Activated MEK/ERK Pathway Drives Widespread and Coordinated Overexpression of UHRF1 and DNMT1 in Cancer cells

The roles of phosphorylation of signaling proteins in the prognosis of acute myeloid leukemia

Signaling pathways of Retinoblastoma (Rb) protein, Akt-kinase, and Erk-kinase (extracellular signal-regulated kinase) have an important role in the pathogenesis of acute myeloid leukemia. Constitutive activation of these proteins by phosphorylation contributes to cell survival by regulation of cell cycle, proliferation and proapoptotic signaling processes. According to previous data phosphorylated forms of these proteins represent a worse outcome for cancer patients. We investigated the presence of phosphorylated Rb (P-Rb), Akt (P-Akt) and Erk (P-Erk) proteins by Western blot technique using phospho-specific antibodies in bone marrow or peripheral blood samples of 69 AML patients, 36 patients with myelodysplastic syndrome (MDS) and 10 healthy volunteers. Expression level of PTEN (Phosphatase and tensin homolog) and PHLPP (PH domain and leucine-rich repeat Protein Phosphatase) phosphatases, the negative regulators of Akt kinase pathway were also examined. We tested the effect of these proteins on survival and on the correlation with known prognostic features in AML. We found 46.3% of AML patients had detectable P-Rb, 34.7% had P-Akt and 28.9% had P-Erk protein. 66.1% of patients expressing PTEN, 38.9% PHLPP, 37.2% both PTEN and PHLPP and 32.2% neither PTEN nor PHLPP phosphatases. Compared to nucleophosmin mutation (NPMc) negative samples P-Erk was significantly less in nucleophosmin mutated patients, P-Rb was significantly less in patients' group with more than 30 G/L peripheral leukocyte count by diagnosis. PHLPP was significantly present in FAB type M5. The expression of P-Rb represented significant better overall survival (OS), while P-Akt represented significantly worse event-free survival (EFS) in unfavorable cytogenetics patients. The presence of both PHLPP and PTEN phosphatases contributes to better OS and EFS, although the differences were not statistically significant. We confirmed significant positive correlation between P-Akt and PHLPP. Assessing the phosphorylation of Rb, Akt and Erk may define a subgroup of AML patients who would benefit especially from new targeted treatment options complemented the standard chemotherapy, and it may contribute to monitoring remission, relapse or progression of AML.

The expression and clinical significance of UHRF1 in soft tissue sarcomas and its prognostic value

To explore the expression and prognostic value of UHRF1 gene in soft tissue sarcoma (STS) and its related molecular mechanism. The expression data and clinicopathological parameters of STS were downloaded from the Cancer Genome Atlas (TCGA). The expression level of UHRF1 in STS and adjacent tissues and its relationship with clinicopathological characteristics were analyzed. The expression level of UHRF1 in STS tissues was significantly higher than that in paracancerous tissues (P < .001), and the overall survival (OS) time of patients with high UHRF1 expression was significantly shorter than that of patients with low UHRF1 expression (P = .002). The expression of UHRF1 was correlated with tumor necrosis, histological type and metastasis, and the differences were statistically significant (P = .013; P = .001; P = .002). The area ratio under receiver operating characteristic (ROC) curve between STS tissue and adjacent tissue of UHRF1 expression was 0.994. Number of tumors (HR = 0.416, 95%CI = 0.260-0.666, P < .001), depth of tumor (HR = 2.888, 95%CI = 0.910-9.168, P = .033), metastasis (HR = 2.888, 95% CI = 1.762-4.732, P < .001), residual tumor (HR = 2.637, 95% CI = 1.721-4.038, P < .001) and UHRF1 expression (HR = 1.342, 95% CI = 1.105-1.630, P = .003) were significantly associated with OS, and high expression of UHRF1 (HR = 1.387, 95%CI = 1.008-1.907, P = .044) was an independent risk factor for the prognosis of STS patients. The results of the nomogram exhibited that UHRF1 expression level had a significant effect on the total score value. GSEA enrichment analysis suggested that UHRF1 was involved in 14 signaling pathways regulating mRNA spliceosome, cell cycle, P53 signaling pathway were identified. Single sample gene set enrichment analysis (ssGSEA) exhibited that the expression of UHRF1 in STS was positively correlated with the level of Th2 cell infiltration, and negatively correlated with plasmacytoid dendritic cells (pDC), natural killer cells (NK), Eosinophils, Mast cells, etc. UHRF1 expression is involved in the immune microenvironment of HCC and affects the occurrence and development of HCC. UHRF1 is highly expressed in STS tissues. It is involved in the regulation of multiple tumor-related signaling pathways and immune cell microenvironment, suggesting that UHRF1 may be a potential molecular marker for prognosis prediction and targeted therapy of STS patients.

