Histone variant H3.3 promotes metastasis in alveolar rhabdomyosarcoma

(B)On(e)-cohistones and the epigenetic alterations at the root of bone cancer

Identification of mutations in histones in a number of human neoplasms and developmental syndromes represents the most compelling evidence to date for a causal role of epigenetic perturbations in human disease. In most cases, these mutations have gain of function properties that cause deviation from normal developmental processes leading to embryo defects and/or neoplastic transformation. These exciting discoveries represent a step-change in our understanding of the role of chromatin (dys)regulation in development and disease. However, the mechanisms of action of oncogenic histone mutations (oncohistones) remain only partially understood. Here, we critically assess existing literature on oncohistones focussing mainly on bone neoplasms. We show how it is possible to draw parallels with some of the cell-autonomous mechanisms of action described in paediatric brain cancer, although the functions of oncohistones in bone tumours remain under-investigated. In this respect, it is becoming clear that histone mutations targeting the same residues display, at least in part, tissue-specific oncogenic mechanisms. Furthermore, it is emerging that cancer cells carrying oncohistones can modify the surrounding microenvironment to support growth and/or alter differentiation trajectories. A better understanding of oncohistone function in different neoplasms provide potential for identification of signalling that could be targeted therapeutically. Finally, we discuss some of the main concepts and future directions in this research area, while also drawing possible connections and parallels with other cancer epigenetic mechanisms.

The many faces of H3.3 in regulating chromatin in embryonic stem cells and beyond

H3.3 is a highly conserved nonreplicative histone variant. H3.3 is enriched in promoters and enhancers of active genes, but it is also found within suppressed heterochromatin, mostly around telomeres. Accordingly, H3.3 is associated with seemingly contradicting functions: It is involved in development, differentiation, reprogramming, and cell fate, as well as in heterochromatin formation and maintenance, and the silencing of developmental genes. The emerging view is that different cellular contexts and histone modifications can promote opposing functions for H3.3. Here, we aim to provide an update with a focus on H3.3 functions in early mammalian development, considering the context of embryonic stem cell maintenance and differentiation, to finally conclude with emerging roles in cancer development and cell fate transition and maintenance.

Roles of Histone H2B, H3 and H4 Variants in Cancer Development and Prognosis

Histone variants are the paralogs of core histones (H2A, H2B, H3 and H4). They are stably expressed throughout the cell cycle in a replication-independent fashion and are capable of replacing canonical counterparts under different fundamental biological processes. Variants have been shown to take part in multiple processes, including DNA damage repair, transcriptional regulation and X chromosome inactivation, with some of them even specializing in lineage-specific roles like spermatogenesis. Several reports have recently identified some unprecedented variants from different histone families and exploited their prognostic value in distinct types of cancer. Among the four classes of canonical histones, the H2A family has the greatest number of variants known to date, followed by H2B, H3 and H4. In our prior review, we focused on summarizing all 19 mammalian histone H2A variants. Here in this review, we aim to complete the full summary of the roles of mammalian histone variants from the remaining histone H2B, H3, and H4 families, along with an overview of their roles in cancer biology and their prognostic value in a clinical context.

The Role and Mechanism of the Histone Methyltransferase G9a in Tumors: Update

Methylation-mediated gene silencing is closely related to the occurrence and development of human tumors. The euchromatic histone lysine methyltransferase 2 (EHMT2, also known as G9a) is highly expressed in many tumors and is generally considered to be an oncogene, which is associated with the poor outcome of many tumors. Combined immunotherapy and immune checkpoint blockade therapy also have good efficacy and certain safety. However, there are still many difficulties in the drugs targeting G9a, and the combined effect and safety of G9a with many drugs is still under study. This article aims to summarize the role and mechanism of G9a and its inhibitors in tumors in the past two years, and to understand the application prospect of G9a from the perspective of diagnosis and treatment.

