Expression pattern of CDK12 protein in gastric cancer and its positive correlation with CD8+ cell density and CCL12 expression

Background: The aims of this study were to investigate the expression pattern of CDK12 protein in gastric cancer, and to analyze the correlations of CDK12 expression between CD8(+) cell density and CCL12 expression. Methods: Eighty-six paired tumor and non-tumor samples were collected from patients who underwent radical surgery and had pathological confirmed gastric adenocarcinoma. Immunohistochemistry was used to assess CDK12 expression and CD8(+) cell density. Expression of CDK12 and CCL21 mRNA was detected by quantitative reverse transcription-polymerase chain reaction. Results: CDK12 expression in gastric tumor tissues was significantly higher than it in paired non-tumor tissues (P<0.001). High expression of CDK12 was identified in 43 cases (50%), and it was significantly correlated with Lauren's classification (diffuse type) and number of metastatic lymph nodes (>= 15). High CDK12 protein level indicated a relative poorer overall survival than patients with CKD12 low expression, while it was not identified as an independent prognostic factor. Median number of CD8(+) cells in tumor tissues was 51 (range: 0-292). Number of CD8(+) cells was positively correlated with CDK12 expression score in tumor tissues (r=0.243, P=0.024). Positive correlation was also found between CDK12 and CCL21 mRNA expression (r=0.419, P=0.017). Conclusion: High CDK12 expression was detected in gastric cancer which was correlated with malignant phenotypes and worse outcome. Positive correlations of CD8(+) cell number and CCL21 mRNA expression with CDK12 level were identified.