MDB-54. GENOMIC VARIANCE OF MATCHED PRIMARY AND RECURRENT HUMAN MEDULLOBLASTOMA

Abstract

Abstract BACKGROUND To investigate the difference between matched primary and recurrent human medulloblastoma across four molecular subgroups and to further expand the existing mutational spectrum in the recurrence or dissemination lesions. METHODS We analyzed the whole-exome sequencing (WES) data of 56 matched samples from 28 pairs with primary and recurrent/disseminated medulloblastoma. WES was performed using the Illumina HiSeq 2500 system, and the sequencing data were then subjected to variant detection, genome annotation, GO functional enrichment analysis, and GWAS. RESULTS All tumor samples were classified as four subgroups, including 4 cases of WNT-MB, 8 cases of SHH-MB, 20 cases of G3-MB and 24 cases of G4-MB. Conical and non-conical chromosomal variations were observed in each subgroup. Recurrent G3-MB cohort exhibited the loss of chr1p and chr22q and gain of the chr16p. The gain of chr2p, 2q, and 9p, as well as the loss of chr9q were found in the recurrent lesions of G4-MB. Recurrence of SHH-MB exhibited the loss of chr19q and chr4p, and loss of chr5p was found in the WNT-MB recurrences. CTNNB1, IDH1, and ARID1A were only observed in recurrent tumors of G3-MB; MYC was only observed in the recurrent tumors of G4-MB; IDH1 and TERT were only observed in recurrent tumors of the SHH-MB. Compared to primary medulloblastoma, recurrent tumor samples obtained a higher level of tumor mutation burden. The mutant gene profiles were mainly enriched in cell adhesion function. CONCLUSIONS When relapsing, medulloblastoma subgroup generally remains consistent, but exhibits the specific CNV, SNV and mutated gene profiles.