MTT reduction assay of wild-type (A; n = 5), TSC2-null (B; n = 5) MEFs and control (C; n = 7) and LAM (D; n = 8) cells in the presence or absence of doxycycline. *Significant difference from FBS, P≤ 0.05 one-way repeated measures anova. FBS, fetal bovine serum; LAM, lymphangioleiomyomatosis; MEF, mouse embryonic fibroblast; MTT, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium; TSC, tuberous sclerosis complex.