Anti‐cytoskeleton‐associated protein 4 (CKAP4) Ab and lenvatinib additively inhibit hepatocellular carcinoma growth. (A) Hep3B cells were stained with anti‐CKAP4 Ab under nonpermeabilizing conditions. Signals were detected using the tyramide signal amplification (TSA) system. Scale bar, 20 μm. (B) Hep3B (top left panels) and JHH6 cells (bottom left panels) treated with 20 μg/ml control IgG or anti‐CKAP4 Ab were subjected to the sphere formation assay. For each condition, the sizes of the spheres are expressed relative to the control condition. Scale bar, 50 μm. Data are presented as the mean ± SE. **p < 0.01 (ANOVA post hoc test). (C) Hep3B cells treated with 20 μg/ml anti‐CKAP4 Ab, 0.1 μM lenvatinib, or their combination were subjected to the sphere formation assay. Scale bar, 50 μm. **p < 0.01 (ANOVA post hoc test). (D) Hep3B cells were subcutaneously transplanted into immunodeficient mice. From day 2 after transplantation, control IgG or anti‐CKAP4 Ab (250 μg/body) was given intravenously three times a week with or without 1 mg/kg lenvatinib orally six times per week (control, n = 8; anti‐CKAP4 Ab, n = 14; lenvatinib, n = 11; anti‐CKAP4 Ab + lenvatinib, n = 10). Tumor development was observed for 21 days. Scale bar, 10 mm. Data are presented as the mean ± SE. *p < 0.05; **p < 0.01 (Wilcoxon's rank–sum test)