bix-01294 and Carcinoma--Hepatocellular

Dimethylation of the histone H3 protein at lysine residue 9 (H3K9) is mediated by euchromatin histone methyltransferase II (EHMT2) and results in transcriptional repression of target genes. Recently, chemical inhibition of EHMT2 was shown to induce various physiological outcomes, including endoplasmic reticulum stress-associated genes transcription in cancer cells. To identify genes that are transcriptionally repressed by EHMT2 during apoptosis, and cell stress responses, we screened genes that are upregulated by BIX-01294, a chemical inhibitor of EHMT2. RNA sequencing analyses revealed 77 genes that were upregulated by BIX-01294 in all four hepatic cell carcinoma (HCC) cell lines. These included genes that have been implicated in apoptosis, the unfolded protein response (UPR), and others. Among these genes, the one encoding the stress-response protein Ras-related GTPase C (RRAGC) was upregulated in all BIX-01294-treated HCC cell lines. We confirmed the regulatory roles of EHMT2 in RRAGC expression in HCC cell lines using proteomic analyses, chromatin immune precipitation (ChIP) assay, and small guide RNA-mediated loss-of-function experiments. Upregulation of RRAGC was limited by the reactive oxygen species (ROS) scavenger N-acetyl cysteine (NAC), suggesting that ROS are involved in EHMT2-mediated transcriptional regulation of stress-response genes in HCC cells. Finally, combined treatment of cells with BIX-01294 and 5- Aza-cytidine induced greater upregulation of RRAGC protein expression. These findings suggest that EHMT2 suppresses expression of the RRAGC gene in a ROS-dependent manner and imply that EHMT2 is a key regulator of stress-responsive gene expression in liver cancer cells. [BMB Reports 2020; 53(11): 576-581].

Topics: Apoptosis; Azepines; Carcinoma, Hepatocellular; Cell Line, Tumor; Cell Proliferation; Chromatin Immunoprecipitation; Euchromatin; Gene Expression; Gene Expression Regulation; Histocompatibility Antigens; Histone Methyltransferases; Histone-Lysine N-Methyltransferase; Histones; Humans; Liver Neoplasms; Monomeric GTP-Binding Proteins; Proteomics; Quinazolines; Reactive Oxygen Species; Stress, Physiological; Transcriptome

Functional E-cadherin loss, a hallmark of epithelial-mesenchymal transition (EMT), is important for metastasis. However, the mechanism of Snail2 in hepatocellular carcinoma (HCC) EMT and metastasis remains unclear. Here, we showed that Snail2 was upregulated in primary HCC, and significantly increased during transforming growth factor-β-induced liver cell EMT. Snail2-overexpressing and knockdown cell lines have been established to determine its function in EMT in HCC. H3K9 methylation was upregulated and H3K4 and H3K56 acetylation were downregulated at the E-cadherin promoter in Snail2-overexpressing cancer cells. Furthermore, Snail2 interacted with G9a and histone deacetylases (HDACs) to form a complex to suppress E-cadherin transcription. Snail2 overexpression enhanced migration and invasion in HCC cells, whereas G9a and HDAC inhibition significantly reversed this effect. Moreover, Snail2 overexpression in cancer cells increased tumor metastasis and shortened survival time in mice, whereas G9a and HDAC inhibitors extended survival. Our study not only reveals a critical mechanism underlying the epigenetic regulation of EMT but also suggests novel treatment strategies for HCC.

Topics: Acetylation; Animals; Azepines; Cadherins; Carcinoma, Hepatocellular; Cell Movement; Disease Progression; Down-Regulation; Epigenesis, Genetic; Epithelial-Mesenchymal Transition; Female; Histocompatibility Antigens; Histone Deacetylase Inhibitors; Histone Deacetylases; Histone-Lysine N-Methyltransferase; Humans; Hydroxamic Acids; Liver; Liver Neoplasms; Methylation; Mice; Mice, Inbred BALB C; Mice, Nude; Neoplasm Invasiveness; Neoplasm Metastasis; Quinazolines; Snail Family Transcription Factors; Transcription, Genetic; Transforming Growth Factor beta

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a cancer-selective, cell-death-inducing agent with little toxicity to normal cells. However, various human cancers and cancer cell lines have been reported to be resistant to TRAIL. Molecular clarification of resistance mechanism is needed.. Compound screening, proliferation assays, western blotting, and flow cytometry were used to examine the sensitizer activity of methyl transferase inhibitor BIX-01294 in combination with TRAIL, in hepatocellular carcinoma (HCC) cells. RNA sequencing analysis and single guide (sg)RNA-mediated gene deletion were used to investigate the role of survivin in sensitization.. In HCC cells, BIX-01294 enhanced TRAIL sensitivity by reducing survivin expression at the RNA level. Small interference RNA-mediated gene knockdown demonstrated the mechanism of sensitization to be via the reduction of survivin.. Euchromatin histone methyltransferase 2 (EHMT2) inhibition by BIX-01294 may be a potent anti-tumor therapeutic strategy for human HCC.

