Hypomethylation-Linked Activation of PLCE1 Impedes Autophagy and Promotes Tumorigenesis through MDM2-Mediated Ubiquitination and Destabilization of p53

Identification of differentially expressed autophagy-related genes in cases of intracranial aneurysm: Bioinformatics analysis

OBJECTIVE

Recent research indicates that autophagy is essential for the rupture of intracranial aneurysm (IA). This study aimed to examine and validate potential autophagy-related genes (ARGs) in cases of IA using bioinformatics analysis.

METHODS

Two expression profiles (GSE54083 and GSE75436) were obtained from the Gene Expression Omnibus database. Differentially expressed ARGs (DEARGs) in cases of IA were screened using GSE75436, and enrichment analysis and Protein-Protein Interaction (PPI) networks were used to identify the hub genes and related pathways. Furthermore, a novel predictive diagnostic signature for IA based on the hub genes was constructed. The area under the Receiver Operating Characteristic curve (AUC) was used to evaluate the signature performance in GSE75436.

RESULTS

In total, 75 co-expressed DEARGs were identified in the GSE75436 and GSE54083 dataset (28 upregulated and 47 downregulated genes). Enrichment analysis of DEARGs revealed several enriched terms associated with proteoglycans in cancer and human immunodeficiency virus 1 infection. PPI analysis revealed interactions between these genes. Hub DEARGs included insulin-like growth factor 1, clusters of differentiation 4, cysteine-aspartic acid protease 8, Bcl-2-like protein 11, mouse double mutant 2 homolog, toll-like receptor 4, growth factor receptor-bound protein 2, Jun proto-oncogene, AP-1 transcription factor subunit, hypoxia inducible factor 1 alpha, and erythroblastic oncogene B-2. Notably, the signature showed good performance in distinguishing IA (AUC = 0.87). The sig calibration curves showed good calibration.

CONCLUSION

Bioinformatic analysis identified 75 potential DEARGs in cases of IA. This study revealed that IA is affected by autophagy, which could explain the pathogenesis of IA and aid in its diagnosis and treatment. However, future research with experimental validation is necessary to identify potential DEARGs in cases of IA.

Molecular mechanisms in regulation of autophagy and apoptosis in view of epigenetic regulation of genes and involvement of liquid-liquid phase separation

Cellular physiology is critically regulated by multiple signaling nexuses, among which cell death mechanisms play crucial roles in controlling the homeostatic landscape at the tissue level within an organism. Apoptosis, also known as programmed cell death, can be induced by external and internal stimuli directing the cells to commit suicide in unfavourable conditions. In contrast, stress conditions like nutrient deprivation, infection and hypoxia trigger autophagy, which is lysosome-mediated processing of damaged cellular organelle for recycling of the degraded products, including amino acids. Apparently, apoptosis and autophagy both are catabolic and tumor-suppressive pathways; apoptosis is essential during development and cancer cell death, while autophagy promotes cell survival under stress. Moreover, autophagy plays dual role during cancer development and progression by facilitating the survival of cancer cells under stressed conditions and inducing death in extreme adversity. Despite having two different molecular mechanisms, both apoptosis and autophagy are interconnected by several crosslinking intermediates. Epigenetic modifications, such as DNA methylation, post-translational modification of histone tails, and miRNA play a pivotal role in regulating genes involved in both autophagy and apoptosis. Both autophagic and apoptotic genes can undergo various epigenetic modifications and promote or inhibit these processes under normal and cancerous conditions. Epigenetic modifiers are uniquely important in controlling the signaling pathways regulating autophagy and apoptosis. Therefore, these epigenetic modifiers of both autophagic and apoptotic genes can act as novel therapeutic targets against cancers. Additionally, liquid-liquid phase separation (LLPS) also modulates the aggregation of misfolded proteins and provokes autophagy in the cytosolic environment. This review deals with the molecular mechanisms of both autophagy and apoptosis including crosstalk between them; emphasizing epigenetic regulation, involvement of LLPS therein, and possible therapeutic approaches against cancers.

