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Targeting androgen receptor (AR) by pharmacologic intervention is one of the effective approaches for treatment of malignant prostate cancers. Histone deacetylase (HDAC) alters the epigenetic status of tumor-associated genes, including those for miRNAs (miRNA), and affects the behavior of cancers. Here, we examined the molecular effects of a HDAC inhibitor, OBP-801, on AR expression and tumor cell growth in prostate cancers. Treatment with OBP-801 efficiently suppressed cell growth of three prostate cancer lines (22Rv1, VCaP, and LNCaP), together with AR downregulation, regardless of their hormone sensitivity. Intriguingly, this effect by OBP-801 was not due to decreased transcriptional activity of the AR gene, but due to posttranscriptional regulation, namely by miRNA-mediated suppression. Among the upregulated miRNAs after OBP-801 treatment in the three prostate cancer cell lines, miR-320a, whose expression was significantly correlated with prognosis of prostate cancers (P = 0.0185), was the most closely associated with AR expression. An miR-320a mimic suppressed AR protein expression together with growth suppression, while anti-miR-320a oligonucleotide significantly abrogated the growth suppression by OBP-801 treatment. FISH analysis revealed that miR-320a was highly expressed in human normal prostate luminal cells, but was rarely expressed in prostate cancer cells. In an AR-dependent prostate tumorigenic rat model, OBP-801 treatment profoundly increased miR-320a expression and repressed prostate tumorigenesis. Our data demonstrated that OBP-801 effectively suppressed AR activity via epigenetic upregulation of miR-320a, which resulted in tumor cell growth suppression of prostate cancers. OBP-801 may be a potent AR-targeting therapeutic reagent in AR-positive prostate cancer regardless of androgen dependency. Cancer Res; 76(14); 4192–204. ©2016 AACR.

Targeting androgen receptor (AR) by pharmacological intervention is one of the effective approaches for treatment of malignant prostate cancers. Histone deacetylase (HDAC) alters epigenetic status of tumor-associated genes, including microRNAs (miRNAs), and affects the behavior of cancers. Here we examined molecular effects of a HDAC inhibitor, OBP-801, on AR expression and tumor cell growth in prostate cancers. Treatment of OBP-801 efficiently suppressed cell growth of three prostate cancer lines (22Rv1, VCaP, and LNCaP), together with AR downregulation, regardless of their hormone sensitivity. Intriguingly, this effect by OBP-801 is not due to downregulation of transcriptional activity of the AR gene, but due to post-transcriptional regulation, namely miRNA-mediated suppression. Among the upregulated miRNAs after OBP-801 treatment in three prostate cancer cell lines, miR-320a, of which expression was significantly correlated with prognosis of prostate cancers (P = 0.0185), was the most closely associated with AR expression. miR-320a mimic suppressed AR protein expression together with growth suppression, while anti-miR320a significantly abrogated the growth suppression by OBP-801 treatment. Fluorescent in situ hybridization analysis revealed that miR-320a was highly expressed in human normal prostate luminal cells but rarely expressed in prostate cancer cells. In AR-dependent prostate tumorigenic rat model, OBP-801 treatment profoundly increased the miR-320 expression and repressed prostate tumorigenesis. Our data demonstrated that OBP-801 effectively suppressed AR activity via epigenetic upregulation of miR-320a, which resulted in tumor cell growth suppression of prostate cancers. OBP-801 may be a potent drug as an AR targeting therapy in AR positive prostate cancer regardless of androgen dependency. Citation Format: Shinya Sato, Keisuke Katsushima, Keiko Shinjo, Satoru Takahashi, Yutaka Kondo. Inhibition of histone deacetylase induces miR-320-mediated androgen receptor suppression in prostate cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1110.

Pancreatic cancer is highly lethal malignancy despite the recent clinical advancement. Since pancreatic cancer is often difficult to diagnose, there is an urgent need to develop novel biomarkers for early detection with blood tests. Epigenetic alterations have emerged as a common hallmark of many types of human cancers as well as pancreatic cancer. Studies have shown that epigenetic dysregulation is associated with multiple steps during carcinogenesis. Therefore, invention of blood-based DNA methylation biomarkers and their high-sensitive detection system may be a promising diagnostic tool for pancreatic cancer. In order to establish the diagnostic system, first, we performed genome-wide DNA methylation analysis of 38 EUS-FNA specimens of pancreatic cancer with clinical stage III-IV using Illumina Infinium HumanMethylation450 BeadChip. We further analyzed the DNA methylation profiles of other types of tumors in the public database, TCGA (The Cancer Genome Atlas), and identified five marker genes, which were specifically methylated in pancreatic cancers. In addition, analysis of DNA methylation status of pancreas cancers comparing 10 normal tissues in TCGA data set revealed that 99% of tumors were methylated at least one of the five markers (sensitivity, 98.9%; specificity, 44%). We next examined the DNA methylation status in the markers in the validation cohort (n=19) by bisulfite pyrosequencing and quantitative methylation specific PCR and found that 18/19 (95%) cases were methylated in at least one marker (AUC=0.95). Currently, our preliminary data showed that more than 95% of cancer patients have aberrant DNA methylation in circulating free DNA (cfDNA). Our results indicate that detection of DNA methylation in the cfDNA might be a promising and potent tool for diagnosis of pancreatic cancers. Citation Format: Keiko Shinjo, Yutaka Kondo. Use of DNA methylation in circulating free DNA as a potent biomarker for pancreatic cancer detection. [abstract]. In: Proceedings of the AACR Special Conference on Chromatin and Epigenetics in Cancer; Sep 24-27, 2015; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2016;76(2 Suppl):Abstract nr B14.

