MtFt expression inhibited tumor growth. (Ai) Weights of H1299 cell– and B9 cell–derived tumors (9 weeks after injection) and (ii) measurement of tumor burden growth over time. (B) MtFt and TfR expression (Western blotting) was repressed by oral administration of Dox to the mice (B9-Dox) (“Materials and methods”). (C) Weights of tumors (10 weeks after transplantation) obtained from mice that had (B9-Dox) or did not have (B9) doxycycline in their drinking water (*P < .1).