High expression of ACKR1 predicts a good prognosis and suppresses sarcoma cell progression via regulating the tumor immune microenvironment

Sarcoma is a malignant tumor originating from mesenchymal tissue with a poor prognosis. Atypical chemokine receptor 1 (ACKR1) is found closely related to cancer progression. However, the effects of ACKR1 in soft tissue sarcoma have not been well investigated. Therefore, our present study is devoted to analyze the functions of ACKR1 in sarcoma progression and its potential mechanism. We detected the expression of ACKR1 in the Cancer Genome Atlas (TCGA)-pan-cancer database, TCGA-Sarcoma from TCGA databases, and GSE21122 from Gene Expression Omnibus (GEO) database. The relationships between ACKR1 expression, clinicopathological data, and survival status were evaluated in the TCGA-Sarcoma database. Moreover, overexpression negative control (OE-NC) and overexpression ACKR1 (OE-ACKR1) were used to further verify the effects of ACKR1 overexpression in the progression of sarcoma cells by using Reverse Transcription-Quantitative Polymerase Chain Reaction (RT-qPCR), cell counting kit-8 (CCK-8), 5-Ethyny-2'-Deoxyuridine (EdU), wound healing, transwell assay, and flow cytometry assays. Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), and gene set enrichment analysis (GSEA) analyses were carried out to explore the potential enriched biological process of ACKR1 expression in sarcoma. Furthermore, tumor-immune system interactions databases (TISIDB) were applied to further confirm the relations between ACKR1 and tumor immune microenvironment in sarcoma. Our study found that ACKR1 is downregulated in multiple cancers (including sarcoma), and low expression of ACKR1 is related to poor survival status in sarcoma. The biological experiments found that promoting expression of ACKR1 can suppress sarcoma cell proliferation, migration, invasion, promote cell apoptosis, and arrest cell cycle. The GO-KEGG, GSEA, and TISIDB analysis showed that ACKR1 is related to the tumor immune microenvironment. In conclusion, low expression of ACKR1 presented as an independent prognostic biomarker in sarcoma. Overexpression of ACKR1 can significantly suppress cell progression ability in sarcoma by regulating the immune microenvironment.

CP41, a novel curcumin analogue, induces apoptosis in endometrial cancer cells by activating the H3F3A/ proteasome-MAPK signaling pathway and enhancing oxidative stress

AIMS

Curcumin is a natural compound and has good antitumor properties, but its clinical use is limited by its low bioavailability. We constructed the derivative CP41 (3,5-bis(2-chlorobenzylidene)-1-piperidin-4-one) by enhancing the bioavailability of curcumin while retaining its antitumor properties.

MAIN METHODS

CCK-8 (Cell Counting Kit-8) was used to detect the effect of CP41 on cell proliferation; Western blotting, immunofluorescence, immunoprecipitation, quantitative PCR and enzyme-linked immunosorbent assay were used to evaluate the expression of subcutaneous tumor-related molecules in cells and mice.

KEY FINDINGS

Our results showed that CP41 inhibited the proliferation of endometrial cancer cells by suppressing the proliferation of AN3CA and HEC-1-B cells. We found that CP41 significantly increased H3F3A and inhibited proteasome activity, which activated MAPK signaling and led to apoptosis. Further experiments showed that H3F3A is a potential target of CP41. Correlation analysis showed that H3F3A was positively correlated with the sensitivity to chemotherapeutic agents in endometrial cancer. CP41 significantly induced reactive oxygen species (ROS) levels and activated endoplasmic reticulum stress, which led to apoptosis. The safety profile of CP41 was also evaluated, and CP41 did not cause significant drug toxicity in mice.

SIGNIFICANCE

CP41 showed stronger antitumor potency than curcumin, and its antitumor activity may be achieved by inducing ROS and activating H3F3A-mediated apoptosis.

Involvement of the H3.3 Histone Variant in the Epigenetic Regulation of Gene Expression in the Nervous System, in Both Physiological and Pathological Conditions

All the cells of an organism contain the same genome. However, each cell expresses only a minor fraction of its potential and, in particular, the genes encoding the proteins necessary for basal metabolism and the proteins responsible for its specific phenotype. The ability to use only the right and necessary genes involved in specific functions depends on the structural organization of the nuclear chromatin, which in turn depends on the epigenetic history of each cell, which is stored in the form of a collection of DNA and protein modifications. Among these modifications, DNA methylation and many kinds of post-translational modifications of histones play a key role in organizing the complex indexing of usable genes. In addition, non-canonical histone proteins (also known as histone variants), the synthesis of which is not directly linked with DNA replication, are used to mark specific regions of the genome. Here, we will discuss the role of the H3.3 histone variant, with particular attention to its loading into chromatin in the mammalian nervous system, both in physiological and pathological conditions. Indeed, chromatin modifications that mark cell memory seem to be of special importance for the cells involved in the complex processes of learning and memory.