PPP1R15A and neoplasm: However, VEGF-A IHC showed that GADD34 mutation, either heterozygous or homozygous, had no significant effect on VEGF-A expression in medulloblastoma in Ptch1+/− mice (Figure 4G–4I, 4M), and CD31 IHC showed that GADD34 mutation, either heterozygous or homozygous, did not significantly affect angiogenesis in this tumor (Figure 4J–4L, 4N).