Deguelin, a selective silencer of the NPM1 mutant, potentiates apoptosis and induces differentiation in AML cells carrying the NPM1 mutation

Abstract

Nucleophosmin (NPM1) is a multifunctional protein that functions as a molecular chaperone, shuttling between the nucleolus and the cytoplasm. In up to one third of patients with acute myeloid leukemia, mutation of NPM1 results in the aberrant cytoplasmic accumulation of mutant protein and is thought to be responsible for leukemogenesis. Deguelin, a rotenoid isolated from several plant species, has been shown to be a strong anti-tumor agent. Human leukemia cell lines were used for in vitro studies. Drug efficacy was evaluated by apoptosis and differentiation assays, and associated molecular events were assessed by Western blot. Gene silencing was performed using small interfering RNA (siRNA). Deguelin exhibited strong cytotoxic activity in the cell line of OCI-AML3 and selectively down-regulated the NPM1 mutant protein, which was accompanied by up-regulation of the activity of caspase-6 and caspase-8 in high concentrations. Deguelin induced differentiation of OCI-AML3 cells at a nontoxic concentration which was associated with a decrease in expression of activated caspase-8, p53, p21, and the 30-kD form of CCAAT/enhancer binding protein α (C/EBPα), whereas no effects were found in OCIM2 cells expressing NPM-wt. Moreover, treatment with siRNA in the NPM mutant cell line OCI-AML3 decreased expression of p53, p21, pro-caspase-8, and the 30-kD form of C/EBPα, and it inhibited proliferation and induced differentiation of the OCI-AML3 cells. In conclusion, deguelin is a potent in vitro inhibitor of the mutant form of NPM1, which provides the molecular basis for its anti-leukemia activities in NPM1 mutant acute myeloid leukemia cells.

Arsenic trioxide and all-trans retinoic acid target NPM1 mutant oncoprotein levels and induce apoptosis in NPM1-mutated AML cells

“…In the NPM1 wild-type AML cell lines, besides a slight effect of ATO/ATRA combination in U937, ATO/ATRA pretreatment did not show any effect on DNR sensitivity ( Figure 6C-D). Although observed mainly in OCI/AML3, these findings are in keeping with previous reports showing that downregulation of NPM1 sensitizes AML cells to chemotherapy [31][32][33][34][35] and has clinical implications.…”

“…Evidence that NPM1 mutant downregulation can be a suitable way to target NPM1-mutated AML cells comes also from previous reports showing that NPM1 mutant silencing either by drugs (ie, deguelin, 33 and (-)-epigallocatechin-3-gallate 34 ) or inhibitory RNA 31 leads to apoptosis and sensitizes cells to chemotherapeutics.…”

Molecules that target nucleophosmin for cancer treatment: an update

“…ECGT is the major polyphenol extracted from green tea, widely investigated for its antioxidant properties and for its possible effects in cancer prevention [123]. In both cases it was shown that treatment of OCI-AML3 cells with deguelin [124] and of IMS-M2 cells (also expressing NPM1c+) with ECGT [125], was effective in reducing NPM1c+ but not NPM1wt levels and in inducing apoptosis. NPM1 levels were instead not consistently affected when treating AML cell lines expressing NPM1wt only [124].…”

Steroid receptor coactivator-3 is a pivotal target of gambogic acid in B-cell Non-Hodgkin lymphoma and an inducer of histone H3 deacetylation

“…Cell growth inhibition after GA treatment was examined with MTT assays, as previously described (Yi et al, 2015).…”