Phospholipase PLCE1 Promotes Transcription and Phosphorylation of MCM7 to Drive Tumor Progression in Esophageal Cancer

Phospholipase C epsilon 1 (PLCE1) is a well-established susceptibility gene for esophageal squamous cell carcinoma (ESCC). Identification of the underlying mechanism(s) regulated by PLCE1 could lead to a better understanding of ESCC tumorigenesis. In this study, we found that PLCE1 enhances tumor progression by regulating the replicative helicase MCM7 via two pathways. PLCE1 activated PKCα-mediated phosphorylation of E2F1, which led to the transcriptional activation of MCM7 and miR-106b-5p. The increased expression of miR-106b-5p, located in intron 13 of MCM7, suppressed autophagy and apoptosis by targeting Beclin-1 and RBL2, respectively. Moreover, MCM7 cooperated with the miR-106b-25 cluster to promote PLCE1-dependent cell-cycle progression both in vivo and in vitro. In addition, PLCE1 potentiated the phosphorylation of MCM7 at six threonine residues by the atypical kinase RIOK2, which promoted MCM complex assembly, chromatin loading, and cell-cycle progression. Inhibition of PLCE1 or RIOK2 hampered MCM7-mediated DNA replication, resulting in G1-S arrest. Furthermore, MCM7 overexpression in ESCC correlated with poor patient survival. Overall, these findings provide insights into the role of PLCE1 as an oncogenic regulator, a promising prognostic biomarker, and a potential therapeutic target in ESCC.

SIGNIFICANCE

PLCE1 promotes tumor progression in ESCC by activating PKCα-mediated phosphorylation of E2F1 to upregulate MCM7 and miR-106b-5p expression and by potentiating MCM7 phosphorylation by RIOK2.

Hydrogen sulfide attenuates atherosclerosis induced by low shear stress by sulfhydrylating endothelium NFIL3 to restrain MEST mediated endothelial mesenchymal transformation

BACKGROUND

Endothelial-mesenchymal transition (EndMT) induced by low shear stress plays an important role in the development of atherosclerosis. However, little is known about the correlation between hydrogen sulfide (H2S), a protective gaseous mediator in atherosclerosis and the process of EndMT.

METHODS

We constructed a stable low-shear-stress-induced(2 dyn/cm2) EndMT model, acombined with the pretreatment method of hydrogen sulfide slow release agent(GYY4137). The level of MEST was detected in the common carotid artery of ApoE-/- mice with local carotid artery ligation. The effect of MEST on atherosclerosis development in vivo was verified using ApoE-/- mice were given tail-vein injection of endothelial-specific overexpressed and knock-down MEST adeno-associated virus (AAV).

RESULTS

These findings confirmed that MEST is up-regulated in low-shear-stress-induced EndMT and atherosclerosis. In vivo experiments showed that MEST gene overexpression significantly promoted EndMT and aggravated the development of atherosclerotic plaques and MEST gene knockdown significantly inhibited EndMT and delayed the process of atherosclerosis. In vitro, H2S inhibits the expression of MEST and EndMT induced by low shear stress and inhibits EndMT induced by MEST overexpression. Knockdown of NFIL3 inhibit the up regulation of MEST and EndMT induced by low shear stress in HUVECs. CHIP-qPCR assay and Luciferase Reporter assay confirmed that NFIL3 binds to MEST DNA, increases its transcription and H2S inhibits the binding of NFIL3 and MEST DNA, weakening NFIL3's transcriptional promotion of MEST. Mechanistically, H2S increased the sulfhydrylation level of NFIL3, an important upstream transcription factors of MEST. In part, transcription factor NFIL3 restrain its binding to MEST DNA by sulfhydration.

CONCLUSIONS

H2S negatively regulate the expression of MEST by sulfhydrylation of NFIL3, thereby inhibiting low-shear-stress-induced EndMT and atherosclerosis.

PAD2: A potential target for tumor therapy

Peptide arginine deiminase 2(PAD2) catalyzes the conversion of arginine residues on target proteins to citrulline residues in the presence of calcium ions. This particular posttranslational modification is called citrullination. PAD2 can regulate the transcriptional activity of genes through histone citrullination and nonhistone citrullination. In this review, we summarize the evidence from recent decades and systematically illustrate the role of PAD2-mediated citrullination in tumor pathology and the regulation of tumor-associated immune cells such as neutrophils, monocytes, macrophages and T cells. Several PAD2-specific inhibitors are also presented to discuss the feasibility of anti-PAD2 therapy to treat tumors and the urgent problems to be solved. Finally, we review some recent developments in the development of PAD2 inhibitors.

