Therefore, there is a clear need for further in vitro studies to explore the mechanism of the RT-PK phenomenon of lenvatinib in the future; for example, by comparing various HCC tumor cell lines with nontumorigenic hepatic cells to assess cell viability, colony formation, cell cycle situations, DNA double-strand break, DNA repair, CYP 3A4 activity, and P-gp activity. The gene discussed is PGP; the disease is hepatocellular carcinoma.