MGAT1 is a novel transcriptional target of Wnt/β-catenin signaling pathway

Insights into the role of glycosyltransferase in the targeted treatment of gastric cancer

Gastric cancer is a remarkably heterogeneous tumor. Despite some advances in the diagnosis and treatment of gastric cancer in recent years, the precise treatment and curative outcomes remain unsatisfactory. Poor prognosis continues to pose a major challenge in gastric cancer. Therefore, it is imperative to identify effective targets to improve the treatment and prognosis of gastric cancer patients. It should be noted that glycosylation, a novel form of posttranslational modification, is a process capable of regulating protein function and influencing cellular activities. Currently, numerous studies have shown that glycosylation plays vital roles in the occurrence and progression of gastric cancer. As crucial enzymes that regulate glycan synthesis in glycosylation processes, glycosyltransferases are potential targets for treating GC. Hence, investigating the regulation of glycosyltransferases and the expression of associated proteins in gastric cancer cells is highly important. In this review, the related glycosyltransferases and their related signaling pathways in gastric cancer, as well as the existing inhibitors of glycosyltransferases, provide more possibilities for targeted therapies for gastric cancer.

PRAME Expression: A Target for Cancer Immunotherapy and a Prognostic Factor in Uveal Melanoma

Purpose

Uveal melanoma (UM) is a rare disease with a high mortality, and new therapeutic options are being investigated. Preferentially Expressed Antigen in Melanoma (PRAME) is a cancer testis antigen, expressed in the testis, but also in cancers, including uveal melanoma. PRAME is considered a target for immune therapy in several cancers, and PRAME-specific T cell clones have been shown to kill UM cells.

Methods

We studied the literature on PRAME expression in hematological and solid malignancies, including UM, and its role as a target for immunotherapy. The distribution of tumor features was compared between PRAME-high and PRAME-low UM in a 64-patient cohort from the Leiden University Medical Center (LUMC) and in the Cancer Genome Atlas (TCGA) cohort of 80 cases and differential gene expression analysis was performed in the LUMC cohort.

Results

PRAME is expressed in many malignancies, it is frequently associated with a negative prognosis, and can be the target of T cell receptor (TCR)-transduced T cells, a promising treatment option with high avidity and safety. In UM, PRAME is expressed in 26% to 45% of cases and is correlated with a worse prognosis. In the LUMC and the TCGA cohorts, high PRAME expression was associated with larger diameter, higher Tumor-Node-Metastasis (TNM) stage, more frequent gain of chromosome 8q, and an inflammatory phenotype.

Conclusions

We confirm that PRAME is associated with poor prognosis in UM and has a strong connection with extra copies of 8q. We show that PRAME-specific immunotherapy in an adjuvant setting is promising in treatment of malignancies, including UM.

PA-MSHA Regulates PD-L1 Expression in Hepatoma Cells

BACKGROUND

Programmed death ligand 1 (PD-L1) is expressed in hepatocellular carcinoma (HCC) cells. PD-L1 function and structure are regulated through glycosylation and various signaling pathways. However, the relationship between Pseudomonas aeruginosa mannose sensitive hemagglutinin (PA-MSHA), glycosylation and PD-L1 warrants further study. In this study, we investigated the effects of PA-MSHA on the regulation of mannosyl and N-glycosylation to identify the mechanisms underlying its function.

METHODS

PD-L1, β-catenin, c-Myc, mannosyl, MGAT1 and mannosidase II in HCC were identified by postoperative specimens from the HCC cohort with immunohistochemistry and immunofluorescence. PA-MSHA was used to suppress tumor progression. Alterations to the expression of PD-L1, β-catenin, c-Myc, MGAT1, and mannosidase II at the gene and protein levels were detected by qRT-PCR and Western blot analysis. Soluble PD-L1 (sPD-L1) were detected using enzyme-linked immunosorbent assay.

RESULTS

Mannosyl and mannosidase II expression levels increased, whereas those of MGAT1 decreased in the HCC cells. The glycosylation-related pathway proteins, namely, β-catenin, c-Myc and PD-L1, had increased expression levels. Moreover, proliferation in the HCC cells was inhibited after PA-MSHA treatment, PD-L1 function was significantly inhibited. Transmission electron microscopy showed that PA-MSHA penetrated into the HCC cytoplasm through the cytomembrane, resulting in apoptosis. Here, PA-MSHA significantly reduced sPD-L1 expression levels in the tumor cells.

