Modulation of EZH2 Expression by MEK-ERK or PI3K-AKT Signaling in Lung Cancer Is Dictated by Different KRAS Oncogene Mutations

Triple Blockade of Oncogenic RAS Signaling Using KRAS and MEK Inhibitors in Combination with Irradiation in Pancreatic Cancer

Pancreatic ductal adenocarcinoma (PDAC) is one of the deadliest of human malignancies and carries an exceptionally poor prognosis. It is mostly driven by multiple oncogenic alterations, with the highest mutation frequency being observed in the KRAS gene, which is a key oncogenic driver of tumorogenesis and malignant progression in PDAC. However, KRAS remained undruggable for decades until the emergence of G12C mutation specific KRAS inhibitors. Despite this development, this therapeutic approach to target KRAS directly is not routinely used for PDAC patients, with the reasons being the rare presence of G12C mutation in PDAC with only 1-2% of occurring cases, modest therapeutic efficacy, activation of compensatory pathways leading to cell resistance, and absence of effective KRASG12D or pan-KRAS inhibitors. Additionally, indirect approaches to targeting KRAS through upstream and downstream regulators or effectors were also found to be either ineffective or known to cause major toxicities. For this reason, new and more effective treatment strategies that combine different therapeutic modalities aiming at achieving synergism and minimizing intrinsic or adaptive resistance mechanisms are required. In the current work presented here, pancreatic cancer cell lines with oncogenic KRAS G12C, G12D, or wild-type KRAS were treated with specific KRAS or SOS1/2 inhibitors, and therapeutic synergisms with concomitant MEK inhibition and irradiation were systematically evaluated by means of cell viability, 2D-clonogenic, 3D-anchorage independent soft agar, and bioluminescent ATP assays. Underlying pathophysiological mechanisms were examined by using Western blot analyses, apoptosis assay, and RAS activation assay.

A methylation-phosphorylation switch controls EZH2 stability and hematopoiesis

The Polycomb Repressive Complex 2 (PRC2) methylates H3K27 to regulate development and cell fate by transcriptional silencing. Alteration of PRC2 is associated with various cancers. Here, we show that mouse Kdm1a deletion causes a dramatic reduction of PRC2 proteins, whereas mouse null mutation of L3mbtl3 or Dcaf5 results in PRC2 accumulation and increased H3K27 trimethylation. The catalytic subunit of PRC2, EZH2, is methylated at lysine 20 (K20), promoting EZH2 proteolysis by L3MBTL3 and the CLR4DCAF5 ubiquitin ligase. KDM1A (LSD1) demethylates the methylated K20 to stabilize EZH2. K20 methylation is inhibited by AKT-mediated phosphorylation of serine 21 in EZH2. Mouse Ezh2K20R/K20R mutants develop hepatosplenomegaly associated with high GFI1B expression, and Ezh2K20R/K20R mutant bone marrows expand hematopoietic stem cells and downstream hematopoietic populations. Our studies reveal that EZH2 is regulated by methylation-dependent proteolysis, which is negatively controlled by AKT-mediated S21 phosphorylation to establish a methylation-phosphorylation switch to regulate the PRC2 activity and hematopoiesis.

FLT3 tyrosine kinase inhibition modulates PRC2 and promotes differentiation in acute myeloid leukemia

Internal tandem duplication mutations in fms-like tyrosine kinase 3 (FLT3-ITD) are recurrent in acute myeloid leukemia (AML) and increase the risk of relapse. Clinical responses to FLT3 inhibitors (FLT3i) include myeloid differentiation of the FLT3-ITD clone in nearly half of patients through an unknown mechanism. We identified enhancer of zeste homolog 2 (EZH2), a component of polycomb repressive complex 2 (PRC2), as a mediator of this effect using a proteomic-based screen. FLT3i downregulated EZH2 protein expression and PRC2 activity on H3K27me3. FLT3-ITD and loss-of-function mutations in EZH2 are mutually exclusive in human AML. We demonstrated that FLT3i increase myeloid maturation with reduced stem/progenitor cell populations in murine Flt3-ITD AML. Combining EZH1/2 inhibitors with FLT3i increased terminal maturation of leukemic cells and reduced leukemic burden. Our data suggest that reduced EZH2 activity following FLT3 inhibition promotes myeloid differentiation of FLT3-ITD leukemic cells, providing a mechanistic explanation for the clinical observations. These results demonstrate that in addition to its known cell survival and proliferation signaling, FLT3-ITD has a second, previously undefined function to maintain a myeloid stem/progenitor cell state through modulation of PRC2 activity. Our findings support exploring EZH1/2 inhibitors as therapy for FLT3-ITD AML.

Reclassification of RAS/BRAF allele mutations predicts the survival benefit of triplet chemotherapy in metastatic colorectal cancer

Background

Different RAS/BRAF allele mutations imply distinct biological properties in various solid tumors. Recently, several studies have focused on the predictive and prognostic roles of various RAS/BRAF allele mutations in colorectal cancer (CRC) but the results remain controversial.

Methods

Between March 2017 and September 2022, the patients diagnosed as stages I-IV CRC with detailed medical records including next-generation sequencing (NGS) data and clinicopathological follow-up information available at our center were enrolled. Survival data were estimated using the Kaplan-Meier method, and the difference was tested in a log-rank test. Multivariate tests were carried out using Cox models.

Results

A total of 1029 CRC patients were included, and the incidence of RAS/BRAF mutation was 58.4%. The hypermutated cohort was defined as patients with microsatellite instability-H or POLE/D mutation. In the non-hypermutational cohort, only KRAS G13D mutation was associated with a higher incidence and inferior disease-free survival in patients with stage I-III CRC. In the cohort of patients with non-hypermutated metastatic colorectal cancer (mCRC), we assessed the risk of various RAS/BRAF allele mutations and subsequently reclassified patients into four groups based on first-line median progression-free survival: wild type (group 1), low-risk RAS/BRAF mutation (group 2, RAS/BRAF mutations other than KRAS G13D/G12V/G12C or BRAF V600E), high-risk RAS mutation (group 3, KRAS G13D/G12V/G12C), and BRAF V600E mutation (group 4). mCRC patients with high-risk RAS mutation could significantly benefit from intensive triplet chemotherapy (hazard ratio, 2.54; 95% confidence interval, 1.36-5.12; p = 0.0091).

Conclusion

In the non-hypermutated CRC cohort, the prognostic risk of various RAS/BRAF allele mutations varied between local and metastatic CRC. KRAS G13D mutation tended to be the only prognostic marker for stages I-III CRC; however, KRAS G13D/G12V/G12C mutations collectively defined a high-risk subgroup of mCRC patients with poor prognosis, who would benefit from intensive triplet chemotherapy.

EZH2 as a potential therapeutic target for gastrointestinal cancers

Gastrointestinal (GI) cancers continue to be a major cause of mortality and morbidity globally. Understanding the molecular pathways associated with cancer progression and severity is essential for creating effective cancer treatments. In cancer research, there is a notable emphasis on Enhancer of zeste homolog 2 (EZH2), a key player in gene expression influenced by its irregular expression and capacity to attach to promoters and alter methylation status. This review explores the impact of EZH2 signaling on various GI cancers, such as colorectal, gastric, pancreatic, hepatocellular, esophageal, and cholangiocarcinoma. The primary function of EZH2 signaling is to facilitate the accelerated progression of cancer cells. Additionally, EZH2 has the capacity to modulate the reaction of GI cancers to chemotherapy and radiotherapy. Numerous pathways, including long non-coding RNAs and microRNAs, serve as upstream regulators of EZH2 in these types of cancer. EZH2's enzymatic activity enables it to attach to target gene promoters, resulting in methylation that modifies their expression. EZH2 could be considered as an independent prognostic factor, with increased expression correlating with a worse disease prognosis. Additionally, a range of gene therapies including small interfering RNA, and anti-tumor agents are being explored to target EZH2 for cancer treatment. This comprehensive review underscores the current insights into EZH2 signaling in gastrointestinal cancers and examines the prospect of therapies targeting EZH2 to enhance patient outcomes.

