Fig. 2: SYK signals through the MAPK/ERK1/2 pathway to block differentiation of leukemic cells.

A KG1 and MOLM14 cells transduced with an empty vector or a vector containing constitutively active form of MEK1 kinase (MEK-DD) were treated with R406 (KG1: 4 µM, MOLM14: 0.075 µM) for 24 h; thereafter, the phosphorylation status of ERK1/2 was assessed by immunoblotting. B Transfected cells were incubated for 3 days with R406 (KG1 0.4 µM, MOLM14 0.075 µM), and NBT reduction was assessed. The graph shows a relative change in absorbance at 620 nm. The experiment was repeated twice. Bars indicate mean + /− SD from biological replicates (n = 2) of a representative experiment. **P < 0.01. C May–Grunwald–Giemsa staining of KG1 cells containing either MEK-DD or empty vector after 5 days of treatment with R406 or PMA at the indicated concentration. Differentiated cells are morphologically characterized by nuclear condensation, increased cytoplasm/nucleus ratio, increased cell volume, and increased number of cytoplasmic granules. D KG1 cells containing either MEK-DD or empty vector were treated with R406 (0.4 µM) for 3 days. Thereafter, CD14 level was assessed by flow cytometry.