Glia Maturation Factor Beta as a Novel Biomarker and Therapeutic Target for Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is one of the most common types of cancer. The novel sensitive biomarkers and therapeutic targets are urgently needed for the early diagnosis of HCC and improvement of clinical outcomes. Glia maturation factor-β (GMFB) is a growth and differentiation factor for both glia and neurons and has been found to be tightly involved in inflammation and neurodegeneration conditions. In our study, the expression level of GMFB was significantly up-regulated in patients with HCC and positively co-expression with tumor node metastases (TNM) stage and histopathological grade of HCC. The high expression level of GMFB was remarkably associated with poor overall survival, which mainly occurred in males rather than females. Multivariate analysis revealed GMFB to be an independent prognostic factor for overall survival in patients with HCC. Results of Gene Ontology (GO) and KEGG pathways analysis showed that down-regulation of pathways related to protein translation and mitochondria function were enriched. Protein-protein interaction analysis revealed the central role of mitochondria protein in HCC. The downregulation of genes involved in glycolysis and gluconeogenesis was observed among the co-expression genes of GMFB. Knockdown of GMFB in Hep3B significantly inhibited proliferation, migration, and invasion of Hep3B cells, and also downregulated the expression levels of some of metal matrix proteinase (MMP), increased mtDNA copy number and loss of mitochondrial transmembrane potential. GMFB influences the malignancy rate of HCC possibly through regulation of the expression of MMPs, mtDNA function and glycolysis. We proposed that GMFB was a promising HCC diagnostic and prognostic biomarker and therapeutic target in HCC.

Glia Maturation Factor-γ (GMFG) Promotes Ovarian Tumorigenesis and Chemoresistance via Activation of the FAK Signaling-Associated Focal Adhesion Dynamics

Background: Glia maturation factor-γ (GMFG) is reported to regulate actin cytoskeleton remodeling through the facilitation of actin debranching and nucleation suppression, which may be associated with cellular malignancy, but the role of GMFG in tumorigenesis remains largely unknown. Methods: By overexpression or silencing of GMFG in ovarian cancer cell lines, we show that GMFG enhances in vitro ovarian cancer cell proliferation, migration, invasion, and paclitaxel resistance and accelerates in vivo tumor growth and intraperitoneal metastasis in xenograft animal models. Results: The mechanistic study demonstrates that GMFG activates the FAK/Talin/Paxillin/Src signaling molecules via binding to p-FAK (Tyr397) and p-Talin (Ser425), whereas cell proliferation, migration and paclitaxel resistance induced by GMFG can be inversely suppressed by the chemical inhibition of p-FAK (Tyr397). Additionally, patients with high expression of GMFG exhibited a poor progression-free survival (PFS) (HR = 1.2, 95%CI: 1.05−1.37, P = 0.0069), and were significantly correlated with lymph node metastasis (P = 0.002) and venous invasion (P = 0.028). Conclusion: Our study suggests that GMFG may activate FAK signaling via binding to p-FAK (tyr397) and p-Talin (ser425) to promote ovarian tumorigenesis and chemoresistance. These findings indicate a functional interaction between GMFG and FAK pathway in ovarian tumorigenesis and chemoresistance. Thus, targeting the oncogenic GMFG-FAK axis may be a promising therapeutic strategy for ovarian cancer.

The Actin-Disassembly Protein Glia Maturation Factor γ Enhances Actin Remodeling and B Cell Antigen Receptor Signaling at the Immune Synapse

Signaling by the B cell antigen receptor (BCR) initiates actin remodeling. The assembly of branched actin networks that are nucleated by the Arp2/3 complex exert outward force on the plasma membrane, allowing B cells to form membrane protrusions that can scan the surface of antigen-presenting cells (APCs). The resulting Arp2/3 complex-dependent actin retrograde flow promotes the centripetal movement and progressive coalescence of BCR microclusters, which amplifies BCR signaling. Glia maturation factor γ (GMFγ) is an actin disassembly-protein that releases Arp2/3 complex-nucleated actin filaments from actin networks. By doing so, GMFγ could either oppose the actions of the Arp2/3 complex or support Arp2/3 complex-nucleated actin polymerization by contributing to the recycling of actin monomers and Arp2/3 complexes. We now show that reducing the levels of GMFγ in human B cell lines via transfection with a specific siRNA impairs the ability of B cells to spread on antigen-coated surfaces, decreases the velocity of actin retrograde flow, diminishes the coalescence of BCR microclusters into a central cluster at the B cell-APC contact site, and decreases APC-induced BCR signaling. These effects of depleting GMFγ are similar to what occurs when the Arp2/3 complex is inhibited. This suggests that GMFγ cooperates with the Arp2/3 complex to support BCR-induced actin remodeling and amplify BCR signaling at the immune synapse.

