Stat3 activity is required for survival in SFM. (A) SRB12-p9, Neo and two representative independent S3WT (S3WT6, S3WT10) and S3DN clones (S3DN2, S3DN5) were cultured for the indicated times in 10% FCS-containing media or SFM and cell viability was determined by the MTT assay (see materials and methods). White and black bars indicate the mean absorbance at 540 nm for cells grown in SFM or 10% FCS-containing media, respectively. Error bars indicate SEM for triplicate cultures. Results shown are representative of >4 assays that included 2 independent S3WT and S3DN cell clones. (B) SRB12-p9, Neo, S3DN2 and S3WT6 cells were cultured for 5 days in 10% FCS-containing media or SFM (upper and lower rows, respectively). Results shown are representative of 3 independent S3DN and S3WT cell clones from 4 separate experiments. Cells were photographed on a phase contrast microscope (100×).