Roles of post-translational modifications of UHRF1 in cancer

UHRF1 as a member of RING-finger type E3 ubiquitin ligases family, is an epigenetic regulator with five structural domains. It has been involved in the regulation of a series of biological functions, such as DNA replication, DNA methylation, and DNA damage repair. Additionally, aberrant overexpression of UHRF1 has been observed in over ten cancer types, indicating that UHRF1 is a typical oncogene. The overexpression of UHRF1 repressed the transcription of such tumor-suppressor genes as CDKN2A, BRCA1, and CDH1 through DNMT1-mediated DNA methylation. In addition to the upstream transcription factors regulating gene transcription, post-translational modifications (PTMs) also contribute to abnormal overexpression of UHRF1 in cancerous tissues. The types of PTM include phosphorylation, acetylation, methylationand ubiquitination, which regulate protein stability, histone methyltransferase activity, intracellular localization and the interaction with binding partners. Recently, several novel PTM types of UHRF1 have been reported, but the detailed mechanisms remain unclear. This comprehensive review summarized the types of UHRF1 PTMs, as well as their biological functions. A deep understanding of these crucial mechanisms of UHRF1 is pivotal for the development of novel UHRF1-targeted anti-cancer therapeutic strategies in the future.

Polyphyllin I induces ferroptosis in castration-resistant prostate cancer cells through the ERK/DNMT1/ACSL4 axis

BACKGROUND

Castration-resistant prostate cancer (CRPC) inevitably arises after androgen deprivation therapy (ADT). Therefore, there is an urgent need to search for novel treatment strategies for CRPC. Polyphyllin I (PPI), one of the steroidal saponins in paris polyphylla, has been shown to have an anticancer effect. This study investigated the role and mechanism of PPI in CRPC cell ferroptosis.

METHODS

Protein levels of GPX4, p-extracellular regulated protein kinases (ERK), ERK, DNMT1, and ACSL4 were measured by Western blot. DNMT1 and ACSL4 mRNA expression was analyzed by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). Prostate cancer cells (DU145, PC3) were treated with PPI. Cell viability was assessed utilizing Cell Counting Kit-8 (CCK-8) assay. The role of PPI in regulating ferroptosis was determined by analyzing lipid reactive oxygen species (ROS), malonyl dialdehyde (MDA), iron (Fe2+ ), and glutathione (GSH) content. Chromatin immunoprecipitation (ChIP) assay verified the effect of DNMT1 on the ACSL4 promoter. The methylation level of ACSL4 promoter was assessed utilizing MSP. A nude mice xenograft was adopted to detect the effect of PPI in vivo.

RESULTS

PPI inhibited CRPC cell proliferation, reduced levels of GSH and GPX4, and increased levels of MDA, Fe2+ , and ROS, while ERK inhibitor reversed the effect of PPI on ferroptosis. PPI repressed the methylation level of ACSL4 promoter by inhibiting DNMT1. DNMT1 knockdown promoted CRPC cell ferroptosis by regulating ACSL4. PPI induced ferroptosis and suppressed CRPC growth in nude mice.

CONCLUSION

PPI can be used as a ferroptosis inducer to induce ferroptosis in CRPC cells via the ERK/DNMT1/ACSL4 axis, suggesting that PPI may be a new strategy for CRPC treatment.

Natural and Synthetic Anticancer Epidrugs Targeting the Epigenetic Integrator UHRF1

Cancer is one of the leading causes of death worldwide, and its incidence and mortality are increasing each year. Improved therapeutic strategies against cancer have progressed, but remain insufficient to invert this trend. Along with several other risk factors, abnormal genetic and epigenetic regulations play a critical role in the initiation of cellular transformation, as well as tumorigenesis. The epigenetic regulator UHRF1 (ubiquitin-like, containing PHD and RING finger domains 1) is a multidomain protein with oncogenic abilities overexpressed in most cancers. Through the coordination of its multiple domains and other epigenetic key players, UHRF1 regulates DNA methylation and histone modifications. This well-coordinated dialogue leads to the silencing of tumor-suppressor genes (TSGs) and facilitates tumor cells' resistance toward anticancer drugs, ultimately promoting apoptosis escape and uncontrolled proliferation. Several studies have shown that the downregulation of UHRF1 with natural compounds in tumor cells induces the reactivation of various TSGs, inhibits cell growth, and promotes apoptosis. In this review, we discuss the underlying mechanisms and the potential of various natural and synthetic compounds that can inhibit/minimize UHRF1's oncogenic activities and/or its expression.

