Stromal ACTA2 Counteracts TCDD-Induced Hepatocarcinogenesis via Suppression of the PI3K–AKT–mTOR Pathway

Purpose: 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is a persistent environmental pollutant that promotes hepatocellular carcinoma (HCC) through non-genotoxic mechanisms. However, stromal regulatory factors that counteract its tumor-promoting effects remain poorly defined. This study aimed to elucidate the role of actin alpha-2 (ACTA2) in TCDD-associated hepatocarcinogenesis. Methods: An integrative strategy combining network toxicology, Mendelian randomization, multi-omics and single-cell analyses, molecular docking and molecular dynamics simulations, along with in vitro experiments, was employed to investigate the functional role of ACTA2. Results: ACTA2 was identified as a stromal-associated factor linked to reduced HCC risk and improved patient survival. Single-cell and multi-omics analyses revealed that ACTA2 is predominantly expressed in hepatic stellate cells and fibroblast-like populations, reflecting tumor microenvironment composition rather than tumor cell–intrinsic expression. Functional enrichment analyses indicated that ACTA2 is associated with extracellular matrix remodeling and PI3K–AKT signaling. Molecular simulations demonstrated stable binding of TCDD to ACTA2 (ΔG_bind ≈ − 7.05 kcal/mol), suggesting potential structural perturbation. In vitro experiments showed that TCDD downregulated ACTA2 expression, promoted proliferation of LX-2 and cancer-associated fibroblasts (CAFs), and activated PI3K–AKT–mTOR signaling, whereas ACTA2 overexpression attenuated these effects. Conclusion: ACTA2 acts as a context-dependent stromal regulator that modulates PI3K–AKT–mTOR signaling in TCDD-induced hepatocarcinogenesis. These findings highlight the importance of stromal remodeling in environmental carcinogenesis and suggest ACTA2 as a potential biomarker and therapeutic target in dioxin-associated HCC. Keywords: TCDD, ACTA2, PI3K–AKT–mTOR, hepatocellular carcinoma, environmental carcinogenesis