Histone Lysine Methylation Dynamics Control EGFR DNA Copy-Number Amplification

Controllers of histone methylation-modifying enzymes in gastrointestinal cancers

Gastrointestinal (GI) cancers have been considered primarily genetic malignancies, caused by a series of progressive genetic alterations. Accumulating evidence shows that histone methylation, an epigenetic modification program, plays an essential role in the different pathological stages of GI cancer progression, such as precancerous lesions, tumorigenesis, and tumor metastasis. Histone methylation-modifying enzymes, including histone methyltransferases (HMTs) and demethylases (HDMs), are the main executor of post-transcriptional modification. The abnormal expression of histone methylation-modifying enzymes characterizes GI cancers with complex pathogenesis and progression. Interactions between upstream controllers and histone methylation-modifying enzymes have recently been revealed, and have provided numerous opportunities to elucidate the pathogenesis of GI cancers in depth and clearly. Here we focus on the association between histone methylation-modifying enzymes and their controllers, aiming to provide a new perspective on the molecular research and clinical management of GI cancers.

Categorizing Extrachromosomal Circular DNA as Biomarkers in Serum of Cancer

Extrachromosomal circular DNA (eccDNA), a double-stranded circular DNA molecule found in multiple organisms, has garnered an increasing amount of attention in recent years due to its close association with the initiation, malignant progression, and heterogeneous evolution of cancer. The presence of eccDNA in serum assists in non-invasive tumor diagnosis as a biomarker that can be assessed via liquid biopsies. Furthermore, the specific expression patterns of eccDNA provide new insights into personalized cancer therapy. EccDNA plays a pivotal role in tumorigenesis, development, diagnosis, and treatment. In this review, we comprehensively outline the research trajectory of eccDNA, discuss its role as a diagnostic and prognostic biomarker, and elucidate its regulatory mechanisms in cancer. In particular, we emphasize the potential application value of eccDNA in cancer diagnosis and treatment and anticipate the development of novel tumor diagnosis strategies based on serum eccDNA in the future.

Stromal Rigidity Stress Accelerates Pancreatic Intraepithelial Neoplasia Progression and Chromosomal Instability via Nuclear Protein Tyrosine Kinase 2 Localization

Because the mechanotransduction by stromal stiffness stimulates the rupture and repair of the nuclear envelope in pancreatic progenitor cells, accumulated genomic aberrations are under selection in the tumor microenvironment. Analysis of cell growth, micronuclei, and γH2AX foci links to mechanotransduction pressure in vivo during serial orthotopic passages of mouse KrasLSL-G12D/+;Trp53flox/flox;Pdx1-Cre (KPC) cancer cells in the tumor and in migrating through the size-restricted 3-μm micropores. To search for pancreatic cancer cell of origin, analysis of single-cell data sets revealed that the extracellular matrix shapes an alternate route of acinar-ductal transdifferentiation of acinar cells into a central hub of elegantly restrained topoisomerase II α (TOP2A)-overexpressing cancer cells that spread out as unique cancer clusters with copy number amplifications in MYC-PTK2 (protein tyrosine kinase 2) locus and PIK3CA. High-PTK2 expression is associated with 171 differentially methylated CpG loci, 319 differentially expressed genes, and poor overall survival in patients with The Cancer Genome Atlas-PAAD. Abolished RGD-integrin signaling by disintegrin KG blocked the PTK2 phosphorylation, increased cancer apoptosis, decreased VAV1 expression, and prolonged overall survival in the KPC mice. Decreases of α-smooth muscle actin deposition in the CD248 knockout KPC mice remodel the tissue stroma and down-regulated TOP2A expression in the epithelium. In summary, stromal stiffness induces the onset of cells of origin of cancer by ectopic TOP2A expression, and the genomic amplification of MYC-PTK2 locus via alternative transdifferentiation of pancreatic progenitor cells is the vulnerability useful for disintegrin KG treatment against cells-of-origin cancer.

Histone lysine demethylase 4 family proteins maintain the transcriptional program and adrenergic cellular state of MYCN-amplified neuroblastoma

Neuroblastoma with MYCN amplification (MNA) is a high-risk disease that has a poor survival rate. Neuroblastoma displays cellular heterogeneity, including more differentiated (adrenergic) and more primitive (mesenchymal) cellular states. Here, we demonstrate that MYCN oncoprotein promotes a cellular state switch in mesenchymal cells to an adrenergic state, accompanied by induction of histone lysine demethylase 4 family members (KDM4A-C) that act in concert to control the expression of MYCN and adrenergic core regulatory circulatory (CRC) transcription factors. Pharmacologic inhibition of KDM4 blocks expression of MYCN and the adrenergic CRC transcriptome with genome-wide induction of transcriptionally repressive H3K9me3, resulting in potent anticancer activity against neuroblastomas with MNA by inducing neuroblastic differentiation and apoptosis. Furthermore, a short-term KDM4 inhibition in combination with conventional, cytotoxic chemotherapy results in complete tumor responses of xenografts with MNA. Thus, KDM4 blockade may serve as a transformative strategy to target the adrenergic CRC dependencies in MNA neuroblastomas.

