Myeloid and lymphoblastic disease phenotypes are reversible. (A) Six SCLtTA/BCR-ABL double-transgenic mice (▪) and 2 BCR-ABL single-transgenic mice (controls, □) were repeatedly induced (tetracycline removed from the drinking water) and reverted (tetracycline readministered). Shown is the absolute neutrophil count (ANC) in the peripheral blood over the course of 129 days after the first removal of tetracycline. (striped box) Presence or absence of tetracycline (Tet). Where no error bars are visible, SD was less than 1. (B) Reversibility of the lymphoblastic disease in an SCLtTA/BLCR-ABL double-transgenic mouse. This mouse had developed cervical lymphoma on day 28 of induction of BCR-ABL by tetracycline removal from the drinking water, and FACS analysis revealed that 38% of the cells in the peripheral blood were BP-1⁺B220^lo B-lymphoblastic tumor cells (left panel). Twelve days after tetracycline was readministered, there was no clinical evidence of lymphoma, and FACS analysis confirmed that the BP-1⁺B220^lo cells had disappeared from the peripheral blood (right panel).