Maintenance of established TetIL-7R tumors no longer appears to require high IL-7Rα expression. (A) IL-7Rα expression was measured in F5 TetIL-7R primary tumor cells (left), and after adoptive transfer into Rag1^−/− mice (middle). Mean fluorescence intensity (MFI) of primary tumor cells collected from the thymus of a sick mouse continuously fed dox (tumor) were compared with the DP (CD4⁺CD8⁺) cells of an F5 control mouse (used as the negative control; left). Malignant cells collected from the thymus of the same mouse were transplanted into Rag1^−/− recipient mice that were fed with (On dox) or not fed (Off dox) dox-containing food for 4 weeks after transplantation (middle). MFI was compared after 4 weeks between On- and Off-dox groups. IL-7Rα MFI for each transplant-recipient animal (right). (B) Transplanted cells collected from the bone marrow of On- and Off-dox recipient mice 4 weeks after transplantation were compared for their immunophenotype. CD4 vs CD8 (top) and CD5 vs TCRαβ (bottom). Frequency of cells within the gate (left) for each transplant recipient. Results are representative of 3 independent experiments (each from a different primary tumor).