The androgen receptor is a therapeutic target in desmoplastic small round cell sarcoma

Desmoplastic small round cell tumor (DSRCT) is an aggressive, usually incurable sarcoma subtype that predominantly occurs in post-pubertal young males. Recent evidence suggests that the androgen receptor (AR) can promote tumor progression in DSRCTs. However, the mechanism of AR-induced oncogenic stimulation remains undetermined. Herein, we demonstrate that enzalutamide and AR-directed antisense oligonucleotides (AR-ASO) block 5α-dihydrotestosterone (DHT)-induced DSRCT cell proliferation and reduce xenograft tumor burden. Gene expression analysis and chromatin immunoprecipitation sequencing (ChIP-seq) were performed to elucidate how AR signaling regulates cellular epigenetic programs. Remarkably, ChIP-seq revealed novel DSRCT-specific AR DNA binding sites adjacent to key oncogenic regulators, including WT1 (the C-terminal partner of the pathognomonic fusion protein) and FOXF1. Additionally, AR occupied enhancer sites that regulate the Wnt pathway, neural differentiation, and embryonic organ development, implicating AR in dysfunctional cell lineage commitment. Our findings have direct clinical implications given the widespread availability of FDA-approved androgen-targeted agents used for prostate cancer.

Androgen receptor can promote tumour progression in desmoplastic small round cell tumour (DSRCT), an aggressive paediatric malignancy that predominantly affects young males. Here, the authors show that DSRCT is an AR-driven malignancy and sensitive to androgen deprivation therapy

Chromatin state dynamics confers specific therapeutic strategies in enhancer subtypes of colorectal cancer

OBJECTIVE

Enhancer aberrations are beginning to emerge as a key epigenetic feature of colorectal cancers (CRC), however, a comprehensive knowledge of chromatin state patterns in tumour progression, heterogeneity of these patterns and imparted therapeutic opportunities remain poorly described.

DESIGN

We performed comprehensive epigenomic characterisation by mapping 222 chromatin profiles from 69 samples (33 colorectal adenocarcinomas, 4 adenomas, 21 matched normal tissues and 11 colon cancer cell lines) for six histone modification marks: H3K4me3 for Pol II-bound and CpG-rich promoters, H3K4me1 for poised enhancers, H3K27ac for enhancers and transcriptionally active promoters, H3K79me2 for transcribed regions, H3K27me3 for polycomb repressed regions and H3K9me3 for heterochromatin.

RESULTS

We demonstrate that H3K27ac-marked active enhancer state could distinguish between different stages of CRC progression. By epigenomic editing, we present evidence that gains of tumour-specific enhancers for crucial oncogenes, such as ASCL2 and FZD10, was required for excessive proliferation. Consistently, combination of MEK plus bromodomain inhibition was found to have synergistic effects in CRC patient-derived xenograft models. Probing intertumour heterogeneity, we identified four distinct enhancer subtypes (EPIgenome-based Classification, EpiC), three of which correlate well with previously defined transcriptomic subtypes (consensus molecular subtypes, CMSs). Importantly, CMS2 can be divided into two EpiC subgroups with significant survival differences. Leveraging such correlation, we devised a combinatorial therapeutic strategy of enhancer-blocking bromodomain inhibitors with pathway-specific inhibitors (PARPi, EGFRi, TGFβi, mTORi and SRCi) for EpiC groups.

CONCLUSION

Our data suggest that the dynamics of active enhancer underlies CRC progression and the patient-specific enhancer patterns can be leveraged for precision combination therapy.

KMT2D deficiency confers a therapeutic vulnerability to glycolytic and IGFR inhibitors in melanoma

We reported that histone H3 lysine (K) 4 methyltransferase, KMT2D, serves as a potent tumor-suppressor in melanoma, which was identified via in vivo epigenome-focused RNA interference (RNAi) screen. KMT2D-deficient tumors show substantial reprogramming of key metabolic pathways including glycolysis via reduction of H3K4me1 (Histone H3K4 mono-methylation)-marked active enhancers, conferring sensitivity to inhibitors of glycolysis and IGFR (Insulin Growth Factor Receptor) pathway.

