Overexpression of G9a and MCM7 in oesophageal squamous cell carcinoma is associated with poor prognosis

Biomarkers of lymph node metastasis in esophageal cancer

Esophageal cancer (EC) is among the most aggressive malignancies, ranking as the seventh most prevalent malignant tumor worldwide. Lymph node metastasis (LNM) indicates localized spread of cancer and often correlates with a poorer prognosis, emphasizing the necessity for neoadjuvant systemic therapy before surgery. However, accurate identification of LNM in EC presents challenges due to the lack of satisfactory diagnostic techniques. Imaging techniques, including ultrasound and computerized tomography scans, have low sensitivity and accuracy in assessing LNM. Additionally, the existing serological detection lacks precise biomarkers. The intricate and not fully understood molecular processes involved in LNM of EC contribute to current detective limitations. Recent research has shown potential in using various molecules, circulating tumor cells (CTCs), and changes in the microbiota to identify LNM in individuals with EC. Through summarizing potential biomarkers associated with LNM in EC and organizing the underlying mechanisms involved, this review aims to provide insights that facilitate biomarker development, enhance our understanding of the underlying mechanisms, and ultimately address the diagnostic challenges of LNM in clinical practice.

GLP and G9a histone methyltransferases as potential therapeutic targets for lymphoid neoplasms

Histone methyltransferases (HMTs) are enzymes that regulate histone methylation and play an important role in controlling transcription by altering the chromatin structure. Aberrant activation of HMTs has been widely reported in certain types of neoplastic cells. Among them, G9a/EHMT2 and GLP/EHMT1 are crucial for H3K9 methylation, and their dysregulation has been associated with tumor initiation and progression in different types of cancer. More recently, it has been shown that G9a and GLP appear to play a critical role in several lymphoid hematologic malignancies. Importantly, the key roles played by both enzymes in various diseases made them attractive targets for drug development. In fact, in recent years, several groups have tried to develop small molecule inhibitors targeting their epigenetic activities as potential anticancer therapeutic tools. In this review, we discuss the physiological role of GLP and G9a, their oncogenic functions in hematologic malignancies of the lymphoid lineage, and the therapeutic potential of epigenetic drugs targeting G9a/GLP for cancer treatment.

MCM8 promotes lung cancer progression through upregulating DNAJC10

MCM8 is a helicase, which participates in DNA replication and tumorigenesis and is upregulated in many human cancers, including lung cancer (LC); however, the function of MCM8 in LC tumour progression is unclear. In this study, we found that MCM8 was expressed at high levels in LC cells and tissues. Further, MCM8 upregulation was associated with advanced tumour grade and lymph node metastasis, and indicated poor prognosis. Silencing of MCM8 suppressed cell growth and migration in vitro and in vivo, while ectopic MCM8 expression promoted cell cycle progression, as well as cell migration, proliferation, and apoptosis. Mechanistically, DNAJC10 was identified as a downstream target of MCM8, using gene array and CO-IP assays. DNAJC10 overexpression combatted the inhibitory activity of MCM8 knockdown on LC progression, while silencing DNAJC10 alleviated the oncogenic function of MCM8 overexpression. MCM8 expression was positively correlated with that of DNAJC10 in LC samples from The Cancer Genome Atlas database, and DNAJC10 upregulation was also associated with poor overall survival of patients with LC. This study indicated that MCM8/DNAJC10 axis plays an important role in in LC development, and maybe as a new potential therapeutic target or a diagnostic biomarker for treating patients with LC.

Unwinding Helicase MCM Functionality for Diagnosis and Therapeutics of Replication Abnormalities Associated with Cancer: A Review

The minichromosome maintenance (MCM) protein is a component of an active helicase that is essential for the initiation of DNA replication. Dysregulation of MCM functions contribute to abnormal cell proliferation and genomic instability. The interactions of MCM with cellular factors, including Cdc45 and GINS, determine the formation of active helicase and functioning of helicase. The functioning of MCM determines the fate of DNA replication and, thus, genomic integrity. This complex is upregulated in precancerous cells and can act as an important tool for diagnostic applications. The MCM protein complex can be an important broad-spectrum therapeutic target in various cancers. Investigations have supported the potential and applications of MCM in cancer diagnosis and its therapeutics. In this article, we discuss the physiological roles of MCM and its associated factors in DNA replication and cancer pathogenesis.

EHMT2 Suppresses ARRB1 Transcription and Activates the Hedgehog Signaling to Promote Malignant Phenotype and Stem Cell Property in Oral Squamous Cell Carcinoma

Oral squamous cell carcinoma (OSCC) represents the primary subtype of head and neck squamous cell carcinoma (HNSCC), characterized by a high morbidity and mortality rate. Although previous studies have established specific correlations between euchromatic histone lysine methyltransferase 2 (EHMT2), a histone lysine methyltransferase, and the malignant phenotype of OSCC cells, its biological functions in OSCC remain largely unknown. This study, grounded in bioinformatics predictions, aims to clarify the influence of EHMT2 on the malignant behavior of OSCC cells and delve into the underlying mechanisms. EHMT2 exhibited high expression in OSCC tissues and demonstrated an association with poor patient outcomes. Artificial EHMT2 silencing in OSCC cells, achieved through lentiviral vector infection, significantly inhibited colony formation, migration, invasion, and cell survival. Regarding the mechanism, EHMT2 was found to bind the promoter of arrestin beta 1 (ARRB1), thereby suppressing its transcription through H3K9me2 modification. ARRB1, in turn, was identified as a negative regulator of the Hedgehog pathway, leading to a reduction in the proteins GLI1 and PTCH1. Cancer stem cells (CSCs) were enriched through repeated sphere formation assays in two OSCC cell lines. EHMT2 was found to activate the Hedgehog pathway, thus promoting sphere formation, migration and invasion, survival, and tumorigenic activity of the OSCC-CSCs. Notably, these effects were counteracted by the additional overexpression of ARRB1. In conclusion, this study provides novel evidence suggesting that EHMT2 plays specific roles in enhancing stem cell properties in OSCC by modulating the ARRB1-Hedgehog signaling cascade.

Inhibition of the Tumor Suppressor Gene SPINK5 via EHMT2 Induces the Oral Squamous Cell Carcinoma Development

Serine protease inhibitor Kazal-type 5 (SPINK5) has been revealed as a significant prognostic biomarker in oral squamous cell carcinoma (OSCC). However, there is little information regarding the detailed epigenetics mechanism underlying its dysregulation in OSCC. Using the Gene Expression Omnibus database, we identified SPINK5 as a significantly downregulated gene in OSCC tissues. Moreover, SPINK5 inhibited the malignant aggressiveness of HSC3 and squamous cell carcinomas (SCC)9 cells, whereas depletion of SPINK5 using shRNAs led to the opposite trend. The euchromatic histone lysine methyltransferase 2 (EHMT2) was found to bind to the SPINK5 promoter, and EHMT2 repressed the SPINK5 expression. SPINK5 reversed the stimulating effects of EHMT2 on the aggressiveness of HSC3 and SCC9 cells by impairing the Wnt/β-catenin pathway. Wnt/β-catenin inhibitor IWR-1 treatment reverted the malignant phenotype of OSCC cells in the presence of short hairpin RNA (sh)-SPINK5. Silencing of EHMT2 inhibited tumor growth and blocked the Wnt/β-catenin signaling in OSCC, which was reversed by SPINK5 knockdown. Our study shows that SPINK5, mediated by the loss of EHMT2, can inhibit the development of OSCC by inhibiting Wnt/β-catenin signaling and may serve as a treatment target for OSCC.

Tumor-suppressive functions of protein lysine methyltransferases

Protein lysine methyltransferases (PKMTs) play crucial roles in histone and nonhistone modifications, and their dysregulation has been linked to the development and progression of cancer. While the majority of studies have focused on the oncogenic functions of PKMTs, extensive evidence has indicated that these enzymes also play roles in tumor suppression by regulating the stability of p53 and β-catenin, promoting α-tubulin-mediated genomic stability, and regulating the transcription of oncogenes and tumor suppressors. Despite their contradictory roles in tumorigenesis, many PKMTs have been identified as potential therapeutic targets for cancer treatment. However, PKMT inhibitors may have unintended negative effects depending on the specific cancer type and target enzyme. Therefore, this review aims to comprehensively summarize the tumor-suppressive effects of PKMTs and to provide new insights into the development of anticancer drugs targeting PKMTs.

