HDAC9 and neoplasm: To disentangle the effects of the loss of HDAC activity in pre-tumor cells from the loss in other compartments, Hdac1 or Hdac2 were deleted in T cells via Cd4Cre in NPM::ALK mice, resulting in NPM::ALK Hdac1KO and NPM::ALK Hdac2KO mice (Fig. 2A).