MEK/ERK and PI3K/AKT pathway inhibitors affect the transformation of myelodysplastic syndrome into acute myeloid leukemia via H3K27me3 methylases and de‑methylases

The transformation of myelodysplastic syndrome (MDS) into acute myeloid leukemia (AML) poses a significant clinical challenge. The trimethylation of H3 on lysine 27 (H3K27me3) methylase and de‑methylase pathway is involved in the regulation of MDS progression. The present study investigated the functional mechanisms of the MEK/ERK and PI3K/AKT pathways in the MDS‑to‑AML transformation. MDS‑AML mouse and SKM‑1 cell models were first established and this was followed by treatment with the MEK/ERK pathway inhibitor, U0126, the PI3K/AKT pathway inhibitor, Ly294002, or their combination. H3K27me3 methylase, enhancer of zeste homolog (EZH)1, EZH2, demethylase Jumonji domain‑containing protein‑3 (JMJD3) and ubiquitously transcribed tetratricopeptide repeat on chromosome X (UTX) and H3K27me3 protein levels were determined using western blot analysis. Cell viability, cycle distribution and proliferation were assessed using CCK‑8, flow cytometry, EdU and colony formation assays. The ERK and AKT phosphorylation levels in clinical samples and established models were determined, and SKM‑1 cell behaviors were assessed. The levels of H3K27me3 methylases and de‑methylases and distal‑less homeobox 5 (DLX5) were measured. The results revealed that the ERK and AKT phosphorylation levels were elevated in patients with MDS and MDS‑AML, and in mouse models. Treatment with U0126, a MEK/ERK pathway inhibitor, and Ly294002, a PI3K/AKT pathway inhibitor, effectively suppressed ERK and AKT phosphorylation in mice with MDS‑AML. It was observed that mice with MDS treated with U0126/Ly294002 exhibited reduced transformation to AML, delayed disease transformation and increased survival rates. Treatment of the SKM‑1 cells with U0126/Ly294002 led to a decrease in cell viability and proliferation, and to an increase in cell cycle arrest by suppressing ERK/PI3K phosphorylation. Moreover, treatment with U0126/Ly294002 downregulated EZH2/EZH1 expression, and upregulated JMJD3/UTX expression. The effects of U0126/Ly294002 were nullified when EZH2/EZH1 was overexpressed or when JMJD3/UTX was inhibited in the SKM‑1 cells. Treatment with U0126/Ly294002 also resulted in a decreased H3K27me3 protein level and H3K27me3 level in the DLX5 promoter region, leading to an increased DLX5 expression. Overall, the findings of the present study suggest that U0126/Ly294002 participates in MDS‑AML transformation by modulating the levels of H3K27me3 methylases and de‑methylases, and regulating DLX5 transcription and expression.

CDH1 loss promotes diffuse-type gastric cancer tumorigenesis via epigenetic reprogramming and immune evasion

Diffuse-type gastric adenocarcinoma (DGAC) is a deadly cancer often diagnosed late and resistant to treatment. While hereditary DGAC is linked to CDH1 gene mutations, causing E-Cadherin loss, its role in sporadic DGAC is unclear. We discovered CDH1 inactivation in a subset of DGAC patient tumors. Analyzing single-cell transcriptomes in malignant ascites, we identified two DGAC subtypes: DGAC1 (CDH1 loss) and DGAC2 (lacking immune response). DGAC1 displayed distinct molecular signatures, activated DGAC-related pathways, and an abundance of exhausted T cells in ascites. Genetically engineered murine gastric organoids showed that Cdh1 knock-out (KO), KrasG12D, Trp53 KO (EKP) accelerates tumorigenesis with immune evasion compared to KrasG12D, Trp53 KO (KP). We also identified EZH2 as a key mediator promoting CDH1 loss-associated DGAC tumorigenesis. These findings highlight DGAC's molecular diversity and potential for personalized treatment in CDH1-inactivated patients.

Histone methyltransferase enzyme enhancer of zeste homolog 2 counteracts ischemic brain injury via H3K27me3-mediated regulation of PI3K/AKT/mTOR signaling pathway

BACKGROUND

Epigenetic histone methylation plays a crucial role in cerebral ischemic injury, particularly in the context of ischemic stroke. However, the complete understanding of regulators involved in histone methylation, such as Enhancer of Zeste Homolog 2 (EZH2), along with their functional effects and underlying mechanisms, remains incomplete.

METHODS

Here, we employed a rat model of MCAO (Middle cerebral artery occlusion) and an OGD (Oxygen-Glucose Deprivation) model of primary cortical neurons to study the role of EZH2 and H3K27me3 in cerebral ischemia-reperfusion injury. The infarct volume was measured through TTC staining, while cell apoptosis was detected using TUNEL staining. The mRNA expression levels were quantified through quantitative real-time polymerase chain reaction (qPCR), whereas protein expressions were evaluated via western blotting and immunofluorescence experiments.

RESULTS

The expression levels of EZH2 and H3K27me3 were upregulated in OGD; these expression levels were further enhanced by GSK-J4 but reduced by EPZ-6438 and AKT inhibitor (LY294002) under OGD conditions. Similar trends were observed for mTOR, AKT, and PI3K while contrasting results were noted for UTX and JMJD3. The phosphorylation levels of mTOR, AKT, and PI3K were activated by OGD, further stimulated by GSK-J4, but inhibited by EPZ-6438 and AKT inhibitor. Inhibition of EZH2 or AKT effectively counteracted OGD-/MCAO-induced cell apoptosis. Additionally, inhibition of EZH2 or AKT mitigated MCAO-induced infarct size and neurological deficit in vivo.

CONCLUSIONS

Collectively, our results demonstrate that EZH2 inhibition exerts a protective effect against ischemic brain injury by modulating the H3K27me3/PI3K/AKT/mTOR signaling pathway. The results provide novel insights into potential therapeutic mechanisms for stroke treatment.

New insights into the important roles of phase seperation in the targeted therapy of lung cancer

Lung cancer is a complex and heterogeneous disease characterized by abnormal growth and proliferation of lung cells. It is the leading cause of cancer-related deaths worldwide, accounting for approximately 18% of all cancer deaths. In recent years, targeted therapy has emerged as a promising approach to treat lung cancer, which involves the use of drugs that selectively target specific molecules or signaling pathways that are critical for the growth and survival of cancer cells. Liquid-liquid phase separation (LLPS) is a fundamental biological process that occurs when proteins and other biomolecules separate into distinct liquid phases in cells. LLPS is essential for various cellular functions, including the formation of membraneless organelles, the regulation of gene expression, and the response to stress and other stimuli. Recent studies have shown that LLPS plays a crucial role in targeted therapy of lung cancer, including the sequestration of oncogenic proteins and the development of LLPS-based drug delivery systems. Understanding the mechanisms of LLPS in these processes could provide insights into new therapeutic strategies to overcome drug resistance in lung cancer cells.

The roles of EZH2 in cancer and its inhibitors

The enhancer of zeste homolog 2 (EZH2) is encoded by the Enhancer of zeste 2 polycomb repressive complex 2 subunit gene. EZH2 is involved in the cell cycle, DNA damage repair, cell differentiation, autophagy, apoptosis, and immunological modulation. The main function of EZH2 is to catalyze the methylation of H3 histone of H3K27Me3, which inhibits the transcription of target genes, such as tumor suppressor genes. EZH2 also forms complexes with transcriptions factors or directly binds to the promoters of target genes, leading to regulate gene transcriptions. EZH2 has been as a prominent target for cancer therapy and a growing number of potential targeting medicines have been developed. This review summarized the mechanisms that EZH2 regulates gene transcription and the interactions between EZH2 and important intracellular signaling molecules (Wnt, Notch, MEK, Akt) and as well the clinical applications of EZH2-targeted drugs.

The pharmacological and biological importance of EZH2 signaling in lung cancer

Up to 18% of cancer-related deaths worldwide are attributed to lung tumor and global burden of this type of cancer is ascending. Different factors are responsible for development of lung cancer such as smoking, environmental factors and genetic mutations. EZH2 is a vital protein with catalytic activity and belongs to PCR2 family. EZH2 has been implicated in regulating gene expression by binding to promoter of targets. The importance of EZH2 in lung cancer is discussed in current manuscript. Activation of EZH2 significantly elevates the proliferation rate of lung cancer. Furthermore, metastasis and associated molecular mechanisms including EMT undergo activation by EZH2 in enhancing the lung cancer progression. The response of lung cancer to therapy can be significantly diminished due to EZH2 upregulation. Since EZH2 increases tumor progression, anti-cancer agents suppressing its expression reduce malignancy. In spite of significant effort in understanding modulatory function of EZH2 on other pathways, it appears that EZH2 can be also regulated and controlled by other factors that are described in current review. Therefore, translating current findings to clinic can improve treatment and management of lung cancer patients.

