Wnt activation as a therapeutic strategy in medulloblastoma

Medulloblastoma (MB), the most common malignant pediatric brain tumor, is defined by four molecular subgroups (Wnt, Shh, Group 3, Group 4) based on transcriptional and epigenetic profiles. Wnt MB accounts for 10% of cases with the majority harboring somatic CTNNB1 mutations and chromosomal alterations for monosomy 6. Clinically, Wnt MBs have the most favorable prognosis with a >95% 5-year survivorship. By contrast, non-Wnt MBs are characterized by metastatic disease, increased rates of recurrence, and intermediate-poor overall survivorship. Given that Wnt MBs represent the only subgroup in which metastasis is not indicative of a poor prognosis, it has been suggested that Wnt signaling may contribute to their remarkable response to therapy. Using primary patient-derived MB brain tumor-initiating cell (BTIC) lines, we have characterized intrinsic differences in the tumor-initiating capacity of Wnt and non-Wnt MBs. In this work, we aimed to discover if Wnt activation in non-Wnt MBs could serve as a rationale for therapy employing a novel substrate-competitive peptide Wnt agonist. Our preclinical work establishes activated Wnt signaling as an innovative treatment paradigm with high clinical utility in childhood MB and provides evidence for the context-specific tumor suppressive function of the Wnt/β-catenin pathway. We compared the transcriptome of MB BTIC lines generated from Wnt (BT853), Group 3 (SU_MB002), and Group 4 (ICB1299). Each sample had triplicates (A, B, C). Further, we compared the transcriptome of control (PBS) and Wnt-activating drug-treated (L807mts) samples for SU_MB002 and ICB1299. These were also prepared in triplicates (A, B, C). Lastly, we compared the transcriptome of SU_MB002 cells that were flow cytometrically sorted for expression of endogenous Wnt activity based on TCF reporter expression for GFP (TGP_POS) compared to those cells that were negative based on TCF reporter expression for GFP (TGP_NEG). These samples were also prepared and analyzed as triplicates (A, B, C).