The peripheral mu opioid receptor antagonist, methylnaltrexone (MNTX), inhibits EGF-induced phosphorylation of Src, PI3 kinase and STAT3 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 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-phospho-Src (pY⁴¹⁶) (a), anti-phospho-p85/p55 PI3 kinase (pY⁴⁵⁸/pY¹⁹⁹) (b,c), anti-phospho-STAT3 (pY⁷⁰⁵) (d) and anti-actin (e) antibodies. <b>Panel B</b>: Graphical quantitation of immunoreactivity of experiments performed described in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0091577#pone-0091577-g003" target="_blank">Figure 3-B</a> and Panel A with normalization to total specific protein and n = 3 independent experiments per condition. An asterisk (*) indicates a statistically significant difference (p<0.05) from control. The error bars = standard deviation.