Wa Zhang

Abstract A hallmark of human cancer is global DNA hypomethylation (GDHO), but the mechanisms accounting for this defect and its pathological consequences have not been defined in human epithelial ovarian cancer (EOC). In EOC, GDHO was associated with advanced disease and reduced overall and disease-free survival. GDHO(+) EOC was enriched for a proliferative gene expression signature, including CCNE1 and FOXM1 overexpression. DNA hypomethylation preferentially occurred within genomic blocks (hypomethylated blocks) overlapping late-replicating, lamina-associated domains, PRC2 binding, and H3K27me3. Increased proliferation coupled with hypomethylated block formation at late replicating regions suggested passive hypomethylation, which was further supported by the observation that cytosine DNA methyltransferases ( DNMTs) and UHRF1 showed significantly reduced expression in GDHO(+) EOC, after normalization to proliferation markers. Importantly, GDHO(+) EOC showed elevated chromosomal instability (CIN), and copy number alterations (CNA) were enriched at hypomethylated blocks. Together, these findings implicate a passive demethylation mechanism for GDHO that promotes genomic instability and poor prognosis in EOC.

The cancer-testis/cancer-germline antigen NY-ESO-1 is a vaccine target in epithelial ovarian cancer (EOC), but its limited expression is a barrier to vaccine efficacy. As NY-ESO-1 is regulated by DNA methylation, we hypothesized that DNA methyltransferase (DNMT) inhibitors may augment NY-ESO-1 vaccine therapy. In agreement, global DNA hypomethylation in EOC was associated with the presence of circulating antibodies to NY-ESO-1. Pre-clinical studies using EOC cell lines showed that decitabine treatment enhanced both NY-ESO-1 expression and NY-ESO-1-specific CTL-mediated responses. Based on these observations, we performed a phase I dose-escalation trial of decitabine, as an addition to NY-ESO-1 vaccine and doxorubicin liposome (doxorubicin) chemotherapy, in 12 patients with relapsed EOC. The regimen was safe, with limited and clinically manageable toxicities. Both global and promoter-specific DNA hypomethylation occurred in blood and circulating DNAs, the latter of which may reflect tumor cell responses. Increased NY-ESO-1 serum antibodies and T cell responses were observed in the majority of patients, and antibody spreading to additional tumor antigens was also observed. Finally, disease stabilization or partial clinical response occurred in 6/10 evaluable patients. Based on these encouraging results, evaluation of similar combinatorial chemo-immunotherapy regimens in EOC and other tumor types is warranted.

A hallmark of human cancer is global DNA hypomethylation (GDHO), but the mechanisms accounting for this defect and its pathological consequences have not been investigated in human epithelial ovarian cancer (EOC). In EOC, GDHO was associated with advanced disease and reduced overall and disease-free survival. GDHO (+) EOC tumors displayed a proliferative gene expression signature, including FOXM1 and CCNE1 overexpression. Furthermore, DNA hypomethylation in these tumors was enriched within genomic blocks (hypomethylated blocks) that overlapped late-replicating regions, lamina-associated domains, PRC2 binding sites, and the H3K27me3 histone mark. Increased proliferation coupled with hypomethylated blocks at late-replicating regions suggests a passive hypomethylation mechanism. This hypothesis was further supported by our observation that cytosine DNA methyltransferases (DNMTs) and UHRF1 showed significantly reduced expression in GDHO (+) EOC after normalization to canonical proliferation markers, including MKI67. Finally, GDHO (+) EOC tumors had elevated chromosomal instability (CIN), and copy number alterations (CNA) were enriched at the DNA hypomethylated blocks. Together, these findings implicate a passive DNA demethylation mechanism in ovarian cancer that is associated with genomic instability and poor prognosis.