CONCLUSIONS

PA-MSHA plays the role of a lectin, affecting receptors on the cytomembrane. This strain inhibits mannosyl by suppressing β-catenin signaling. We hypothesized that PA-MSHA suppresses PD-L1 by: 1. Inhibiting the glycosylation process; and 2. Suppressing β-catenin and c-Myc, thereby reducing the transcription of this protein.

MicroRNA miR-331-3p suppresses osteosarcoma progression via the Bcl-2/Bax and Wnt/β-Catenin signaling pathways and the epithelial-mesenchymal transition by targeting N-acetylglucosaminyltransferase I (MGAT1)

Osteosarcoma (OS) is a high-grade malignant disease that is a prevalent primary malignant sarcoma of the bone. The purpose of this investigation was to therefore elucidate the association between miR-331-3p and OS development and to identify a potential underlying mechanism. Key genes involved in OS were selected using GSE65071 dataset from the Gene Expression Omnibus (GEO) database and Gene Expression Profiling Interactive Analysis (GEPIA). Reverse transcription quantitative polymerase chain reaction (RT-qPCR) and Western blotting were conducted to detect miR-331-3p, MGAT1, the epithelial-mesenchymal transition (EMT), Bcl-2/Bax and Wnt/β-Catenin signaling pathways related proteins. Dual-luciferase reporter assay and TargetScan were used for validating interaction between MGAT1 mRNA and miR-331-3p. Biological effects of miR-331-3p and MGAT1 on OS cells were detected employing MTT, Transwell, wound healing and flow cytometry, respectively. MiR-331-3p was under-expressed in OS, and up-regulation or inhibition of its expression could significantly inhibit or promote the malignant phenotypes of OS cells. Furthermore, we found that MGAT1, a target of miR-331-3p, had elevated expression in OS. Interestingly, MGAT1 could partially alleviate the effect of miR-331-3p in vitro. Collectively, miR-331-3p acts as an critical tumor suppressor through inhibiting MGAT1, results in suppressed Wnt/β-Catenin pathway and decreased proliferation of OS cells; leads to increased apoptosis via Bcl-2/Bax pathway and inhibited migration and invasion ability via the EMT.

Step-by-Step Construction of Gene Co-Expression Network Analysis for Identifying Novel Biomarkers of Sepsis Occurrence and Progression

Background

Sepsis is the leading cause of death in critically ill patients. Although it is well known that the immune system plays a key role in sepsis, exactly how it works remains unknown.

Methods

In our study, we used weighted gene co-expression network analysis (WGCNA) to screen out the immune-related genes that may play a critical role in the process of sepsis.

Results

A total of three sepsis-related hub genes were screened for further verification. Subsequent analysis of immune subtypes suggested their potential predictive effect in the clinic.

Conclusion

Our study shows that three immune-related genes CHMP1A, MED15 and MGAT1 are important biomarkers of sepsis. The screened genes may help to distinguish normal individuals from patients with different degrees of sepsis.

Abnormal Expression and Prognosis Value of COG Complex Members in Kidney Renal Clear Cell Carcinoma (KIRC)

Kidney renal clear cell carcinoma (KIRC) is the most aggressive subtype of kidney tumours with poor prognosis as well as the increasing incidence rate in worldwide. The conserved oligomeric Golgi (COG) complex is an eight-subunit (Cog1-8) peripheral Golgi protein that controls membrane trafficking and protein glycosylation and plays vital roles in human disease including cancers. Therefore, to uncover the prognostic value of COG complex in KIRC, a series of databases, including UALCAN database, GEPIA database, and Kaplan-Meier plotter, were used to analyse the mRNA expression of COG complex subunits and their prognostic values in patients with KIRC in this study. Compared with normal counterparts, mRNA expression of six COG complex subunits was significantly downregulated in KIRC tissue in UALCAN database, while COG4 mRNA expression was significantly upregulated in KIRC tissue. Moreover, the survival analysis indicated that all members of COG complex subunits were closely related with the prognosis of KIRC patients, while COG1 and COG4 were significantly associated with unfavourable overall survival (OS), the rest of COG complex subunits were importantly correlated with favourable OS. Simultaneously, higher mRNA expression of COG3, COG6, and COG8 exhibits better progression-free survival (PFS) and disease-free survival (DFS) in KIRC patients. These results identified that COG complex subunits, especially COG3, COG6, and COG8, are potential prognostic biomarkers of KIRC patients and may offer effective and new strategies for more accurately diagnosing the patients with KIRC in advance.

