Neuromedin B causes transactivation of Epidermal Growth Factor receptors in lung cancer cells

Abstract

The transactivation of Epidermal Growth Factor receptors (EGF-Rs) was investigated in lung cancer cells. Neuromedin B (NMB), which is an autocrine growth factor in some lung cancer cells (Moody et al., JPET 1992;163:), has structural homology with bombesin (BB) and gastrin releasing peptide (GRP). Also, some lung cancer cells have EGF-R overexpression and/or mutation. Here the ability of NMB to transactivate EGF-Rs was investigated by Western blot. Ten nM NMB or BA0, a universal agonist, but not BB or GRP caused phosphorylation of Tyr1068 of the EGF-R using NCI-H1299 cells. This signal was amplified using NCI-H1299 cells stably transfected with NMB-Rs. The transactivation of EGF-Rs or the phosphorylation of ERK caused by NMB was inhibited by AG1478, a tyrosine kinase inhibitor, as well as PD168368, a NMB-R antagonist, but not BW2258U89, a GRP-R antagonist. These results suggest that NMB causes ERK activation after phosphorylation of the EGF-Rs in lung cancer cells. Also, the transactivation of the EGFR caused by NMB addition to lung cancer cells was inhibited by GM6001, a matrix metalloprotease inhibitor. It remains to be determined if NMB causes release of EGF-R agonists from lung cancer cells, such as transforming growth factor alpha, resulting in tyrosine phosphorylation of EGF-Rs.