Figure 3: The phosphopeptides showing different levels under gefitinib treatment were categorized according to three trends.

The red arrow, green arrow and blue line represent up-regulation, down-regulation and no change, respectively. Under Trend 1, phosphopeptides showing 2-fold down-regulation in Rgef, R10μM and R20μM were selected. ERK1/2 sequence motifs (S-P) were enriched from 22 phosphopeptides in the Trend 1 group with a score of 9.94. Under Trend 2, phosphopeptides exhibiting a greater than 2-fold up-regulation of phosphorylation in Rgef, but no change in R10μM and R20μM, were selected. Two CK2 sequence motifs, (S-E-X-E) and (S-X-E), were enriched from 29 and 48 phosphopeptides in the Trend 2 group with scores of 30.56 and 16, respectively. The sequence motif (S-D) was matched with 24 phosphopeptides with a score of 16, but no putative kinases were matched. Under Trend 3, phosphopeptides displaying greater than 2-fold up-regulation in Rgef, R10μM and R20μM were selected. ERK1/2 sequence motifs (S-P) were enriched from 26 phosphopeptides in the Trend 3 group with a score of 11.04.