A comprehensive analysis of immune infiltration in the tumor microenvironment of osteosarcoma

Background

Even though immunotherapy has been an effective treatment for solid tumors, its efficacy in osteosarcoma remains sub‐optimal. It is therefore imperative to understand the complex tumor microenvironment (TME) of osteosarcoma to facilitate the development of immunotherapies against this cancer.

Methods

The mRNA expression profiles of osteosarcoma tissues were downloaded from The Cancer Genome Atlas (TCGA) database. Next, the ssGSEA, MCP‐counter, CIBERSORT, and Xcell algorithm analyses were performed to characterize the tumor microenvironment of osteosarcoma tissues. The tumor tissues were divided into inflammatory and non‐inflammatory. A comprehensive assessment of immune cell infiltration in osteosarcoma tissues was then performed. Sub‐group analysis of immune cell infiltration between men and women patients with osteosarcoma was also carried out.

Results

The results revealed that the infiltration of immune cells including activated B cell, activated CD8 T cell, CD56dim natural killer cell, and cytotoxic lymphocytes cells, in osteosarcoma tissues was higher in male than in female patients. Based on the infiltration profile of different immune cells, the osteosarcoma tissues were grouped into four clusters. The four clusters were further divided into hot and cold tumors. The differently expressed genes (DEGs) between cold and hot tumors were mainly associated with the activation and regulation of immune response. Additionally, a neuronal pentraxin (NPTX2) expression which was upregulated in cold tumors was found to be negatively correlated with the expression of CD8a Molecule (CD8A), Granzyme B (GZMB), and Interferon Gamma (IFNG). NPTX2 decreased CCL4 secretion. Knockdown of NPTX2 in osteosarcoma cells inhibited tumor growth and increased tumor cell apoptosis. Moreover, a prognosis prediction model of osteosarcoma was constructed and validated in patients receiving immunotherapy using external data.

Conclusions

To the best of our knowledge, this is the first study to characterize the infiltration of immune cells in osteosarcoma tissues from patients receiving immune infiltration therapy.

Identification of Prognostic Genes in Leiomyosarcoma by Gene Co-Expression Network Analysis

Background/Aims

Leiomyosarcoma (LMS) is a tumor derived from malignant mesenchymal tissue associated with poor prognosis. Determining potential prognostic markers for LMS can provide clues for early diagnosis, recurrence, and treatment.

Methods

RNA sequence data and clinical features of 103 LMS were obtained from the Cancer Genome Atlas (TCGA) database. Application Weighted Gene Co-Expression Network Analysis (WGCNA) was used to construct a free-scale gene co-expression network, to study the interrelationship between its potential modules and clinical features, and to identify hub genes in the module. The hub gene function was verified by an external database.

Results

Twenty-four co-expression modules were constructed using WGCNA. A dark red co-expression module was found to be significantly associated with disease recurrence. Functional enrichment analysis and GEPIA and ONCOMINE database analyses demonstrated that hub genes CDK4, CCT2, and MGAT1 may play an important role in LMS recurrence.

Conclusion

Our study constructed an LMS co-expressing gene module and identified prognostic markers for LMS recurrence detection and treatment.

N-acetylglucosaminyltransferase I promotes glioma cell proliferation and migration through increasing the stability of the glucose transporter GLUT1

Abnormal alteration of N-glycosylation structure contributes to glioma progression. N-acetylglucosaminyltransferase I (MGAT1) plays an essential role in the conversion of processed high-mannose cores into complex or hybrid N-linked oligosaccharide structures. The function of MGAT1 in glioma development remains largely unknown. Here, we found that the expression of MGAT1 is higher in glioblastoma compared to normal brain tissues. Inhibition of EGFR signalling pathway or serum starvation reduces MGAT1 expression. Knockdown of MGAT1 inhibits glioma cell proliferation and migration. Furthermore, MGAT1 promotes complex N-glycosylation of glucose transporter 1 (Glut1) and increases Glut1 protein levels. In summary, our findings indicate that MGAT1 is highly expressed in glioblastoma and promotes glioma cells at least partly through upregulation of Glut1 protein.

