Hypoxia drives shared and distinct transcriptomic changes in two invasive glioma stem cell lines.

Glioblastoma (GBM) is the most common primary malignant cancer of the central nervous system. Insufficient oxygenation (hypoxia) has been linked to GBM invasion and aggression, leading to poor patient outcomes. Hypoxia induces gene expression for cellular adaptations. However, GBM is characterized by high intertumoral (molecular subtypes) and intratumoral heterogeneity (cell states), and it is not well understood to what extent hypoxia triggers patient-specific gene responses and cellular diversity in GBM. Here, we surveyed eight patient-derived GBM stem cell lines for invasion phenotypes in 3D culture, which identified two GBM lines showing increased invasiveness in response to hypoxia. RNA-seq analysis of the two patient GBM lines revealed a set of shared hypoxia response genes concerning glucose metabolism, angiogenesis, and autophagy, but also a large set of patient-specific hypoxia-induced genes featuring cell migration and anti-inflammation, highlighting intertumoral diversity of hypoxia responses in GBM. We further applied the Shared GBM Hypoxia gene signature to single cell RNA-seq datasets of glioma patients, which showed that hypoxic cells displayed a shift towards mesenchymal-like (MES) and astrocyte-like (AC) states. Interestingly, in response to hypoxia, tumor cells in IDH-mutant gliomas displayed a strong shift to the AC state, whereas tumor cells in IDH-wildtype gliomas mainly shifted to the MES state. This distinct hypoxia response of IDH-mutant gliomas may contribute to its more favorable prognosis. Our transcriptomic studies provide a basis for future approaches to better understand the diversity of hypoxic niches in gliomas.

Generation and Analysis of dsDNA Breaks for Checkpoint and Repair Studies in Fission Yeast.

Damage to DNA elicits both checkpoint and repair responses. These are complex events that involve many genes whose products assemble at lesions and form signaling cascades to recruit additional factors and regulate the cell cycle. The fission yeast Schizosaccharomyces pombe has proven to be an excellent model to study these events, and has led gene and pathway discovery efforts. Recent progress has involved a more detailed analysis of the earliest events at lesions, particularly double-stranded DNA breaks (DSBs). Here we describe several methods for the analysis of events at DSBs, both on the DNA and the recruitment of proteins to these lesions, using S. pombe as a model. However, each of these methods is easily applicable to any experimental system with minor modifications to the protocols.