The clinicopathological significance and relapse predictive role of tumor microenvironment of intrahepatic cholangiocarcinoma after radical surgery

BACKGROUND: This study attempts to detect the expression of FoxP3, CD68, CD8α, and PD‐L1 in the tumor microenvironment (TME) of intrahepatic cholangiocarcinoma (ICC), and analyze the relationship between the corresponding cells and clinicopathological characteristics as well as prognosis of ICC. METHODS: RNA sequencing (RNA‐seq) provided the general landscape of the TME in ICC. A total of 99 ICC patients and the corresponding specimens were used for multiplex immunofluorescence and relapse‐free survival (RFS) was analyzed. Flow cytometry further validated the effect of regulatory T (Treg) cells on ICC relapse. RESULTS: RNA‐seq data showed that the infiltration of Treg cells, CD8+ T cells, and macrophages were likely associated with ICC relapse. The survival analysis based on multiplex immunofluorescence showed that the high FoxP3(+) Treg cells ratio and low CD68(+) macrophages ratio in mesenchyme were associated with higher RFS rate, respectively. Low FoxP3(+) Τreg cells ratio was associated with more perineural invasion, and high CD68(+) macrophages ratio was correlated with more lymph node metastasis. Cox regression analysis revealed that FoxP3(+) Treg cells ratio was an independent predictive factor for ICC relapse. Flow cytometry showed that TregIII was the predominant Treg cell subtype in both tumor tissue and peripheral blood of ICC patients, and high TregIII abundance in peripheral blood was significantly associated with longer RFS of ICC patients. CONCLUSION: High FoxP3(+) Treg cells ratio in the mesenchyme of ICC tumor tissue predicted longer RFS and was an independent favorable prognostic factor for ICC patients. Among all Treg cell subtypes, TregIII in peripheral blood was correlated with the RFS of ICC patients.