G9a Inhibition Induces Autophagic Cell Death via AMPK/mTOR Pathway in Bladder Transitional Cell Carcinoma

Targeting histone modifiers in bladder cancer therapy - preclinical and clinical evidence

Bladder cancer in the most advanced, muscle-invasive stage is lethal, and very limited therapeutic advances have been reported for decades. To date, cisplatin-based chemotherapy remains the first-line therapy for advanced bladder cancer. Late-line options have historically been limited. In the past few years, next-generation sequencing technology has enabled chromatin remodelling gene mutations to be characterized, showing that these alterations are more frequent in urothelial bladder carcinoma than in other cancer types. Histone modifiers have functional roles in tumour progression by modulating the expression of tumour suppressors and oncogenes and, therefore, have been considered as novel drug targets for cancer therapy. The roles of epigenetic reprogramming through histone modifications have been increasingly studied in bladder cancer, and the therapeutic efficacy of targeting those histone modifiers genetically or chemically is being assessed in preclinical studies. Results from preclinical studies in bladder cancer encouraged the investigation of some of these drugs in clinical trials, which yield mixed results. Further understanding of how alterations of histone modification mechanistically contribute to bladder cancer progression, drug resistance and tumour microenvironment remodelling will be required to facilitate clinical application of epigenetic drugs in bladder cancer.

Alternative splicing regulation and its therapeutic potential in bladder cancer

Bladder cancer is one of the leading causes of mortality globally. The development of bladder cancer is closely associated with alternative splicing, which regulates human gene expression and enhances the diversity of functional proteins. Alternative splicing is a distinctive feature of bladder cancer, and as such, it may hold promise as a therapeutic target. This review aims to comprehensively discuss the current knowledge of alternative splicing in the context of bladder cancer. We review the process of alternative splicing and its regulation in bladder cancer. Moreover, we emphasize the significance of abnormal alternative splicing and splicing factor irregularities during bladder cancer progression. Finally, we explore the impact of alternative splicing on bladder cancer drug resistance and the potential of alternative splicing as a therapeutic target.

The exploitation of host autophagy and ubiquitin machinery by Mycobacterium tuberculosis in shaping immune responses and host defense during infection

Intracellular pathogens have evolved various efficient molecular armaments to subvert innate defenses. Cellular ubiquitination, a normal physiological process to maintain homeostasis, is emerging one such exploited mechanism. Ubiquitin (Ub), a small protein modifier, is conjugated to diverse protein substrates to regulate many functions. Structurally diverse linkages of poly-Ub to target proteins allow enormous functional diversity with specificity being governed by evolutionarily conserved enzymes (E3-Ub ligases). The Ub-binding domain (UBD) and LC3-interacting region (LIR) are critical features of macroautophagy/autophagy receptors that recognize Ub-conjugated on protein substrates. Emerging evidence suggests that E3-Ub ligases unexpectedly protect against intracellular pathogens by tagging poly-Ub on their surfaces and targeting them to phagophores. Two E3-Ub ligases, PRKN and SMURF1, provide immunity against Mycobacterium tuberculosis (M. tb). Both enzymes conjugate K63 and K48-linked poly-Ub to M. tb for successful delivery to phagophores. Intriguingly, M. tb exploits virulence factors to effectively dampen host-directed autophagy utilizing diverse mechanisms. Autophagy receptors contain LIR-motifs that interact with conserved Atg8-family proteins to modulate phagophore biogenesis and fusion to the lysosome. Intracellular pathogens have evolved a vast repertoire of virulence effectors to subdue host-immunity via hijacking the host ubiquitination process. This review highlights the xenophagy-mediated clearance of M. tb involving host E3-Ub ligases and counter-strategy of autophagy inhibition by M. tb using virulence factors. The role of Ub-binding receptors and their mode of autophagy regulation is also explained. We also discuss the co-opting and utilization of the host Ub system by M. tb for its survival and virulence.Abbreviations: APC: anaphase promoting complex/cyclosome; ATG5: autophagy related 5; BCG: bacille Calmette-Guerin; C2: Ca²⁺-binding motif; CALCOCO2: calcium binding and coiled-coil domain 2; CUE: coupling of ubiquitin conjugation to ER degradation domains; DUB: deubiquitinating enzyme; GABARAP: GABA type A receptor-associated protein; HECT: homologous to the E6-AP carboxyl terminus; IBR: in-between-ring fingers; IFN: interferon; IL1B: interleukin 1 beta; KEAP1: kelch like ECH associated protein 1; LAMP1: lysosomal associated membrane protein 1; LGALS: galectin; LIR: LC3-interacting region; MAPK11/p38: mitogen-activated protein kinase 11; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MAP3K7/TAK1: mitogen-activated protein kinase kinase kinase 7; MAPK8/JNK: mitogen-activated protein kinase 8; MHC-II: major histocompatibility complex-II; MTOR: mechanistic target of rapamycin kinase; NBR1: NBR1 autophagy cargo receptor; NFKB1/p50: nuclear factor kappa B subunit 1; OPTN: optineurin; PB1: phox and bem 1; PE/PPE: proline-glutamic acid/proline-proline-glutamic acid; PknG: serine/threonine-protein kinase PknG; PRKN: parkin RBR E3 ubiquitin protein ligase; RBR: RING-in between RING; RING: really interesting new gene; RNF166: RING finger protein 166; ROS: reactive oxygen species; SMURF1: SMAD specific E3 ubiquitin protein ligase 1; SQSTM1: sequestosome 1; STING1: stimulator of interferon response cGAMP interactor 1; TAX1BP1: Tax1 binding protein 1; TBK1: TANK binding kinase 1; TNF: tumor necrosis factor; TRAF6: TNF receptor associated factor 6; Ub: ubiquitin; UBA: ubiquitin-associated; UBAN: ubiquitin-binding domain in ABIN proteins and NEMO; UBD: ubiquitin-binding domain; UBL: ubiquitin-like; ULK1: unc-51 like autophagy activating kinase 1.

Cognitive Decline and BPSD Are Concomitant with Autophagic and Synaptic Deficits Associated with G9a Alterations in Aged SAMP8 Mice

Behavioural and psychological symptoms of dementia (BPSD) are presented in 95% of Alzheimer’s Disease (AD) patients and are also associated with neurotrophin deficits. The molecular mechanisms leading to age-related diseases are still unclear; however, emerging evidence has suggested that epigenetic modulation is a key pathophysiological basis of ageing and neurodegeneration. In particular, it has been suggested that G9a methyltransferase and its repressive histone mark (H3K9me2) are important in shaping learning and memory by modulating autophagic activity and synaptic plasticity. This work deepens our understanding of the epigenetic mechanisms underlying the loss of cognitive function and BPSD in AD. For this purpose, several tasks were performed to evaluate the parameters of sociability (three-chamber test), aggressiveness (resident intruder), anxiety (elevated plus maze and open field) and memory (novel object recognition test) in mice, followed by the evaluation of epigenetic, autophagy and synaptic plasticity markers at the molecular level. The behavioural alterations presented by senescence-accelerated mice prone 8 (SAMP8) of 12 months of age compared with their senescence-accelerated mouse resistant mice (SAMR1), the healthy control strain was accompanied by age-related cognitive deficits and alterations in epigenetic markers. Increased levels of G9a are concomitant to the dysregulation of the JNK pathway in aged SAMP8, driving a failure in autophagosome formation. Furthermore, lower expression of the genes involved in the memory-consolidation process modulated by ERK was observed in the aged male SAMP8 model, suggesting the implication of G9a. In any case, two of the most important neurotrophins, namely brain-derived neurotrophic factor (Bdnf) and neurotrophin-3 (NT3), were found to be reduced, along with a decrease in the levels of dendritic branching and spine density presented by SAMP8 mice. Thus, the present study characterizes and provides information regarding the non-cognitive and cognitive states, as well as molecular alterations, in aged SAMP8, demonstrating the AD-like symptoms presented by this model. In any case, our results indicate that higher levels of G9a are associated with autophagic deficits and alterations in synaptic plasticity, which could further explain the BPSD and cognitive decline exhibited by the model.

