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Purpose: On the basis of preclinical evidence of epigenetic contribution to sensitivity and resistance to immune checkpoint inhibitors (ICI), we hypothesized that guadecitabine (hypomethylating agent) and atezolizumab [anti–programmed cell death ligand 1 (PD-L1)] together would potentiate a clinical response in patients with metastatic urothelial carcinoma (UC) unresponsive to initial immune checkpoint blockade therapy. Patients and Methods: We designed a single arm phase II study (NCT03179943) with a safety run-in to identify the recommended phase II dose of the combination therapy of guadecitabine and atezolizumab. Patients with recurrent/advanced UC who had previously progressed on ICI therapy with programmed cell death protein 1 or PD-L1 targeting agents were eligible. Preplanned correlative analysis was performed to characterize peripheral immune dynamics and global DNA methylation, transcriptome, and immune infiltration dynamics of patient tumors. Results: Safety run-in enrolled 6 patients and phase II enrolled 15 patients before the trial was closed for futility. No dose-limiting toxicity was observed. Four patients, with best response of stable disease (SD), exhibited extended tumor control (8–11 months) and survival (>14 months). Correlative analysis revealed lack of DNA demethylation in tumors after 2 cycles of treatment. Increased peripheral immune activation and immune infiltration in tumors after treatment correlated with progression-free survival and SD. Furthermore, high IL6 and IL8 levels in the patients’ plasma was associated with short survival. Conclusions: No RECIST responses were observed after combination therapy in this trial. Although we could not detect the anticipated tumor-intrinsic effects of guadecitabine, the addition of hypomethylating agent to ICI therapy induced immune activation in a few patients, which associated with longer patient survival.

Supplementary Figure 8: PD-L1 levels in tumor or tumor microenvironment does not associate with tumor progression or control.

Supplementary TablesSupplementary Table 1: Patient and tumor sample informationSupplementary Table 2: Tumor mutation burdenSupplementary Table 3: Unfiltered whole exome sequencing mutation analysisSupplementary Table 4: Filtered whole exome sequencing mutation analysisSupplementary Table 5: Immunohistochemistry scores of tumorsSupplementary Table 6: FACS panel for PBMC analysisSupplementary Table 7: Geometric mean fluorescence intensity (GMFI) from PBMC FACSSupplementary Table 8: Representativeness of Study Participants

Purpose:On the basis of preclinical evidence of epigenetic contribution to sensitivity and resistance to immune checkpoint inhibitors (ICI), we hypothesized that guadecitabine (hypomethylating agent) and atezolizumab [anti–programmed cell death ligand 1 (PD-L1)] together would potentiate a clinical response in patients with metastatic urothelial carcinoma (UC) unresponsive to initial immune checkpoint blockade therapy.Patients and Methods:We designed a single arm phase II study (NCT03179943) with a safety run-in to identify the recommended phase II dose of the combination therapy of guadecitabine and atezolizumab. Patients with recurrent/advanced UC who had previously progressed on ICI therapy with programmed cell death protein 1 or PD-L1 targeting agents were eligible. Preplanned correlative analysis was performed to characterize peripheral immune dynamics and global DNA methylation, transcriptome, and immune infiltration dynamics of patient tumors.Results:Safety run-in enrolled 6 patients and phase II enrolled 15 patients before the trial was closed for futility. No dose-limiting toxicity was observed. Four patients, with best response of stable disease (SD), exhibited extended tumor control (8–11 months) and survival (>14 months). Correlative analysis revealed lack of DNA demethylation in tumors after 2 cycles of treatment. Increased peripheral immune activation and immune infiltration in tumors after treatment correlated with progression-free survival and SD. Furthermore, high IL6 and IL8 levels in the patients’ plasma was associated with short survival.Conclusions:No RECIST responses were observed after combination therapy in this trial. Although we could not detect the anticipated tumor-intrinsic effects of guadecitabine, the addition of hypomethylating agent to ICI therapy induced immune activation in a few patients, which associated with longer patient survival.

Epithelial ovarian carcinomas are particularly deadly due to intratumoral heterogeneity, resistance to standard-of-care therapies, and poor response to alternative treatments such as immunotherapy. Targeting the ovarian carcinoma epigenome with DNA methyltransferase inhibitors (DNMTi) or histone deacetylase inhibitors (HDACi) increases immune signaling and recruits CD8+ T cells and natural killer cells to fight ovarian carcinoma in murine models. This increased immune activity is caused by increased transcription of repetitive elements (RE) that form double-stranded RNA (dsRNA) and trigger an IFN response. To understand which REs are affected by epigenetic therapies in ovarian carcinoma, we assessed the effect of DNMTi and HDACi on ovarian carcinoma cell lines and patient samples. Subfamily-level (TEtranscripts) and individual locus-level (Telescope) analysis of REs showed that DNMTi treatment upregulated more REs than HDACi treatment. Upregulated REs were predominantly LTR and SINE subfamilies, and SINEs exhibited the greatest loss of DNA methylation upon DNMTi treatment. Cell lines with TP53 mutations exhibited significantly fewer upregulated REs with epigenetic therapy than wild-type TP53 cell lines. This observation was validated using isogenic cell lines; the TP53-mutant cell line had significantly higher baseline expression of REs but upregulated fewer upon epigenetic treatment. In addition, p53 activation increased expression of REs in wild-type but not mutant cell lines. These data give a comprehensive, genome-wide picture of RE chromatin and transcription-related changes in ovarian carcinoma after epigenetic treatment and implicate p53 in RE transcriptional regulation.Significance:This study identifies the repetitive element targets of epigenetic therapies in ovarian carcinoma and indicates a role for p53 in this process.See interview with Katherine B. Chiappinelli, PhD, recipient of the 2022 Cancer Research Early Career Award: https://vimeo.com/720726570

Supplementary Figure from Epigenetic Therapies in Ovarian Cancer Alter Repetitive Element Expression in a TP53-Dependent Manner

Supplementary Data from Epigenetic Therapies in Ovarian Cancer Alter Repetitive Element Expression in a TP53-Dependent Manner

Supplementary Table from Epigenetic Therapies in Ovarian Cancer Alter Repetitive Element Expression in a TP53-Dependent Manner

COVID-19, the disease caused by SARS-CoV-2, has claimed approximately 5 million lives and 257 million cases reported globally. This virus and disease have significantly affected people worldwide, whether directly and/or indirectly, with a virulent pathogen that continues to evolve as we race to learn how to prevent, control, or cure COVID-19. The focus of this review is on the SARS-CoV-2 virus’ mechanism of infection and its proclivity at adapting and restructuring the intracellular environment to support viral replication. We highlight current knowledge and how scientific communities with expertize in viral, cellular, and clinical biology have contributed to increase our understanding of SARS-CoV-2, and how these findings may help explain the widely varied clinical observations of COVID-19 patients.

