Synergy matrices combining lenvatinib with gefitinib, vandetanib, or pelitinib showed higher cytotoxicities in SNU398 cells with circUCK2(2,3) overexpression compared to cells without circUCK2(2,3) overexpression, both in short-term viability assays and long-term clonogenic assays (Fig. 6F, G, and Fig. S13), suggesting that circUCK2(2,3) may enhance the synergistic lethal effects of lenvatinib and EGFR inhibitors in HCC cells. Here, EGFR is linked to hepatocellular carcinoma.