The Complex Network between MYC Oncogene and microRNAs in Gastric Cancer: An Overview

MYC and NCAPG2 as molecular targets of colorectal cancer and gastric cancer in nursing

Colorectal cancer is a common malignant tumor in intestinal tract, the early symptoms are not obvious. Gastric cancer is a malignant tumor originating from the gastric mucosal epithelium. However, the role of MYC and non-SMC condensin II complex subunit G2 (NCAPG2) in colorectal cancer and gastric cancer remains unclear. The colorectal cancer datasets GSE49355 and gastric cancer datasets GSE19826 were downloaded from gene expression omnibus database. Differentially expressed genes (DEGs) were screened and weighted gene co-expression network analysis (WGCNA) was performed. Functional enrichment analysis, gene set enrichment analysis (GSEA) and immune infiltration analysis was performed. Construction and analysis of protein-protein interactions (PPI) network. Survival analysis and comparative toxicogenomics database (CTD) were performed. A heat map of gene expression was drawn. A total of 751 DEGs were obtained. According to the gene ontology (GO) analysis, in Biological process (BP) analysis, they are mainly enriched in cell differentiation, cartilage development, and skeletal development. In cellular component (CC) analysis, they are mainly enriched in the cytoskeleton of muscle cells and actin filaments. In molecular function (MF) analysis, they are mainly concentrated in Rho GTPase binding, DNA binding, and fibronectin binding. In Kyoto encyclopedia of genes and genomes (KEGG) pathway analysis, they are mainly enriched in the MAPK signaling pathway, apoptosis, and cancer pathways. The soft threshold power for WGCNA analysis was set to 9, resulting in the generation of 40 modules. Ultimately, 2 core genes (MYC and NCAPG2) were identified. The heatmap of core gene expression showed high expression of MYC and NCAPG2 in colorectal cancer tissue samples and low expression in normal tissue samples, while they were core molecules in gastric cancer. Survival analysis indicated that MYC and NCAPG2 were risk factors, showing an upregulation trend with increasing risk scores. CTD analysis revealed associations of MYC and NCAPG2 with colorectal cancer, gastric cancer, inflammation, and immune system diseases. MYC and NCAPG2 are highly expressed in colorectal cancer. The higher the expression of MYC and NCAPG2, the worse the prognosis. MYC and NCAPG2 are core molecules in gastric cancer.

TRIM50 Inhibits Gastric Cancer Progression by Regulating the Ubiquitination and Nuclear Translocation of JUP

Gastric cancer is one of the most frequent cancers in the world. Emerging clinical data show that ubiquitination system disruptions are likely involved in carcinoma genesis and progression. However, the precise role of ubiquitin (Ub)-mediated control of oncogene products or tumor suppressors in gastric cancer is unknown. Tripartite motif-containing 50 (TRIM50), an E3 ligase, was discovered by high-output screening of ubiquitination-related genes in tissues from patients with gastric cancer to be among the ubiquitination-related enzymes whose expression was most downregulated in gastric cancer. With two different databases, we verified that TRIM50 expression was lower in tumor tissues relative to normal tissues. TRIM50 also suppressed gastric cancer cell growth and migration in vitro and in vivo. JUP, a transcription factor, was identified as a new TRIM50 ubiquitination target by MS and coimmunoprecipitation experiments. TRIM50 increases JUP K63-linked polyubiquitination mostly at the K57 site. We discovered that the K57 site is critical for JUP nuclear translocation by prediction with the iNuLoC website and further studies. Furthermore, ubiquitination of the K57 site limits JUP nuclear translocation, consequently inhibiting the MYC signaling pathway. These findings identify TRIM50 as a novel coordinator in gastric cancer cells, providing a potential target for the development of new gastric cancer treatment strategies.

IMPLICATIONS

TRIM50 regulates gastric cancer tumor progression, and these study suggest TRIM50 as a new cancer target.

