Inhibition of Akt/PKB by a COX-2 inhibitor induces apoptosis in gastric cancer cells

Background/Aim: Inhibition of cyclooxygenase-2 has been proposed to be a potential mechanism for the chemoprevention of gastrointestinal tumors by nonsteroidal anti-inflammatory drugs. This study investigates the mechanisms by which the cyclooxygenase-2 inhibitor SC236 induces apoptosis of gastric cancer cell lines and its downstream signaling pathway. Methods: Two gastric cancer cell lines, AGS and MKN28, were treated with SC236 and assessed for cell growth and apoptosis. The involvement of mitogen-activated protein kinase and Akt kinase/protein kinase B (Akt/PKB) pathways and their downstream signalings were studied in the AGS cell line. Results: SC236 treatment induced apoptosis in gastric cancer cells and caused activation of p38 and stress-activated protein kinase/jun kinase, but down-regulated Akt/PKB. The specific p38 inhibitor SB203580 and the dominant-negative stress-activated protein kinase/jun kinase both failed, while the constitutively active form of Akt/PKB was able to block SC236-induced apoptosis. SC236-induced apoptosis was coupled with release of cytochrome c and activation of caspases. Conclusion: One of the pathways involved in SC-236-induced apoptosis in gastric cancer cells is through downregulation of Akt and then release of cytochrome c. Copyright (c) 2006 S. Karger AG, Basel.