MicroRNA-206 promotes the recruitment of CD8⁺ T cells by driving M1 polarisation of Kupffer cells

Objective Kupffer cells (KCs) protect against hepatocellular carcinoma (HCC) by communicating with other immune cells. However, the underlying mechanism(s) of this process is incompletely understood. Design FVB/NJ mice were hydrodynamically injected with AKT/Ras and Sleeping Beauty transposon to induce HCC. Mini-circle and Sleeping Beauty were used to overexpress microRNA-206 in KCs of mice. Flow cytometry and immunostaining were used to evaluate the change in the immune system. Results Hydrodynamic injection of AKT/Ras into mice drove M2 polarisation of KCs and depletion of cytotoxic T cells (CTLs) and promoted HCC development. M1-to-M2 transition of KCs impaired microRNA-206 biogenesis. By targeting Klf4 (kruppel like factor 4) and, thereby, enhancing the production of M1 markers including C-C motif chemokine ligand 2 (CCL2), microRNA-206 promoted M1 polarisation of macrophages. Indeed, microRNA-206-mediated increase of CCL2 facilitated hepatic recruitment of CTLs via CCR2. Disrupting each component of the KLF4/CCL2/CCR2 axis impaired the ability of microRNA-206 to drive M1 polarisation of macrophages and recruit CTLs. In AKT/Ras mice, KC-specific expression of microRNA-206 drove M1 polarisation of KCs and hepatic recruitment of CTLs and fully prevented HCC, while 100% of control mice died from HCC. Disrupting the interaction between microRNA-206 and Klf4 in KCs and depletion of CD8⁺ T cells impaired the ability of miR-206 to prevent HCC. Conclusions M2 polarisation of KCs is a major contributor of HCC in AKT/Ras mice. MicroRNA-206, by driving M1 polarisation of KCs, promoted the recruitment of CD8⁺ T cells and prevented HCC, suggesting its potential use as an immunotherapeutic approach.