Miat and interacting protein Metadherin maintain a stem-like niche to promote medulloblastoma tumorigenesis and treatment resistance.

Long noncoding RNAs (lncRNAs) play essential roles in the development and progression of many cancers. However, the contributions of lncRNAs to medulloblastoma (MB) remain poorly understood. Here, we identify as an lncRNA enriched in the sonic hedgehog group of MB that is required for maintenance of a treatment-resistant stem-like phenotype in the disease. Loss of results in the differentiation of tumor-initiating, stem-like MB cells and enforces the differentiation of tumorigenic stem-like MB cells into a nontumorigenic state. expression in stem-like MB cells also facilitates treatment resistance by down-regulating p53 signaling and impairing radiation-induced cell death, which can be reversed by therapeutic inhibition of using antisense oligonucleotides. Mechanistically, the RNA binding protein Metadherin (Mtdh), previously linked to resistance to cytotoxic therapy in cancer, binds to in stem-like MB cells. Like the loss of , the loss of reduces tumorigenicity and increases sensitivity to radiation-induced death in stem-like MB cells. Moreover, Miat and Mtdh function to regulate the biogenesis of several microRNAs and facilitate tumorigenesis and treatment resistance. Taken together, these data reveal an essential role for the lncRNA in sustaining a treatment-resistant pool of tumorigenic stem-like MB cells.