Transcription factor JUNB is required for transformation of EpCAM-positive hepatocellular carcinoma (HCC) cells into CD90-positive HCC cells in vitro

Hepatocellular carcinoma (HCC) harbors two types of stem cells—epithelial and mesenchymal stem cells. The mechanism by which epithelial EpCAM-positive HCC cells transform into mesenchymal CD90-positive HCC cells remains unclear. On peritumoral fibrotic nodules, epithelial HCC cells form communities with stromal cells, driving tumor growth and malignancy. We aimed to clarify the mechanism by which epithelial cell adhesion molecule (EpCAM)-positive HCC cells contribute to the phenotype of mesenchymal CD90-positive HCC cells that metastasize to distant sites by elucidating the interaction between EpCAM-positive HCC cells and fibroblasts. EpCAM-positive CD90-negative epithelial HCC cells (Huh1, Huh7, and HCC cells) were converted into metastasis-prone CD90-positive HCC cells by co-culture with fibroblasts (Lx-2 and Tig3-20). We identified the transcription factor JUNB as responsible for this altered phenotype. We found that the overexpression of JUNB in CD90-negative epithelial HCC cells resulted in significant transformation to mesenchymal CD90-positive HCC in vitro and in vivo, showing metastatic potential to the lungs. In addition, the JUNB expression in EpCAM-positive hepatoma cells was increased by paracrine stimulation with fibroblast-derived TGFb1. This study unravels the mechanism by which fibroblasts aggravate the malignancy of liver cancer, and the results suggest that JUNB may be a target for treating liver cancer metastasis.