Fig. 4. SETDB1 mediated FosB expression changes the cell proliferation rate. (A) A549 cells were transfected with pCDNA3-FosB plasmid in 60 mm diameter dishes, after which they were seeded at a density of 2,000 cells/well in 96-well plates. The MTT assay was performed after doxorubicin treatment. (B) A549 cells were transfected with siRNA, and were treated with doxorubicin after seeding in 96-well plates for the MTT assay. Cell proliferation rate decreased with siFosB, but increased marginally in the combinatory transfection of siSETDB1and siFosB. (*P ＜ 0.05) (C) A549 cells were treated with various kinase inhibitors, along with doxorubicin. Western blot showed that most kinase inhibitors regulated the increased FosB gene expression by doxorubicin. (D) ChIP assay was performed with three primer sets for FosB promoter region, in the absence or presence of doxorubicin treatment. SETDB1 binding was detected in the specific regions (−267 to −115). H3K9me3 occupancy was consistent in these regions.