ATP6AP2 and cancer: Moreover, at variance with GCTs, where ATP6AP1 and ATP6AP2 mutations were predominantly frameshift or nonsense, consistent with the mutational spectra of potential tumor suppressor genes, inactivating mutations targeting ATP6AP1 and ATP6AP2 were found to be vanishingly rare in common cancers from TCGA, with a prevalence of 0.03% and 0.05% of cases, respectively (Fig. 3b).