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Biomarker discovery and validation are necessary for improving the prediction of clinical outcomes and patient monitoring. Despite considerable interest in biomarker discovery and development, improvements in the range and quality of biomarkers are still needed. The main challenge is how to integrate preclinical data to obtain a reliable biomarker that can be measured with acceptable costs in routine clinical practice. Epigenetic alterations are already being incorporated as valuable candidates in the biomarker field. Furthermore, their reversible nature offers a promising opportunity to ameliorate disease symptoms by using epigenetic-based therapy. Thus, beyond helping to understand disease biology, clinical epigenetics is being incorporated into patient management in oncology, as well as being explored for clinical applicability for other human pathologies such as neurological and infectious diseases and immune system disorders.

Key Points Alterations in epigenetic marks — specifically DNA methylation — are an emerging biomarker that may be used in the decision-making process for disease diagnosis, prognosis and treatment, most notably in cancer, but there are examples in other diseases, such as type 1 diabetes. Alterations in epigenetic marks that are chosen as biomarkers must be carefully selected owing to the dynamic nature of these marks. These alterations may be detected in non-invasive tissues, such as serum, in addition to primary tissues and so may have advantages over genetic biomarkers. Glutathione S -transferase pi 1 ( GSTP1 ) is the best-studied example of an epigenetic biomarker for cancer diagnosis. However, additional candidates show a high potential for future clinical applications, although specificity of diagnosis is an issue, and combinatorial approaches analysing DNA methylation alterations at several genes may improve this. Single-gene approaches have identified epigenetic biomarkers that predict cancer recurrence and survival. Recently, high-resolution genome-wide technologies have shown the potential to improve this strategy with DNA methylation signatures of cancers showing high predictive capacity of disease prognosis. DNA methylation alterations may be used as biomarkers to predict response to chemotherapy strategies. O 6 -methylguanine DNA methyltransferase ( MGMT ) and breast cancer 1, early onset ( BRCA1 ) are examples of hypermethylated genes that predict a response to chemotherapy in cancer. Additional prognostic gene markers have already been identified and suggest DNA methylation profiling as a potent strategy to predict drug response. Recent advances in sequencing and array technologies, which are capable of screening DNA methylomes genome-wide at high-resolution, gave unexpected novel insights in cancer biology. They will be crucial for DNA methylation profiling and the identification of epigenetic biomarker for diagnosis, prognosis and prediction of drug response. Epigenetic alterations, notably in DNA hypermethylation, are emerging as consistent biomarkers for disease. Here, with a focus on cancer, the authors discuss the identification of these biomarkers and their use in disease diagnosis, prognosis and response to therapy. Knowledge of epigenetic alterations in disease is rapidly increasing owing to the development of genome-wide techniques for their identification. The ever-growing number of genes that show epigenetic alterations in disease emphasizes the crucial role of these epigenetic alterations — particularly DNA methylation — for future diagnosis, prognosis and prediction of response to therapies. This Review focuses on epigenetic profiling, which has started to be of clinical value in cancer and may in the future be extended to other diseases, such as neurological and autoimmune disorders.

The number and types of known functional noncoding RNAs (ncRNAs) has increased considerably over the past few years, and both cis - and trans -acting ncRNAs have been reported. This Review focuses on long- and short-sized ncRNAs that act in cis ; that is, where both the regulatory RNA and the target gene are transcribed from the same locus. In recent years, the number and types of known functional noncoding RNAs have increased considerably. A subset of both short- and long-sized species are known to be involved in the cis regulation of target genes located at or near the same genomic locus. Their expression is often coordinated with that of neighboring protein-coding genes, and in many cases, related transcripts can influence each other at one step or another during their biogenesis. Here, we review the current literature, summarizing the existing knowledge about mammalian cis -acting RNAs and their impact on physiological and disease states.

