The Anti-Warburg Effect Elicited by the cAMP-PGC1α Pathway Drives Differentiation of Glioblastoma Cells into Astrocytes

Activated KRAS reprograms neural progenitor cells to glioma stem cell‑like phenotype

Glioma is the most common primary brain tumor. Glioma stem cells (GSCs) are the origin of gliomagenesis and may develop from normal neural progenitor cells (NPCs). However, how neoplastic transformation occurs in normal NPCs and the role of the Ras/Raf/MAPK pathway in NPC transformation is unclear. The present study generated NPCs from human embryonic stem cells (ESCs) carrying gene alterations in the Ras/Raf/MAPK pathway. The CCK‑8 proliferation, single‑cell clonal expansion, cell migration, RT‑qPCR, immunofluorescence staining, western blotting, transcriptome and Seahorse analyses, and intracranial implantation assay were performed to identify the characterization of transformed NPCs in vitro and in vivo. Brain organoids were used to verify the phenotypes transforming in NPCs. KRAS‑activated NPCs exhibited increased proliferation and migration in vitro. KRAS‑activated NPCs showed atypical morphology and formed aggressive tumors in immunodeficient mice. At the molecular level, KRAS‑activated NPCs displayed neoplasm‑associated metabolic and gene expression profiles. Moreover, activation of KRAS led to substantial cell proliferation and abnormal structure in ESC‑derived brain organoids. The present study showed that activated KRAS transformed normal NPCs to GSC‑like cells and established a simple cellular model to investigate gliomagenesis.

Significant Systemic Insulin Resistance is Associated With Unique Glioblastoma Multiforme Phenotype

Background

Some glioblastoma multiforme (GBM) are characterized by the presence of gemistocytes (GCs), a unique phenotype of reactive astrocytes. Certain GCs can be identified as neoplastic cells but these cells were also found to be associated with diabetes in non-neoplastic lesions of the central nervous system. Our aim was to find a correlation between insulin - resistance metabolic features and the presence of GCs in patients with newly diagnosed GBM.

Methods

Medical records from histologically confirmed GBM patients were retrospectively extracted for different systemic metabolic variables. A statistic-based comparison was made between GBM, diabetic patients with and without GC. Patients with poorly controlled diabetes (ie, hemoglobin A1C ⩾ 8.0) were also compared between the 2 groups.

Results

A total of 220 newly diagnosed GBM patients were included in our study. 58 (26.3%) patients had a history of diabetes mellitus type 2 (DM2) at the time of admission. The rate of poorly-controlled DM2 was nearly as twice in the GC-GBM group than in the non-GC GBM group (18.75% vs 9.5%; P = .130). In the DM2 cohort, the subgroup of GC-GBM was significantly associated with demographic and metabolic features related to insulin resistance such as male gender predominance (89% vs 50%, P = .073) and morbid obesity (weight ⩾85 kg: OR 6.16; P = .0019 and mean BMI: 34.1 ± 11.42 vs 28.7 ± 5.44; P = .034 for group with and without GCs, respectively). In the poorly-controlled DM2 group, none of the GC-GBM patients were using insulin prior to diagnosis, compared to 61.1% in the non-GC GBM patients (OR = 0.04, P = .045).

Conclusion

Systemic metabolic factors related to marked insulin resistance (DM2, morbid obesity, male gender) are associated with a unique histologic phenotype of GBM, characterized by the presence of GCs. This feature is prominent in poorly-controlled DM2 GBM patients who are not using synthetic insulin. This novel finding may add to the growing data on the relevance of glucose metabolism in astrocytes and in astrocytes associated with high-grade gliomas. In GBM patients, a correlation between patients' metabolic status, tumor's histologic phenotype, tumor's molecular changes, use of anti-diabetic drugs and the respective impact of these factor on survival warrants further investigation.

PT109, a novel multi-kinase inhibitor suppresses glioblastoma multiforme through cell reprogramming: Involvement of PTBP1/PKM1/2 pathway

Glioblastoma multiforme (GBM) is the most prevalent type and lethal form of primary malignant brain tumor, accounting for about 40-50% of intracranial tumors and without effective treatments now. Cell reprogramming is one of the emerging treatment approaches for GBM, which can reprogram glioblastomas into non-tumor cells to achieve therapeutic effects. However, anti-GBM drugs through reprogramming can only provide limited symptom relief, and cannot completely cure GBM. Here we showed that PT109, a novel multi-kinase inhibitor, suppressed GBM's proliferation, colony formation, migration and reprogramed GBM into oligodendrocytes. Analysis of quantitative proteomics data after PT109 administration of human GBM cells showed significant influence of energy metabolism, cell cycle, and immune system processes of GBM-associated protein. Metabolomics analysis showed that PT109 improved the aerobic respiration process in glioma cells. Meanwhile, we found that PT109 could significantly increase the ratio of Pyruvate kinase M1/2 (PKM1/2) by reducing the level of polypyrimidine tract-binding protein 1 (PTBP1). Altogether, this work developed a novel anti-GBM small molecule PT109, which reprogramed GBM into oligodendrocytes and changed the metabolic pattern of GBM through the PTBP1/PKM1/2 pathway, providing a new strategy for the development of anti-glioma drugs.

High Expression of Glycolytic Genes in Clinical Glioblastoma Patients Correlates With Lower Survival

Glioblastoma (GBM), the most aggressive brain tumor, is associated with a median survival at diagnosis of 16–20 months and limited treatment options. The key hallmark of GBM is altered tumor metabolism and marked increase in the rate of glycolysis. Aerobic glycolysis along with elevated glucose consumption and lactate production supports rapid cell proliferation and GBM growth. In this study, we examined the gene expression profile of metabolic targets in GBM samples from patients with lower grade glioma (LGG) and GBM. We found that gene expression of glycolytic enzymes is up-regulated in GBM samples and significantly associated with an elevated risk for developing GBM. Our findings of clinical outcomes showed that GBM patients with high expression of HK2 and PKM2 in the glycolysis related genes and low expression of genes involved in mitochondrial metabolism-SDHB and COX5A related to tricarboxylic acid (TCA) cycle and oxidative phosphorylation (OXPHOS), respectively, was associated with poor patient overall survival. Surprisingly, expression levels of genes involved in mitochondrial oxidative metabolism are markedly increased in GBM compared to LGG but was lower compared to normal brain. The fact that in GBM the expression levels of TCA cycle and OXPHOS-related genes are higher than those in LGG patients suggests the metabolic shift in GBM cells when progressing from LGG to GBM. These results are an important step forward in our understanding of the role of metabolic reprogramming in glioma as drivers of the tumor and could be potential prognostic targets in GBM therapies.

Redifferentiation therapeutic strategies in cancer

The widely recognized problems of pharmacological strategies based on killing cancer cells demand a rethink of therapeutic approaches. Tumor reversion strategies that aim to shift cancer cells to a healthy differentiated state are a promising alternative. Although many studies have firmly demonstrated the possibility of reverting cancer to a normal differentiated state, we are still unable (with the exception of retinoic acid in a form of leukemia) to revert cancer cells to a stable differentiated healthy state. Here, we review the main biological bases of redifferentiation strategies and provide a description of the most promising research avenues.