JaponiconeA induces apoptosis of bortezomib-sensitive and -resistant myeloma cells in vitro and in vivo by targeting IKKβ

OBJECTIVE: Multiple myeloma (MM) remains incurable with high rates of relapse. New therapeutic drugs are therefore urgently needed to improve the prognosis. JaponiconeA (JA), a natural product isolated from Inula japonica Thunb, has shown good anti-MM potential. A comprehensive study should therefore be conducted to identify both the in vitro and in vivo mechanisms of the anti-MM effects of JA. METHODS: CCK8 assays and flow cytometry were used to detect the proliferation, apoptosis, and cell cycle of MM cell lines when treated with JA. In vivo experiments were conducted using subcutaneous xenograft mouse models. We also identified possible targets and the mechanism of JA using RNA-seq and c-Map databases, and identified the specific targets of JA in bortezomib-sensitive and -resistant MM cell lines using CETSA, DARTS, and rescue experiments. Furthermore, JA and bortezomib were used separately or together to characterize their possible synergistic effects. RESULTS: In vitro, JA inhibited proliferation, and induced apoptosis and G2/M phase arrest in MM cell lines, and selectively killed primary CD138(+) MM cells. In vivo, JA also demonstrated a strong anti-tumor effect with no observable toxicity. In addition, JA showed synergetic effects in combination with bortezomib, and enhanced the anti-tumor effect of bortezomib in bortezomib-resistant cells. CETSA and DARTS confirmed direct binding of JA to NF-κB inhibitor kinase beta (IKKβ), and overexpression of IKKβ or knockdown of IκBα partially rescued the apoptosis induced by JA. CONCLUSIONS: JA exhibited strong anti-tumor effects in MM. It sensitized myeloma cells to bortezomib and overcame NF-κB-induced drug resistance by inhibiting IKKβ, providing a new treatment strategy for MM patients.