tretinoin and belinostat

Development of acute myeloid leukemia is usually sustained by deregulated epigenome. Alterations in DNA methylation and histone modifications are common manifestations of the disease. Acute promyelocytic leukemia (APL) is not an exception. Therefore, drugs that target epigenetic processes suggest an appealing strategy for APL treatment. In this study we tested the anti-leukemic activity of histone deacetylase inhibitor (HDACi) Belinostat (PXD101, (2E)-N-Hydroxy-3-[3-(phenylsulfamoyl)phenyl]prop-2-enamide), and histone methyltransferase inhibitor (HMTi) 3-Deazaneplanocin A (DZNep, 5R-(4-amino-1H-imidazo[4,5-c]pyridin-1-yl)-3-(hydroxymethyl)-3-cyclopentene-1S,2R-diol) combined with retinoic acid (RA) in APL cells NB4 and HL-60. We demonstrated that APL cell treatment with combinations of differentiation inductor RA, HDACi Belinostat and HMTi DZNep caused a depletion of leukemia cell growth and viability, initiated apoptosis and exaggerated RA induced granulocytic differentiation. Also an increased expression of transcription factors C/EBPε and PPARγ was demonstrated, while no significant reduction in C/EBPα gene level was detected. Furthermore, combined treatment depleted gene expression levels of EZH2 and SUZ12, especially in HL-60 cells, and diminished protein levels of Polycomb Repressive Complex 2 (PRC2) components EZH2, SUZ12 and EED. In addition, our study has shown that Belinostat and DZNep together with RA caused a depletion in HDAC1 and HDAC2 protein levels, HDAC2 gene expression and increased hyperacetylation of histone H4 in both leukemia cell lines. Using ChIP method we also demonstrated the increased association of hyperacetylated histone H4 with the C/EBPα and C/EBPε promoter regions in HL-60 cells. Summarizing, these findings indicate that combined treatment with RA, Belinostat and 3-Deazaneplanocin A is an effective epigenetic inducer for leukemia cell differentiation.

Topics: Acetylation; Adenosine; Apoptosis; CCAAT-Enhancer-Binding Protein-alpha; Cell Differentiation; Drug Interactions; Enhancer of Zeste Homolog 2 Protein; Gene Expression Regulation, Neoplastic; Histone Deacetylase Inhibitors; Histone Methyltransferases; Histone-Lysine N-Methyltransferase; Histones; HL-60 Cells; Humans; Hydroxamic Acids; Leukemia, Promyelocytic, Acute; Neoplasm Proteins; Polycomb Repressive Complex 2; Promoter Regions, Genetic; Sulfonamides; Transcription Factors; Tretinoin

Xenograft models are suitable for in vivo study of leukemia's pathogenesis and the preclinical development of anti-leukemia agents but understanding of epigenetic regulatory mechanisms linking to adult cell functions in pathological conditions during different in vivo treatments is yet unknown. In this study, for the first time epigenetic chromatin modifications were characterized in tissues and tumours from murine xenograft model generated using the human acute promyelocytic leukemia (APL) NB4 cells engrafted in immunodeficient NOG mice. Xenografts were subjected to combined epigenetic treatment by histone deacetylase inhibitor Belinostat, histone methyltransferase inhibitor 3-DZNeaplanocin A and all-trans-retinoic acid based on in vitro model, where such combination inhibited NB4 cell growth and enhanced retinoic acid-induced differentiation to granulocytes. Xenotransplantation was assessed by peripheral blood cells counts, the analysis of cell surface markers (CD15, CD33, CD45) and the expression of certain genes (PML-RAR alpha, CSF3, G-CSFR, WT1). The combined treatment prolonged APL xenograft mice survival and prevented tumour formation. The analysis of the expression of histone marks such as acetylation of H4, trimethylation of H3K4, H3K9 and H3K27 in APL xenograft mice tumours and tissues demonstrated tissue-specific changes in the level of histone modifications and the APL prognostic mark, WT1 protein. In summary, the effects of epigenetic agents used in this study were positive for leukemia prevention and linked to a modulation of the chromatin epigenetic environment in adult tissues of malignant organism.

