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  • Title: MEK inhibition induces caspases activation, differentiation blockade and PML/RARalpha degradation in acute promyelocytic leukaemia.
    Author: Barbarroja N, Siendones E, Torres LA, Luque MJ, Martinez JM, Dorado G, Velasco F, Torres A, López-Pedrera C.
    Journal: Br J Haematol; 2008 Jul; 142(1):27-35. PubMed ID: 18445086.
    Abstract:
    The hallmark of acute promyelocytic leukaemia (APL) is the reciprocal translocation t(15;17), which leads to the expression of the promyelocytic leukaemia/retinoic acid receptor alpha (PML/RARalpha) fusion protein and a cell differentiation blockade at the promyelocytic stage. PML/RARalpha is directly targeted by all-trans-retinoic acid (ATRA), which degrades the oncoprotein and induces complete remission of malignancies. The aberrant function of PML/RARalpha, together with the constitutive activation of the mitogen-activated protein/extracellular signal-regulated kinase (MEK/ERK) signalling pathway, regulates the ability of haematopoietic cells to proliferate, differentiate, and escape from apoptotic episodes. The role of the MEK/ERK pathway in PML/RARalpha expression, differentiation, proliferation and apoptosis in APL cells was analysed using specific MEK inhibitors. The blockade of MEK/ERK pathway resulted in caspase-dependent degradation of PML/RARalpha, and attenuation of the cell differentiation induction. To our knowledge, this is the first report to show that PML/RARalpha was suppressed by MEK/ERK inhibition, through a mechanism dependent on caspase activation. ATRA co-operated with MEK inhibitor to increase degradation of PML/RARalpha and exhibited a convergence point in caspase activation with MEK inhibitors. Taken together, our data suggest a new role of MEK/ERK pathway in the pathogenesis of APL, thus supporting the use of MEK/ERK inhibitors as an efficient therapeutic strategy for this haematological malignancy.
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