Pharmacological inhibition of EZH2 by ZLD1039 suppresses tumor growth and pulmonary metastasis in melanoma cells in vitro and in vivo

The incidence and mortality rate of malignant melanoma are increasing worldwide. Metastasis reduces the efficacy of current melanoma therapies and leads to poor prognosis for patients. EZH2 is a methyltransferase that promotes the proliferation, metastasis, and drug resistance of tumor cells by regulating transcriptional activity. EZH2 inhibitors could be effective in melanoma therapies. Herein, we aimed to investigate whether the pharmacological inhibition of EZH2 by ZLD1039, a potent and selective S-adenosyl-l-methionine-EZH2 inhibitor, suppresses tumor growth and pulmonary metastasis in melanoma cells. Results showed that ZLD1039 selectively reduced H3K27 methylation in melanoma cells by inhibiting EZH2 methyltransferase activity. Additionally, ZLD1039 exerted excellent antiproliferative effects on melanoma cells in 2D and 3D culture systems. Administration of ZLD1039 (100 mg/kg) by oral gavage caused antitumor effects in the A375 subcutaneous xenograft mouse model. RNA sequencing and GSEA revealed that the ZLD1039-treated tumors exhibited changes in the gene sets enriched from the "Cell Cycle" and "Oxidative Phosphorylation", whereas the "ECM receptor interaction" gene set had a negative enrichment score. Mechanistically, ZLD1039 induced G0/G1 phase arrest by upregulating p16 and p27 and inhibiting the functions of the cyclin D1/CDK6 and cyclin E/CDK2 complexes. Moreover, ZLD1039 induced apoptosis in melanoma cells via the mitochondrial reactive oxygen species apoptotic pathway, consistent with the changes in transcriptional signatures. ZLD1039 also exhibited excellent antimetastatic effects on melanoma cells in vitro and in vivo. Our data highlight that ZLD1039 may be effective against melanoma growth and pulmonary metastasis and thus could serve as a therapeutic agent for melanoma.

Digitoxin Affects Metabolism, ROS Production and Proliferation in Pancreatic Cancer Cells Differently Depending on the Cell Phenotype

Digitoxin has repeatedly shown to have negative effects on cancer cell viability; however, the actual mechanism is still unknown. In this study, we investigated the effects of digitoxin (1–100 nM) in four pancreatic cancer cell lines, BxPC-3, CFPAC-1, Panc-1, and AsPC-1. The cell lines differ in their KRAS/BRAF mutational status and primary tumor or metastasis origin. We could detect differences in the basal rates of cell proliferation, glycolysis, and ROS production, giving the cell lines different phenotypes. Digitoxin treatment induced apoptosis in all four cell lines, but to different degrees. Cells derived from primary tumors (Panc-1 and BxPC-3) were highly proliferating with a high proportion of cells in the S/G2 phase, and were more sensitive to digitoxin treatment than the cell lines derived from metastases (CFPAC-1 and AsPC-1), with a high proportion of cells in G0/G1. In addition, the effects of digitoxin on the rate of glycolysis, ROS production, and proliferation were dependent on the basal metabolism and origin of the cells. The KRAS downstream signaling pathways were not altered by digitoxin treatment, thus the effects exerted by digitoxin were probably disconnected from these signaling pathways. We conclude that digitoxin is a promising treatment in highly proliferating pancreatic tumors.

Regulation and Therapeutic Targeting of MTHFD2 and EZH2 in KRAS-Mutated Human Pulmonary Adenocarcinoma

Activating KRAS mutations occur in about 30% of pulmonary adenocarcinoma (AC) cases and the discovery of specific inhibitors of G12C-mutated KRAS has considerably improved the prognosis for a subgroup of about 14% of non-small cell lung cancer (NSCLC) patients. However, even in patients with a KRAS G12C mutation, the overall response rate only reaches about 40% and mutations other than G12C still cannot be targeted. Despite the fact that one-carbon metabolism (1CM) and epigenetic regulation are known to be dysregulated by aberrant KRAS activity, we still lack evidence that co-treatment with drugs that regulate these factors might ameliorate response rates and patient prognosis. In this study, we show a direct dependency of Methylenetetrahydrofolate dehydrogenase 2 (MTHFD2) and Enhancer of Zeste Homolog 2 (EZH2) expression on mutationally activated KRAS and their prognostic relevance in KRAS-mutated AC. We show that aberrant KRAS activity generates a vulnerability of AC cancer cell lines to both MTHFD2 and EZH2 inhibitors. Importantly, co-inhibition of both factors was synergistically effective and comparable to KRASG12C inhibition alone, paving the way for their use in a therapeutic approach for NSCLC cancer patients.

Targeting HSP90 Inhibits Proliferation and Induces Apoptosis Through AKT1/ERK Pathway in Lung Cancer

Lung cancer is one of the most common malignant cancers worldwide. Searching for specific cancer targets and developing efficient therapies with lower toxicity is urgently needed. HPS90 is a key chaperon protein that has multiple client proteins involved in the development of cancer. In this study, we investigated the transcriptional levels of HSP90 isoforms in cancerous and normal tissues of lung cancer patients in multiple datasets. The higher expression of HSP90AA1 in cancer tissues correlated with poorer overall survival was observed. The higher levels of transcription and expression of HSP90AA1 and the activity of AKT1/ERK pathways were confirmed in lung cancer patient tissues. In both human and mouse lung cancer cell lines, knocking down HSP90AA1 promoted cell apoptosis through the inhibition of the pro-survival effect of AKT1 by decreasing the phosphorylation of itself and its downstream factors of mTOR and BAD, as well as downregulating Mcl1, Bcl-xl, and Survivin. The knockdown also suppressed lung cancer cell proliferation by inhibiting ERK activation and downregulating CyclinD1 expression. The treatment of 17-DMAG, an HSP90 inhibitor, recaptured these effects in vitro and inhibited tumor cell growth, and induced apoptosis without obvious side effects in lung tumor xenograft mouse models. This study suggests that targeting HSP90 by 17-DMAG could be a potential therapy for the treatment of lung cancer.

The Cross-Talk between Epigenetic Gene Regulation and Signaling Pathways Regulates Cancer Pathogenesis

Cancer begins due to uncontrolled cell division. Cancer cells are insensitive to the signals that control normal cell proliferation. This uncontrolled cell division is due to the accumulation of abnormalities in different factors associated with the cell division, including different cyclins, cell cycle checkpoint inhibitors, and cellular signaling. Cellular signaling pathways are aberrantly activated in cancer mainly due to epigenetic regulation and post-translational regulation. In this chapter, the role of epigenetic regulation in aberrant activation of PI3K/AKT, Ras, Wnt, Hedgehog, Notch, JAK/STAT, and mTOR signaling pathways in cancer progression is discussed. The role of epigenetic regulators in controlling the upstream regulatory proteins and downstream effector proteins responsible for abnormal cellular signaling-mediated cancer progression is covered in this chapter. Similarly, the role of signaling pathways in controlling epigenetic gene regulation-mediated cancer progression is also discussed. We have tried to ascertain the current status of potential epigenetic drugs targeting several epigenetic regulators to prevent different cancers.

Inhibition of cytoplasmic EZH2 induces antitumor activity through stabilization of the DLC1 tumor suppressor protein

mRNA expression of the DLC1 tumor suppressor gene is downregulated in many lung cancers and their derived cell lines, with DLC1 protein levels being low or absent. Although the role of increased EZH2 methyltransferase in cancer is usually attributed to its histone methylation, we unexpectedly observed that post-translational destabilization of DLC1 protein is common and attributable to its methylation by cytoplasmic EZH2, leading to CUL-4A ubiquitin-dependent proteasomal degradation of DLC1. Furthermore, siRNA knockdown of KRAS in several lines increases DLC1 protein, associated with a drastic reduction in cytoplasmic EZH2. Pharmacologic inhibition of EZH2, CUL-4A, or the proteasome can increase the steady-state level of DLC1 protein, whose tumor suppressor activity is further increased by AKT and/or SRC kinase inhibitors, which reverse the direct phosphorylation of DLC1 by these kinases. These rational drug combinations induce potent tumor growth inhibition, with markers of apoptosis and senescence, that is highly dependent on DLC1 protein.