SLC39A10 promotes malignant phenotypes of gastric cancer cells by activating the CK2-mediated MAPK/ERK and PI3K/AKT pathways

Solute carrier family 39 member 10 (SLC39A10) belongs to a subfamily of zinc transporters and plays a key role in B-cell development. Previous studies have reported that its upregulation promotes breast cancer metastasis by enhancing the influx of zinc ions (Zn2+); however, its role in gastric cancer remains totally unclear. Here, we found that SLC39A10 expression was frequently increased in gastric adenocarcinomas and that SLC39A10 upregulation was strongly associated with poor patient outcomes; in addition, we identified SLC39A10 as a direct target of c-Myc. Functional studies showed that ectopic expression of SLC39A10 in gastric cancer cells dramatically enhanced the proliferation, colony formation, invasiveness abilities of these gastric cancer cells and tumorigenic potential in nude mice. Conversely, SLC39A10 knockdown inhibited gastric cancer cell proliferation and colony formation. Mechanistically, SLC39A10 exerted its carcinogenic effects by increasing Zn2+ availability and subsequently enhancing the enzyme activity of CK2 (casein kinase 2). As a result, the MAPK/ERK and PI3K/AKT pathways, two major downstream effectors of CK2, were activated, while c-Myc, a downstream target of these two pathways, formed a vicious feedback loop with SLC39A10 to drive the malignant progression of gastric cancer. Taken together, our data demonstrate that SLC39A10 is a functional oncogene in gastric cancer and suggest that targeting CK2 is an alternative therapeutic strategy for gastric cancer patients with high SLC39A10 expression.

The Silkworm Carboxypeptidase Inhibitor Prevents Gastric Cancer Cells' Proliferation through the EGF/EGFR Signaling Pathway

Gastric cancer is a common malignant tumor originating from the gastric mucosa epithelium. Studies have shown that bioactive substances such as antimicrobial peptides and cantharidin contained in a variety of insects can exert anti-cancer functions; when compared with chemotherapy drugs, these bioactive substances have less toxicity and reduced side effects. Here, we report the first Bombyx mori carboxypeptidase inhibitor that is specifically and highly expressed in silk glands, which can significantly prevent the proliferation of gastric cancer cells by inhibiting the MAPK/ERK pathway initiated by EGF/EGFR through the promotion of expression of the proto-oncogene c-Myc, thereby affecting the expression of related cyclins. Through molecular docking and virtual screening of silkworm carboxypeptidase inhibitors and epidermal growth factor receptors, we identified a polypeptide that overlapped with existing small-molecule inhibitors of the receptor. In the present work, we explore the medicinal potential and application of silkworm carboxypeptidase inhibitors to promote the development of anti-tumor drugs from insect-derived substances.

Effect of Electroacupuncture at Zusanli (ST36) on Intestinal Microbiota in Rats With Chronic Atrophic Gastritis

Background: Electroacupuncture is a common treatment for chronic atrophic gastritis (CAG) in China. We aimed to determine the effects of electroacupuncture at zusanli (ST36) on intestinal microbiota in CAG rats.

Methods: In total, 42 SD rats were randomly divided into normal (NC, 10 rats) and model (MG, 32 rats) groups. Rats in the MG group were established as CAG disease models. After that, the rats in the MG group were randomly divided into CAG (10 rats), electroacupuncture (EA, 10 rats), and Vitacoenzyme (Vit, 10 rats) groups. Rats in the NC and CAG groups were subjected to a 30-min/d confinement for 4 weeks. Rats in the EA group were given electroacupuncture at zusanli for 30 min/d for 4 weeks. Rats in the Vit group were given Vitacoenzyme solution 10 ml/(kg d) for 4 weeks. Histopathological changes in the gastric mucosa were observed with hematoxylin and eosin staining, and the gene expression level of p53, Bcl-2, and c-myc was determined using the qPCR method. The 16S rDNA sequencing technique was used to determine structural changes and relative abundance expression of intestinal flora.