Reprogramming of bivalent chromatin states in NRAS mutant melanoma suggests PRC2 inhibition as a therapeutic strategy

The dynamic evolution of chromatin state patterns during metastasis, their relationship with bona fide genetic drivers, and their therapeutic vulnerabilities are not completely understood. Combinatorial chromatin state profiling of 46 melanoma samples reveals an association of NRAS mutants with bivalent histone H3 lysine 27 trimethylation (H3K27me3) and Polycomb repressive complex 2. Reprogramming of bivalent domains during metastasis occurs on master transcription factors of a mesenchymal phenotype, including ZEB1, TWIST1, and CDH1. Resolution of bivalency using pharmacological inhibition of EZH2 decreases invasive capacity of melanoma cells and markedly reduces tumor burden in vivo, specifically in NRAS mutants. Coincident with bivalent reprogramming, the increased expression of pro-metastatic and melanocyte-specific cell-identity genes is associated with exceptionally wide H3K4me3 domains, suggesting a role for this epigenetic element. Overall, we demonstrate that reprogramming of bivalent and broad domains represents key epigenetic alterations in metastatic melanoma and that EZH2 plus MEK inhibition may provide a promising therapeutic strategy for NRAS mutant melanoma patients.

Enhancer Reprogramming Confers Dependence on Glycolysis and IGF Signaling in KMT2D Mutant Melanoma

Histone methyltransferase KMT2D harbors frequent loss-of-function somatic point mutations in several tumor types, including melanoma. Here, we identify KMT2D as a potent tumor suppressor in melanoma through an in vivo epigenome-focused pooled RNAi screen and confirm the finding by using a genetically engineered mouse model (GEMM) based on conditional and melanocyte-specific deletion of KMT2D. KMT2D-deficient tumors show substantial reprogramming of key metabolic pathways, including glycolysis. KMT2D deficiency aberrantly upregulates glycolysis enzymes, intermediate metabolites, and glucose consumption rates. Mechanistically, KMT2D loss causes genome-wide reduction of H3K4me1-marked active enhancer chromatin states. Enhancer loss and subsequent repression of IGFBP5 activates IGF1R-AKT to increase glycolysis in KMT2D-deficient cells. Pharmacological inhibition of glycolysis and insulin growth factor (IGF) signaling reduce proliferation and tumorigenesis preferentially in KMT2D-deficient cells. We conclude that KMT2D loss promotes tumorigenesis by facilitating an increased use of the glycolysis pathway for enhanced biomass needs via enhancer reprogramming, thus presenting an opportunity for therapeutic intervention through glycolysis or IGF pathway inhibitors.

Abstract 4493: Enhancer reprogramming contributes to anti-PD1 resistance in melanoma

Immune checkpoint blockade therapy has improved clinical responses and long-term survival benefit for patients with advanced melanoma, however the response rate is modest and a large fraction of treated patients do not experience clinical benefits. Therefore, there is tremendous need to identify combination strategies to improve responses and to overcome resistance to therapy. Emerging data suggest that epigenetic drugs can improve the responses to immunotherapy. However, we have limited understanding of epigenetic mechanisms that characterize responses to Immune checkpoint blockade therapy. Therefore, we generated comprehensive epigenomic landscapes of 36 samples from anti PD-1 treated metastatic melanoma patients by profiling 6 histone markers. To determine correlation of epigenetic features with gene expression, we generated RNA-Access data for 12 matched samples. We determined chromatin states using ChromHMM and ChromHMM profiling consolidated using Epilogos. Analysis of chromatin state differences and associated individual mark profiles with response rate suggested that pre-treatment samples from anti PD-1 non-responsive patients contain higher active enhancer state (enriched for H3K27Ac) compared to responsive patients. Many of these enhancers targeted key regulators of pathways that are shown to mediate resistance to immune checkpoint blockade therapy. Importantly, aberrant expression of these genes correlated well with enhancer gains. Inhibition of enhancers with bromodomain inhibitor along with anti PD-1 significantly decreased the tumor volume by increased T cell infiltration. Together, these findings reveal that enhancer gains on key oncogenes associate with poor response to Immune checkpoint therapy which could be potentially used for stratifying responder and resistant lesions.