Identification of hub necroptosis-related lncRNAs for prognosis prediction of esophageal carcinoma

Necroptosis is a newly identified programmed cell death associated with the biological process of various cancers, including esophageal carcinoma (ESCA). Meanwhile, the dysregulation of long non-coding RNAs (lncRNAs) is greatly implicated in ESCA progression and necroptosis regulation. However, the lncRNAs involved in regulating necroptosis in ESCA are still unclear. In this study, we aim to explore the expression profile of necroptosis-related lncRNAs (NRLs), and evaluate their roles in ESCA prognosis and treatment. In the present study, 198 differentially expressed NRLs were identified between the ESCA and adjacent normal tissues through screening the data extracted from the Cancer Genome Atlas (TCGA) database. And, a prognostic panel consisting of 6 NRLs was constructed using the LASSO algorithm and multivariate Cox regression analysis. The ESCA patients with high risks had a markedly reduced survival time and higher mortality prevalence. Moreover, C-index of 6 NRLs-panel was superior to 48 published prognostic models based on lncRNAs or mRNAs for ESCA. There were significant differences between the high-risk and low-risk groups in tumor-related pathways, genetic mutations, and drug sensitivity responses. In vitro analysis revealed that inhibition of PVT1 impeded the proliferation, migration, and colony formation of ESCA cells, increased the expressions of p-RIP1 and p-MLKL and promoted necroptosis. By contrast, PVT1 overexpression resulted in a decrease in necroptotic cell death events, thus promoting tumor progression. Collectively, the established 6-NRLs panel was a promising biomarker for the prognostic prediction of ESCA. Moreover, our current findings provided potential targets for individualized therapy for ESCA patients.

Inhibition of the Phospholipase Cε-c-Jun N-Terminal Kinase Axis Suppresses Glioma Stem Cell Properties

Glioma stem cells (GSCs), the cancer stem cells of glioblastoma multiforme (GBM), contribute to the malignancy of GBM due to their resistance to therapy and tumorigenic potential; therefore, the development of GSC-targeted therapies is urgently needed to improve the poor prognosis of GBM patients. The molecular mechanisms maintaining GSCs need to be elucidated in more detail for the development of GSC-targeted therapy. In comparison with patient-derived GSCs and their differentiated counterparts, we herein demonstrated for the first time that phospholipase C (PLC)ε was highly expressed in GSCs, in contrast to other PLC isoforms. A broad-spectrum PLC inhibitor suppressed the viability of GSCs, but not their stemness. Nevertheless, the knockdown of PLCε suppressed the survival of GSCs and induced cell death. The stem cell capacity of residual viable cells was also suppressed. Moreover, the survival of mice that were transplanted with PLCε knockdown-GSCs was longer than the control group. PLCε maintained the stemness of GSCs via the activation of JNK. The present study demonstrated for the first time that PLCε plays a critical role in maintaining the survival, stemness, and tumor initiation capacity of GSCs. Our study suggested that PLCε is a promising anti-GSC therapeutic target.

Structural studies of antitumor compounds that target the RING domain of MDM2

Mouse double minute 2 homolog (MDM2) is an E3 ubiquitin-protein ligase that is involved in the transfer of ubiquitin to p53 and other protein substrates. The expression of MDM2 is elevated in cancer cells and inhibitors of MDM2 showed potent anticancer activities. Many inhibitors target the p53 binding domain of MDM2. However, inhibitors such as Inulanolide A and MA242 are found to bind the RING domain of MDM2 to block ubiquitin transfer. In this report, crystal structures of MDM2 RING domain in complex with Inulanolide A and MA242 were solved. These inhibitors primarily bind in a hydrophobic site centered at the sidechain of Tyr489 at the C-terminus of MDM2 RING domain. The C-terminus of MDM2 RING domain, especially residue Tyr489, is required for ubiquitin discharge induced by MDM2. The binding of these inhibitors at Tyr489 may interrupt interactions between the MDM2 RING domain and the E2-Ubiquitin complex to inhibit ubiquitin transfer, regardless of what the substrate is. Our results suggest a new mechanism of inhibition of MDM2 E3 activity for a broad spectrum of substrates.

The role of autophagy in initiation, progression, TME modification, diagnosis, and treatment of esophageal cancers

Autophagy is a highly conserved metabolic process with a cytoprotective function. Autophagy is involved in cancer, infection, immunity, and inflammation and may be a potential therapeutic target. Increasing evidence has revealed that autophagy has primary implications for esophageal cancer, including its initiation, progression, tumor microenvironment (TME) modification, diagnosis, and treatment. Notably, autophagy displayed excellent application potential in radiotherapy combined with immunotherapy. Radiotherapy combined with immunotherapy is a new potential therapeutic strategy for cancers, including esophageal cancer. Autophagy modulators can work as adjuvant enhancers in radiotherapy or immunotherapy of cancers. This review highlights the most recent data related to the role of autophagy regulation in esophageal cancer.

