PIK3CA and gastric cancer: To further investigate the functional cooperation of CBS and PI3K/AKT signaling in gastric cancer pathogenesis, we engineered AGS gastric cancer cells, which harbor CBS deficiency and PIK3CA mutations E545A and E453K resulting in AKT activation (Figure 6F), to express a doxycycline-inducible wild type CBS or an inactive CBSI278T mutant.