TNFSF9 and lymphoma: Transcription factors may provoke lymphoma progression by regulating lymphoma cell interaction with the tumor microenvironment.22,23 PU.1 is a key communicator between FL cells and microenvironmental DC through immune checkpoint interaction.24,25 We demonstrated a significant correlation of PU.1 with expression of PD-L1 and 4-1BBL on lymphoma cells.