Citation Format: Mayinuer Maitituoheti, Ming Tang, Christopher J. Terranova, Emily Keung, Katarzyna J. Tomczak, Jennifer Wargo, Kunal Rai. Enhancer reprogramming contributes to anti-PD1 resistance in melanoma [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 4493.

KMT2D Deficiency Impairs Super-Enhancers to Confer a Glycolytic Vulnerability in Lung Cancer

Epigenetic modifiers frequently harbor loss-of-function mutations in lung cancer, but their tumor-suppressive roles are poorly characterized. Histone methyltransferase KMT2D (a COMPASS-like enzyme, also called MLL4) is among the most highly inactivated epigenetic modifiers in lung cancer. Here, we show that lung-specific loss of Kmt2d promotes lung tumorigenesis in mice and upregulates pro-tumorigenic programs, including glycolysis. Pharmacological inhibition of glycolysis preferentially impedes tumorigenicity of human lung cancer cells bearing KMT2D-inactivating mutations. Mechanistically, Kmt2d loss widely impairs epigenomic signals for super-enhancers/enhancers, including the super-enhancer for the circadian rhythm repressor Per2. Loss of Kmt2d decreases expression of PER2, which regulates multiple glycolytic genes. These findings indicate that KMT2D is a lung tumor suppressor and that KMT2D deficiency confers a therapeutic vulnerability to glycolytic inhibitors.

Atypical plant homeodomain of UBR7 functions as an H2BK120Ub ligase and breast tumor suppressor

The roles of Plant Homeodomain (PHD) fingers in catalysis of histone modifications are unknown. We demonstrated that the PHD finger of Ubiquitin Protein Ligase E3 Component N-Recognin7 (UBR7) harbors E3 ubiquitin ligase activity toward monoubiquitination of histone H2B at lysine120 (H2BK120Ub). Purified PHD finger or full-length UBR7 monoubiquitinated H2BK120 in vitro, and loss of UBR7 drastically reduced H2BK120Ub genome-wide binding sites in MCF10A cells. Low UBR7 expression was correlated with occurrence of triple-negative breast cancer and metastatic tumors. Consistently, UBR7 knockdown enhanced the invasiveness, induced epithelial-to-mesenchymal transition and promoted metastasis. Conversely, ectopic expression of UBR7 restored these cellular phenotypes and reduced tumor growth. Mechanistically, UBR7 loss reduced H2BK120Ub levels on cell adhesion genes, including CDH4, and upregulated the Wnt/β-Catenin signaling pathway. CDH4 overexpression could partially revert UBR7-dependent cellular phenotypes. Collectively, our results established UBR7 as a histone H2B monoubiquitin ligase that suppresses tumorigenesis and metastasis of triple-negative breast cancer.

An Integrated Platform for Genome-wide Mapping of Chromatin States Using High-throughput ChIP-sequencing in Tumor Tissues

Histone modifications constitute a major component of the epigenome and play important regulatory roles in determining the transcriptional status of associated loci. In addition, the presence of specific modifications has been used to determine the position and identity non-coding functional elements such as enhancers. In recent years, chromatin immunoprecipitation followed by next generation sequencing (ChIP-seq) has become a powerful tool in determining the genome-wide profiles of individual histone modifications. However, it has become increasingly clear that the combinatorial patterns of chromatin modifications, referred to as Chromatin States, determine the identity and nature of the associated genomic locus. Therefore, workflows consisting of robust high-throughput (HT) methodologies for profiling a number of histone modification marks, as well as computational analyses pipelines capable of handling myriads of ChIP-Seq profiling datasets, are needed for comprehensive determination of epigenomic states in large number of samples. The HT-ChIP-Seq workflow presented here consists of two modules: 1) an experimental protocol for profiling several histone modifications from small amounts of tumor samples and cell lines in a 96-well format; and 2) a computational data analysis pipeline that combines existing tools to compute both individual mark occupancy and combinatorial chromatin state patterns. Together, these two modules facilitate easy processing of hundreds of ChIP-Seq samples in a fast and efficient manner. The workflow presented here is used to derive chromatin state patterns from 6 histone mark profiles in melanoma tumors and cell lines. Overall, we present a comprehensive ChIP-seq workflow that can be applied to dozens of human tumor samples and cancer cell lines to determine epigenomic aberrations in various malignancies.

