ID1 and neoplasm: Western blot analysis of tumor lysates demonstrated similar results as those observed by IHC staining, with ACVR1 R206H, H3.1K27M; PDGF-A; p53 deficient mutant tumors having significantly higher protein levels of Id1, Hes1, and CD31 than other tumor types, with ACVR1 R206H contributing most to these higher levels (Fig. 5b–d).