SMYD3 represses tumor-intrinsic interferon response in HPV-negative squamous cell carcinoma of the head and neck

Cancers often display immune escape, but the mechanisms are incompletely understood. Herein, we identify SMYD3 as a mediator of immune escape in human papilloma virus (HPV)-negative head and neck squamous cell carcinoma (HNSCC), an aggressive disease with poor response to immunotherapy with pembrolizumab. SMYD3 depletion induces upregulation of multiple type I interferon (IFN) response and antigen presentation machinery genes in HNSCC cells. Mechanistically, SMYD3 binds to and regulates the transcription of UHRF1, encoding for a reader of H3K9me3, which binds to H3K9me3-enriched promoters of key immune-related genes, recruits DNMT1, and silences their expression. SMYD3 further maintains the repression of immune-related genes through intragenic deposition of H4K20me3. In vivo, Smyd3 depletion induces influx of CD8+ T cells and increases sensitivity to anti-programmed death 1 (PD-1) therapy. SMYD3 overexpression is associated with decreased CD8 T cell infiltration and poor response to neoadjuvant pembrolizumab. These data support combining SMYD3 depletion strategies with checkpoint blockade to overcome anti-PD-1 resistance in HPV-negative HNSCC.

NUP98 and RAE1 sustain progenitor function through HDAC-dependent chromatin targeting to escape from nucleolar localization

Self-renewing somatic tissues rely on progenitors to support the continuous tissue regeneration. The gene regulatory network maintaining progenitor function remains incompletely understood. Here we show that NUP98 and RAE1 are highly expressed in epidermal progenitors, forming a separate complex in the nucleoplasm. Reduction of NUP98 or RAE1 abolishes progenitors' regenerative capacity, inhibiting proliferation and inducing premature terminal differentiation. Mechanistically, NUP98 binds on chromatin near the transcription start sites of key epigenetic regulators (such as DNMT1, UHRF1 and EZH2) and sustains their expression in progenitors. NUP98's chromatin binding sites are co-occupied by HDAC1. HDAC inhibition diminishes NUP98's chromatin binding and dysregulates NUP98 and RAE1's target gene expression. Interestingly, HDAC inhibition further induces NUP98 and RAE1 to localize interdependently to the nucleolus. These findings identified a pathway in progenitor maintenance, where HDAC activity directs the high levels of NUP98 and RAE1 to directly control key epigenetic regulators, escaping from nucleolar aggregation.

Lenvatinib inhibited HCC cell migration and invasion through regulating the transcription and ubiquitination of UHRF1 and DNMT1

Hepatocellular carcinoma (HCC) is one of the most common causes of malignancy-related deaths. Lenvatinib, as a multi-targeted tyrosine kinase inhibitor, has gained increasing attention for its antitumor activity. However, the effect and mechanisms of Lenvatinib on HCC metastasis are virtually unknown. In this study, we revealed that Lenvatinib inhibited HCC cell motility and epithelial mesenchymal transition (EMT), along with cell adhesion and extension. Concomitant high DNMT1 and UHRF1 mRNA levels were in HCC patients and indicated worse prognosis. On the one hand, Lenvatinib modulated the transcription of UHRF1 and DNMT1via negatively regulation of ERK/MAPK pathway. On the other hand, Lenvatinib downregulated DNMT1 and UHRF1 expression by promoting their protein degradation through ubiquitin-proteasome pathway, consequently, resulting in upregulation of E-Cadherin. Moreover, Lenvatinib attenuated Huh7 cell adhesion and metastasis in vivo. Our findings provided insight into the intriguing molecular mechanisms regarding the anti-metastasis effect of Lenvatinib in HCC.

The p110α/ΔNp63α complex mutations in triple-negative breast cancer: Potential targets for transcriptional-based therapies

BACKGROUND

Hotspot mutations occurring in the p110α domain of the PIK3CA gene, specifically p110αH1047R/L increase tumor metastasis and cell motility in triple-negative breast cancer (TNBC). These mutations also affect the transcriptional regulation of ΔNp63α, a significant isoform of the p53 protein involved in cancer progression. This study attempts to investigate the transcriptional impact of p110αH1047R/L mutations on the PIK3CA/ΔNp63α complex in TNBC carcinogenesis.

METHODS

We performed site-directed mutagenesis to introduce p110αH1047R/L mutations and evaluated their oncogenic effects on the growth, invasion, migration, and apoptosis of three different TNBC cell lines in vitro. We investigated the impact of these mutations on the p110α/ΔNp63α complex and downstream transcriptional signaling pathways at the gene and protein levels. Additionally, we used bioinformatics techniques such as molecular dynamics simulations and protein-protein docking to gain insight into the stability and structural changes induced by the p110αH1047R/L mutations in the p110α/ΔNp63α complex and downstream signaling pathway.

RESULTS

The presence of PIK3CA oncogenic hotspot mutations in the p110α/ΔNp63α complex led to increased scattering of TNBC cells during growth, migration, and invasion. Our in vitro mutagenesis assay showed that the p110αH1047R/L mutations activated the PI3K-Akt-mTOR and tyrosine kinase receptor pathways, resulting in increased cell proliferation, invasion, and apoptosis in TNBC cells. These mutations decreased the repressing effect of ΔNp63α on the p110α kinase domain, leading to the enhancement of downstream signaling pathways of PI3K and tyrosine kinase receptors and oncogenic transformation in TNBC. Additionally, our findings suggest that the physical interaction between the DNA binding domain of ΔNp63α and the kinase domain of p110α may be partially impaired, potentially leading to alterations in the conformation of the p110α/ΔNp63α complex.