Effects of tobacco compound 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) on the expression of epigenetically regulated genes in lung carcinogenesis

Cigarette smoking is a major cause of lung cancer. Although tobacco smoking-induced genotoxicity has been well established, there is apparent lack of abundance functional epigenetic effects reported On cigarette smoke-induced lung carcinogenesis. The aim of this study was to determine effects of intratracheal administration of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) utilizing target gene expression DNA methylation patterns in lung tissues of mice following twice weekly for 8 weeks treatment. An unbiased approach where genomic regions was undertaken to assess early methylation changes within mouse pulmonary tissues. A methylated-CpG island recovery assay (MIRA) was performed to map the DNA methylome in lung tissues, with the position of methylated DNA determined using a Genome Analyzer (MIRA-SEQ). Alterations in epigenetic-regulated target genes were confirmed with quantitative reverse transcription-PCR, which revealed 35 differentially hypermethylated genes including Cdkn1C, Hsf4, Hnf1a, Cdx1, and Hoxa5 and 30 differentially hypomethylated genes including Ddx4, Piwi1, Mdm2, and Pce1 in NNK-exposed lung tissue compared with controls. The main pathway of these genes for mediating biological information was analyzed using the Kyoto Encyclopedia of Genes and Genomes database. Among them, Rssf1 and Mdm2 were closely associated with NNK-induced lung carcinogenesis. Taken together, our data provide valuable resources for detecting cigarette smoke-induced lung carcinogenesis.

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.

CircPLCE1 facilitates the malignant progression of colorectal cancer by repressing the SRSF2-dependent PLCE1 pre-RNA splicing

Studies have demonstrated that circular RNAs (circRNAs) play important roles in various types of cancer; however, the mechanisms of circRNAs located in the nucleus have rarely been explored. Here, we report a novel circular RNA circPLCE1 (hsa_circ_0019230) that facilitates the malignant progression of colorectal cancer (CRC) by repressing serine/arginine‐rich splicing factor 2 (SRSF2)‐dependent phospholipase C epsilon 1 (PLCE1) pre‐RNA splicing. Quantitative real‐time polymerase chain reaction was used to determine the expression of circPLCE1 in CRC tissues and cells. Cell Counting Kit‐8, Transwell and flow cytometric assays were used to assess the role of circPLE1 in CRC cell proliferation, migration and apoptosis, respectively. An animal study was conducted to test the role of circPLCE1 in vivo. Furthermore, catRAPID and RPISeq were used to predict the possible binding proteins of circPLCE1. RNA fractionation and RNA immunoprecipitation assays were used to confirm the RNA‐protein interaction. In this study, we found that circPLCE1 was more significantly down‐regulated in CRC tissues compared with that in adjacent normal tissues. However, circPLCE1 knockdown suppressed CRC cell proliferation, migration and invasion and increased apoptosis. Nude mouse experiments showed that ectopic expression of circPLCE1 dramatically increased tumour growth in vivo. Mechanistically, circPLCE1 directly bound to the SRSF2 protein, repressing SRSF2‐dependent PLCE1 pre‐RNA splicing, resulting in the progression of CRC. Individually mutating the binding sites of circPLCE1 abolished the inhibition of PLCE1 mRNA production. Our study revealed a novel molecular mechanism in the regulation of PLCE1 and suggested a new function of circular RNA.

Identification of a PLCE1‑regulated competing endogenous RNA regulatory network for esophageal squamous cell carcinoma

