Immune checkpoint inhibitors (ICI) transformed the treatment landscape of hepatocellular carcinoma (HCC). Unfortunately, patients with attenuated MHC-I expression remain refractory to ICIs, and druggable targets for upregulating MHC-I are limited. Here, we found that genetic or pharmacologic inhibition of fatty acid synthase (FASN) increased MHC-I levels in HCC cells, promoting antigen presentation and stimulating antigen-specific CD8+ T-cell cytotoxicity. Mechanistically, FASN inhibition reduced palmitoylation of MHC-I that led to its lysosomal degradation. The palmitoyltransferase DHHC3 directly bound MHC-I and negatively regulated MHC-I protein levels. In an orthotopic HCC mouse model, Fasn deficiency enhanced MHC-I levels and promoted cancer cell killing by tumor-infiltrating CD8+ T cells. Moreover, the combination of two different FASN inhibitors, orlistat and TVB-2640, with anti–PD-L1 antibody robustly suppressed tumor growth in vivo. Multiplex IHC of human HCC samples and bioinformatic analysis of The Cancer Genome Atlas data further illustrated that lower expression of FASN was correlated with a higher percentage of cytotoxic CD8+ T cells. The identification of FASN as a negative regulator of MHC-I provides the rationale for combining FASN inhibitors and immunotherapy for treating HCC. Significance: Inhibition of FASN increases MHC-I protein levels by suppressing its palmitoylation and lysosomal degradation, which stimulates immune activity against hepatocellular carcinoma and enhances the efficacy of immune checkpoint inhibition.

Background and Aims: Deregulation of adenosine-to-inosine editing by adenosine deaminase acting on RNA 1 (ADAR1) leads to tumor-specific transcriptome diversity with prognostic values for HCC. However, ADAR1 editase-dependent mechanisms governing liver cancer stem cell (LCSC) generation and maintenance have remained elusive. Approach and Results: RNA-seq profiling identified ADAR1-responsive recoding editing events in HCC and showed editing frequency of GLI1, rather than transcript abundance was clinically relevant. Functional differences in LCSC self-renewal and tumor aggressiveness between wild-type (GLI1^wt) and edited GLI1 (GLI1^edit) were elucidated. We showed that overediting of GLI1 induced an arginine-to-glycine (R701G) substitution, augmenting tumor-initiating potential and exhibiting a more aggressive phenotype. GLI1^R701G harbored weak affinity to SUFU, which in turn, promoted its cytoplasmic-to-nuclear translocation to support LCSC self-renewal by increased pluripotency gene expression. Moreover, editing predisposed to stabilize GLI1 by abrogating β-TrCP-GLI1 interaction. Integrative analysis of single-cell transcriptome further revealed hyperactivated mitophagy in ADAR1-enriched LCSCs. GLI1 editing promoted a metabolic switch to oxidative phosphorylation to control stress and stem-like state through PINK1-Parkin-mediated mitophagy in HCC, thereby conferring exclusive metastatic and sorafenib-resistant capacities. Conclusions: Our findings demonstrate a novel role of ADAR1 as an active regulator for LCSCs properties through editing GLI1 in the highly heterogeneous HCC.

Rhabdomyosarcoma (RMS) is one of the most common solid tumors in children and adolescents. Patients with relapsed/refractory RMS have limited treatment options, highlighting the urgency for the identification of novel therapeutic targets for RMS. In the present study, aurora kinase B (AURKB) was found to be highly expressed in RMS and associated with unfavorable prognosis of patients. Functional experiments indicated that inhibition of AURKB significantly reduced RMS cell proliferation, induced apoptosis and ferroptosis, and suppressed RMS growth in vivo. The highly expressed AURKB in RMS contributes to the apoptosis and ferroptosis resistance of tumor cells through the nucleophosmin 1 (NPM1)/Sp1 transcription factor (SP1)/acyl-CoA synthetase long-chain family member 5 (ACSL5) axis. Furthermore, inhibition of AURKB exerted an anti-RMS effect together with vincristine both in vitro and in vivo, with tolerable toxicity. The above findings provide insights we believe are new into the tumorigenesis of RMS, especially with regard to apoptosis or ferroptosis resistance, indicating that AURKB may be a potential target for clinical intervention in patients with RMS.

Epigenetic regulation is a pivotal factor during neuroblastoma (NB) pathogenesis and investigations into cancer epigenetics are actively underway to identify novel therapeutic strategies for NB patients. SUV39H1, a member of the H3K9 methyltransferase family, contributing to tumorigenesis across multiple malignancies. However, its specific role in NB remains unexplored. In this study, we conducted a high-throughput screen utilizing a compound library containing 288 epigenetic drugs, leading to the identification of chaetocin as the most potent NB inhibitor by targeting SUV39H1. Genetic manipulation and therapeutic inhibition of SUV39H1 significantly impacted proliferation, migration, cell cycle phases, and apoptosis in NB cells. Concurrently, chaetocin demonstrated robust anti-tumor efficacy in vivo with tolerable toxicity. RNA-seq unveiled that SUV39H1 knockdown and inhibition down-regulated cell cycle pathways, impacting vital genes such as AURKA. Besides, MCPIP1 emerged as a novel tumor suppressor following SUV39H1 inhibition, which decreased AURKA expression in NB. In detail, SUV39H1 mediated the enrichment of H3K9me3 at the promoter region of MCPIP1, repressing the MCPIP1-mediated degradation of AURKA and facilitating the subsequent accumulation of AURKA, which revealed the oncogenic role of SUV39H1 via the SUV39H1-MCPIP1-AURKA signaling axis in NB. Therapeutic inhibition of SUV39H1 using chaetocin emerges as an effective and safe strategy for NB patients. Illustration of the oncogenic pathway regulated by SUV39H1 in NB.