Tracking interactions between TAMs and CAFs mediated by arginase-induced proline production during immune evasion of HCC

Synergistic changes between tumor-associated macrophages (TAMs) and tumor-associated fibroblasts (CAFs) aggravated immune evasion of hepatocellular carcinoma (HCC), however, the underlying molecular mechanisms remain elusive. Their continuous and dynamic interactions are subject to bioactive molecule changes. A real-time and in-situ monitoring method suitable for in vivo research of these processes would be indispensable but is scarce. In this study, a dual imaging strategy that tracing the TAMs and CAFs simultaneously was developed using a new arginase-specific probe and established CAFs-specific probe. The emerging roles of arginase in mediating CAFs activation in mice were explored. Results showed arginase up-regulation in TAMs, followed by proline increase. Subsequently, proline produced by TAMs initiated the activation of CAFs. Through the JAK-STAT signaling, CAFs up-regulated the PD-L1 and CTLA-4, ultimately promoting immune evasion of HCC. This study revealed a new mechanism by which TAMs and CAFs collaborate in immune evasion, providing new targets for HCC immunotherapy.