The proneural basic-helix-loop-helix protein achaete-scute homologue 1 (ASH1) is expressed in a very limited spectrum of normal and cancerous cells in a lineage-specific manner, including normal pulmonary neuroendocrine cells and lung cancer cells with neuroendocrine features. Our previous results indicated that ASH1 may play a crucial role in the growth and survival of lung cancers with neuroendocrine features, which prompted us to investigate the molecular function of ASH1 in relation to its involvement in carcinogenic processes. Herein, we report for the first time that ASH1 functions as a dual transcription factor by activating neuroendocrine differentiation markers and also repressing putative tumor suppressors. This protein was found to inactivate DKK1 and DKK3, negative regulators of Wnt/β-catenin signaling, E-cadherin, and integrin β1 through ASH1-mediated deacetylation and repressive trimethylation of lysine 27 (H3K27me3) of histone H3 in the promoter regions of DKK1 and E-cadherin. In addition, ASH1-transduced A549 adenocarcinoma cells exhibited markedly altered morphology characteristics compared with lung cancer cells with neuroendocrine features both in vitro and in vivo and also grew faster in vivo. Our results provide important clues for a better understanding of the molecular and cellular biological roles of ASH1 in the process of carcinogenesis of lung cancers with neuroendocrine features and warrant future investigations to shed light on the lineage-specific dependency of this transcription factor with dual functions. [Cancer Res 2008;68(6):1647–55]

Aberrant promoter hypermethylation and associated gene silencing are epigenetic hallmarks of tumorigenesis. It has been suggested that aberrant DNA methylation can affect the sensitivity of cancers to antineoplastic agents by altering expression of genes critical to drug response. To study this issue, we used bisulfite PCR to assess DNA methylation of 32 promoter-associated CpG islands in human cancer cell lines from the National Cancer Institute (NCI) drug-screening panel (NCI-60 panel). The frequency of aberrant hypermethylation of these islands ranged from 2% to 81% in NCI-60 cancer cells, and provided a database that can be analyzed for the sensitivity to ≈30,000 drugs tested in this panel. By correlating drug activity with DNA methylation, we identified a list of methylation markers that predict sensitivity to chemotherapeutic drugs. Among them, hypermethylation of the p53 homologue p73 and associated gene silencing was strongly correlated with sensitivity to alkylating agents. We used small interfering RNA to down-regulate p73 expression in multiple cell lines, including the resistant cell lines TK10 (renal cancer) and SKMEL28 (melanoma). Down-regulating p73 substantially increased sensitivity to commonly used alkylating agents, including cisplatin, indicating that epigenetic silencing of p73 directly modulates drug sensitivity. Our results confirm that epigenetic profiles are useful in identifying molecular mediators for cancer drug sensitivity (pharmaco-epigenomics). [Cancer Res 2007;67(23):11335–43]

Inactivation of methylcytosine dioxygenase, ten-eleven translocation (TET) is known to be associated with aberrant DNA methylation in cancers. Tumors with a CpG island methylator phenotype (CIMP), a distinct subgroup with extensive DNA methylation, show characteristic features in the case of colorectal cancer (CRC). The relationship between TET inactivation and CIMP in CRCs is not well understood. The expression level of TET family genes was compared between CIMP-positive (CIMP-P) and CIMP-negative (CIMP-N) CRCs. Furthermore, DNA methylation profiling, including assessment of the TET1 gene, was assessed in CRCs, as well as colon polyps. The TET1 was silenced by DNA methylation in a subset of CRCs as well as cell lines, expression of which was reactivated by demethylating agent. TET1 methylation was more frequent in CIMP-P (24/55, 44%) than CIMP-N (3/113, 3%, P Citation Format: Norihisa Ichimura, Keiko Shinjo, Fumiharu Ohka, Keisuke Katsushima, Akira Hatanaka, Masayuki Tojo, Yasuhiro Shimizu, Eiichiro Yamamoto, Hiromu Suzuki, Yutaka Kondo. Aberrant TET1 methylation closely associated with CpG island methylator phenotype in colorectal 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 1054. doi:10.1158/1538-7445.AM2015-1054