Role of Chromatin Modifying Complexes and Therapeutic Opportunities in Bladder Cancer

BACKGROUND

Chromatin modifying enzymes, mainly through post translational modifications, regulate chromatin architecture and by extension the underlying transcriptional kinetics in normal and malignant cells. Muscle invasive bladder cancer (MIBC) has a high frequency of alterations in chromatin modifiers, with 76% of tumors exhibiting mutation in at least one chromatin modifying enzyme [1]. Additionally, clonal expansion of cells with inactivating mutations in chromatin modifiers has been identified in the normal urothelium, pointing to a currently unknown role of these proteins in normal bladder homeostasis.

OBJECTIVE

To review current knowledge of chromatin modifications and enzymes regulating these processes in Bladder cancer (BCa).

METHODS

By reviewing current literature, we summarize our present knowledge of external stimuli that trigger loss of equilibrium in the chromatin accessibility landscape and emerging therapeutic interventions for targeting these processes.

RESULTS

Genetic lesions in BCa lead to altered function of chromatin modifying enzymes, resulting in coordinated dysregulation of epigenetic processes with disease progression.

CONCLUSION

Mutations in chromatin modifying enzymes are wide-spread in BCa and several promising therapeutic targets for modulating activity of these genes are currently in clinical trials. Further research into understanding how the epigenetic landscape evolves as the disease progresses, could help identify patients who might benefit the most from these targeted therapies.

Prediction of Prognosis and Recurrence of Bladder Cancer by ECM-Related Genes

Background

Bladder cancer (BLCA) is one of the most common cancers and ranks ninth among all cancers. Extracellular matrix (ECM) genes activate a number of pathways that facilitate tumor development. This study is aimed at providing models to predict BLCA survival and recurrence by ECM genes.

Methods

Expression data from BLCA samples in GSE32894, GSE13507, GSE31684, GSE32548, and TCGA-BLCA cohorts were downloaded and analyzed. The ECM-related genes were obtained by differentially expressed gene analysis, stage-associated gene analysis, and random forest variable selection. The ECM was constructed in GSE32894 by the hub ECM-related genes and validated in GSE13507, GSE31684, GSE32548, and TCGA-BLCA cohorts. The correlations of the ECM score with cells (T cells, fibroblasts, etc.) and the response to immunotherapeutic drugs were investigated. Four machine learning models were selected and used to construct models to predict the recurrence of BLCA. A total of 15 paired BLCA and normal tissue specimens, human immortalized uroepithelial cell lines, and bladder cancer cell lines were selected for the validation of the difference in expression of FSTL1 between normal tissues and BLCA.

Results

Six ECM genes (CTHRC1, MMP11, COL10A1, FSTL1, SULF1, and COL5A3) were recognized to be the hub ECM-related genes. The ECM score of each BLCA patient was calculated using these six selected ECM-related genes. BLCA patients with a high ECM score group had significantly lower overall survival rates than patients in the low ECM score group. We found that the ECM score was positively associated with immune cells and fibroblasts and negatively correlated with tumor purity. When treated with immunotherapy, BLCA patients with a high ECM score presented a high response rate and better prognosis. We also found that the combination of FSTL1, stage, age, and gender achieved an AUC value of 0.76 in predicting bladder cancer recurrence. Based on the RT-qPCR results of FSTL1 gene expression, there was an overall decrease in the mRNA expression of FSTL1 in cancer tissues compared to their adjacent normal tissues. Subsequent in vitro validation demonstrated that the FSTL1 expression was downregulated at the gene and protein level compared to that in SVH cells.

Conclusion

Taken together, our results indicate that ECM-related genes correlate with immune cells, overall survival, and recurrence of BLCA. This study provides a machine learning model for predicting the survival and recurrence of BLCA patients.

Selective histone methyltransferase G9a inhibition reduces metastatic development of Ewing sarcoma through the epigenetic regulation of NEU1

Ewing sarcoma (EWS) is an aggressive bone and soft tissue tumor with high susceptibility to metastasize. The underlying molecular mechanisms leading to EWS metastases remain poorly understood. Epigenetic changes have been implicated in EWS tumor growth and progression. Linking epigenetics and metastases may provide insight into novel molecular targets in EWS and improve its treatment. Here, we evaluated the effects of a selective G9a histone methyltransferase inhibitor (BIX01294) on EWS metastatic process. Our results showed that overexpression of G9a in tumors from EWS patients correlates with poor prognosis. Moreover, we observe a significantly higher expression of G9a in metastatic EWS tumor as compared to either primary or recurrent tumor. Using functional assays, we demonstrate that pharmacological G9a inhibition using BIX01294 disrupts several metastatic steps in vitro, such as migration, invasion, adhesion, colony formation and vasculogenic mimicry. Moreover, BIX01294 reduces tumor growth and metastases in two spontaneous metastases mouse models. We further identified the sialidase NEU1 as a direct target and effector of G9a in the metastatic process in EWS. NEU1 overexpression impairs migration, invasion and clonogenic capacity of EWS cell lines. Overall, G9a inhibition impairs metastases in vitro and in vivo through the overexpression of NEU1. G9a has strong potential as a prognostic marker and may be a promising therapeutic target for EWS patients.

Cinnamaldehyde induces autophagy-mediated cell death through ER stress and epigenetic modification in gastric cancer cells

Previous reports suggested that cinnamaldehyde (CA), the bioactive ingredient in Cinnamomum cassia, can suppress tumor growth, migratory, and invasive abilities. However, the role and molecular mechanisms of CA in GC are not completely understood. In the present study, we found that CA-induced ER stress and cell death via the PERK-CHOP axis and Ca²⁺ release in GC cells. Inhibition of ER stress using specific-siRNA blocked CA-induced cell death. Interestingly, CA treatment resulted in autophagic cell death by inducing Beclin-1, ATG5, and LC3B expression and by inhibiting p62 expression whereas autophagy inhibition suppressed CA-induced cell death. We showed that CA induces the inhibition of G9a and the activation of LC3B. Moreover, CA inhibited G9a binding on Beclin-1 and LC3B promoter. Overall, these results suggested that CA regulates the PERK-CHOP signaling, and G9a inhibition activates autophagic cell death via ER stress in GC cells.

Regulation of autophagy by protein methylation and acetylation in cancer

Autophagy is a highly conserved mechanism responsible for cellular homeostasis and integrity in a variety of physiological conditions. Materials targeted for degradation are directed to autophagosomes and autolysosomes, where they are broken down into their base components. Aberrant regulation of autophagy is significantly associated with various cancers and neurodegenerative diseases. Recently, accumulating evidence has revealed that the coordinated regulation of histone and non-histone protein modification is associated with autophagy. In this review, we highlight the recent progress that has been made in elucidating the molecular basis of protein methylation and acetylation associated with autophagy at the transcriptional and posttranslational levels. Furthermore, we discuss the importance of describing causality between protein methylation/acetylation and autophagy regulation as compelling therapeutic opportunities in cancer pathogenesis and progression.

