Uncoupling Metastasis and Epithelial‐to‐Mesenchymal Transition in sgP19/kRAS‐Driven Spontaneous Metastatic Liver Tumor Model

Epithelial-to-mesenchymal transition (EMT) is an early event during tumor metastasis. Here, the relevance of EMT in liver carcinogenesis and metastasis is sought to be determined in a murine mixed typical intrahepatic cholangiocarcinoma (iCCA)/sarcomatoid iCCA liver tumor model using CRISPR/Cas9-based gene deletion of p19 (sgP19) in combination with transposon-based expression of the activated form of pCaggs-kRAS^G12D (kRAS) in the mouse liver (sgP19/kRAS mixed model). It discovered that metastasis in the lymph node, lung, or kidney occurred in the sgP19/kRAS mixed model. Both typical iCCA tumor cells with epithelial features and sarcomatoid tumor cells with mesenchymal features could be detected in this model. Lineage tracing technology is applied to confirm the metastasis induced in the sgP19/kRAS model. Subsequently, the gain of expression of mesenchymal marker vimentin in tumor cells revealed the induction of EMT in the sgP19/kRAS model, and it is induced by activating the TGFβ/ZEB1 signaling pathway. Altogether, the study suggests that TGFβ/ZEB1 mediates the induction of EMT in iCCA, while targeting EMT failed to inhibit iCCA development or tumor metastasis, disputing the claims that EMT is a major molecular event leading to tumor metastasis.