Bioinformatics and survival analysis of glia maturation factor-γ in pan-cancers

Background Glia maturation factor-γ (GMFG) is reported to inhibit the actin nucleation through binding to the actin-related protein-2/3 complex (Arp2/3). Considering the main function of GMFG in actin remodeling, which is vital for immune response, angiogenesis, cell division and motility, GMFG is supposed to have important roles in tumor development, while up to now, only two studies described the role of GMFG in cancers. By investigating the clinical values of GMFG using The Cancer Genome Atlas (TCGA) data and the functional mechanisms of GMFG through analyses of Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichments, this study was aimed to better understand the impact of GMFG in pan-cancers and to draw more attentions for the future research of GMFG. Methods RNA-seq and clinical data of cancer patients were collected from TCGA and analyzed by the Kaplan-Meier methods. GO and KEGG analyses were conducted using the online tools from the Database for Annotation, Visualization and Integrated Discovery (DAVID). Results Compared to the corresponding normal samples, GMFG was significantly upregulated in glioblastoma (GBM), kidney clear cell carcinoma (KIRC), lower grade glioma (LGG), acute myeloid leukemia (LAML), and pancreatic cancer (PAAD), testicular cancer (TGCT), but was downregulated in kidney chromophobe (KICH), lung adenocarcinoma (LUAD) and lung squamous cell carcinoma (LUSC) (P < 0.05 for all). High expression of GMFG predicted worse OS in GBM (HR = 1.5, P = 0.017), LGG (HR = 2.2, P < 0.001), LUSC (HR = 1.4, P = 0.022) and ocular melanomas (UVM) (HR = 7, P < 0.001), as well as worse DFS in LGG (HR = 1.8, P < 0.001) and prostate cancer (PRAD) (HR = 1.9, P = 0.004). In contrast, high expression of GMFG was associated with better OS in skin cutaneous melanoma (SKCM) (HR = 0.59, P < 0.001) and thymoma (THYM) (HR = 0.098, P = 0.031), as well as better DFS in bile duct cancer (CHOL) (HR = 0.2, P = 0.003). GMFG was mainly involved in the immune response, protein binding and cytokine-cytokine receptor interaction pathways, and was positively associated with multiple immunomodulators in most cancers. Conclusion Our study preliminarily identified that GMFG may cause different survivals for different cancers through modulating tumor progression, immune response status and tissue-specific tumor microenvironment (TME).

Glia Maturation Factor-Gamma Regulates Autophagy and Scavenger Receptor-Mediated Phagocytosis in Murine Macrophages

Autophagy and phagocytosis are critical processes involved in maintaining macrophage homeostasis and cellular immunity. Because dysfunction of autophagy is observed in many human pathologies, it is important to understand the regulatory mechanisms governing crosstalk between autophagy and phagocytosis. Glia maturation factor-gamma (GMFg) is a novel regulator of the Arp2/3 complex, its role in modulating autophagy and phagocytosis remains unknown. Here, we show that knockdown of GMFg in murine macrophages inhibited autophagosome formation and compromised lysosomal function. GMFg knockdown suppressed phosphorylation of liver kinase B1 (LKB1)/AMP-activated protein kinase (AMPK) signaling pathway components, suggesting a role for this pathway in GMFg regulation of autophagy. Moreover, GMFg-knockdown macrophages displayed increased the expression of scavenger-receptor MSR1 and CD36, which was dependent on activation of the nuclear factor erythroid 2-related factor 2 (Nrf2) transcription factor, and exhibited increased phagocytic activity. In contrast, overexpression of GMFg in murine macrophages increased autophagosome abundance and suppressed both scavenger-receptor expression and phagocytic activity. These findings suggest that GMFg regulates autophagy through AMPKregulated control of autophagosome formation, while mediating phagocytosis through modulation of scavenger-receptor abundance in macrophages, and may provide insight into therapeutic approaches to autophagy-related diseases and autophagy-regulated phagocytosis in immune and metabolic disorders.