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

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.

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.

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.

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.