Topics: Animals; Antineoplastic Agents; Antineoplastic Combined Chemotherapy Protocols; Brain; Cell Line, Tumor; Epigenesis, Genetic; Female; Histones; Humans; Hydroxamic Acids; Leukemia, Promyelocytic, Acute; Liver; Male; Mice; Organ Specificity; Protein Processing, Post-Translational; Sulfonamides; Tretinoin; WT1 Proteins; Xenograft Model Antitumor Assays

Epigenetic changes play a significant role in leukaemia pathogenesis, therefore histone deacetylases (HDACis) are widely accepted as an attractive strategy for acute promyelocytic leukaemia (APL) treatment. Belinostat (Bel, PXD101), a hydroxamate-type HDACi, has proved to be a promising cure in clinical trials for solid tumours and haematological malignancies. However, insight into molecular effects of Bel on APL, is still lacking. In this study, we investigated the effect of Bel alone and in combination with differentiation inducer retinoic acid (RA) on human promyelocytic leukaemia NB4 and HL-60 cells. We found that treatment with Bel, depending on the dosage used, inhibits cell proliferation, whereas in combination with RA enhances and accelerates granulocytic leukaemia cell differentiation. We also evaluated the effect of used treatments with Bel and RA on certain epigenetic modifiers (HDAC1, HDAC2, PCAF) as well as cell cycle regulators (p27) gene expression and protein level modulation. We showed that Bel in combination with RA up-regulates basal histone H4 hyperacetylation level more strongly compared to Bel or RA alone. Furthermore, chromatin immunoprecipitation assay indicated that Bel induces the accumulation of hyperacetylated histone H4 at the p27 promoter region. Mass spectrometry analysis revealed that in control NB4 cells, hyperacetylated histone H4 is mainly found in association with proteins involved in DNA replication and transcription, whereas after Bel treatment it is found with proteins implicated in pro-apoptotic processes, in defence against oxidative stress and tumour suppression. Summarizing, our study provides some novel insights into the molecular mechanisms of HDACi Bel action on APL cells.

Topics: Acetylation; Cell Cycle Checkpoints; Cell Differentiation; Cell Survival; Chromatin Assembly and Disassembly; Cyclin-Dependent Kinase Inhibitor p27; DNA Methylation; Gene Expression Regulation, Leukemic; Granulocytes; Histone Deacetylase Inhibitors; Histones; HL-60 Cells; Humans; Hydroxamic Acids; Leukemia, Promyelocytic, Acute; Molecular Sequence Data; Neoplasm Proteins; Promoter Regions, Genetic; Sulfonamides; Tretinoin

Therapeutic strategies targeting histone deacetylase (HDAC) inhibition have become promising in many human malignancies. Belinostat (PXD101) is a hydroxamate-type HDAC inhibitor tested in phase I and II clinical trials in solid tumors and hematological cancers. However, little is known about the use of belinostat for differentiation therapy against acute myelogenous leukemia. Here, we characterize the antileukemia activity of belinostat as a single drug and in combination with all-trans-retinoic acid (RA) in promyelocytic leukemia HL-60 and NB4 cells. Belinostat exerted dose-dependent growth-inhibitory or proapoptotic effects, promoting cell cycle arrest at the G0/G1 or the S transition. Apoptosis was accompanied by activation of caspase 3, degradation of PARP-1, and cell cycle-dependent changes in the expression of survivin, cyclin E1, and cyclin A2. Belinostat induced a dose-dependent reduction in the expression of EZH2 and SUZ12, HDAC-1, HDAC-2, and histone acetyltransferase PCAF (p300/CBP-associated factor). Belinostat increased acetylation of histone H4, H3 at K9 and H3 at K16 residues in a dose-dependent manner, but did not reduce trimethylation of H3 at K27 at proapoptotic doses. Combined treatment with belinostat and RA dose dependently accelerated and reinforced granulocytic differentiation, accompanied by changes in the expression of CD11b, C/EBPα (CCAAT/enhancer binding protein-α), and C/EBPε. Our results concluded the usefulness of belinostat, as an epigenetic drug, for antileukemia and differentiation therapy.

Topics: Acetylation; Antineoplastic Agents; Apoptosis; Apoptosis Regulatory Proteins; Cell Cycle Checkpoints; Cell Differentiation; Cell Line, Tumor; Cell Proliferation; Drug Synergism; Enhancer of Zeste Homolog 2 Protein; Epigenesis, Genetic; Granulocytes; Histone Deacetylase Inhibitors; Histone Deacetylases; Histones; Humans; Hydroxamic Acids; Leukemia, Promyelocytic, Acute; Neoplasm Proteins; Polycomb Repressive Complex 2; Sulfonamides; Transcription Factors; Tretinoin