Effects of GSK3β activation on the cytotoxicity and apoptosis induced by doxorubicin, in A549 cells. A, western blot assay for activation of caspase-3 and cleavage of the death substrate PARP in A549 cells transfected either with S9A-GSK3β (S9A) or with DN-GSK3β (DN), treated with 2 μM doxorubicin for the indicated time points. B, quantitative detection of apoptotic A549 cells induced by doxorubicin. A549 cells transfected with S9A and DN in the presence or absence of LMB were treated with 2 μM doxorubicin for the indicated times. Apoptotic cells were detected by flow cytometry. Data represents the mean percentage of annexin-V positive cells from three independent experiments; bars, ± SD. *p<0.01. C, A549 cells treated with different concentrations of doxorubicin and LiCl alone, or with a fixed amount (10 mM) of LiCl and different doses of doxorubicin as indicated, following 48 h incubation. Cell viability determined by WST assay. *p<0.01. D, time-course of apoptosis induced by doxorubicin in combination with LiCl in A549 cells. Cells were treated either with doxorubicin (2 μM) alone or with LiCl (10 mM) added in, for the indicated time. Apoptotic cells were detected by annexin-V staining. *p<0.05.