DNA methyltransferase inhibitors (DNMTis) reexpress hypermethylated genes in cancers and leukemias and also activate endogenous retroviruses (ERVs), leading to interferon (IFN) signaling, in a process known as viral mimicry. In the present study we show that in the subset of acute myeloid leukemias (AMLs) with mutations in

Epithelial ovarian carcinomas are particularly deadly due to intratumoral heterogeneity, resistance to standard-of-care therapies, and poor response to alternative treatments such as immunotherapy. Targeting the ovarian carcinoma epigenome with DNA methyltransferase inhibitors (DNMTi) or histone deacetylase inhibitors (HDACi) increases immune signaling and recruits CD8+ T cells and natural killer cells to fight ovarian carcinoma in murine models. This increased immune activity is caused by increased transcription of repetitive elements (RE) that form double-stranded RNA (dsRNA) and trigger an IFN response. To understand which REs are affected by epigenetic therapies in ovarian carcinoma, we assessed the effect of DNMTi and HDACi on ovarian carcinoma cell lines and patient samples. Subfamily-level (TEtranscripts) and individual locus-level (Telescope) analysis of REs showed that DNMTi treatment upregulated more REs than HDACi treatment. Upregulated REs were predominantly LTR and SINE subfamilies, and SINEs exhibited the greatest loss of DNA methylation upon DNMTi treatment. Cell lines with TP53 mutations exhibited significantly fewer upregulated REs with epigenetic therapy than wild-type TP53 cell lines. This observation was validated using isogenic cell lines; the TP53-mutant cell line had significantly higher baseline expression of REs but upregulated fewer upon epigenetic treatment. In addition, p53 activation increased expression of REs in wild-type but not mutant cell lines. These data give a comprehensive, genome-wide picture of RE chromatin and transcription-related changes in ovarian carcinoma after epigenetic treatment and implicate p53 in RE transcriptional regulation. Significance: This study identifies the repetitive element targets of epigenetic therapies in ovarian carcinoma and indicates a role for p53 in this process. See interview with Katherine B. Chiappinelli, PhD, recipient of the 2022 Cancer Research Early Career Award: https://vimeo.com/720726570

Lung cancer is the most common cause of cancer mortality worldwide and non-small cell lung cancer (NSCLC) accounts for approximately 85% of all lung cancers. Dysregulation and/or overexpression of MYC are widely implicated in NSCLC, which suggests that MYC may be a promising therapeutic target for the treatment of NSCLC. Recently, two direct MYC inhibiting agents with improved in vivo efficacy and tolerability, MYCi975 and Omomyc, have been developed. To define new drug strategies that could potentiate the therapeutic effects of MYC inhibitors, transcriptome datasets from MYCi975 and Omomyc studies were reanalyzed. These data revealed the induction of two class IIa histone deacetylases (HDACs), HDAC5 and HDAC9, upon MYC inhibition. Importantly, class IIa HDACs are involved in cancer proliferation, aggressiveness, and prognosis. In addition, novel agents that selectively inhibit class IIa HDACs have demonstrated promising anti-tumor efficacy; thus, suggesting potential therapeutic benefits from dual targeting of MYC and class IIa HDACs. We assessed the treatment efficacy of MYCi plus class IIa HDACi across 18 NSCLC cell lines, 10 of which demonstrated substantial reduction of cell viability upon combination treatment. Querying of driver mutation spectra associated with differential drug response in our cell line panel defined that EGFR mutant cell lines exhibited resistance, while STK11 or Ras mutant cell lines were sensitive to our drug paradigm. Gene set enrichment analysis comparing the transcriptomes of sensitive versus resistant cell lines revealed that MYC Targets, Oxidative Phosphorylation, and Reactive Oxygen Species (ROS) pathways were activated in combination treatment responsive cell lines. RNA sequencing on treated cell lines identified large-scale transcriptional shifts facilitated by combination treatment, including suppression of MYC, cell cycle, and mitochondrial pathways. Furthermore, G1/S arrest and elevated mitochondrial ROS levels in combination drug-treated cells were confirmed using flow cytometry. Concordant with the role of MYC as a key cell cycle regulator, MYC protein levels were decreased in the combination treatment group as compared to the vehicle or mono-treatment groups. Importantly, both MYC overexpression and ROS scavenger treatment partially rescued the reduction of cell viability by combination treatment, suggesting both MYC depletion and ROS elevation as contributors to therapeutic efficacy driven by combination treatment. Expanding these studies to in vivo models, we discern that combination MYC and class IIa HDAC inhibition significantly reduced tumor burden in a patient-derived xenograft model of human NSCLC. In summary, we define here a novel drug paradigm combining MYC and class IIa HDAC inhibitors, which potentiates anti-tumor efficacy in NSCLC via MYC depletion and oxidative stress. Citation Format: Jina Park, Ying-Yu Chen, Jennie Cao, Michelle Vaz, Ray-Whay C. Yen, Stephen B. Baylin, Michael J. Topper. Inhibition of class IIa HDACs potentiates MYC inhibitor-driven cytotoxicity by inducing MYC depletion and oxidative stress in non-small cell lung cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6256.

Cancer recurrence after surgery remains an unresolved clinical problem1–3. Myeloid cells derived from bone marrow contribute to the formation of the premetastatic microenvironment, which is required for disseminating tumour cells to engraft distant sites4–6. There are currently no effective interventions that prevent the formation of the premetastatic microenvironment6,7. Here we show that, after surgical removal of primary lung, breast and oesophageal cancers, low-dose adjuvant epigenetic therapy disrupts the premetastatic microenvironment and inhibits both the formation and growth of lung metastases through its selective effect on myeloid-derived suppressor cells (MDSCs). In mouse models of pulmonary metastases, MDSCs are key factors in the formation of the premetastatic microenvironment after resection of primary tumours. Adjuvant epigenetic therapy that uses low-dose DNA methyltransferase and histone deacetylase inhibitors, 5-azacytidine and entinostat, disrupts the premetastatic niche by inhibiting the trafficking of MDSCs through the downregulation of CCR2 and CXCR2, and by promoting MDSC differentiation into a more-interstitial macrophage-like phenotype. A decreased accumulation of MDSCs in the premetastatic lung produces longer periods of disease-free survival and increased overall survival, compared with chemotherapy. Our data demonstrate that, even after removal of the primary tumour, MDSCs contribute to the development of premetastatic niches and settlement of residual tumour cells. A combination of low-dose adjuvant epigenetic modifiers that disrupts this premetastatic microenvironment and inhibits metastases may permit an adjuvant approach to cancer therapy. In mouse models of pulmonary metastasis, adjuvant epigenetic therapy targeting myeloid-derived suppressor cells disrupts the premetastatic microenvironment after resection of primary tumours and inhibits the dissemination of residual tumour cells.

COVID-19, the disease caused by SARS-CoV-2, has claimed approximately 5 million lives and 257 million cases reported globally. This virus and disease have significantly affected people worldwide, whether directly and/or indirectly, with a virulent pathogen that continues to evolve as we race to learn how to prevent, control, or cure COVID-19. The focus of this review is on the SARS-CoV-2 virus' mechanism of infection and its proclivity at adapting and restructuring the intracellular environment to support viral replication. We highlight current knowledge and how scientific communities with expertize in viral, cellular, and clinical biology have contributed to increase our understanding of SARS-CoV-2, and how these findings may help explain the widely varied clinical observations of COVID-19 patients.

A minority of cancers have breast cancer gene (BRCA) mutations that confer sensitivity to poly (ADP-ribose) polymerase (PARP) inhibitors (PARPis), but the role for PARPis in BRCA-proficient cancers is not well established. This suggests the need for novel combination therapies to expand the use of these drugs. Recent reports that low doses of DNA methyltransferase inhibitors (DNMTis) plus PARPis enhance PARPi efficacy in BRCA-proficient AML subtypes, breast, and ovarian cancer open up the possibility that this strategy may apply to other sporadic cancers. We identify a key mechanistic aspect of this combination therapy in nonsmall cell lung cancer (NSCLC): that the DNMTi component creates a BRCAness phenotype through downregulating expression of key homologous recombination and nonhomologous end-joining (NHEJ) genes. Importantly, from a translational perspective, the above changes in DNA repair processes allow our combinatorial PARPi and DNMTi therapy to robustly sensitize NSCLC cells to ionizing radiation in vitro and in vivo. Our combinatorial approach introduces a biomarker strategy and a potential therapy paradigm for treating BRCA-proficient cancers like NSCLC.

