The Role of epigenetic modifications of DNA and histones in the treatment of oncohematological diseases

Introduction. Current knowledge of tumour biology attests a dual genetic and epigenetic nature of cancer cell abnormalities. Tumour epigenetics research provided insights into the key pathways mediating oncogenesis and facilitated novel epigenetic therapies.Aim — an overview of intricate involvement of epigenetic change in haematological morbidity and current therapeutic approaches to target the related mechanisms.Main findings. We review the best known epigenetic marks in tumour cells, e.g. DNA cytosine methylation, methylation and acetylation of histone proteins, the underlying enzymatic machinery and its role in oncogenesis. The epigenetic profile-changing drugs are described, including DNA hypomethylating agents, histone deacetylase and methylase inhibitors. A particular focus is made on substances currently approved in haematological therapy or undergoing clinical trial phases for future clinical availability.

Evidence of origin with epigenetic change of metachronous lesions in early gastric cancer after endoscopic submucosal dissection

Early gastric cancer (EGC) with metachronous lesions developing on scars after endoscopic submucosal dissection (ESD) is extremely rare and hard to treat. We evaluated whether DNA methylation of the cancer-specific methylation gene, cysteine dioxygenase type 1 (CDO1), would predict such lesions. CDO1 methylation (TaqMeth) values were compared between 11 patients with metachronous lesions developing on scars after ESD (M group) identified from 2,055 patients (0.5%) and 33 patients with EGC with no confirmed evidence of metachronous lesions at > 3 years after ESD (solitary [S] group). To assess Helicobacter pylori influence, 11 H. pylori-negative EGC patients (N group) were also analyzed. Each ESD specimen was measured at the tumor (T) and 4-points separated tumor-adjacent noncancerous mucosa (TAM). TaqMeth values for T were significantly higher than TAM (S + M) (P = 0.0019) and TAM (N) (P < 0.0001). Moreover, TAM (M) had significantly higher TaqMeth values than TAM (S) (P < 0.0001) suggesting that TAM (M) exhibited CDO1 hypermethylation similar to T (P = 0.5713). Additionally, TaqMeth values for TAM (S) were significantly higher than TAM (N) (P < 0.0001). The receiver operating characteristic for discriminating the highest TaqMeth values separated TAMs (M) from those of TAMs (S) was 0.81. CDO1 hypermethylation promisingly predicted EGC with metachronous lesions developing on scars after ESD.

The Epigenetic Modulation of Cancer and Immune Pathways in Hepatitis B Virus-Associated Hepatocellular Carcinoma: The Influence of HBx and miRNA Dysregulation

Hepatitis B virus (HBV)-associated hepatocellular carcinoma (HBV-HCC) pathogenesis is fueled by persistent HBV infection that stealthily maintains a delicate balance between viral replication and evasion of the host immune system. HBV is remarkably adept at using a combination of both its own, as well as host machinery to ensure its own replication and survival. A key tool in its arsenal, is the HBx protein which can manipulate the epigenetic landscape to decrease its own viral load and enhance persistence, as well as manage host genome epigenetic responses to the presence of viral infection. The HBx protein can initiate epigenetic modifications to dysregulate miRNA expression which, in turn, can regulate downstream epigenetic changes in HBV-HCC pathogenesis. We attempt to link the HBx and miRNA induced epigenetic modulations that influence both the HBV and host genome expression in HBV-HCC pathogenesis. In particular, the review investigates the interplay between CHB infection, the silencing role of miRNA, epigenetic change, immune system expression and HBV-HCC pathogenesis. The review demonstrates exactly how HBx-dysregulated miRNA in HBV-HCC pathogenesis influence and are influenced by epigenetic changes to modulate both viral and host genome expression. In particular, the review identifies a specific subset of HBx induced epigenetic miRNA pathways in HBV-HCC pathogenesis demonstrating the complex interplay between HBV infection, epigenetic change, disease and immune response. The wide-ranging influence of epigenetic change and miRNA modulation offers considerable potential as a therapeutic option in HBV-HCC.

