Effect of mutant FKHRL1.

Expression of mutant FKHRL1 inhibits proliferation and IGF-I rescue of Dex-induced apoptosis. (A) Effect of expression of mutant FKHRL1 on proliferation of H929 cells. Cell clones expressing PFB vector (Control), PFB-FKHRL1-WT (WT), PFB-FKHRL1-Thr32Ala (Thr32Ala), PFB-FKHRL1-Ser253Ala (Ser253Ala), or PFB-FKHRL1-Ser315Ala (Ser315Ala) were cultured in serum-free media containing 100 ng/mL IGF-I for 48 hours. Proliferation was assessed by MTT assay. Results are presented as mean ± SE (n = 4). Data are representative of 3 separate experiments. *P < .01. Expression of the various constructs was confirmed by blotting with antibodies to the HA tag. (B) Effect of expression of mutant FKHRL1 on IGF-I rescue of Dex-induced apoptosis. H929 clones, indicated as above, were pretreated with 100 ng/mL IGF-I for 1 hour followed by incubation with 1 μM Dex for an additional 36 hours. Cells were stained with annexin V and propidium iodide. Apoptotic cells were enumerated by FACS analysis.