SMAD1 and neoplasm: The ACVR1 protein can bind to Activin A, BMP2, BMP5, BMP6, BMP7, or BMP9 but not the other BMPs, and trigger SMAD1/5/8 signaling.[18] Our data indicate that BMP‐ACVR1 signaling is not only required for the anti‐tumor efficacy of PRC2 inhibitor, but also repressed by PRC2 and upregulated upon PRC2 inhibition (Figure 1H).