Histone-lysine N-methyltransferase EHMT2 (G9a) inhibition mitigates tumorigenicity in Myc-driven liver cancer

Hepatocellular carcinoma (HCC) is the third deadliest and sixth most common cancer in the world. Histone-lysine N-methyltransferase EHMT2 (also known as G9a) is a histone methyltransferase frequently overexpressed in many cancer types, including HCC. We showed that Myc-driven liver tumours have a unique H3K9 methylation pattern with corresponding G9a overexpression. This phenomenon of increased G9a was further observed in our c-Myc-positive HCC patient-derived xenografts. More importantly, we showed that HCC patients with higher c-Myc and G9a expression levels portend a poorer survival with lower median survival months. We demonstrated that c-Myc interacts with G9a in HCC and cooperates to regulate c-Myc-dependent gene repression. In addition, G9a stabilises c-Myc to promote cancer development, contributing to the growth and invasive capacity in HCC. Furthermore, combination therapy between G9a and synthetic-lethal target of c-Myc, CDK9, demonstrates strong efficacy in patient-derived avatars of Myc-driven HCC. Our work suggests that targeting G9a could prove to be a potential therapeutic avenue for Myc-driven liver cancer. This will increase our understanding of the underlying epigenetic mechanisms of aggressive tumour initiation and lead to improved therapeutic and diagnostic options for Myc-driven hepatic tumours.

Identification of Potential Biomarkers Using Integrative Approach: A Case Study of ESCC

This paper presents a consensus-based approach that incorporates three microarray and three RNA-Seq methods for unbiased and integrative identification of differentially expressed genes (DEGs) as potential biomarkers for critical disease(s). The proposed method performs satisfactorily on two microarray datasets (GSE20347 and GSE23400) and one RNA-Seq dataset (GSE130078) for esophageal squamous cell carcinoma (ESCC). Based on the input dataset, our framework employs specific DE methods to detect DEGs independently. A consensus based function that first considers DEGs common to all three methods for further downstream analysis has been introduced. The consensus function employs other parameters to overcome information loss. Differential co-expression (DCE) and preservation analysis of DEGs facilitates the study of behavioral changes in interactions among DEGs under normal and diseased circumstances. Considering hub genes in biologically relevant modules and most GO and pathway enriched DEGs as candidates for potential biomarkers of ESCC, we perform further validation through biological analysis as well as literature evidence. We have identified 25 DEGs that have strong biological relevance to their respective datasets and have previous literature establishing them as potential biomarkers for ESCC. We have further identified 8 additional DEGs as probable potential biomarkers for ESCC, but recommend further in-depth analysis.

MCM4 is a novel prognostic biomarker and promotes cancer cell growth in glioma

BACKGROUND

Gliomas account for 75% of all primary malignant brain tumors in adults and result in high mortality. Accumulated evidence has declared the minichromosome maintenance protein complex (MCM) gene family plays a critical role in modulating the cell cycle and DNA replication stress. However, the biological function and clinic characterization of nine MCM members in low-grade glioma are not yet clarified.

METHODS

In this study, we utilized diverse public databases, including The Cancer Genome Atlas (TCGA), Chinese Glioma Genome Atlas (CGGA), Rembrandt, Human Protein Atlas (HPA), Linkedomics, cbioportal, Tumor and Immune System Interaction Database (TISIDB), single-sample GSEA (ssGSEA), Tumor Immune Estimation Resource (TIMER), Genomics of Drug Sensitivity in Cancer (GDSC) and Cancer Therapeutics Response Portal databases to explore the mRNA and protein expression profiles, gene mutation, clinical features, diagnosis, prognosis, signaling pathway, tumor mutational burden (TMB), immune subtype, immune cell infiltration, immune modulator and drug sensitivity of nine MCMs. Afterward, qRT-PCR was utilized to detect the expression of the MCM family in glioblastoma multiforme (GBM) cell lines. The one-, three-, or five-year survival rate was predicted by utilizing a nomogram established by cox proportional hazard regression.

RESULTS

In this study, we found that nine MCMs were consistently up-regulated in glioma tissues and glioma cell lines. Elevated nine MCMs expressions were significantly correlated with a higher tumor stage, isocitrate dehydrogenase (IDH) mutates, 1p/19q codeletion, histological type, and primary therapy outcome. Survival analyses showed that higher expression of MCM2-MCM8 (minichromosome maintenance protein2-8) and MCM10 (minichromosome maintenance protein 10) were linked with poor overall survival (OS) and progression-free survival (PFS) in glioma patients. On the other hand, up-regulated MCM2-MCM8 and MCM10 were significantly associated with shorter disease-specific survival (DSS) in glioma patients. Univariate and multivariate analyses revealed that MCM2 (minichromosome maintenance protein2), MCM4 (minichromosome maintenance protein 4), MCM6 (minichromosome maintenance protein 6), MCM7 (minichromosome maintenance protein 7) expression and tumor grade, 1p/19q codeletion, age, and primary therapy outcome were independent factors correlated with the clinical outcome of glioma patients. More importantly, a prognostic MCMs model constructed using the above five prognostic genes could predict the overall survival of glioma patients with medium-to-high accuracy. Furthermore, functional enrichment analysis indicated that MCMs principal participated in regulating cell cycle and DNA replication. DNA copy number variation (CNV) and DNA methylation significantly affect the expression of MCMs. Finally, we uncover that MCMs expression is highly correlated with immune cell infiltration, immune modulator, TMB, and drug sensitivity.

CONCLUSIONS

In summary, this finding confirmed that MCM4 is a potential target of precision therapy for patients with glioma.

Targeting the LSD1-G9a-ER Stress Pathway as a Novel Therapeutic Strategy for Esophageal Squamous Cell Carcinoma

Despite recent advances in the management and treatment of esophageal squamous cell carcinoma (ESCC), the prognosis remains extremely poor, and current nonsurgical treatment options are limited. To identify new therapeutic targets, we screened a curated library of epigenetic compounds using a panel of cancer cell lines and found that coinhibiting the histone demethylase LSD1 and the histone methyltransferase G9a potently suppresses cell growth; similar results were obtained by knocking down both LSD1 and G9a expression. Importantly, we also found that inhibiting LSD1 and G9a significantly decreased tumor growth in a xenograft mouse model with ESCC cell lines. To examine the clinical relevance of these findings, we performed immunohistochemical analyses of microarray profiling data obtained from human esophageal squamous cancer tissues and found that both LSD1 and G9a are upregulated in cancer tissues compared to healthy tissues, and this increased expression was significantly correlated with poor prognosis. Mechanistically, we discovered that inhibiting LSD1 and G9a induces cell death via S-phase arrest and apoptosis, and cotargeting ER stress pathways increased this effect both in vitro and in vivo. Taken together, these findings provide compelling evidence that targeting LSD1, G9a, and ER stress-related pathways may serve as a viable therapeutic strategy for ESCC.

G9a Knockdown Suppresses Cancer Aggressiveness by Facilitating Smad Protein Phosphorylation through Increasing BMP5 Expression in Luminal A Type Breast Cancer

Epigenetic abnormalities affect tumor progression, as well as gene expression and function. Among the diverse epigenetic modulators, the histone methyltransferase G9a has been focused on due to its role in accelerating tumorigenesis and metastasis. Although epigenetic dysregulation is closely related to tumor progression, reports regarding the relationship between G9a and its possible downstream factors regulating breast tumor growth are scarce. Therefore, we aimed to verify the role of G9a and its presumable downstream regulators during malignant progression of breast cancer. G9a-depleted MCF7 and T47D breast cancer cells exhibited suppressed motility, including migration and invasion, and an improved response to ionizing radiation. To identify the possible key factors underlying these effects, microarray analysis was performed, and a TGF-β superfamily member, BMP5, was selected as a prominent target gene. It was found that BMP5 expression was markedly increased by G9a knockdown. Moreover, reduction in the migration/invasion ability of MCF7 and T47D breast cancer cells was induced by BMP5. Interestingly, a G9a-depletion-mediated increase in BMP5 expression induced the phosphorylation of Smad proteins, which are the intracellular signaling mediators of BMP5. Accordingly, we concluded that the observed antitumor effects may be based on the G9a-depletion-mediated increase in BMP5 expression and the consequent facilitation of Smad protein phosphorylation.