Epigenetic modifications: Key players in cancer heterogeneity and drug resistance

Cancer heterogeneity and drug resistance remain pivotal obstacles in effective cancer treatment and management. One major contributor to these challenges is epigenetic modifications - gene regulation that does not involve changes to the DNA sequence itself but significantly impacts gene expression. As we elucidate these phenomena, we underscore the pivotal role of epigenetic modifications in regulating gene expression, contributing to cellular diversity, and driving adaptive changes that can instigate therapeutic resistance. This review dissects essential epigenetic modifications - DNA methylation, histone modifications, and chromatin remodeling - illustrating their significant yet complex contributions to cancer biology. While these changes offer potential avenues for therapeutic intervention due to their reversible nature, the interplay of epigenetic and genetic changes in cancer cells presents unique challenges that must be addressed to harness their full potential. By critically analyzing the current research landscape, we identify knowledge gaps and propose future research directions, exploring the potential of epigenetic therapies and discussing the obstacles in translating these concepts into effective treatments. This comprehensive review aims to stimulate further research and aid in developing innovative, patient-centered cancer therapies. Understanding the role of epigenetic modifications in cancer heterogeneity and drug resistance is critical for scientific advancement and paves the way towards improving patient outcomes in the fight against this formidable disease.

Histone demethylase KDM6A coordinating with KMT2B regulates self-renewal and chemoresistance of non-small cell lung cancer stem cells

BACKGROUND AND AIMS

Wnt signaling is essential for the maintenance of cancer stem cells (CSCs), but mutations in the β-catenin and APC genes are less common in non-small cell lung carcinoma (NSCLC). Thus, the mechanism underlying the constitutive activation of Wnt signaling in lung CSCs is still unknown.

MATERIALS AND METHODS

Gene set enrichment analysis and immunohistochemistry were performed to establish the correlation between KDM6A/KM2B and CSC stemness. Human NSCLC cell lines were genetically manipulated for functional studies. Sphere formation assay and stemness gene expression profiling were examined to investigate the role of KDM6A/KMT2B in lung CSCs. Tumor xenograft assay were used to identify the function of KDM6A/KMT2B on tumorigenicity and tumor recurrence in vivo. Western blot analysis, coimmunoprecipitation and chromatin immunoprecipitation were performed to understand KDM6A/KMT2B mediated epigenetic regulation of Histone 3 lysine 4 methylation (H3K4me) on Wnt signaling pathway.

RESULTS

We discovered that the expression of Histone demethylase KDM6A and methyltransferase KMT2B correlate with the stemness of CSCs in NSCLC. KDM6A coordinates with KMT2B to activate the Wnt/β-catenin signaling pathway by regulating the H3K4me3 level and promotes the tumorigenicity and maintenance of CSC stemness. Furthermore, KDM6A/ KMT2B overexpression promotes the CSC chemoresistance and tumor recurrence both in vitro and in vivo. Inhibition of KDM6A and KMT2B potently suppress tumor initiation and recurrence in xenografted animal models.

CONCLUSION

Our findings suggest that KDM6A and KMT2B mediate the constitutive activation of Wnt/β-catenin signaling in lung CSCs, potentially providing a therapeutic target for NSCLC.

Epigenetic balance ensures mechanistic control of MLL amplification and rearrangement

MLL/KMT2A amplifications and translocations are prevalent in infant, adult, and therapy-induced leukemia. However, the molecular contributor(s) to these alterations are unclear. Here, we demonstrate that histone H3 lysine 9 mono- and di-methylation (H3K9me1/2) balance at the MLL/KMT2A locus regulates these amplifications and rearrangements. This balance is controlled by the crosstalk between lysine demethylase KDM3B and methyltransferase G9a/EHMT2. KDM3B depletion increases H3K9me1/2 levels and reduces CTCF occupancy at the MLL/KMT2A locus, in turn promoting amplification and rearrangements. Depleting CTCF is also sufficient to generate these focal alterations. Furthermore, the chemotherapy doxorubicin (Dox), which associates with therapy-induced leukemia and promotes MLL/KMT2A amplifications and rearrangements, suppresses KDM3B and CTCF protein levels. KDM3B and CTCF overexpression rescues Dox-induced MLL/KMT2A alterations. G9a inhibition in human cells or mice also suppresses MLL/KMT2A events accompanying Dox treatment. Therefore, MLL/KMT2A amplifications and rearrangements are controlled by epigenetic regulators that are tractable drug targets, which has clinical implications.

CUL4B-DDB1-COP1-mediated UTX downregulation promotes colorectal cancer progression

BACKGROUND

UTX (encoded by KDM6A), a histone demethylase for H3K27me2/3, is frequently mutated in human cancers. However, its functional and regulatory mechanisms in colorectal cancer (CRC) remain unclear.