MicroRNA-329 upregulation impairs the HMGB2/β-catenin pathway and regulates cell biological behaviors in melanoma

Melanoma is responsible for the majority of deaths caused by skin cancer. Antitumor activity of microRNA-329 (miR-329) has been seen in several human cancers. In this study, we identify whether miR-329 serves as a candidate regulator in melanoma. Melanoma-related differentially expressed genes were screened with its potential molecular mechanism predicted. Melanoma tissues and pigmented nevus tissues were collected, where the levels of miR-329 and high-mobility group box 2 (HMGB2) were determined. To characterize the regulatory role of miR-329 on HMGB2 and the β-catenin pathway in melanoma cell activities, miR-329 mimics, miR-329 inhibitors, and siRNA-HMGB2 were transfected into melanoma cells. Cell viability, migration, invasion, cell cycle, and apoptosis were assessed. miR-329 was predicted to influence melanoma by targeting HMGB2 via the β-catenin pathway. High level of HMGB2 and low miR-329 expression were observed in melanoma tissues. HMGB2 was targeted and negatively regulated by miR-329. In melanoma cells transfected with miR-329 mimics or siRNA-HMGB2, cell proliferation, migration, and invasion were impeded, yet cell cycle arrest and apoptosis were promoted, corresponding to decreased levels of β-catenin, cyclin D1, and vimentin and increased levels of GSK3β and E-cadherin. Collectively, our results show that miR-329 can suppress the melanoma progression by downregulating HMGB2 via the β-catenin pathway.

Identification of IFITM3 and MGAT1 as novel interaction partners of BRI3 by yeast two-hybrid screening

BRI3 (brain protein I3) is one of the Wnt/β-catenin pathway target genes as indicated by the results of serial analysis of gene expression (SAGE) and microarray analyses performed in our laboratory. The Wnt/β-catenin signaling pathway is an evolutionarily conserved pathway, which has important functions in early vertebrate development, axis formation, cellular proliferation, and morphogenesis. Previous studies showed that BRI3 expression is upregulated at both mRNA and protein levels upon β-catenin activation by various approaches, such as lithium treatment and overexpression of Wnt ligands in Huh7 (hepatocellular carcinoma) cell lines. Moreover, with regard to the previous literature, BRI3 was found to have a very important role in the TNFα-mediated cell death pathway. In this study, we screened a human liver cDNA library by yeast two-hybrid assay using BRI3 protein as bait, with the aim of finding novel interaction partners of BRI3. Library screening by yeast mating resulted in the identification of three candidate positive clones. Among these, IFITM3 and MGAT1 proteins were confirmed as interaction partners by using cotransformation in yeast cells and coimmunoprecipitation from mammalian cell lines. Considering the poor functional characterization of BRI3 to date, identification of novel BRI3-interacting proteins is an essential first step in determining the action mechanism of BRI3 with respect to the Wnt/β-catenin pathway.

Induced pluripotent stem cell-derived conditional medium promotes Leydig cell anti-apoptosis and proliferation via autophagy and Wnt/β-catenin pathway

Leydig cell transplantation is a better alternative in the treatment of androgen-deficient males. The main purpose of this study was to investigate the effects of induced pluripotent stem cell-derived conditioned medium (iPS-CM) on the anti-apoptosis, proliferation and function of immature Leydig cells (ILCs), and illuminate the underlying mechanisms. ILCs were exposed to 200 μmol/L hydrogen peroxide (H2 O2 ) for 24 hours with or without iPS-CM treatments. Cell apoptosis was detected by flow cytometric analysis. Cell proliferation was assessed using cell cycle assays and EdU staining. The steroidogenic enzyme expressions were quantified with Western blotting. The results showed that iPS-CM significantly reduced H2 O2 -induced ILC apoptosis through down-regulation of autophagic and apoptotic proteins LC3-I/II, Beclin-1, P62, P53 and BAX as well as up-regulation of BCL-2, which could be inhibited by LY294002 (25 μmol/L). iPS-CM could also promote ILC proliferation through up-regulation of β-catenin and its target proteins cyclin D1, c-Myc and survivin, but was inhibited by XAV939 (10 μmol/L). The level of bFGF in iPS-CM was higher than that of DMEM-LG. Exogenous bFGF (20 ng/mL) or Wnt signalling agonist lithium chloride (LiCl) (20 mmol/L) added into DMEM-LG could achieve the similar effects of iPS-CM. Meanwhile, iPS-CM could improve the medium testosterone levels and up-regulation of LHCGR, SCARB1, STAR, CYP11A1, HSD3B1, CYP17A1, HSD17B3 and SF-1 in H2 O2 -induced ILCs. In conclusion, iPS-CM could reduce H2 O2 -induced ILC apoptosis through the activation of autophagy, promote proliferation through up-regulation of Wnt/β-catenin pathway and enhance testosterone production through increasing steroidogenic enzyme expressions, which might be used in regenerative medicine for future.