The peripheral mu opioid receptor antagonist, methylnaltrexone (MNTX), inhibits EGF-induced recruitment/activation of the linker protein, Grb-2, and the scaffolding protein, Gab-1, in human lung cancer cells.

<p><b>Panel A</b>: Human H358 non-small cell lung cancer (NSCLC) cells were either untreated (control) or treated with 100 nM MNTX (1 hour pre-incubation), 10 ng/ml EGF for 15 minutes, or 100 nM MNTX and 10 ng/ml EGF. Cell lysates were obtained and immunoprecipitated with anti-EGFR antibody. Immunoblots were performed on total cell lysates and immunoprecipitated material using anti-Grb-2 (a,c) and anti-EGFR (b,d) antibody. MNTX inhibits EGF-induced recruitment of Grb-2 to the EGFR. <b>Panel B</b>: Human H358 non-small cell lung cancer (NSCLC) cells were either untreated (control) or treated with 100 nM MNTX alone, 10 ng/ml EGF for 5, 15 or 30 minutes, or 100 nM MNTX and 10 ng/ml EGF for 5, 15, or 30 minutes. Cell lysates were obtained and immunoblotted using anti-pY⁶²⁷ Gab-1 (a), anti-pY³⁰⁷ Gab-1 (b) and anti-actin (c) antibodies. MNTX attenuates EGF-induced Gab-1 tyrosine phosphorylation.