The following article from Cancer Science, 'Blockage of intracellular proton extrusion with proton pump inhibitor induces apoptosis in gastric cancer' by Marie Yeo, Dong-Kyu Kim, Hee Jin Park, Sung Won Cho, Jae Youn Cheong and Kwang Jae Lee (doi: 10.1111/j.1349-7006.2007.00642.x), published online on 23 October 2007 on Blackwell Synergy (http://www.blackwell-synergy.com), has been retracted by agreement between the authors, the journal Editor in Chief, Takashi Tsuruo, and Blackwell Publishing. All authors wish to retract this paper because of the use of RGM-1 without the prior permission of the original establisher.