Characterization of Chromosomal Instability in Glioblastoma

Abstract

Glioblastoma multiforme (GBM) is a malignant tumor of the central nervous system (CNS). The poor prognosis of GBM due to resistance to therapy has been associated with high chromosomal instability (CIN). Replication stress is a major cause of CIN that manifests as chromosome rearrangements, fragility, and breaks, including those cytologically expressed within specific chromosome regions named common fragile sites (CFSs). In this work, we characterized the expression of human CFSs in the glioblastoma U-251 MG cell line upon treatment with the inhibitor of DNA polymerase alpha aphidicolin (APH). We observed 52 gaps/breaks located within previously characterized CFSs. We found 17 to be CFSs in GBM cells upon treatment with APH, showing a frequency equal to at least 1% of the total gaps/breaks. We report that two CFSs localized to regions FRA2E (2p13/p12) and FRA2F (2q22) were only found in U-251 MG cells, but not lymphocytes or fibroblasts, after APH treatment. Notably, these glioblastoma-specific CFSs had a relatively high expression compared to the other CFSs with breakage frequency between ∼7 and 9%. Presence of long genes, incomplete replication, and delayed DNA synthesis during mitosis (MiDAS) after APH treatment suggest that an impaired replication process may contribute to this loci-specific fragility in U-251 MG cells. Altogether, our work offers a characterization of common fragile site expression in glioblastoma U-251 MG cells that may be further exploited for cytogenetic and clinical studies to advance our understanding of this incurable cancer.

Visualization of the three-dimensional structure of the human centromere in mitotic chromosomes by superresolution microscopy

“…In our previous study, we applied Cen-CO-FISH to reveal a mechanism dependent on CENP-A and its associated proteins to prevent centromere recombination in human cells, which also increases in replicative senescence and in cancer cells (Giunta and Funabiki, 2017). CENP-A contributes to centromere DNA stability (Black and Giunta, 2018) and to preventing mutagenic R-loop-induced DNA damage and chromosome rearrangements (Balzano et al, 2021;Giunta, Hervé, et al, 2021). We also found that CENP-A depletion causes an apparent increase in the chromatin volume occupied by α-satellites along with altered sphericity of centromeres (Giunta and Funabiki, 2017).…”

Replication stress causes delayed mitotic entry and chromosome 12 fragility at the ANKS1B large neuronal gene in human induced pluripotent stem cells

“…The nature of breaks and gaps on mitotic chromosomes remains enigmatic, as they can be presented by single-stranded DNA, double-strand DNA breaks or decondensed chromatin. Therefore, cytogenetic analysis remains relevant for studying cFS (Miron et al, 2015;Balzano et al, 2022).…”