Alantolactone Induces Apoptosis in Imatinib-Sensitive and -Resistant CML Cells by Inhibiting NF-KappaB Signaling and Degrading Bcr/Abl Protein

Firstly, we used CCK-8 assay to determine the cell viability and found that K562s were inhibited up to 64.5% after 48 hours of incubation of 10uM concentration of alantolactone, Annexin V⁺ cells were up to 68% which were confirmed by morphological observation, and apoptosis-related proteins were activated during the treatment, suggesting its inducing-apoptosis ability. Secondly, incubation of alantolactone could inhibit NF-kB signaling activity, proved by inhibition of IkBa phosphorylation and blockade of nuclear translocation of p65, while the luciferase assay further revealed the inhibited transcription of NF-kB dependent reporter gene, which was confirmed by immunofluorescence staining. Of note, Bcr-Abl protein was specifically and rapidly down-regulated as early as 6 hours after 10uM of alantolactone treatment. And alantolactone-induced Bcr-Abl down-regulation could be partially reversed by the autophagy inhibitor chloroquine but not by the proteasome inhibitor MG132 or bortezomib, indicating that autophagy may contributes to Bcr-Abl reduction. Furthermore, similar concentration of alantolactone could also induce apoptosis in K562r cells and inhibited the growth of primary CD34⁺ leukemic cells from CML patients.

Collectively, our results primarily demonstrated that alantolactone could induce apoptosis in CML cells, regardless of imatinib-sensitive or -resistant, by inhibiting NF-kB signaling and depleting Bcr/Abl through a unique mechanism. Alantolactone could be used as a probe for deciphering the mechanism of Bcr-Abl destruction and NF-kB inhibition, and this agent may be a promising candidate for treating CML patients.

No relevant conflicts of interest to declare.