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BACKGROUND Alterations in actin subunit expression have previously been observed in multiple cancers. In glioblastoma (GBM), the expression of ACTC1 has been associated with a more invasive phenotype and with shorter survival. We sought to explore the diversity of actin subunit expression across glioma subtypes and patient derived glioblastoma stem cells (GSCs). METHODS Bioinformatic analysis of multiple glioma databases was performed to profile actin subunit (ACTA1, ACTA2, ACTC1, ACTG1, ACTG2, and ACTB) mRNA levels. Expression levels were also evaluated in normal brain in comparison to liver and heart tissue. Western blot was used to analyze protein expression in GSCs, surgical tissue and human fetal astrocytes. RESULTS The primary actin subunits expressed in normal brain are beta actin (ACTB) and gamma actin (ACTG1). RNA sequencing of tissue from multiple glioma subtypes or different brain regions reveals a global increase in ACTG1 and ACTB abundance in gliomas compared to normal brain. LGG-GCIMP high and LGG-co-deleted glioma subtypes have the lowest ACTC1 expression. LGG-GCIMP low (HR 9.75, P< 0.001), LGG-mesenchymal-like (HR11.1, P< 0.001), LGG-classic-like (HR10.96, P< 0.001) subtypes are associated with ACTC1 expression. ACTC1, ACTCB, and ACTG protein expression was observed in GSCs, freshly resected GBM tissue, and human fetal astrocytes. CONCLUSIONS Gliomas have a specific pattern of actin subunit expression that differs in actin subunit type and abundance when compared to normal adult brain. Expression of ACTC1 is found in aggressive glioma subtypes and is shared by GSCs and human fetal astrocytes. Investigation into the neurodevelopmental role of ACTC1 and its contribution to oncogenic transformation in GBM is warranted.

BACKGROUND Elevated levels of D-2-hydroxyglutarate (D2HG) have been detected in several cancers, including IDH1/2 mutant gliomas, PHGDH-amplified breast cancer, diffuse large B-cell lymphomas which harbor loss-of-function mutations in D2HG dehydrogenase gene (D2HGDH), and MYC-amplified breast cancers. Given the high degree of conservation between the yeast and human isocitrate dehydrogenases the similarities between yeast and cancer glycolytic metabolism, we hypothesized that a yeast model would allow for the successful recapitulation of metabolic dysregulation by D2HG. METHODS A heteroallelic idp1 R148H yeast strain was created (equivalent to human IDH2 R172H). The growth characteristics of this strain and the dld3∆ strain (equivalent to D2HGDH loss of function) were evaluated with glucose or galactose carbon source. Octyl-D2HG, a cell permeable mimic of D2HG, was used to assess the effects of D2HG accumulation at varying concentration. FACS was used to measure cell viability, reactive oxygen species (ROS) production, and mitochondrial membrane potential. Analysis of the synthetic lethal genetic array for the dld3∆ strain was performed. RESULTS Accumulation of D2HG in mutant and wild-type yeast strains results in impaired growth and reduction in cell viability in a concentration dependent manner. The negative effect on growth and cell viability is more prominent when cells are not utilizing oxidative phosphorylation for energy production (glucose versus galactose carbon source). D-2HG accumulation results in ROS production in dld3∆ but not in the heteroallelicidp1 R148H yeast strain. An increase in mitochondrial membrane potential occurs in both strains when grown with galactose, but not in glucose. The top negative genetic interactors with dld3∆ include genes involved in mitochondrial function. CONCLUSIONS We found that yeast cells have different sensitivity to the toxic effects of D-2HG depending on the metabolic status of the cell. This suggests that altering cell metabolism may be a viable therapeutic target in cancers with excess production of D2HG such as IDH mutant gliomas.