Systematic Epigenomic Analysis Reveals Chromatin States Associated with Melanoma Progression

The extent and nature of epigenomic changes associated with melanoma progression is poorly understood. Through systematic epigenomic profiling of 35 epigenetic modifications and transcriptomic analysis, we define chromatin state changes associated with melanomagenesis by using a cell phenotypic model of non-tumorigenic and tumorigenic states. Computation of specific chromatin state transitions showed loss of histone acetylations and H3K4me2/3 on regulatory regions proximal to specific cancer-regulatory genes in important melanoma-driving cell signaling pathways. Importantly, such acetylation changes were also observed between benign nevi and malignant melanoma human tissues. Intriguingly, only a small fraction of chromatin state transitions correlated with expected changes in gene expression patterns. Restoration of acetylation levels on deacetylated loci by histone deacetylase (HDAC) inhibitors selectively blocked excessive proliferation in tumorigenic cells and human melanoma cells, suggesting functional roles of observed chromatin state transitions in driving hyperproliferative phenotype. Through these results, we define functionally relevant chromatin states associated with melanoma progression.

EMDomics: a robust and powerful method for the identification of genes differentially expressed between heterogeneous classes

MOTIVATION

A major goal of biomedical research is to identify molecular features associated with a biological or clinical class of interest. Differential expression analysis has long been used for this purpose; however, conventional methods perform poorly when applied to data with high within class heterogeneity.

RESULTS

To address this challenge, we developed EMDomics, a new method that uses the Earth mover's distance to measure the overall difference between the distributions of a gene's expression in two classes of samples and uses permutations to obtain q-values for each gene. We applied EMDomics to the challenging problem of identifying genes associated with drug resistance in ovarian cancer. We also used simulated data to evaluate the performance of EMDomics, in terms of sensitivity and specificity for identifying differentially expressed gene in classes with high within class heterogeneity. In both the simulated and real biological data, EMDomics outperformed competing approaches for the identification of differentially expressed genes, and EMDomics was significantly more powerful than conventional methods for the identification of drug resistance-associated gene sets. EMDomics represents a new approach for the identification of genes differentially expressed between heterogeneous classes and has utility in a wide range of complex biomedical conditions in which sample classes show within class heterogeneity.

AVAILABILITY AND IMPLEMENTATION

The R package is available at http://www.bioconductor.org/packages/release/bioc/html/EMDomics.html.

Abstract 2172: Earth mover's distance for the identification of genes associated with drug resistance in cancer

Conventional methods for differential gene expression analysis perform well when intra-class heterogeneity is low and inter-class heterogeneity is high. However, many problems in biology and biomedicine, such as drug resistance in cancer, contain samples that show both significant intra- and inter-class heterogeneity. Conventional methods, which use means and variances to compute test statistics, lack power to identify genes differentially expressed between classes in these cases. To address this challenge, we developed EMDomics, a new method for differential gene expression analysis designed to perform well in the setting of intra-class heterogeneity.

EMDomics uses the Earth mover's distance (EMD) to measure the overall difference between the distribution of a gene's expression in two classes of samples and uses permutations to estimate false discovery rates and obtain q-values for each gene. To evaluate the theoretical basis for EMDomics, we model heterogeneous mechanisms of drug resistance using simulated data and compare the performance of EMDomics to the commonly used conventional methods (SAM and Limma), in terms of sensitivity and specificity for identifying genes truly associated with drug resistance in the simulation. To test EMDomics on real biological data, we applied it to the challenging problem of identifying genes associated with drug response in ovarian cancer, using data from The Cancer Genome Atlas.

In both the simulated and real biological data, EMDomics outperformed the competing approaches for the identification of differentially expressed genes. Using simulated data, EMDomics yielded higher sensitivity and precision for highly heterogeneous data. Using real data, EMDomics was able to identify genes that are highly relevant for ovarian cancer biology, which were not identified by the conventional methods. Also, applying gene set enrichment analysis showed that most highly enriched gene sets includes pathways known to play critical roles in ovarian cancer pathogenesis. The most enriched gene set identified by the EMDomics analysis is a set of genes down-regulated in cancer cell lines with mutated TP53. Other gene sets identified as highly enriched by the EMDomics analysis, include gene sets related to LEF1, BMI1, KRAS, EZH2, and PTEN, and pathways related to cell-cell junction organization, cell-cell communication, WNT signaling, and extracellular matrix organization.

