Tumor-associated macrophages (TAMs) are pivotal drivers of hepatocellular carcinoma (HCC) progression, and blocking TAM M2 polarization has the potential to dampen tumor microenvironment remodeling. In this study, we screened a series of phenylethanoid and phenylpropanoid glycosides and identified syringin as a natural compound capable of inhibiting M2 polarization while promoting M1 polarization in macrophages. Single-cell RNA sequencing confirmed that syringin reduced TAM M2 polarization and significantly impaired tumor microenvironment remodeling. In detail, syringin indirectly reduced the stability of MYC proto-oncogene protein (MYC), which is required for driving a broad set of targets, including Arg1 , Il10 , Ym1 , Mrc1 , and Cd274 . Using affinity-based protein profiling (ABPP), we revealed dihydrolipoamide S -acetyltransferase (DLAT) as a direct target of syringin. DLAT possesses protein acetyltransferase activity that acetylates MYC at K148. Syringin bound DLAT at residues R430 and N576 and disrupted the DLAT/MYC axis, thereby blocking MYC acetylation and promoting the ubiquitination and degradation of MYC protein. Additionally, syringin enhanced the efficacy of programmed cell death protein 1 blockade in mouse and patient-derived xenograft models, offering a potential adjunctive agent for HCC. Syringin targets DLAT to inhibit TAM M2 polarization and MYC stability, thereby restraining HCC progression and enhancing PD-1/PD-L1 immunotherapy.
Xiao et al. (Sun,) studied this question.