['Several studies have demonstrated that YWHAZ (14-3-3ζ), included in the 14-3-3 family of proteins, has been implicated in the initiation and progression of cancers. We tested whether YWHAZ acted as a cancer-promoting gene through its activation/overexpression in gastric cancer (GC).', 'We analysed 7 GC cell lines and 141 primary tumours, which were curatively resected in our hospital between 2001 and 2003.', 'Overexpression of the YWHAZ protein was frequently detected in GC cell lines (six out of seven lines, 85.7%) and primary tumour samples of GC (72 out of 141 cases, 51%), and significantly correlated with larger tumour size, venous and lymphatic invasion, deeper tumour depth, and higher pathological stage and recurrence rate. Patients with YWHAZ-overexpressing tumours had worse overall survival rates than those with non-expressing tumours in both intensity and proportion expression-dependent manner. YWHAZ positivity was independently associated with a worse outcome in multivariate analysis (P=0.0491, hazard ratio 2.3 (1.003-5.304)). Knockdown of YWHAZ expression using several specific siRNAs inhibited the proliferation, migration, and invasion of YWHAZ-overexpressing GC cells. Higher expression of the YWHAZ protein was significantly associated with the lower expression of miR-375 in primary GC tissues (P=0.0047).'] Does overexpression of YWHAZ relate to tumor cell proliferation and malignant outcome of gastric carcinoma?