Hu et al. Journal of Experimental & Clinical Cancer Research 2010, 29:154 http://www.jeccr.com/content/29/1/154 Page 4 of 8 Figure 1 Immunofluorescence staining of GSK-3b in ALL cells. Bone marrow samples were obtained from children with ALL and from control patients. GSK-3b was probed with Dylight 549-labeled anti-rabbit secondary antibody (red fluorescence) and nuclei were counterstained with Hoechst 33342 (blue fluorescence). Nuclear accumulation of GSK-3b in ALL cells was detected, whereas only cytoplasmic expression of GSK- 3b was observed in control cells. Figure 2 Detection of GSK-3b and NF- B protein expression, after 48 h of treatment with GSK-3b inhibitors, by western blot assay. ALL cells were cultured in the presence of LiCl (10 mM) or SB216763 (10 μM) for 48 h. Cytosolic and nuclear fractions were prepared from the indicated samples. b-Actin and histone were used as markers for the purity of the cytosolic and nuclear fractions, respectively. GSK-3b inhibition led to depletion of GSK-3b nuclear pool in ALL cells, whereas nuclear levels of NF- B p65 remained unchanged. The data shown are representative of 3 independent experiments. 1: untreated ALL cells; 2: ALL cells treated with NaCl; 3: ALL cells treated with LiCl (10 mM); 4: ALL cells treated with DMSO; 5: ALL cells treated with SB216763(10 μM). cord blood stem cell activity [13]. However, consistent with the localization of GSK-3b in the nuclei of normal BMMC, we found that the number of apoptotic cells in normal BMMC was not significantly changed in the pre- sence or absence of GSK-3b inhibitors after 48 h of treatment (Figure 4; P > 0.05). The results obtained with GSK-3b inhibition in normal progenitors versus ALL cells provide evidence of a significant therapeutic selectivity. Pharmacologic inhibition of GSK-3b decreased NF- B- mediated expression of an antiapoptotic molecule in ALL cells Pharmacologic inhibition of GSK-3b induced apoptosis in ALL cells, so we further investigated whether inhibi- tion of GSK-3b affects NF- B-mediated expression of the antiapoptotic gene survivin in cells from 10 patients with ALL. We found that inhibition of GSK-3b resulted in decreased mRNA and protein expressions of NF- B