Objective:To detect the expressions of Krüppel-like factor 12 (KLF12)protein in the cancer tissue and serum of the patients with colorectal cancer,and to investigate their clinical values.Methods:A total of 120 colorectal cancer patients were selected as case group,and 100 normal cases were regarded as control group. The cancer tissue and adjacent mucosa tissue were collected.Immunohistochemical method was used to detect the expressions of KLF12,nm23,CyclinE1,matrix metalloproteinase-2 (MMP-2),and MMP-9 proteins,and the relationships among these proteins were evaluated.ELISA assay was applied to detect the serum KLF12 levels of the patients in case group before operation and 1 month after operation the levels of serum KLF12 of the subjects in control group.Results:The positive expression rates of KLF12,CyclinE1,MMP-2 and MMP-9 proteins in cancer tissue were higher than those in adjacent mucosa tissue (χ2 =66.155,52.795,64.515,52.632;P <0.001),while the positive expression rate of nm23 protein in cancer tissue was lower than that in adjacent mucosa tissue (χ2 =13.019,P <0.001).The Spearman analysis results showed that the expression of KLF12 protein was positively correlated with the expressions of MMP-2 and MMP-9 proteins (r=0.3963,P <0.001;r=0.3264,P <0.001);the expression of KLF12 was negatively correlated with the expression of nm23 protein (r = - 0.2273,P =0.013).The level of serum KLF12 of the patients in case group before operation was higher than that in control group.The cut-off value of ROC curve of serum KLF12 protein expression level was 3.795 μg·L-1 ,and the area under the ROC curve was 0.834.The sensitivity and specificity were 60.8% and 94.0%,respectively. After operation,the serum level of KLF12 protein in the patients in case group was decreased,which was still higher than that in control group (t=2.708,P =0.007).The expression level of KLF12 protein in cancer tissue was positively correlated with the level of serum KLF12 protein (r =0.4069,P <0.001).According to degree of lymph node metastasis,and the serum level of KLF12 protein in N3 group was the highest,and the lowest serum level of KLF12 protein was found in N0 group (F =21.731,P <0.001).Conclusion:KLF12 protein might be involved in the invasion and metastasis of colorectal cancer,and the detection of serum level of KLF12 protein could be valuable for the judgement of disease and prediction of lymph node metastasis of the patients.