METHODS

Immunohistochemistry staining was used to investigate the clinical relevance of UTX in CRC. Additionally, we generated a spontaneous mouse CRC model with conditional Utx knockout to explore the role of UTX in the colorectal tumorigenesis. Post-translational regulation of UTX was determined by co-immunoprecipitation and immunoblot analyses.

RESULTS

Herein, we identify that downregulation of UTX, mediated by the Cullin 4B-DNA Damage Binding Protein-1-Constitutive Photomorphogenesis Protein 1 (CUL4B-DDB1-COP1) complex, promotes CRC progression. Utx deletion in intestinal epithelial cells enhanced the susceptibility to tumorigenesis in AOM/DSS-induced spontaneous mouse CRC model. However, this effect is primarily alleviated by GSK126, an inhibitor of histone methyltransferase EZH2. Mechanistically, EMP1 and AUTS2 are identified as putative UTX target genes mediating UTX functions in limiting intestinal tumorigenesis. Notably, the CUL4B-DDB1-COP1 complex is identified as the functional E3 ligase responsible for targeting UTX for degradation in CRC cells. Thus, Cop1 deficiency in mouse intestinal tissue results in UTX accumulation and restricts tumorigenesis. Furthermore, patient cohort analysis reveals that UTX expression is negatively correlated with clinical stage, favorable disease outcomes, and COP1 expression.

CONCLUSIONS

In the current study, the tumor suppressor function and regulation of UTX in CRC provide a molecular basis and the rationale to target EZH2 in UTX-deficient CRC.

The H3K27 demethylase controls the lateral line embryogenesis of zebrafish

BACKGROUND

Kdm6b, a specific histone 3 lysine 27 (H3K27) demethylase, has been reported to be implicated in a variety of developmental processes including cell differentiation and cell fate determination and multiple organogenesis. Here, we regulated the transcript level of kdm6bb to study the potential role in controlling the hearing organ development of zebrafish.

METHODS

A morpholino antisense oligonucleotide (MO) strategy was used to induce Kdm6b deficiency; immunohistochemical staining and in situ hybridization analysis were conducted to figure out the morphologic alterations and embryonic mechanisms.

RESULTS

Kdm6bb is expressed in the primordium and neuromasts at the early stage of zebrafish embryogenesis, suggesting a potential function of Kdm6b in the development of mechanosensory organs. Knockdown of kdm6bb severely influences the cell migration and proliferation in posterior lateral line primordium, abates the number of neuromasts along the trunk, and mRNA-mediated rescue test can partially renew the neuromasts. Loss of kdm6bb might be related to aberrant expressions of chemokine genes encompassing cxcl12a and cxcr4b/cxcr7b in the migrating primordium. Moreover, inhibition of kdm6bb reduces the expression of genes in Fgf signaling pathway, while it increases the axin2 and lef1 expression level of Wnt/β-catenin signaling during the migrating stage.

CONCLUSIONS

Collectively, our results revealed that Kdm6b plays an essential role in guiding the migration of primordium and in regulating the deposition of zebrafish neuromasts by mediating the gene expression of chemokines and Wnt and Fgf signaling pathway. Since histone methylation and demethylation are reversible, targeting Kdm6b may present as a novel therapeutic regimen for hearing disorders.

Transition from Transient DNA Rereplication to Inherited Gene Amplification Following Prolonged Environmental Stress

Cells require the ability to adapt to changing environmental conditions, however, it is unclear how these changes elicit stable permanent changes in genomes. We demonstrate that, in response to environmental metal exposure, the metallothionein (MT) locus undergoes DNA rereplication generating transient site-specific gene amplifications (TSSGs). Chronic metal exposure allows transition from MT TSSG to inherited MT gene amplification through homologous recombination within and outside of the MT locus. DNA rereplication of the MT locus is suppressed by H3K27me3 and EZH2. Long-term ablation of EZH2 activity eventually leads to integration and inheritance of MT gene amplifications without the selective pressure of metal exposure. The rereplication and inheritance of MT gene amplification is an evolutionarily conserved response to environmental metal from yeast to human. Our results describe a new paradigm for adaptation to environmental stress where targeted, transient DNA rereplication precedes stable inherited gene amplification.

Extrachromosomal circular DNA in colorectal cancer: biogenesis, function and potential as therapeutic target

Extrachromosomal circular DNA (ecDNA) has gained renewed interest since its discovery more than half a century ago, emerging as critical driver of tumor evolution. ecDNA is highly prevalent in many types of cancers, including colorectal cancer (CRC), which is one of the most deadly cancers worldwide. ecDNAs play an essential role in regulating oncogene expression, intratumor heterogeneity, and resistance to therapy independently of canonical chromosomal alterations in CRC. Furthermore, the existence of ecDNAs is attributed to the patient's prognosis, since ecDNA-based oncogene amplification adversely affects clinical outcomes. Recent understanding of ecDNA put an extra layer of complexity in the pathogenesis of CRC. In this review, we will discuss the current understanding on mechanisms of biogenesis, and distinctive features of ecDNA in CRC. In addition, we will examine how ecDNAs mediate oncogene overexpression, gene regulation, and topological interactions with active chromatin, which facilitates genetic heterogeneity, accelerates CRC malignancy, and enhances rapid adaptation to therapy resistance. Finally, we will discuss the potential diagnostic and therapeutic implications of ecDNAs in CRC.

