CX3CL1/CX3CR1-dependent regulatory macrophage infiltration promotes tumor recurrence after liver transplantation for intrahepatic cholangiocarcinoma

Abstract

Background: Regional immunoregulation in graft and tumor microenvironment may play a critical role in intrahepatic cholangiocarcinoma (iCCA) recurrence after liver transplantation (LT). Regulatory macrophages (Mregs) have promising potentials for the treatment of graft rejection due to the potent immunosuppressive function. However, Mregs in tumor microenvironment were reported to promote tumor growth and immunoevasion. Currently, the existence and role of Mregs in iCCA remain unknown. Here, we aim to investigate the role and mechanism of Mregs on iCCA recurrence after curative surgical treatment. Methods: Gene expression profile from our institute and TCGA were analyzed to find out possible interaction between iCCA and monocytes. The serum CX3CL1 concentration and peripheral CX3CR1+ monocytes were assessed in LT patients. A total of 75 patients with iCCA was included and prospectively followed-up since 2001. The clinical significance of CX3CL1 expression and Mregs was evaluated by Cox proportional hazards regression model. Results: 1. Higher serum CX3CL1 concentration and more peripheral CX3CR1+ monocytes were detected in post-transplantation patients (Fig.1). 2. Compared with non-cancerous tissue, CX3CL1 expression and CX3CR1+ Mreg infiltration were increased in iCCA tumor tissue both after LT and resection (Fig.2). The expression level of CX3CL1 was positively related to the number of CX3CR1+ Mregs in iCCA (Pearson correlation= 0.292, P< 0.05). The elevated level of tumoral CX3CL1 and higher number of CX3CR1+ Mregs in iCCA tissue were correlated with shorter disease-free survival (DFS) in iCCA patients after curative surgery (Fig.2); 3. In multivariate model, CX3CR1+ Mreg was identified as an independent prognostic factor for DFS (HR:3.400, 95%CI: 1.900-6.084, P< 0.001). 4. Elevated CX3CL1 facilitated recruitment and infiltration of Mregs (Fig.3). Conclusion: Enhanced CX3CL1/CX3CR1 interaction facilitated intragraft Mreg infiltration, which subsequently promoted iCCA recurrence after LT.