Of the diverse array of putative molecular and biological functions assigned to long non-coding RNAs (lncRNAs), one attractive perspective in epigenetic research has been the hypothesis that lncRNAs directly interact with the proteins involved in the modulation of chromatin conformation. Indeed, epigenetic modifiers are among the most frequent protein partners of lncRNAs that have been identified to date, of which histone methyltransferases and protein members of the Polycomb Repressive Complex PRC2 have received considerable attention. This review is focused on how lncRNAs interface with epigenetic factors to shape the outcomes of crucial biological processes such as regulation of gene transcription, modulation of nuclear architecture, X inactivation in females and pre-mRNA splicing. Because of our increasing knowledge of their role in development and cellular differentiation, more research is beginning to be done into the deregulation of lncRNAs in human disorders. Focusing on cancer, we describe some key examples of disease-focused lncRNA studies. This knowledge has significantly contributed to our ever-improving understanding of how lncRNAs interact with epigenetic factors of human disease, and has also provided a plethora of much-needed novel prognostic biomarker candidates or potential therapeutic targets. Finally, current limitations and perspectives on lncRNA research are discussed here. This article is part of a discussion meeting issue ‘Frontiers in epigenetic chemical biology’.

Chronological age is a risk factor for SARS-CoV-2 infection and severe COVID-19. Previous findings indicate that epigenetic age could be altered in viral infection. However, the epigenetic aging in COVID-19 has not been well studied. In this study, DNA methylation of the blood samples from 232 healthy individuals and 413 COVID-19 patients is profiled using EPIC methylation array. Epigenetic ages of each individual are determined by applying epigenetic clocks and telomere length estimator to the methylation profile of the individual. Epigenetic age acceleration is calculated and compared between groups. We observe strong correlations between the epigenetic clocks and individual’s chronological age ( r  > 0.8, p  < 0.0001). We also find the increasing acceleration of epigenetic aging and telomere attrition in the sequential blood samples from healthy individuals and infected patients developing non-severe and severe COVID-19. In addition, the longitudinal DNA methylation profiling analysis find that the accumulation of epigenetic aging from COVID-19 syndrome could be partly reversed at late clinic phases in some patients. In conclusion, accelerated epigenetic aging is associated with the risk of SARS-CoV-2 infection and developing severe COVID-19. In addition, the accumulation of epigenetic aging from COVID-19 may contribute to the post-COVID-19 syndrome among survivors. Age is a risk factor for SARS-CoV-2 infection and severe disease. Here the authors perform DNA methylation analyses in whole blood from COVID-19 patients using established epigenetic clocks and telomere length estimators, and describing correlations between epigenetic aging and the risk of SARS-CoV-2 infection and severe disease.

DNA methylation is the best known epigenetic mark. Cancer and other pathologies show an altered DNA methylome. However, delivering complete DNA methylation maps is compromised by the price and labor-intensive interpretation of single nucleotide methods. Following the success of the HumanMethylation450 BeadChip (Infinium) methylation microarray (450K), we report the technical and biological validation of the newly developed MethylationEPIC BeadChip (Infinium) microarray that covers over 850,000 CpG methylation sites (850K). The 850K microarray contains >90% of the 450K sites, but adds 333,265 CpGs located in enhancer regions identified by the ENCODE and FANTOM5 projects. The 850K array demonstrates high reproducibility at the 450K CpG sites, is consistent among technical replicates, is reliable in the matched study of fresh frozen versus formalin-fixed paraffin-embeded samples and is also useful for 5-hydroxymethylcytosine. These results highlight the value of the MethylationEPIC BeadChip as a useful tool for the analysis of the DNA methylation profile of the human genome.

We have come a long way since the first reports of the existence of aberrant DNA methylation in human cancer. Hypermethylation of CpG islands located in the promoter regions of tumor suppressor genes is now firmly established as an important mechanism for gene inactivation. CpG island hypermethylation has been described in almost every tumor type. Many cellular pathways are inactivated by this type of epigenetic lesion: DNA repair (hMLH1, MGMT), cell cycle (p16(INK4a), p15(INK4b), p14(ARF)), apoptosis (DAPK), cell adherence (CDH1, CDH13), detoxification (GSTP1), etc em leader However, we still know little of the mechanisms of aberrant methylation and why certain genes are selected over others. Hypermethylation is not an isolated layer of epigenetic control, but is linked to the other pieces of the puzzle such as methyl-binding proteins, DNA methyltransferases and histone deacetylase, but our understanding of the degree of specificity of these epigenetic layers in the silencing of specific tumor suppressor genes remains incomplete. The explosion of user-friendly technologies has given rise to a rapidly increasing list of hypermethylated genes. Careful functional and genetic studies are necessary to determine which hypermethylation events are truly relevant for human tumorigenesis. The development of CpG island hypermethylation profiles for every form of human tumors has yielded valuable pilot clinical data in monitoring and treating cancer patients based in our knowledge of DNA methylation. Basic and translational will both be needed in the near future to fully understand the mechanisms, roles and uses of CpG island hypermethylation in human cancer. The expectations are high.

