To investigate whether these mechanisms are relevant in DIPG, we treated cell lines derived from DIPG patients that are either ACVR1+/+ (ICR‐B169) or ACVR1+/R206H (HSJD‐DIPG‐007) (Carvalho et al,2019; C. Jones, personal communication) with Activin A. ICR‐B169 cells did not detectably induce pSMAD1/5 in response to Activin A (Fig 3C). This evidence concerns the gene ACVR1 and diffuse intrinsic pontine glioma.