TMOD-23. ESTABLISHMENT AND CHARACTERIZATION OF IDH1-MUTANT HYPERMUTATED GLIOMA CELL LINES

Abstract

Low-grade gliomas can undergo hypermutation (HM) and malignant progression after treatment with temozolomide (TMZ). We and others have demonstrated that TMZ-associated HM is characterized by predominant C>T/G>A nucleotide transitions and mutation of mismatch repair (MMR) and PI3K pathway genes. Well-characterized models of HM glioma are needed to better understand the biology of HM tumors. We established three IDH1-mutant HM glioma cell lines from two post-treatment surgical specimens, two from an ATRX- and P53-mutant HM astrocytoma (P137), and one from a TERT promoter-mutant, 1p/19q co-deleted HM oligodendroglioma (P278). P137 cultures were established in serum-free conditions on laminin (GNS) and in 10% serum (ML). HM status was determined by exome sequencing. P137 GNS and P137 ML have 4,722 and 2,946 mutations, respectively, and represent independent HM events compared to each other and both spatially distinct and adjacent samples of uncultured tissue. MMR genes MSH4, MSH5, and MSH6 and PI3K pathway gene AKT3 have C>T/G>A mutations in P137 ML. In P137 GNS, MSH4, MSH5, MSH6, MLH1, MTOR, RPTOR, PIK3CA, and PTEN have C>T/G>A mutations. Both P137 ATRX-mutant lines are positive for alternative lengthening of telomeres, as measured by c-circle assay. Phylogenetic analysis shows that an independent tumor sample of P137 shares 524 mutations with the cell lines and has 1,872 private mutations. An immediately spatially adjacent piece of tumor shares 1,081 mutations with the GNS culture, only 47 mutations with the ML culture, and has 2,865 private mutations. P278 was established in serum-free conditions, has 5,752 mutations, and shares 4,875 of these mutations with two independent pieces of the tumor, including C>T/G>A mutations in MLH1, MSH2, MTOR, RPTOR, and PIK3R1. All cell lines maintain an IDH1 R132H heterozygous mutation through months of in vitro growth, produce 2-hydroxyglutarate, and demonstrate anchorage-independent growth. These cell lines provide novel tools for modeling hypermutated oligodendroglioma and astrocytoma.