Epigenetic regulation of autophagy: A key modification in cancer cells and cancer stem cells

Aberrant epigenetic alterations play a decisive role in cancer initiation and propagation via the regulation of key tumor suppressor genes and oncogenes or by modulation of essential signaling pathways. Autophagy is a highly regulated mechanism required for the recycling and degradation of surplus and damaged cytoplasmic constituents in a lysosome dependent manner. In cancer, autophagy has a divergent role. For instance, autophagy elicits tumor promoting functions by facilitating metabolic adaption and plasticity in cancer stem cells (CSCs) and cancer cells. Moreover, autophagy exerts pro-survival mechanisms to these cancerous cells by influencing survival, dormancy, immunosurveillance, invasion, metastasis, and resistance to anti-cancer therapies. In addition, recent studies have demonstrated that various tumor suppressor genes and oncogenes involved in autophagy, are tightly regulated via different epigenetic modifications, such as DNA methylation, histone modifications and non-coding RNAs. The impact of epigenetic regulation of autophagy in cancer cells and CSCs is not well-understood. Therefore, uncovering the complex mechanism of epigenetic regulation of autophagy provides an opportunity to improve and discover novel cancer therapeutics. Subsequently, this would aid in improving clinical outcome for cancer patients. In this review, we provide a comprehensive overview of the existing knowledge available on epigenetic regulation of autophagy and its importance in the maintenance and homeostasis of CSCs and cancer cells.

Evaluation of anti-cancer potency of silibinin on murine renal carcinoma RenCa cells in an animal model with an intact immune system

Silibinin is a flavonoid extract isolated from milk thistle and has been proved to be a promising chemotherapeutic drug for cancer. However, most of those studies were performed on the human cancer cells, where the effects of silibinin could only be observed on an animal model with a deficient immune system. RenCa cells were isolated from a murine spontaneous renal cell carcinoma, which resembles many features of human renal cell carcinoma, and have been used to establish animal models with a sound immune response. Herein, we investigated the anti-cancer effects of silibinin on RenCa cells, revealing that it inhibited cell viability in both dose- and time-dependent manners. Silibinin slightly triggered apoptosis and significantly induced G2-M cell cycle arrest by downregulating cyclin B1 and CDK1 and increasing expression of p21. Furthermore, silibinin significantly inhibited the growth of RenCa cell xenografts in vivo. In addition, we found that silibinin reduced programmed cell death 1 ligand 1 expression of RenCa cells in vivo and in vitro. Our findings demonstrate that silibinin can inhibit the growth of mouse tumor cells in an animal model with an intact immune system, and silibinin may decrease the immunosuppression effect of tumor cells. Our results provide new evidence for evaluation of Silibinin application in cancer therapy.

Epigenetic Regulation of Autophagy Beyond the Cytoplasm: A Review

Autophagy is a highly conserved catabolic process induced under various stress conditions to protect the cell from harm and allow survival in the face of nutrient- or energy-deficient states. Regulation of autophagy is complex, as cells need to adapt to a continuously changing microenvironment. It is well recognized that the AMPK and mTOR signaling pathways are the main regulators of autophagy. However, various other signaling pathways have also been described to regulate the autophagic process. A better understanding of these complex autophagy regulatory mechanisms will allow the discovery of new potential therapeutic targets. Here, we present a brief overview of autophagy and its regulatory pathways with emphasis on the epigenetic control mechanisms.

BIX-01294, a G9a inhibitor, suppresses cell proliferation by inhibiting autophagic flux in nasopharyngeal carcinoma cells

G9a, a histone methyltransferase, has been found to be upregulated in a range of tumor tissues, and contributes to tumor growth and metastasis. However, the impact of G9a inhibition as a potential therapeutic target in nasopharyngeal carcinoma (NPC) is unclear. In the present study we aimed to investigate the anti-proliferative effect of G9a inhibition in the NPC cell lines CNE1 and CNE2, and to further elucidate the molecular mechanisms underlying these effects. The expression of G9a in NPC tumor tissues was significantly higher than that in normal nasopharyngeal tissues. The pharmacological inhibition of G9a by BIX-01294 (BIX) inhibited proliferation and induced caspase-independent apoptosis in NPC cells in vitro. Treatment with BIX induced autophagosome accumulation, which exacerbated the cytotoxic activity of BIX in NPC cells. Mechanistic studies have found that BIX impairs autophagosomes by initiating autophagy in a Beclin-1-independent way, and impairs autophagic degradation by inhibiting lysosomal cathepsin D activation, leading to lysosomal dysfunction. BIX was able to suppress tumor growth, possibly by inhibiting autophagic flux; it might therefore constitute a promising candidate for NPC therapy.

G9a/GLP targeting in MM promotes autophagy-associated apoptosis and boosts proteasome inhibitor-mediated cell death

Multiple myeloma (MM) is an (epi)genetic highly heterogeneous plasma cell malignancy that remains mostly incurable. Deregulated expression and/or genetic defects in epigenetic-modifying enzymes contribute to high-risk disease and MM progression. Overexpression of the histone methyltransferase G9a was reported in several cancers, including MM, correlating with disease progression, metastasis, and poor prognosis. However, the exact role of G9a and its interaction partner G9a-like protein (GLP) in MM biology and the underlying mechanisms of action remain poorly understood. Here, we report that high G9a RNA levels are associated with a worse disease outcome in newly diagnosed and relapsed MM patients. G9a/GLP targeting using the specific G9a/GLP inhibitors BIX01294 and UNC0638 induces a G1-phase arrest and apoptosis in MM cell lines and reduces primary MM cell viability. Mechanistic studies revealed that G9a/GLP targeting promotes autophagy-associated apoptosis by inactivating the mTOR/4EBP1 pathway and reducing c-MYC levels. Moreover, genes deregulated by G9a/GLP targeting are associated with repressive histone marks. G9a/GLP targeting sensitizes MM cells to the proteasome inhibitors (PIs) bortezomib and carfilzomib, by (further) reducing mTOR signaling and c-MYC levels and activating p-38 and SAPK/JNK signaling. Therapeutic treatment of 5TGM1 mice with BIX01294 delayed in vivo MM tumor growth, and cotreatment with bortezomib resulted in a further reduction in tumor burden and a significantly prolonged survival. In conclusion, we provide evidence that the histone methyltransferases G9a/GLP support MM cell growth and survival by blocking basal autophagy and sustaining high c-MYC levels. G9a/GLP targeting represents a promising strategy to improve PI-based treatment in patients with high G9a/GLP levels.

G9a Inhibition Enhances Checkpoint Inhibitor Blockade Response in Melanoma

PURPOSE

G9a histone methyltransferase exerts oncogenic effects in several tumor types and its inhibition promotes anticancer effects. However, the impact on checkpoint inhibitor blockade response and the utility of G9a or its target genes as a biomarker is poorly studied. We aimed to examine whether G9a inhibition can augment the efficacy of checkpoint inhibitor blockade and whether LC3B, a G9a target gene, can predict treatment response.

EXPERIMENTAL DESIGN

Clinical potential of LC3B as a biomarker of checkpoint inhibitor blockade was assessed using patient samples including tumor biopsies and circulating tumor cells from liquid biopsies. Efficacy of G9a inhibition to enhance checkpoint inhibitor blockade was examined using a mouse model.

RESULTS

Patients with melanoma who responded to checkpoint inhibitor blockade were associated with not only a higher level of tumor LC3B but also a higher proportion of cells expressing LC3B. A higher expression of MAP1LC3B or LC3B protein was associated with longer survival and lower incidence of acquired resistance to checkpoint inhibitor blockade, suggesting LC3B as a potential predictive biomarker. We demonstrate that G9a histone methyltransferase inhibition is able to not only robustly induce LC3B level to augment the efficacy of checkpoint inhibitor blockade, but also induces melanoma cell death.