Coping with darkness: The adaptive response of marine picocyanobacteria to repeated light energy deprivation

The picocyanobacteria Prochlorococcus and Synechococcus are found throughout the ocean’s euphotic zone, where the daily light:dark cycle drives their physiology. Periodic deep mixing events can, however, move cells below this zone, depriving them of light for extended periods of time. Here we demonstrate that Prochlorococcus and Synechococcus can adapt to tolerate repeated periods of light energy deprivation. Cyanobacterial cultures kept in the dark for 3 days and then returned to the light initially required 18-26 days to resume growth, but after multiple rounds of dark exposure the strains began to regrow after only 1-2 days. This dark-tolerant phenotype was stable and heritable; cultures retained the trait across at least 18-21 generations even when grown in a standard 13:11 light:dark cycle. We found no genetic differences between the dark-tolerant and parental strains of Prochlorococcus NATL2A, indicating that an epigenetic change is responsible for the adaptation. To begin to explore this possibility, we asked whether DNA methylation – an epigenetic mechanism in bacteria – occurs in Prochlorococcus. LC-MS/MS analysis showed that while DNA methylations, including 6mA and 5mC, are found in some other Prochlorococcus strains, no methylations were detected in either the parental or dark-tolerant strain used in our experiments –i.e. the NATL2A strain. These findings suggest that Prochlorococcus utilizes a yet-to-be-determined epigenetic mechanism to adapt to the stress of extended light energy deprivation.

Age-associated epigenetic change in chimpanzees and humans

Methylation levels have been shown to change with age at sites across the human genome. Change at some of these sites is so consistent across individuals that it can be used as an ‘epigenetic clock’ to predict an individual's chronological age to within a few years. Here, we examined how the pattern of epigenetic ageing in chimpanzees compares with humans. We profiled genome-wide blood methylation levels by microarray for 113 samples from 83 chimpanzees aged 1–58 years (26 chimpanzees were sampled at multiple ages during their lifespan). Many sites (greater than 65 000) showed significant change in methylation with age and around one-third (32%) of these overlap with sites showing significant age-related change in humans. At over 80% of sites showing age-related change in both species, chimpanzees displayed a significantly faster rate of age-related change in methylation than humans. We also built a chimpanzee-specific epigenetic clock that predicted age in our test dataset with a median absolute deviation from known age of only 2.4 years. However, our chimpanzee clock showed little overlap with previously constructed human clocks. Methylation at CpGs comprising our chimpanzee clock showed moderate heritability. Although the use of a human microarray for profiling chimpanzees biases our results towards regions with shared genomic sequence between the species, nevertheless, our results indicate that there is considerable conservation in epigenetic ageing between chimpanzees and humans, but also substantial divergence in both rate and genomic distribution of ageing-associated sites. This article is part of the theme issue ‘Evolution of the primate ageing process'.

The Epigenetic Modification of Epigallocatechin Gallate (EGCG) on Cancer

: Among the major components of green tea, epigallocatechin-3-gallate (EGCG) is the most effective for its anti-cancer characteristics. The bulk of studies provide the mechanisms of suppressive function of EGCG are involved in alteration of cancer cell cycle, development, and apoptosis through activation/inhibition of several signal pathways. : Another mechanism that explains the multiple effects exerted by EGCG in cancer is the epigenetic change by DNA methylation or methyltransferases, histone acetylation or deacetylases, and no coding RNAs (micoRNAs). Furthermore, decontrolled expression of miRNA transcription has been tested to be directly regulated by oncogenic and tumor-suppressor transcription factors. Recently, several proteins have been identified as miRNA direct interactors by EGCG. However, the mechanisms explaining the action of miRNA being modulated by EGCG have not been completely understood yet. This review summarizes the state of epigenetic change being modulated by EGCG in a variety of cancers and oncogenic and tumor-suppressor transcription factors.