Antitumor effects of blocking protein neddylation in T315I-BCR-ABL leukemia cells and leukemia stem cells

Imatinib (IM) revolutionized the treatment of chronic myeloid leukemia (CML) but drug resistance and disease recurrence remain a challenge. In this study, we suggest a novel strategy based on blocking protein neddylation to address BCR-ABL point mutations and leukemia stem cells (LSCs) that lie at the root of IM-resistant recurrences. Based on the finding that the NEDD8-activating enzyme subunit NAE1 is overexpressed in CML cells, we hypothesized that the function of certain neddylation-dependent protein substrates might be targeted to therapeutic ends in IM-resistant CML cells and LSCs. In support of this hypothesis, we demonstrated that the NAE1 inhibitor MLN4924 induced G2/M-phase arrest and apoptosis in bulk CML cells with wild-type p53, regardless of their T315I mutation status in BCR-ABL. Moreover, MLN4924 inhibited the survival and self-renewal of primary human CML CD34+ cells and LSCs in CML-bearing mice via accumulation of p27kip1 in the nucleus. Notably, p27kip1 silencing attenuated the suppressive effect of MLN4924 on the maintenance of LSCs in CML-bearing mice. Taken together, our findings offer a preclinical proof of concept for targeting protein neddylation as a novel therapeutic strategy to override mutational and LSC-derived IM resistance in CML.

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