Germline GPR161 mutations predispose to pediatric medulloblastoma

PURPOSE The identification of a heritable tumor predisposition often leads to changes in management and increased surveillance of individuals who are at risk; however, for many rare entities, our knowledge of heritable predisposition is incomplete. METHODS Families with childhood medulloblastoma, one of the most prevalent childhood malignant brain tumors, were investigated to identify predisposing germline mutations. Initial findings were extended to genomes and epigenomes of 1,044 medulloblastoma cases from international multicenter cohorts, including retrospective and prospective clinical studies and patient series. RESULTS We identified heterozygous germline mutations in the G protein-coupled receptor 161 (GPR161) gene in six patients with infant-onset medulloblastoma (median age, 1.5 years). GPR161 mutations were exclusively associated with the sonic hedgehog medulloblastoma (MB_SHH) subgroup and accounted for 5% of infant MB_SHH cases in our cohorts. Molecular tumor profiling revealed a loss of heterozygosity at GPR161 in all affected MB_SHH tumors, atypical somatic copy number landscapes, and no additional somatic driver events. Analysis of 226 MB_SHH tumors revealed somatic copy-neutral loss of heterozygosity of chromosome 1q as the hallmark characteristic of GPR161 deficiency and the primary mechanism for biallelic inactivation of GPR161 in affected MB_SHH tumors. CONCLUSION Here, we describe a novel brain tumor predisposition syndrome that is caused by germline GPR161 mutations and characterized by MB_SHH in infants. Additional studies are needed to identify a potential broader tumor spectrum associated with germline GPR161 mutations.