Hepatocellular carcinoma (HCC) is an aggressive disease that occurs predominantly in men. Estrogen elicits protective effects against HCC development. Elucidation of the estrogen-regulated biological processes that suppress HCC could lead to improved prevention and treatment strategies. Here, we performed transcriptomic analyses on mouse and human liver cancer and identified lecithin cholesterol acyltransferase (LCAT) as the most highly estrogen-upregulated gene and a biomarker of favorable prognosis. LCAT upregulation inhibited HCC in vitro and in vivo and mediated estrogen-induced suppression of HCC in an ESR1-dependent manner. LCAT facilitated high-density lipoprotein cholesterol production and uptake via the LDLR and SCARB1 pathways. Consistently, high HDL-C levels corresponded to a favorable prognosis in HCC patients. The enhanced HDL-C absorption induced by LCAT impaired SREBP2 maturation, which ultimately suppressed cholesterol biosynthesis and dampened HCC cell proliferation. HDL-C alone inhibited HCC growth comparably to the cholesterol-lowering drug lovastatin, and SREBF2 overexpression abolished the inhibitory activity of LCAT. Clinical observations and cross-analyses of multiple databases confirmed the correlation of elevated LCAT and HDL-C levels to reduced cholesterol synthesis and improved HCC patient prognosis. Furthermore, LCAT deficiency mimicked whereas LCAT overexpression abrogated the tumor growth–promoting effects of ovariectomy in HCC-bearing female mice. Most importantly, HDL-C and LCAT delayed the development of subcutaneous tumors in nude mice, and HDL-C synergized with lenvatinib to eradicate orthotopic liver tumors. Collectively, this study reveals that estrogen upregulates LCAT to maintain cholesterol homeostasis and to dampen hepatocarcinogenesis. LCAT and HDL-C represent potential prognostic and therapeutic biomarkers for targeting cholesterol homeostasis as a strategy for treating HCC. Significance: Estrogen mediates the sex differences in hepatocellular carcinoma development by reducing cholesterol biosynthesis through activation of an LCAT/HDL-C axis, providing strategies for improving liver cancer prevention, prognosis, and treatment.

Background: Dysregulated ubiquitination modification occupies a pivotal role in hepatocellular carcinoma (HCC) tumorigenesis and progression. The ubiquitin aldehyde binding 1 (OTUB1) was aberrantly upregulated and exhibited the pro-tumorigenic function in HCC. However, the underlying mechanisms and responsible targets of OTUB1 remain unclear. Methods: First, bioinformatics analysis, western blot and immunohistochemistry staining were applied to analyze OTUB1 expression in HCC specimens. Then, immunoprecipitation assay-tandem mass spectrometry (MS) combined with the gene set enrichment analysis (GSEA) was used to explore the downstream target of OTUB1. Co-immunoprecipitation and ubiquitination assays were used to identify the mechanisms involved. Finally, we explored the regulatory effect of MAZ on OTUB1 through ChIP-qPCR and dual-luciferase reporter assay. Results: OTUB1 was broadly elevated in HCC tissues and promoted the proliferation and metastasis of HCC in vitro and in vivo. The receptor for activated C kinase 1 (RACK1) performed as a functional partner of OTUB1 and its hyperactivation was associated with aggressive development and other malignant features in HCC by activating oncogenes transcription. Mechanistically, OTUB1 directly bound to RACK1 at its C-terminal domain and decreased the K48-linked ubiquitination of RACK1 through its non-canonical suppression of ubiquitination activity, which stabilized RACK1 protein levels in HCC cells. Therefore, OTUB1 significantly increased multiple oncogenes expression and activated PI3K/AKT and FAK/ERK signaling in a RACK1-dependent manner in HCC. Moreover, the transcription factor MAZ upregulated OTUB1 expression through identifying a putative response element of OTUB1 promoter area. Conclusions: Our findings might provide a new therapeutic strategy for HCC by modifying the MAZ-OTUB1-RACK1 axis.

