Fig. 6

Response of SKN-SH wild-type cells (W) to incubation with conditioned media (CM) from doxorubicin-resistant cells (R): Effect on Stat3 phosphorylation, cytotoxic response to doxorubicin, and susceptibility to doxorubicin-induced apoptosis. (A) Effect on Stat3 phosphorylation: W and R cells were incubated with conditioned media obtained from R and W cells, respectively, for 10 or 30 min. Phosphorylation of Stat3 was determined by Western blot using anti-phosphoStat3 antibody. (B) Effect on cell response to doxorubicin: W cells were preincubated for 48 hr with increasing volumes (0–100 µl) of conditioned media from R cells. The W cells were then incubated with varying concentrations of doxorubicin for 72 hr, and viable cells determined by the MTT assay. (C) Effect of conditioned media on doxorubicin-induced DNA degradation in W cells: W cells were incubated with conditioned media from W or R cells for 48 hr prior to an additional 24 hr of incubation with doxorubicin (1 µM). DNA was extracted and electro-phoresed on a 1% agarose gel.