FN1 knockout inhibits tumorigenesis but promotes lung metastasis in hepatocellular carcinoma

Primary liver cancer is the sixth most common malignancy and third leading cause of cancer‑related deaths. HCC accounts for ~90% of cases, with HBV infection as a major aetiological factor. Poor prognosis is largely due to late diagnosis and high metastatic propensity.

Fibronectin (FN1), an ECM glycoprotein, is generally oncogenic by remodelling the ECM and activating integrin‑driven pathways. However, FN1 deficiency can paradoxically impair collagen barriers and promote metastasis. This duality is context‑dependent. HBV DNA integration into FN1 occurs preferentially in adjacent non‑cancerous tissues, contradicting FN1's pro‑oncogenic function. Clarifying FN1's role in HCC is therefore important.

Methods

Four sgRNAs targeting murine Fn1 were designed; sgFn1(1+4) was selected. Hepa1‑6 cells were transfected, and GFP‑positive clones were selected. Fn1‑KO was confirmed by Western blot. Functional assays (CCK‑8, colony formation, migration, invasion, adhesion) were performed. C57BL/6J and HBV transgenic mice were used for subcutaneous implantation and spontaneous HCC models. Flow cytometry, immunohistochemistry, and RNA‑seq were performed. TCGA‑LIHC data were analysed for immune infiltration.

Results

In vitro: Fn1‑KO cells showed impaired proliferation, migration, invasion, and adhesion. Collagen supplementation failed to rescue proliferation; exogenous Fn1 restored proliferation.

In vivo: Fn1‑KO xenografts grew more slowly than WT controls. Transcriptomic and immunohistochemical analyses confirmed downregulation of types I and III collagen.

Immune microenvironment: High FN1 expression correlated with increased M2 macrophages and reduced CD8⁺ T cells. Fn1‑KO xenografts showed decreased M2 macrophages and PD‑1⁺CD8⁺ T cells. Interferon‑stimulated genes were activated upon Fn1 deletion.

Spontaneous HCC: Fn1‑KO attenuated hepatic tumour incidence and malignant progression. M2 macrophages and PD‑1⁺CD8⁺ T cells were reduced.

Lung metastasis: Despite decreased primary tumour incidence, pulmonary metastatic tumours were comparable between groups.

Discussion

FN1 promotes HCC progression via collagen deposition (TGF‑β/PI3K/Akt) and ECM‑cytoskeleton signalling through integrin‑FAK/PI3K/Akt. Fn1‑KO disrupts this mechanotransduction, explaining why collagen failed to rescue proliferation. Paradoxically, FN1 deletion compromised adhesion and facilitated lung metastasis. Clinically, lower FN1 expression in primary HCC indicates higher risk of lung metastasis; closer pulmonary imaging surveillance should be considered.

Conclusions

FN1 deficiency suppresses hepatocyte malignant transformation and HCC progression but promotes pulmonary metastasis.

Full text

https://www.xiahepublishing.com/2310-8819/JCTH-2025-00689

The study was recently published in the Journal of Clinical and Translational Hepatology.

The Journal of Clinical and Translational Hepatology (JCTH) is owned by the Second Affiliated Hospital of Chongqing Medical University and published by XIA & HE Publishing Inc. JCTH publishes high quality, peer reviewed studies in the translational and clinical human health sciences of liver diseases. JCTH has established high standards for publication of original research, which are characterized by a study’s novelty, quality, and ethical conduct in the scientific process as well as in the communication of the research findings. Each issue includes articles by leading authorities on topics in hepatology that are germane to the most current challenges in the field. Special features include reports on the latest advances in drug development and technology that are relevant to liver diseases. Regular features of JCTH also include editorials, correspondences and invited commentaries on rapidly progressing areas in hepatology. All articles published by JCTH, both solicited and unsolicited, must pass our rigorous peer review process.

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