Results: Compared with the NC group, gastric mucosal pathology in the CAG group revealed significant inflammatory infiltration, and the gastric mucosal lesions in the electroacupuncture group were improved remarkably; the expression of p53 and c-myc genes in the CAG group increased (p < 0.05), while the expression of Bcl-2 genes decreased (p < 0.05) in the EA group, that of p53 and c-myc genes decreased (p < 0.05), and that of Bcl-2 genes increased (p < 0.05). The abundance of bacteria such as Lactobacillus, Desulfobacterota, and Bacteroides pectinophilus group in the CAG group increased (p < 0.05), while that of bacteria such as Gastranaerophilales, Romboutsia, and Blautia decreased (p < 0.05). The relative abundance of Desulfobacterota and Helicobacter in the EA group decreased (p < 0.05), while that of probiotic bacteria such as Oscillospirales, Romboutsia, and Christensenellaceae increased (p < 0.05).

Conclusion: Electroacupuncture at zusanli can promote the repair of pathological damage to the gastric mucosa in rats with CAG, and the mechanism might relate to the reduction in the relative abundance of harmful bacteria, increase in the relative abundance of intestinal probiotics, and regulation of the intestinal microbiota.

microRNA-378a-3p regulates the progression of hepatocellular carcinoma by regulating PD-L1 and STAT3

Programmed death ligand 1 (PD-L1) plays an essential role in the development or progression of hepatocellular carcinoma (HCC). MicroRNAs (miRNAs) are small RNA molecules that regulate gene expression during normal and pathophysiological events. Here, we explored the functions and detailed mechanisms of miR-378a-3p and PD-L1 in HCC progression. First, miR-378a-3p was selected by analyzing miRNA levels in two HCC Gene Expression Omnibus datasets. We found that miR-378a-3p levels exhibited a downward trend in HCC and were negatively correlated with PD-L1 levels. Additionally, a dual luciferase assay predicted that miR-378a-3p directly targets PD-L1. Moreover, the transfection of miR-378a-3p mimics into Li-7 and HuH-7 cells effectively decreased the PD-L1 mRNA and protein expression levels, and inhibited Treg differentiation in co-culture models by modulating the expression levels of certain cytokines. Furthermore, the overexpression of miR-378a-3p hindered cell proliferation and migration but facilitated apoptosis by repressing STAT3 signaling in HCC cells. In conclusion, miR-378a-3p appears to inhibit HCC tumorigenesis by regulating PD-L1 and STAT3 levels. Thus, miR-378a-3p may be a potential target for HCC therapy.

Effect of Helicobacter pylori Eradication on Epigenetic Changes in Gastric Cancer-related Genes

It is known that gastric carcinogenesis results from the progressive changes from chronic gastritis to gastric atrophy, intestinal metaplasia, dysplasia, and invasive carcinoma. Several genetic and epigenetic alterations are involved in this process, and Helicobacter pylori (H. pylori) infection is believed to induce the initiation and progression of these steps. From an epigenetic point of view, H. pylori induces hypermethylation of genes involved in the development of gastric cancer and regulates the expression of various microRNAs (miRNAs). These H. pylori-related epigenetic changes are accumulated not only at the site of neoplasm but also in the adjacent non-cancerous gastric mucosa. Thereby, a state vulnerable to gastric cancer known as an epigenetic field defect is formed. H. pylori eradication can have an effective chemopreventive effect in gastric carcinogenesis. However, the molecular biological changes that occur in the stomach environment during H. pylori eradication have not yet been established. Several studies have reported that H. pylori eradication can restore infection-related changes, especially epigenetic alterations in gastric cancer-related genes, but some studies have shown otherwise. Simply put, it appears that the recovery of methylated gastric cancer-related genes and miRNAs during H. pylori eradication may vary among genes and may also differ depending on the histological subtype of the gastric mucosa. In this review, we will discuss the potential mechanism of gastric cancer prevention by H. pylori eradication, mainly from an epigenetic perspective.

Prognostic Value and Biological Functions of RNA Binding Proteins in Stomach Adenocarcinoma

Purpose

To investigate the prognostic value and biological function of RNA binding proteins (RBPs) in stomach adenocarcinoma (STAD).

