Fig. 6

Cisplatin resistance was independent of AREG expression in 11 OSCC cell lines. a Neither exogenous EGF nor AREG affected cisplatin resistance in OSCC cell lines. Cells were grown in the presence (+) or absence (−) of human recombinant EGF (50 ng/ml), human recombinant AREG (100 ng/ml) for 24 h and then treated with (+) or without (−) 10 μM cisplatin (NS: not significant. p > 0.05, student’s t-test). b Cisplatin IC50 value did not correlate to AREG mRNA expression (left) or protein production (right) in 11 OSCC cell lines. The cisplatin IC50 value in sensitive (n = 4) or resistant (n = 7) OSCC cell lines were plotted against AREG mRNA expression (left) or 24 h AREG production (right). The cell lines were clustered into cisplatin sensitive (IC50 < 3.5 μM) or resistant (IC50 > 8.5 μM). Median indicated with horizontal lines (Wilcoxon rank-sum test)