// Wa Zhang 1, 10 , Carter J. Barger 1 , Kevin H. Eng 4 , David Klinkebiel 2 , Petra A. Link 3 , Angela Omilian 5 , Wiam Bshara 5 , Kunle Odunsi 6, 7, 8 , Adam R. Karpf 1, 9 1 Eppley Institute for Cancer Research, University of Nebraska Medical Center, Omaha, NE, USA 2 Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, NE, USA 3 Department of Pharmacology, Roswell Park Cancer Institute, Buffalo, NY, USA 4 Department of Biostatistics and Bioinformatics, Roswell Park Cancer Institute, Buffalo, NY, USA 5 Department of Pathology, Roswell Park Cancer Institute, Buffalo, NY, USA 6 Department of Gynecologic Oncology, Roswell Park Cancer Institute, Buffalo, NY, USA 7 Department of Immunology, Roswell Park Cancer Institute, Buffalo, NY, USA 8 Center for Immunotherapy, Roswell Park Cancer Institute, Buffalo, NY, USA 9 Fred and Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, NE, USA 10 Current address: Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore, MD, USA Correspondence to: Adam R. Karpf, email: adam.karpf@unmc.edu Keywords: PRAME, cancer testis antigens, epithelial ovarian cancer, high grade serous cancer, DNA methylation Received: May 02, 2016      Accepted: May 29, 2016      Published: June 13, 2016 ABSTRACT PRAME is a cancer-testis antigen (CTA) and potential immuno-therapeutic target, but has not been well-studied in epithelial ovarian cancer (EOC) or its high grade serous (HGSC) subtype. Compared to normal ovary, PRAME expression was significantly increased most EOC, regardless of stage and grade. Interestingly, PRAME mRNA expression was associated with improved survival in the HGSC subtype. The PRAME locus was a frequent target for copy number alterations (CNA) in HGSC but most changes were heterozygous losses, indicating that elevated PRAME expression is not typically due to CNA. In contrast, PRAME promoter DNA hypomethylation was very common in EOC and HGSC and correlated with increased PRAME expression. PRAME expression and promoter hypomethylation both correlated with LINE-1 hypomethylation, a biomarker of global DNA hypomethylation. Pharmacologic or genetic disruption of DNA methyltransferase (DNMT) enzymes activated PRAME expression in EOC cells. Immunohistochemistry (IHC) of PRAME in EOC revealed frequent, but low level, protein expression, and expression was confined to epithelial cells and localized to the cytoplasm. Cytoplasmic PRAME expression was positively associated with PRAME mRNA expression and negatively associated with promoter methylation, but the latter correlation was not statistically significant. PRAME protein expression did not correlate with EOC clinicopathology or survival. In summary, PRAME is frequently expressed in EOC at the mRNA and protein levels, and DNA methylation is a key mechanism regulating its expression. These data support PRAME as an immunotherapy target in EOC, and suggest treatment with DNMT inhibitors as a means to augment PRAME immunotherapy.

// Carter J. Barger 1 , Wa Zhang 1 , Joanna Hillman 2 , Aimee B. Stablewski 2 , Michael J. Higgins 2 , Barbara C. Vanderhyden 3 , Kunle Odunsi 4, 5, 6 , Adam R. Karpf 1 1 Eppley Institute and Fred & Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, NE, 68198, USA 2 Department of Molecular and Cellular Biology, Roswell Park Cancer Institute, Buffalo, NY, 14263, USA 3 Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, Ontario, K1H 8M5, Canada 4 Department of Immunology, Roswell Park Cancer Institute, Buffalo, NY, 14263, USA 5 Department of Gynecologic Oncology, Roswell Park Cancer Institute, Buffalo, NY, 14263, USA 6 Center for Immunotherapy, Roswell Park Cancer Institute, Buffalo, NY, 14263, USA Correspondence to: Adam R. Karpf, e-mail: adam.karpf@unmc.edu Keywords: FOXM1, epithelial ovarian cancer, p53, Rb, E2F1 Received: March 17, 2015      Accepted: July 06, 2015      Published: July 16, 2015 ABSTRACT The FOXM1 transcription factor network is frequently activated in high-grade serous ovarian cancer (HGSOC), the most common and lethal subtype of epithelial ovarian cancer (EOC). We used primary human EOC tissues, HGSOC cell lines, mouse and human ovarian surface epithelial (OSE) cells, and a murine transgenic ovarian cancer model to investigate genetic determinants of FOXM1 overexpression in EOC, and to begin to define its functional contribution to disease pathology. The Cancer Genome Atlas (TCGA) data indicated that the FOXM1 locus is amplified in ~12% of HGSOC, greater than any other tumor type examined, and that FOXM1 amplification correlates with increased expression and poor survival. In an independent set of primary EOC tissues, FOXM1 expression correlated with advanced stage and grade. Of the three known FOXM1 isoforms, FOXM1c showed highest expression in EOC. In murine OSE cells, combined knockout of Rb1 and Trp53 synergistically induced FOXM1. Consistently, human OSE cells immortalized with SV40 Large T antigen (IOSE-SV) had significantly higher FOXM1 expression than OSE immortalized with hTERT (IOSE-T). FOXM1 was overexpressed in murine ovarian tumors driven by combined Rb1 / Trp53 disruption. FOXM1 induction in IOSE-SV cells was partially dependent on E2F1, and FOXM1 expression correlated with E2F1 expression in human EOC tissues. Finally, FOXM1 functionally contributed to cell cycle progression and relevant target gene expression in human OSE and HGSOC cell models. In summary, gene amplification, p53 and Rb disruption, and E2F1 activation drive FOXM1 expression in EOC, and FOXM1 promotes cell cycle progression in EOC cell models.