TGFβ induces proHB-EGF shedding and EGFR transactivation through ADAM activation in gastric cancer cells

Background and aims Transforming growth factor-beta (TGF beta) is known to potently inhibit cell growth Loss of responsiveness to TGB beta inhibition on cell growth is a hallmark of many types of cancer, yet its mechanism is not fully understood. Membrane-anchored heparin-binding EGF-like growth factor (proHB-EGF) ectodomain is cleaved by a disintegrin and metalloproteinase (ADAM) members and is implicated in epidermal growth factor receptor (EGFR) transactivation Recently, nuclear translocation of the C-terminal fragment (CTF) of pro-HB-EGF was found to induce cell growth We investigated the association between TGF beta and HB-EGF signal transduction via ADAM activation Materials and methods The CCK-8 assay in two gastric cancer cell lines was used to determine the effect for cell growth by TGF beta. The effect of two ADAM inhibitors was also evaluated Induction of EGFR phosphorylation by TGF beta was analyzed and the effect of the ADAM inhibitors was also examined Nuclear translocation of HB-EGF-CTF by shedding through ADAM activated by TGF beta was also analyzed EGFR transactivation, HB-EGF-CTF nuclear translocation, and cell growth were examined under the condition of ADAM17 knockdown Result. TGF beta-induced EGFR phosphorylation of which ADAM inhibitors were able to inhibit TGF beta induced shedding of proHB-EGF allowing HB-EGF-CTF to translocate to the nucleus ADAM inhibitors blocked this nuclear translocation TGF beta enhanced gastric cancer cell growth and ADAM inhibitors suppressed this effect. EGFR phosphorylation, HB-EGF-CTF nuclear translocation, and cell growth were suppressed in ADAM17 knockdown cells Conclusion HB-EGF-CTF nuclear translocation and EGFR transactivation from proHB-EGF shedding mediated by ADAM17 activated by TGF beta might be an important pathway of gastric cancer cell proliferation by TGF beta. (C) 2010 Elsevier Inc. All rights reserved