Combination of AG1478 and gemcitabine does not cause synergistic growth inhibition and does not prevent constitutive STAT3Tyr705phosphorylation of PDAC cells. A, Exponentially growing PDAC cells were exposed to indicated concentrations of EGFR inhibitor, AG1478, gemcitabine or both together. MTT assays were performed to measure growth inhibition after 96 h of treatment. Bars represent SD of eight replicates, and the experiments were repeated three times. (*) = significant growth inhibition (p < 0.001) starts from this dose level and remained significant at higher doses. B, Exponentially growing PDAC cells were exposed to indicated concentrations of AG1478, gemcitabine (10 ng/ml), or both together. The blots were probed for phosphorylated and total forms of EGFR and STAT3. As a loading control, human β-actin levels are shown.