The past decade has seen the emergence of immunotherapy as a prime approach to cancer treatment, revolutionizing the management of many types of cancer. Despite the promise of immunotherapy, most patients do not have a response or become resistant to treatment. Thus, identifying combinations that potentiate current immunotherapeutic approaches will be crucial. The combination of immune-checkpoint inhibition with epigenetic therapy is one such strategy that is being tested in clinical trials, encompassing a variety of cancer types. Studies have revealed key roles of epigenetic processes in regulating immune cell function and mediating antitumour immunity. These interactions make combined epigenetic therapy and immunotherapy an attractive approach to circumvent the limitations of immunotherapy alone. In this Review, we highlight the basic dynamic mechanisms underlying the synergy between immunotherapy and epigenetic therapies and detail current efforts to translate this knowledge into clinical benefit for patients. Despite promising responses in a minority of patients with cancer, considerable scope remains to improve the efficacy of both immune-checkpoint inhibitors and epigenetic drugs, with one potential strategy involving the combination of these two types of treatment. Here, the authors describe the mechanisms underlying the synergy between immune-checkpoint inhibitors and epigenetic drugs and discuss the ongoing clinical development of such combinations.

Lung cancer is the leading cause of cancer-related mortality among both men and women in the United States. Immune checkpoint blockade has emerged as a promising therapy for advanced non-small cell lung cancer (NSCLC); however, only a subset of patients responds to this treatment regimen. Therefore, combinatorial therapeutic strategies to enhance anti-tumor immunity and efficacy of immunotherapy are in urgent need. Our group and others have demonstrated the potential of MYC inhibition in NSCLC to render the tumor microenvironment (TME) more immune permissive by upregulating antigen presentation machinery and chemokines that recruit effector lymphocytes. We performed a dedicated reanalysis of published transcriptome data from two distinct cancer types, prostate and lung, which were treated with novel MYC inhibiting agents, MYCi975 and Omomyc, respectively. These data revealed augmentation of two class IIa histone deacetylases (HDACs), HDAC5 and HDAC9, upon MYC inhibition. In addition to the suggested interaction between MYC and Class IIa HDACs derived from our transcriptional analyses, class IIa HDACs have an established role in tumorigenesis, angiogenesis, and poor prognosis of cancer patients, thus implying that therapeutic benefits could be derived from dual inhibition of MYC and class IIa HDAC. Elucidation of the basal relationship between Class IIa HDACs and the immune microenvironment of NSCLC was derived through correlative analyses of TCGA Lung adenocarcinoma and squamous carcinoma RNA-seq data. These data revealed a conserved positive correlation across non-small cell lung cancer between class IIa HDAC RNA levels, Treg score, and Treg/CD8 ratio by immune deconvolution analysis. Evaluation of combinatorial treatment efficacy of MYCi plus Class IIa HDACi was undertaken using 19 NSCLC cell lines, which recapitulate the mutational and histological landscape of NSCLC. These data identified a genotype-driven drug synergy, wherein EGFR mutant cell lines presented as resistant, and Ras mutant cell lines presented as sensitive to our combination drug paradigm. In summary, we defined a positive association between Class IIa HDAC expression and Treg score in TCGA NSCLC samples, suggesting a possibility of immune-modulation via class IIa HDAC inhibition. Furthermore, we identified transcriptional augmentation of class IIa HDAC induced by MYC repression, which indicates a potential novel therapeutic opportunity. Finally, we determined that inhibition of class IIa HDACs potentiates MYC inhibitor-driven anti-tumor efficacy across a diverse set of NSCLC cell lines. Citation Format: Jina Park, Michelle Vaz, Ray-Whay C. Yen, Stephen B. Baylin, Michael J. Topper. Combination of MYC and class IIa HDAC inhibition potentiates anti-tumor efficacy in non-small cell lung cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3280.

DNA methyltransferase inhibitors (DNMTis), which transcriptionally activate hypermethylated genes in cancers and leukemias, also activate endogenous retroviruses (ERVs), leading to increased cytosolic double-stranded (ds) RNA and interferon (IFN) signaling, in a process termed viral mimicry. The tumor suppressor TP53 has been reported to cooperate with DNA methylation and IFN signaling to maintain transcriptional silencing of various repeat sequences, including ERVs. We now report that DNMTis, used to treat acute myeloid leukemia (AML) patients unfit for chemotherapy, robustly induce expression of ERVs and STING-dependent IFN/inflammasome signaling in AML with mutations in TP53(approximately 10%), a subset with poor prognosis. First, our studies of ERV transcripts (N=13) levels in TP53 mutant (KASUMI, KG1-1A, U937) and wild-type (WT; MOLM-14, OCI/AML2, and OCI/AML3) AML cell lines and primary cells (N=6 mutant, N=6 WT) show that, while TP53 mutant cells have low baseline ERV expression, DNMTi treatment significantly increases ERV expression, compared with WT TP53 cells (p Second, while TCGA data analysis showed that baseline STING transcript are low in TP53 mutant vs WT AML, phospho-STING (activated) is actually increased in TP53 mutant AML cells and DNMTi treatment further activates STING. Increased expression of downstream IFN/inflammasome genes in TP53 mutant AML treated with DNMTi, compared with results in WT cells, validates these results. Moreover, DNMTi combination with poly (ADP-ribose) polymerase inhibitors (PARPis), which we previously reported to activate STING in breast and ovarian cancer though increasing cytosolic dsDNA and dsRNA, further augments STING activation and IFN/inflammasome signaling (p Third, the IFN/inflammasome signaling response to DNMTI/PARPI signaling is directly linked with decreased expression of DNA ds break repair (DSBR) genes and activity, leading to homologous recombination defects (HRD). Fourth, the mechanism for both IFN/inflammasome signaling and HRD induction is dependent on STING, since both CRISPR/CAS KO of STING or treatment with the STING inhibitor H-151 can rescue these effects in TP53 mutant and WT AML cells. Our findings increase understanding of the therapy potential for combining DNMTi+PARPi treatment in AML and suggest use of this paradigm to treat mutant TP53 AML. These results also suggest that activating STING may be a key strategy for increasing IFN/inflammasome signaling in treatment of TP53 mutant AML and that immune responses may be further augmented with immune therapy in AML and other cancers. Citation Format: Aksinija A. Kogan, Michael J. Topper, Lora Stojanovic, Lena J. McLaughlin, Tammy J. Kingsbury, Maria R. Baer, Michael Kessler, Stephen B. Baylin, Feyruz V. Rassool. DNA methyltransferase inhibitors increase ERV reactivation and STING-dependent interferon/inflammasome signaling in TP53 mutant AML [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 6301.

