Immunohistochemistry and image analysis, Apoptosis induction in shRNA-transduced importin β1 knockdown HeLa cells with administration of agonistic anti-hDR5 mAb (CS-1008) in vivo, Antitumor effect of importin β1 knockdown via atelocollagen delivery of shRNA in combination with CS-1008 on HeLa and HepG2 xenograft models, Effect of importazole on apoptosis induction by rTRAIL in HeLa and HepG2 cells in vitro, Body weights of the mice during the treatment importazole and/or CS-1008 in the experiments presented in Fig. 6, Importin β1 expression in the xenograft tumor tissues dissected from the mice treated with hIgG and doxycycline in the experiments presented in Fig. 3A and B.
Ministry of Education, Culture, Sports, Science and Technology, Japan
ARTICLE ABSTRACTTNF-related apoptosis-inducing ligand (TRAIL) and an agonistic antibody against the death-inducing TRAIL receptor 5, DR5, are thought to selectively induce tumor cell death and therefore, have gained attention as potential therapeutics currently under investigation in several clinical trials. However, some tumor cells are resistant to TRAIL/DR5–induced cell death, even though they express DR5. Previously, we reported that DR5 is transported into the nucleus by importin β1, and knockdown of importin β1 upregulates cell surface expression of DR5 resulting in increased TRAIL sensitivity in vitro. Here, we examined the impact of importin β1 knockdown on agonistic anti-human DR5 (hDR5) antibody therapy. Drug-inducible importin β1 knockdown sensitizes HeLa cells to TRAIL-induced cell death in vitro, and exerts an antitumor effect when combined with agonistic anti-hDR5 antibody administration in vivo. Therapeutic importin β1 knockdown, administered via the atelocollagen delivery system, as well as treatment with the importin β inhibitor, importazole, induced regression and/or eradication of two human TRAIL-resistant tumor cells when combined with agonistic anti-hDR5 antibody treatment. Thus, these findings suggest that the inhibition of importin β1 would be useful to improve the therapeutic effects of agonistic anti-hDR5 antibody against TRAIL-resistant cancers.