in advanced NSCLC patients. We analyzed the genomic alterations in two paired serum tumor DNA samples obtained before treatment and at treatment failure from NSCLC patients with primary or secondary resistance to erlotinib on a clinical trial (clinicaltrials.gov, identifier: NCT00950365). Of particular interest, we found that there were similar changes in the gDNAs from erlotinib-resistant patients’ sera and gDNA from R#2 cells within the mTOR/AKT pathway, including amplification of PI3K, AMPK, and VEGF genes, and deletion of RSK genes. Analyses on more banked, paired serum tumor DNA samples from patients enrolled in the same trial are ongoing. Our results support targeting the mTOR/AKT and/or VEGF pathway as a strategy to overcome clinical resistance to EGFR TKIs and serum tumor DNA could be a useful surrogate to assessing resistance mechanisms to therapy in advanced NSCLC patients.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 5040. doi:10.1158/1538-7445.AM2011-5040

miR-125b promotes growth of prostate cancer xenograft tumor through targeting pro-apoptotic genes

BACKGROUND

Increasing evidence demonstrates that aberrantly regulated microRNAs (miRNAs) contribute to the initiation and progression of human cancer. We previously have demonstrated that miR-125b stimulated the growth of prostate cancer (CaP) cells. In this study, we further determined the influence of miR-125b on the pathogenesis of CaP.

METHODS

To evaluate the effect of miR-125b on xenograft tumor growth, male athymic mice were subcutaneously injected with PC-346C-miR-125b cells that stably overexpressed miR-125b. Potential direct target transcripts of miR-125b were identified using a bioinformatics approach and three miR-125b targeted molecules were confirmed by means of biochemical analyses.

RESULTS

Enforced expression of miR-125b promoted tumor growth in both intact and castrated male nude mice. In an effort to define the molecular mechanism(s) mediating its tumor growth properties, we found that miR-125b directly targets eight transcripts, including three key pro-apoptotic genes: p53, Puma, and Bak1. Increasing the abundance of miR-125b resulted in a dramatic decrease in the levels of these three proteins in CaP cells. A direct repressive effect on each of these was supported by the ability of miR-125b to significantly reduce the activity of luciferase reporters containing their 3'-untranslated regions of each gene encompassing the miR-125b-binding sites. Additionally, we found that repression of miR-125b activity was able to sensitize CaP cells to different therapeutic interventions.

CONCLUSION

Data obtained in this study demonstrate that miR-125b promotes growth of prostatic xenograft tumors by down-regulating three key pro-apoptotic genes. This suggests that miR-125b is oncogenic and makes it an attractive therapeutic target in CaP.

Genome-wide analysis of androgen receptor binding and gene regulation in two CWR22-derived prostate cancer cell lines

Prostate carcinoma (CaP) is a heterogeneous multifocal disease where gene expression and regulation are altered not only with disease progression but also between metastatic lesions. The androgen receptor (AR) regulates the growth of metastatic CaPs; however, sensitivity to androgen ablation is short lived, yielding to emergence of castrate-resistant CaP (CRCaP). CRCaP prostate cancers continue to express the AR, a pivotal prostate regulator, but it is not known whether the AR targets similar or different genes in different castrate-resistant cells. In this study, we investigated AR binding and AR-dependent transcription in two related castrate-resistant cell lines derived from androgen-dependent CWR22-relapsed tumors: CWR22Rv1 (Rv1) and CWR-R1 (R1). Expression microarray analysis revealed that R1 and Rv1 cells had significantly different gene expression profiles individually and in response to androgen. In contrast, AR chromatin immunoprecipitation (ChIP) combined with promoter DNA microarrays (ChIP-on-chip) studies showed that they have a similar AR-binding profile. Coupling of the microarray study with ChIP-on-chip analysis identified direct AR targets. The most prominent function of transcripts that were direct AR targets was transcriptional regulation, although only one transcriptional regulator, CCAAT/enhancer binding protein δ, was commonly regulated in both lines. Our results indicate that the AR regulates the expression of different transcripts in the two lines, and demonstrate the versatility of the AR-regulated gene expression program in prostate tumors.

ANCCA/ATAD2 overexpression identifies breast cancer patients with poor prognosis, acting to drive proliferation and survival of triple-negative cells through control of B-Myb and EZH2

Chromatin coregulators are important factors in tumorigenesis and cancer progression. ANCCA is an AAA+ ATPase and a bromodomain-containing nuclear coactivator for the estrogen and androgen receptors that is crucial for assembly of chromatin-modifying complexes and proliferation of hormone-responsive cancer cells. In this study, we show that ANCCA is overexpressed in >70% of breast tumors and that its high protein level correlates well with tumor histologic grades (P<0.0001), highlighting ANCCA as a prognostic factor for poor overall survival and disease recurrence. Strikingly, high-level ANCCA correlated with triple-negative tumors that represent highly aggressive disease. Analysis of ANCCA transcript levels in multiple expression profiles of breast cancer identified ANCCA as a common signature gene, indicating that elevated transcripts also strongly correlate with tumor metastasis and poor survival. Biological and mechanistic investigations revealed that ANCCA is crucial for proliferation and survival of triple-negative/basal-like cancer cells and that it controls the expression of B-Myb, histone methyltransferase EZH2, and an Rb-E2F core program for proliferation, along with a subset of key mitotic kinesins and cell survival genes (IRS2, VEGF, and Akt1). In particular, ANCCA overexpression correlated strongly with EZH2 in tumors. Our results suggest that ANCCA may integrate multiple oncogenic programs in breast cancer, serving in particular as a prognostic marker and a therapeutic target for triple-negative cancers.