CONICET | Buscador de Institutos y Recursos Humanos

The leukemias are malignant diseases of hematopoietic cells in which the proper balance between proliferation, differentiation and apoptosis is no longer operative. Synthetic glucocorticoids like dexametasone (Dex) are frequently used in the treatment of hematopoietic diseases due to its pro-apoptotic properties. On the other hand, in many clinical trials the differentiation inducer retinoic acid (RA) resulted not encouraging in most myeloid patients. In this sense, our hypothesis suggests that a combination of steroid hormones and RA could represent an alternative and promising therapy. The main goal of this project is to study the role of glucocorticoids in RA-induced human promyelocytic leukemia cell differentiation. Undifferentiated NB4 cells were treated with RA in the presence or absence of Dex over 72h. Our results showed that Dex markedly enhances a RA-induced cell differentiation response, observed as a potentiated expression of the cell surface marker CD11c by flow cytometry analysis (control: (0±1)% RA: (19±2)% RA+Dex: (54±3)% - p≤0.01). To gain functional insights into this differentiation process, the expression of hox genes, pscd4, meis2, gr and rarβ was monitored in RT-qPCR assays. Notably, upon 48h, the addition of Dex potentiates RA-induced expression of hoxA3 (control: (0.4±0.1) a.u. RA: (1.0±0.0) a.u. RA+Dex: (1.5±0.3) a.u - p≤0.02) and pscd4 (control: (0.3±0.2) a.u. RA: (1.0±0.0) a.u. RA+Dex: (1.6±0.1) a.u - p≤0.01) genes. Finally, PML-RARα and RARα protein down-regulation upon RA stimulation was confirmed by western blot, and remained unchanged upon combined treatment with Dex. Moreover, reduced levels of GR protein upon RA and Dex co-stimulation were also observed. Overall, our data reveals the existence of a synergistic effect of Dex and RA on NB4 cell differentiation. Further characterization of this molecular context could aid to identify attractive targets for therapeutic strategies in myeloid leukemia

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