A variety of tumor suppressor genes are down-regulated by hypermethylation during carcinogenesis. Using methylated CpG amplification-representation difference analysis, we identified a DNA fragment corresponding to the Tazarotene-induced gene 1 (TIG1) promoter-associated CpG island as one of the genes hypermethylated in the leukemia cell line K562. Because TIG1 has been proposed to act as a tumor suppressor, we tested the hypothesis that cytosine methylation of the TIG1 promoter suppresses its expression and causes a loss of responsiveness to retinoic acid in some neoplastic cells. We examined TIG1 methylation and expression status in 53 human cancer cell lines and 74 primary tumors, including leukemia and head and neck, breast, colon, skin, brain, lung, and prostate cancer. Loss of TIG1 expression was strongly associated with TIG1 promoter hypermethylation (P < 0.001). There was no correlation between TIG1 promoter methylation and that of retinoid acid receptor β2 (RARβ2), another retinoic-induced putative tumor suppressor gene (P = 0.78). Treatment with the DNA methyltransferase inhibitor 5-aza-2′-deoxycytidine for 5 days restored TIG1 expression in all eight silenced cell lines tested. TIG1 expression was also inducible by treatment with 1 μm all-trans-retinoic acid for 3 days except in densely methylated cell lines. Treatment of the K562 leukemia cells with demethylating agent combined with all-trans-retinoic acid induced apoptosis. These findings indicate that silencing of TIG1 promoter by hypermethylation is common in human cancers and may contribute to the loss of retinoic acid responsiveness in some neoplastic cells.

Background and aims: While the connection between chronic inflammation and tumorigenesis was suspected in hepatocellular carcinomas (HCCs), key factors linking these two processes were not completely understood. Ample evidence shows that accumulation of genetic and epigenetic abnormalities may be fundamental mechanisms underlying tumor formation. The aim of this study is to examine whether viral infection affects epigenetic profile in chronic hepatitis/liver cirrhosis (CH/LC) and HCC tissues. Methods: To evaluate the direct effects of viral infection, we examined DNA methyaltion changes in hepatitis C virus (HCV) infected cells in vitro. Genome-wide DNA methylation status was examined in liver tissues repopulated with human hepatocytes (humanized liver) in uPA/SCID mice, which were infected with hepatitis B virus (HBV-mice, 13 mice) or HCV-mice (14 mice), using methylated CpG island amplification-microarrays (MCAM, 6,157 CpG islands). Genome-wide DNA methylation status was also examined in 37 HCCs: 19 and 18 were associated with HCV and HBV infection, respectively (HCC-HBV and HCC-HCV). Further, quantitative pyrosequencing analysis was performed to examine the methylation status of selected genes. Result: MCAM analysis in humanized mouse liver revealed that larger number of genes were methylated in HCV-mice than HBV-mice (287 genes versus 157 genes, P=0.034, respectively). DNA methylation target genes in HBV-mice were also methylated in HCV-mice, while both HBV-mice and HCV-mice had own specific targets. Association between aberrant DNA methylation and infection period was more strongly observed in HBV-mice (r=0.769) than HCV-mice (r=0.175). Interestingly, both HBV and HCV affected DNA methylation not only in infected humanized liver (hepatocytes) but also surrounding mouse tissues (non-infected cells). In vitro analysis of HCV infection did not affect DNA methylaion in cultured cells for more than a month. Thses data suggest that HCV infection may affect DNA methylaiton via inflammatory responses. Consistently, various cytokines from mouse tissues were upregulated after HBV and HCV infections. In clinical samples, most of the DNA methylation target genes in HCC-HBV were also methylated in HCC-HCV, as was found in mouse model. In addition, many DNA methylation target genes in human HCCs were also identified in mouse model with MCAM analysis. Conclusion: We developed mouse model to assess DNA methylaton profiling after hepatitis viral infection. Although HBV protein has been known to induce aberrant DNA methylation, our data sugget that viral infection is a strong inducer of aberrant DNA methylation via inflammatory responses. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4811. doi:10.1158/1538-7445.AM2011-4811

Aberrant activation of the canonical Wnt pathway due to accumulation of β-catenin occurs in approximately 70% of hepatocellular carcinomas (HCCs) and contributes to their initiation, development and progression. Genetic mutations in the components of this pathway account for only a subset of HCCs with β-catenin accumulation, suggesting that an alternative mechanism for Wnt/β-catenin activation is prevailing. Enhancer of zeste homolog 2 (EZH2) is known to promote tumorigenesis by down-regulating tumor-suppressor genes; however, whether EZH2 regulates oncogenic pathways is unclear. Using chromatin immunoprecipitation microarray, we uncovered 12 Wnt/β-catenin signal antagonists whose promoters were concordantly occupied by EZH2 and repressive histone modifications in hepatocellular HCC cells. EZH2 over-expressed in 42% (75/179) of human HCCs and significantly associated with β-catenin accumulation. Concomitant inhibition of EZH2 and histone deacetylase transcriptionally activated Wnt/β-catenin signal antagonists, suppressed T-cell factor-dependent transcriptional activity and down-regulated β-catenin transcriptional targets in HCC cells. Conversely, ectopic EZH2 over-expression in nontumorigenic hepatocytes increased cellular proliferation in a β-catenin-dependent manner and promoted tumorigenicity. This study uncovers an EZH2-mediated epigenetic mechanism that leads to Wnt/β-catenin signaling dyregulation in human HCC and suggests that therapeutic interventions targeting EZH2 may confer a clinical benefit in β-catenin-driven malignancies. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4881.