Differential expression of TIM-3 between primary and metastatic sites in renal cell carcinoma

BACKGROUND: Due to the significant heterogeneity of renal cell carcinoma (RCC), immune checkpoints may express differently between primary and metastatic tumor. We aimed to evaluate the differential expression of TIM-3 between the primary and metastatic sites of RCC. METHODS: Cases of RCC with metastases resected or biopsied at West China Hospital between January 2009 and November 2016 were included. Clinicopathological parameters were retrospectively extracted. SPPS 22.0, GraphPad Prism 6 and R statistical software were applied for data analysis. RESULTS: A total of 163 cases were included. Immunohistochemical results showed that the overall detection rate of TIM-3 was 56.4% (92/163). The detection rate of TIM-3 in the primary (53.0%, 44/83) was numerically higher than that of the metastasis (42.6%,79/174). Although the concordance rate of TIM-3 between the primary and metastasis was as high as 66.3% (55/83) in the paired cohort, a significant statistically difference of TIM-3 expression between the primary and metastasis was observed (χ2 = 4.664, p = 0.002), with a poor consistency (Kappa = 0.331, p = 0.002). Subsequent survival analysis suggested that TIM-3 expression either in the primary or metastatic tumor was associated with longer progression-free survival (PFS) (HR: 0.67, 95% CI 0.45–0.99, P = 0.02) and overall survival (OS) (HR: 0.52, 95% CI 0.33–0.82, P < 0.001). The expressions of TIM-3 in the primary, metastatic tumors and patients treated with targeted agents all played as favorable factors for PFS and OS. Further multivariate analysis showed that, in the whole cohort, TIM-3 expression in metastatic tumor increased the predicted accuracy (PA) of the whole model of PFS from 74.7 to 75.6% (P = 0.02). For OS, the PA of whole model was increased from 78.1 to 81.1% by adding TIM-3 expression in the metastasis (P = 0.005). The same trends were also observed in paired patients and patients treated with targeted agents. In conclusion, the expression difference between the primary and metastatic tumor of TIM-3 was significant. Biopsy or resection of the metastases may provide a more accurate biological information for clinician’s decision-making and the patient’s prognosis. What’s more, the role of TIM-3 in the RCC still remains controversy, further study are needed to verify the conclusion.