Immunohistochemical analysis of proliferating cell nuclear antigen and minichromosome maintenance complex component 7 in benign and malignant salivary gland tumors

Background:

Proliferation markers have been used to determine the behavior and prognosis of benign and malignant tumors; this study was aimed to compare the immunohistochemical (IHC) expression of proliferating cell nuclear antigen (PCNA) and novel marker minichromosome maintenance complex component 7 (MCM7) in common salivary gland tumors including pleomorphic adenoma (PA), mucoepidermoid carcinoma (MEC), and adenoid cystic carcinoma (AdCC), to find a possible significant correlation between benign and malignant tumors.

Materials and Methods:

In this cross-sectional study, a total of 90 cases, including 30 PAs, 30 MECs, and 30 AdCCs, were collected. The IHC expressions of PCNA and MCM7 were evaluated. Their expressions were compared with each other and between benign and malignant tumors. Statistical analysis was performed by Chi-square and Tukey's test. P value was considered 0.05.

Results:

Out of 30 cases of PA, 28 cases (93.3%) were PCNA positive and 28 cases (93.3%) were MCM7 positive. In the AdCC cases, 29 cases (96.6%) were PCNA positive and 29 cases (96.6%) were MCM7 positive. In the MEC cases, all cases (100%) were PCNA positive and 23 cases (76.6%) were MCM7 positive. The labeling index (LI) of MCM7 and PCNA was evaluated, and this index was lower in MCM7 LI than PCNA in all tumors. The MCM7 and PCNA expression showed a significant difference in PA and MEC (P < 0.001).

Conclusion:

PCNA expression was higher than MCM7 expression in salivary gland tumors. However, more studies are needed to evaluate the malignant activity of these tumors with group of markers such as MCM family members.

EHMT1/EHMT2 in EMT, Cancer Stemness and Drug Resistance: Emerging Evidence and Mechanisms

Metastasis, therapy failure and tumor recurrence are major clinical challenges in cancer. The interplay between tumor initiating cells (TICs) and Epithelial-Mesenchymal transition (EMT) drives tumor progression and spread. Recent advances have highlighted the involvement of epigenetic deregulation in these processes. The Euchromatin Histone Lysine Methyltransferase 1 (EHMT1) and Euchromatin Histone Lysine Methyltransferase 2 (EHMT2) that primarily mediate histone 3 lysine 9 di-methylation (H3K9me2), as well as methylation of non-histone proteins, are now recognized to be aberrantly expressed in many cancers. Their deregulated expression is associated with EMT, cellular plasticity and therapy resistance. In this review, we summarize evidence of their myriad roles in cancer metastasis, stemness and drug resistance. We discuss cancer-type specific molecular targets, context-dependent mechanisms and future directions of research in targeting EHMT1/EHMT2 for the treatment of cancer.

MCM7 affects the cisplatin resistance of liver cancer cells and the development of liver cancer by regulating the PI3K/Akt signaling pathway

OBJECTIVE

Aberrant DNA replication is regarded as a component of cancer development. Minichromosome maintenance protein 7 (MCM7), which is critical for the initiation of DNA replication, is overexpressed in multiple malignancies. The effect of MCM7 on cell proliferation, apoptosis, and drug resistance of liver cancer and its mechanism were investigated in this study.

METHODS

MCM7 expression in normal liver cells, liver cancer cell lines, and tissues, as well as adjacent tissues, was determined by qRT-PCR. CCK-8 and flow cytometry was performed to detect cell viability, apoptosis, and cell cycle, respectively. The related mRNA and protein expressions were detected by qRT-PCR and western blot.

RESULTS

High expression of MCM7 was found in liver cancer tissues and cells, which results in notably lower survival time of patients. Cisplatin (DDP) could inhibit cell proliferation and affect MCM7 expression. Silencing of MCM7 inhibited cell viability, promoted cell apoptosis, arrested cell cycle at G1 phase, and enhanced the effect of DDP on cancer cells, while overexpression of MCM7 did the opposite. Moreover, silencing of MCM7 inhibited cyclinD1 and Ki-67 expressions. The overexpression of MCM7 increased phosphorylation levels of PI3K and AKT, activated the PI3K/AKT pathway, and weakened the inhibitory effect of DDP on the PI3K/AKT pathway.

CONCLUSION

Silencing of MCM7 may inhibit cell proliferation and promote apoptosis by regulating the PI3K/AKT pathway to affect the cell cycle, thus affecting the development of liver cancer, and improving the sensitivity of liver cancer cells to DDP.

EHMT2/G9a as an Epigenetic Target in Pediatric and Adult Brain Tumors

Epigenetic mechanisms, including post-translational modifications of DNA and histones that influence chromatin structure, regulate gene expression during normal development and are also involved in carcinogenesis and cancer progression. The histone methyltransferase G9a (euchromatic histone lysine methyltransferase 2, EHMT2), which mostly mediates mono- and dimethylation by histone H3 lysine 9 (H3K9), influences gene expression involved in embryonic development and tissue differentiation. Overexpression of G9a has been observed in several cancer types, and different classes of G9a inhibitors have been developed as potential anticancer agents. Here, we review the emerging evidence suggesting the involvement of changes in G9a activity in brain tumors, namely glioblastoma (GBM), the main type of primary malignant brain cancer in adults, and medulloblastoma (MB), the most common type of malignant brain cancer in children. We also discuss the role of G9a in neuroblastoma (NB) and the drug development of G9a inhibitors.

Structure, Activity, and Function of the Protein Lysine Methyltransferase G9a

G9a is a lysine methyltransferase catalyzing the majority of histone H3 mono- and dimethylation at Lys-9 (H3K9), responsible for transcriptional repression events in euchromatin. G9a has been shown to methylate various lysine residues of non-histone proteins and acts as a coactivator for several transcription factors. This review will provide an overview of the structural features of G9a and its paralog called G9a-like protein (GLP), explore the biochemical features of G9a, and describe its post-translational modifications and the specific inhibitors available to target its catalytic activity. Aside from its role on histone substrates, the review will highlight some non-histone targets of G9a, in order gain insight into their role in specific cellular mechanisms. Indeed, G9a was largely described to be involved in embryonic development, hypoxia, and DNA repair. Finally, the involvement of G9a in cancer biology will be presented.

Computational Screening of Natural Compounds for Identification of Potential Anti-Cancer Agents Targeting MCM7 Protein

Minichromosome maintenance complex component 7 (MCM7) is involved in replicative licensing and the synthesis of DNA, and its overexpression is a fascinating biomarker for various cancer types. There is currently no effective agent that can prevent the development of cancer caused by the MCM7 protein. However, on the molecular level, inhibiting MCM7 lowers cancer-related cellular growth. With this purpose, this study screened 452 biogenic compounds extracted from the UEFS Natural Products dataset against MCM protein by using the in silico art of technique. The hit compounds UEFS99, UEFS137, and UEFS428 showed good binding with the MCM7 protein with binding energy values of −9.95, −8.92, and −8.71 kcal/mol, which was comparatively higher than that of the control compound ciprofloxacin (−6.50). The hit (UEFS99) with the minimum binding energy was picked for molecular dynamics (MD) simulation investigation, and it demonstrated stability at 30 ns. Computational prediction of physicochemical property evaluation revealed that these hits are non-toxic and have good drug-likeness features. It is suggested that hit compounds UEFS99, UEFS137, and UEFS428 pave the way for further bench work validation in novel inhibitor development against MCM7 to fight the cancers.