EMDomics represents a new approach for the identification of genes differentially expressed between heterogeneous classes. It is a robust non-parametric method, which does not make any assumptions about the distributions or differences between the two classes being compared, and thus has significantly more power than conventional approaches for identifying differential ‘Omics features between heterogeneous classes. The method can be applied in a wide variety of settings to compare distributions of ‘Omics data between two classes.

Citation Format: Sheida Nabavi, Daniel Schmolze, Mayinuer Maitituoheti, Andrew H. Beck. Earth mover's distance for the identification of genes associated with drug resistance in 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 2172. doi:10.1158/1538-7445.AM2015-2172

Twist2 contributes to cisplatin-resistance of ovarian cancer through the AKT/GSK-3β signaling pathway

Cisplatin is regularly used in the treatment of ovarian cancer. However, the drug only provides a modest survival advantage, primarily due to chemoresistance and the upregulation of antiapoptotic machineries in ovarian cancer cells. Therefore, targeting the mechanisms responsible for cisplatin resistance in ovarian cancer cells may improve the therapeutic outcomes. Twist basic helix-loop-helix transcription factor 2 (Twist2) is a novel zinc finger transcription factor that has been indicated to be an important inducer of epithelial-mesenchymal transition, which has been shown to be involved in various phases of tumorigenicity and progression. However, whether Twist2 suppression increases the chemosensitivity of ovarian cancer cells to chemotherapeutic agents remains unclear. In the present study, Twist2 expression was found to differ between human ovarian cisplatin-sensitive cancer cell line, OV2008, and the resistant variant, C13K cells. Twist2 plasmids or RNA interference were then utilized to alter Twist2 expression in OV2008 or C13K cells, respectively, to further assess apoptosis, cell viability and cell growth, as well as a possible mechanism. The results of the present study indicated that Twist2 plays a crucial role in the chemoresistance of ovarian cancer. In addition, the downregulation of Twist2 expression may facilitate apoptosis and recover the sensitivity of chemoresistant ovarian cancer through the protein kinase B/glycogen synthase kinase-3β pathway. Therefore, Twist2 depletion may be a promising approach to ovarian cancer therapy.

Soluble B and T lymphocyte attenuator possesses antitumor effects and facilitates heat shock protein 70 vaccine-triggered antitumor immunity against a murine TC-1 cervical cancer model in vivo

B and T lymphocyte attenuator (BTLA)-herpesvirus entry mediator (HVEM) signaling coinhibitory pathway is believed to impair antitumor immune competences. An intriguing unresolved question is whether blockade of BTLA-HVEM guides an effective therapeutic tool against established tumors. To address this issue, we constructed a eukaryotic expression plasmid (psBTLA) that expressed the extracellular domain of murine BTLA (soluble form of BTLA), which could bind HVEM, the ligand of BTLA, and block BTLA-HVEM interactions. The data in this study showed that treatment by injection of psBTLA resulted in down-regulation of IL-10 and TGF-beta and promotion of dendritic cell function by increasing the expression of B7-1 and IL-12, but the adaptive antitumor immune responses achieved by psBTLA administration alone were limited and could not eradicate the tumor effectively. Next, we evaluated the immunotherapeutic efficacy and mechanism of combination therapy of heat shock protein 70 (HSP70) vaccine/psBTLA by using murine TC-1 cervical cancer mice as an ectopic tumor model. Our in vivo studies revealed that treatment with HSP70 vaccine alone did not lead to satisfactory tumor growth inhibition, whereas cotreatment with psBTLA significantly improved antitumor immunity and compensated the deficiency of HSP70 vaccine by increasing the expression of Th1 cytokines, IL-2, and IFN-gamma and decreasing transcription levels of IL-10, TGF-beta, and Foxp3 in the tumor microenvironment. Taken together, our findings indicate that blocking the BTLA-HVEM interaction with sBTLA enhances antitumor efficacy and results in a significant synergistic effect against existent tumor cells in vivo when combined with the HSP70 vaccine.