Deletion of Cdc42 or Rac1 increases apoptosis mediated by Bid upregulation. (A) Representative western blots of immortalized NPM-ALK lymphoma cell lines obtained from mice with the indicated genotypes. Cells were transduced by retroviruses expressing an inducible CreER^T2 recombinase system and selected using 25 μg/mL blasticidin for 6 days. Cre recombinase was shortly activated by treatment with 10 nM 4-hydroxytamoxifen (4-OHT) for 4 hours to induce deletion of the floxed genes. Cells were collected 24, 48, and 72 hours after 4-OHT induction, lysed, and blotted with the indicated antibodies. Data are from 1 representative cell line for each genotype out of 3 NPM-ALK, 5 NPM-ALK;CreER^T2;Cdc42^fl/fl, 4 NPM-ALK;CreER^T2;Rac1^fl/fl, and 3 NPM-ALK;CreER^T2;Cdc42^fl/fl;Rac1^fl/fl cell lines transduced with CreER^T2 recombinase. (B) NPM-ALK lymphoma cell lines obtained from mice with the genotypes as in panel A and expressing CreER^T2 were conditionally deleted of the indicated floxed genes by treatment with 10 nM 4-OHT for 4 hours as described above. Cell growth/viability were measured by CellTiter-Glo at the indicated time points. Data are presented as mean ± SD of triplicate experiments, each performed with 3 independent cell lines for each genotype. (C) Percentages of apoptotic cells measured by TMRM staining at the indicated time points in NPM-ALK immortalized lymphoma cells from mice with the indicated genotypes after CreER^T2 induction of the floxed genes as described above. Data are indicated as means ± SD of triplicate experiments, each performed with 3 independent cell lines for each genotype. ***P < .001.