LAUSR

BACKGROUND & AIMS Hepatocellular carcinoma (HCC) is characterized by intratumoral accumulation of regulatory T-cells (Tregs), which suppresses antitumor immunity. This study was designed to investigate how microRNAs regulate immunosuppression in HCC. METHODS FVB/NJ mice were hydrodynamically injected with AKT/Ras or c-Myc and Sleeping Beauty transposon to induce HCC. The Sleeping Beauty system was used to deliver microRNA-15a/16-1 into livers of mice. Flow cytometry and immunostaining were used to determine changes in the immune system. RESULTS Hydrodynamic injection (HDI) of AKT/Ras or c-Myc into mice resulted in hepatic enrichment of Tregs, reduced cytotoxic T cells (CTLs) and HCC development. HCC impaired microRNA-15a/16-1 biogenesis in Kupffer cells (KCs) of AKT/Ras and c-Myc mice. HDI of microRNA-15a/16-1 fully prevented HCC in AKT/Ras and c-Myc mice, while 100% of control mice died from HCC. Therapeutically, microRNA-15a/16-1 promoted a regression of HCC in both mouse models. MicroRNA-15a/16-1 impaired hepatic enrichment of Tregs and increased hepatic CTLs. Mechanistically, a significant increase was observed in serum C-C motif chemokine 22 (CCL22) and transcription of Ccl22 in KCs of AKT/Ras and c-Myc mice. MicroRNA-15a/16-1 prevented KCs from overproducing CCL22 by inhibiting NF-κB that activates transcription of Ccl22. By reducing CCL22 binding to CCR4 on Tregs, microRNA-15a/16-1 impaired Treg chemotaxis. Disrupting the interaction between microRNA-15a/16-1 and NF-κB impaired the ability of microRNA-15a/16-1 to prevent hepatic Treg accumulation and HCC. Depletion of CD8+ T cells and additional treatment of CCL22 recovered growth of HCC that was fully prevented by miR-15a/16. CONCLUSION MicroRNA-15a/16-1 attenuates immunosuppression by disrupting CCL22-mediated communication between KCs and Tregs. MicroRNA-15a/16-1 represents a potential immunotherapy against HCC.