Downregulation of MCM8 expression restrains the malignant progression of cholangiocarcinoma

Cholangiocarcinoma (CCA) is a highly aggressive malignant tumor with an extremely poor prognosis. Minichromosome maintenance 8 homologous recombination repair factor (MCM8) is a helicase involved in the elongation step of DNA replication and tumorigenesis. In the present study, the clinical significance and biological function of MCM8 in CCA were investigated. The expression levels of MCM8 in CCA and paracancerous tissues were analyzed using immunohistochemical staining. The potential mechanisms underlying MCM8 and the biological effects of MCM8 in CCA cells were explored using in vitro assays and in vivo mouse xenograft models. The high expression levels of MCM8 in CCA has important clinical significance in predicting disease progression. Knockdown of MCM8 decreased proliferation, promoted apoptosis and suppressed migration of CCA cells. MCM8 knockdown also suppressed tumor growth in vivo. Mechanistically, MCM8 knockdown led to the abnormal downregulation of survivin, XIAP, HSP27, IGF‑1sR, sTNF‑R1, sTNF‑R2, TNF‑α and TNF‑β. Furthermore, downregulation of MCM8 expression inhibited the PI3K/Akt signaling pathway and induced the MAPK9 signaling pathway. MCM8 promoted the malignant progression of CCA, indicating that inhibition of MCM8 may have the potential to serve as a novel molecular targeted therapy.

KDM1A and KDM3A promote tumor growth by upregulating cell cycle-associated genes in pancreatic cancer

Pancreatic cancer is a highly malignant cancer of the pancreas with a very poor prognosis. Methylation of histone lysine residues is essential for regulating cancer physiology and pathophysiology, mediated by a set of methyltransferases (KMTs) and demethylases (KDMs). This study surveyed the expression of methylation regulators functioning at lysine 9 of histone 3 (H3K9) in pancreatic lesions and explored the underlying mechanisms. We analyzed KDM1A and KDM3A expression in clinical samples by immunohistochemical staining and searching the TCGA PAAD program and GEO datasets. Next, we identified the variation in tumor growth in vitro and in vivo after knockdown of KDM1A or KDM3A and explored the downstream regulators of KDM1A and KDM3A via RNA-seq, and gain- and loss-of-function assays. Eleven H3K9 methylation regulators were highly expressed in pancreatic cancer, and only KDM1A and KDM3A expression positively correlated with the clinicopathological characteristics in pancreatic cancer. High expression of KDM1A or KDM3A positively correlated with pathological grade, lymphatic metastasis, invasion, and clinical stage. Kaplan-Meier analysis indicated that a higher level of KDM1A or KDM3A led to a shorter survival period. Knockdown of KDM1A or KDM3A led to markedly impaired tumor growth in vitro and in vivo. Mechanistically, CCNA2, a cell cycle-associated gene was partially responsible for KDM1A knockdown-mediated effect and CDK6, also a cell cycle-associated gene was partially responsible for KDM3A knockdown-mediated effect on pancreatic cancer cells. Our study demonstrates that KDM1A and KDM3A are highly expressed in pancreatic cancer and are intimately correlated with clinicopathological factors and prognosis. The mechanism of action of KDM1A or KDM3A was both linked to the regulation of cell cycle-associated genes, such as CCNA2 or CDK6, respectively, by an H3K9-dependent pathway.

Multi-Dimensional Scaling Analysis of Key Regulatory Genes in Prostate Cancer Using the TCGA Database

Prostate cancer (PC) is a polygenic disease with multiple gene interactions. Therefore, a detailed analysis of its epidemiology and evaluation of risk factors can help to identify more accurate predictors of aggressive disease. We used the transcriptome data from a cohort of 243 patients from the Cancer Genome Atlas (TCGA) database. Key regulatory genes involved in proliferation activity, in the regulation of stress, and in the regulation of inflammation processes of the tumor microenvironment were selected to test a priori multi-dimensional scaling (MDS) models and create a combined score to better predict the patients' survival and disease-free intervals. Survival was positively correlated with cortisol expression and negatively with Mini-Chromosome Maintenance 7 (MCM7) and Breast-Related Cancer Antigen2 (BRCA2) expression. The disease-free interval was negatively related to the expression of enhancer of zeste homolog 2 (EZH2), MCM7, BRCA2, and programmed cell death 1 ligand 1 (PD-L1). MDS suggested two separate pathways of activation in PC. Within these two dimensions three separate clusters emerged: (1) cortisol and brain-derived neurotrophic factor BDNF, (2) PD-L1 and cytotoxic-T-lymphocyte-associated protein 4 (CTL4); (3) and finally EZH2, MCM7, BRCA2, and c-Myc. We entered the three clusters of association shown in the MDS in several Kaplan-Meier analyses. It was found that only Cluster 3 was significantly related to the interval-disease free, indicating that patients with an overall higher activity of regulatory genes of proliferation and DNA repair had a lower probability to have a longer disease-free time. In conclusion, our data study provided initial evidence that selecting patients with a high grade of proliferation and DNA repair activity could lead to an early identification of an aggressive PC with a potentials for metastatic development.

Research progress of dual inhibitors targeting crosstalk between histone epigenetic modulators for cancer therapy

Abnormal epigenetics is a critical hallmark of human cancers. Anticancer drug discovery directed at histone epigenetic modulators has gained impressive advances with six drugs available for cancer therapy and numerous other candidates undergoing clinical trials. However, limited therapeutic profile, drug resistance, narrow safety margin, and dose-limiting toxicities pose intractable challenges for their clinical utility. Because histone epigenetic modulators undergo intricate crosstalk and act cooperatively to shape an aberrant epigenetic profile, co-targeting histone epigenetic modulators with a different mechanism of action has rapidly emerged as an attractive strategy to overcome the limitations faced by the single-target epigenetic inhibitors. In this review, we summarize in detail the crosstalk of histone epigenetic modulators in regulating gene transcription and the progress of dual epigenetic inhibitors targeting this crosstalk.

miR-107 regulates the effect of MCM7 on the proliferation and apoptosis of colorectal cancer via the PAK2 pathway

Microchromosome maintenance protein 7 (MCM7), a DNA replication permitting factor, plays an essential role in initiating DNA replication. MCM7 is reported to be involved in tumor formation and progression, whereas the expression profile and molecular function of MCM7 in colorectal cancer (CRC) remain unknown. In this study, we aimed to evaluate the clinical significance and biological function of MCM7 in CRC and investigated whether MCM7 can be used for a differential diagnosis in CRC and whether it may serve as a more sensitive proliferation marker for CRC evaluation. Moreover, immunohistochemical analysis of MCM7 was performed in a total of 89 specimens, and high MCM7 expression levels were associated with worse overall survival (OS) in CRC patients. Furthermore, the cell functional test suggested that lentivirus-mediated silencing of MCM7 with shRNA in CRC cells significantly inhibited cellular proliferation and promoted apoptosis in vitro and inhibited tumor growth in vivo. Additionally, mechanistic studies further demonstrated that P21-activated protein kinase 2 (PAK2) was regulated by MCM7 via microarray analysis and cell functional recovery tests, and miR-107 played a role in regulating expression MCM7 via miRNA microarray analysis and 3'UTR reporter assays. Taken together, our results suggest that the miR-107/MCM7/PAK2 pathway may participate in cancer progression and that MCM7 may serve as a prognostic biomarker in CRC.

Knockdown of MCM8 inhibits development and progression of bladder cancer in vitro and in vivo

BACKGROUND

Bladder cancer is a frequently diagnosed urinary system tumor, whose mortality remains rising. Minichromosome maintenance eight homologous recombination repair factor (MCM8), a newly discovered MCM family member, has been shown to be required for DNA replication. Unfortunately, little is known concerning the roles of MCM8 in bladder cancer.

METHODS

The present study, we aimed at probing into the impacts and detailed mechanisms of MCM8 in bladder cancer progression. In this study, MCM8 expression level was detected through immunohistochemistry staining (IHC), qRT-PCR and Western blot assay. Silenced MCM8 cell models were constructed by lentivirus transfection. In vitro, the cell proliferation was evaluated by the MTT assay. The wound-healing assay and the transwell assay were utilized to assess the cell migration. Also, the cell apoptosis and the cell cycle were determined by flow cytometry. Moreover, the Human Apoptosis Antibody Array assay was performed to analyze the alterations of apoptosis-related proteins. The in vivo experiments were conducted to verify the effects of MCM8 knockdown on the tumor growth of bladder cancer.

