HBx/DTL Positive Feedback Loop Promotes HBV-Related Hepatocellular Carcinoma Progression

Although hepatitis B virus (HBV) infection is a well-documented etiologic factor for hepatocellular carcinoma (HCC), which ranks as the third leading cause of cancer-related mortality globally, the mechanism by which HBV facilitates cancer development remains largely elusive. In this study, we employed advanced methodologies including, single-cell RNA sequencing, flow cytometry, western blot analysis, chromatin immunoprecipitation-qPCR and Cut&Tag to investigate the expression of DTL and its biological functions in HCC. We observed that DTL is overexpressed in HBV-positive HCC samples, with its elevated expression being associated with increased tumor cell proliferation and reduced overall and disease-free survival rates. The upregulation of DTL expression was specifically induced by the HBV regulatory protein HBx, thereby substantiating the oncogenic potential of HBV. Mechanistically, our findings indicated that the HBx protein augments DTL transcription by binding to its promoter region, subsequently facilitating HCC cell proliferation and modulating cell cycle progression, particularly by increasing the proportion of cells in the S phase. Furthermore, DTL was identified as a protein that interacts with HBx and associates with the Cullin4-RING ubiquitin ligases (CRL4s), thereby stabilizing HBx by reducing its ubiquitin-mediated degradation. In vivo experiments demonstrated that DTL not only facilitated cancer cell proliferation by modulating the cell cycle but also promoted tumorigenesis in nude mice. Moreover, DTL expression modifies the tumor immune microenvironment by increasing the proportion of regulatory T cells, thereby contributing to immune evasion. In summary, our findings underscore the pivotal role of DTL as a key regulator in HBV-related HCC by influencing cell cycle progression and establishing a positive feedback loop involving the HBx-DTL-CRL4s. These insights expand our understanding of HBV oncogenic mechanisms and suggest that DTL could serve as a novel biomarker and therapeutic target, potentially enhancing patient outcomes.