Panobinostat treatment depletes EZH2 and DNMT1 levels and enhances decitabine mediated de-repression of JunB and loss of survival of human acute leukemia cells

Abstract

The PRC2 complex protein EZH2 is a histone methyltransferase that is known to bind and recruit DNMT1 to the DNA to modulate DNA methylation. Here, we determined that the pan-HDAC inhibitor panobinostat (LBH589) treatment depletes DNMT1 and EZH2 protein levels, disrupts the interaction of DNMT1 with EZH2, as well as de-represses JunB in human acute leukemia cells. Similar to treatment with the hsp90 inhibitor 17-DMAG, treatment with panobinostat also inhibited the chaperone association of heat shock protein 90 with DNMT1 and EZH2, which promoted the proteasomal degradation of DNMT1 and EZH2. Unlike treatment with the DNA methyltransferase inhibitor decitabine, which demethylates JunB promoter DNA, panobinostat treatment mediated chromatin alterations in the JunB promoter. Combined treatment with panobinostat and decitabine caused greater attenuation of DNMT1 and EZH2 levels than either agent alone, which was accompanied by more JunB de-repression and loss of clonogenic survival of K562 cells. Co-treatment with panobinostat and decitabine also caused more loss of viability of primary AML but not normal CD34+ bone marrow progenitor cells. Collectively, these findings indicate that co-treatment with panobinostat and decitabine targets multiple epigenetic mechanisms to de-repress JunB and exerts antileukemia activity against human acute myeloid leukemia cells.

Treatment with Panobinostat Induces Glucose-Regulated Protein 78 Acetylation and Endoplasmic Reticulum Stress in Breast Cancer Cells

“…Western blot analyses of GRP78, p-eIF2α, eIF2α, ATF4, CHOP, HDAC6, and β-actin were done using specific antibodies, as described previously (23,29,30). The expression of β-actin was used as a loading control.…”

“…The expression of β-actin was used as a loading control. Immunoprecipitation of HDAC6, endogenous GRP78, and FLAG-tagged GRP78 were carried out using specificantibodies as previously described and immunoblotted with anti-GRP78, HDAC6, PERK, or anti-acetyl lysine antibody (30). Class-specific IgG was used as a control in immunoprecipitations.…”

“…Reverse transcription was done with 2 μg of RNA using Supercript RT (Invitrogen). PCR reactions were done using the listed specific primers using 2× Supermix IQ (Bio-Rad) reagent, as previously described (30 …”

Deacetylase inhibitors modulate proliferation and self-renewal properties of leukemic stem and progenitor cells

“…DACi additionally induce selective proteasomal degradation of histone decetylase 2 (HDAC2), DNA methyltransferases and other proteins responsible for aberrant gene repression and signaling. [4][5][6] This effect equally alters the cellular program, but to date, the underlying mechanisms remain elusive and have not yet been studied in the leukemic stem and progenitor compartment.…”

Increased expression of amyloid precursor protein promotes proliferation and migration of AML1/ETO-positive leukemia cells and be inhibited by panobinostat

“…As for the important role of overexpression of APP in various of human malignancies, finding drugs that inhibiting expression levels of APP could have important implications for cancer therapy. The panhistone deaetylase inhibitors panobinostat (PS, also known as LBH589) is a novel HDACi that inhibits multiple HDAC classes, exerting potent anti-cancer effects in hematological malignancies [14][15][16][17], which aroused to be focused on deplete expression levels of APP.…”