Apolipoprotein A1-encoding recombinant adenovirus remodels cholesterol metabolism in tumors and the tumor microenvironment to inhibit hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a prevalent malignant tumor requiring effective treatments. Oncolytic viruses induce anti-tumor responses but have limited efficacy. Apolipoprotein A1 (ApoA1) inhibits inflammation, modulates immunity, and promotes anti-oxidation. This study aims to construct an oncolytic adenovirus (Ad5)-ApoA1 for superior anti-tumor effects. We analyzed ApoA1 expression in tumors and its prognostic significance using public databases. Subsequently, we engineered a recombinant oncolytic adenovirus Ad5-ApoA1 and assessed its replication and oncolytic efficacy in vitro and in nude mice. The impact of Ad5-ApoA1 on the tumor microenvironment of HCC was evaluated through flow cytometry, transcriptome sequencing, single-cell sequencing, and other methodologies. Additionally, mechanisms of immune microenvironment modulation by Ad5-ApoA1 were explored. ApoA1 expression was down-regulated with HCC progression and significantly positively correlated with the prognosis of HCC patients. Ad5-ApoA1 exhibited robust oncolytic activity but showed no therapeutic effect on nude mice. However, it significantly inhibited HCC growth and prolonged the survival period of both healthy-immune and humanized immune-reconstituted NCG mice. Furthermore, Ad5-ApoA1 significantly promoted the expression of IFN-γ and GzmB in CD8⁺ T cells while inhibiting the expression of PD-1 and LAG-3. Notably, the cholesterol content in the CD8⁺ T cells studied was significantly correlated with the expression of PD-1 and LAG-3, with ApoA1 promoting cholesterol efflux and reducing cholesterol levels. Ad5-ApoA1 activates CD8⁺ T cells by promoting large-scale viral replication. High levels of ApoA1 protein expression promote cholesterol efflux, inhibit CD8⁺ T cell depletion, and reduce inflammatory factors, ultimately leading to superior therapeutic effects on hepatocellular carcinoma.