BIRC2 blockade facilitates immunotherapy of hepatocellular carcinoma

Abstract

The effectiveness of immunotherapy in hepatocellular carcinoma (HCC) is limited, however, the molecular mechanism remains unclear. In this study, we identified baculoviral IAP repeat-containing protein 2 (BIRC2) as a key regulator involved in immune evasion of HCC. Genome-wide CRISPR/Cas9 screening was conducted to identify tumor-intrinsic genes pivotal for immune escape. In vitro and in vivo models demonstrated the role of BIRC2 in protecting HCC cells from immune killing. Then the function and relevant signaling pathways of BIRC2 were explored. The therapeutic efficacy of BIRC2 inhibitor was examined in different in situ and xenograft HCC models. Elevated expression of BIRC2 correlated with adverse prognosis and resistance to immunotherapy in HCC patients. Mechanistically, BIRC2 interacted with and promoted the ubiquitination-dependent degradation of NFκB-inducing kinase (NIK), leading to the inactivation of the non-canonical NFκB signaling pathway. This resulted in the decrease of major histocompatibility complex class I (MHC-I) expression, thereby protecting HCC cells from T cell-mediated cytotoxicity. Silencing BIRC2 using shRNA or inhibiting it with small molecules increased the sensitivity of HCC cells to immune killing. Meanwhile, BIRC2 blockade improved the function of T cells both in vitro and in vivo. Targeting BIRC2 significantly inhibited tumor growth, and enhanced the efficacy of anti-programmed death protein 1 (PD-1) therapy. Our findings suggested that BIRC2 blockade facilitated immunotherapy of HCC by simultaneously sensitizing tumor cells to immune attack and boosting the anti-tumor immune response of T cells.