Non-alcoholic fatty liver disease (NAFLD) is expected to become the leading risk factor for liver cancer, surpassing viral hepatitis. Unlike viral hepatitis-related hepatocellular carcinoma (HCC), the role of excessive nutrient supply in steatotic HCC is not well understood, hindering effective prevention and treatment strategies. Therefore, it is crucial to identify key molecules in the pathogenesis of steatotic HCC, investigate changes in metabolic reprogramming due to excessive fatty acid (FA) supply, understand its molecular mechanisms, and find potential therapeutic targets. Trans-species transcriptome analysis identified Ring Finger Protein 5 (RNF5) as a critical regulator of steatotic HCC. RNF5 upregulation is associated with poor prognosis in steatotic HCC compared to canonical HCC. In vitro and in vivo studies showed that RNF5 exacerbates HCC in the presence of additional FA supply. Lipidomics and transcriptome analyses revealed that RNF5 significantly increases carnitine palmitoyltransferase 1A (CPT1A) mRNA levels and is positively correlated with fatty acid oxidation (FAO). Protein interaction analysis demonstrated that RNF5 promotes K63-type ubiquitination of insulin-like growth factor-2 mRNA-binding protein 1 (IGF2BP1), enhancing CPT1A mRNA stabilization through m6A modification. Additionally, peroxisome proliferator-activated receptor gamma (PPARγ) was found to activate RNF5 expression specifically in HCC cells. Mechanistically, excessive exogenous FAs reorganize FA metabolism in HCC cells, worsening steatotic HCC via the PPARγ-RNF5-IGF2BP1-CPT1A axis. This study highlights a distinct FA metabolism pattern in steatotic HCC, providing valuable insights for potential therapeutic targets.

Aberrant upregulation of the intracellular antioxidant glutathione (GSH) is implicated in promoting tumor proliferation, inducing drug resistance, and inhibiting ferroptosis across various malignancies, including hepatocellular carcinoma (HCC). Targeting the mechanism underlying GSH upregulation in HCC could represent a therapeutic strategy to improve patient outcomes. In this study, we employed a genome-wide CRISPR/Cas9 screen and targeted metabolomics to identify the acetyltransferase ARD1 as a pivotal facilitator of de novo GSH synthesis in HCC. Notably, ARD1 upregulation was positively correlated with elevated GSH levels and poor prognosis in patients with HCC. In vivo and in vitro functional assays revealed that ARD1 promoted HCC cell proliferation and inhibited ferroptosis in a GSH-dependent manner. LC/MS-MS–based stable isotope labeling revealed that ARD1 increased GSH levels by stabilizing γ-glutamylcysteine ligase catalytic (GCLC) subunit mRNA, which was mediated by the RNA-binding protein PABPC1. Mechanistically, ARD1 acetylated PABPC1 at Ki67, augmenting its cytoplasmic retention by disrupting PABPC1–importin α7 complex formation. Cytoplasmic PABPC1 then interacted with eIF4G to collaboratively stabilize GCLC mRNA, preventing its degradation, increasing GSH synthesis, and ultimately conferring ferroptosis resistance in HCC cells. Furthermore, oxidative stress induced by hydrogen peroxide suppressed ARD1 ubiquitination and degradation, thereby promoting PABPC1 cytoplasmic translocation and inducing GCLC expression. ARD1 suppression promoted sorafenib-mediated ferroptosis in xenografts derived from patients with HCC tumors with high ARD1 and GCLC expression. Overall, this research uncovers an oxidative stress–ARD1–PABPC1–GCLC axis with a crucial role in GSH metabolic reprogramming and ferroptosis regulation in HCC and reveals a strategy for ferroptosis-based targeted therapy for HCC. Significance: The acetyltransferase ARD1 promotes hepatocellular carcinoma progression, inhibits ferroptosis by upregulating GCLC to facilitate de novo synthesis of glutathione, and can be targeted to improve sorafenib efficacy.