Extrachromosomal DNA amplifications in cancer

Extrachromosomal DNA (ecDNA) amplification is an important driver alteration in cancer. It has been observed in most cancer types and is associated with worse patient outcome. The functional impact of ecDNA has been linked to its unique properties, such as its circular structure that is associated with altered chromatinization and epigenetic regulatory landscape, as well as its ability to randomly segregate during cell division, which fuels intercellular copy number heterogeneity. Recent investigations suggest that ecDNA is structurally more complex than previously anticipated and that it localizes to specialized nuclear bodies (hubs) and can act in trans as an enhancer for genes on other ecDNAs or chromosomes. In this Review, we synthesize what is currently known about how ecDNA is generated and how its genetic and epigenetic architecture affects proto-oncogene deregulation in cancer. We discuss how recently identified ecDNA functions may impact oncogenesis but also serve as new therapeutic vulnerabilities in cancer.

A Macrophage Differentiation-Mediated Gene: DDX20 as a Molecular Biomarker Encompassing the Tumor Microenvironment, Disease Staging, and Prognoses in Hepatocellular Carcinoma

Background

DDX20 involves the mechanism of cell proliferate, mitogenic Ets transcriptional suppressor (METS), which can arrest the cell cycle of macrophages. However, little is known about DDX20 expression, clinical values, and the relationship with tumor microenvironment in HCC.

Methods

We mined the transcriptional, protein expression and survival data of DDX20 in HCC from online databases. The immunological effects of DDX20 were estimated by bioinformatic algorithms. The RNAi and CRISPR screening were used to assess the gene effect of DDX20 for the EGFR gene in liver tumor cell.

Results

We found that the DDX20 was highly expressed in HCC. The qRT-PCR result shows a significantly upregulated DDX20 expression in HCC samples from the West China Hospital. The high mRNA expression of DDX20 is associated with a poor survival. DDX20 expression is positively correlated with MDSCs in HCC tissues. Moreover, DDX20 has a high predicted ability for the response to immunotherapy. Furthermore, hsa-mir-324-5p could regulate the macrophage differentiation by interacting with DDX20. Meanwhile, the EGFR gene gets a high dependency score for DDX20.

Conclusion

In sum, DDX20 may serve as a prognostic marker for worse clinical outcomes with HCC and potentially enable more precise and personalized immunotherapeutic strategies in the future.

DNA repair as a shared hallmark in cancer and ageing

Increasing evidence demonstrates that DNA damage and genome instability play a crucial role in ageing. Mammalian cells have developed a wide range of complex and well‐orchestrated DNA repair pathways to respond to and resolve many different types of DNA lesions that occur from exogenous and endogenous sources. Defects in these repair pathways lead to accelerated or premature ageing syndromes and increase the likelihood of cancer development. Understanding the fundamental mechanisms of DNA repair will help develop novel strategies to treat ageing‐related diseases. Here, we revisit the processes involved in DNA damage repair and how these can contribute to diseases, including ageing and cancer. We also review recent mechanistic insights into DNA repair and discuss how these insights are being used to develop novel therapeutic strategies for treating human disease. We discuss the use of PARP inhibitors in the clinic for the treatment of breast and ovarian cancer and the challenges associated with acquired drug resistance. Finally, we discuss how DNA repair pathway‐targeted therapeutics are moving beyond PARP inhibition in the search for ever more innovative and efficacious cancer therapies.

Epigenetic Regulations of Perineural Invasion in Head and Neck Squamous Cell Carcinoma

Carcinomas of the oral cavity and oropharynx belong among the ten most common malignancies in the human population. The prognosis of head and neck squamous cell carcinoma (HNSCC) is determined by the degree of invasiveness of the primary tumor and by the extent of metastatic spread into regional and distant lymph nodes. Moreover, the level of the perineural invasion itself associates with tumor localization, invasion's extent, and the presence of nodal metastases. Here, we summarize the current knowledge about different aspects of epigenetic changes, which can be associated with HNSCC while focusing on perineural invasion (PNI). We review epigenetic modifications of the genes involved in the PNI process in HNSCC from the omics perspective and specific epigenetic modifications in OSCC or other neurotropic cancers associated with perineural invasion. Moreover, we summarize DNA methylation status of tumor-suppressor genes, methylation and demethylation enzymes and histone post-translational modifications associated with PNI. The influence of other epigenetic factors on the HNSCC incidence and perineural invasion such as tobacco, alcohol and oral microbiome is overviewed and HPV infection is discussed as an epigenetic factor associated with OSCC and related perineural invasion. Understanding epigenetic regulations of axon growth that lead to tumorous spread or uncovering the molecular control of axon interaction with cancer tissue can help to discover new therapeutic targets for these tumors.