CONCLUSIONS

Checkpoint inhibitor blockade response is limited to a subset of the patient population. These results have implications for the development of LC3B as a predictive biomarker of checkpoint inhibitor blockade to guide patient selection, as well as G9a inhibition as a strategy to extend the proportion of patients responding to immunotherapy.

Insight into the multi-faceted role of the SUV family of H3K9 methyltransferases in carcinogenesis and cancer progression

Growing evidence implicates histone H3 lysine 9 methylation in tumorigenesis. The SUV family of H3K9 methyltransferases, which include G9a, GLP, SETDB1, SETDB2, SUV39H1 and SUV39H2 deposit H3K9me1/2/3 marks at euchromatic and heterochromatic regions, catalyzed by their conserved SET domain. In cancer, this family of enzymes can be deregulated by genomic alterations and transcriptional mis-expression leading to alteration of transcriptional programs. In solid and hematological malignancies, studies have uncovered pro-oncogenic roles for several H3K9 methyltransferases and accordingly, small molecule inhibitors are being tested as potential therapies. However, emerging evidence demonstrate onco-suppressive roles for these enzymes in cancer development as well. Here, we review the role H3K9 methyltransferases play in tumorigenesis focusing on gene targets and biological pathways affected due to misregulation of these enzymes. We also discuss molecular mechanisms regulating H3K9 methyltransferases and their influence on cancer. Finally, we describe the impact of H3K9 methylation on therapy induced resistance in carcinoma. Converging evidence point to multi-faceted roles for H3K9 methyltransferases in development and cancer that encourages a deeper understanding of these enzymes to inform novel therapy.

Contrast effects of autophagy in the treatment of bladder cancer

Bladder cancer is a disease that negatively affects patients' quality of life, but treatment options have remained unchanged for a long time. Although promising results have been achieved with current bladder cancer treatments, cancer recurrence, progression, and therapy resistance are the most severe problems preventing the efficiency of bladder cancer treatments. Autophagy refers to an evolutionarily conserved catabolic process in which proteins, damaged organelles, and cytoplasmic components are degraded by lysosomal enzymes. Autophagy regulates the therapeutic response to the chemotherapy drugs, thus determining the effect of therapy on cancer cells. Autophagy is a stress-induced cell survival mechanism and its excessive stimulation can cause resistance of tumor cells to therapeutic agents. Depending on the conditions, an increase in autophagy may cause treatment resistance or autophagic cell death, and it is related to important anti-cancer mechanisms, such as apoptosis. Therefore, understanding the roles of autophagy under different conditions is important for designing effective anti-cancer agents. The dual role of autophagy in cancer has attracted considerable attention in respect of bladder cancer treatment. In this review, we summarize the basic characteristics of autophagy, including its mechanisms, regulation, and functions, and we present examples from current studies concerning the dual role of autophagy in bladder cancer progression and therapy.

The combination of G9a histone methyltransferase inhibitors with erythropoietin protects heart against damage from acute myocardial infarction

BACKGROUND

This study tested the hypothesis that combined histone methyltransferase G9a inhibitor (i.e., UNC0638) and erythropoietin (EPO) was superior to either one alone for protecting myocardium from acute myocardial infarction (AMI) damage.

METHODS AND RESULTS

Adult-male SD rats (n=30) were equally categorized into group 1 (sham-operated control), group 2 (AMI), group 3 (AMI-EPO/1000 IU/kg, I.M./3 h after AMI), group 4 (AMI- UNC0638/5 mg/kg I.P./3 h after AMI) and group 5 [AMI-UNC0638-EPO 3 h after AMI] treatment. Animals were euthanized at day 21 after AMI induction. By day 21, left-ventricular-ejection-fraction (LVEF) was highest in group 1, lowest in group 2, significantly higher in group 5 than in groups 3 and 4, but no difference between the latter two groups (all P<0.0001). The protein expressions of inflammatory (MMP-2/MM-9), fibrotic (fibronectin/Smad3/TGF-ß), apoptotic/DNA-damaged (caspas-3/PARP/γ-H2AX), cell-stress response (HIF-1α/p-Akt/p-mTOR) and autophagic (beclin-1/ratio of LC3B-II to LC3B-I) biomarkers exhibited an opposite pattern, whereas the protein expressions of endothelial integrity (CD31/vWF) and anti-oxidant (SIRT1/SIRT3) exhibited an identical pattern of LVEF among the five groups (all P<0.0001). The protein expressions (SDF-1α/VEGF/CXCR4) and cellular expressions (C-kit/CD31+//Sca-1/CD31+//KDR/CD34+) of angiogenesis biomarkers were significantly progressively increased from groups 1 to 5 (all P<0.0001). The infarction/fibrotic areas, myocyte size and number of G9a cells exhibited an opposite pattern, whereas the small-vessel density displayed an identical trend of LVEF among the groups (all P<0.0001). Flow cytometric analysis showed cellular levels of inflammation (Ly6G+/MPO+/CD11b/c+), oxidative-stress (DCFDA+) and apoptosis (early+/late+) exhibited an opposite pattern to LVEF among the groups (all P<0.0001).

CONCLUSION

EPO-BIX01294 effectively protected myocardium against AMI-induced damage.

SPAG6 silencing induces autophagic cell death in SKM-1 cells via the AMPK/mTOR/ULK1 signaling pathway

As a member of the cancer-testis antigen family, sperm-associated antigen 6 (SPAG6) has been reported to be associated with the pathogenesis of myelodysplastic syndromes (MDS). Previous studies have demonstrated that SPAG6 is upregulated in bone marrow from patients with MDS and MDS-transformed acute myeloid leukemia and that knockdown of SPAG6 expression levels suppressed proliferation and promote apoptosis and differentiation in SKM-1 cells. However, the association between SPAG6 and autophagy in SKM-1 cells remains unclear. Hence, the aim of the present study was to investigate this association and its underlying mechanism. The present study used a short hairpin RNA (shRNA) lentivirus to silence SPAG6 expression levels in SKM-1 cells and demonstrated that SPAG6 knockdown increased autophagy and apoptosis. Furthermore, pharmacologically inhibiting autophagy with chloroquine and 3-methyladenine decreased SPAG6 knockdown-mediated apoptosis, indicating that SPAG6 knockdown-mediated autophagy promoted apoptosis in SKM-1 cells. Additionally, compared with the expression levels in negative control-shRNA lentivirus-transfected SKM-1 cells, the protein expression levels of phosphorylated AMP-activated protein kinase (p-AMPK) and phosphorylated unc-51-like autophagy activating kinase 1 (p-ULK1) were upregulated, while phosphorylated mammalian target of rapamycin (p-mTOR) protein expression was downregulated in SPAG6-shRNA lentivirus-transfected cells. Moreover, inhibiting AMPK expression levels with Compound C, a specific inhibitor of AMPK, attenuated SPAG6 knockdown-induced autophagy and apoptosis, suggesting that AMPK-mediated autophagy enhanced the pro-apoptotic effect of SPAG6 knockdown in SKM-1 cells. Taken together, the results of the present study demonstrated that SPAG6 silencing triggered autophagy via regulation of the AMPK/mTOR/ULK1 signaling pathway, which further contributed to the apoptosis of SKM-1 cells induced by SPAG6 knockdown. Thus, the current results indicate that SPAG6 may be a potential therapeutic target against MDS, and that autophagy may represent a potential mechanism for the treatment of MDS.

