fk-866 and Leukemia--Myeloid

FK866 is a specific inhibitor of NAMPT and induces apoptosis of leukemic cells by depletion of intracellular NAD(+). Since up-regulation of NAMPT is associated with several cases of cancers, including leukemias, we asked whether in leukemic cells inhibition of NAMPT involves p53 pathway. We observed that FK866 induced apoptosis and reduced cell proliferation in NB-4, OCI-AML3 and MOLM-13 cell lines. In contrast, the leukemia cell lines, K-562 and Kasumi, containing nonfunctional p53 were relatively unaffected by FK866 treatment. Importantly, direct inhibition of sirtuins significantly reduced the viability of NB-4, OCI-AML3 and MOLM-13 cell lines. Activation of p53 by FK866 involved increased acetylation of p53 at lysine 382 with subsequent increase in the expression of p21 and BAX. Further, knockdown of p53 attenuated the effects of FK866 on apoptosis and cell cycle arrest, which was partly associated with decreased expression of p21 and BAX. Our results suggest the role of p53 acetylation pathway in the anti-leukemic effect of FK866.

Topics: Acetylation; Acrylamides; Apoptosis; bcl-2-Associated X Protein; Cell Line, Tumor; Cell Proliferation; Cyclin-Dependent Kinase Inhibitor p21; Cytokines; Gene Knockout Techniques; Humans; Leukemia, Myeloid; NAD; Nicotinamide Phosphoribosyltransferase; Piperidines; Sirtuins; Tumor Suppressor Protein p53; Up-Regulation

Inhibitors of nicotinamide phosphoribosyltransferase have recently been validated as therapeutic targets in leukemia, but the mechanism of leukemogenic transformation downstream of this enzyme is unclear.. Here, we evaluated whether nicotinamide phosphoribosyltransferase's effects on aberrant proliferation and survival of myeloid leukemic cells are dependent on sirtuin and delineated the downstream signaling pathways operating during this process.. We identified significant upregulation of sirtuin 2 and nicotinamide phosphoribosyltransferase levels in primary acute myeloid leukemia blasts compared to in hematopoietic progenitor cells from healthy individuals. Importantly, specific inhibition of nicotinamide phosphoribosyltransferase or sirtuin 2 significantly reduced proliferation and induced apoptosis in human acute myeloid leukemia cell lines and primary blasts. Intriguingly, we found that protein kinase B/AKT could be deacetylated by nicotinamide phosphoribosyltransferase and sirtuin 2. The anti-leukemic effects of the inhibition of nicotinamide phosphoribosyltransferase or sirtuin 2 were accompanied by acetylation of protein kinase B/AKT with subsequent inhibition by dephosphorylation. This leads to activation of glycogen synthase kinase-3 β via diminished phosphorylation and, ultimately, inactivation of β-catenin by phosphorylation.. Our results provide strong evidence that nicotinamide phosphoribosyltransferase and sirtuin 2 participate in the aberrant proliferation and survival of leukemic cells, and suggest that the protein kinase B/AKT/ glycogen synthase kinase-3 β/β-catenin pathway is a target for inhibition of nicotinamide phosphoribosyltransferase or sirtuin 2 and, thereby, leukemia cell proliferation.

Topics: Acrylamides; Apoptosis; Benzothiazoles; beta Catenin; Blast Crisis; Cell Line, Tumor; Cell Proliferation; Cell Survival; Enzyme Activation; Enzyme Inhibitors; Gene Expression Regulation, Leukemic; Glycogen Synthase Kinase 3; Glycogen Synthase Kinase 3 beta; Humans; Leukemia, Myeloid; Models, Biological; Nicotinamide Phosphoribosyltransferase; Piperidines; Proto-Oncogene Proteins c-akt; RNA, Messenger; Signal Transduction; Sirtuin 2