Extrachromosomal Circular DNA: A New Target in Cancer

Genomic instability and amplification are intrinsically important traits determining the development and heterogeneity of tumors. The role of extrachromosomal circular DNA (eccDNA) in tumors has recently been highlighted. EccDNAs are unique genetic materials located off the chromosomal DNA. They have been detected in a variety of tumors. This review analyzes the mechanisms involved in the formation of eccDNAs and their genetic characteristics. In addition, the high-copy number and transcriptional levels of oncogenes located in eccDNA molecules contribute to the acceleration of tumor evolution and drug resistance and drive the development of genetic heterogeneity. Understanding the specific genomic forms of eccDNAs and characterizing their potential functions will provide new strategies for tumor therapy. Further research may yield new targets and molecular markers for the early diagnosis and treatment of human cancer.

Epigenetic Factors as Etiological Agents, Diagnostic Markers, and Therapeutic Targets for Luminal Breast Cancer

Luminal breast cancer, an etiologically heterogeneous disease, is characterized by high steroid hormone receptor activity and aberrant gene expression profiles. Endocrine therapy and chemotherapy are promising therapeutic approaches to mitigate breast cancer proliferation and recurrence. However, the treatment of therapy-resistant breast cancer is a major challenge. Recent studies on breast cancer etiology have revealed the critical roles of epigenetic factors in luminal breast cancer tumorigenesis and drug resistance. Tumorigenic epigenetic factor-induced aberrant chromatin dynamics dysregulate the onset of gene expression and consequently promote tumorigenesis and metastasis. Epigenetic dysregulation, a type of somatic mutation, is a high-risk factor for breast cancer progression and therapy resistance. Therefore, epigenetic modulators alone or in combination with other therapies are potential therapeutic agents for breast cancer. Several clinical trials have analyzed the therapeutic efficacy of potential epi-drugs for breast cancer and reported beneficial clinical outcomes, including inhibition of tumor cell adhesion and invasiveness and mitigation of endocrine therapy resistance. This review focuses on recent findings on the mechanisms of epigenetic factors in the progression of luminal breast cancer. Additionally, recent findings on the potential of epigenetic factors as diagnostic biomarkers and therapeutic targets for breast cancer are discussed.

Collective regulation of chromatin modifications predicts replication timing during cell cycle

Replication timing (RT) associates with genome architecture, while having a mixed relationship to histone marks. By profiling replication at high resolution and assessing broad histone marks across the cell cycle at the resolution of RT with and without genetic perturbation, we address the causal relationship between histone marks and RT. Four primary chromatin states, including an uncharacterized H3K36me2 state, emerge and define 97% of the mappable genome. RT and local replication patterns (e.g., initiation zones) quantitatively associate with chromatin states, histone mark dynamics, and spatial chromatin structure. Manipulation of broad histone marks and enhancer elements by overexpressing the histone H3 lysine 9/36 tri-demethylase KDM4A impacts RT across 11% of the genome. Broad histone modification changes were strong predictors of the observed RT alterations. Lastly, replication within H3K36me2-enriched neighborhoods is sensitive to KDM4A overexpression and is controlled at a megabase scale. These studies establish a role for collective chromatin mark regulation in modulating RT.

Van Rechem et al. establish that collective histone mark dynamics and their associated regulation modulate replication timing (RT). Four primary chromatin states define 97% of the mappable genome and associate with RT patterns. The K9/K36me3 demethylase KDM4A controls 11% of RT genome-wide through broad histone marks, especially H3K36me2, and enhancers.

Cancer evolution: Darwin and beyond

Clinical and laboratory studies over recent decades have established branched evolution as a feature of cancer. However, while grounded in somatic selection, several lines of evidence suggest a Darwinian model alone is insufficient to fully explain cancer evolution. First, the role of macroevolutionary events in tumour initiation and progression contradicts Darwin's central thesis of gradualism. Whole-genome doubling, chromosomal chromoplexy and chromothripsis represent examples of single catastrophic events which can drive tumour evolution. Second, neutral evolution can play a role in some tumours, indicating that selection is not always driving evolution. Third, increasing appreciation of the role of the ageing soma has led to recent generalised theories of age-dependent carcinogenesis. Here, we review these concepts and others, which collectively argue for a model of cancer evolution which extends beyond Darwin. We also highlight clinical opportunities which can be grasped through targeting cancer vulnerabilities arising from non-Darwinian patterns of evolution.

Drug resistance in colorectal cancer: An epigenetic overview

Colorectal cancer (CRC) is a leading cause of cancer-related deaths worldwide. Despite significant progress that has been made in therapies against CRC over the past decades, drug resistance is still a major limitation in CRC treatment. Numerous investigations have unequivocally shown that epigenetic regulation plays an important role in CRC drug resistance because of the high rate of epigenetic alterations in multiple genes during cancer development or drug treatment. Furthermore, the reversibility of epigenetic alterations provides novel therapeutic strategies to overcome drug resistance using small molecules, which can target non-coding RNAs or reverse histone modification and DNA methylation. In this review, we discuss epigenetic regulation in CRC drug resistance and the possible role of preventing or reversing CRC drug resistance using epigenetic therapy in CRC treatment.