CONCLUSION

Our findings suggest that targeting the p110αH1047R/L mutations in TNBC could be a promising strategy for developing transcriptional-based therapies. Restoring the interaction between ΔNp63α and the p110α kinase domain, which is disrupted by these mutations, may provide a new approach to treating TNBC.

DNA methyltransferase-1 in acute myeloid leukaemia: beyond the maintenance of DNA methylation

DNA methylation is considered an essential epigenetic event during leukaemogenesis and the emergence of drug resistance, which is primarily regulated by DNA methyltransferases. DNA methyltransferase-1 (DNMT1) is one of the members of DNA methyltransferases, in charge of maintaining established methylation. Recently, DNMT1 is shown to promote malignant events of cancers through the epigenetic and non-epigenetic processes. Increasing studies in solid tumours have identified DNMT1 as a therapeutic target and a regulator of therapy resistance; however, it is unclear whether DNMT1 is a critical regulator in acute myeloid leukaemia (AML) and how it works. In this review, we summarized the recent understanding of DNMT1 in normal haematopoiesis and AML and discussed the possible functions of DNMT1 in promoting the development of AML and predicting the sensitivity of hypomethylation agents to better understand the relationship between DNMT1 and AML and to look for new hope to treat AML patients.Key messagesThe function of DNA methyltransferase-1 in acute myeloid leukaemia.DNA methyltransferase-1 predicts the sensitivity of drug and involves the emergence of drug resistance.

ERK1/2 inhibits Cullin 3/SPOP-mediated PrLZ ubiquitination and degradation to modulate prostate cancer progression

The gene encoding the E3 ubiquitin ligase substrate-binding adaptor SPOP is frequently mutated in prostate cancer (PCa), but how SPOP functions as a tumor suppressor and contributes to PCa pathogenesis remains poorly understood. Prostate Leucine Zipper (PrLZ) serves as a prostate-specific and androgen-responsive gene, which plays a pivotal role in the malignant progression of PCa. However, the upstream regulatory mechanism of PrLZ protein stability and its physiological contribution to PCa carcinogenesis remain largely elusive. Here we report that PrLZ can be degraded by SPOP. PrLZ abundance is elevated in SPOP-mutant expressing PCa cell lines and patient specimens. Meanwhile, ERK1/2 might regulate SPOP-mediated PrLZ degradation through phosphorylating PrLZ at Ser40, which blocks the interaction between SPOP and PrLZ. In addition, we identify IL-6 might act as an upstream PrLZ degradation regulator via promoting its phosphorylation by ERK1/2, leading to its impaired recognition by SPOP. Thus, our study reveals a novel SPOP substrate PrLZ which might be controlled by ERK1/2-mediated phosphorylation, thereby facilitating to explore novel drug targets and improve therapeutic strategy for PCa.

An shRNA kinase screen identifies regulators of UHRF1 stability and activity in mouse embryonic stem cells

Propagation of DNA methylation through cell division relies on the recognition of methylated cytosines by UHRF1. In reprogramming of mouse embryonic stem cells to naive pluripotency (also known as ground state), despite high levels of Uhrf1 transcript, the protein is targeted for degradation by the proteasome, leading to DNA methylation loss. We have undertaken an shRNA screen to identify the signalling pathways that converge upon UHRF1 and control its degradation, using UHRF1-GFP fluorescence as readout. Many candidates we identified are key enzymes in regulation of glucose metabolism, nucleotide metabolism and Pi3K/AKT/mTOR pathway. Unexpectedly, while downregulation of all candidates we selected for validation rescued UHRF1 protein levels, we found that in some of the cases this was not sufficient to maintain DNA methylation. This has implications for development, ageing and diseased conditions. Our study demonstrates two separate processes that regulate UHRF1 protein abundance and activity.

E2F1‐mediated AUF1 upregulation promotes HCC development and enhances drug resistance via stabilization of AKR1B10

The AU‐rich binding factor 1 (AUF1) is one of the well known adenylate‐uridylate‐rich element (ARE)‐specific RNA‐binding proteins (ARE‐BPs) for which dysregulation has been reported in various human cancers. However, the involvement of AUF1 in the initiation and progression of hepatocellular carcinoma (HCC) is still elusive. In this study, we aimed at exploring the clinical significance, function, and mechanism of the abnormal expression of AUF1 in HCC. Using a bioinformatics analysis of The Cancer Genome Atlas (TCGA) and Liver Cancer Institute (LCI) database, we identified that AUF1 was abnormally highly expressed in HCC tissues and that the high expression of AUF1 was correlated with poor prognosis in patients with HCC. We also confirmed the increased AUF1 expression and its prognostic value in our HBV‐related HCC cohorts. AUF1 overexpression in hepatoma cells promoted cell proliferation and increased the resistance of hepatoma cells toward doxorubicin, whereas knockdown of AUF1 exerted the opposite effects. Mechanistically, we demonstrated that AKR1B10 was a critical target of AUF1 and was essential for sustaining the AUF1‐induced proliferation and drug resistance of hepatoma cells. AUF1 increased AKR1B10 expression by binding to the 3′UTR region of AKR1B10 mRNA and stabilizing AKR1B10 mRNA. Additionally, we demonstrated that E2F1 enhanced AUF1 expression in HCC at the transcription level. Our study revealed a novel role of AUF1 in promoting the development and drug resistance of HCC via the post‐transcriptional regulation of AKR1B10 expression. The E2F1/AUF1/AKR1B10 axis can serve as a potential therapeutic target in HCC.

