Identification of medulloblastoma molecular subgroups by gene expression profiling

Clinical heterogeneity of medulloblastoma is based on differences in the molecular landscape of the tumor, which include gene expression and DNA methylation profiles and mutational spectrum. WHO classification of CNS malignancies developed in 2016 implies segregation of medulloblastoma entity into 4 distinct molecular subgroups: WNT, SHH, group 3 and group 4. This division defines clinical presentation, response to therapy, risk of tumor recurrence and presents a basis for individualized and risk-adapted treatment conduction. Molecular genetic techniques for medulloblastoma subgrouping are based either on gene expression profiling or investigation of whole-genome DNA methylation. Method used in clinical practice should be reliable, fast, undemanding for preanalytic procedures and robust. For these reasons gene expression analysis by NanoString technology can be designated. In the current study we present the first Russian experience in the molecular classification of medulloblastoma based on gene expression profiling by Nanostring technique. The retrospective analysis of 65 pathologically verified medulloblastoma samples was performed. Among these cases WNT subgroup was revealed in 8, SHH – in 15, group 3 – in 16 and group 4 in 26 patients. The subgroup distribution as well as clinical significance of each tumor type corresponded to the literature data. Notable, that NanoString technology allowed achieving reliable data on gene expression from complicated material – formalin-fixed paraffin embedded tissue.