Immunobiology and immunotherapeutic targeting of glioma stem cells

EFNB1 drives glioma progression and shapes the immune microenvironment: a potential prognostic biomarker

Gliomas, a heterogeneous group of tumors affecting the brain and spinal cord, present a significant clinical challenge. Ephrin B1 (EFNB1) has been implicated in various malignancies. However, its role in gliomas remained poorly understood. Hence, this study aimed to elucidate the connection between EFNB1 and the progression of glioma. A retrospective RNA-seq analysis was conducted by utilizing the data from glioma patients in the TCGA and CGGA databases. Kaplan-Meier survival analysis and multivariate regression models were employed to evaluate the prognostic significance of EFNB1. RT-PCR was used to quantify EFNB1 expression in glioma tissues and cell lines. Meanwhile, in vitro assays were carried out to assess its functional roles in glioma cells. Our findings demonstrated that EFNB1 expression was significantly elevated in gliomas and other cancers. Moreover, high EFNB1 expression was closely correlated with advanced clinical stages and poor prognosis. Notably, multivariate analysis identified EFNB1 as an independent prognostic factor for overall survival. KEGG pathway analysis suggested that EFNB1 was involved in critical biological processes, including the cell cycle, protein processing in the endoplasmic reticulum, Epstein-Barr virus infection, and Salmonella infection. Furthermore, EFNB1 expression was associated with immune cell infiltration, particularly Th2 cells, macrophages, and plasmacytoid dendritic cells. In glioma cells, EFNB1 expression was markedly increased. Consequently, functional experiments demonstrated that EFNB1 knockdown inhibited glioma cell proliferation, invasion, and migration. These results highlighted EFNB1 as a novel independent prognostic biomarker and suggest its potential role in shaping the immunological microenvironment of gliomas.

Suppression of FAM83D Inhibits Glioma Proliferation, Invasion and Migration by Regulating the AKT/mTOR Signaling Pathway

•

FAM83D is upregulated in the glioma cells and tissues.

•

Silencing FAM83D inhibits the proliferation, invasion and migration of glioma cells.

•

Silencing FAM83D inhibits the activity of AKT/mTOR signaling pathway.

•

FAM83D inhibition limits the in vivo growth of glioma cells.

Objective

To explore the mechanism by which the family with sequence similarity 83, member D (FAM83D)-mediated AKT/mTOR signaling pathway activation affects the proliferation and metastasis of glioma cells.

Methods

FAM83D protein expression in glioma cells and tissues was detected by western blotting. Glioma U87 and U251 cells were selected and divided into the Mock, siNC, siFAM83D, FAM83D, MK2206 and FAM83D + MK2206 groups. Cell proliferation was assessed by MTT (3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide) and clone formation assays, while invasion and migration were evaluated by Transwell assays and wound healing tests. The protein expression of members of the AKT/mTOR pathway was determined via western blotting. Xenograft models were also established in nude mice to observe the in vivo effect of FAM83D on the growth of glioma.

Results

FAM83D was upregulated in glioma patients, especially in those with Stage III-IV. In addition, cells treated with siFAM83D had significant downregulation of p-AKT/AKT and p-mTOR/mTOR, with decreased proliferation and colony numbers, as well as decreased invasion and migration compared to the Mock group. However, FAM83D overexpression could activate the Akt/mTOR pathway and promote the proliferation, invasion and migration of glioma cells. Moreover, treatment with MK2206, an inhibitor of AKT, reversed the promoting effect of FAM83D on the growth of glioma cells. The in vivo experiments demonstrated that silencing FAM83D could inhibit the in vivo growth of glioma cells

Conclusion

FAM83D was upregulated in glioma and silencing FAM83D suppressed the proliferation, invasion and migration of glioma cells via inhibition of the AKT/mTOR pathway.

Preclinical evaluation of binimetinib (MEK162) delivered via polymeric nanocarriers in combination with radiation and temozolomide in glioma

Background and purpose

Glioblastoma multiforme (GBM) is the most aggressive subtype of malignant gliomas, with an average survival rate of 15 months after diagnosis. More than 90% of all GBMs have activating mutations in the MAPK/ERK pathway. Recently, we showed the allosteric MEK1/2 inhibitor binimetinib (MEK162) to inhibit cell proliferation and to enhance the effect of radiation in preclinical human GBM models. Because the free drug cannot pass the blood–brain barrier (BBB), we investigated the use of nanocarriers for transport of the drug through the BBB and its efficacy when combined with radiotherapy and temozolomide (TMZ) in glioma spheroids.

Methods

In vitro studies were performed using multicellular U87 human GBM spheroids. Polymeric nanocarriers (polymersomes) were loaded with MEK162. The interaction between nanocarrier delivered MEK162, irradiation and TMZ was studied on the kinetics of spheroid growth and on protein expression in the MAPK/ERK pathway. BBB passaging was evaluated in a transwell system with human cerebral microvascular endothelial (hCMEC/D3) cells.

Results

MEK162 loaded polymersomes inhibited spheroid growth. A synergistic effect was found in combination with fractionated irradiation and an additive effect with TMZ on spheroid volume reduction. Fluorescent labeled polymersomes were taken up by human cerebral microvascular endothelial cells and passed the BBB in vitro.

Conclusion

MEK162 loaded polymersomes are taken up by multicellular spheroids. The nanocarrier delivered drug reduced spheroid growth and inhibited its molecular target. MEK162 delivered via polymersomes showed interaction with irradiation and TMZ. The polymersomes crossed the in vitro BBB model and therewith offer exciting challenges ahead for delivery of therapeutics agents to brain tumours.

