ROLE OF GLUCOCORTICOID RECEPTOR IN MYELOID LEUKEMIA CELL DIFFERENTIATION INDUCED BY RETINOIC ACID

MICAELA SILBERMINS; ADALI PECCI; LUCIANA ROCHA VIEGAS

Bariloche

Simposio; Fourth South American Symposium in Signal Transduction and Molecular Medicine (SISTAM 2018); 2018

Leukemias are malignant diseases of hematopoietic cells with altered proliferation, differentiation and apoptosis balance. Synthetic glucocorticoids (glu) like dexametasone (Dex) are used in the treatment of hematopoietic diseases due to its pro-apoptotic properties. While, the differentiation inducer retinoic acid (RA) results not encouraging in most myeloid patients. Thus, we hypothesize that a combination of Dex and RA could represent an alternative and promising therapy. To this aim, we study the role of glu in RA-induced human promyelocytic leukemia cell differentiation. Undifferentiated NB4 cells were treated with RA in the presence or absence of Dex. Our results showed that over 72h Dex markedly enhances a RA-induced cell differentiation response observed both as the expression of the cell surface marker CD11c by flow cytometry and as the ability to reduce nitroblue tetrazolium by counting violet granulocytic cells. Given that RA receptor (RAR) and glucocorticoid receptor (GR) interact with common co-repressors and co-activators, we explored the possibility of an endogenous GR-RARα association. Indeed, co-immunoprecipitation experiments using nuclear lysates from NB4 cells treated over 24h revealed the existence of a novel endogenous complex containing both GR and RARα even in the absence of stimulus. This interaction is enhanced by RA and Dex combined treatment. Moreover, upon 48h the addition of Dex potentiates RA-induced effect on the expression of hoxA3, hoxA4, pscd4, hoxA13 and hoxD13 genes, monitored by RT-qPCR assays. Furthermore, in silico analysis of published ChIP-seqs, reveal regions in the hoxA cluster and in the pscd4 gene that bind both RARα and GR, albeit only studied under different conditions so far.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.