Among the hallmarks of non-small cell lung cancer (NSCLC) is cancer immunoediting. Immunoediting results when cancer cells evade immune recognition via positive selection for cells that do not present immunogenic antigens recognized by CD8+ T cells. An epigenetic therapy-based approach has been developed in our lab to enhance expression of tumor antigens using combinatorial DNA methyltransferase inhibition (DNMTi) paired with histone deacetylase inhibition (HDACi). However, durable responses from the application of epigenetic therapy alone or in combination with other therapies have remained elusive in NSCLC. This may be because enhanced proliferation and infiltration of tumor-associated antigen specific CD8+ T cells are necessary to recognize epigenetically induced antigens to halt disease progression. In the current study, we identified epigenetic therapy inducible self-antigens that can potentially be used to activate and guide the differentiation of CD8+ T cells specific to NSCLC tumor antigens. The identification of these candidates was derived from analyses of paired RNAseq data from NSCLC patients treated with combination epigenetic therapy. From these analyses, differentially expressed transcripts selected from total transcriptome data were filtered to remove non-protein coding genes and genes with detectable expression in normal tissues as indicated by GTEx. HLA binding affinity (HLA-A*0201) of selected targets was defined by NetMHC 4.0 artificial neural network-based prediction to identify strong binding peptide candidates. The combined results of these data filtering facilitated the identification of 34 epigenetic therapy induced genes and associated peptides (9mers) with predicted high binding affinity for HLA-A*0201. The predicted peptides of target genes were selected for single peptide pulsing in allogenic dendritic cells to generate antigen specific CD8+ T cells for TCR sequencing (TCRseq). TCRseq libraries derived from peptide stimulation experiments revealed distinct V and J gene frequencies and emergence of antigen specific clonotypes, which suggest clonal expansion. To validate whether epigenetic therapy could induce target genes expression in an independent experimental model, in vitro human NSCLC cell lines were treated with DNMTi and HDACi to mimic the clinical drug paradigm and transcriptional augmentation was assessed by qRT-PCR. In this orthogonal system, we validated eight target genes that were induced by epigenetic therapy in vitro. Altogether, these data suggest that a conserved subset of genes, whose derived proteins are predicted to be presented in class I MHC and act as T cell epitopes, is induced by combination epigenetic treatment. Our studies provide a basis for the development of novel and personalized strategies to improve outcomes and quality of life for more patients with NSCLC. Citation Format: Julia An, Valsamo Anagnostou, Kristen A. Marrone, Victor E. Velculescu, Julie R. Brahmer, Stephen B. Baylin, Michael J. Topper. Identification of epigenetic therapy induced tumor antigens to promote proliferation and infiltration of antigen specific T cells in non-small cell lung cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3278.

DNA methyltransferase inhibitors (DNMTis) modulate genome-wide methylation patterns, previously linked by our group to downregulation of DNA double strand break repair (DSBR) that sensitizes non-small cell lung cancer (NSCLC) to poly(ADP-ribose) polymerase inhibitors (PARPis). DNMTi hypomethylation of endogenous retroviral (ERV) elements produces cytosolic aggregation of double-stranded RNA (dsRNA) that activates antiviral interferon (IFN) and inflammasome signaling. Accordingly, DNMTi treatment of NSCLC cell lines (A549, H460) increases expression of 1) multiple ERV transcripts; 2) dsRNA sensors RIG-I and MDA5; 3) downstream mitochondrial antiviral signaling protein (MAVS); 4) MAVS-activated antiviral kinases (TBK1, IKKα/β) and transcriptional regulators (IRF3/7, NFκB); and 5) IFNβ and IFN-stimulated genes (ISGs). A second mechanism of cellular antiviral signaling is STING (stimulator of interferon genes) activation triggered by cytosolic dsDNA. Following DNMTi treatment, we observe mitochondrial dysfunction including impairment of oxidative phosphorylation, reactive oxygen species generation, and reduced mitochondrial membrane potential. This dysfunction is associated with increased mitochondrial DNA (mtDNA) damage and accumulation of cytosolic mtDNA, leading to increased STING expression and IFN activation that can be abrogated by siSTING or IKK inhibition. Treatment with PARPi, which activates STING via cytosolic accumulation of damaged nuclear DNA, further enhances DNMTi-induced IFN signaling. We previously linked IFN activation to DSBR downregulation in breast and ovarian cancer, and now present TCGA analysis in NSCLC indicating a similar negative correlation, corroborated by reduced DSBR in NSCLC cell lines after IFNβ treatment. Computational interrogation indicates multiple DSBR promoters contain IFN-stimulated response elements (ISREs), including potential negative regulators, that may account for these findings. Notably, we find that precise patterns of immune activation may be TP53 dependent: NSCLC cell lines with missense mutations (H23, H441, H1115), as observed in ~30% patients, exhibit increased NFκB inflammasome signaling and decreased IFN activation compared to wildtype (A549, H460). TP53 mutation is associated with significantly reduced baseline STING expression, potentially affording a more robust DNMTi treatment response; accordingly, TP53-mutant NSCLC cells exhibit significantly greater sensitivity to DNMTi/PARPi. Our new data expands on our published work to further understanding of novel mechanisms of 1) inflammasome induction and 2) mitochondrial dysfunction through which DNMTis activate cellular antiviral signaling and downregulate DSBR to induce PARPi sensitivity in NSCLC. We also identify TP53 as a possible biomarker for future personalization of DNMTi therapy. Citation Format: Rachel Abbotts, Lora Stojanovic, Michael J. Topper, Brian M. Polster, Stephen B. Baylin, Feyruz V. Rassool. DNMT inhibitor induces NSCLC inflammasome signaling and mitochondrial dysfunction, producing to DSB repair defects and PARP inhibitor sensitivity [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 5593.

Epithelial ovarian carcinomas (OC) are particularly deadly due to intratumoral heterogeneity, resistance to standard-of-care therapies, and poor response to alternative treatments such as immunotherapy. Targeting the OC epigenome with DNA methyltransferase inhibitors (DNMTi) or histone deacetylase inhibitors (HDACi) increases immune signaling and recruits CD8+ T cells and NK cells to fight OC in murine models. This increased immune activity is caused by increased transcription of repetitive elements (RE) that form double-stranded RNA (dsRNA) and trigger an interferon response. To understand which REs are affected by epigenetic therapies in OC, we assessed the effect of DNMTi and HDACi on OC cell lines and patient samples. Subfamily-level (TEtranscripts) and individual locus-level (Telescope) analysis of REs showed that DNMTi treatment upregulated more REs than HDACi treatment. Upregulated REs were predominantly LTR and SINE subfamilies, and SINEs exhibited the greatest loss of DNA methylation upon DNMTi treatment. Cell lines with TP53 mutations exhibited significantly fewer upregulated REs with epigenetic therapy than wild type TP53 cell lines. This observation was validated using isogenic cell lines; the TP53 mutant cell line had significantly higher baseline expression of REs but upregulated fewer upon epigenetic treatment. In addition, p53 activation increased expression of REs in wild type but not mutant cell lines. These data give a comprehensive, genome-wide picture of RE chromatin and transcription-related changes in OC after epigenetic treatment and implicate p53 in RE transcriptional regulation.

Poly(ADP ribose) polymerase inhibitors (PARPi) have efficacy in triple negative breast (TNBC) and ovarian cancers (OCs) harboring BRCA mutations, generating homologous recombination deficiencies (HRDs). DNA methyltransferase inhibitors (DNMTi) increase PARP trapping and reprogram the DNA damage response to generate HRD, sensitizing BRCA-proficient cancers to PARPi. We now define the mechanisms through which HRD is induced in BRCA-proficient TNBC and OC. DNMTi in combination with PARPi up-regulate broad innate immune and inflammasome-like signaling events, driven in part by stimulator of interferon genes (STING), to unexpectedly directly generate HRD. This inverse relationship between inflammation and DNA repair is critical, not only for the induced phenotype, but also appears as a widespread occurrence in The Cancer Genome Atlas datasets and cancer subtypes. These discerned interactions between inflammation signaling and DNA repair mechanisms now elucidate how epigenetic therapy enhances PARPi efficacy in the setting of BRCA-proficient cancer. This paradigm will be tested in a phase I/II TNBC clinical trial.