Autophagy activation promotes bevacizumab resistance in glioblastoma by suppressing Akt/mTOR signaling pathway

Glioblastomas are the most common primary and malignant brain tumors. The standard therapy includes surgery and radiotherapy plus chemotherapy, with additional bevacizumab to block the angiogenesis in tumors. However, the ever-growing tolerance of glioblastomas to chemotherapeutic drugs impairs the clinical outputs of tumor treatment. The present study investigated the tolerance of glioblastomas to bevacizumab. Although bevacizumab resulted in direct anti-proliferation and pro-apoptosis effects on glioblastoma cells via downregulating the anti-apoptotic proteins and upregulating the pro-apoptotic proteins, tolerance was also encountered that was mainly caused by autophagy induction in tumor cells. The suppressed Akt-mTOR signaling pathway led to the upregulated autophagy process. Blockade of the autophagy process significantly increased the tumor-suppressive effect of bevacizumab on glioblastoma cells. To our knowledge, the present study is the first to report the involvement of autophagy in the tolerance of glioblastomas to bevacizumab. Therefore, autophagy inhibition may be considered a novel way to overcome the tolerance of glioblastomas to anti-angiogenic agents.

Single vs. combination immunotherapeutic strategies for glioma

INTRODUCTION

Malignant gliomas are highly invasive tumors, associated with a dismal survival rate despite standard of care, which includes surgical resection, radiotherapy and chemotherapy with temozolomide (TMZ). Precision immunotherapies or combinations of immunotherapies that target unique tumor-specific features may substantially improve upon existing treatments. Areas covered: Clinical trials of single immunotherapies have shown therapeutic potential in high-grade glioma patients, and emerging preclinical studies indicate that combinations of immunotherapies may be more effective than monotherapies. In this review, the authors discuss emerging combinations of immunotherapies and compare efficacy of single vs. combined therapies tested in preclinical brain tumor models. Expert opinion: Malignant gliomas are characterized by a number of factors which may limit the success of single immunotherapies including inter-tumor and intra-tumor heterogeneity, intrinsic resistance to traditional therapies, immunosuppression, and immune selection for tumor cells with low antigenicity. Combination of therapies which target multiple aspects of tumor physiology are likely to be more effective than single therapies. While a limited number of combination immunotherapies are described which are currently being tested in preclinical and clinical studies, the field is expanding at an astounding rate, and endless combinations remain open for exploration.

Radiation-induced brain injury: low-hanging fruit for neuroregeneration

Brain radiation is a fundamental tool in neurooncology to improve local tumor control, but it leads to profound and progressive impairments in cognitive function. Increased attention to quality of life in neurooncology has accelerated efforts to understand and ameliorate radiation-induced cognitive sequelae. Such progress has coincided with a new understanding of the role of CNS progenitor cell populations in normal cognition and in their potential utility for the treatment of neurological diseases. The irradiated brain exhibits a host of biochemical and cellular derangements, including loss of endogenous neurogenesis, demyelination, and ablation of endogenous oligodendrocyte progenitor cells. These changes, in combination with a state of chronic neuroinflammation, underlie impairments in memory, attention, executive function, and acquisition of motor and language skills. Animal models of radiation-induced brain injury have demonstrated a robust capacity of both neural stem cells and oligodendrocyte progenitor cells to restore cognitive function after brain irradiation, likely through a combination of cell replacement and trophic effects. Oligodendrocyte progenitor cells exhibit a remarkable capacity to migrate, integrate, and functionally remyelinate damaged white matter tracts in a variety of preclinical models. The authors here critically address the opportunities and challenges in translating regenerative cell therapies from rodents to humans. Although valiant attempts to translate neuroprotective therapies in recent decades have almost uniformly failed, the authors make the case that harnessing human radiation-induced brain injury as a scientific tool represents a unique opportunity to both successfully translate a neuroregenerative therapy and to acquire tools to facilitate future restorative therapies for human traumatic and degenerative diseases of the central nervous system.

Cigarette smoking and risk of adult glioma: a meta-analysis of 24 observational studies involving more than 2.3 million individuals

Background

Cigarette smoking has been shown to be a risk factor for adult glioma by some but not all studies. We conducted a meta-analysis to systematically assess the potential association.

Methods

PubMed and EMBASE were searched from the date of their inception to October 1, 2015, to identify relevant articles. Reference lists from these articles were reviewed to identify additional studies. Both cohort and case–control studies were included. Fixed-effects models were used to calculate the overall relative risk (RR) with corresponding 95% confidence intervals (CIs).

Results

The final analysis included 24 studies (seven cohort and 17 case–control studies), involving more than 2.3 million individuals. The combined RR was 1.04 (95% CI: 1.00, 1.09; P=0.073) for ever-smokers, 0.97 (95% CI: 0.88, 1.07; P=0.574) for current-smokers, and 1.07 (95% CI: 0.98, 1.16; P=0.130) for past smokers, with little evidence of heterogeneity. Omission of any single study from the analysis had little effect on the result. No evidence of publication bias was found. A small but statistically significant increase was found in past smokers in females (RR: 1.13, 95% CI: 1.00, 1.28; P=0.046) but not in males.

Conclusion

In general, there was no association between cigarette smoking and adult glioma. The small but statistically significant association in females requires further investigation.