RESULTS

The results demonstrated that compared with normal adjacent tissues, MCM8 expression in bladder cancer tissues was strongly up-regulated. The up-regulation of MCM8 expression in bladder cancer may be a valuable independent prognostic indicator. Of note, MCM8 inhibition modulated the malignant phenotypes of bladder cancer cells. In terms of mechanism, it was validated that MCM8 knockdown made Akt, P-Akt, CCND1 and CDK6 levels down-regulated, as well as MAPK9 up-regulated.

CONCLUSIONS

Taken together, our study demonstrated an important role of MCM8 in bladder cancer and created a rationale for the therapeutic potential of MCM8 inhibition in human bladder cancer therapy.

EHMT2 inhibitor BIX-01294 induces endoplasmic reticulum stress mediated apoptosis and autophagy in diffuse large B-cell lymphoma cells

Despite advancement in the treatment of diffuse large B-cell lymphoma (DLBCL), many patients tend to relapse or become refractory after initial therapy. Therefore, it is essential to identify novel therapeutic targets and drugs, understand the molecular pathogenesis mechanism of DLBCL, and find ways to prevent and treat relapsed or refractory DLBCL. BIX-01294 is a small molecule compound that specifically inhibits EHMT2 activity. In this study, we demonstrate that BIX-01294 triggered the inhibition of human DLBCL cell proliferation, lead to G₁ phase arrest via increasing P21 level and reducing cyclin E level. BIX-01294 also induced apoptosis via endogenous and exogenous apoptotic pathways. Moreover, BIX-01294 triggered autophagy and activated ER stress in human DLBCL cells. Furthermore, we showed that both key components of ER stress, ATF3, and ATF4, are required for BIX-01294-induced apoptosis and autophagy. Hence, this study provides new evidence that EHMT2 may be a new therapeutic target, and BIX-01294 may be a potential therapeutic drug for treating DLBCL.

Identification of mini-chromosome maintenance 8 as a potential prognostic marker and its effects on proliferation and apoptosis in gastric cancer

Mini‐chromosome maintenance (MCM) proteins play important roles in initiating eukaryotic genome replication. The MCM family of proteins includes several members associated with the development and progression of certain cancers. We performed online data mining to assess the expression of MCMs in gastric cancer (GC) and the correlation between their expression and survival in patients with GC. Notably, MCM8 expression was undoubtedly up‐regulated in GC, and higher expression correlated with shorter overall survival (OS) and progression‐free survival (PFS) in patients with GC. However, the role of MCM8 in GC has not been previously explored. Our in vitro experiments revealed that MCM8 knockdown inhibited cell growth and metastasis. Moreover, MCM8 knockdown induced apoptosis. Mechanistically, the expression levels of Bax and cleaved caspase‐3 were increased, whereas Bcl‐2 expression decreased. Additionally, we demonstrated that MCM8 knockdown suppressed tumorigenesis in vivo. Overall, these results suggest that MCM8 plays a significant role in GC progression.

A New Computational Approach to Evaluating Systemic Gene–Gene Interactions in a Pathway Affected by Drug LY294002

In this study, we investigate how drugs systemically affect genes via pathways by integrating information from interactions between chemical compounds and molecular expression datasets, and from pathway information such as gene sets using mathematical models. First, we adopt drug-induced gene expression datasets; then, employ gene set enrichment analysis tools for selecting candidate enrichment pathways; and lastly, implement the inverse algorithm package for identifying gene–gene regulatory networks in a pathway. We tested LY294002-induced datasets of the MCF7 breast cancer cell lines, and found a CELL CYCLE pathway with 101 genes, ERBB signaling pathway consisting of 82 genes, and MTOR pathway consisting of 45 genes. We consider two interactions: quantity strength depending on number of interactions, and quality strength depending on weight of interaction as positive (+) and negative (−) interactions. Our methods revealed ANAPC1-CDK6 (−0.412) and ORC2L- CHEK1(0.951) for the CELL CYCLE pathway; INS-RPS6 (−3.125) and PRKAA2-PRKAA2 (+1.319) for the MTOR pathway; and CBLB-RPS6KB1 (−0.141), RPS6KB1-CBLC (+0.238) for the ERBB signaling pathway to be top quality interactions. Top quantity interactions discovered include 12; the CDC (−,+) gene family for the CELL CYCLE pathway, 20; PIK3 (−), 23; PIK3CG (+) for the MTOR pathway, 11; PAK (−), 10; PIK3 (+) for the ERBB signaling pathway.

MCM family in gastrointestinal cancer and other malignancies: From functional characterization to clinical implication

Despite the recent advances in cancer research and treatment, gastrointestinal (GI) cancers remain the most common deadly disease worldwide. The aberrant DNA replication serves as a major source of genomic instability and enhances cell proliferation that contributes to tumor initiation and progression. Minichromosome maintenance family (MCMs) is a well-recognized group of proteins responsible for DNA synthesis. Recent studies suggested that dysregulated MCMs lead to tumor initiation, progression, and chemoresistance via modulating cell cycle and DNA replication stress. Their underlying mechanisms in various cancer types have been gradually identified. Furthermore, multiple studies have investigated the association between MCMs expression and clinicopathological features of cancer patients, implying that MCMs might serve as prominent prognostic biomarkers for GI cancers. This review summarizes the current knowledge on the oncogenic role of MCM proteins and highlights their clinical implications in various malignancies, especially in GI cancers. Targeting MCMs might shed light on the potential for identifying novel therapeutic strategies.

DNA Methyltransferases in Cancer: Biology, Paradox, Aberrations, and Targeted Therapy

DNA methyltransferases are an essential class of modifiers in epigenetics. In mammals, DNMT1, DNMT3A and DNMT3B participate in DNA methylation to regulate normal biological functions, such as embryo development, cell differentiation and gene transcription. Aberrant functions of DNMTs are frequently associated with tumorigenesis. DNMT aberrations usually affect tumor-related factors, such as hypermethylated suppressor genes and genomic instability, which increase the malignancy of tumors, worsen the prognosis for patients, and greatly increase the difficulty of cancer therapy. However, the impact of DNMTs on tumors is still controversial, and therapeutic approaches targeting DNMTs are still under exploration. Here, we summarize the biological functions and paradoxes associated with DNMTs and we discuss some emerging strategies for targeting DNMTs in tumors, which may provide novel ideas for cancer therapy.

Epigenetic Alterations in Oesophageal Cancer: Expression and Role of the Involved Enzymes

Oesophageal cancer is a life-threatening disease, accounting for high mortality rates. The poor prognosis of this malignancy is mostly due to late diagnosis and lack of effective therapies for advanced disease. Epigenetic alterations may constitute novel and attractive therapeutic targets, owing to their ubiquity in cancer and their reversible nature. Herein, we offer an overview of the most important studies which compared differences in expression of enzymes that mediate epigenetic alterations between oesophageal cancer and normal mucosa, as well as in vitro data addressing the role of these genes/proteins in oesophageal cancer. Furthermore, The Cancer Genome Atlas database was interrogated for the correlation between expression of these epigenetic markers and standard clinicopathological features. We concluded that most epigenetic players studied thus far are overexpressed in tumours compared to normal tissue. Furthermore, functional assays suggest an oncogenic role for most of those enzymes, supporting their potential as therapeutic targets in oesophageal cancer.

Targeting Chromatin Remodeling for Cancer Therapy

Background:

Epigenetic alterations comprise key regulatory events that dynamically alter gene expression and their deregulation is commonly linked to the pathogenesis of various diseases, including cancer. Unlike DNA mutations, epigenetic alterations involve modifications to proteins and nucleic acids that regulate chromatin structure without affecting the underlying DNA sequence, altering the accessibility of the transcriptional machinery to the DNA, thus modulating gene expression. In cancer cells, this often involves the silencing of tumor suppressor genes or the increased expression of genes involved in oncogenesis. Advances in laboratory medicine have made it possible to map critical epigenetic events, including histone modifications and DNA methylation, on a genome-wide scale. Like the identification of genetic mutations, mapping of changes to the epigenetic landscape has increased our understanding of cancer progression. However, in contrast to irreversible genetic mutations, epigenetic modifications are flexible and dynamic, thereby making them promising therapeutic targets. Ongoing studies are evaluating the use of epigenetic drugs in chemotherapy sensitization and immune system modulation. With the preclinical success of drugs that modify epigenetics, along with the FDA approval of epigenetic drugs including the DNA methyltransferase 1 (DNMT1) inhibitor 5-azacitidine and the histone deacetylase (HDAC) inhibitor vorinostat, there has been a rise in the number of drugs that target epigenetic modulators over recent years.

