RESUMEN
BACKGROUND: 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. DESIGN AND METHODS: 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. RESULTS: 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 ß via diminished phosphorylation and, ultimately, inactivation of ß-catenin by phosphorylation. CONCLUSIONS: 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 ß/ß-catenin pathway is a target for inhibition of nicotinamide phosphoribosyltransferase or sirtuin 2 and, thereby, leukemia cell proliferation.
Asunto(s)
Leucemia Mieloide/enzimología , Nicotinamida Fosforribosiltransferasa/metabolismo , Sirtuina 2/metabolismo , Acrilamidas/farmacología , Apoptosis/efectos de los fármacos , Benzotiazoles/farmacología , Crisis Blástica/enzimología , Crisis Blástica/genética , Línea Celular Tumoral , Proliferación Celular/efectos de los fármacos , Supervivencia Celular/efectos de los fármacos , Activación Enzimática/efectos de los fármacos , Inhibidores Enzimáticos/farmacología , Regulación Leucémica de la Expresión Génica , Glucógeno Sintasa Quinasa 3/metabolismo , Glucógeno Sintasa Quinasa 3 beta , Humanos , Leucemia Mieloide/genética , Modelos Biológicos , Nicotinamida Fosforribosiltransferasa/antagonistas & inhibidores , Piperidinas/farmacología , Proteínas Proto-Oncogénicas c-akt/antagonistas & inhibidores , Proteínas Proto-Oncogénicas c-akt/metabolismo , ARN Mensajero/genética , ARN Mensajero/metabolismo , Transducción de Señal , Sirtuina 2/antagonistas & inhibidores , Sirtuina 2/genética , beta Catenina/antagonistas & inhibidores , beta Catenina/metabolismoRESUMEN
We found that hematopoietic cell-specific Lyn substrate 1 (HCLS1 or HS1) is highly expressed in human myeloid cells and that stimulation with granulocyte colony-stimulating factor (G-CSF) leads to HCLS1 phosphorylation. HCLS1 binds the transcription factor lymphoid-enhancer binding factor 1 (LEF-1), transporting LEF-1 into the nucleus upon G-CSF stimulation and inducing LEF-1 autoregulation. In patients with severe congenital neutropenia, inherited mutations in the gene encoding HCLS1-associated protein X-1 (HAX1) lead to profound defects in G-CSF-triggered phosphorylation of HCLS1 and subsequently to reduced autoregulation and expression of LEF-1. Consistent with these results, HCLS1-deficient mice are neutropenic. In bone marrow biopsies of the majority of tested patients with acute myeloid leukemia, HCLS1 protein expression is substantially elevated, associated with high levels of G-CSF synthesis and, in some individuals, a four-residue insertion in a proline-rich region of HCLS1 protein known to accelerate intracellular signaling. These data demonstrate the importance of HCLS1 in myelopoiesis in vitro and in vivo.