Comparison of protein expression of EGFR family proteins and the down-stream molecules in erlotinib-resistant cell lines in the absence or presence of erlotinib.

<p>A, Western blot analysis showing the expression of pEGFR, EGFR, pHER2, HER2, pHER3, HER3, pc-Met, c-Met, PTEN, pAkt, Akt, pERK1/2, and ERK1/2 proteins, and α-tubulin as a loading control. B, Exponentially growing PC9 and PC9/ER1 cells were exposed to various doses of erlotinib for 5 hr, and followed by Western blot analysis. C, Exponentially growing 11–18, 11–18/ER1-7, and 11–18/ER2-1 cells were exposed to various doses of erlotinib for 5 hr, and followed by Western blot analysis.