Advanced age is strongly correlated with both increased cancer incidence and general immune decline. The immune tumor microenvironment (ITME) has been established as an important prognostic of both therapeutic efficacy and overall patient survival. Thus, age-related immune decline is an important consideration for the treatment of a large subset of cancer patients. Current studies of aging-related immune alterations are predominantly performed on non-cancerous tissue, requiring additional study into the effects of age on tumor immune infiltration. We leverage large scale transcriptional data sets from The Cancer Genome Atlas and the Genotype-Tissue Expression project to distinguish normal age-related immune alterations from age-related changes in tumor immune infiltration. We demonstrate that while there is overlap between the normal immune aging phenotype and that of the ITME, there are several changes in immune cell abundance that are specific to the ITME, particularly in T cell, NK cell, and Macrophage populations. These results suggest that aged immune cells are more susceptible to tumor suppression of cytotoxic immune cell infiltration and activity than normal tissues, which creates an unfavorable ITME in older patients in excess of normal immune decline with age and may inform the application of existing and emerging immunotherapies for this large population of patients. We additionally identify that age-related increases in tumor mutational burden are associated with decreased DNA methylation and increased expression of the immune checkpoint genesPDL1, CD80,andLAG3which may have implications for therapeutic application of immune checkpoint blockade in older patients.

SUMMARY Both tumors and aging alter the immune landscape of tissues. These interactions may play an important role in tumor progression among elderly patients and may suggest considerations for patient care. We leverage large-scale genomic and clinical databases to perform comprehensive comparative analysis of molecular and cellular markers of immune checkpoint blockade (ICB) response with patient age. These analyses demonstrate that aging is associated with increased tumor mutational burden, increased expression and decreased promoter methylation of immune checkpoint genes, and increased interferon gamma signaling in older patients in many cancer types studied, all of which are expected to promote ICB efficacy. Concurrently, we observe age-related alterations that might be expected to reduce ICB efficacy, such as decreases in T cell receptor diversity. Altogether, these changes suggest the capacity for robust ICB response in many older patients, which may warrant large-scale prospective study on ICB therapies among patients of advanced age., In brief Erbe et al. use multi-omics databases to evaluate biomarkers that are used to predict the response of patients with cancer to ICB in the context of aging. Erbe et al. find that biomarkers associated with ICB response are enriched in tumors from older patients relative to their younger counterparts., Graphical Abstract

Summary UHRF1 facilitates the establishment and maintenance of DNA methylation patterns in mammalian cells. The establishment domains are defined, including E3 ligase function, but the maintenance domains are poorly characterized. Here, we demonstrate that UHRF1 histone- and hemimethylated DNA binding functions, but not E3 ligase activity, maintain cancer-specific DNA methylation in human colorectal cancer (CRC) cells. Disrupting either chromatin reader activity reverses DNA hypermethylation, reactivates epigenetically silenced tumor suppressor genes (TSGs), and reduces CRC oncogenic properties. Moreover, an inverse correlation between high UHRF1 and low TSG expression tracks with CRC progression and reduced patient survival. Defining critical UHRF1 domain functions and its relationship with CRC prognosis suggests directions for, and value of, targeting this protein to develop therapeutic DNA demethylating agents.

Cancer recurrence after surgery remains an unresolved clinical problem

Poly (ADP-ribose) polymerase inhibitors (PARPi) are FDA approved in a subset of patients with ovarian cancer or metastatic breast cancers who harbor BRCA gene mutations. Although these mutations, which generate homologous recombination deficiencies (HRD), have been the main predictor to PARPi sensitivity, responses to therapy have not been durable and have failed for the majority of sporadic triple negative breast cancers (TNBC). We previously reported that DNA methyltransferase inhibitor (DNMTi) azacytidine (Aza) improves the efficacy of a new generation of PARPi, Talazoparib (Tal), through increased trapping of cytotoxic PARP-DNA complexes in both BRCA-mutant and -proficient TNBC. These trapped complexes lead to increased and persistent levels of lethal double strand breaks (DSBs), suggesting that DSB repair may also be impaired with this treatment. Indeed, Aza/Tal treatment in BRCA-proficient TNBC cell lines significantly downregulates expression of HR and Fanconi Anemia (FA) genes, notably FANCD2, and decreases HR activity, thus generating HRD. DNMTi have also been established to induce a viral mimicry response which upregulate type I interferon (IFN) signaling and production of inflammatory cytokines. In the present study, we elucidate the link between Aza/Tal facilitated HRD and induction of innate immune and inflammatory related genes, mediated through a STING dependent mechanism, which we term as a pathogen mimicry response (PMR). Gene set enrichment analysis of RNA-Seq data derived from mono- and combination-treated TNBC cell line MDA-MB-231, reveals enrichment of innate immune and cytosolic DNA sensing pathways with significant increases of TNFα/NF-κB and IFNαβ gene sets. Overlap between HRD and immune related signaling was evaluated using the STRING database, which reveals a significant interaction specifically between FA and TNFα/NF-κB and IFNαβ pathway genes. Tal driven cytosolic DNA as well as an Aza augmentation in STING protein expression, emerges as the key node in Aza/Tal induced innate immune signaling. Transient knockdown of STING is able to significantly rescue Aza- and combination-induced repression of FANCD2. Critically, in the presence of FANCD2 rescue facilitated by STING-specific inhibition, Aza-induced HRD was also reversed. These STING perturbation data suggest that Aza-induced HRD is dependent on presence of competent STING signaling. This inverse relationship was validated in both METABRIC TNBC dataset and TCGA data sets including lung adenocarcinoma and lung squamous cell carcinoma, colon adenocarcinoma, and AML, thus suggesting broad applicability of this observed transcriptional program independent of pharmacologic intervention. Induction of PMR to drive HRD suggests that DNMTi-PARPi therapy strategies can expand the therapeutic scope of PARPi to encompass treatment of BRCA-proficient cancers. Citation Format: Lena J. McLaughlin, Aksinija A. Kogan, Stephen B. Baylin, Michael J. Topper, Feyruz V. Rassool. Pharmacologic induction of innate immune signaling via STING directly drives homologous recombination deficiency [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 969.

In the letter by Haffner et al. (1), they report that seminoma cell-intrinsic DNA hypomethylation is associated with endogenous retroviral expression, an IFN response, and lymphocytic infiltration. Their data complement and support our recent therapeutic study in a mouse model of ovarian cancer (2) and support our observations that low doses of the DNA methyltransferase (DNMT) inhibitor azacytidine (AZA), in combination with the histone deacetylase inhibitor, givinostat, activate type 1 IFN signaling in ovarian (2) and lung (3) cancer cells to increase numbers and activation of immune cells in the tumor microenvironment and to increase sensitivity to the … [↵][1]5To whom correspondence may be addressed. Email: zahnoci{at}jhmi.edu or sbaylin{at}jhmi.edu. [1]: #xref-corresp-1-1

Ovarian cancer is the most lethal of all gynecological cancers, and there is an urgent unmet need to develop new therapies. Epithelial ovarian cancer (EOC) is characterized by an immune suppressive microenvironment, and response of ovarian cancers to immune therapies has thus far been disappointing. We now find, in a mouse model of EOC, that clinically relevant doses of DNA methyltransferase and histone deacetylase inhibitors (DNMTi and HDACi, respectively) reduce the immune suppressive microenvironment through type I IFN signaling and improve response to immune checkpoint therapy. These data indicate that the type I IFN response is required for effective in vivo antitumorigenic actions of the DNMTi 5-azacytidine (AZA). Through type I IFN signaling, AZA increases the numbers of CD45+ immune cells and the percentage of active CD8+ T and natural killer (NK) cells in the tumor microenvironment, while reducing tumor burden and extending survival. AZA also increases viral defense gene expression in both tumor and immune cells, and reduces the percentage of macrophages and myeloid-derived suppressor cells in the tumor microenvironment. The addition of an HDACi to AZA enhances the modulation of the immune microenvironment, specifically increasing T and NK cell activation and reducing macrophages over AZA treatment alone, while further increasing the survival of the mice. Finally, a triple combination of DNMTi/HDACi plus the immune checkpoint inhibitor α-PD-1 provides the best antitumor effect and longest overall survival, and may be an attractive candidate for future clinical trials in ovarian cancer.