▪ Abstract  Aberrant DNA methylation is the most common molecular lesion of the cancer cell. Neither gene mutations (nucleotide changes, deletions, recombinations) nor cytogenetic abnormalities are as common in human tumors as DNA methylation alterations. The most studied change of DNA methylation in neoplasms is the silencing of tumor suppressor genes by CpG island promoter hypermethylation, which targets genes such as p16 INK4a , BRCA1, and hMLH1. There is a profile of CpG island hypermethylation according to the tumor type, and genes silent by methylation represent all cellular pathways. The introduction of bisulfite-PCR methodologies combined with new genomic approaches provides a comprehensive spectrum of the genes undergoing this epigenetic change across all malignancies. However, we still know very little about how this aberrant DNA methylation “invades” the previously unmethylated CpG island and how it is maintained through cell divisions. Furthermore, we should remember that this methylation occurs in the context of a global genomic loss of 5-methylcytosine (5mC). Initial clues to understand this paradox should be revealed from the current studies of DNA methyltransferases and methyl CpG binding proteins. From the translational standpoint, we should make an effort to validate the use of some hypermethylated genes as biomarkers of the disease; for example, it may occur with MGMT and GSTP1 in brain and prostate tumors, respectively. Finally, we must expect the development of new and more specific DNA demethylating agents that awake these methyl-dormant tumor suppressor genes and prove their therapeutic values. The expectations are high.

B-cell acute lymphoblastic leukemia (B-ALL) remains a major clinical challenge in hematologic oncology, characterized by a continuous evolution of molecular drivers that shape its heterogeneity across the age spectrum. Pediatric B-ALL is generally associated with high cure rates, while adult forms of the disease are often more aggressive and less responsive to treatment. This review examines the age-specific genetic and epigenetic landscapes that contribute to this disparity, revealing how the nature and timing of molecular alterations point to fundamentally different leukemogenic processes. Favorable genetic aberrations, such as ETV6::RUNX1 and hyperdiploidy, are predominant in children, whereas adults more frequently present with high-risk features, including BCR::ABL1 fusions and IKZF1 deletions. Epigenetic distinctions are similarly age-dependent, involving divergent patterns of DNA methylation, histone modifications, and non-coding RNA expression. For example, pediatric B-ALL frequently harbors mutations in epigenetic regulators like SETD2 and CREBBP, while adult B-ALL is more commonly affected by alterations in TET2 and IDH1/2. These molecular differences are not only prognostic but also mechanistic, reflecting distinct developmental trajectories and vulnerabilities. Understanding these age-driven transitions is essential for improving risk stratification and developing precision therapies tailored to the unique biology of B-ALL across the lifespan.

Mitotic cell division increases tumour mutation burden and copy number load, predictive markers of the clinical benefit of immunotherapy. Cell division correlates also with genomic demethylation involving methylation loss in late-replicating partial methylation domains. Here we find that immunomodulatory pathway genes are concentrated in these domains and transcriptionally repressed in demethylated tumours with CpG island promoter hypermethylation. Global methylation loss correlated with immune evasion signatures independently of mutation burden and aneuploidy. Methylome data of our cohort ( n  = 60) and a published cohort ( n  = 81) in lung cancer and a melanoma cohort ( n  = 40) consistently demonstrated that genomic methylation alterations counteract the contribution of high mutation burden and increase immunotherapeutic resistance. Higher predictive power was observed for methylation loss than mutation burden. We also found that genomic hypomethylation correlates with the immune escape signatures of aneuploid tumours. Hence, DNA methylation alterations implicate epigenetic modulation in precision immunotherapy. Demethylation of the genome is found in cancer. Here, the authors show that genomic demethylation entails changes in promoter methylation and gene expression associated with immune escape and suggest that the epigenetic alterations may be an important determinant of responses to immunotherapy.