The molecular mechanisms and therapeutic potential of EZH2 in breast cancer

Due to its high occurrence and mortality rate, breast cancer has been studied from various aspects as one of the cancer field's hot topics in the last decade. Epigenetic alterations are spoused to be highly effective in breast cancer development. Enhancer of zeste homolog 2 (EZH2) is an enzymatic epi-protein that takes part in most vital cell functions by its different action modes. EZH2 is suggested to be dysregulated in specific breast cancer types, particularly in advanced stages. Mounting evidence revealed that EZH2 overexpression or dysfunction affects the pathophysiology of breast cancer. In this review, we discuss biological aspects of the EZH2 molecule with a focus on its newly identified action mechanisms. We also highlight how EZH2 plays an essential role in breast cancer initiation, progression, metastasis, and invasion, which emerged as a worthy target for treating breast cancer in different approaches.

The Pivotal Immunomodulatory and Anti-Inflammatory Effect of Histone-Lysine N-Methyltransferase in the Glioma Microenvironment: Its Biomarker and Therapy Potentials

Enhancer of zeste homolog 2 (EZH2) is a histone-lysine N-methyltransferase that encrypts a member of the Polycomb group (PcG) family. EZH2 forms a repressive chromatin structure which eventually participates in regulating the development as well as lineage propagation of stem cells and glioma progression. Posttranslational modifications are distinct approaches for the adjusted modification of EZH2 in the development of cancer. The amino acid succession of EZH2 protein makes it appropriate for covalent modifications, like phosphorylation, acetylation, O-GlcNAcylation, methylation, ubiquitination, and sumoylation. The glioma microenvironment is a dynamic component that comprises, besides glioma cells and glioma stem cells, a complex network that comprises diverse cell types like endothelial cells, astrocytes, and microglia as well as stromal components, soluble factors, and the extracellular membrane. EZH2 is well recognized as an essential modulator of cell invasion as well as metastasis in glioma. EZH2 oversecretion was implicated in the malfunction of several fundamental signaling pathways like Wnt/β-catenin signaling, Ras and NF-κB signaling, PI3K/AKT signaling, β-adrenergic receptor signaling, and bone morphogenetic protein as well as NOTCH signaling pathways. EZH2 was more secreted in glioblastoma multiforme than in low-grade gliomas as well as extremely secreted in U251 and U87 human glioma cells. Thus, the blockade of EZH2 expression in glioma could be of therapeutic value for patients with glioma. The suppression of EZH2 gene secretion was capable of reversing temozolomide resistance in patients with glioma. EZH2 is a promising therapeutic as well as prognostic biomarker for the treatment of glioma.

Context Matters-Why We Need to Change From a One Size Fits all Approach to Made-to-Measure Therapies for Individual Patients With Pancreatic Cancer

Pancreatic cancer is one of the deadliest cancers and remains a major unsolved health problem. While pancreatic ductal adenocarcinoma (PDAC) is associated with driver mutations in only four major genes (KRAS, TP53, SMAD4, and CDKN2A), every tumor differs in its molecular landscape, histology, and prognosis. It is crucial to understand and consider these differences to be able to tailor treatment regimens specific to the vulnerabilities of the individual tumor to enhance patient outcome. This review focuses on the heterogeneity of pancreatic tumor cells and how in addition to genetic alterations, the subsequent dysregulation of multiple signaling cascades at various levels, epigenetic and metabolic factors contribute to the oncogenesis of PDAC and compensate for each other in driving cancer progression if one is tackled by a therapeutic approach. This implicates that besides the need for new combinatorial therapies for PDAC, a personalized approach for treating this highly complex cancer is required. A strategy that combines both a target-based and phenotypic approach to identify an effective treatment, like Reverse Clinical Engineering® using patient-derived organoids, is discussed as a promising way forward in the field of personalized medicine to tackle this deadly disease.

Going beyond Polycomb: EZH2 functions in prostate cancer

The Polycomb group (PcG) protein Enhancer of Zeste Homolog 2 (EZH2) is one of the three core subunits of the Polycomb Repressive Complex 2 (PRC2). It harbors histone methyltransferase activity (MTase) that specifically catalyze histone 3 lysine 27 (H3K27) methylation on target gene promoters. As such, PRC2 are epigenetic silencers that play important roles in cellular identity and embryonic stem cell maintenance. In the past two decades, mounting evidence supports EZH2 mutations and/or over-expression in a wide array of hematological cancers and solid tumors, including prostate cancer. Further, EZH2 is among the most upregulated genes in neuroendocrine prostate cancers, which become abundant due to the clinical use of high-affinity androgen receptor pathway inhibitors. While numerous studies have reported epigenetic functions of EZH2 that inhibit tumor suppressor genes and promote tumorigenesis, discordance between EZH2 and H3K27 methylation has been reported. Further, enzymatic EZH2 inhibitors have shown limited efficacy in prostate cancer, warranting a more comprehensive understanding of EZH2 functions. Here we first review how canonical functions of EZH2 as a histone MTase are regulated and describe the various mechanisms of PRC2 recruitment to the chromatin. We further outline non-histone substrates of EZH2 and discuss post-translational modifications to EZH2 itself that may affect substrate preference. Lastly, we summarize non-canonical functions of EZH2, beyond its MTase activity and/or PRC2, as a transcriptional cofactor and discuss prospects of its therapeutic targeting in prostate cancer.

PBDEs affect inflammatory and oncosuppressive mechanisms via the EZH2 methyltransferase in airway epithelial cells

AIMS

We aimed to investigate the effect of PBDEs (47, 99, 209) on cellular events involved in epigenetic modification, inflammation, and epithelial mesenchymal transition (EMT).

MATERIALS AND METHODS

We studied: 1) ERK1/2 phosphorylation; 2) Enhancer of Zester Homolog 2 (EZH2); 3) Histone H3 tri-methylated in lysine 27 (H3K27me3); 4) K-RAS; 5) silencing disabled homolog 2-interacting protein gene (DAB2IP), 6) let-7a; 7) Muc5AC/Muc5B, and 8) IL-8 in a 3D in vitro model of epithelium obtained with primary Normal Human Bronchial Epithelial cells (pNHBEs) or A549 cell line, chronically exposed to PBDEs (47, 99, 209).

KEY FINDINGS

PBDEs (10 nM, 100 nM and 1 μM) increased ERK1/2 phosphorylation, and EZH2, H3K27me3, and K-RAS protein expression, while decreased DAB2IP and Let-7a transcripts in pNHBEs ALI culture. Furthermore PBDEs (47, 99) (100 nM) increased Muc5AC and Muc5B mRNA, and PBDE 47 (100 nM) IL-8 mRNA via EZH2 in pNHBEs. Finally, PBDEs (100 nM) affected EZH2, H3K27me3, K-RAS protein expression, and DAB2IP, Let-7a transcripts and cell invasion in A549 cells. Gsk343 (methyltransferase EZH2 inhibitor) (1 mM) and U0126 (inhibitor of MEK1/2) (10 μM) were used to show the specific effect of PBDEs.

SIGNIFICANCE

PBDE inhalation might promote inflammation/cancer via EZH2 methyltransferase activity and H3K27me3, k-RAS and ERk1/2 involvement, generating adverse health outcomes of the human lung.

Myristoylation-mediated phase separation of EZH2 compartmentalizes STAT3 to promote lung cancer growth

N-myristoylation is a crucial signaling and pathogenic modification process that confers hydrophobicity to cytosolic proteins. Although different large-scale approaches have been applied, a large proportion of myristoylated proteins remain to be identified. EZH2 is overexpressed in lung cancer cells and exerts oncogenic effects via its intrinsic methyltransferase activity. Using a well-established click chemistry approach, we found that EZH2 can be modified by myristoylation at its N-terminal glycine in lung cancer cells. Hydrophobic interaction is one of the main forces driving or stabilizing liquid-liquid phase separation (LLPS), raising the possibility that myristoylation can modulate LLPS by mediating hydrophobic interactions. Indeed, myristoylation facilitates EZH2 to form phase-separated liquid droplets in lung cancer cells and in vitro. Furthermore, we provide evidence that myristoylation-mediated LLPS of EZH2 compartmentalizes its non-canonical substrate, STAT3, and activates STAT3 signaling, ultimately resulting in accelerated lung cancer cell growth. Thus, targeting EZH2 myristoylation may have significant therapeutic efficacy in the treatment of lung cancer. Altogether, these observations not only extend the list of myristoylated proteins, but also indicate that hydrophobic lipidation may serve as a novel incentive to induce or maintain LLPS.

