Comparative Proteomic Analysis of Tumor Mesenchymal-Like Stem Cells Derived from High Grade versus Low Grade Gliomas

Understanding the immunosuppressive microenvironment of glioma: mechanistic insights and clinical perspectives

Glioblastoma (GBM), the predominant and primary malignant intracranial tumor, poses a formidable challenge due to its immunosuppressive microenvironment, thereby confounding conventional therapeutic interventions. Despite the established treatment regimen comprising surgical intervention, radiotherapy, temozolomide administration, and the exploration of emerging modalities such as immunotherapy and integration of medicine and engineering technology therapy, the efficacy of these approaches remains constrained, resulting in suboptimal prognostic outcomes. In recent years, intensive scrutiny of the inhibitory and immunosuppressive milieu within GBM has underscored the significance of cellular constituents of the GBM microenvironment and their interactions with malignant cells and neurons. Novel immune and targeted therapy strategies have emerged, offering promising avenues for advancing GBM treatment. One pivotal mechanism orchestrating immunosuppression in GBM involves the aggregation of myeloid-derived suppressor cells (MDSCs), glioma-associated macrophage/microglia (GAM), and regulatory T cells (Tregs). Among these, MDSCs, though constituting a minority (4-8%) of CD45+ cells in GBM, play a central component in fostering immune evasion and propelling tumor progression, angiogenesis, invasion, and metastasis. MDSCs deploy intricate immunosuppressive mechanisms that adapt to the dynamic tumor microenvironment (TME). Understanding the interplay between GBM and MDSCs provides a compelling basis for therapeutic interventions. This review seeks to elucidate the immune regulatory mechanisms inherent in the GBM microenvironment, explore existing therapeutic targets, and consolidate recent insights into MDSC induction and their contribution to GBM immunosuppression. Additionally, the review comprehensively surveys ongoing clinical trials and potential treatment strategies, envisioning a future where targeting MDSCs could reshape the immune landscape of GBM. Through the synergistic integration of immunotherapy with other therapeutic modalities, this approach can establish a multidisciplinary, multi-target paradigm, ultimately improving the prognosis and quality of life in patients with GBM.

Proteomics Study of Mesenchymal Stem Cell-Like Cells Obtained from Tumor Microenvironment of Patients with Malignant and Benign Salivary Gland Tumors

Objective

Salivary gland tumors (SGTs) show some aggressive and peculiar clinicopathological behaviors that might be related to the components of the tumor microenvironment, especially mesenchymal stem cells (MSCs)-associated proteins. However, the role of MSCs-related proteins in SGTs tumorigenesis is poorly understood. This study aimed to isolate and characterize MSCs from malignant and benign tumor tissues and to identify differentially expressed proteins between these two types of MSCs.

Materials and Methods

In this experimental study, MSC-like cells derived from benign (pleomorphic adenoma, n=5) and malignant (mucoepidermoid carcinoma, n=5) tumor tissues were verified by fluorochrome antibodies and flow cytometric analysis. Differentially expressed proteins were identified using two-dimensional polyacrylamide gel electrophoresis (2DE) and Mass spectrometry.

Results

Results showed that isolated cells strongly expressed characteristic MSCs markers such as CD44, CD73, CD90, CD105, and CD166, but they did not express or weakly expressed CD14, CD34, CD45 markers. Furthermore, the expression of CD24 and CD133 was absent or near absent in both isolated cells. Results also discovered overexpression of Annexin A4 (Anxa4), elongation factor 1-delta (EF1-D), FK506 binding protein 9 (FKBP9), cytosolic platelet-activating factor acetylhydrolase type IB subunit beta (PAFAH1B), type II transglutaminase (TG2), and s-formylglutathione hydrolase (FGH) in MSCs isolated from the malignant tissues. Additionally, heat shock protein 70 (Hsp70), as well as keratin, type II cytoskeletal 7 (CK-7), were found to be overexpressed in MSCs derived from the benign ones.

Conclusion

Malignant and benign SGTs probably exhibit a distinct pattern of tissue proteins that are most likely related to the metabolic pathway. However, further studies in a large number of patients are required to determine the applicability of identified proteins as new targets for cancer therapy.

Study on the differential proteomics of rat hippocampal mitochondria during deep hypothermic circulatory arrest

BACKGROUND

This study aimed to investigate the effect of deep hypothermic circulatory arrest (DHCA) on rat hippocampal mitochondrial protein expression and its differential proteomics, and explore the potential mechanisms behind the effect.