ERBB Signaling Pathway in Cancer Stem Cells

The epidermal growth factor receptor (EGFR) was first tyrosine kinase receptor linked to human cancers. EGFR or ERBB1 is a member of ERBB subfamily, which consists of four type I transmembrane receptor tyrosine kinases, ERBB1, 2, 3 and 4. ERBBs form homo/heterodimers after ligand binding except ERBB2 and consequently becomes activated. Different signal pathways, such as phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT), RAS/RAF/MEK/ERK, phospholipase Cγ and JAK-STAT, are triggered by ERBB activation. Since ERBBs, through these pathways, regulate stemness and differentiation of cancer stem cells (CSCs), their roles in CSC tumorigenicity have extensively been investigated. The hyperactivation of ERBBs and its downstream pathways stimulated by either genetic and/or epigenetic factors are frequently described in many types of human cancers. Their dysregulations make cells acquiring CSC characters such as survival, tumorigenicity and stemness. Because of the roles in tumor growth and progress, ERBBs are considered to be one of the drug targets as cancer treatment strategy. In this chapter, we will summarize the structure, function and roles of ERBB subfamily along with their relative pathways regulating the stemness and tumorigenicity of CSCs. Finally, we will discuss the targeting therapy strategies of cancer along with ERBBs in addition to some challenges and future perspectives.

Nuclear UHRF1 is a gate-keeper of cellular AMPK activity and function

The AMP-activated protein kinase (AMPK) is a central regulator of energy homeostasis. Although much has been learned on how low energy status and glucose starvation activate AMPK, how AMPK activity is properly controlled in vivo is still poorly understood. Here we report that UHRF1, an epigenetic regulator highly expressed in proliferating and cancer cells, interacts with AMPK and serves to suppress AMPK activity under both basal and stressed conditions. As a nuclear protein, UHRF1 promotes AMPK nuclear retention and strongly suppresses nuclear AMPK activity toward substrates H2B and EZH2. Importantly, we demonstrate that UHRF1 also robustly inhibits AMPK activity in the cytoplasm compartment, most likely as a consequence of AMPK nucleocytoplasmic shuttling. Mechanistically, we found that UHRF1 has no obvious effect on AMPK activation by upstream kinases LKB1 and CAMKK2 but inhibits AMPK activity by acting as a bridging factor targeting phosphatase PP2A to dephosphorylate AMPK. Hepatic overexpression of UHRF1 showed profound effects on glucose and lipid metabolism in wild-type mice but not in those with the liver-specific knockout of AMPKα1/α2, whereas knockdown of UHRF1 in adipose tissue led to AMPK activation and reduced sizes of adipocytes and lipogenic activity, highlighting the physiological significance of this regulation in glucose and lipid metabolism. Thus, our study identifies UHRF1 as a novel AMPK gate-keeper with critical roles in cellular metabolism.

DNMT1-induced miR-378a-3p silencing promotes angiogenesis via the NF-κB signaling pathway by targeting TRAF1 in hepatocellular carcinoma

BACKGROUND

Angiogenesis plays an important role in the occurrence, development and metastasis of hepatocellular carcinoma (HCC). According to previous studies, miR-378a participates in tumorigenesis and tumor metastasis, but its exact role in HCC angiogenesis remains poorly understood.

METHODS

qRT-PCR was used to investigate the expression of miR-378a-3p in HCC tissues and cell lines. The effects of miR-378a-3p on HCC in vitro and in vivo were examined by Cell Counting Kit-8 (CCK-8), Transwell, tube formation and Matrigel plug assays, RNA sequencing, bioinformatics, luciferase reporter, immunofluorescence and chromatin immunoprecipitation (ChIP) assays were used to detect the molecular mechanism by which miR-378a-3p inhibits angiogenesis.

RESULTS

We confirmed that miR-378a-3p expression was significantly downregulated and associated with higher microvascular density (MVD) in HCC; miR-378a-3p downregulation indicated a short survival time in HCC patients. miR-378a-3p knockdown led to a significant increase in angiogenesis in vitro and in vivo. We found that miR-378a-3p directly targeted TNF receptor associated factor 1 (TRAF1) to attenuate NF-κB signaling, and then downregulated secreted vascular endothelial growth factor. DNA methyltransferase 1 (DNMT1)-mediated hypermethylation of miR-378a-3p was responsible for downregulating miR-378a-3p. Moreover, a series of investigations indicated that p65 initiated a positive feedback loop that could upregulate DNMT1 to promote hypermethylation of the miR-378a-3p promoter.

