HCCaging: a liver physiological aging-related biomarker for hepatocellular carcinoma diagnosis based on transcriptome data.

Aging is a fundamental biological process that influences cancer development in a context-dependent manner; however, how aging-related programs manifest in hepatocellular carcinoma (HCC) remains incompletely understood. Here, we systematically characterized aging-associated features in HCC by establishing a liver cancer-specific aging signature, termed HCCaging, across more than 2,000 tumor samples from 16 independent cohorts. We comprehensively evaluated its heterogeneity and associations with clinical outcomes, tumor stage, immune infiltration, and therapeutic response. The HCCaging score increased with chronological age, was higher in normal liver than tumor tissues, and elevated in early- versus late-stage tumors. In contrast, 13 previously reported aging- or senescence-related gene sets failed to show consistent patterns across these conditions in HCC. Machine learning models, including gradient boosting machines and random forests, achieved higher accuracy in distinguishing tumor from non-tumor samples using the HCCaging score compared with other 13 aging- or senescence-gene sets across eight independent HCC cohorts. Single-cell transcriptomic profiling revealed that HCCaging increased with age, particularly within epithelial compartments, reaching its highest levels in hepatocytes. Notably, although the proportion of T/NK cells declined with aging, their functional programs, including activated effector function, chemokine/chemokine receptor signaling, cytolytic activity, and pro-inflammatory pathways, were enhanced in older individuals. The HCCaging score, together with key genes ACAA1 and ESR1, were negatively correlated with T/NK cell infiltration, anti-inflammatory activity, and anti-apoptotic signatures, but positively correlated with pro-apoptotic, pro-inflammatory, chemokine, and cytolytic pathways. Furthermore, increased expression of XCL1 and XCL2 in T/NK cells with aging correlated positively with HCCaging, ACAA1, and ESR1, suggesting preserved or even enhanced antitumor potential of T/NK cells in older patients. Collectively, these findings highlight the dual role of aging in liver tumorigenesis. Hepatic aging and enhanced T/NK cell effector function may confer tumor-protective effects, whereas the concomitant decline in overall T/NK cell infiltration likely compromises immunosurveillance, thereby increasing carcinogenic susceptibility in the aging liver. This study provides new insights into the heterogeneity of hepatic aging and its complex interplay with the HCC tumor microenvironment and clinical outcomes.