EHMT2/G9a Inhibits Aortic Smooth Muscle Cell Death by Suppressing Autophagy Activation

Although EHMT2 (also known as G9a) plays a critical role in several kinds of cancers and cardiac remodeling, its function in vascular smooth muscle cells (VSMCs) remains unknown. In the present study, we revealed a novel function of EHMT2 in regulating autophagic cell death (ACD) of VSMC. Inhibition of EHMT2 by BIX01294 or knockdown of EHMT2 resulted in reduced VSMC numbers which were independent of proliferation and apoptosis. Interestingly, EHMT2 protein levels were significantly decreased in VSMCs treated with autophagic inducers. Moreover, more autophagic vacuoles and accumulated LC3II were detected in VSMCs treated with BIX01294 or lenti-shEHMT2 than their counterparts. Furthermore, we found that EHMT2 inhibited the ACD of VSMCs by suppressing autophagosome formation. Mechanistically, the pro-autophagic effect elicited by EHMT2 inhibition was associated with SQSTM1 and BECN1 overexpression. Moreover, these detrimental effects were largely nullified by SQSTM1 or BECN1 knockdown. More importantly, similar results were observed in primary human aortic VSMCs. Overall, these findings suggest that EHMT2 functions as a crucial negative regulator of ACD via decreasing SQSTM1 or BECN1 expression and that EHMT2 could be a potent therapeutic target for cardiovascular diseases (e.g., aortic dissection).

Targeting the Immune system and Epigenetic Landscape of Urological Tumors

In the last years, we have witnessed remarkable advances in targeted therapies for cancer patients. There is a growing effort to either replace or reduce the dose of unspecific, systemic (chemo)therapies, given the associated short- and long-term side effects, by introducing more specific targeted therapies as single or combination agents. Due to the well-known implications of the immune system and epigenetic landscape in modulating cancer development, both have been explored as potential targets in several malignancies, including those affecting the genitourinary tract. As the immune system function is also epigenetically regulated, there is rationale for combining both strategies. However, this is still rather underexplored, namely in urological tumors. We aim to briefly review the use of immune therapies in prostate, kidney, bladder, and testicular cancer, and further describe studies providing supporting evidence on their combination with epigenetic-based therapies.

Upregulated expression of G9a is correlated with poor prognosis of gastric cancer patients

As one of the most serious cancers, gastric cancer (GC) represents the third leading cause of malignancy-related deaths. G9a is a histone lysine methyltransferase and has been reported to be involved in the progression of some human cancers. In the present study, we aimed to explore the expression patterns and clinical value of G9a in GC patients.The expression of G9a in 142 paired GC tissues and adjacent non-cancerous tissues (no less than 5 cm from tumor edge) was examined with quantitative real-time polymerase chain reaction (qRT-PCR). To estimate the association of G9a expression with clinical characteristics of GC patients, Chi-square test and t test were conducted. Kaplan-Meier survival and multivariate Cox regression analyses were performed to explore the prognostic value of G9a in GC.Upregulated expression of G9a was found in GC tissues compared with noncancerous tissues (P < .001). Elevated G9a expression was significantly correlated with patients' lymph node metastasis (P = .007) and TNM stage (P < .001). Kaplan-Meier survival curves demonstrated that patients with high G9a expression had shorter survival time than those with low expression (log-rank test, P < .05), reaching a median OS of 24 months. According to the results of Cox regression, G9a could be considered as an independent prognostic biomarker in patients with GC (HR = 3.912, 95% CI = 2.213-6.915, P < .001). Additionally, the diagnosis cut-off value of G9a in GC patients was 1.515.Taken together, G9a expression was upregulated in GC tissues and could be an effective prognostic biomarker for GC.

G9a promotes cell proliferation and suppresses autophagy in gastric cancer by directly activating mTOR

As an important methyltransferase, G9a has been reported to be abnormally expressed in various human cancers and plays essential roles in tumorigenesis. However, the biologic functions and molecular mechanisms of G9a in gastric cancer (GC) remain unclear. GC is the fifth most frequent cancer around the world and seriously threatens human health, especially in developing countries. Here, our results showed that high expression of G9a was intensively correlated with poor prognosis and more advanced stages of GCs. Knockdown of G9a or treatment with its inhibitor, BIX01294, significantly reduced cell growth by cell cycle arrest and autophagy. In addition, the mechanistic target of rapamycin (mTOR) was evidently decreased after G9a silencing or inhibition, and mTOR activation partially rescued the effects of cell proliferation inhibition and autophagy induced by G9a knockdown or inhibition. Down-regulation of G9a effectively inhibited mTOR expression and tumor growth in the xenograft tumor model of GC cells. We also showed that G9a regulates mTOR and cell proliferation and autophagy depending on its histone methylase activity. Using chromatin immunoprecipitation analysis, we found that mTOR expression was associated with promoter methylation and an enrichment for mono- and dimethylated histone 3 lys 9 (H3K9). G9a knockdown revealed an apparent decrease in H3K9 monomethylation levels, but no apparent change in H3K9 dimethylation levels at the mTOR promoter. These results indicate that G9a is a novel and promising therapeutic target for GC treatment.-Yin, C., Ke, X., Zhang, R., Hou, J., Dong, Z., Wang, F., Zhang, K., Zhong, X., Yang, L., Cui, H. G9a promotes cell proliferation and suppresses autophagy in gastric cancer by directly activating mTOR.

Protein methylation functions as the posttranslational modification switch to regulate autophagy

Studies over the past decades have elucidated the critical role of autophagy in human health and diseases. Although the processes of autophagy in the cytoplasm have been well studied, the posttranscriptional and epigenetic regulation mechanisms of autophagy are still poorly understood. Protein methylation, including histone methylation and non-histone protein methylation, is the most important type of posttranscriptional and epigenetic modification. Recent studies have shown that protein methylation is associated with effects on autophagosome formation, autophagy-related protein expression, and signaling pathway activation, but the details are still unclear. Thus, it is important to summarize the current status and discuss the future directions of research on protein methylation in the context of autophagy.

Metformin targets a YAP1-TEAD4 complex via AMPKα to regulate CCNE1/2 in bladder cancer cells

Background

Metformin has been reported to function as the anti-tumor inhibiting the growth of different types of cancers, including bladder cancer. But there are few reports on the roles of Yap1, the key molecule of Hippo pathway, in the metformin induced inhibition of bladder cancer (BLCA). We are wondering if the inhibitory effect of metformin on bladder cancer is fulfilled via Yap1 and exploring the related mechanism.

Methods

MTS and colony formation assays were used to explore the cellular viabilities and proliferation of BLCA cells challenged by metformin at different concentrations, in vitro. Flow Cytometry (FCM) was used to analyze the cell cycle and the cellular apoptosis of the BLCA cells. Western Blot was performed to detect the expressions of AMPKα, Yap1, CCND1, CCNE1/2 and CDK2/4/6 in the metformin-treated BLCA cell lines. RNAi method was used for the related genetic functional analysis. The relationships among Yap1, TEADs and CCNE1/2 were predicted and evaluated using bioinformatics, dual-luciferase reporter and co-immunoprecipitation (Co-IP) assays. For in vivo experiments, a xenograft model was used to investigate the effects of metformin on the proliferation of BLCA cells. And Immunohistochemistry (IHC) assay was performed to assess the expressions of CCNE1/2 and Yap1 proteins in the tumor tissues from the model.

