ABSTRACT
DNA double-strand breaks (DSBs) can efficiently kill cancer cells, but they can also produce unwanted chromosome rearrangements when DNA ends from different DSBs are erroneously joined. Movement of DSB-containing chromatin domains might facilitate these DSB interactions and promote the formation of chromosome rearrangements. Therefore, we analyzed the mobility of chromatin domains containing DSBs, marked by the fluorescently tagged DSB marker 53BP1, in living mammalian cells and compared it with the mobility of undamaged chromatin on a time-scale relevant for DSB repair. We found that chromatin domains containing DSBs are substantially more mobile than intact chromatin, and are capable of roaming a more than twofold larger area of the cell nucleus. Moreover, this increased DSB mobility, but not the mobility of undamaged chromatin, can be reduced by agents that affect higher-order chromatin organization.
Subject(s)
Cell Nucleus/metabolism , Chromatin/metabolism , DNA Breaks, Double-Stranded , DNA Repair/genetics , Cell Line, Tumor , Cell Nucleus/drug effects , Cell Nucleus/genetics , Cell Nucleus/radiation effects , Chromatin/drug effects , Chromatin/genetics , Chromatin/radiation effects , Chromosome Aberrations/drug effects , Chromosome Aberrations/radiation effects , DNA Breaks, Double-Stranded/drug effects , DNA Breaks, Double-Stranded/radiation effects , DNA Damage , Etoposide/pharmacology , Fluorescence , Gamma Rays , Humans , Intracellular Signaling Peptides and Proteins/genetics , Intracellular Signaling Peptides and Proteins/metabolism , Models, Molecular , Motion , Plasmids , Staining and Labeling , Time-Lapse Imaging , Transfection , Tumor Suppressor p53-Binding Protein 1ABSTRACT
Glioblastoma multiforme (GBM) is a devastating disease with high mortality and poor prognosis. Cancer stem cells (CSCs) have recently been defined as a fraction of tumor cells highly resistant to therapy and subsequently considered to be responsible for tumor recurrence. These cells have been characterized in GBM and suggested to reside in and be supported by the tumor microvascular niche. Here we evaluated the response of tumor microvascular endothelial cells (tMVECs) to radio- and chemotherapy, and analyzed how this affects their interaction with CSCs. Our data demonstrate that tMVECs exhibit extreme resistance to both therapies, with the main response to irradiation being senescence. Importantly, senescent tMVECs can be detected in human GBM samples as well as in mice upon irradiation. Even though permanently arrested, they are still viable and able to support CSC growth with the same efficacy as non-senescent tMVECs. Intriguingly, GBM CSCs themselves are capable of differentiating into cells with similar features as tMVECs that subsequently undergo senescence when exposed to radiation. This indicates that endothelial-like cells are therapy resistant and, more importantly, support expansion of GBM cells.