Fig. 4.

Cmpd1-mediated inhibition of pYStat3 is associated with Erk1/2^MAPK induction, which promotes pS727Stat3 and is reversed by the MEK inhibitor PD98059. Immunoblotting analysis of whole-cell lysate preparation from U251MG cells untreated (–) or treated with 15 µM Cmpd1 for 15 or 30 minutes following pretreatment with or without 50 µM PD98059 for the indicated times and probing for pYStat3, pS727Stat3, Stat3, pErk1/2^MAPK, Erk1/2^MAPK, and glyceraldehyde 3-phosphate dehydrogenase (GAPDH). The positions of the proteins in the gel are labeled. Bands corresponding to the phospho-protein levels in the gel were quantified by ImageQuant and calculated as a percentage of control (dimethyl sulfoxide) relative to the total proteins and GAPDH levels. Control lane (–) represents whole-cell lysates prepared from 0.025% dimethyl sulfoxide–treated cells. Data are representative of three independent determinations.