// Frank P. Vendetti 1 , Michael Topper 1 , Peng Huang 1 , Irina Dobromilskaya 1 , Hariharan Easwaran 1 , John Wrangle 1 , Stephen B. Baylin 1 , J. T. Poirier 2 , Charles M. Rudin 2 1 The Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins University, Baltimore, MD 2 Memorial Sloan Kettering Cancer Center, NY 10065, New York Correspondence to: Charles M. Rudin, e-mail: rudinc@mskcc.org Keywords: epigenetic, azacitidine, entinostat, priming, chemosensitivity, non-small cell lung cancer (NSCLC) Received: July 25, 2014 Accepted: November 04, 2014 Published: November 25, 2014 ABSTRACT Recent clinical data in lung cancer suggests that epigenetically targeted therapy may selectively enhance chemotherapeutic sensitivity. There have been few if any studies rigorously evaluating this hypothesized priming effect. Here we describe a series of investigations testing whether epigenetic priming with azacitidine and entinostat increases sensitivity of NSCLC to cytotoxic agents. We noted no differences in chemosensitivity following treatment with epigenetic therapy in in vitro assays of viability and colony growth. Using cell line and patientderived xenograft (PDX) models, we also observed no change in responsiveness to cisplatin in vivo . In select models, we noted differential responses to irinotecan treatment in vivo . In vitro epigenetic therapy prior to tumor implantation abrogated response of H460 xenografts to irinotecan. Conversely, in vitro epigenetic therapy appeared to sensitize A549 xenografts (tumor growth inhibition 51%, vs. 22% in mock-pretreated control). In vivo epigenetic therapy enhanced the response of adenocarcinoma PDX to irinotecan. Taken together, these data do not support broadly applicable epigenetic priming in NSCLC. Priming effects may be context-specific, dependent on both tumor and host factors. Further preclinical study is necessary to determine whether, and in which contexts, priming with epigenetic therapy has potential to enhance chemotherapeutic efficacy in NSCLC patients.

// Huili Li 1,* , Katherine B. Chiappinelli 1,* , Angela A. Guzzetta 1,* , Hariharan Easwaran 1 , Ray-Whay Chiu Yen 1 , Rajita Vatapalli 1 , Michael J. Topper 1 , Jianjun Luo 1 , Roisin M. Connolly 1,2 , Nilofer S. Azad 1 , Vered Stearns 1,2 , Drew M. Pardoll 1 , Nancy Davidson 3 , Peter A. Jones 4 , Dennis J. Slamon 5 , Stephen B. Baylin 1 , Cynthia A. Zahnow 1 , Nita Ahuja 1,6 1 Department of Oncology, The Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins, Baltimore, MD, USA 2 Breast Cancer Program, The Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins, Baltimore, MD, USA 3 Department of Medicine, University of Pittsburgh Cancer Institute and UPMC CancerCenter, Pittsburgh, PA 4 Departments of Urology and Biochemistry and Molecular Biology, USC Norris Comprehensive Cancer Center, Keck School of Medicine, University of Southern California, Los Angeles, CA 5 The Jonsson Comprehensive Cancer Center, University of California-Los Angeles 6 Department of Surgery, School of Medicine, Johns Hopkins University, Baltimore, MD, USA * These authors contributed equally to the work Correspondence: Nita Ahuja, email: // Cynthia A. Zahnow, email: // Keywords : Epigenetics, immune, cancers, DNA methyltransferase inhibitor, interferon, methylation, antigen processing Received : February 4, 2014 Accepted : February 16, 2014 Published : February 16, 2014 Abstract Epigenetic therapy is emerging as a potential therapy for solid tumors. To investigate its mechanism of action, we performed integrative expression and methylation analysis of 63 cancer cell lines (breast, colorectal, and ovarian) after treatment with the DNA methyltransferase inhibitor 5-azacitidine (AZA). Gene Set Enrichment Analysis demonstrated significant enrichment for immunomodulatory pathways in all three cancers (14.4-31.3%) including interferon signaling, antigen processing and presentation, and cytokines/chemokines. Strong upregulation of cancer testis antigens was also observed. An AZA IMmune gene set (AIMs) derived from the union of these immunomodulatory pathway genes classified primary tumors from all three types, into “high” and “low” AIM gene expression subsets in tumor expression data from both TCGA and GEO. Samples from selected patient biopsies showed upregulation of AIM genes after treatment with epigenetic therapy. These results point to a broad immune stimulatory role for DNA demethylating drugs in multiple cancers.

Acute myeloid leukemia (AML) patients unfit for intensive chemotherapy are treated with DNA methyltransferase inhibitors (DNMTis). However, while many AML patients respond to DNMTis, responses are not durable. We previously reporteda novel treatment strategy for AML that combines DNMTis with poly (ADP-ribose) polymerase inhibitors (PARPis), drugs classically used to treat breast and ovarian cancer patients with BRCA mutations and homologous recombination defects (HRD) (Faraoni and Graziani, 2018). We found that combining low doses of the potent PARP-trapping PARPi talazoparib with DNMTis increases PARP trapping and cytotoxicityin vitroand increases therapeutic efficacy in vivo (Muvarak et al, 2016). We have nowidentified a novel mechanism through which DNMTis may sensitize BRCA-proficient AML cells to PARPis. This mechanism is tied to the capacity of these drugs to reprogram cancer signaling networks, including altering DNA repair pathways (Tsai et al, 2012). In studies in AML cell lines (N=6) and peripheral blood mononuclear cells (PBMCs) from AML patients (N=4), we now show that treatment with the DNMTi decitabine (DAC) at a low concentration (10nM) can directly induce HRD, by significantly (p How do DNMTis downregulate HR gene expression? We show for the first time that immune signaling is linked to induction of HRD. We have previously shown that DNMTis activate innate immune pathways involving interferon (IFN) □ and tumor necrosis factor (TNF) □, a phenomenon known as viral mimicry (Chiappinelli et al, 2015).First, The Cancer Genome Atlas (TCGA) AML data sets show an inverse correlation between type 1 interferon (IFN)/pro-inflammatory response and HR-related genes. Second, we verified in BRCA-proficient AML cell lines (N=6) that immune signaling by exogenous TNF□□or IFN□□treatment decreases HR gene expression and activity by more than two-fold for the majority of genes tested (p Importantly, we identified a common immune signaling pathway induced by both DNMTis and PARPis. PARPis have also been shown to activate type 1 IFN pathways via induction of cytoplasmic double-stranded DNA sensing through signaling of the cyclic GMP-AMP Synthase - Stimulator of Interferon Genes(cGAS-STING) pathway. We now find that inhibition of STING with inhibitor H-151 (500nM) not only rescues immune signaling induced by PARPi, but also by DAC and PARPi combination treatment. Moreover, the STING inhibitor also rescues DAC- and/or PARPi-induced HRD. These data suggest that STING may be a central signaling hub linked to HRD and also suggest ways in which epigenetic therapy, inhibitors of DNA damage response proteins, and targeted immune therapy can synergize to treat AML. Disclosures Baer: Takeda: Research Funding; Incyte: Research Funding; Kite: Research Funding; Forma: Research Funding; AI Therapeutics: Research Funding; Abbvie: Research Funding; Astellas: Research Funding.