HMGA1 induces EZH2 overexpression in human B-cell lymphomas

EZH2 is an enzymatic subunit of PRC2, an epigenetic regulator that triggers the methylation of the histone H3 lysine 27 silencing the transcription of several genes. EZH2 has a critical role in cancer progression, since its overexpression has been associated with increased cancer cell invasiveness, drug resistance and poor patient survival. However, the mechanisms accounting for EZH2 overexpression in cancer remain still unclear. Intriguingly, also HMGA protein overexpression is a feature of many human malignancies and correlates with the presence of metastases and a poor outcome. The HMGA proteins, including HMGA1 and HMGA2, belong to the architectural transcription factors that play a key role in the organization of chromatin structure. Here, we report a statistically significant correlation between HMGA1 and EZH2 expression in human lymphomas. We demonstrate that HMGA1 is able to bind EZH2 promoter and induce its activity. Consistently, silencing of HMGA1 expression results in the downregulation of the EZH2 levels leading to a decreased proliferation and migration rate of human lymphoma cell lines. Therefore, these data identify HMGA1 as an EZH2 activator, suggesting a novel molecular mechanism contributing to EZH2 overexpression in human malignancies and a synergism of these proteins in cancer progression.

Patient-derived xenograft: a developing tool for screening biomarkers and potential therapeutic targets for human esophageal cancers

Esophageal cancer (EC) represents a human malignancy, diagnosed often at the advanced stage of cancer and resulting in high morbidity and mortality. The development of precision medicine allows for the identification of more personalized therapeutic strategies to improve cancer treatment. By implanting primary cancer tissues into immunodeficient mice for expansion, patient-derived xenograft (PDX) models largely maintain similar histological and genetic representations naturally found in patients' tumor cells. PDX models of EC (EC-PDX) provide fine platforms to investigate the tumor microenvironment, tumor genomic heterogeneity, and tumor response to chemoradiotherapy, which are necessary for new drug discovery to combat EC in addition to optimization of current therapeutic strategies for EC. In this review, we summarize the methods used for establishing EC-PDX models and investigate the utilities of EC-PDX in screening predictive biomarkers and potential therapeutic targets. The challenge of this promising research tool is also discussed.

Overcoming Immune Checkpoint Blockade Resistance via EZH2 Inhibition

Recent progress in cancer immunotherapy highlights the power of the immune system to control tumors, although a small patient subset responds to current immunotherapies. Additional approaches to mobilize antitumor immunity are required to overcome primary and acquired resistance to immunotherapy such as immune checkpoint blockade (ICB). Emerging evidence shows that targeting epigenetic elements that promote tumor progression and inhibit immune cell activity can enhance antitumor immunity by reshaping the tumor microenvironment (TME). Here, we review the pleiotropic functions in tumor and immune cells of enhancer of zeste homolog 2 (EZH2), the catalytic subunit of polycomb repressive complex 2 (PRC2), with a focus on EZH2 inhibition as a potentially promising approach to enhance current immunotherapies and improve patient outcomes for certain cancers.

RePhine: An Integrative Method for Identification of Drug Response-related Transcriptional Regulators

Transcriptional regulators (TRs) participate in essential processes in cancer pathogenesis and are critical therapeutic targets. Identification of drug response-related TRs from cell line-based compound screening data is often challenging due to low mRNA abundance of TRs, protein modifications, and other confounders (CFs). In this study, we developed a regression-based pharmacogenomic and ChIP-seq data integration method (RePhine) to infer the impact of TRs on drug response through integrative analyses of pharmacogenomic and ChIP-seq data. RePhine was evaluated in simulation and pharmacogenomic data and was applied to pan-cancer datasets with the goal of biological discovery. In simulation data with added noises or CFs and in pharmacogenomic data, RePhine demonstrated an improved performance in comparison with three commonly used methods (including Pearson correlation analysis, logistic regression model, and gene set enrichment analysis). Utilizing RePhine and Cancer Cell Line Encyclopedia data, we observed that RePhine-derived TR signatures could effectively cluster drugs with different mechanisms of action. RePhine predicted that loss-of-function of EZH2/PRC2 reduces cancer cell sensitivity toward the BRAF inhibitor PLX4720. Experimental validation confirmed that pharmacological EZH2 inhibition increases the resistance of cancer cells to PLX4720 treatment. Our results support that RePhine is a useful tool for inferring drug response-related TRs and for potential therapeutic applications. The source code for RePhine is freely available at https://github.com/coexps/RePhine.

Lysine Methyltransferases Signaling: Histones are Just the Tip of the Iceberg

Protein lysine methylation is a functionally diverse post-translational modification involved in various major cellular processes. Lysine methylation can modulate proteins activity, stability, localization, and/or interaction, resulting in specific downstream signaling and biological outcomes. Lysine methylation is a dynamic and fine-tuned process, deregulation of which often leads to human pathologies. In particular, the lysine methylome and its associated signaling network can be linked to carcinogenesis and cancer progression. Histone modifications and chromatin regulation is a major aspect of lysine methylation importance, but increasing evidence suggests that a high relevance and impact of non-histone lysine methylation signaling has emerged in recent years. In this review, we draw an updated picture of the current scientific knowledge regarding non-histone lysine methylation signaling and its implication in physiological and pathological processes. We aim to demonstrate the significance of lysine methylation as a major and yet underestimated posttranslational modification, and to raise the importance of this modification in both epigenetic and cellular signaling by focusing on the observed activities of SET- and 7β-strandcontaining human lysine methyltransferases. Recent evidence suggests that what has been observed so far regarding lysine methylation's implication in human pathologies is only the tip of the iceberg. Therefore, the exploration of the "methylome network" raises the possibility to use these enzymes and their substrates as promising new therapeutic targets for the development of future epigenetic and methyllysine signaling cancer treatments.

S100A16 promotes metastasis and progression of pancreatic cancer through FGF19-mediated AKT and ERK1/2 pathways

The S100 protein family genes play a crucial role in multiple stages of tumorigenesis and progression. Most of S100 genes are located at chromosome locus 1q21, which is a region frequently rearranged in cancers. Here, we examined the expression of the S100 family genes in paired pancreatic ductal adenocarcinoma (PDAC) samples and further validated the expression of S100A16 by immunohistochemistry staining. We found that S100A16 is significantly upregulated in clinical PDAC samples. However, its roles in PDAC are still unclear. We next demonstrated that S100A16 promotes PDAC cell proliferation, migration, invasion, and metastasis both in vitro and in vivo. Knockdown of S100A16 induces PDAC cell cycle arrest in the G2/M phase and apoptosis. Furthermore, we also demonstrated that S100A16 promotes PDAC cell proliferation, migration, and invasion via AKT and ERK1/2 signaling in a fibroblast growth factor 19 (FGF19)-dependent manner. Taken together, our results reveal that S100A16 is overexpressed in PDAC and promotes PDAC progression through FGF19-mediated AKT and ERK1/2 signaling, suggesting that S100A16 may be a promising therapeutic target for PDAC. S100A16 was upregulated in PDAC and associated with prognosis of PDAC patients. S100A16 regulates apoptosis and the cell cycle of pancreatic cancer cells. S100A16 promotes the progression of pancreatic cancer by AKT-ERK1/2 signaling. S100A16 may be a promising therapeutic target for PDAC.

The effects of mutant Ras proteins on the cell signalome

The genetic alterations in cancer cells are tightly linked to signaling pathway dysregulation. Ras is a key molecule that controls several tumorigenesis-related processes, and mutations in RAS genes often lead to unbiased intensification of signaling networks that fuel cancer progression. In this article, we review recent studies that describe mutant Ras-regulated signaling routes and their cross-talk. In addition to the two main Ras-driven signaling pathways, i.e., the RAF/MEK/ERK and PI3K/AKT/mTOR pathways, we have also collected emerging data showing the importance of Ras in other signaling pathways, including the RAC/PAK, RalGDS/Ral, and PKC/PLC signaling pathways. Moreover, microRNA-regulated Ras-associated signaling pathways are also discussed to highlight the importance of Ras regulation in cancer. Finally, emerging data show that the signal alterations in specific cell types, such as cancer stem cells, could promote cancer development. Therefore, we also cover the up-to-date findings related to Ras-regulated signal transduction in cancer stem cells.