CONCLUSION

Our study indicates a novel DNMT1/miR-378a-3p/TRAF1/NF-κB positive feedback loop in HCC cells, which may become a potential therapeutic target for HCC.

Design, Bio-evaluation and Molecular Dynamics Simulation of Novel GSK-3β Inhibitors

Glycogen synthase kinase 3 beta (GSK-3β) is considered as a promising drug target for the treatment of Alzheimer's disease (AD). In the present study, two compound libraries were selected for virtual screening based on pharmacophore models of GSK-3β to discover new inhibitors. Nine potential hits were retained for biological investigation and four of these compounds showed GSK-3β inhibitory activity (with the IC₅₀ values in sub-micromolar range on GSK-3β). Compounds 6 and 9 have good safety. They do not have any significant in vitro cytotoxicity against PC12 and SH-SY5Y neuroblastoma cells at concentrations up to 90 μM. Based on the inhibitory activity and druggability properties, compound 8 is the preferred molecule, and it is a promising lead for the development of the GSK-3β inhibitors for reducing the abnormal hyperphosphorylation of tau protein and relieving AD.

Stability of Imprinting and Differentiation Capacity in Naïve Human Cells Induced by Chemical Inhibition of CDK8 and CDK19

Pluripotent stem cells can be stabilized in vitro at different developmental states by the use of specific chemicals and soluble factors. The naïve and primed states are the best characterized pluripotency states. Naïve pluripotent stem cells (PSCs) correspond to the early pre-implantation blastocyst and, in mice, constitute the optimal starting state for subsequent developmental applications. However, the stabilization of human naïve PSCs remains challenging because, after short-term culture, most current methods result in karyotypic abnormalities, aberrant DNA methylation patterns, loss of imprinting and severely compromised developmental potency. We have recently developed a novel method to induce and stabilize naïve human PSCs that consists in the simple addition of a chemical inhibitor for the closely related CDK8 and CDK19 kinases (CDK8/19i). Long-term cultured CDK8/19i-naïve human PSCs preserve their normal karyotype and do not show widespread DNA demethylation. Here, we investigate the long-term stability of allele-specific methylation at imprinted loci and the differentiation potency of CDK8/19i-naïve human PSCs. We report that long-term cultured CDK8/19i-naïve human PSCs retain the imprinting profile of their parental primed cells, and imprints are further retained upon differentiation in the context of teratoma formation. We have also tested the capacity of long-term cultured CDK8/19i-naïve human PSCs to differentiate into primordial germ cell (PGC)-like cells (PGCLCs) and trophoblast stem cells (TSCs), two cell types that are accessible from the naïve state. Interestingly, long-term cultured CDK8/19i-naïve human PSCs differentiated into PGCLCs with a similar efficiency to their primed counterparts. Also, long-term cultured CDK8/19i-naïve human PSCs were able to differentiate into TSCs, a transition that was not possible for primed PSCs. We conclude that inhibition of CDK8/19 stabilizes human PSCs in a functional naïve state that preserves imprinting and potency over long-term culture.

UHRF1 Is a Novel Druggable Epigenetic Target in Malignant Pleural Mesothelioma

INTRODUCTION

Ubiquitin-like with plant homeodomain and ring finger domains 1 (UHRF1) encodes a master regulator of DNA methylation that has emerged as an epigenetic driver in human cancers. To date, no studies have evaluated UHRF1 expression in malignant pleural mesothelioma (MPM). This study was undertaken to explore the therapeutic potential of targeting UHRF1 in MPM.

METHODS

Microarray, real-time quantitative reverse transcription-polymerase chain reaction, immunoblot, and immunohistochemistry techniques were used to evaluate UHRF1 expression in normal mesothelial cells (NMCs) cultured with or without asbestos, MPM lines, normal pleura, and primary MPM specimens. The impact of UHRF1 expression on MPM patient survival was evaluated using two independent databases. RNA-sequencing, proliferation, invasion, and colony formation assays, and murine xenograft experiments were performed to evaluate gene expression and growth of MPM cells after biochemical or pharmacologic inhibition of UHRF1 expression.

RESULTS

UHRF1 expression was significantly higher in MPM lines and specimens relative to NMC and normal pleura. Asbestos induced UHRF1 expression in NMC. The overexpression of UHRF1 was associated with decreased overall survival in patients with MPM. UHRF1 knockdown reversed genomewide DNA hypomethylation, and inhibited proliferation, invasion, and clonogenicity of MPM cells, and growth of MPM xenografts. These effects were phenocopied by the repurposed chemotherapeutic agent, mithramycin. Biochemical or pharmacologic up-regulation of p53 significantly reduced UHRF1 expression in MPM cells. RNA-sequencing experiments exhibited the pleiotropic effects of UHRF1 down-regulation and identified novel, clinically relevant biomarkers of UHRF1 expression in MPM.