Poly (ADP-ribose) polymerase inhibitors (PARPis) are effective in a subset of triple negative breast cancers (TNBC) with BRCA gene mutations, which generates homologous recombination deficiencies (HRD), through synthetic lethality. However, PARPis fail for the majority of sporadic TNBC with intact BRCA1/2 genes and other BRCA-proficient cancers, including acute myeloid leukemia (AML). PARPi, Talazoparib (TAL), has potent PARP trapping ability, in both BRCA mutant and proficient TNBCs and AML. We reported that a combination of TAL with low doses of DNA methyl transferase inhibitor (DNMTi) azacytidine (AZA) or decitabine (DAC), increased PARP trapping even further, leading to increased levels of cytotoxic double strand breaks in vitro and decreased tumor burden in vivo. Low doses of DNMTis have been shown previously to reprogram genome wide cancer signaling, including immune and DNA damage/repair pathways. We now tie these two signaling pathways together for events through which DNMTis plus TAL drive HRD. BRCA proficient TNBC (N=2) and AML (cell lines (N=2) and primary cells (N=4)) treated with low doses of DNMTis (DAC 10nM and AZA 250-500nM), significantly downregulate expression of genes in HR and Fanconi Anemia (FA) pathways, decreasing HR activity, thus generating HRD. HR is further decreased when DNMTis are combined with TAL. We now link DNMTi/TAL induced HRD to a coupled interferon (IFN) response in both TNBC and AML. In these systems, we elucidate DNMTi/TAL potentiated cGAS-Sting and type 1 IFN signaling, culminating in the induction of IFN responsive genes and inflammatory cytokine production. Importantly, in DNMTi/TAL treated cells, increased expression of IFN signaling genes is strongly linked to downregulation of FA/HR genes through protein interaction network mapping. This inverse association between IFN and HR related genes, was further validated in TCGA data sets for AML and invasive BC, suggesting broad applicability of this observed transcriptional program. The acquisition of HRD from IFN signaling specifically, is verified by the observation of reduced HR gene expression and activity in the presence of exogenous double stranded RNA (Poly(I:C)) or IFNβ treatment in both TNBC and AML cell lines. Finally, knockdown of a key connectivity node between IFN and HR related genes, interferon sensitive gene 15 (ISG15), abrogates downregulation of FA gene expression when treated with IFNβ, suggesting mediation of HRD through ISG15. In conclusion, we have identified a novel mechanism through which IFN-sensitive genes can create an HRD phenotype in BRCA proficient TNBC and AML, suggesting that innate immunity and inflammatory processes may be intrinsically linked to DNA repair in cancer. These studies suggest that immune therapies and/or epigenetic therapy are likely to enhance responses to PARPis in BRCA proficient cancers. Citation Format: Lena J. McLaughlin, Aksinija A. Kogan, Eun Yong Choi, Rena S. Lapidus, Ying Zou, Huili Li, Stephen B. Baylin, Michael J. Topper, Feyruz V. Rassool. DNMT and PARP inhibitor combination therapy induces an interferon-driven homologous recombination defect in triple-negative breast cancers and acute myeloid leukemia [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 4473.

Reversing the DNA methylation abnormalities by targeting the maintenance DNA methylation machinery represents a sought-after therapy paradigm in both liquid and solid tumors. UHRF1, a multi-domain protein with both chromatin reader and writer functions, is essential for targeting DNA methyltransferase 1 (DNMT1) to replicating DNA to maintain DNA methylation in both normal and cancer cells. Dysregulation of the DNMT1-UHRF1 axis is being increasingly linked to malignant transformation and progression across cancer types. Our recent study shows that UHRF1 depletion, alone or in combination with low doses of a DNMT inhibitor, effectively induces DNA demethylation and tumor suppressor genes (TSGs) reactivation. These findings collectively suggest UHRF1 represents a promising target for developing next-generation DNA demethylation agents for cancer therapy. Understanding the collective contribution of UHRF1’s domains for maintenance methylation is essential for the major translational goal of blocking maintenance of abnormal DNA methylation in established cancers and throughout cancer initiation and progression. While the UHRF1 domains responsible for de novo or re-methylation have been identified, the domain requirements specifically for maintaining normal and cancer-specific DNA methylation are poorly characterized. Herein, by developing a carefully timed genetic complementation assay, we systematically interrogate the roles for each major domain of UHRF1 for maintaining genome-wide DNA methylation in human colorectal cancer (CRC) cells. Distinct from the domain required for establishing methylation, we find that UHRF1 histone-binding and hemimethylated DNA reader domains, but not E3 ligase activity, are essential for maintaining cancer-specific DNA methylation in both HCT116 and RKO cells. Disrupting either one of the essential domains phenocopies UHRF1 depletion for global DNA demethylation and reactivation of epigenetically silenced TSGs. Supporting the essential roles of abnormal DNA methylation in sustaining the key oncogenic properties of CRC cells, we further show genetic perturbation of either histone- or hemimethylated DNA-binding activities of UHRF1 dramatically impairs CRC proliferation, invasion, and metastasis in vitro and in vivo. Moreover, for eight UHRF1 chromatin-reader domain regulated TSGs, we reveal a strong negative correlation between high UHRF1 expression, promoter hypermethylation, and their low expression with disease progression and overall survival in CRC patients in both TCGA and two independent CRC cohorts (n=363 and 390, respectively). Taken together, our data identify important differences from domains dominant for de novo DNA methylation, and provide important implications for the oncogenic functions of UHRF1 in CRC, and for credentialing UHRF1 as a desirable target for cancer drug development and means to personalize this. Citation Format: Xiangqian Kong, Jie Chen, Wenbing Xie, Stephen M. Brown, Yi Cai, Kaichun Wu, Daiming Fan, Yongzhan Nie, Yong Tao, Ray-Whay Chiu Yen, Hariharan Easwaran, Michael J. Topper, Scott B. Rothbart, Limin Xia, Stephen B. Baylin. Defining UHRF1 domains that support maintenance of human colon cancer DNA methylation and tumorigenicity [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 947.

Epigenetic silencing and inappropriate activation of gene expression are frequent events during the initiation and progression of cancer. These events involve a complex interplay between the hypermethylation of CpG dinucleotides within gene promoter and enhancer regions, the recruitment of transcriptional corepressors and the deacetylation and/or methylation of histone tails. These epigenetic regulators act in concert to block transcription or interfere with the maintenance of chromatin boundary regions. However, DNA/histone methylation and histone acetylation states are reversible, enzyme-mediated processes and as such, have emerged as promising targets for cancer therapy. This review will focus on the potential benefits and synergistic/additive effects of combining DNA-demethylating agents and histone deacetylase inhibitors or lysine-specific demethylase inhibitors together in epigenetic therapy for solid tumors and will highlight what is known regarding the mechanisms of action that contribute to the antitumor response.

