FIGURE 4.

IRAK1/4 Inhibitor I enhanced the antitumor effects of lenvatinib in HTC/C3 xenograft mouse model. A, HTC/C3 cells (1 × 10⁷) were inoculated into the flank region of 7‐wk‐old female nude mice (BALB/c‐nu) subcutaneously. After tumor formation, the mice were assigned to each group (vehicle control, IRAK1/4 Inhibitor I, lenvatinib, and combined IRAK1/4 Inhibitor I and lenvatinib). Lenvatinib was administrated orally at a dose of 10 mg/kg daily for 14 d and IRAK1/4 Inhibitor I was administrated intraperitoneally at a dose of 5 mg/kg daily for 14 d. Differences between groups were evaluated using the Steel‐Dwass test after 1‐way ANOVA. Data are presented as mean ± SD. B, Effect of the combined use of lenvatinib and IRAK1/4 Inhibitor I on body weight in the HTC/C3 xenograft mouse model. Time course of the body weights of the vehicle control, IRAK1/4 Inhibitor I, lenvatinib, and combination groups are shown. Data are presented as mean ±SD. C, Effect of the combined use of lenvatinib and IRAK1/4 Inhibitor I on phosphorylation status of IRAK1, IRAK4, and ERK in resected tumors from HTC/C3 xenograft mouse model. Tumors were resected after 14 d of treatment with vehicle control, IRAK1/4 Inhibitor I alone, lenvatinib alone, and combination groups. Protein expression levels of IRAK1, IRAK4, and ERK were evaluated by western blot analysis. D, Antiangiogenic effects of the combined use of lenvatinib and IRAK1/4 Inhibitor I in the HTC/C3 xenograft mouse model. Immunohistochemical staining of vascular endothelial cells of resected tumor tissue was performed using anti‐CD31 antibody (×100 magnification). High microvessel density (MVD) sites in the vehicle control, IRAK1/4 Inhibitor I, lenvatinib, and combination groups were imaged at ×100 magnification. CD31 positive areas are shown by a red color. E, The number of vessels per mm² in high‐MVD sites was counted using ImageJ software and shown graphically. Differences between groups were evaluated using Steel‐Dwass test after 1‐way ANOVA. Data are presented as mean ± SD