SOX12 is a novel stemness marker in gastric cancer progression. A, IHC staining showed that Yap1−/−Taz−/− mice exhibited low SOX12 expression in the MNNG (N-methyl-N’-nitro-N-nitrosoguanidine)-induced gastric cancer model. B and C, Highly expressed SOX12 gastric cancer cases were associated with unfavorable outcomes compared with the low-expression group. D–H, SOX12 depletion by siRNA inhibited cell proliferation, colony formation, cell metastasis abilities, and tumorsphere formation. I and J, Flow cytometry and Western blot analysis confirmed that SOX12 knockdown induced cell apoptosis. K, SOX12 overexpression in MKN7 cells increased the expression levels of canonical stemness markers. L, Heatmap displays multiple stemness markers that were upregulated in SOX12 high expression cases (from TCGA dataset). *, P < 0.05; **, P < 0.01; ***, P < 0.001.