Retrospective study of gene signatures and prognostic value of m6A regulatory factor in non-small cell lung cancer using TCGA database and the verification of FTO

N6-methyladenosine (m6A) is the most common internal modification in eukaryotic mRNA. However, little is known about its role in non-small cell lung cancer (NSCLC). In this study, a total of 1017 NSCLC patients from the cancer genome atlas (TCGA) database with copy number variation (CNV) data were included. Log-rank tests and Cox regression model were used for survival analysis. The relationship between m6A regulators and clinicopathological features was evaluated using the chi-square test. The alteration of m6A regulators were related to T stage. Patients with any CNVs of regulators genes had worse overall survival (OS) than those with diploid genes. The deletion of m6A writer genes was an independent risk factor for poor OS, and the effect synergized with that of copy number gain of eraser genes. High expression of Fat mass-and obesity-associated gene (FTO) was associated with KRAS signaling up. Knockdown of FTO increased m6A content and inhibit proliferation of A549 lung cancer cell. Thus, we identified the genetic changes of m6A regulatory factors in NSCLC for the first time and found a significant relationship between these changes and poor clinical characteristics. FTO might play an important role in promoting NSCLC by decreasing m6A level and activating KRAS signaling.

E2F7-EZH2 axis regulates PTEN/AKT/mTOR signalling and glioblastoma progression

BACKGROUND

E2F transcription factors are considered to be important drivers of tumour growth. E2F7 is an atypical E2F factor, and its role in glioblastoma remains undefined.

METHODS

E2F7 expression was examined in patients by IHC and qRT-PCR. The overall survival probability was determined by statistical analyses. MTT assay, colony formation, cell-cycle assay, cell metastasis and the in vivo model were employed to determine the functional role of E2F7 in glioblastoma. Chromatin immunoprecipitation, luciferase assay and western blot were used to explore the underlying mechanisms.

RESULTS

E2F7 was found to be up-regulated in glioblastoma patients, and high E2F7 expression was associated with poor overall survival in glioblastoma patients. Functional studies showed that E2F7 promoted cell proliferation, cell-cycle progression, cell metastasis and tumorigenicity abilities in vitro and in vivo. E2F7 promoted the transcription of EZH2 by binding to its promoter and increased H3K27me3 level. EZH2 recruited H3K27me3 to the promoter of PTEN and inhibited PTEN expression, and then activated the AKT/mTOR signalling pathway. In addition, restored expression of EZH2 recovered the abilities of cell proliferation and metastasis in E2F7-silencing cells.

CONCLUSION

Collectively, our findings indicate that E2F7 promotes cell proliferation, cell metastasis and tumorigenesis via EZH2-mediated PTEN/AKT/mTOR pathway in glioblastoma.

Genome-wide DNA methylation analysis of KRAS mutant cell lines

Oncogenic RAS mutations are associated with DNA methylation changes that alter gene expression to drive cancer. Recent studies suggest that DNA methylation changes may be stochastic in nature, while other groups propose distinct signaling pathways responsible for aberrant methylation. Better understanding of DNA methylation events associated with oncogenic KRAS expression could enhance therapeutic approaches. Here we analyzed the basal CpG methylation of 11 KRAS-mutant and dependent pancreatic cancer cell lines and observed strikingly similar methylation patterns. KRAS knockdown resulted in unique methylation changes with limited overlap between each cell line. In KRAS-mutant Pa16C pancreatic cancer cells, while KRAS knockdown resulted in over 8,000 differentially methylated (DM) CpGs, treatment with the ERK1/2-selective inhibitor SCH772984 showed less than 40 DM CpGs, suggesting that ERK is not a broadly active driver of KRAS-associated DNA methylation. KRAS G12V overexpression in an isogenic lung model reveals >50,600 DM CpGs compared to non-transformed controls. In lung and pancreatic cells, gene ontology analyses of DM promoters show an enrichment for genes involved in differentiation and development. Taken all together, KRAS-mediated DNA methylation are stochastic and independent of canonical downstream effector signaling. These epigenetically altered genes associated with KRAS expression could represent potential therapeutic targets in KRAS-driven cancer.

High level of EZH2 expression is linked to high density of CD8-positive T-lymphocytes and an aggressive phenotype in renal cell carcinoma

Purpose

Enhancer of zeste homolog 2 (EZH2), the catalytic part of the Polycomb repressive complex 2 (PRC2), has a prognostic role in renal cell carcinoma (RCC) and was recently shown to modulate the immune response by reducing tumor cell immunogenicity.

Methods

To investigate whether the prognostic role of EZH2 might be driven by a modified immune environment, more than 1800 RCCs were analyzed in a tissue microarray for EZH2 expression and CD8 positive lymphocytes were quantitated by automated digital imaging.

Results

EZH2 positivity was found in 75.2% of 1603 interpretable tumors. In clear cell RCC, high EZH2 expression was significantly linked to high ISUP, Furmann, and Thoenes grade (p < 0.0001 each), advanced stage (p < 0.0001), nodal (p = 0.0190) and distant metastasis (p < 0.0001) as well as shortened overall (p < 0.0027) and recurrence free survival (p < 0.0001). The density of CD8+ cells varied from 0 to 5048 cells/mm² (Median 120 cells/mm²). A high CD8+ count was significantly associated with high ISUP, Fuhrmann, and Thoenes grade (p < 0.0001 each), advanced tumor stage (p = 0.0041), distant metastasis (p = 0.0026) as well as reduced overall survival (p = 0.0373) and recurrence free survival (p = 0.0450). The density of CD8+ cells continuously increased with raising EZH2 levels (p < 0.0001).

Conclusion

Our data support a striking prognostic role of both EZH2 expression and the density of CD8+ cells in RCC. The tight relationship of EZH2 expression and CD8+ cell counts in RCC is consistent with models suggesting that EZH2 overexpression can be caused by high lymphocyte content in certain tumor types. Such a mechanism could explain the unique finding of high lymphocyte counts driving poor prognosis in RCC patients.

Dysregulation of SPRR3/miR-876-3p Axis Contributes to Tumorigenesis in Non-Small-Cell Lung Cancer

Background

SPRR3, also known as esophagin, has been shown to be involved in the initiation and progression of numerous types of tumor. However, the biological function of SPRR3 that contributes to non-small-cell lung cancer (NSCLC) growth and migration is largely unknown.

Methods

The expression of SPRR3 and its association with EZH2 and miR-876-3p in NSCLC cells were determined by real-time PCR. Protein levels were measured by immunohistochemistry (IHC) and Western blot. Cell functions were studied by CCK-8, transwell assay, flow cytometry and dual-luciferase reporter assay. The effect of SPRR3 on tumor growth in vivo was evaluated in patient-derived xenograft (PDX) models.

Results

SPRR3 was up-regulated in most NSCLC cell lines and clinical tissues. Also, the correlation between SPRR3 expression and clinical features was significant. Functional studies confirmed that SPRR3 modulates cell proliferation, invasion and cell apoptosis in NSCLC via regulating EZH2, which is a well-known oncogene in NSCLC. Furthermore, SPRR3 was found to be a direct target of miR-876-3p that also plays a suppressor role in NSCLC.