Results

Metformin could inhibit the proliferation of the BLCA cells via inducing the G1 cell cycle arrest without apoptosis. And metformin upregulated the phosphorylated AMPKα and decreased the expressions of Yap1 and CCND1, CCNE1/2 and CDK4/6. AMPK inhibition by compound C (CC) restored the cell proliferation and the G1 cell cycle arrest induced by metformin, in vivo. Knockdown of YAP1 inhibited the proliferation of BLCA cells and caused the cell cycle arrest at G1 phase by decreasing the expressions of CCNE1/2 and other G1 phase related molecules, which has been restored by the Yap 5SA mutant. Bioinformatics analysis showed that trans-factor TEAD4 was highly expressed and positively associated with the expressions of CCNE1 and CCNE2 in BLCA and only TEAD4 was precipitated by Yap1 in the BLCA cells. Further studies demonstrated that Yap1 positively regulated both CCNE1 and CCNE2 expressions via forming complex with TEAD4. Furthermore, we observed that metformin inhibited the cell proliferation by decreasing the expressions of Yap1 and both CCNE1 and CCNE2 in xenograft model.

Conclusions

The results of our study reveal a new potential regulatory pathway in which metformin inhibits cell proliferation via AMPKα/Yap1/TEAD4/CCNE1/2 axis in BLCA cells, providing new insights into novel molecular therapeutic targets for BLCA.

Electronic supplementary material

The online version of this article (10.1186/s13046-019-1346-1) contains supplementary material, which is available to authorized users.

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.

Inhibition of a G9a/DNMT network triggers immune-mediated bladder cancer regression

Bladder cancer is lethal in its advanced, muscle-invasive phase with very limited therapeutic advances^1,2. Recent molecular characterization has defined new (epi)genetic drivers and potential targets for bladder cancer^3,4. The immune checkpoint inhibitors have shown remarkable efficacy but only in a limited fraction of bladder cancer patients^5-8. Here, we show that high G9a (EHMT2) expression is associated with poor clinical outcome in bladder cancer and that targeting G9a/DNMT methyltransferase activity with a novel inhibitor (CM-272) induces apoptosis and immunogenic cell death. Using an immunocompetent quadruple-knockout (Pten^loxP/loxP; Trp53^loxP/loxP; Rb1^loxP/loxP; Rbl1^-/-) transgenic mouse model of aggressive metastatic, muscle-invasive bladder cancer, we demonstrate that CM-272 + cisplatin treatment results in statistically significant regression of established tumors and metastases. The antitumor effect is significantly improved when CM-272 is combined with anti-programmed cell death ligand 1, even in the absence of cisplatin. These effects are associated with an endogenous antitumor immune response and immunogenic cell death with the conversion of a cold immune tumor into a hot tumor. Finally, increased G9a expression was associated with resistance to programmed cell death protein 1 inhibition in a cohort of patients with bladder cancer. In summary, these findings support new and promising opportunities for the treatment of bladder cancer using a combination of epigenetic inhibitors and immune checkpoint blockade.

BET inhibitor JQ1 suppresses cell proliferation via inducing autophagy and activating LKB1/AMPK in bladder cancer cells

AIM

JQ1, a BET bromodomain inhibitor, is a promising therapeutic approach for bladder cancer (BC). Our study aimed to determine whether autophagy is induced by JQ1 and its potential role toward proliferation in BC.

METHODS

Cell proliferation was determined by methylthiazolyldiphenyl-tetrazolium bromide (MTT) assay, cell counting assay, and colony formation assay. Autophagosomes and autolysosomes were observed by transmission electron microscopy and mRFP-EGFP-LC3 fluorescence assay. 3-MA, BAFA1, NH₄ Cl, and siATG5 were used to inhibit autophagy. AMPK siRNA was used to knock down AMPK. T24 xenograft model in mice was chosen to perform in vivo studies. Autophagy markers LC-3B and p62, p-AMPKα, p-ACC, p-ULK1, p-mTOR and p-LKB1 were determined by western blot in vitro studies and by immunohistochemistry (IHC) in vivo specimens.

RESULTS

We found that BC cell proliferation was suppressed by JQ1; moreover, JQ1 induced the accumulation of autophagosomes and autolysosomes, and autophagy flux, and the growth suppression capacity of JQ1 was attenuated by autophagy inhibitors. Furthermore, we found that JQ1 induced the phosphorylation of AMPKα, and AMPKα knockdown attenuated autophagy induction and anti-proliferation effect induced by JQ1 in BC cells, indicating that autophagy induced by JQ1 is dependent on AMPKα. Through endogenous immunoprecipitation analysis, we found that JQ1 dramatically increased the interaction between LKB1 and AMPKα, which may lead to more AMPK activation. Proliferation inhibition, autophagy induction, and LKB1/AMPK activation capacities of JQ1 were further confirmed in vivo.

CONCLUSIONS

Taken together, our results demonstrate that autophagy is induced by JQ1 through activation of LKB1/AMPK pathway, and the autophagy induced by JQ1 positively contributes to the inhibition of BC cell proliferation. These findings provide a novel point of view to understand the mechanism of how targeting BET bromodomain suppress cancer cell growth and suggest that targeting BET bromodomain might be a potential approach to treat BC in the future.

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.

Differential effects of ginkgol C17:1 on cisplatin-induced cytotoxicity: Protecting human normal L02 hepatocytes versus sensitizing human hepatoma HepG2 cells

Liver cancer is a major healthcare problem and one of the leading causes of cancer-associated mortality in the world. To date, chemotherapy remains a common method for treating cancer and cisplatin is one of the most widely used chemotherapeutics. However, owing to drug resistance and side effects, it is imperative to identify a novel approach to improve the anticancer effect of cisplatin. Auxiliary chemotherapy drugs with minor toxicity to normal cells may represent a novel strategy for cancer therapy. Previous studies have indicated that ginkgol C17:1 exhibits anticancer effects in liver cancer cells in vitro and in vivo. The antitumor activity of ginkgol C17:1 has been reported in combination with cisplatin in human liver cancer cells. Owing to the route of systemic administration, liver cancer cells and normal hepatocytes were exposed to chemotherapeutics and auxiliary chemotherapy drugs. However, the effects of ginkgol C17:1 in normal hepatocytes remain unclear. In the present study, the biological effects of ginkgol C17:1 alone and as co-treatment with cisplatin were compared in human hepatoma cells and normal hepatocytes. Consistently, the results confirmed that in human hepatoma HepG2 cells, ginkgol C17:1 or cisplatin alone induced autophagy and apoptosis. The co-treatment increased cisplatin-induced apoptosis and inhibited cisplatin-induced autophagy. In comparison, the treatments in human normal L02 hepatocytes indicated that ginkgol C17:1 alone induced autophagy, whereas cisplatin alone induced apoptosis. The co-treatment inhibited cisplatin-induced apoptosis, but enhanced autophagy in L02 cells. Further investigation revealed that the AMP-activated protein kinase/serine/threonine protein kinase ULK1 and phosphoinositide 3-kinase/protein kinase B/mammalian target of rapamycin signaling pathways were involved in the underlying regulatory mechanisms. Taken together, the results of the present study provide the first evidence that ginkgol C17:1 protects normal hepatocytes against cisplatin-induced cytotoxicity while potentiating the anticancer effect of cisplatin chemotherapy. The differential effects on normal and cancer cells suggest that ginkgol C17:1 is a promising candidate for auxiliary chemotherapy.

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.

