H2BC21 and neoplasm: To do so, we generated primary tumors by orthotopically injecting a mixture of 20% H2B-eGFP-labeled Her2-GEM model-derived Paqr8-OE cells and 80% H2B-mCherry-labeled vector control cells into nu/nu mice on doxycycline and then withdrew doxycycline to downregulate Her2 and induce tumor regression.