ACVR1 and lymphoma: Together, the removal of H3K27me3 marks through PRC2 inhibition or depletion results in the upregulation of ACVR1 and the activation of BMP‐ACVR1 signaling, reflected by the phosphorylation of SMAD1/5 and the common upregulation of ID2 or ID3 in EZH2‐mutant lymphoma cells.