Fig. 4

Phosphorylation of EGFR Y845 is not inhibited with Src inhibitors PP1 and Dasatinib. a EGFR Y845 levels show increased levels in response to cetuximab with time in resistant cells (left panel) and constant levels in sensitive cells (right panel). b Quantitation of EGFR Y845 normalized to GAPDH from four independent experiments after increasing times of exposure to10 μM of PP1. c phospho-Src Y416 show increased levels in response to cetuximab with time in resistant cells (left panel) and constant levels in sensitive cells (right panel). d Quantitation of p-Src Y416 normalized to GAPDH from four independent experiments after increasing times of exposure to cetuximab. e Representative western blot of EGFR Y845 show constant levels in response to PP1 in both resistant cells (left panel) and sensitive cells (right panel) in presence of cetuximab. f Representative western blot of p-Src 416 show reducing levels in response to PP1 in both resistant cells (left panel) and sensitive cells (right panel) with increasing time. g As in E above but after exposure to Dasatinib. h As in E above but after exposure to Dasatinib. i Proliferation of resistant and sensitive cell lines after exposure to PP1 for 72 h, measured using the CCK-8 assay