PML/RARA inhibits expression of HSP90 and its target AKT.

Essential for cell survival, the 90 kD Heat Shock Proteins (HSP90) are molecular chaperons required for conformational stabilization and trafficking of numerous client proteins. Functional HSP90 is required for the stability of AKT, a serine-threonine kinase phosphorylated in response to growth factor stimulation. AKT plays a crucial regulatory role in differentiation, cell cycle, transcription, translation, metabolism and apoptosis.

PML/RARa inhibits PTEN expression in hematopoietic cells by competing with PU.1 transcriptional activity.

Acute promyelocitic leukemia (APL) is characterized by the pathognomonic presence in leukemic blasts of the hybrid protein PML/RARA, that acts as a transcriptional repressor impairing the expression of genes that are critical to myeloid differentiation. Here, we show that primary blasts from APL patients express lower levels of the oncosuppressor protein PTEN, as compared to blast cells from other AML subtypes or normal bone marrow, and demonstrate that PML-RARA directly inhibits PTEN expression. We show that All-Trans Retinoic Acid (ATRA) triggers in APL cells an active chromatin status at the core regulatory region of the PTEN promoter, that allows the binding of the myeloid-regulating transcription factor PU.

Analysis of mutational status, SNP rs16754, and expression levels of Wilms tumor 1 (WT1) gene in acute promyelocytic leukemia.

Overexpression, polymorphisms, and mutations of the WT1 gene have been reported in several human tumors including acute myeloid leukemia (AML) and variably correlated with prognosis. Acute promyelocytic leukemia (APL) represents the AML subset disclosing higher WT1 expression levels; however, no WT1 studies specifically focused on APL have been conducted. We screened for the presence of mutations, SNP rs16754, and expression levels of WT1 gene in 103 adult patients with newly diagnosed APL.