Musashi1 enhances chemotherapy resistance of pediatric glioblastoma cells in vitro.

Glioblastoma (GBM) is the most aggressive form of glioma in adults and children and is associated with very poor prognosis. Pediatric tumors are biologically distinct from adult GBM and differ in response to current GBM treatment protocols. Regarding pediatric GBM, new drug combinations and the molecular background of chemotherapy effects need to be investigated, in order to increase patient survival outcome. The expression of the RNA-binding protein Musashi1 (MSI1) in pediatric glioma samples of different WHO tumor grades was investigated on the protein (immunohistochemistry) and on the RNA level (publicly accessible RNA sequencing dataset). The impact of the chemotherapeutic temozolomide (TMZ) in combination with valproic acid (VPA) was tested in two pediatric glioblastoma-derived cell lines. The supportive effect of MSI1 expression against this treatment was investigated via transient knockdown and protein overexpression. MSI1 expression correlates with pediatric high-grade glioma (HGG). The combination of TMZ with VPA significantly increases the impact of drug treatment on cell viability in vitro. MSI1 was found to promote drug resistance to the combined treatment with TMZ and VPA. MSI1 expression is a potential marker for pediatric HGG and increases chemoresistance. Inhibition of MSI1 might lead to an improved patient outcome and therapy response.