LncRNA Miat and Metadhedrin maintain a treatment resistant stem-like niche of medulloblastoma cells

Medulloblastoma is a pediatric brain tumor arising from the cerebellum and brainstem that is curable with surgery and aggressive cytotoxic therapy including craniospinal irradiation and chemotherapy. Preclinical models indicate that a small pool of de-differentiated, stem cell-like medulloblastoma cells are resistant to cytotoxic treatment and contribute to medulloblastoma relapse after aggressive therapy. Here, we identify Miat as a Shh and Myc regulated long noncoding RNA (lncRNA) that is required for maintenance of a treatment-resistant medulloblastoma stem-like phenotype. Loss of Miat delays medulloblastoma formation in genetically defined mouse models of Shh medulloblastoma and enforces differentiation of tumorigenic stem-like medulloblastoma cells into a non-tumorigenic cell state. Miat facilitates treatment resistance in part by downregulating p53 signaling and impairing radiation induced cell death in stem-like MB cells, which can be reversed by therapeutic inhibition of Miat with antisense oligonucleotides. The RNA binding protein Metadhedrin (Mtdh), which is associated with resistance to cytotoxic therapy in numerous types of cancer, co-localizes with Miat in stem-like medulloblastoma cells. Further, loss of Mtdh activates p53 signaling and reduces tumorigenicity in stem-like medulloblastoma cells. Taken together, these data reveal a critical role for the lncRNA Miat in sustaining a treatment resistant pool of tumorigenic stem-like medulloblastoma cells.