Transcatheter arterial embolization promotes liver tumor metastasis by increasing the population of circulating tumor cells

Transcatheter arterial embolization (TAE) is widely used as an effective palliative treatment for hepatocellular carcinoma (HCC), and can prolong survival time. However, the high incidence of tumor recurrence and metastasis after TAE is still a major problem. Recent studies demonstrated that circulating tumor cells (CTCs) contribute to tumor metastasis. In this study, we tried to clarify whether the residual HCC after TAE can increase metastasis by increasing the number of CTCs. An orthotopic liver tumor model in the Buffalo rat was established using green fluorescent protein (GFP)-transfected HCC cell line, McA-RH7777. Two weeks after orthotopic liver tumor implantation, the rats underwent TAE treatment from the gastroduodenal artery. Iodized oil or saline was injected intra-arterially. Blood samples were taken on day 0, 1, 3, 7, 14, and 21 for detection of CTCs after TAE treatment. We analyzed the number of CTCs and assessed the metastatic potential of surviving tumor cells in rats between TAE and control groups. Our results demonstrated that the metastatic colonies in the lung were significantly increased by TAE treatment. The number of CTCs was also significantly increased by TAE treatment from day 7 to day 21. The expression of hypoxia-inducible factor (HIF)-1α and epithelial–mesenchymal transition (EMT) marker proteins (N-cadherin and vimentin) was upregulated, but E-cadherin was downregulated after TAE treatment. In conclusion, the metastatic potential of residual HCC can be induced by TAE treatment in a rat liver tumor model, which involves the acquisition of EMT features and an increased number of CTCs.