In order to test the durability of the requirement for antigen, we harvested tumor cells that had arisen after the initial transplantation of MMTV-rtTA/TRE-MYC/BCRHEL cells into sHEL mice and introduced these into either wild-type or a second set of sHEL mice that were not treated with doxycycline. This evidence concerns the gene MYC and neoplasm.