Comprehensive data analysis of genomics, epigenomics, and transcriptomics to identify specific biomolecular markers for prostate adenocarcinoma

Background

Multiomics data analysis based on high-throughput sequencing technology has become a hotspot in tumor investigation. The present study aimed to explore prognostic biomarkers via investigating DNA copy number variation (CNV) and methylation variation (MET) data in prostate cancer.

Methods

We obtained the messenger RNA (mRNA) expression, CNV, and methylated data of prostate adenocarcinoma (PRAD) samples via The Cancer Genome Atlas (TCGA)-PRAD cohort. We calculated and assessed the associations between CNV and RNA sequencing (RNA-seq), and between MET and RNA-seq via Pearson correlation coefficients. We then used the "iCluster" package to perform multigroup cluster analysis with CNVcor gene CNV data, METcor gene methylation data, and CNVcor and METcor gene mRNA data. The univariate Cox analysis was used to screen significant hub genes, and multivariate Cox analysis was used to construct risk a model. The nomogram was constructed based on "rms" package, and the immune infiltrating patterns were compared between high- and low-risk groups.

Results

A total of 477 PRAD samples with complete CNV, methylation, mRNA, and matched clinical information were included in our study. A list of 10,073 CNVcor genes and 9841 METcor genes were confirmed with a significance level of P<0.01. We found that CNVcor is more likely to appear on chromosome (chr)8, chr17, and chr10, while METcor is more likely to appear on chr1, chr19, and chr17. Based on the core genes, we finally classified the samples into 4 subtypes, incorporating iC1 (iCluster) (92 samples), iC2 (79 samples), iC3 (165 samples), and iC4 (141 samples). Furthermore, we constructed the prognostic model for PRAD based on the 5 genes (IER3, AOX1, PRKCDBP, UBD, and FBLN5). Nomograms incorporating risk score and other clinical variables were further constructed, and these nomograms exhibited superior predictive ability. We further compared the differential immune infiltrating patterns in 2 risk groups and found significantly low levels of infiltrating cluster of differentiation (CD)8⁺ T cells in high-risk samples.

Conclusions

Our study integrated the multi-omics data to elucidate the molecular features of PRAD and pivotal genes for predicting prognosis.

The inhibitors of KDM4 and KDM6 histone lysine demethylases enhance the anti-growth effects of erlotinib and HS-173 in head and neck cancer cells

Novel therapeutics are required to improve treatment outcomes in head and neck squamous cell carcinoma (HNSCC) patients. Histone lysine demethylases (KDM) have emerged recently as new potential drug targets for HNSCC therapy. They might also potentiate the action of the inhibitors of EGFR and PI3K signaling pathways. This study aimed at evaluating the anti-cancer effects of KDM4 (ML324) and KDM6 (GSK-J4) inhibitors and their combinations with EGFR (erlotinib) and PI3K (HS-173) inhibitors in HNSCC cells. The effect of the inhibitors on the viability of CAL27 and FaDu cells was evaluated using resazurin assay. The effect of the chemicals on cell cycle and apoptosis was assessed using propidium iodide and Annexin V staining, respectively. The effect of the compounds on gene expression was determined using qPCR and Western blot. The changes in cell cycle distribution upon treatment with the compounds were small to moderate, with the exception of erlotinib, which induced G1 arrest. However, all the compounds and their combinations induced apoptosis in both cell lines. These effects were associated with changes in the level of expression of CDKN1A, CCND1 and BIRC5. The inhibition of KDM4 and KDM6 using ML324 and GSK-J4, respectively, can be regarded as a novel therapeutic strategy in HNSCC.

Genetic and non-genetic clonal diversity in cancer evolution

The observation and analysis of intra-tumour heterogeneity (ITH), particularly in genomic studies, has advanced our understanding of the evolutionary forces that shape cancer growth and development. However, only a subset of the variation observed in a single tumour will have an impact on cancer evolution, highlighting the need to distinguish between functional and non-functional ITH. Emerging studies highlight a role for the cancer epigenome, transcriptome and immune microenvironment in functional ITH. Here, we consider the importance of both genetic and non-genetic ITH and their role in tumour evolution, and present the rationale for a broad research focus beyond the cancer genome. Systems-biology analytical approaches will be necessary to outline the scale and importance of functional ITH. By allowing a deeper understanding of tumour evolution this will, in time, encourage development of novel therapies and improve outcomes for patients.

