CDK12 is a potential therapeutic target for human gastric cancer. A. The expression of CDK12 was examined by immunohistochemistry (IHC) staining using a gastric tumor array. The upper panels show quantification of all samples and paired samples (n=58). The lower panels show expression of CDK12 in patients with different age, gender, clinical stages and tumor grades. The representative photographs of each group of paired samples are shown. 100 × magnification. B. The expression of CDK12 in human gastric cancer cell lines: HCG27, AGS, SNU-1, KATOIII, and NCI-N87 were evaluated by western blotting (WB). C. The level of CDK12 knock-down by lentiviral transduction (shMock, shCDK12#2 and shCDK12#5) was measured by western blotting in SNU-1 and KATOIII cell lines. D. Cell viability was measured after CDK12 knock-down by MTT (72 h after seeding cells) assay. E. Colony number was checked after CDK12 knocking down by anchorage-independent colony formation assay, representative photographs are shown. F. Protein levels were detected by WB after overexpression of CDK12 or control. G. Cell proliferation was measured by colony formation assay after overexpression of CDK12 or control, representative images are shown. Data represent means ±SD. P<0.05: *, p<0.01: **, p<0.001: ***. Significance determined by two-tailed Student's t test.