ETV1/TGF-β/SMAD4-CTGF Axis Activated Tumor-CAFs Crosstalk Promotes Poor Progression in Hepatocellular Carcinoma Patients.

The transcription factor ETV1 plays a critical oncogenic role in tumors; its function in cancer-associated fibroblasts (CAFs) remains poorly understood. We identified a positive correlation between ETV1 and CAFs infiltration in TIMER2.0, and overexpressed ETV1 predicted a poor prognosis in patients from TCGA. Consistently, ETV1 positively correlated with markers of CAFs. α-SMA, PDGFRβ, TGF-β, COL1A1, and CTGF, markers of CAFs, were downregulated in LI90 cells cocultured with ETV1 low-expressed Huh7 cells, and CTGF presented the most pronounced reduction. Though no direct ETV1 binding domains were predicted in the CTGF promoter, ETV1 activates TGF-β signaling in tumor tissues from TCGA. Intriguingly, multiple SMAD4 binding domains were predicted in the promoter of CTGF. Luciferase reporter assays, ChIP-PCR, and EMSA presented that SMAD4 binds specifically to the P3 domain in CTGF promoter, which activated the transcription of CTGF. Rescue experiments indicated that ETV1 induced CTGF expression for the TGF-β/SMAD4 pathway in ETV1-shRNA-Lv infected Huh7 cells cocultured with LI90 cells infected with SMAD4-oe-Lv. In humanized immune-reconstituted mouse models, low expression of ETV1 inhibited tumor growth and CTGF expression. Moreover, DEN-induced murine hepatocellular carcinoma tissues exhibited elevated expression of ETV1, CTGF, PCNA, and Ki67. Clinically, ETV1 was overexpressed in tumor tissues and predicted poor progression in HCC patients. Thus, our findings reveal a novel ETV1/TGF/β/SMAD-CTGF signaling axis within the tumor microenvironment that facilitates tumor-CAFs communication, ultimately promoting aggressive HCC progression through enhanced tumor cell proliferation.