We used the L858R and L861Q EGFR mutants in this report. L858R is one of the two most common EGFR mutations detected in NSCLC ( 12). L861Q was identified by a mutagenesis screen in mice; this mutant EGFR exhibits increased
tyrosine kinase activity and steady-state lower protein levels compared with WT receptor ( 33). The location of both L861Q and L858R is juxtaposed with each other in the activation loop, which provides the platform for kinase substrate(s) and modulates the catalytic activity of kinase by promoting a conformational change ( 34). Furthermore, oncogenic mutations in other RTKs involve an amino acid residue to the L861 of EGFR ( 35, 36). We observed ligand-independent
phosphorylation of mutant EGFRs ( Fig. 1), suggesting that the mutants turn on survival
signal transduction pathways, such as AKT in a ligand-independent manner. However, the oncogenic signals generated by the EGFR mutants were not sufficient for sustained growth of 32D cells in the absence of serum with or without ...