Stem-05. Identification of Patient-derived Glioblastoma Stem Cell (gsc) Lines With the Alternative Lengthening of Telomeres Phenotype
Year: 2018
Type: conference-abstract
Abstract: Telomeres are terminal DNA elements found at chromosomal ends consisting of hexagonal repeats of (TTAGGG)n, which are essential for maintaining genomic stability. In glioblastoma, TERT promoter mutations occur in approximately 60–80% of cases, leading to increased telomerase activity and enabling replicative immortality. The remaining tumors, instead, activate a telomerase-independent alternative lengthening of telomeres (ALT) mechanism, driven by homologous recombination machinery. ALT+ gliomas are enriched in tumors harboring mutations in ATRX and IDH, and mutually exclusive with TERT promoter mutations. A novel quantitative PCR (qPCR) method that measures both telomere content (TC) and extra-chromosomal telomeric DNA C-Circles (CCs) was used to screen a panel of 24 human GSC cell lines for potential ALT lines. mRNA expression of TERT (which encodes the catalytic component of telomerase) was measured via whole transcriptome sequencing. ATRX protein expression was assessed by immunoblotting. We identified 2 ALT+ GSC cell lines: GSC-522 and GSC-818. These 2 cell lines have significantly elevated DNA CC content (p<0.001) and telomere content (p<0.001) relative to the other GSCs, consistent with the ALT phenotype. Furthermore, whole transcriptome sequencing identified mRNA expression of TERT to be negligible in these two cell lines relative to the others (p=0.0023), suggesting absence of telomerase activity. Both GSC-522 and GSC 8–18 were found to lack detectable full length ATRX protein upon immunoblot analysis, suggesting loss of function of this pathway. CONCLUSIONS: Identification of ALT+ GSCs will enable future explorations of the mechanisms and biology of the ALT phenotype in the context of glioma, and will also help define radiation sensitivity and resistance patterns in ALT vs. telomerase-positive gliomas. Furthermore, these cell lines will serve as pre-clinical models to test novel chemotherapeutic agents in an effort to improve outcomes in a subset of high-grade gliomas.
Source: Neuro-Oncology
Institution: The University of Texas MD Anderson Cancer Center
Language: English
Subfield: Physiology
Field: Medicine
Domain: Health Sciences
Open Access status: bronze
OpenAlex ID: W2899646177