FSTL1 Secreted by Activated Fibroblasts Promotes Hepatocellular Carcinoma Metastasis and Stemness

Cancer Res. 2021 Nov 15;81(22):5692-5705. doi: 10.1158/0008-5472.CAN-20-4226. Epub 2021 Sep 22.


The tumor microenvironment plays a critical role in maintaining the immature phenotype of tumor-initiating cells (TIC) to promote cancer. Hepatocellular carcinoma (HCC) is a unique disease in that it develops in the setting of fibrosis and cirrhosis. This pathologic state commonly shows an enrichment of stromal myofibroblasts, which constitute the bulk of the tumor microenvironment and contribute to disease progression. Follistatin-like 1 (FSTL1) has been widely reported as a proinflammatory mediator in different fibrosis-related and inflammatory diseases. Here we show FSTL1 expression to be closely correlated with activated fibroblasts and to be elevated in regenerative, fibrotic, and disease liver states in various mouse models. Consistently, FSTL1 lineage cells gave rise to myofibroblasts in a CCL4-induced hepatic fibrosis mouse model. Clinically, high FSTL1 in fibroblast activation protein-positive (FAP+) fibroblasts were significantly correlated with more advanced tumors in patients with HCC. Although FSTL1 was expressed in primary fibroblasts derived from patients with HCC, it was barely detectable in HCC cell lines. Functional investigations revealed that treatment of HCC cells and patient-derived 3D organoids with recombinant FSTL1 or with conditioned medium collected from hepatic stellate cells or from cells overexpressing FSTL1 could promote HCC growth and metastasis. FSTL1 bound to TLR4 receptor, resulting in activation of AKT/mTOR/4EBP1 signaling. In a preclinical mouse model, blockade of FSTL1 mitigated HCC malignancy and metastasis, sensitized HCC tumors to sorafenib, prolonged survival, and eradicated the TIC subset. Collectively, these data suggest that FSTL1 may serve as an important novel diagnostic/prognostic biomarker and therapeutic target in HCC. SIGNIFICANCE: This study shows that FSTL1 secreted by activated fibroblasts in the liver microenvironment augments hepatocellular carcinoma malignancy, providing a potential new strategy to improve treatment of this aggressive disease.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptor Proteins, Signal Transducing / genetics
  • Adaptor Proteins, Signal Transducing / metabolism
  • Animals
  • Apoptosis
  • Biomarkers, Tumor / genetics
  • Biomarkers, Tumor / metabolism*
  • Carcinoma, Hepatocellular / genetics
  • Carcinoma, Hepatocellular / metabolism
  • Carcinoma, Hepatocellular / secondary*
  • Cell Cycle Proteins / genetics
  • Cell Cycle Proteins / metabolism
  • Cell Proliferation
  • Fibroblasts / metabolism
  • Fibroblasts / pathology*
  • Follistatin-Related Proteins / genetics
  • Follistatin-Related Proteins / metabolism*
  • Gene Expression Regulation, Neoplastic*
  • Humans
  • Liver Neoplasms / genetics
  • Liver Neoplasms / metabolism
  • Liver Neoplasms / pathology*
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Neoplastic Stem Cells / metabolism
  • Neoplastic Stem Cells / pathology*
  • Prognosis
  • Proto-Oncogene Proteins c-akt / genetics
  • Proto-Oncogene Proteins c-akt / metabolism
  • TOR Serine-Threonine Kinases / genetics
  • TOR Serine-Threonine Kinases / metabolism
  • Toll-Like Receptor 4 / genetics
  • Toll-Like Receptor 4 / metabolism
  • Tumor Cells, Cultured
  • Xenograft Model Antitumor Assays


  • Adaptor Proteins, Signal Transducing
  • Biomarkers, Tumor
  • Cell Cycle Proteins
  • EIF4EBP1 protein, human
  • Follistatin-Related Proteins
  • Toll-Like Receptor 4
  • FSTL1 protein, human
  • MTOR protein, human
  • AKT1 protein, human
  • Proto-Oncogene Proteins c-akt
  • TOR Serine-Threonine Kinases