Adjuvant Epigenetic Therapy of Decitabine and Suberoylanilide Hydroxamic Acid Exerts Anti-Neoplastic Effects in Acute Myeloid Leukemia Cells

Abstract

Atypical epigenetic processes including histone acetylation and DNA methylation have been identified as a fundamental theme in hematologic malignancies. Such mechanisms modify gene expression and prompt, in part at least, the initiation and progression of several malignancies including acute myeloid leukemia. In the current study we determined the effects of treating KG-1 and U937 acute myeloid leukemia (AML) cells, in vitro, with the HDAC inhibitor, suberoylanilide hydroxamic acid (SAHA), or with a DNMT inhibitor, decitabine (DAC), or their combination, on cell proliferation, cell cycle progression, apoptosis, and expression of apoptosis-related proteins. Each of SAHA and DAC attenuated cell proliferation and induced cell cycle arrest and apoptotic cell death of KG-1 and U937 cell lines. Besides, their sequential combination improved the obtained anti-neoplastic effect: significant augmentation of growth inhibition and apoptosis induction as compared to cells treated with either drug alone. This effect was featured by the upregulated expression of Bax, cytochrome c1, p21, and cleaved caspases 8, 9, and 3, signifying the activation of both the intrinsic and extrinsic pathways of apoptosis. The sequential combination of SAHA and DAC causes a profound antitumorigenic effect in AML cell lines by inducing the expression of tumor suppressor genes. feature of malignancy. Promoter CpG island hypermethylation of tumor suppressor genes, as mediated by DNA methyltransferase enzymes (DNMTs), is well-reported to associate with a closed chromatin structure and potent transcriptional silencing that inactivates key cellular pathways like DNA damage repair and apoptosis [10,11].The two epigenetic mechanisms are functionally interdependent [12]. DNMTs with several DNA binding factors associate with HDACs to form corepressor complexes that alter chromatin architecture and, subsequently, the transcription of putative target genes [13,14]. Trichostatin A, a histone deacetylase inhibitor, induced DNA demethylation in human cancer cell lines [15], and the use of 5-azacytidine, a demethylating agent, mediated an increase in H4 acetylation [16], therefore providing evidence for an integrated crosstalk between the two epigenetic mechanisms.Dysregulated epigenetic mechanisms are central in the pathogenesis of acute myeloid leukemia (AML), the most common type of acute leukemia in adults with poor prognosis despite induction therapy [17][18][19]. Epigenetic shifts impair the differentiation of myeloid progenitors and promote their uncontrolled clonal proliferation leading to bone marrow failure [20].Unique DNA methylation profiles were reported in AML patient samples. Many genes were found to be differentially hypermethylated and repressed [21,22]. AML blasts also exhibited significant modifications in histone acetylation levels at more than 1000 genomic loci compared with progenitor cells with fundamental promoter regions being hypoacetylated in AML compared with progenitor cells [23].The major role of epigenetics in myeloid leukemogenesi...

Histone deacetylase inhibition by suberoylanilide hydroxamic acid: a therapeutic approach to treat human uterine leiomyoma

“…We found that treatment of HULP cells with SAHA decreased cell proliferation, as demonstrated by decreased PCNA protein expression. These findings suggest an antiproliferative effect of SAHA treatment on UL, as was previously described in other tumors (31)(32)(33). Additionally, the cell cycle regulatory genes CCND1 and C-MYC were down-regulated after SAHA treatment.…”

“…Suberoylanilide hydroxamic acid (SAHA), or vorinostat, is a competitive inhibitor of class I and class II HDAC (26) that is used as an anticancer drug to treat different types of tumors (27,28). One of the well-characterized biochemical effects of SAHA is increased accumulation of acetylated core histones caused by inhibition of HDAC activity (29,30), which blocks cell proliferation and tumor growth in hepatoid adenocarcinoma (31), myeloid leukemia (32), and prostate cancer (33).…”

Beta-Tocotrienol Exhibits More Cytotoxic Effects than Gamma-Tocotrienol on Breast Cancer Cells by Promoting Apoptosis via a P53-Independent PI3-Kinase Dependent Pathway

“…The pellet was resuspended in incubation buffer and stained with Annexin V and propidium iodide (PI) following the manufacturer's instruction (Annexin V-FITC Apoptosis Detection Kit; Abcam). Cells were then analyzed by flow cytometer using the BD Accuri C6 Plus Software as previously described [50,51]. Living cells are stained negative for both Annexin-V and PI.…”

8a, a New Acridine Antiproliferative and Pro-Apoptotic Agent Targeting HDAC1/DNMT1

“…Similarly, aberrant DNA methylation often silences the transcription of tumor-suppressor genes and is considered a hallmark of myeloid neoplasms [ 12 ]. The crosstalk between DNA methylation and histone modifications has been reported widely [ 13 ]. The combined clinical use of histone deacetylase inhibitors (HDACi) and a DNA methylation agent (HMA) enhances the efficacy [ 14 ].…”