Targeting MMP9 in CTNNB1 mutant hepatocellular carcinoma restores CD8⁺ T cell-mediated antitumour immunity and improves anti-PD-1 efficacy.

Abstract

The gain of function (GOF) CTNNB1 mutations (CTNNB1 <i>^GOF</i> ) in hepatocellular carcinoma (HCC) cause significant immune escape and resistance to anti-PD-1. Here, we aimed to investigate the mechanism of CTNNB1 <i>^GOF</i> HCC-mediated immune escape and raise a new therapeutic strategy to enhance anti-PD-1 efficacy in HCC. RNA sequencing was performed to identify the key downstream genes of CTNNB1 <i>^GOF</i> associated with immune escape. An in vitro coculture system, murine subcutaneous or orthotopic models, spontaneously tumourigenic models in conditional gene-knock-out mice and flow cytometry were used to explore the biological function of matrix metallopeptidase 9 (MMP9) in tumour progression and immune escape. Single-cell RNA sequencing and proteomics were used to gain insight into the underlying mechanisms of MMP9. MMP9 was significantly upregulated in CTNNB1 <i>^GOF</i> HCC. MMP9 suppressed infiltration and cytotoxicity of CD8⁺ T cells, which was critical for CTNNB1 <i>^GOF</i> to drive the suppressive tumour immune microenvironment (TIME) and anti-PD-1 resistance. Mechanistically, CTNNB1 <i>^GOF</i> downregulated sirtuin 2 (SIRT2), resulting in promotion of β-catenin/lysine demethylase 4D (KDM4D) complex formation that fostered the transcriptional activation of MMP9. The secretion of MMP9 from HCC mediated slingshot protein phosphatase 1 (SSH1) shedding from CD8⁺ T cells, leading to the inhibition of C-X-C motif chemokine receptor 3 (CXCR3)-mediated intracellular of G protein-coupled receptors signalling. Additionally, MMP9 blockade remodelled the TIME and potentiated the sensitivity of anti-PD-1 therapy in HCC. CTNNB1 <i>^GOF</i> induces a suppressive TIME by activating secretion of MMP9. Targeting MMP9 reshapes TIME and potentiates anti-PD-1 efficacy in CTNNB1 <i>^GOF</i> HCC.