CONCLUSIONS

UHRF1 is an epigenetic driver in MPM. These findings support the efforts to target UHRF1 expression or activity for mesothelioma therapy.

Expression of DNA Methyltransferase 1 Is a Hallmark of Melanoma, Correlating with Proliferation and Response to B-Raf and Mitogen-Activated Protein Kinase Inhibition in Melanocytic Tumors

Aberrant DNA methylation is an epigenetic hallmark of melanoma, but the expression of DNA methyltransferase (Dnmt)-1 in melanocytic tumors is unknown. Dnmt1 expression was analyzed in primary melanocytes, melanoma cell lines, and 83 melanocytic tumors, and its associations with proliferation, mutational status, and response to B-Raf and mitogen-activated protein kinase kinase (MEK) inhibition were explored. Dnmt1 expression was increased incrementally from nevi [mean fluorescence intensity (MFI), 48.1; interquartile range, 41.7 to 59.6] to primary melanomas (MFI, 68.8; interquartile range, 58.4 to 77.0) and metastatic melanomas (MFI, 87.5; interquartile range, 77.1 to 114.5) (P < 0.001). Dnmt1 expression was correlated with Ki-67 expression (Spearman correlation, 0.483; P < 0.001) and was independent of BRAF mutation status (P = 0.55). In BRAF-mutant melanoma, Dnmt1 was down-regulated during response to B-Raf and MEK inhibition and was again up-regulated on drug resistance in vitro and in vivo. Degradation of Dnmt1 by the histone deacetylase inhibitor suberoylanilide hydroxamic acid was associated with decreased cell viability in B-Raf inhibitor-sensitive and -resistant cell lines. This study demonstrates that Dnmt1 expression is correlated with proliferation in melanocytic tumors, is increased with melanoma progression, and is associated with response to B-Raf and MEK inhibition. Given its strong expression in metastatic melanoma, Dnmt1 may be a promising target for combined epigenetic and immunotherapy.

Silencing UHRF1 enhances cell autophagy to prevent articular chondrocytes from apoptosis in osteoarthritis through PI3K/AKT/mTOR signaling pathway

Osteoarthritis (OA) is a common chronic degenerative joint disease, and chondrocyte apoptosis is one of most important pathological changes of OA pathogenesis. Growing studies have shown that Ubiquitin-like with PHD and RING finger domains 1 (UHRF1) is an important epigenetic regulatory factor that regulates cell proliferation and apoptosis of various tumors, but its role in OA remains ill-defined. In the present study, we found that UHRF1 expression was increased in human OA cartilage tissues, compared with normal cartilage tissues. Interleukin-1β (IL-1β), a major inflammatory cytokine that promotes cartilage degradation in OA, was used to stimulate primary human chondrocytes in vitro. The expression of UHRF1 was also enhanced in IL-1β-induced chondrocytes. Moreover, down-regulation of UHRF1 induced an increase on cell proliferation and autophagy, and a decrease on apoptosis of chondrocytes after IL-1β treatment. Further data indicated that silencing UHRF1 attenuated the up-regulation of IL-1β on phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR) signaling pathway in chondrocytes. Then, an activator of PI3K weakened the effect of UHRF1 silencing on cell proliferation, autophagy, apoptosis of IL-1β-induced chondrocytes, and the cell autophagy special inhibitor 3-methyladenine (3-MA) also showed a same impact on UHRF1, hence suggesting that knockdown of UHRF1 enhances cell autophagy to protect chondrocytes from apoptosis in OA through PI3K/AKT/mTOR signaling pathway. In conclusion, our study suggests that UHRF1 may be a potential regulator of chondrocyte apoptosis in the pathogenesis of OA.

The Synergism of PGN, LTA and LPS in Inducing Transcriptome Changes, Inflammatory Responses and a Decrease in Lactation as Well as the Associated Epigenetic Mechanisms in Bovine Mammary Epithelial Cells

