Key actors in cancer therapy: epigenetic modifiers

3-deazaneplanocin A, a histone methyltransferase inhibitor, improved the chemoresistance induced under hypoxia in melanoma cells

One of common characteristics of solid tumors is low O2 level, so-called hypoxia, which plays a critical role in chemoresistance. Epigenetic mechanism such as DNA methylation and histone modification is involved in cancer development and progression. There is ample evidence that epigenetic drugs reversed acquired chemoresistance in cancer cells under normal O2 level, normoxia. However, it remains unknown whether epigenetic drugs improve acquired chemoresistance under hypoxia. The aim of our study was to investigate whether epigenetic drugs can improve the chemoresistance induced under hypoxia in cancer cells. In murine melanoma B16-BL6 (B16) cells, the culture under hypoxia, 1%O2 caused the elevated expression of hypoxia-inducible factor-1α (HIF-1α) and its target genes. The chemoresistance to 7-ethyl-10-hydroxycamptothecin (SN-38, the active metabolite of irinotecan) was also acquired under hypoxia in B16 cells. In addition, as epigenetic mechanisms, the protein expression of the enhancer of zeste homolog 2 (EZH2), histone methyltransferase and its target histone H3 trimethylation at lysine 27 (H3K27Me3) level increased under hypoxia. The induction of H3K27Me3 under hypoxia was suppressed by EZH2 siRNA and 3-deazaneplanocin A (DZNep), an EZH2 inhibitor. Furthermore, both EZH2 siRNA and DZNep significantly reduced the cell viability after SN-38 treatment and improved the chemoresistance to SN-38 under hypoxia. These results indicated that the chemoresistance to SN-38 under hypoxia would arise from epigenetic mechanism, H3K27Me3 elevation due to EZH2 induction. In conclusion, a histone methyltransferase EZH2 inhibitor, DZNep was capable of tackling acquired chemoresistance via the suppression of histone methylation induced under hypoxic tumor microenvironment.

Epigenetic modifiers as game changers for healthy ageing

Epigenetic alterations during ageing are manifested with altered gene expression linking it to lifespan regulation, genetic instability, and diseases. Diet and epigenetic modifiers exert a profound effect on the lifespan of an organism by modulating the epigenetic marks. However, our understanding of the multifactorial nature of the epigenetic process during ageing and the onset of disease conditions as well as its reversal by epidrugs, diet, or environmental factors is still mystifying. This review covers the key findings in epigenetics related to ageing and age-related diseases. Further, it holds a discussion about the epigenetic clocks and their implications in various age-related disease conditions including cancer. Although, epigenetics is a reversible process how fast the epigenetic alterations can revert to normal is an intriguing question. Therefore, this paper touches on the possibility of utilizing nutrition and MSCs secretome to accelerate the epigenetic reversal and emphasizes the identification of new therapeutic epigenetic modifiers to counter epigenetic alteration during ageing.

Integrated bioinformatics analysis reveals CDK1 and PLK1 as potential therapeutic targets of lung adenocarcinoma

ABSTRACT

This study is to identify potential biomarkers and therapeutic targets for lung adenocarcinoma (LUAD).GSE6044 and GSE118370 raw data from the Gene Expression Omnibus database were normalized with Robust Multichip Average. After merging these two datasets, the combat function of sva packages was used to eliminate batch effects. Then, limma packages were used to filtrate differentially expressed genes. We constructed protein-protein interaction relationships using STRING database and hub genes were identified based on connectivity degrees. The cBioportal database was used to explore the alterations of the hub genes. The promoter methylation of cyclin dependent kinase 1 (CDK1) and polo-like Kinase 1 (PLK1) and their association with tumor immune infiltration in patients with LUAD were investigated using DiseaseMeth version 2.0 and TIMER databases. The Cancer Genome Atlas-LUAD dataset was used to perform gene set enrichment analysis.We identified 10 hub genes, which were upregulated in LUAD, among which 8 were successfully verified in the Cancer Genome Atlas and Oncomine databases. Kaplan-Meier analysis indicated that the expressions of CDK1 and PLK1 in LUAD patients were associated with overall survival and disease-free survival. The methylation levels in the promoter regions of these 2 genes in LUAD patients were lower than those in normal lung tissues. Their expressions in LUAD were associated with tumor stages and relative abundance of tumor infiltrating immune cells, such as B cells, CD4+ T cells, and macrophages. Moreover, cell cycle, DNA replication, homologous recombination, mismatch repair, P53 signaling pathway, and small cell lung cancer signaling were significantly enriched in CDK1 and PLK1 high expression phenotype.CDK1 and PLK1 may be used as potential biomarkers and therapeutic targets for LUAD.

When Oxidative Stress Meets Epigenetics: Implications in Cancer Development

Cancer is one of the leading causes of death worldwide and it can affect any part of the organism. It arises as a consequence of the genetic and epigenetic changes that lead to the uncontrolled growth of the cells. The epigenetic machinery can regulate gene expression without altering the DNA sequence, and it comprises methylation of the DNA, histones modifications, and non-coding RNAs. Alterations of these gene-expression regulatory elements can be produced by an imbalance of the intracellular environment, such as the one derived by oxidative stress, to promote cancer development, progression, and resistance to chemotherapeutic treatments. Here we review the current literature on the effect of oxidative stress in the epigenetic machinery, especially over the largely unknown ncRNAs and its consequences toward cancer development and progression.

Loss of HAT1 expression confers BRAFV600E inhibitor resistance to melanoma cells by activating MAPK signaling via IGF1R

BRAF inhibitors (BRAFi) have been approved for the clinical treatment of BRAF-mutant metastatic melanoma. Although initial responses to BRAFi are generally favorable, acquired BRAFi resistance emerges rapidly, resulting in treatment failure. Only some of the underlying mechanisms responsible for BRAFi resistance are currently understood. Here, we showed that the genetic inhibition of histone acetyltransferase 1 (HAT1) in BRAF-mutant melanoma cells resulted in BRAFi resistance. Using quantitative immunofluorescence analysis of patient sample pairs, consisting of pre-treatment along with matched progressed BRAFi + MEKi-treated melanoma samples, HAT1 downregulation was observed in 7/11 progressed samples (~63%) in comparison with pre-treated samples. Employing NanoString-based nCounter PanCancer Pathway Panel-based gene expression analysis, we identified increased MAPK, Ras, transforming growth factor (TGF)-β, and Wnt pathway activation in HAT1 expression inhibited cells. We further found that MAPK pathway activation following the loss of HAT1 expression was partially driven by increased insulin growth factor 1 receptor (IGF1R) signaling. We showed that both MAPK and IGF1R pathway inhibition, using the ERK inhibitor SCH772984 and the IGF1R inhibitor BMS-754807, respectively, restored BRAFi sensitivity in melanoma cells lacking HAT1. Collectively, we show that the loss of HAT1 expression confers acquired BRAFi resistance by activating the MAPK signaling pathway via IGF1R.