Conclusion

These findings indicated that miR-876-3p/SPRR3/EZH2 signaling cascade exerts important roles in the regulation of NSCLC, suggesting that this pathway can serve as a potential therapeutic target in NSCLC.

lncRNA PVT1 accelerates progression of non-small cell lung cancer via targeting miRNA-526b/EZH2 regulatory loop

Biological function of plasmacytoma variant translocation 1 (PVT1) in influencing the progression of non-small cell lung cancer (NSCLC) through Micro ribonucleic acid (miRNA)-526b/EZH2 regulatory loop was elucidated. Relative levels of PVT1 and miRNA-526b in NSCLC tissues were detected by quantitative real-time polymerase chain reaction (qRT-PCR). Prognostic potential of PVT1 in NSCLC was assessed by Kaplan-Meier curves. The interaction among PVT1/miRNA-526b/EZH2 regulatory loop was confirmed by dual-luciferase reporter gene assay. Regulatory effects of PVT1/miRNA-526b/EZH2 axis on viability and wound closure of A549 cells were evaluated by cell counting kit-8 (CCK-8) and wound closure assay, respectively. PVT1 was upregulated in NSCLC tissues, while miRNA-526b was downregulated. PVT1 level was negatively related to that of miR-526 in NSCLC tissues. Worse survival was seen in NSCLC patients expressing high level of PVT1 compared to those with low level. Knockdown of PVT1 attenuated viability and wound closure ability in A549 cells, which were partially reversed after miRNA-526b knockdown. miRNA-526b is the downstream target of PVT1 and its level was negatively regulated by PVT1. EZH2 is the target gene of miRNA-526b. Transfection of miRNA-526b mimic remarkably downregulated EZH2 in A549 cells. Importantly, the attenuated viability and wound closure ability in A549 cells overexpressing miRNA-526b were reversed after EZH2 overexpression. PVT1 is upregulated in NSCLC, and predicts a poor prognosis. PVT1 accelerates the progression of NSCLC via targeting miRNA-526b/EZH2 regulatory loop.

p53-inducible SESTRINs might play opposite roles in the regulation of early and late stages of lung carcinogenesis

SESTRINs (SESN1-3) are proteins encoded by an evolutionarily conserved gene family that plays an important role in the regulation of cell viability and metabolism in response to stress. Many of the effects of SESTRINs are mediated by negative and positive regulation of mechanistic target of rapamycin kinase complexes 1 and 2 (mTORC1 and mTORC2), respectively, that are often deregulated in human cancers where they support cell growth, proliferation, and cell viability. Besides their effects on regulation of mTORC1/2, SESTRINs also control the accumulation of reactive oxygen species, cell death, and mitophagy. SESN1 and SESN2 are transcriptional targets of tumor suppressor protein p53 and may mediate tumor suppressor activities of p53. Therefore, we conducted studies based on a mouse lung cancer model and human lung adenocarcinoma A549 cells to evaluate the potential impact of SESN1 and SESN2 on lung carcinogenesis. While we observed that expression of SESN1 and SESN2 is often decreased in human tumors, inactivation of Sesn2 in mice positively regulates tumor growth through a mechanism associated with activation of AKT, while knockout of Sesn1 has no additional impact on carcinogenesis in Sesn2-deficient mice. However, inactivation of SESN1 and/or SESN2 in A549 cells accelerates cell proliferation and imparts resistance to cell death in response to glucose starvation. We propose that despite their contribution to early tumor growth, SESTRINs might suppress late stages of carcinogenesis through inhibition of cell proliferation or activation of cell death in conditions of nutrient deficiency.

Akt inhibition synergizes with polycomb repressive complex 2 inhibition in the treatment of multiple myeloma

Polycomb repressive complex 2 (PRC2) components, EZH2 and its homolog EZH1, and PI3K/Akt signaling pathway are focal points as therapeutic targets for multiple myeloma. However, the exact crosstalk between their downstream targets remains unclear. We herein elucidated some epigenetic interactions following Akt inhibition and demonstrated the efficacy of the combined inhibition of Akt and PRC2. We found that TAS-117, a potent and selective Akt inhibitor, downregulated EZH2 expression at the mRNA and protein levels via interference with the Rb-E2F pathway, while EZH1 was compensatively upregulated to maintain H3K27me3 modifications. Consistent with these results, the dual EZH2/EZH1 inhibitor, UNC1999, but not the selective EZH2 inhibitor, GSK126, synergistically enhanced TAS-117-induced cytotoxicity and provoked myeloma cell apoptosis. RNA-seq analysis revealed the activation of the FOXO signaling pathway after TAS-117 treatment. FOXO3/4 mRNA and their downstream targets were upregulated with the enhanced nuclear localization of FOXO3 protein after TAS-117 treatment. ChIP assays confirmed the direct binding of FOXO3 to EZH1 promoter, which was enhanced by TAS-117 treatment. Moreover, FOXO3 knockdown repressed EZH1 expression. Collectively, the present results reveal some molecular interactions between Akt signaling and epigenetic modulators, which emphasize the benefits of targeting PRC2 full activity and the Akt pathway as a therapeutic option for multiple myeloma.

RRAS2 knockdown suppresses osteosarcoma progression by inactivating the MEK/ERK signaling pathway

Aberrant function of RRAS2 drives malignant transformation in a various of cancers. However, little information exists on the function of RRAS2 in tumorigenesis of osteosarcoma. In this study, we investigated the effect of RRAS2 on osteosarcoma progression and its underlying mechanism. The gene expression level and prognostic power of RRAS2 in osteosarcoma were first investigated using the data from the Gene Expression Omnibus database. Then RNA interference was performed to silence the expression of RRAS2 in osteosarcoma cells. Quantitative real-time-PCR and western blot were used to examine the gene and protein expressions of RRAS2 in osteosarcoma cells. In-vitro cancer proliferation and migration were determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolum bromide solution and wound-healing assays, respectively. We found that RRAS2 was significantly upregulated in osteosarcoma cells and high expression of RRAS2 was associated with a poor prognosis for patients with osteosarcoma. RNA interference decreased the gene and protein expression of RRAS2, reduced in-vitro the proliferation and migration of osteosarcoma cells, and suppressed the activation of the MEK/ERK signaling pathway. RRAS2 as an adverse prognostic factor promoted cell proliferation and migration by activating the MEK/ERK signaling pathway, and may provide new therapeutic value for osteosarcoma.

DZNep inhibits Hif-1α and Wnt signalling molecules to attenuate the proliferation and invasion of BGC-823 gastric cancer cells

3-deazaneplanocin A (DZNep) is a histone methyltransferase inhibitor, which may cause the reactivation of silenced tumor suppressor genes in tumors to inhibit the development, metastasis and dissemination of tumor cells. However, the effects and mechanisms of its application in gastric cancer remain unclear. The present study revealed an inhibitory function of DZNep in BGC-823 cells. The cell colony, Cell Counting Kit-8 (CCK8), wound healing, Transwell and flow cytometry assays were performed, and the results demonstrated that DZNep could inhibit the proliferation, apoptosis and invasion of BGC-823 cells, and promote their apoptosis. The effects of intervention in BDC-823 cells with DZNep on the RNA and protein expression levels of hypoxia-inducible factor (Hif-1α) and Wnt/β-catenin signalling molecules were further examined using reverse transcription-quantitative PCR and western blot analysis. The results demonstrated that different concentrations of DZNep could inhibit the expression of enhancer of zeste homolog 2 (EZH2) protein, decrease the RNA and protein expression levels of Hif-1α, total β-catenin and phosphorylated-β-catenin and increase the expression levels of non-phosphorylated-β-catenin to different degrees. The results of the present study suggests that DZNep inhibits BGC-823 gastric cancer cells via the inhibition of EZH2, Hif-1α and Wnt/β-catenin signalling molecules. These results provide theoretical basis for the application of DZNep in clinical trials.

The regulation of NDRG2 expression during ATLL development after HTLV-1 infection

N-myc downstream-regulated gene 2 (NDRG2) is a candidate tumor suppressor that is frequently downregulated in adult T-cell leukemia/lymphoma (ATLL) and functions to negatively regulate several cellular signaling pathways as PP2A recruiter. To clarify the molecular mechanisms of suppression of NDRG2 expression, we initially determined the expression pattern of NDRG2 in various types of T-cells and ATLL cells. NDRG2 expression was significantly upregulated in HTLV-1/Tax-immortalized T-cells, which was mediated by NF-κB activation through Tax expression. On the other hand, NDRG2 expression was suppressed in HTLV-1-infected cell lines and various types of ATLL cells, which was dependent on the DNA methylation of the NDRG2 promoter. We found that the expression of enhancer of zeste homolog 2 (EZH2), a member of the polycomb family, is increased in ATLL, and that EZH2 directly binds to the NDRG2 promoter and induces DNA methylation of the NDRG2 promoter. Since the expression of EZH2 were anti-parallelly regulated with the NDRG2 expression, EZH2 might be one of the most important regulators of the downregulation of NDRG2, contributing to enhanced activation of signaling pathways during ATLL development.