Preprogramming therapeutic response of PI3K/mTOR dual inhibitor via the regulation of EHMT2 and p27 in pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive disease, which is characterized by its high invasiveness, rapid progression, and profound resistance to therapy. Gemcitabine is the first-line treatment option for pancreatic cancer patients, but the overall survival is quite low. Therefore, it is an urgent issue to identify new molecules for improved therapies, with better efficacy and less toxicity. Our previous data indicated that Euchromatic histone-lysine N-methyltransferase 2 (EHMT2) functions as a therapeutic target to override GEM resistance and promote metastasis in the treatment of pancreatic cancer. Here, we screened a small-molecule library of 143 protein kinase inhibitors, to verify cytotoxicity of different inhibitors in EHMT2-depleted cells. We determined that the EHMT2 plays a promising modulating role for targeted PI3K/mTOR inhibition. Our data revealed that EHMT2 down-regulates p27 expression, and this contributes to tumor growth. The depletion of EHMT2, ectopic expression of methyltransferase-dead EHMT2, or treatment with an EHMT2 inhibitor decreases H3K9 methylation of p27 promoter and induces G1 arrest in PANC-1 pancreatic cancer cells. Consistent with these findings, in vivo tumor xenograft models, primary tumors, and the Oncomine database utilizing bioinformatics approaches, also show a negative correlation between EHMT2 and p27. We further demonstrated that low EHMT2 elevated BEZ235 sensitivity through up-regulation of p27 in PDAC cells; high levels of SKP2 decrease BEZ235 responsiveness in PDAC cells. Altogether, our results suggest the EHMT2-p27 axis as a potential marker to modulate cell response to dual PI3K/mTOR inhibition, which might provide a strategy in personalized therapeutics for PDAC patients.

Kaempferol induces autophagic cell death via IRE1-JNK-CHOP pathway and inhibition of G9a in gastric cancer cells

Kaempferol, a flavonoid, found in traditional medicine, fruits, and vegetables, and an HDAC inhibitor, is a powerful anti-cancer reagent against various cancer cell lines. However, detailed mechanisms involved in the treatment of gastric cancer (GC) using kaempferol are not fully understood. In our study, we investigated the biological activity and molecular mechanism involved in kaempferol-mediated treatment of GC. Kaempferol promoted autophagy and cell death, and increased LC3-I to LC3-II conversion and the downregulation of p62 in GC. Furthermore, our results showed that kaempferol induces autophagic cell death via the activation of the IRE1-JNK-CHOP signaling, indicating ER stress response. Indeed, the inhibition of ER stress suppressed kaempferol-induced autophagy and conferred prolonged cell survival, indicating autophagic cell death. We further showed that kaempferol mediates epigenetic change via the inhibition of G9a (HDAC/G9a axis) and also activates autophagic cell death. Taken together, our findings indicate that kaempferol activates the IRE1-JNK-CHOP signaling from cytosol to nucleus, and G9a inhibition activates autophagic cell death in GC cells.

GLP overexpression is associated with poor prognosis in Chronic Lymphocytic Leukemia and its inhibition induces leukemic cell death

Background Heterodimeric methyltransferases GLP (EHMT1/KMT1D) and G9a (EHMT2/KMT1C) are two closely related enzymes that promote the monomethylation and dimethylation of histone H3 lysine 9. Dysregulation of their activity has been implicated in several types of human cancer. Patients and methods Here, in order to investigate whether GLP/G9a exerts any impact on Chronic Lymphocytic Leukemia (CLL), GLP/G9a expression levels were assessed in a cohort of 50 patients and the effects of their inhibition were verified for the viability of CLL cells. Also, qRT-PCR was used to investigate the transcriptional levels of GLP/G9a in CLL patients. In addition, patient samples were classified according to ZAP-70 protein expression by flow cytometry and according to karyotype integrity by cytogenetics analysis. Finally, a selective small molecule inhibitor for GLP/G9a was used to ascertain whether these methyltransferases influenced the viability of MEC-1 CLL cell lineage. Results mRNA analysis revealed that CLL samples had higher levels of GLP, but not G9a, when compared to non-leukemic controls. Interestingly, patients with unfavorable cytogenetics showed higher expression levels of GLP compared to patients with favorable karyotypes. More importantly, GLP/G9a inhibition markedly induced cell death in CLL cells. Conclusion Taken together, these results indicate that GLP is associated with a worse prognosis in CLL, and that the inhibition of GLP/G9a influences CLL cell viability. Altogether, the present data demonstrate that these methyltransferases can be potential markers for disease progression, as well as a promising epigenetic target for CLL treatment and the prevention of disease evolution.

Effects of ginkgol C17:1 on cisplatin-induced autophagy and apoptosis in HepG2 cells

Previous studies have demonstrated that ginkgol C17:1 significantly inhibits human liver cancer cells and enhances the anticancer activity of cisplatin in vivo and in vitro. However, the mechanism and biological function of ginkgol C17:1 on cells undergoing chemotherapy remain unclear. The aim of the present study was to determine the antitumor activity and mechanism of ginkgol C17:1 in combination with cisplatin in human hepatoblastoma HepG2 cells. The green fluorescent protein (GFP)-light chain 3 (LC3) adenovirus was transfected into HepG2 cells and autophagic flux was determined using fluorescence microscopy. Western blot analysis was also conducted to measure the expression of proteins associated with apoptosis, autophagy and their associated signaling pathways. Compared with the control group, autophagic flux and nucleus aberration rates were significantly increased (P<0.05), and the expression of proteins associated with autophagy and apoptosis were increased in the groups treated with cisplatin or ginkgol C17:1, respectively. However, following co-treatment with ginkgol C17:1 and cisplatin, the autophagic flux and the expression of autophagy proteins decreased; however, the nucleus aberration rate and apoptosis protein expression significantly increased (P<0.05) compared with the group treated with cisplatin alone. Additionally, the signaling pathways of autophagy and apoptosis were also activated following treatment with cisplatin, alone and in combination with ginkgol C17:1. Taken together, these results indicate that ginkgol C17:1 inhibits cisplatin-induced autophagy via AMP-activated protein kinase/ULK1signaling and increases cisplatin-induced apoptosis in HepG2 cells via the phosphoinositide 3-kinase/Akt/mechanistic target of rapamycin pathway.

Histone lysine methyltransferase G9a is a novel epigenetic target for the treatment of hepatocellular carcinoma

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

Salen-Mn compounds induces cell apoptosis in human prostate cancer cells through promoting AMPK activity and cell autophagy

Currently only docetaxel has been approved to be used in the chemotherapy of prostate cancer and new drugs are urgent need. Salen-Mn is a novel type of synthetic reagent bionic and exerts remarkable anticancer activities. However, the effect of Salen-Mn on human prostate cancer has not been elucidated yet. In this study, we found that treatment of PC-3 and DU145 human prostate cancer cells with Salen-Mn inhibited cell growth in dose and time dependent manner. Moreover, Salen-Mn induced cell apoptosis, and increased the expression of apoptotic proteins, such as cleaved caspase-3, cleaved PARP, and Bax, in PC-3 and DU145 prostate cancer cells. Furthermore, we found that Salen-Mn induced expression of LC3-I/II, which is protein marker of cell autophagy, in both dose and time dependent manners; in addition, Salen-Mn increased the phosphorylation of AMPK, suggesting that Salen-Mn increase cell autophagy through activating AMPK pathway. On the other hand, when PC-3 and DU145 cells were treated with Salen-Mn and 3-MA, an inhibitor of cell autophagy, the inhibitory effect of Salen-Mn on cell growth and the induction of apoptotic proteins were decreased. In addition, we found that Salen-Mn inhibited the growth of PC-3 cell xenografts in nude mice. In summary, our results indicate that Salen-Mn suppresses cell growth through inducing AMPK activity and autophagic cell death related cell apoptosis in prostate cancer cells and suggest that Salen-Mn and its derivatives could be new options for the chemical therapeutics in the treatment of prostate cancer.