Materials and Methods

Datasets of the differentially expressed genes (DEGs) were downloaded from the TCGA-based (The Cancer Genome Atlas) GEPIA database, from which the differentially expressed RBPs were determined. Functions and prognostic values of these determined RBPs were systematically investigated by a series of methods in bioinformatics analysis. In addition, transwell assays were performed to explore the effect of PTBP1 in STAD cells.

Results

Three hundred and sixty-two differentially expressed RBPs were determined, with 331 up-regulated and 31 down-regulated. Seven RBPs (PTBP1, PPIH, SMAD5, MSI2, RBM15, MRPS17, and ADAT3) were identified to be prognosis-related and adopted to construct a prognostic model. Compared with low-risk patients in TCGA training cohort, TCGA testing cohort and GEO cohort, high-risk patients had poorer overall survival (OS). The area under the ROC curves of this prognostic model were 0.804, 0.644 and 0.581 for TCGA training cohort, TCGA testing cohort and GEO cohort, respectively, justifying itself as a good prognostic model with reliable predictive ability. Using the seven identified RBPs, we then constructed a nomogram to generate a clinical utility model. The regulatory networks and functions of the seven RBPs were then investigated, the results of which demonstrated that MRPS17 and PTBP1 reduced the number of infiltrated immune cells. In-vitro experiments showed that the downregulation of PTBP1 weakened the migration and invasion capability of AGS and HGC27 cells.

Conclusion

The seven-gene signature can be used as a reliable STAD prognostic biomarker, and these findings help us better understand the prognostic roles and functions of RBPs in STAD.

A global and physical mechanism of gastric cancer formation and progression

Gastric cancer is regarded as a major health issue for human being nowadays. The Helicobacter pylori (H. pylori) infection has been found to accelerate the development of gastritis and gastric cancer. Significant efforts have been made towards the understanding of the biology of gastric cancer on both genetic and epigenetic levels. However the physical mechanism behind the gastric cancer formation is still elusive. In this study, we constructed a model for investigating gastric cancer formation by explored the gastric cancer landscape and the flow flux. We uncovered three stable state attractors on the landscape: normal, gastritis and gastric cancer. The definition of each attractor is based on the biological function and gene expression levels. The global stabilities and the switching processes were quantified through the barrier heights and dominant kinetic paths. To investigate the underlying mechanism of the process from normal through the gastritis to the gastric cancer caused by genetic or epigenetic factors, we simulate the oncogenesis of gastric cancer through changes of several gene regulation strengths and H. pylori infection. The simulated results can illustrate the developmental and metastasis process of gastric cancer. Different H. pylori infection degrees accelerating the process from gastritis to gastric cancer can be quantified. Then we applied global sensitivity analysis, one key gene and four key regulations were found. These results are consist with the experimental results and can be used to design the polygenic anti-cancer agents through multiple key genes or regulations. The landscape approach provides a physical and simple strategy for analyzing gastric cancer in a systematic and quantitative way. It also offers new insight into treatment strategy for gastric cancer by adjusting relevant polygenic genes and regulations.

HBXIP promotes gastric cancer via METTL3-mediated MYC mRNA m6A modification

Gastric cancer (GC) is one of the most common malignancies worldwide with limited treatment options and distinct geographical distribution even in countries such as China. Genetic alterations during its carcinogenesis need urgent elucidation. In this study, we propose an intriguing hypothesis that the hepatitis B X-interacting protein (HBXIP) may function as an oncogene in GC. We harvested 45 GC tissues and matched the paracancerous tissues. The c-myc proto-oncogene (MYC) N6-methyladenosine (m6A) mRNA methylation was detected by m6A RNA immunoprecipitation and dot-blot assays. Expressions of HBXIP, methyltransferase like 3 (METTL3) and MYC were all determined to be upregulated in both GC tissues and cells. Silencing HBXIP led to a decreased expression of METTL3, which inhibited GC cell proliferation, migration and invasion while promoting their apoptosis. Furthermore, METTL3 enhanced MYC m6A methylation and increased MYC translation, which could potentiate the proliferation, migration and invasion of GC cells. Finally, the HBXIP knockdown impeded the tumorigenicity of GC cells in vivo. Based on the findings of this study, we conclude that HBXIP plays an oncogenic role in GC via METTL3-mediated MYC mRNA m6A modification. The study offers a comprehensive understanding of HBXIP as a potential therapeutic target to limit GC progression.

