Abstract
Neurotensin is a 13 amino acid peptide which is present in many lung cancer cell lines. Neurotensin binds with high affinity to the neurotensin receptor 1, and functions as an autocrine growth factor in lung cancer cells. Neurotensin increases tyrosine phosphorylation of the epidermal growth factor receptor (EGFR) and the neurotensin receptor 1 antagonist SR48692 blocks the transactivation of the EGFR. Here the effects of reactive oxygen species on the transactivation of the EGFR and HER2 were investigated. Using non-small cell lung cancer (NSCLC) cell lines, neurotensin receptor 1 mRNA and protein were present. Using NCI-H838 cells, neurotensin or neurotensin8-13 but not neurotensin1-8 increased EGFR, ERK and HER2 tyrosine phosphorylation which was blocked by SR48692. Neurotensin addition to NCI-H838 cells increased significantly reactive oxygen species which was inhibited by SR48692, Tiron (superoxide scavenger) and diphenylene iodonium (DPI inhibits the ability of NADPH oxidase and dual oxidase enzymes to produce reactive oxygen species). Tiron or DPI impaired the ability of neurotensin to increase EGFR, ERK and HER2 tyrosine phosphorylation. Neurotensin stimulated NSCLC cellular proliferation whereas the growth was inhibited by SR48692, DPI or lapatinib (lapatinib is tyrosine kinase inhibitor of the EGFR and HER2). Lapatinib inhibited the ability of the neurotensin receptor 1 to transactivate the EGFR and HER2. The results indicate that neurotensin receptor 1 regulates the transactivation of the EGFR and HER2 in a reactive oxygen species-dependent manner.