Abstract: Objective To investigate the expression of cytoskeleton⁃associated protein 4 (CKAP4) in clear cell renal cell carcinoma (ccRCC) and its clinical significance. Methods A total of 237 tumor tissues and paracancerous tissues were collected from ccRCC patients. The expression level of CKAP4 protein was detected by immunohistochemistry. The clinicopathological characteristics of ccRCC patients with different CKAP4 protein expression levels were compared by χ² test. The Kaplan⁃Meier method and Log⁃rank test were used to analyze the differences in the overall survival (OS) and progression⁃free survival (PFS) of patients with different CKAP4 protein expression levels. Cox proportional hazard regression was performed to analyze the influencing factors of OS and PFS in the patients with ccRCC. Results The high expression rate of CKAP4 protein in ccRCC tissues was significantly higher than that in paracancerous tissues (54.0% vs 23.6%, χ²=46.050, P<0.001). CKAP4 protein was highly expressed in the cancer tissues of ccRCC patients with higher Fuhrman grade, deeper tumor invasion, lymph node metastasis, distant metastasis and higher TNM stage (all P<0.05). The ccRCC patients with high expression of CKAP4 protein had significantly lower OS rate (χ²=6.394, P=0.011) and PFS rate (χ²=10.065, P=0.002) than those with low CKAP4 protein expression. High expression of CKAP4 protein was an independent risk factor for postoperative OS (HR=2.884, 95%CI:1.425-4.765, P<0.001) and PFS (HR=3.512, 95%CI: 1.987-5.326, P<0.001) in the patients with ccRCC. Conclusions CKAP4 protein is highly expressed in ccRCC tissues, and is an independent risk factor for poor prognosis in the patients with ccRCC.

Key words: Clear cell renal cell carcinoma, Cytoskeleton-associated protein 4, Clinicopathological characteristics, Prognosis