Shortened G1 phase of cell cycle and decreased histone H3K27 methylation are associated with AKT-induced enhancement of primordial germ cell reprogramming

Primordial germ cells (PGCs) are reprogrammed into pluripotent embryonic germ cells (EGCs) under specific culture conditions, but the detailed mechanisms of PGC reprogramming have not yet been fully clarified. Previous studies have demonstrated that AKT, an important intracellular signaling molecule, promotes reprogramming of PGCs into EGCs. Because AKT likely inhibits p53 functions to enhance PGC reprogramming, and p53 negatively regulates cell cycle progression, we analyzed cell cycle changes in PGCs following AKT activation and found that the ratio of PGCs in the G1/G0 phase was decreased while that of PGCs in the G2/M phase was increased after AKT activation. We also showed that the expression of the CDK inhibitor p27kip1, which prevents the G1‐S transition and is transcriptionally activated by p53, was significantly downregulated by AKT activation. The results suggested that the characteristic cell cycle changes of PGCs by AKT activation are, at least in part, due to decreased expression of p27^kip1 . We also investigated changes in histone H3K27 tri-methylation (H3K27me3) by AKT activation in PGCs, because we previously found that decreased H3K27me3 was involved in PGC reprogramming via upregulation of cyclin D1. We observed that AKT activation in PGCs resulted in H3K27 hypomethylation. In addition, DZNeP, an inhibitor of the H3K27 trimethyl transferase Ezh2, stimulated EGC formation. These results together suggested that AKT activation promotes G1-S transition and downregulates H3K27me3 to enhance PGC reprogramming.

Relationship of DNA methylation to mutational changes and transcriptional organization in fusion-positive and fusion-negative rhabdomyosarcoma

Our previous study of DNA methylation in the pediatric soft tissue tumor rhabdomyosarcoma (RMS) demonstrated that fusion-positive (FP) and fusion-negative (FN) RMS tumors exhibit distinct DNA methylation patterns. To further examine the significance of DNA methylation differences in RMS, we investigated genome-wide DNA methylation profiles in discovery and validation cohorts. Unsupervised analysis of DNA methylation data identified novel distinct subsets associated with the specific fusion subtype in FP RMS and with RAS mutation status in FN RMS. Furthermore, the methylation pattern in normal muscle is most similar to the FN subset with wild-type RAS mutation status. Several biologically relevant genes were identified with methylation and expression differences between the two fusion subtypes of FP RMS or between the RAS wild-type and mutant subsets of FN RMS. Genomic localization studies showed that promoter and intergenic regions were hypomethylated and the 3' untranslated regions were hypermethylated in FP compared to FN tumors. There was also a significant difference in the distribution of PAX3-FOXO1 binding sites between genes with and without differential methylation. Moreover, genes with PAX3-FOXO1 binding sites and promoter hypomethylation exhibited the highest frequency of overexpression in FP tumors. Finally, a comparison of RMS model systems revealed that patient-derived xenografts most closely recapitulate the DNA methylation patterns found in human RMS tumors compared to cell lines and cell line-derived xenografts. In conclusion, these findings highlight the interaction of epigenetic changes with mutational alterations and transcriptional organization in RMS tumors, and contribute to improved molecular categorization of these tumors.

Ginsenoside Rg5 induces apoptosis in human esophageal cancer cells through the phosphoinositide‑3 kinase/protein kinase B signaling pathway

The role of ginsenoside in the prevention of cancer has been well established. Ginsenoside Rg5 is one of the main components isolated from red ginseng, which has been demonstrated to have anti-tumor effects by inhibiting cell proliferation and causing DNA damage. However, the role of ginsenoside Rg5 and its molecular mechanisms remain unclear in human esophageal cancer. In the present study, Rg5 was investigated as a novel drug for the chemotherapy of esophageal cancer in in vitro experiments. Esophageal cancer Eca109 cells were exposed to various concentrations of ginsenoside Rg5 (0–32 µΜ) for 24 h. Subsequent cell proliferation assays demonstrated that treatment with ginsenoside Rg5 resulted in the dose-dependent inhibition of proliferation, while a significant increase in apoptotic rate and increased activities of caspase-3, −8 and −9 were observed. In addition, the mitochondrial membrane potential was decreased and the cytoplasmic free calcium level increased following treatment with ginsenoside Rg5. Furthermore, the expression of B-cell lymphoma 2 and phosphorylated-protein kinase B (p-Akt) decreased. The specific phosphoinositide-3 kinase (PI3K) inhibitor LY294002 promoted this effect, while insulin-like growth factor-1, a specific PI3K activator, inhibited this action. Taken together, the results suggested that ginsenoside Rg5 may have a tumor-suppressive effect on esophageal cancer by promoting apoptosis and may be associated with the downregulation of the PI3K/Akt signaling pathway.

Targeting DNA Methylation and EZH2 Activity to Overcome Melanoma Resistance to Immunotherapy

Methylation of DNA at CpG sites is the most common and stable of epigenetic changes in cancer. Hypermethylation acts to limit immune checkpoint blockade immunotherapy by inhibiting endogenous interferon responses needed for recognition of cancer cells. By contrast, global hypomethylation results in the expression of programmed death ligand 1 (PD-L1) and inhibitory cytokines, accompanied by epithelial-mesenchymal changes that can contribute to immunosuppression. The drivers of these contrasting methylation states are not well understood. DNA methylation also plays a key role in cytotoxic T cell 'exhaustion' associated with tumor progression. We present an updated exploratory analysis of how DNA methylation may define patient subgroups and can be targeted to develop tailored treatment combinations to help improve patient outcomes.

Epigenetic silencing of the synthesis of immunosuppressive Siglec ligand glycans by NF-κB/EZH2/YY1 axis in early-stage colon cancers

Normal colonic epithelial cells express sialyl 6-sulfo Lewis^x and disialyl Lewis^a on their cell surface, which are ligands for the immunosuppressive molecule Siglec-7. Expression of these normal glycans is frequently lost upon malignant transformation by silencing DTDST and ST6GalNAc6 at the early stage of colorectal carcinogenesis, and leads to production of inflammatory mediators that facilitate carcinogenesis. Indeed, by querying The Cancer Genome Atlas datasets, we confirmed that the level of DTDST or ST6GalNAc6 mRNA is substantially decreased at the early stage of colorectal carcinogenesis. Cultured colon cancer cell lines were used in this study including DLD-1, HT-29, LS174T and SW620. Their promoter regions were strongly marked by repressive mark H3K27me3, catalyzed by EZH2 that was markedly upregulated in early stage of colorectal carcinogenesis. Suppression of EZH2 substantially downregulated H3K27me3 mark and upregulated DTDST and ST6GalNAc6 as well as expression of normal glycans and Siglec-binding activities. Transcription factor YY1 was vital for the recruitment of PRC2-containing EZH2 to both promoters. Inhibition of NF-κB substantially reduced EZH2 transcription and restored their mRNAs as well as the production of normal Siglec ligand glycans in the results obtained from in vitro studies on cultured colon cancer cell lines. These findings provide a putative mechanism for promotion of carcinogenesis by loss of immunosuppressive molecules by epigenetic silencing through NF-κB-mediated EZH2/YY1 axis.

Targeting the cell signaling pathway Keap1-Nrf2 as a therapeutic strategy for adenocarcinomas of the lung

INTRODUCTION

Kelch-like ECH associated protein 1/Nuclear factor erythroid 2-like factor 2 (Keap1-Nrf2) signaling plays a pivotal role in response to oxidative stress in lung cancer. Mutations in KEAP1/NFE2L2 genes always cause persistent Nrf2 activation in lung cancer cells that confer therapeutic resistance and aggressive tumorigenic activity, dictating either poor prognosis or short duration of response to chemotherapy in clinical observations. Areas covered: We provide a review of the mechanisms underlying the regulation of Keap1-Nrf2 at different stages, including genetic mutations, epigenetic modifications, translational/post-translational alterations, and protein-protein interactions. Based on the current knowledge, we discuss the possibilities of intervening Keap1-Nrf2 in lung adenocarcinoma as a therapeutic target. Expert opinion: It is prevalently conceived that Keap1-Nrf2 signaling plays different roles at diverse stages of cancer. Although various Nrf2 or Keap1 inhibitors have been reported during the last decades, none of these inhibitors are currently under clinical studies or in clinical applications, suggesting that sole inhibition of Nrf2 might not be sufficient to suppress tumor growth. On the basis of current studies, we suggest that the rational combination of Nrf2 suppression with chemical agents which cause enhanced oxidative imbalance or abnormal metabolism would be promising in the treatment of lung adenocarcinoma.