Alteration of epigenetic modifications plays an important role in human cancer. Notably, the dysregulation of histone post-translational modifications (PTMs) has been associated with several cancers including colorectal cancer (CRC). However, the signature of histone PTMs on circulating nucleosomes is still not well described. We have developed a fast and robust enrichment method to isolate circulating nucleosomes from plasma for further downstream proteomic analysis. This method enabled us to quantify the global alterations of histone PTMs from 9 CRC patients and 9 healthy donors. Among 54 histone proteoforms identified and quantified in plasma samples, 13 histone PTMs were distinctive in CRC. Notably, methylation of histone H3K9 and H3K27, acetylation of histone H3 and citrullination of histone H2A1R3 were upregulated in plasma of CRC patients. A comparative analysis of paired samples identified 3 common histone PTMs in plasma and tumor tissue including the methylation and acetylation state of lysine 27 of histone H3. Moreover, we highlight for the first time that histone H2A1R3 citrulline is a modification upregulated in CRC patients. This new method presented herein allows the detection and quantification of histone variants and histone PTMs from circulating nucleosomes in plasma samples and could be used for biomarker discovery of cancer.
Michiels (2019) Radiation-induced synthetic lethality: combination of poly(ADP-ribose) polymerase and RAD51 inhibitors to sensitize cells to proton irradiation,
e13534 Background: In liquid biopsy, circulating tumor DNA (ctDNA) is more fragmented than background cell free DNA, peaking at 147bp (equivalent to a mono-nucleosome) instead of 165bp (nucleosome with an additional 20bp of linker DNA). Isolation of these shorter cell free DNA fragments from longer, extracted cell-free DNA improves detection of ctDNA as demonstrated by enrichment of tumor specific mutations. Nuclease protection of the additional 20bp of linker DNA, conferred by bound linker proteins such as Histone 1, would account for the 165bp peak in host background DNA. We hypothesised that extracting intact nucleosomes with linker DNA using a novel, H1 antigen based, immunocapture approach would enrich the ctDNA fraction in the remaining nucleosomes. Methods: We expressed H1.0 protein in E. coli and following extraction, purification and chemically immobilised it to tosyl-activated magnetic beads. The beads were first used to immunodeplete mono-nucleosomes from HeLa cell digests and the level of immunocaptured nucleosomes was determined by immunoassay targeting intact nucleosomes. The level of nucleosome levels determined before and after depletion was further determined by ELISA targeting H3.1 containing intact nucleosomes. DNA was extracted from the H1 immunocaptured “long” nucleosomes and size profiles compared with the remaining nucleosomes in the supernatant by BioAnalyzer. Then, the method was applied to clinical plasma samples and the size distribution of NGS Libraries (Illumina system) prepared from five colorectal cancer and three healthy samples, their immune depleted supernatants and the immunocaptured nucleosomes were then compared. Enrichment of specific genomic regions was also evaluated. Results: We observed relative enrichment of nucleosomes with short DNA in supernatants following H1 immuno-depletion of the cancer samples as evidenced by a change in size distribution by Bioanalyzer and NGS-sequencing. We also observed potential enrichment of TSS is the H1 immunocaptured nucleosomes consistent with linker DNA positioning of TF binding sites. Conclusions: Histone 1.0 has the highest affinity of H1 mammalian isoforms and successfully immunodepleted plasma samples containing cell free circulating nucleosomes with DNA longer that 147bp. Immobilized H1.0 effectively formed a pseudo-chromatosome by binding to free linker DNA or displacing endogenous H1 and other linker associated proteins. H1 antigen based immuno-depletion offers a simple way to enrich tumour derived nucleosomes and thus cell free DNA.
e15032 Background: Non-Hodgkin lymphoma (NHL) is a common type of hematological malignancy. The non-specific symptoms of lymphoma often delay diagnosis that is mainly based on a lymph node biopsy. However, due to their invasive nature, tissue biopsies have many limitations especially for monitoring therapeutic response where multiple biopsies may be required. Conversely, liquid biopsy offers a promising diagnosis and monitoring tool for cancer detection as it is noninvasive and easily repeatable over time compared to tissue biopsy. In this study, we investigated the circulating levels of intact nucleosomes containing the histone H3.1 isoform (Nu.Q-H3.1) in NHL and healthy subjects. Then, as histone post-translational modifications (PTMs) of circulating nucleosomes are described as potential biomarkers of various solid cancers, we investigated the epigenetic profile of nucleosomes from NHL patients following nucleosome enrichment (Nu.Q Capture) combined with mass spectrometry (MS) compared to healthy donors. Methods: In plasma K2EDTA from 9 NHL and 5 healthy subjects, we measured levels of Nu.Q-H3.1 combined with the epigenetic profile of these circulating nucleosomes using our Nu.Q Capture- mass spectrometry protocol. Subsequently, the capability of the identified histone PTMs to differentiate between NHL and healthy plasma was tested in an independent cohort (n = 24 NHL patients and n = 35 healthy donors) and in two patients undergoing treatment course using available quantitative Nu.Q immunoassays. Results: We describe a high level of circulating H3.1-nucleosomes in human plasma NHL patients compared to healthy subjects. This level of H3.1-nucleosomes was correlated with an elevated concentration of cfDNA and is consistent with the DNA distribution size observed by the Bioanalyzer around 146 bp. In addition, the mass spectrometric analysis of the nucleosome enriched extracts allowed us to profile the epigenetic pattern of circulating nucleosomes in NHL patients. Our analysis demonstrated increased levels of H3.1 as well as the lysine acetylation and methylations of the histone H3 in plasma from NHL patients. Furthermore, the clinical validation of the histone PTMs pattern using immunoassays identified a significant increase in the levels of H3.1-nucleosomes as well as 6 histone PTMs (H3K9Me1, H3K27Me3, H3K36Me3, H3K9Ac, H3K14Ac, H3K18Ac) in NHL patients in comparison with healthy donors. Finally, the application of this histone PTMs pattern on NHL patients demonstrated the potential use of these new biomarkers present in liquid biopsy to evaluate the therapeutic response and monitoring of tumor progression. Conclusions: Our results indicate that levels of Nu.Q-H3.1 are particularly elevated in NHL patients and may be a useful diagnostic tool. Moreover, our work emphasizes the crucial roles of the epigenetic marks present on circulating nucleosomes to detect and monitor diseases such as lymphoma.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.