Abstract 1140: Genes preserving stem cell state in group 3 medulloblastoma brain tumor initiating cells contribute to therapy evasion and relapse

Abstract Medulloblastoma (MB) is the most common malignant pediatric brain tumor. Of current molecular subgroups, Group 3 patients face the highest incidence of metastatic spread and overall patient survival of less than 50%. Current clinical trials for recurrent MB patients based on genomic profiles of primary, treatment-naïve tumors provide limited clinical benefit, since recurrent metastatic MBs are highly genetically divergent from their primary tumors. By adapting the existing COG (Children's Oncology Group) protocol for children with newly diagnosed high-risk MB to the treatment of immuno-deficient mice intracranially engrafted with human MB brain tumor initiating cells (BTICs), we have characterized the rare treatment-refractory cell population in Group 3 MBs. MB cell populations recovered separately from brains and spines during the course of tumor development and therapy were comprehensively profiled for gene expression analysis, stem cell and molecular features to generate a global, comparative profile of MB cells through therapy to relapse. One of the most intriguing observations from our gene expression data was consistent over-expression in the treatment-refractory cell population of proteins belonging to the Inhibitor of DNA-binding/differentiation (ID) family (transcription factors with a basic helix-loop-helix motif that act as suppressors cellular differentiation), and a longevity-associated protein known as bactericidal/permeability-increasing fold-containing-family-B-member-4 (BPIFB4). This persistent upregulation of genes preserving undifferentiated state and cellular longevity further strengthens the hypothesis of stem-cell like cells driving tumor relapse in MB. Targeting ID1 and BPIFB4 using both knockdown (KD) and knockout (KO) strategies has resulted in decreased self-renewal and tumorigenicity of both primary and recurrent MB cells, further highlighting their potential as novel therapeutic targets in MB. Our differential genomic and gene expression profiles of the “treatment-responsive” tumors against those that fail therapy have successfully contributed to discovery and characterization of novel therapeutic targets for the most aggressive subgroup of MB. Citation Format: Sheila Kumari Singh, David Bakhshinyan, Chitra Venugopal, Ashley Adile, Mohini Singh, Maleeha Qazi, Branavan Manoranjan, Michelle Kameda-Smith. Genes preserving stem cell state in group 3 medulloblastoma brain tumor initiating cells contribute to therapy evasion and relapse [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1140.