METHODS

We used internal jugular vein reflux and tail artery perfusion methods to establish the rat cardiopulmonary bypass (CPB) model. Rats were dissected to obtain the hippocampus, and the hippocampal mitochondria were purified. The mitochondrial morphology and the mitochondrial marker cytochrome C oxidase (COX) qualitatively examined via transmission electron microscopy and western-blot analysis, respectively. The qualified samples were subjected to isobaric tags for relative and absolute quantification (iTRAQ); we then established the CPB model again to obtain the rat hippocampus for cryoultramicrotomy, and used immunofluorescent double staining technique to qualitatively and semi-quantitatively verify two representative differentially expressed proteins.

RESULTS

By searching the Mascot 2.2 database, 29 differentially expressed proteins were obtained with statistical significance, including 21 known proteins and 8 unknowns. The expression level of COX and monoacylglycerol lipase did not change significantly (P>0.05) during the hyperacute phase; however, their intracellular localizations were altered.

CONCLUSIONS

DHCA induced the differential expression of 29 rat hippocampal mitochondrial proteins, some of which had altered intracellular localization. We speculated that the localized alteration of these proteins is one of the neuroprotection mechanisms that occurs during DHCA.

Mesenchymal Stromal-Like Cells in the Glioma Microenvironment: What Are These Cells?

The glioma microenvironment is a critical regulator of tumor progression. It contains different cellular components such as blood vessels, immune cells, and neuroglial cells. It also contains non-cellular components, such as the extracellular matrix, extracellular vesicles, and cytokines, and has certain physicochemical properties, such as low pH, hypoxia, elevated interstitial pressure, and impaired perfusion. This review focuses on a particular type of cells recently identified in the glioma microenvironment: glioma-associated stromal cells (GASCs). This is just one of a number of names given to these mesenchymal stromal-like cells, which have phenotypic and functional properties similar to those of mesenchymal stem cells and cancer-associated fibroblasts. Their close proximity to blood vessels may provide a permissive environment, facilitating angiogenesis, invasion, and tumor growth. Additional studies are required to characterize these cells further and to analyze their role in tumor resistance and recurrence.

Perspectives for Ezrin and Radixin in Astrocytes: Kinases, Functions and Pathology

Astrocytes are increasingly perceived as active partners in physiological brain function and behaviour. The structural correlations of the glia–synaptic interaction are the peripheral astrocyte processes (PAPs), where ezrin and radixin, the two astrocytic members of the ezrin-radixin-moesin (ERM) family of proteins are preferentially localised. While the molecular mechanisms of ERM (in)activation appear universal, at least in mammalian cells, and have been studied in great detail, the actual ezrin and radixin kinases, phosphatases and binding partners appear cell type specific and may be multiplexed within a cell. In astrocytes, ezrin is involved in process motility, which can be stimulated by the neurotransmitter glutamate, through activation of the glial metabotropic glutamate receptors (mGluRs) 3 or 5. However, it has remained open how this mGluR stimulus is transduced to ezrin activation. Knowing upstream signals of ezrin activation, ezrin kinase(s), and membrane-bound binding partners of ezrin in astrocytes might open new approaches to the glial role in brain function. Ezrin has also been implicated in invasive behaviour of astrocytomas, and glial activation. Here, we review data pertaining to potential molecular interaction partners of ezrin in astrocytes, with a focus on PKC and GRK2, and in gliomas and other diseases, to stimulate further research on their potential roles in glia-synaptic physiology and pathology.

Oncogenic transgelin-2 is differentially regulated in isocitrate dehydrogenase wild-type vs. mutant gliomas

The presence of an isocitrate dehydrogenase (IDH1/2) mutation in gliomas is associated with favorable outcomes compared to gliomas without the mutation (IDH1/2 wild-type, WT). The underlying biological mechanisms accounting for improved clinical outcomes in IDH1/2 mutant gliomas remain poorly understood, but may, in part, be due to the glioma CpG island methylator phenotype (G-CIMP) and epigenetic silencing of genes. We performed profiling of IDH1/2 WT versus IDH1/2 mutant Grade II and III gliomas and identified transgelin-2 (TAGLN2), an oncogene and actin-polymerizing protein, to be expressed at significantly higher levels in IDH1/2 WT gliomas compared to IDH1/2 mutant gliomas. This differential expression of TAGLN2 was primarily due to promoter hypermethylation in IDH1/2 mutant gliomas, suggesting involvement of TAGLN2 in the G-CIMP. Our results also suggest that TAGLN2 may be involved in progression due to higher expression in glioblastomas compared to IDH1/2 WT gliomas of lower grades. Furthermore, our results suggest that TAGLN2 functions as an oncogene by contributing to proliferation and invasion when overexpressed in IDH1/2 WT glioma cells. Taken together, this study demonstrates a possible link between increased TAGLN2 expression, invasion and poor patient outcomes in IDH1/2 WT gliomas and identifies TAGLN2 as a potential novel therapeutic target for IDH1/2 WT gliomas.