Conclusion:

We provide an overview of epigenetic modulations, particularly those involved in cancer, and discuss the recent advances in drug development that target these chromatin-modifying events, primarily focusing on novel strategies to regulate the epigenome.

G9a-mediated repression of CDH10 in hypoxia enhances breast tumour cell motility and associates with poor survival outcome

Rationale: Epigenetic mechanisms are fundamental processes that can modulate gene expression, allowing cellular adaptation to environmental conditions. Hypoxia is an important factor known to initiate the metastatic cascade in cancer, activating cell motility and invasion by silencing cell adhesion genes. G9a is a histone methyltransferase previously shown to accumulate in hypoxic conditions. While its oncogenic activity has been previously reported, not much is known about the role G9a plays in the hypoxia-mediated metastatic cascade.

Methods: The role of G9a in cell motility in hypoxic condition was determined by inhibiting G9a either by short-hairpin mediated knock down or pharmacologically using a small molecule inhibitor. Through gene expression profiling, we identified CDH10 to be an important G9a target that regulates breast cancer cell motility. Lung metastasis assay in mice was used to determine the physiological significance of G9a.

Results: We demonstrate that, while hypoxia enhances breast cancer migratory capacity, blocking G9a severely reduces cellular motility under both normoxic and hypoxic conditions and prevents the hypoxia-mediated induction of cellular movement. Moreover, inhibition of G9a histone methyltransferase activity in mice using a specific small molecule inhibitor significantly reduced growth and colonisation of breast cancer cells in the lung. We identify the type-II cadherin CDH10 as being a novel hypoxia-dependent gene, directly repressed by G9a through histone methylation. CDH10 overexpression significantly reduces cellular movements in breast cancer cell lines and prevents the hypoxia-mediated increase in cell motility. In addition, we show that CDH10 expression is prognostic in breast cancer and that it is inversely correlated to EHMT2 (G9a) transcript levels in many tumor-types, including breast cancer.

Conclusion: We propose that G9a promotes cellular motility during hypoxic stress through the silencing of the cell adhesion molecule CDH10 and we describe CDH10 as a novel prognostic biomarker for breast cancer.

MCM7 silencing promotes cutaneous melanoma cell autophagy and apoptosis by inactivating the AKT1/mTOR signaling pathway

Cutaneous melanoma (CM) has become a major public health concern. Studies illustrate that minichromosome maintenance protein 7 (MCM7) participate in various diseases including skin disease. Our study aimed to study the effects of MCM7 silencing on CM cell autophagy and apoptosis by modulating the AKT threonine kinase 1 (AKT1)/mechanistic target of rapamycin kinase (mTOR) signaling pathway. Initially, microarray analysis was used to screen the CM-related gene expression data as well as differentially expressed genes. Subsequently, MCM7 expression vector and lentivirus RNA used for MCM7 silencing (LV-shRNA-MCM7) were constructed, and these vectors, dimethyl sulfoxide (DMSO) and AKT activator SC79 were then introduced into CM cell line SK-MEL-2 to validate the role of MCM7 in cell autophagy, viability, apoptosis, cell cycle, migration, and invasion. To further investigate the regulatory mechanisms of MCM7 in CM progress, the expression of MCM7, AKT1, mTOR, cyclin D1, as well as autophagy and apoptosis relative factors, such as LC3B, SOD2, DJ-1, p62, Bcl-2, Bax, and caspase-3 in melanoma cells was determined. MCM7 might mediate the AKT1/mTOR signaling pathway to influence the progress of melanoma. MCM7 silencing contributed to the increased expression of Bax, capase-3, and autophagy-related genes (LC3B, SOD2, and DJ-1), but decreased the expression of Bcl-2, which suggested that MCM7 silencing promoted autophagy and cell apoptosis. At the same time, MCM7 silencing also attenuated cell viability, invasion, and migration, and reduced the cyclin D1 expression and protein levels of p-AKT1 and p-mTOR. Taken together, MCM7 silencing inhibited CM via inactivation of the AKT1/mTOR signaling pathway.

Inhibition of Euchromatic Histone Lysine Methyltransferase 2 (EHMT2) Suppresses the Proliferation and Invasion of Cervical Cancer Cells

EHMT2 (euchromatic histone lysine methyltransferase 2), a histone methyltransferase, has been shown to be involved in multiple human cancers. In this study, we determined mRNA and protein expression of EHMT2 in cervical cancer cells and normal cervical epithelial cells. EHMT2 was inhibited with short hairpin RNA (shEHMT2) in cervical cancer cells. Cell viability, colony proliferation, apoptosis, adhesion, and invasion assays and Western blot were performed to assess the function of EHMT2. As a result, EHMT2 was upregulated in human cervical cancer cells compared to normal cervical epithelial cells. Suppression of EHMT2 expression impairs cell proliferation and induces apoptosis. Furthermore, EHMT2 silencing inhibited cell adhesion and invasion. Finally, knockdown of EHMT2 resulted in a reduction of the expression of the tumorigenic proteins Bcl-2, Mcl-1, and Survivin and in an increase in the expression of the anti-malignant protein E-cadherin. In conclusion, our data suggest that EHMT2 plays a key role in cell proliferation and metastatic capacity in cervical cancer cells and could serve as a potential therapeutic target.

Inhibition of G9a by a small molecule inhibitor, UNC0642, induces apoptosis of human bladder cancer cells

Urinary bladder cancer (UBC) is characterized by frequent recurrence and metastasis despite the standard chemotherapy with gemcitabine and cisplatin combination. Histone modifiers are often dysregulated in cancer development, thus they can serve as an excellent drug targets for cancer therapy. Here, we investigated whether G9a, one of the histone H3 methyltransferases, was associated with UBC development. We first analyzed clinical data from public databases and found that G9a was significantly overexpressed in UBC patients. The TCGA Provisional dataset showed that the average expression level of G9a in primary UBC samples (n = 408) was 1.6-fold as much as that in normal bladder samples (n = 19; P < 0.001). Then we used small interfering RNA to knockdown G9a in human UBC T24 and J82 cell lines in vitro, and observed that the cell viability was significantly decreased and cell apoptosis induced. Next, we choosed UNC0642, a small molecule inhibitor targeting G9a, with low cytotoxicity, and excellent in vivo pharmacokinetic properties, to test its anticancer effects against UBC cells in vitro and in vivo. Treatment with UNC0642 dose-dependently decreased the viability of T24, J82, and 5637 cells with the IC₅₀ values of 9.85 ± 0.41, 13.15 ± 1.72, and 9.57 ± 0.37 μM, respectively. Furthermore, treatment with UNC0642 (1-20 μM) dose-dependently decreased the levels of histone H3K9me2, the downstream target of G9a, and increased apoptosis in T24 and J82 cells. In nude mice bearing J82 engrafts, administration of UNC0642 (5 mg/kg, every other day, i.p., for 6 times) exerted significant suppressive effect on tumor growth without loss of mouse body weight. Moreover, administration of UNC0642 significantly reduced Ki67 expression and increased the level of cleaved Caspase 3 and BIM protein in J82 xenografts evidenced by immunohistochemistry and western blot analysis, respectively. Taken together, our data demonstrated that G9a may be a promising therapeutic target for UBC, and an epigenetics-based therapy by UNC0642 is suggested.