Topics: Azepines; Carcinoma, Hepatocellular; Cell Line, Tumor; Down-Regulation; Drug Resistance, Neoplasm; Humans; Liver Neoplasms; Quinazolines; Survivin; TNF-Related Apoptosis-Inducing Ligand

Histone H3 lysine 9 dimethylation (H3K9me2) is mainly regulated by the histone lysine methyltransferase G9a and is associated with the repression of transcription. However, both the role of G9a and the significance of H3K9me2 in hepatocellular carcinoma (HCC) cells remain unclear. In this study, we conducted loss-of-function assay of G9a using short-hairpin RNA and pharmacological interference. Knockdown of G9a reduced H3K9me2 levels and impaired both HCC cell growth and sphere formation. However, transforming growth factor β1-induced epithelial mesenchymal transition (EMT) was not suppressed by G9a knockdown. Combined analyses of chromatin immunoprecipitation followed by sequencing and RNA-sequencing led to successful identification of 96 candidate epigenetic targets of G9a. Pharmacological inhibition of G9a by BIX-01294 resulted in both cell growth inhibition and induction of apoptosis in HCC cells. Intraperitoneal administration of BIX-01294 suppressed the growth of xenograft tumors generated by implantation of HCC cells in non-obese diabetic/severe combined immunodeficient mice. Immunohistochemical analyses revealed high levels of G9a and H3K9me2 in 36 (66.7%) and 35 (64.8%) primary HCC tissues, respectively. G9a expression levels were significantly positively correlated with H3K9me2 levels in tumor tissues. In contrast, in non-tumor tissues, G9a and H3K9me2 were only observed in biliary epithelial cells and periportal hepatocytes. In conclusion, G9a inhibition impairs anchorage-dependent and -independent cell growth, but not EMT in HCC cells. Our data indicate that pharmacological interference of G9a might be a novel epigenetic approach for the treatment of HCC.

Topics: Adult; Aged; Aged, 80 and over; Animals; Azepines; Blotting, Western; Carcinoma, Hepatocellular; Chromatin Immunoprecipitation; DNA Methylation; Enzyme Inhibitors; Epigenesis, Genetic; Female; Gene Expression Regulation, Neoplastic; Histocompatibility Antigens; Histone-Lysine N-Methyltransferase; Histones; Humans; Immunohistochemistry; Liver Neoplasms; Male; Mice; Mice, Inbred NOD; Mice, SCID; Middle Aged; Quinazolines; Real-Time Polymerase Chain Reaction; Xenograft Model Antitumor Assays

Hypoxia-inducible factor (HIF) is a key regulator of tumor growth and angiogenesis. Recent studies have shown that, BIX01294, a G9a histone methyltransferase (HMT)-specific inhibitor, induces apoptosis and inhibits the proliferation, migration, and invasion of cancer cells. However, not many studies have investigated whether inhibition of G9a HMT can modulate HIF-1α stability and angiogenesis. Here, we show that BIX01294 dose-dependently decreases levels of HIF-1α in HepG2 human hepatocellular carcinoma cells. The half-life of HIF-1α, expression of proline hydroxylase 2 (PHD2), hydroxylated HIF-1α and von Hippel-Lindau protein (pVHL) under hypoxic conditions were decreased by BIX01294. The mRNA expression and secretion of vascular endothelial growth factor (VEGF) were also significantly reduced by BIX01294 under hypoxic conditions in HepG2 cells. BIX01294 remarkably decreased angiogenic activity induced by VEGF in vitro, ex vivo, and in vivo, as demonstrated by assays using human umbilical vein endothelial cells (HUVECs), mouse aortic rings, and chick chorioallantoic membranes (CAMs), respectively. Furthermore, BIX01294 suppressed VEGF-induced matrix metalloproteinase 2 (MMP2) activity and inhibited VEGF-induced phosphorylation of VEGF receptor 2 (VEGFR-2), focal adhesion kinase (FAK), and paxillin in HUVECs. In addition, BIX01294 inhibited VEGF-induced formation of actin cytoskeletal stress fibers. In conclusion, we demonstrated that BIX01294 inhibits HIF-1α stability and VEGF-induced angiogenesis through the VEGFR-2 signaling pathway and actin cytoskeletal remodeling, indicating a promising approach for developing novel therapeutics to stop tumor progression.

Topics: Animals; Azepines; Carcinoma, Hepatocellular; Chick Embryo; Enzyme Inhibitors; Hep G2 Cells; Histone Methyltransferases; Histone-Lysine N-Methyltransferase; Humans; Hypoxia-Inducible Factor 1, alpha Subunit; Liver Neoplasms; Mice; Neovascularization, Pathologic; Quinazolines; Signal Transduction