Mastitis is usually caused by a variety of pathogenic bacteria that include both Gram-positive and Gram-negative bacteria. Lipopolysaccharide (LPS) is the pathogen-associated molecular pattern (PAMP) of Gram-negative bacteria, and peptidoglycan (PGN) and lipoteichoic acid (LTA) are those of Gram-positive bacteria. The effects of LPS, PGN and/or LTA on inflammatory response and lactation in bovine mammary epithelial cells (BMECs) are well studied, but the epigenetic mechanisms of their effects received less attention. Furthermore, since the three PAMPs are often simultaneously present in the udder of cows with mastitis, it has implications in practice to study their additive effects. The results show that co-stimulation of bovine mammary epithelial cells with PGN, LTA, and LPS induced a higher number of differentially expressed genes (DEGs) and greater expressions of inflammatory factors including interleukin (IL)-1β, IL-6, IL-8, tumor necrosis factor-α (TNF-α), chemokine (C-X-C motif) ligand (CXCL)1, and CXCL6. In addition, co-stimulation further increased DNA hypomethylation compared with sole LPS stimulation. Co-stimulation greatly decreased casein expression but did not further decrease histone acetylation levels and affect the activity of histone acetyltransferase (HAT) and histone deacetylase (HDAC), compared with sole LPS stimulation. Collectively, this study demonstrated that PGN, LTA, and LPS had an additive effect on inducing transcriptome changes and inflammatory responses in BMECs, probably through inducing a greater decrease in DNA methylation. Co-stimulation with PGN, LTA, and LPS decreased casein expression to a greater degree, but it might not be linked to histone acetylation and HAT and HDAC activity.

Low-Frequency Magnetic Fields (LF-MFs) Inhibit Proliferation by Triggering Apoptosis and Altering Cell Cycle Distribution in Breast Cancer Cells

Breast cancer is a common malignancy threatening women’s health around the world. Despite improved treatments for different subtypes of breast tumors that have been put forward, there still exists a poor therapeutic response and prognosis. Magnetic fields, as a non-invasive therapy, have shown anti-tumor effects in vitro and in vivo; however, the detailed mechanisms involved are still not clear. In this study, we found that in exposure to low-frequency magnetic fields (LF-MFs) with an intensity of 1 mT and frequencies of 50, 125, 200, and 275 Hz, separately, the proliferation of breast cancer cells was inhibited and LF-MF with 200 Hz reached the optimum inhibition effect, on exposure time-dependently. Notably, we found that exposure to LF-MF led to MCF-7 and ZR-75-1 cell apoptosis and cell cycle arrest. Moreover, we also discovered that LF-MF effectively increased the level of reactive oxygen species (ROS), suppressed the PI3K/AKT signaling pathway, and activated glycogen synthase kinase-3β (GSK-3β). We demonstrated that the GSK3β activity contributed to LF-MF-induced cell proliferation inhibition and apoptosis, while the underlying mechanism was associated with the inhibition of PI3K/AKT through increasing the intracellular ROS accumulation. These results indicate that LF-MF with a specific frequency may be an attractive therapy to treat breast cancers.

MiR-506 Targets UHRF1 to Inhibit Colorectal Cancer Proliferation and Invasion via the KISS1/PI3K/NF-κB Signaling Axis

Background

The UHRF1 gene is an epigenetic modification factor that mediates tumor suppressor gene silencing in a variety of cancers. Related studies have reported that UHRF1 can inhibit the expression of the KISS1 gene. However, the regulatory mechanism underlying UHRF1 expression in colorectal cancer (CRC) is still unclear. The aim of this study was to gain a better understanding of the regulation of UHRF1 expression in CRC and to determine whether it regulates the mechanism by which KISS1 promotes CRC metastasis.

Methods

In the present study, the levels of miR-506, UHRF1 and KISS1 expression in CRC tissues and in human CRC cell lines were studied using quantitative real-time PCR (qRT-PCR) and Western blotting. Cell proliferation, migration, and invasion assays are used to detect cell proliferation, migration, and invasion. A dual-luciferase reporter system was used to confirm the target gene of miR-506.

Results

This study found that UHRF1 protein is highly expressed in CRC tissues and negatively correlated with KISS1 protein expression. UHRF1 overexpression activates the PI3K/NF-κB signaling pathway by inhibiting the mRNA expression levels of pathway mediators. Bioinformatics analysis and luciferase reporter gene assays confirmed that miR-506 targets UHRF1.

Conclusion

This study identified the regulation of UHRF1 expression in CRC and the mechanism of CRC metastasis. UHRF1 may be a new potential target molecule for future CRC metastasis treatment.

DNA hypermethylation in disease: mechanisms and clinical relevance

Increasing numbers of studies implicate abnormal DNA methylation in cancer and many non-malignant diseases. This is consistent with numerous findings about differentiation-associated changes in DNA methylation at promoters, enhancers, gene bodies, and sites that control higher-order chromatin structure. Abnormal increases or decreases in DNA methylation contribute to or are markers for cancer formation and tumour progression. Aberrant DNA methylation is also associated with neurological diseases, immunological diseases, atherosclerosis, and osteoporosis. In this review, I discuss DNA hypermethylation in disease and its interrelationships with normal development as well as proposed mechanisms for the origin of and pathogenic consequences of disease-associated hypermethylation. Disease-linked DNA hypermethylation can help drive oncogenesis partly by its effects on cancer stem cells and by the CpG island methylator phenotype (CIMP); atherosclerosis by disease-related cell transdifferentiation; autoimmune and neurological diseases through abnormal perturbations of cell memory; and diverse age-associated diseases by age-related accumulation of epigenetic alterations.