CDK5RAP3 Inhibits the Translocation of MCM6 to Influence the Prognosis in Gastric Cancer

Cyclin-dependent kinase 5 regulatory subunit-associated protein 3 (CDK5RAP3) was identified as a tumor suppressor in gastric cancer, while, minichromosome maintenance complex component 6 (MCM6), which is closely related to the initiation of DNA replication, was reported to be upregulated in multiple malignancies. However, the interaction between these two proteins has not been investigated in gastric cancer. Here, we evaluate the connection between CDK5RAP3 and MCM6 using mass spectrometry and immunoprecipitation. In cells, cell growth and invasiveness indicate that CDK5RAP3 acts as a tumor suppressor by preventing the effects of MCM6. The potential mechanism was revealed using immunofluorescence and nuclear protein extraction. In patients, immunohistochemistry and immunofluorescence show that the protein levels of CDK5RAP3 were markedly decreased in most gastric tumor tissues compared with adjacent nontumor tissues, and the expression levels of MCM6 in the nucleus showed the opposite trend. Prognostic analysis showed that the combined expression of CDK5RAP3 and MCM6 was an independent prognostic factor correlating with the overall survival of gastric cancer patients. Cox regression analysis indicated that the expression of CDK5RAP3 and MCM6 corresponded to T, N, and M stages. Our results demonstrate that CDK5RAP3 can interact with MCM6 and prevent MCM6 from translocating into the nucleus, which may be a potential mechanism through which CDK5RAP3 negatively regulates the proliferation of gastric cancer.

Insights for the design of protein lysine methyltransferase G9a inhibitors

The epigenetic control of gene expression could be affected by addition and/or removal of post-translational modifications such as phosphorylation, acetylation and methylation of histone proteins, as well as methylation of DNA (5-methylation on cytosines). Misregulation of these modifications is associated with altered gene expression, resulting in various disease conditions. G9a belongs to the protein lysine methyltransferases that specifically methylates the K9 residue of histone H3, leading to suppression of several tumor suppressor genes. In this review, G9a functions, role in various diseases, structural biology aspects for inhibitor design, structure-activity relationship among the reported inhibitors are discussed which could aid in the design and development of potent G9a inhibitors for cancer treatment in the future.

The Epigenome in Multiple Myeloma: Impact on Tumor Cell Plasticity and Drug Response

Multiple myeloma (MM) is a clonal plasma cell malignancy that develops primarily in the bone marrow (BM), where reciprocal interactions with the BM niche foster MM cell survival, growth, and drug resistance. MM cells furthermore reshape the BM to their own needs by affecting the different BM stromal cell types resulting in angiogenesis, bone destruction, and immune suppression. Despite recent advances in treatment modalities, MM remains most often incurable due to the development of drug resistance to all standard of care agents. This underscores the unmet need for these heavily treated relapsed/refractory patients. Disruptions in epigenetic regulation are a well-known hallmark of cancer cells, contributing to both cancer onset and progression. In MM, sequencing and gene expression profiling studies have also identified numerous epigenetic defects, including locus-specific DNA hypermethylation of cancer-related and B cell specific genes, genome-wide DNA hypomethylation and genetic defects, copy number variations and/or abnormal expression patterns of various chromatin modifying enzymes. Importantly, these so-called epimutations contribute to genomic instability, disease progression, and a worse outcome. Moreover, the frequency of mutations observed in genes encoding for histone methyltransferases and DNA methylation modifiers increases following treatment, indicating a role in the emergence of drug resistance. In support of this, accumulating evidence also suggest a role for the epigenetic machinery in MM cell plasticity, driving the differentiation of the malignant cells to a less mature and drug resistant state. This review discusses the current state of knowledge on the role of epigenetics in MM, with a focus on deregulated histone methylation modifiers and the impact on MM cell plasticity and drug resistance. We also provide insight into the potential of epigenetic modulating agents to enhance clinical drug responses and avoid disease relapse.

Identification of driver genes associated with chemotherapy resistance of Ewing's sarcoma

Background

The aim of this study was to identify the driver genes associated with chemotherapy resistance of Ewing’s sarcoma and potential targets for Ewing’s sarcoma treatment.

Methods

Two mRNA microarray datasets, GSE12102 and GSE17679, were downloaded from the Gene Expression Omnibus database, which contain 94 human Ewing’s sarcoma samples, including 65 from those who experienced a relapse and 29 from those with no evidence of disease. The differen tially expressed genes (DEGs) were identified using LIMMA package R. Subsequently, Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analyses were performed for DEGs using Database for Annotation, Visualization and Integrated Analysis. The protein–protein interaction network was constructed using Cytoscape software, and module analysis was performed using Molecular Complex Detection.

Results

A total of 206 upregulated DEGs and 141 downregulated DEGs were identified. Upregulated DEGs were primarily enriched in DNA replication, nucleoplasm and protein kinase binding for biological processes, cellular component and molecular functions, respectively. Downregulated DEGs were predominantly involved in receptor clustering, membrane raft, and ligand-dependent nuclear receptor binding. The protein–protein interaction network of DEGs consisted of 150 nodes and 304 interactions. Thirteen hub genes were identified, and biological analysis revealed that these genes were primarily enriched in cell division, cell cycle, and mitosis. Furthermore, based on closeness centrality, betweenness centrality, and degree centrality, the three most significant genes were identified as GAPDH, AURKA, and EHMT2. Furthermore, the significant network module was composed of nine genes. These genes were primarily enriched in mitotic nuclear division, mitotic chromosome condensation, and nucleoplasm.

Conclusion

These hub genes, especially GAPDH, AURKA, and EHMT2, may be closely associated with the progression of Ewing’s sarcoma chemotherapy resistance, and further experiments are needed for confirmation.

The novel prognostic marker, EHMT2, is involved in cell proliferation via HSPD1 regulation in breast cancer

Molecular classifications of breast cancer (BRC), such as human epidermal growth factor receptor 2 (HER2), luminal A and luminal B, have been developed to reduce unnecessary treatment by dividing patients with BRC into low- and high-risk progression groups. However, these methods do not cover all of the pathological characteristics of BRC, and investigations into novel prognostic/therapeutic markers are thus continually required. In this study, we identified the overexpression of the histone methyltransferase, euchromatic histone-lysine N-methyltransferase 2 (EHMT2) in BRC samples (n=1,222) and normal samples (n=113) derived from the TCGA portal by performing a BRC tissue microarray. EHMT2 overexpression was clearly associated with a poor prognosis in multiple cohorts of patients with BRC (total, n=1,644). Furthermore, the knockdown of EHMT2 expression affected cell apoptosis via the downregulation and re-localization of heat shock protein family D (Hsp60) member 1 (HSPD1). In addition, a statistically significant positive correlation between EHMT2 and HSPD1 expression was revealed in the clinical cohorts. On the whole, the findings of this study may assist the development of novel therapeutic strategies and provide a prognostic marker (EHMT2) for patients with BRC.

Dual Inhibition of DNA and Histone Methyltransferases Increases Viral Mimicry in Ovarian Cancer Cells

Ovarian cancer ranks as the most deadly gynecologic cancer, and there is an urgent need to develop more effective therapies. Previous studies have shown that G9A, a histone methyltransferase that catalyzes mono- and dimethylation of histone H3 lysine9, is highly expressed in ovarian cancer tumors, and its overexpression is associated with poor prognosis. Here we report that pharmacologic inhibition of G9A in ovarian cancer cell lines with high levels of G9A expression induces synergistic antitumor effects when combined with the DNA methylation inhibitor (DNMTi) 5-aza-2'-deoxycytidine (5-aza-CdR). These antitumor effects included upregulation of endogenous retroviruses (ERV), activation of the viral defense response, and induction of cell death, which have been termed "viral mimicry" effects induced by DNMTi. G9Ai treatment further reduced H3K9me2 levels within the long terminal repeat regions of ERV, resulting in further increases of ERV expression and enhancing "viral mimicry" effects. In contrast, G9Ai and 5-aza-CdR were not synergistic in cell lines with low basal G9A levels. Taken together, our results suggest that the synergistic effects of combination treatment with DNMTi and G9Ai may serve as a novel therapeutic strategy for patients with ovarian cancer with high levels of G9A expression.Significance: Dual inhibition of DNA methylation and histone H3 lysine 9 dimethylation by 5-aza-CdR and G9Ai results in synergistic upregulation of ERV and induces an antiviral response, serving as a basis for exploring this novel combination treatment in patients with ovarian cancer. Cancer Res; 78(20); 5754-66. ©2018 AACR.

Prognostic value of minichromosome maintenance mRNA expression in early-stage pancreatic ductal adenocarcinoma patients after pancreaticoduodenectomy

Background

The aim of the current study was to investigate the potential prognostic value of minichromosome maintenance (MCM) genes in patients with early-stage pancreatic ductal adenocarcinoma (PDAC) after pancreaticoduodenectomy by using the RNA-sequencing dataset from The Cancer Genome Atlas (TCGA).