Drivers of dynamic intratumor heterogeneity and phenotypic plasticity

Cancer is a clonal disease, i.e., all tumor cells within a malignant lesion trace their lineage back to a precursor somatic cell that acquired oncogenic mutations during development and aging. And yet, those tumor cells tend to have genetic and nongenetic variations among themselves-which is denoted as intratumor heterogeneity. Although some of these variations are inconsequential, others tend to contribute to cell state transition and phenotypic heterogeneity, providing a substrate for somatic evolution. Tumor cell phenotypes can dynamically change under the influence of genetic mutations, epigenetic modifications, and microenvironmental contexts. Although epigenetic and microenvironmental changes are adaptive, genetic mutations are usually considered permanent. Emerging reports suggest that certain classes of genetic alterations show extensive reversibility in tumors in clinically relevant timescales, contributing as major drivers of dynamic intratumor heterogeneity and phenotypic plasticity. Dynamic heterogeneity and phenotypic plasticity can confer resistance to treatment, promote metastasis, and enhance evolvability in cancer. Here, we first highlight recent efforts to characterize intratumor heterogeneity at genetic, epigenetic, and microenvironmental levels. We then discuss phenotypic plasticity and cell state transition by tumor cells, under the influence of genetic and nongenetic determinants and their clinical significance in classification of tumors and therapeutic decision-making.

Mechanistic insights into KDM4A driven genomic instability

Alterations in global epigenetic signatures on chromatin are well established to contribute to tumor initiation and progression. Chromatin methylation status modulates several key cellular processes that maintain the integrity of the genome. KDM4A, a demethylase that belongs to the Fe-II dependent dioxygenase family that uses α-ketoglutarate and molecular oxygen as cofactors, is overexpressed in several cancers and is associated with an overall poor prognosis. KDM4A demethylates lysine 9 (H3K9me2/3) and lysine 36 (H3K36me3) methyl marks on histone H3. Given the complexity that exists with these marks on chromatin and their effects on transcription and proliferation, it naturally follows that demethylation serves an equally important role in these cellular processes. In this review, we highlight the role of KDM4A in transcriptional modulation, either dependent or independent of its enzymatic activity, arising from the amplification of this demethylase in cancer. KDM4A modulates re-replication of distinct genomic loci, activates cell cycle inducers, and represses proteins involved in checkpoint control giving rise to proliferative damage, mitotic disturbances and chromosomal breaks, ultimately resulting in genomic instability. In parallel, emerging evidence of non-nuclear substrates of epigenetic modulators emphasize the need to investigate the role of KDM4A in regulating non-nuclear substrates and evaluate their contribution to genomic instability in this context. The existence of promising KDM-specific inhibitors makes these demethylases an attractive target for therapeutic intervention in cancers.

Hypoxia-Inducible Lysine Methyltransferases: G9a and GLP Hypoxic Regulation, Non-histone Substrate Modification, and Pathological Relevance

Oxygen sensing is inherent among most animal lifeforms and is critical for organism survival. Oxygen sensing mechanisms collectively trigger cellular and physiological responses that enable adaption to a reduction in ideal oxygen levels. The major mechanism by which oxygen-responsive changes in the transcriptome occur are mediated through the hypoxia-inducible factor (HIF) pathway. Upon reduced oxygen conditions, HIF activates hypoxia-responsive gene expression programs. However, under normal oxygen conditions, the activity of HIF is regularly suppressed by cellular oxygen sensors; prolyl-4 and asparaginyl hydroxylases. Recently, these oxygen sensors have also been found to suppress the function of two lysine methyltransferases, G9a and G9a-like protein (GLP). In this manner, the methyltransferase activity of G9a and GLP are hypoxia-inducible and thus present a new avenue of low-oxygen signaling. Furthermore, G9a and GLP elicit lysine methylation on a wide variety of non-histone proteins, many of which are known to be regulated by hypoxia. In this article we aim to review the effects of oxygen on G9a and GLP function, non-histone methylation events inflicted by these methyltransferases, and the clinical relevance of these enzymes in cancer.

The lysine demethylase KDM4A controls the cell-cycle expression of replicative canonical histone genes

Chromatin modulation provides a key checkpoint for controlling cell cycle regulated gene networks. The replicative canonical histone genes are one such gene family under tight regulation during cell division. These genes are most highly expressed during S phase when histones are needed to chromatinize the new DNA template. While this fact has been known for a while, limited knowledge exists about the specific chromatin regulators controlling their temporal expression during cell cycle. Since histones and their associated mutations are emerging as major players in diseases such as cancer, identifying the chromatin factors modulating their expression is critical. The histone lysine tri-demethylase KDM4A is regulated over cell cycle and plays a direct role in DNA replication timing, site-specific rereplication, and DNA amplifications during S phase. Here, we establish an unappreciated role for the catalytically active KDM4A in directly regulating canonical replicative histone gene networks during cell cycle. Of interest, we further demonstrate that KDM4A interacts with proteins controlling histone expression and RNA processing (i.e., hnRNPUL1 and FUS/TLS). Together, this study provides a new function for KDM4A in modulating canonical histone gene expression.

