SUMOylated IL-33 in the nucleus stabilizes the transcription factor IRF1 in hepatocellular carcinoma cells to promote immune escape

Abstract

Interleukin-33 (IL-33) functions both as a secreted cytokine and as a nuclear factor, with pleiotropic roles in cancer and immunity. Here, we explored its role in hepatocellular carcinoma (HCC) and identified that a posttranslational modification altered its nuclear activity and promoted immune escape for HCC. IL-33 abundance was overall decreased but more frequently localized to the nucleus in patient HCC tissues than in normal liver tissues. In human and mouse HCC cells in culture and in vivo, IL-33 overexpression inhibited proliferation and repressed the abundance of programmed death ligand 1 (PD-L1) at the transcriptional level by promoting the ubiquitin-dependent degradation of interferon regulatory factor 1 (IRF1). However, this interaction was disrupted by SUMOylation of IL-33 at Lys 54 mediated by the E3 ligase RanBP2. IL-33 SUMOylation correlated with its nuclear localization in HCC cells and tumors. An increase in SUMOylated IL-33 in HCC cells in cocultures and in vivo stabilized IRF1 and increased PD-L1 abundance and chemokine IL-8 secretion, which prevented the activation of cytotoxic T cells and promoted the M2 polarization of macrophages, respectively. Mutating the SUMOylation site in IL-33 reversed these effects and suppressed tumor growth. These findings indicate that SUMOylation of nuclear IL-33 in HCC cells impairs antitumor immunity.

Unpacking the complexity of nuclear IL-33 (nIL-33): a crucial regulator of transcription and signal transduction

“…Importantly, these findings have opened up exciting possibilities for the development of novel therapeutic strategies that target the nIL-33 pathway for the treatment of various diseases. In our previous study (Wang et al 2023b), we found that SUMOylated nIL-33 promotes PDL1 expression in liver cancer cells. Thus, targeting nIL-33 with SUMOylation may serve as a therapeutic strategy.…”

“…Thus, we referred to this technology (Henning et al 2022) and attempted to construct a SENP2-targeting nIL-33 chimera (STACs) targeting SUMO enzymes. In short, using SUMO specific protease 2 (SENP2) as a recruiter to recruit nIL-33 from SUMOylation, thereby removing SUMO molecules that bind to nIL-33, stabilizing four potential sites for SUMOylation identified within the protein (Wang et al 2023b). These modifications have been shown to modulate the function of IL-33, with SUMOylation enhancing its activity in promoting the proliferation of T cells.…”

“…SUMOylation is a form of post‐translational modification in which small ubiquitin‐like modifier (SUMO) proteins are attached to target proteins (Singh et al 2022; Vertegaal 2022). Previous studies by the authors have suggested that nIL‐33 is subject to SUMOylation, with four potential sites for SUMOylation identified within the protein (Wang et al 2023b). These modifications have been shown to modulate the function of IL‐33, with SUMOylation enhancing its activity in promoting the proliferation of T cells.…”

Distinctive tumorigenic significance and innovative oncology targets of SUMOylation

“…Concretely, in HCC, SUMO1-mediated SUMOylation via the IKII 265-268 SIM site of pyruvate kinase M2 (PKM2) relocates PKM2 from the cytoplasm to the nucleus, leading to glycolytic reprogramming and cancer progression via EMT induction and signal transducer and activator of the transcription 3 (STAT3) signaling pathway 26 . Likewise, Ran-binding protein 2 (RanBP2)-mediated SUMOylation of interleukin-33 (IL-33) at K54 facilitates its nuclear shuttling, therefore resulting in immune evasion in HCC 27 . Furthermore, in prostate cancer, SUMOylation of tumor suppressor gene p53, which is mediated by the RanBP2/SUMO1/Ubc9 complex, facilitates its translocation from the nucleus to the cytoplasm, promoting malignancy progression 28 .…”

“…Specifically, SUMOylation of programmed cell death protein-1 ligand (PD-L1) by TRIM28, an E3 ubiquitin ligase and E3 SUMO ligase, stabilizes PD-L1 via hampering PD-L1 ubiquitination and enhancing PD-L1 SUMOylation, leading to the T cell inactivation and immune evasion in gastric cancer 74 . Additionally, E3 ligase RanBP2-induced SUMOylation of nuclear factor IL-33 at K54 prevents the degradation of transcription factor IRF1 which elevates the expression of PD-L1, a T cell immune checkpoint ligand, in HCC cells, ultimately leading to the inactivation of T cells and immune surveillance 27 .…”