Methods

An RNA-sequencing dataset of 112 early-stage PDAC patients who received a pancreaticoduodenectomy was obtained from TCGA. Survival analysis was used to identify potential prognostic values of MCM genes in PDAC overall survival (OS).

Results

Through mining public databases, we observed that MCM genes (MCM2, MCM3, MCM4, MCM5, MCM6, and MCM7) were upregulated in pancreatic cancer tumor tissue and have a strong positive coexpression with each other. Multivariate survival analysis indicated that a high expression of MCM4 significantly increased the risk of death in patients with PDAC, and time-dependent receiver operating characteristic analysis showed an area under the curve of 0.655, 0.587, and 0.509 for a 1-, 2-, and 3-year PDAC OS prediction, respectively. Comprehensive survival analysis of MCM4 using stratified and joint effects survival analysis suggests that MCM4 may be an independent prognostic indicator for PDAC OS. Gene set enrichment analysis indicated that MCM4 may participate in multiple biologic processes and pathways, including DNA replication, cell cycle, tumor protein p53, and Notch signaling pathways, thereby affecting prognosis of PDAC patients.

Conclusions

Our study indicates that MCM2–7 were upregulated in pancreatic cancer tumor tissues, and mRNA expression of MCM4 may serve as an independent prognostic indicator for PDAC OS prediction after pancreaticoduodenectomy.

Distinct Diagnostic and Prognostic Values of Minichromosome Maintenance Gene Expression in Patients with Hepatocellular Carcinoma

Background: The aim of the present study was to identify diagnostic and prognostic values of minichromosome maintenance (MCM) gene expression in patients with hepatocellular carcinoma (HCC).

Methods: The biological function of the MCM genes were investigated by bioinformatics analysis. The diagnostic and prognostic values of the MCM genes were investigated by using the data of HCC patients from the GSE14520 and The Cancer Genome Atlas (TCGA) databases.

Results: Bioinformatics analysis of the MCM genes substantiated that MCM2-7 genes were significantly enriched in DNA replication and cell cycle, and co-expressed with each other. These genes also co-expressed in HCC tumor tissue in both the GSE14520 and TCGA cohort. We also observed that the expression of the MCM2-7 genes was increased in tumor tissue, and diagnostic receiver operating characteristic analysis of MCM2-7 indicated that these genes could serve as sensitive diagnostic markers in HCC. Survival analysis in the GSE14520 cohort suggested that expression of MCM2, MCM4, MCM5, and MCM6 were significantly associated with hepatitis B virus-related HCC overall survival (OS). However, none of the MCM genes were associated with recurrence-free survival in the GSE14520 cohort. The validation cohort of TCGA suggested that the expression of MCM2, MCM6, and MCM7 were significantly correlated with HCC OS.

Conclusion: Our study indicated that MCM2-7 genes may be potential diagnostic biomarkers in patients with HCC. Among them, MCM2 and MCM6 may serve as potential prognostic biomarkers for HCC.

Expression of Minichromosome Maintenance Proteins (MCM) and Cancer Prognosis: A meta-analysis

Minichromosome maintenance proteins (MCM) played a critical role in replication and cell cycle progression. However, their prognostic roles in cancer remain controversial. Therefore, we performed a meta-analysis to investigate the prognostic value of MCMs in cancers. Totally 31 eligible articles with 7653 cancer patients were included in this meta-analysis. We evaluated the relationship between MCMs expression and overall survival (OS) in various cancer patients by using pooled hazard ratios (HRs) and risk ratios (RRs) with 95% confidence intervals (CIs). The meta-analysis showed that carriers with high expression of MCM5 and MCM7 were significantly associated with short OS for pooled HR (HR=1.04, 95% CI=1.01-1.08, P=0.020, HR=1.78, 95% CI=1.04-3.02, P=0.035, respectively). For pooled RR, individuals with increased MCM2 and MCM7 expression were significantly correlated with poor OS (RR=2.30, 95% CI=1.14-4.63, P=0.019; RR=3.52, 95% CI=2.01-6.18, P<0.001, respectively). The findings suggest that high expression of MCM2, MCM5 and MCM7 might serve as predictive biomarkers for poor prognosis in cancers.

Targeting EHMT2 reverses EGFR-TKI resistance in NSCLC by epigenetically regulating the PTEN/AKT signaling pathway

Epidermal growth factor receptor tyrosine kinase inhibitor (EGFR-TKI) resistance is a major obstacle in the treatment of non-small cell lung cancer (NSCLC). Epigenetic alterations have been shown to be involved in NSCLC oncogenesis; however, their function in EGFR-TKI resistance remains uncharacterized. Here, we found that an EHMT2 inhibitor, UNC0638, can significantly inhibit cell growth and induce apoptosis in EGFR-TKI-resistant NSCLC cells. Additionally, we also found that EHMT2 expression and enzymatic activity levels were elevated in EGFR-TKI-resistant NSCLC cells. Moreover, we determined that genetic or pharmacological inhibition of EHMT2 expression enhanced TKI sensitivity and suppressed migration and tumor sphere formation in EGFR-TKI-resistant NSCLC cells. Further investigation revealed that EHMT2 contributed to PTEN transcriptional repression and thus facilitated AKT pathway activation. The negative relationship between EHMT2 and PTEN was confirmed by our clinical study. Furthermore, we determined that combination treatment with the EHMT2 inhibitor and Erlotinib resulted in enhanced antitumor effects in a preclinical EGFR-TKI-resistance model. We also found that high EHMT2 expression along with low PTEN expression can predict poor overall survival in patients with NSCLC. In summary, our findings showed that EHMT2 facilitated EGFR-TKI resistance by regulating the PTEN/AKT pathway in NSCLC cells, suggesting that EHMT2 may be a target in the clinical treatment of EGFR-TKI-resistant NSCLC.

Genomic and Epigenomic Aberrations in Esophageal Squamous Cell Carcinoma and Implications for Patients

Esophageal squamous cell carcinoma (ESCC) is a common malignancy without effective therapy. The exomes of more than 600 ESCCs have been sequenced in the past 4 years, and numerous key aberrations have been identified. Recently, researchers reported both inter- and intratumor heterogeneity. Although these are interesting observations, their clinical implications are unclear due to the limited number of samples profiled. Epigenomic alterations, such as changes in DNA methylation, histone acetylation, and RNA editing, also have been observed in ESCCs. However, it is not clear what proportion of ESCC cells carry these epigenomic aberrations or how they contribute to tumor development. We review the genomic and epigenomic characteristics of ESCCs, with a focus on emerging themes. We discuss their clinical implications and future research directions.

The histone methyltransferase G9a: a new therapeutic target in biliary tract cancer

The histone methyltransferase G9a (EHMT2) is a key enzyme for dimethylation of lysine 9 at histone 3 (H3K9me2), a suppressive epigenetic mark. G9a is over-expressed in tumor cells and contributes to cancer aggressiveness. Biliary tract cancer (BTC) is a rare cancer with dismal prognosis due to a lack of effective therapies. Currently, there are no data on the role of G9a in BTC carcinogenesis. We analyzed G9a expression in n=68 BTC patient specimens and correlated the data with clinicopathological and survival data. Moreover, we measured G9a expression in a panel of BTC cell lines and evaluated the cytotoxic effect of G9a inhibition in BTC cells using established small-molecule G9a inhibitors. G9a was considerably expressed in about half of BTC cases and was significantly associated with grading and tumor size. Additionally, we observed significant differences of G9a expression between growth type and tumor localization groups. G9a expression diametrically correlated with Vimentin (positive) and E-Cadherin (negative) expression. Importantly, survival analysis revealed G9a as a significant prognostic factor of poor survival in patients with BTC. In BTC cells, G9a and H3K9me2 were detectable in a cell line-dependent manner on mRNA and/or protein level, respectively. Treatment of BTC cells with established small-molecule G9a inhibitors resulted in reduction of cell viability as well as reduced G9a and H3K9me2 protein levels. The present study strongly suggests that G9a contributes to BTC carcinogenesis and may represent a potential prognostic factor as well as a therapeutic target.