Pediatric high-grade glioma: aberrant epigenetics and kinase signaling define emerging therapeutic opportunities

INTRODUCTION

Supratentorial pediatric high-grade gliomas (pHGGs) are aggressive malignancies that lack effective treatment options. Deep genomic sequencing by multiple groups has revealed that the primary alterations unique to pHGGs occur in epigenetic and kinase genes. These mutations, fusions, and deletions present a therapeutic opportunity by use of small molecules targeting epigenetic modifiers and kinases that contribute to pHGG growth.

METHODS

Using a targeted search of the pre-clinical literature and clinicaltrials.gov for kinase and epigenetic pathways in pHGG, we collectively describe how these mechanisms are being targeted in pre-clinical animal models and in current clinical trials, as well as propose unexplored therapeutic possibilities for future investigations.

RESULTS

Relevant pHGG kinases are targetable by several FDA-approved or clinical-stage kinase inhibitors, including altered BRAF/MET/NTRK/ALK and wild-type PI3K/EGFR/PDGFR/VEGF/AXL. Epigenetic proteins implicated in pHGG are also clinically targetable and include histone erasers, writers and readers such as HDACs, demethylases LSD1/JMJD3, methyltransferase EZH2, chromatin reader bromodomains, and chromatin remodeler subunit BMI-1. Crosstalk between these pathways can occur involving kinases such as EGFR and AMPK interacting with epigenetic modifiers such as HDACs or EZH2. Single agent trial results of kinase inhibitors or epigenetic targets alone are underwhelming and hampered by poor pharmacokinetics, adaptive resistance, and broad inclusion criteria.

CONCLUSIONS

The genetic and phenotypic diversity of pHGGs is now well characterized after large-scale sequencing studies on patient tissue. However, clinical treatment paradigms have not yet shifted in response to this information. Combination therapies targeting multiple kinases or epigenetic targets may hold more promise, especially if attempted in selected patient populations with hemispheric pHGG tumors and relevant targeted therapeutic biomarkers.

Inhibition of Serine Metabolism Promotes Resistance to Cisplatin in Gastric Cancer

Background

Serine provides important precursors of protein, lipid, and nucleotide synthesis needed for tumor cell growth. Phosphoglycerate dehydrogenase (PHGDH), a key rate-limiting enzyme in the serine de novo synthesis pathway, is highly expressed in many tumor types (including gastric cancer) and negatively correlated with overall survival. Cisplatin is a chemotherapeutic drug commonly used in the treatment of gastric cancer. In this study, we mainly investigated the relationship between serine metabolism and resistance to cisplatin in gastric cancer cells, as well as the regulatory mechanism involved in this process.

Materials and Methods

We determined the effect of different concentrations of serine or a PHGDH inhibitor combined with cisplatin or oxaliplatin on the viability and apoptosis of SGC7901, BGC823, and MGC803 cells via the Cell Counting Kit-8 and Hoechst 33258 staining, respectively. Western blotting was utilized to detect the relative protein expression. Furthermore, we investigated DNA damage through the micrococcal nuclease sensitivity assay detected using agarose gels.

Results

We found that reduced concentrations of serine or inhibition of PHGDH hindered the toxicity and pro-apoptotic effects of cisplatin on gastric cancer cells. Moreover, the addition of serine could reverse the sensitivity of gastric cancer cells to cisplatin. Moreover, we found that DNA damage was reduced by treatment with PHGDH inhibitor NCT-503 or CBR-5884. Inhibition of serine metabolism induced a decrease in H3K4 tri-methylation, which was reversed by JIB-04 (inhibitor of H3K4 demethylase). The tolerance of gastric cancer cells to cisplatin was relieved by JIB-04. Through micrococcal nuclease experiments, we further found that inhibiting the activity of PHGDH strengthened chromatin tightness.

Conclusion

Inhibition of serine metabolism reduced H3K4 tri-methylation and increased the density of chromatin, which leads to decreased toxicity and pro-apoptotic effect of platinum chemotherapeutic drugs on gastric cancer cells.

Extrachromosomal DNA-relieving heredity constraints, accelerating tumour evolution

Oncogene amplification on extrachromosomal DNA (ecDNA) provides a mechanism by which cancer cells can rapidly adapt to changes in the tumour microenvironment. These circular structures contain oncogenes and their regulatory elements, and, lacking centromeres, they are subject to unequal segregation during mitosis. This non-Mendelian mechanism of inheritance results in increased tumour heterogeneity with daughter cells that can contain increasingly amplified oncogene copy number. These structures also contain favourable epigenetic modifications including transcriptionally active chromatin, further fuelling positive selection. ecDNA drives aggressive tumour behaviour, is related to poorer survival outcomes and provides mechanisms of drug resistance. Recent evidence suggests one in four solid tumours contain cells with ecDNA structures. The concept of tumour evolution is one in which cancer cells compete to survive in a diverse tumour microenvironment under the Darwinian principles of variation and fitness heritability. Unconstrained by conventional segregation constraints, ecDNA can accelerate intratumoral heterogeneity and cellular fitness. In this review, we highlight some of the recent discoveries underpinning this process.