Phospholipase C epsilon 1 (PLCE1) and the competing endogenous RNA (ceRNA) network are crucial for tumorigenesis and the progression of esophageal squamous cell carcinoma (ESCC). However, whether PLCE1 can regulate the ceRNA network in ESCC has not been clarified. In the present study, we aimed to identify the PLCE1-regulated ceRNA network and further elucidate the regulatory mechanisms by which ESCC is promoted. Microarray analysis was used to identify differentially expressed lncRNAs (DELs) and differentially expressed genes (DEGs) from three pairs of samples of PLCE-silenced Eca109 and control Eca109 cells. Next, the ceRNA regulatory network was established and visualized in Cytoscape, and functional enrichment analysis was performed to analyze DEGs from ceRNAs. Protein-protein interaction (PPI) networks among the DEGs were established by the STRING database to screen hub genes. Kaplan-Meier survival analysis was used to validate hub genes. Finally, PLCE1-related hub gene/lncRNA/miRNA axes were also constructed based on the ceRNA network. A total of 105 DELs and 346 DEGs were found to be dysregulated in the microarray data (|log2FC| >1.5, adjusted P<0.05). We constructed a PLCE1-regulated ceRNA network that incorporated 12 lncRNAs, 43 miRNAs, and 169 mRNAs. Functional enrichment analysis indicated that the DEGs might be associated with ESCC onset and development. A PPI network was established, and 9 hub genes [WD and tetratricopeptide repeats 1 (WDTC1), heat shock protein family A (Hsp70) member 5 (HSPA5), N-ethylmaleimide sensitive factor, vesicle fusing ATPase (NSF), fibroblast growth factor 2 (FGF2), cyclin dependent kinase inhibitor 1A (CDKN1A or P21), bone morphogenetic protein 2 (BMP2), complement C3 (C3), GM2 ganglioside activator (GM2A) and discs large MAGUK scaffold protein 4 (DLG4)] were determined from the network. Kaplan-Meier survival analysis validated four hub genes (BMP2, CDKN1A, GM2A, and DLG4) that were treated as prognostic factors. Ultimately, hub gene/lncRNA/miRNA subnetworks were obtained based on the 4 hub genes, 13 DEmiRNAs, and 10 DELs. In conclusion, the PLCE1-regulated ceRNA contributes to the onset and progression of ESCC and the underlying molecular mechanisms may provide insights into personalized prognosis and new therapies for ESCC patients.

Ganoderic acid D induces synergistic autophagic cell death except for apoptosis in ESCC cells

ETHNOPHAMACOLOGICAL RELEVANCE

Ganoderma lucidum has been used as a medicinal mushroom for more than 2000 years in China. Ganoderic acid D (GAD) as a representative active triterpenoid from Ganoderma lucidum is known to possess anticancer activity. However, the mechanism involved in its anticancer cell process is still largely elusive.

AIM OF THE STUDY

Our study aimed to investigate the anticancer effects of GAD on the esophageal squamous cell carcinoma (ESCC) cells and the underlying mechanisms at the cell level.

MATERIALS AND METHODS

EC9706 and Eca109 cells were treated with GAD (0, 10, 20, 40 μM) for 24 h. The cell viability, cell cycle, reactive oxygen species (ROS), mitochondrial membrane potential (MMP), apoptosis rate, caspase-3 activity, autophagic flux, lysosomal function were examined. Cell cycle, apoptotic, autophagy and mTOR signal pathway related proteins such as P53, Cyclin B1, CytoC, PARP, Beclin-1, P62, LC3, PI3K, AKT and mTOR were analyzed by Western blot approach.

RESULTS

GAD inhibited cell proliferation and induced both apoptosis and autophagic cell death. In particular, we found that in the early stage of the autophagic process, GAD could initiate and enhance the autophagy signal while in the late stage it on the contrary could block the autophagic flux by impairing the autophagosome-lysosome fusion and inhibited the lysosomal degradation. Besides the autophagic cell death, GAD also induced the apoptosis mediated by caspase-related process in parallel. The mechanism involved for the synergistic apoptotic and autophagic cell death was also explored. We found that GAD down-regulated the expression of PI3K, AKT and mTOR phosphorylated proteins in the mTOR signaling pathway which thus led to the synergistic effect on apoptosis and autophagic cell death in the ESCC cells.

CONCLUSIONS

In summary, this study has documented that GAD may inhibit cell proliferation through the mTOR pathway in ESCC cells, and induce synergistic apoptosis and autophagic cell death by disrupting the autophagic flux. This work therefore also suggests that GAD may be used as an efficient anticancer adjuvant for ESCC cancer therapy.

USP4 function and multifaceted roles in cancer: a possible and potential therapeutic target

Cancer remains one of the major culprits causing disease-related deaths and leads to a high morbidity and similar mortality. Insidious onset, difficult early detection and a lack of broad-spectrum and effective multi-cancer therapeutic targets have limited the prolongation of cancer patients’ survival for decades. Therefore, a versatile therapeutic target which is involved in various cancer-related signaling pathways and different cancers may be more effective for cancer targeted therapy. USP4, one of the DUBs members which participates in deubiquitination, an inverse process of ubiquitination, can regulate various classical cancer-related signaling pathways, and thereby plays a vital role in some pathological and physiological processes including tumor initiation and progression. Recently, USP4 has been found to exert versatile influences on cells proliferation, migration and invasion, also apoptosis of various tumors. Moreover, USP4 can also act as a prognostic biomarker in several cancers. This review will give a comprehensive introduction of USP4 about its regulatory mechanisms, related signaling pathways, pathophysiological functions and the roles in various cancers which may help us better understand its biological functions and improve future studies to construct suitable USP4-targeted cancer therapy system.