Geneticists have discovered how a specific genetic mutation (H3K27M) causes a devastating, incurable childhood cancer, known as diffuse midline glioma (DMG), and — in lab studies working with model cell types — successfully reverse its effects to slow cancer cell growth with a targeted drug. Their landmark work translates crucial new understanding of the genetics of DMG progression into a highly promising, targeted therapeutic approach and offers significant hope of improved treatments in the future.