Metastasis of Cancer Stem Cells Developed in the Microenvironment of Hepatocellular Carcinoma

Metastasis develops when cancer cells spread from the primary site of a malignant tumor to the surrounding and distant tissues, and it is the most critical problem in cancer treatment. Our group developed cancer stem cells (CSCs) from induced pluripotent stem cells (iPSCs) in the presence of a conditioned medium (CM) of cancer-derived cells. The CSCs were characterized by the formation of malignant tumors in vivo, followed by metastasis. In this study, CSCs converted from mouse iPSCs in the presence of CM from hepatocellular carcinoma (HCC) cell line Huh7 cells. These converted cells (miPS-Huh7cm cells) were established as the metastatic cells. The generated CSCs were injected into the liver or spleen of nude mice. Almost one month after transplantation, the tumors were excised, and the primary cultured cells derived from the malignant tumors and metastatic nodules were evaluated by stemness and metastatic markers to compare their differences. The miPS-Huh7cm cells exhibited metastatic potential, and efficiently formed malignant tumors with lung and/or liver lesions in vivo, whereas the injected miPS formed teratoma. The primary cultured cells derived from the malignant tumors and metastatic nodules sustained the expression of stemness markers, such as Nanog, Klf4 and c-Myc, and acquired cancer stem markers, such as CD90, CD44 and ALDH1. Simultaneously, the expression of metastatic markers, such as Slug, Twist1 and vimentin, in primary cells derived from the malignant tumors, was higher than in metastatic nodules. The CSCs derived from iPSCs, forming malignant tumors and displaying high metastasis, will provide a good animal model to study the mechanisms of metastasis.