Temozolomide-Induced RNA Interactome Uncovers Novel LncRNA Regulatory Loops in Glioblastoma

Simple Summary

Glioblastoma (GBM) is the most aggressive brain tumor and most resistant to therapy. The identification of novel predictive biomarkers or targets to counteract chemoresistance, requires a better understanding of the GBM primary response to therapy. The aim of our study was to assess the molecular response of GBM to the standard of care chemotherapy by temozolomide (TMZ). We established a comprehensive map of gene expression changes after treatment and discovered that GBM cells elicit a coordinated gene expression program after chemotherapy that differs between sensitive and resistant cells. We found that a novel class of genes expressed as long non-coding RNAs (lncRNAs) is involved in gene regulatory circuits in GBM and could represent novel markers of GBM patient prognosis. By shedding light on the involvement of the non-coding genome in GBM, our results may provide new mechanistic insight on lncRNAs and their importance in chemoresistance.

Abstract

Resistance to chemotherapy by temozolomide (TMZ) is a major cause of glioblastoma (GBM) recurrence. So far, attempts to characterize factors that contribute to TMZ sensitivity have largely focused on protein-coding genes, and failed to provide effective therapeutic targets. Long noncoding RNAs (lncRNAs) are essential regulators of epigenetic-driven cell diversification, yet, their contribution to the transcriptional response to drugs is less understood. Here, we performed RNA-seq and small RNA-seq to provide a comprehensive map of transcriptome regulation upon TMZ in patient-derived GBM stem-like cells displaying different drug sensitivity. In a search for regulatory mechanisms, we integrated thousands of molecular associations stored in public databases to generate a background “RNA interactome”. Our systems-level analysis uncovered a coordinated program of TMZ response reflected by regulatory circuits that involve transcription factors, mRNAs, miRNAs, and lncRNAs. We discovered 22 lncRNAs involved in regulatory loops and/or with functional relevance in drug response and prognostic value in gliomas. Thus, the investigation of TMZ-induced gene networks highlights novel RNA-based predictors of chemosensitivity in GBM. The computational modeling used to identify regulatory circuits underlying drug response and prioritizing gene candidates for functional validation is applicable to other datasets.

DPEP1 promotes the proliferation of colon cancer cells via the DPEP1/MYC feedback loop regulation

DPEP1 is highly expressed in the colorectal carcinoma tissues and colon cancer cells. However, the function and underlying mechanism of DPEP1 in the colon cancer cells are still poorly understood. Here, we found that transcription factor MYC could occupy on the DPEP1 promoter and activate its activities, and DPEP1 was up-regulated by MYC proteins in mRNA and protein levels in a dose-dependent manner in colon cancer cells. The expression levels of DPEP1 were positively correlated with that of MYC in colorectal tumor tissues. Moreover, Laser confocal images and Co-immunoprecipitation (Co-IP) revealed that DPEP1 and MYC proteins could bind to each other in the colon cancer cells. In turn, DPEP1 could enhance the stability of MYC proteins by extending the half-life of MYC proteins in colon cancer cells. Thus, DPEP1 and MYC proteins might form a positive feedback loop to maintain their high expression levels in colon cancer cells. In function, the MTT, EdU, Clone Formation assays and xenograft tumors assays demonstrated that DPEP1 could boost the proliferation of colon cancer cells through the DPEP1/MYC positive feedback loop in vitro and in vivo. Theoretically, DPEP1 may serve as a colon cancer biomarker and a novel target of colorectal carcinogenesis therapy.