RESUMEN
BRIT1 (BRCT-repeat inhibitor of hTERT expression), also known as microcephalin (MCPH1), is a crucial gene in the complex cellular machine that is devoted to DNA repair and acts as a regulator of both the intra-S and G2/M checkpoints. The most important role of BRIT1/MCPH1 in the regulation of cell cycle progression appears to be the G2/M checkpoint. The K562 and peripheral blood cells of chronic myeloid leukemia (CML) patients at diagnosis were found to downregulate BRIT1/MCPH1. However, we could not find any correlation between bcr/abl activity and the BRIT1/MCPH1 level. In order to study the genomic instability of CML cells, we evaluated the ability of these cells to arrest mitotic division after exposure to hydroxyurea, a known genotoxic agent. We showed that CML cells continue to proliferate without the activation of the G2/M cell cycle checkpoint arrest or of the apoptotic mechanism. This behavior may predispose the cells to accumulate genomic defects. In conclusion, we found that CML cells have a low BRIT1/MCPH1 level and show a defective G2/M arrest, confirming that these cells have a constitutive genomic instability.
Asunto(s)
Puntos de Control de la Fase G2 del Ciclo Celular , Leucemia Mielógena Crónica BCR-ABL Positiva/metabolismo , Proteínas de Neoplasias/metabolismo , Proteínas del Tejido Nervioso/metabolismo , Actinas/antagonistas & inhibidores , Adulto , Anciano , Proteínas de Ciclo Celular , Proliferación Celular/efectos de los fármacos , Células Cultivadas , Citocalasina B/toxicidad , Citocinesis/efectos de los fármacos , Proteínas del Citoesqueleto , Femenino , Puntos de Control de la Fase G2 del Ciclo Celular/efectos de los fármacos , Regulación Neoplásica de la Expresión Génica , Inestabilidad Genómica , Humanos , Hidroxiurea/antagonistas & inhibidores , Hidroxiurea/toxicidad , Células K562 , Leucemia Mielógena Crónica BCR-ABL Positiva/sangre , Leucocitos/efectos de los fármacos , Leucocitos/metabolismo , Masculino , Persona de Mediana Edad , Mutágenos/toxicidad , Proteínas de Neoplasias/genética , Proteínas del Tejido Nervioso/genética , ARN Mensajero/metabolismoRESUMEN
To understand neutrophil impairment in the progression from MGUS through active MM, we investigated the function of mature, high-density neutrophils (HDNs), isolated from peripheral blood. In 7 MM, 3 MGUS and 3 healthy subjects by gene expression profile, we identified a total of 551 upregulated and 343 downregulated genes in MM-HDN, involved in chemokine signaling pathway and FC-gamma receptor mediated phagocytosis conveying in the activation of STAT proteins. In a series of 60 newly diagnosed MM and 30 MGUS patients, by flow-cytometry we found that HDN from MM, and to a lesser extend MGUS, had an up-regulation of the inducible FcγRI (also known as CD64) and a down-regulation of the constitutive FcγRIIIa (also known as CD16) together with a reduced phagocytic activity and oxidative burst, associated to increased immune-suppression that could be reverted by arginase inhibitors in co-culture with lymphocytes. In 43 consecutive newly-diagnosed MM patients, who received first-line treatment based on bortezomib, thalidomide and dexamethasone, high CD64 could identify at diagnosis patients with inferior median overall survival (39.5 versus 86.7 months, p = 0.04). Thus, HDNs are significantly different among healthy, MGUS and MM subjects. In both MGUS and MM neutrophils may play a role in supporting both the increased susceptibility to infection and the immunological dysfunction that leads to tumor progression.