Comparisons of lapatinib sensitivities and the baseline signalling proteins activities between parental and lapatinib-resistant subclones.

<p><b>A,</b> Lapatinib sensitivity curves in the parental OE19 and two lapatinib-resistant (LR) subclones. The calculated values of IC₅₀ of lapatinib were 200 nM in parental cells and >1,000 nM in two LR subclones. Values were presented as relative cellular viability relative to vehicle-treated controls with the mean ± S.E. of quadruplicate from a representative experiment. The <i>p</i> values were <0.0001 for OE19 <i>vs</i> LR2A and OE19 <i>vs</i> LR2B, and was 0.129 for LR2A <i>vs</i> LR2B. The <i>p</i> values were calculated by two-way ANOVA. <b>B,</b> Immunoblots showing the phosphorylations of distinct signalling molecules in parental OE19 cells and the <i>Src</i>-mutant lapatinib-resistant derivatives.