Synthesis and biological evaluation of benzimidazole derivatives as the G9a Histone Methyltransferase inhibitors that induce autophagy and apoptosis of breast cancer cells

G9a (also known as KMT1C or EHMT2) is initially identified as a H3K9 methyltransferase that specifically mono- and dimethylates 'Lys-9' of histone H3 (H3K9me1 and H3K9me2, respectively) in euchromatin. It is overexpressed in various human cancers and employed as a promising target in cancer therapy. We discovered a benzoxazole scaffold through virtual high-throughput screening, and designed, synthesized 24 derivatives and investigated for inhibition of G9a. After several rounds of kinase and anti-proliferative activity screening, we discovered a potent G9a antagonist (GA001) with an IC₅₀ value of 1.32μM that could induce autophagy via AMPK in MCF7 cells. In addition, we found high concentration of GA001 could induce apoptosis via p21-Bim signal cascades in MCF7 cells. Our results highlight a new approach for the development of a novel drug targeting G9a with a potential to induce autophagy and apoptosis for future breast cancer therapy.

Synthesis of magnetic molecularly imprinted polymers with excellent biocompatibility for the selective separation and inhibition of testosterone in prostate cancer cells

PURPOSE

Androgen plays an important role in the progression of prostate cancer. In the present study, novel magnetic molecularly imprinted polymers (MMIPs) with good biocompatibility were produced for the selective separation and inhibition of testosterone in prostate cancer cells.

MATERIALS AND METHODS

MMIPs were prepared by using magnetic nanospheres, gelatin, and testosterone as the supporting materials, functional monomer, and the template molecule, respectively. The characterization of the resultant products was investigated by transmission electron microscopy, X-ray diffraction, and vibrating sample magnetometry. To test whether MMIPs can remove testosterone in biologic samples, human LNCaP (androgen-dependent) and C4-2 (androgen-independent) prostate cancer cells were selected as cell models. The translocation of androgen receptor (AR) was detected by immunofluorescence assay, and the expression of PSA mRNA was detected by real-time quantitative polymerase chain reaction analysis. Cell flow cytometry analysis was performed to detect cell cycle arrest.

RESULTS

The synthesized nanomaterials (MMIPs) possessed high crystallinity, satisfactory superparamagnetic properties, and uniform imprinted shell, and exhibited high adsorption capacity, fast kinetics, and high selectivity for testosterone. Moreover, the obtained imprinted nanomaterials could selectively enrich and detect testosterone in the LNCaP cell samples as a solid-phase extractant coupled with high-performance liquid chromatography. In addition, the MMIPs could freely enter prostate cancer cells and suppress the translocation of AR into the cell nucleus. We further found that MMIPs inhibited upregulation of AR downstream target genes in LNCaP and C4-2 cells; also, MMIPs inhibited cell growth and induced obvious cell cycle arrest in androgen-dependent LNCaP cells, but had no obvious effect on androgen-independent C4-2 cells.

CONCLUSION

Our results indicate that the obtained imprinted nanomaterials can specifically and effectively bind testosterone and recover it from prostate cancer cells. Moreover, the MMIPs can freely enter prostate cancer cells and block the activation of testosterone-AR pathway. Thus, the MMIPs may be a new option for antiandrogen therapy in prostate cancer.

Ischemic Preconditioning Confers Epigenetic Repression of Mtor and Induction of Autophagy Through G9a-Dependent H3K9 Dimethylation

Background

Ischemic preconditioning (IPC) protects the heart from prolonged ischemic insult and reperfusion injury through a poorly understood mechanism. Post‐translational modifications of histone residues can confer rapid and drastic switches in gene expression in response to various stimuli, including ischemia. The aim of this study was to investigate the effect of histone methylation in the response to cardiac ischemic preconditioning.

Methods and Results

We used cardiac biopsies from mice subjected to IPC to quantify global levels of 3 of the most well‐studied histone methylation marks (H3K9me2, H3K27me3, and H3K4me3) with Western blot and found that H3K9me2 levels were significantly increased in the area at risk compared to remote myocardium. In order to assess which genes were affected by the increase in H3K9me2 levels, we performed ChIP‐Seq and transcriptome profiling using microarray. Two hundred thirty‐seven genes were both transcriptionally repressed and enriched in H3K9me2 in the area at risk of IPC mice. Of these, Mtor (Mechanistic target of rapamycin) was chosen for mechanistic studies. Knockdown of the major H3K9 methyltransferase G9a resulted in a significant decrease in H3K9me2 levels across Mtor, increased Mtor expression, as well as decreased autophagic activity in response to rapamycin and serum starvation.

Conclusions

IPC confers an increase of H3K9me2 levels throughout the Mtor gene—a master regulator of cellular metabolism and a key player in the cardioprotective effect of IPC—leading to transcriptional repression via the methyltransferase G9a. The results of this study indicate that G9a has an important role in regulating cardiac autophagy and the cardioprotective effect of IPC.

Oocyte activation and latent HIV-1 reactivation: AMPK as a common mechanism of action linking the beginnings of life and the potential eradication of HIV-1

In all mammalian species studied to date, the initiation of oocyte activation is orchestrated through alterations in intracellular calcium (Ca(2+)) signaling. Upon sperm binding to the oocyte plasma membrane, a sperm-associated phospholipase C (PLC) isoform, PLC zeta (PLCζ), is released into the oocyte cytoplasm. PLCζ hydrolyzes phosphatidylinositol 4,5-bisphosphate (PIP2) to produce diacylglycerol (DAG), which activates protein kinase C (PKC), and inositol 1,4,5-trisphosphate (IP3), which induces the release of Ca(2+) from endoplasmic reticulum (ER) Ca(2+) stores. Subsequent Ca(2+) oscillations are generated that drive oocyte activation to completion. Ca(2+) ionophores such as ionomycin have been successfully used to induce artificial human oocyte activation, facilitating fertilization during intra-cytoplasmic sperm injection (ICSI) procedures. Early studies have also demonstrated that the PKC activator phorbol 12-myristate 13-acetate (PMA) acts synergistically with Ca(2+) ionophores to induce parthenogenetic activation of mouse oocytes. Interestingly, the Ca(2+)-induced signaling cascade characterizing sperm or chemically-induced oocyte activation, i.e. the "shock and live" approach, bears a striking resemblance to the reactivation of latently infected HIV-1 viral reservoirs via the so called "shock and kill" approach, a method currently being pursued to eradicate HIV-1 from infected individuals. PMA and ionomycin combined, used as positive controls in HIV-1 latency reversal studies, have been shown to be extremely efficient in reactivating latent HIV-1 in CD4(+) memory T cells by inducing T cell activation. Similar to oocyte activation, T cell activation by PMA and ionomycin induces an increase in intracellular Ca(2+) concentrations and activation of DAG, PKC, and downstream Ca(2+)-dependent signaling pathways necessary for proviral transcription. Interestingly, AMPK, a master regulator of cell metabolism that is activated thorough the induction of cellular stress (e.g. increase in Ca(2+) concentration, reactive oxygen species generation, increase in AMP/ATP ratio) is essential for oocyte maturation, T cell activation, and mitochondrial function. In addition to the AMPK kinase LKB1, CaMKK2, a Ca(2+)/calmodulin-dependent kinase that also activates AMPK, is present in and activated on T cell activation and is also present in mouse oocytes and persists until the zygote and two-cell stages. It is our hypothesis that AMPK activation represents a central node linking T cell activation-induced latent HIV-1 reactivation and both physiological and artificial oocyte activation. We further propose the novel observation that various compounds that have been shown to reactivate latent HIV-1 (e.g. PMA, ionomycin, metformin, bryostatin, resveratrol, etc.) or activate oocytes (PMA, ionomycin, ethanol, puromycin, etc.) either alone or in combination likely do so via stress-induced activation of AMPK.