Acute myeloid leukemia (AML) is a genetically heterogeneous disease where malignant clonal proliferation of immature myeloid cells in the bone marrow leads to disruption of normal hematopoiesis and bone marrow failure. Most treatment improvements have consisted of limited chemotherapeutic interventions, and morbidity and mortality remain unacceptably high. While patients unfit for intensive chemotherapy have the options of epigenetic treatments with DNA methyltransferase inhibitors (DNMTis), and the preclinical research underpinning these treatments is robust and promising, clinical response rates have been poor. Therefore, we have derived a unique treatment strategy combining poly-ADP ribose polymerase inhibitors (PARPis) with DNMTis, and we have previously demonstrated efficacy of this combination in AML in both in vitroand in vivomodels. This combination increases the amount and retention time of PARP1 at laser-induced DNA damage sites, increases DNA DSBs and tumor cytotoxicity, blunts cell self-renewal, and leads to strong anti-tumor responses. These results form the basis for our ongoing Phase I/II clinical trial of this combination therapy in patients with relapsed/refractory AML. To identify molecular pathways underpinning this combination, genome-wide expression microarray analysis was performed on RNA extracted from multiple BRCA-intact sporadic AML cell lines treated with single agents or drug combination. Interestingly, combination drug treatment, more than either single treatment alone, up regulated genes in immune response pathways, including interferons, natural killer cell-mediated cytotoxicity and Toll-like receptor signaling pathway genes. In both AML cell lines (N=10) and primary samples (N=8), we used qPCR to validate these expression increases, with particular focus on interferon type 1-inducible genes, including IFI6, IFI27, IFI30, IRF7, ISG15, and OASL. These interferon-inducible genes were similarly increased in selected AML clinical trial samples post combination treatment. Interferon stimulation studies showed that treatment of multiple cell lines with IFN-β similarly up regulates our genes of interest, and suggests that the immune system plays a pivotal role in mediating the effects of our combination treatment. To functionally validate this immune involvement in vivo, we use an immune competent mouse model that spontaneously develops AML. The bone marrow cells collected from leukemic FLT3/ITD;NHD13 mice are transplanted into sublethally irradiated syngeneic recipients where they undergo clonal leukemic expansion and expression of specific surface markers (CD45.1 vs CD45.2) allow for the tracking of both host and transplanted blood cells. After validating that our combination treatment increases survival and reduces tumor burden in this in vivo model, we isolated mononuclear cells from spleens and livers and found that mice in the combination therapy group had increased T cell populations with increased PD1, CD28 and 4-1BB expression. Tal single agent and combination therapy treated mice also had decreased myeloid-derived suppressor cells and increased antigen presenting cells, specifically dendritic cells, monocytes and macrophages. Finally, upon ex vivo stimulation, T cells from mice receiving combination therapy produced significantly more IFN-γ and GM-CSF than mice from other treatment groups. These results indicate that our combination therapy results in immune activation, and suggest the potential to target the immune system in order to induce anti-tumor effects, enhance efficacy of our combination treatment and improve clinical outcomes in AML. Disclosures Lapidus: KinaRx, LLC: Other: Founder and Scientific Advisor.

Non-small cell lung cancer (NSCLC) is the leading cause of cancer-related death in the US. Poly (ADP-ribose) polymerase inhibitors (PARPi) show efficacy as radiosensitizers in NSCLC, but arguably have gained greater importance in cancer therapeutics by exhibiting synthetic lethality (SL) in tumors with defects in the homologous recombination (HR) pathway of double strand break repair (DSBR). Mechanistically, PARPi cytotoxicity is partially mediated through trapping of PARP1 at sites of DNA damage, with next generation PARPis such as talazoparib (Tal) being potent PARP trappers. Our group has previously demonstrated that combining Tal with a DNA methyltransferase inhibitor (DNMTi) enhances PARPi cytotoxicity in acute myeloid leukaemia and breast cancer models. DNMTis are cytosine analogs that become incorporated into replicating DNA, where they covalently bind their target enzyme DNMT1. When combined with PARPi, DNMTis enhance PARP trapping at damage sites, which collapse into cytotoxic double strand breaks (DSB) when encountered by a replication fork. In the current study, we demonstrate synergistic cytotoxicity of Tal in combination with the DNMTi 5-azacytidine (Aza) in NSCLC cell lines by combination index analyses and colony forming assays. Further potentiation of Tal+Aza cytotoxicity is observed following induction of DNA damage via IR. These results were substantiated in an A549 xenograft model (n=8 per group) where Tal+Aza+IR significantly reduced tumor volume and increased survival compared to vehicle (p Citation Format: Rachel Abbotts, Michael Topper, Daniel Fontaine, Christopher Biondi, Eun Yong Choi, Rena Lapidus, Stephen Baylin, Feyruz Rassool. DNA methyltransferase inhibitors sensitize NSCLC cells to PARP inhibitors by induction of a double strand break repair defect [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2823.

The Predictive Safety Testing Consortium's first regulatory submission to qualify kidney safety biomarkers revealed two deficiencies. To address the need for biomarkers that monitor recovery from agent-induced renal damage, we scored changes in the levels of urinary biomarkers in rats during recovery from renal injury induced by exposure to carbapenem A or gentamicin. All biomarkers responded to histologic tubular toxicities to varied degrees and with different kinetics. After a recovery period, all biomarkers returned to levels approaching those observed in uninjured animals. We next addressed the need for a serum biomarker that reflects general kidney function regardless of the exact site of renal injury. Our assay for serum cystatin C is more sensitive and specific than serum creatinine (SCr) or blood urea nitrogen (BUN) in monitoring generalized renal function after exposure of rats to eight nephrotoxicants and two hepatotoxicants. This sensitive serum biomarker will enable testing of renal function in animal studies that do not involve urine collection.

Combining DNA-demethylating agents (DNA methyltransferase inhibitors [DNMTis]) with histone deacetylase inhibitors (HDACis) holds promise for enhancing cancer immune therapy. Herein, pharmacologic and isoform specificity of HDACis are investigated to guide their addition to a DNMTi, thus devising a new, low-dose, sequential regimen that imparts a robust anti-tumor effect for non-small-cell lung cancer (NSCLC). Using in-vitro-treated NSCLC cell lines, we elucidate an interferon α/β-based transcriptional program with accompanying upregulation of antigen presentation machinery, mediated in part through double-stranded RNA (dsRNA) induction. This is accompanied by suppression of MYC signaling and an increase in the T cell chemoattractant CCL5. Use of this combination treatment schema in mouse models of NSCLC reverses tumor immune evasion and modulates T cell exhaustion state towards memory and effector T cell phenotypes. Key correlative science metrics emerge for an upcoming clinical trial, testing enhancement of immune checkpoint therapy for NSCLC.

Combination epigenetic treatment as a therapeutic approach holds much promise. However, to unlock the true potential of these combinatorial paradigms, further optimization is required. We have elucidated in our current study, a treatment schedule combining Azacitidine with Histone Deacetylase Inhibition (HDACi) which considers both schedule and isoform specificity. We have deployed a sequential schedule with HDACi administered post Azacitidine in a chronic low dose manner. This schedule takes advantage of two key parameters altered by Azacitidine: dsRNA induced immune signature and MYC depletion. In our system, HDACis amplify an existing immune signature and the MYC depleted environment acts as a potent sensitizer. HDACi induced augmentation of immune gene transcription seems driven predominantly through the inhibition of HDAC1/2 and HDAC6 isoforms, with broad spectrum HDACi inhibitors demonstrating the greatest potency. While the combination treatment induced perturbation of proliferation is driven by inhibition of HDAC1/2/3 isoforms. Applying this concept to a genetically engineered mouse model of NSCLC we observe a potent anti-tumor response as evidenced by a reduction in tumor burden, progression and proliferation. These phenotypic parameters are correlated with modification of both immune and proliferative gene signatures as well as alteration of key immune populations in the tumor microenvironment. We propose that this combinatorial alteration of both immune and proliferative parameters holds the promise to be a more robust treatment for NSCLC. Note: This abstract was not presented at the meeting. Citation Format: Michael Topper, Michelle Vaz, Katherine Chiappinelli, Christina DeStefano Shields, Alyssa Wenzel, Cynthia Zahnow, Pam Strissel, Reiner Strick, Stephen Baylin. Sequential azacitidine and histone deacetylase inhibition induces a potent antitumor response in Kras G12D mouse model of NSCLC [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr LB-098. doi:10.1158/1538-7445.AM2017-LB-098