In vitro cytotoxic and biochemical effects of 5-aza-2'-deoxycytidine.

The in vitro effect of 5-aza-2'-deoxycytidine (5-aza-CdR) on cytotoxicity and macromolecular synthesis in A(T1)C1-3 hamster fibrosarcoma cells was investigated. The in vitro concentrations that produce 50% cell kill for 5-aza-CdR were about 1.0 and 0.01 microng/ml for a 2- and 24-hr exposure, respectively. 5-aza-CdR inhibited the growth of the fibrosarcoma cells by 40% at a concentration of 0.05 microng/ml. Deoxycytidine, but not cytidine, was a potent antagonist of the cytotoxicity produced by 5-aza-CdR. At cytotoxic concentrations 5-aza-CdR did not appear to inhibit DNA, RNA, or protein synthesis during a 1-hr incubation as measured by the incorporation of radioactive thymidine, uridine,, or leucine into acid-insoluble material. At a concentration of 10 microng/ml, 5-aza-CdR stimulated the incorporation of radioactive thymidine into DNA by more than 50%. These results indicate that 5-aza-CdR is a very potent cytotoxic agent to tumor cells in vitro at concentrations that do not inhibit macromolecular synthesis.     

Methylation status of genes upregulated by demethylating agent 5-aza-2'-deoxycytidine in hepatocellular carcinoma

BACKGROUND/AIMS: To determine the clinical significance of gene promoter methylation in hepatocellular carcinoma (HCC), we examined in clinical samples the methylation status of those promoters that showed elevated activity in hepatoma cell lines after 5-aza-2'-deoxycytidine treatment. METHODS: Regarding the genes with promoter hypermethylation in the cell lines, their expression levels and methylation status in HCC and non-HCC tissues were assessed by semiquantitive RT-PCR and methylation-specific PCR. To confirm the result, the expression levels and methylation status in 16 additional HCC and non-HCC tissues were assessed. RESULTS: The promoter regions of caveolin 1 (CAV1), cysteine and glycine-rich protein 1 (CSRP1), Kruppel-like factor 6 (KLF6), myosin (light polypeptide 9) (MYL9), and transgelin (TAGLN) were highly methylated in the cell lines. CAV1 and CSRP1 were methylated in HCC more frequently than in non-HCC. KLF6, MYL9, and TAGLN were fully methylated in both HCC and non-HCC. Using additional clinical samples, downregulation of CAV1 and CSRP1 was observed in 38 and 56%, respectively, of the 16 HCC samples and aberrant methylation of CAV1 and CSRP1 was observed in 56% of HCC in both cases. CONCLUSION: CAV1 and CSRP1 were inactivated in HCC by aberrant methylation and they may serve as important biomarkers of malignancy.     

Effects of the alpha-D-anomer of 5-aza-2'-deoxycytidine on L1210 mouse leukemic cells in vitro and in vivo

The alpha-D-anomer of 5-aza-2'-deoxycytidine inhibited cell growth in vitro in L1210 mouse leukemic cells (concentration causing 50% inhibition about 1 X 10(-6) M) and was also active in vivo in increasing the life span of mice with L1210 leukemia by 100% after a single i.p. injection (800 to 1000 mg/kg). This effect could be reversed by 2'-deoxycytidine. The alpha-D-anomer produced approximately 100-fold less host toxicity than did 5-aza-2'-deoxycytidine. It was observed that alpha-D-anomer, when kept at 23 degrees for 72 hr, inhibited the uptake of radioactive 2'-deoxycytidine by L1210 cells in vitro as well as the phosphorylation of 2'-deoxycytidine by a cell-free extract from L1210 cells. These effects could not be obtained with the fresh solution of the drug. It is proposed that the action of alpha-D-anomer is due to its conversion to 5-aza-2'-deoxycytidine as shown by high-performance liquid chromatography performed on water solutions of both anomers.     

5-氮-2′-脱氧胞苷对人卵巢癌细胞凋亡及DNA错配修复基因表达的影响

目的:观察5-氮-2′-脱氧胞苷(5-aza-2′-deoxycytidine,又称5-aza-CdR)对卵巢癌细胞SKOV3和3AO增殖凋亡及DNA错配基因hMLH1和hMLH2表达的影响。方法:以特异性甲基转移酶抑制剂5-aza-CdR0.5、5、50μmol/L处理人卵巢癌细胞SKOV3和3AO3d,继续常规培养7d后,采用MTT比色法观察细胞经药物处理前后的增殖活性,用流式细胞术分析5-aza-CdR对细胞凋亡影响,以半定量逆转录-聚合酶链反应(RT-PCR)检测细胞经5-aza-CdR处理前后DNA错配修复基因hMLH1和hMSH2mRNA表达水平的改变。结果:人卵巢癌细胞SKOV3和3AO经5-aza-CdR处理后,与对照组比较,0.5、5、50μmol/L均能明显抑制肿瘤细胞生长,随着5-aza-CdR浓度增加,细胞增殖速度下降。SKOV3经5-aza-CdR0.5、5、50μmol/L处理后细胞的凋亡率分别为(10.59±1.57)%、(17.52±1.72)%、(34.10±1.45)%,3A0经0.5、5、50μmol/L5-aza-CdR处理后细胞的凋亡率分别为(11.11±2.21)%、(17.24±1.11)%、(26.53±2.00)%,与对照组相比均有统计学意义(P<0.01);且凋亡率与剂量成正相关(FSKOV3=227.6,PSKOV3<0.01;F3AO=108.4,P3AO<0.01)。经5-aza-CdR处理后的两株卵巢癌细胞中hMLH1和hMLH2的mRNA表达量有不同程度的增加(P<0.01),且与药物存在剂量依赖性。结论:在人卵巢癌细胞株SKOV3和3AO中,5-aza-CdR可部分逆转hMLH1和hMLH2的失活,恢复其生长调控功能,抑制肿瘤细胞生长,并诱导细胞凋亡。     

Aberrant gene expression in human non small cell lung carcinoma cells exposed to demethylating agent 5-aza-2'-deoxycytidine

The identification of genes undergoing genetic or epigenetic alterations and contributing to the development of cancer is critical to our understanding of the molecular mechanisms of carcinogenesis. A new approach in identifying alterations of genes that might be relevant to the process of tumor development was used in this study by examining the gene expression profile in human lung cancer cells exposed to 5-aza-2'-deoxycytidine (5-aza-dC). A cDNA array analysis was carried out on 5-aza-dC-treated and untreated non small cell lung cancer (NSCLC) cell line NCI-H522. Sixteen and 14 genes were upregulated and downregulated, respectively, by 5-aza-dC treatment. Among them, downregulation of tyrosine protein kinase ABL2 (ABL2) gene and upregulation of hint/protein kinase C inhibitor 1 (Hint/PKCI-1), DVL1, TIMP-1, and TRP-1 genes were found in expanded observations in two or three of five 5-aza-dC-treated NSCLC cell lines. Among these genes, we found that cDNA transfer of Hint/PKCI-1 resulted in a significant in vitro growth inhibition in two cell lines exhibiting 5-aza-dC-induced upregulation of Hint/PKCI-1 and significantly reduced in vivo tumorigenicity of one NSCLC cell line. Hint/PKCI-1, which is the only other characterized human histidine triad (HIT) nucleotide-binding protein in addition to tumor-suppressor gene FHIT, might be involved in lung carcinogenesis.     

5-aza-2'-deoxycytidine upregulates caspase-9 expression cooperating with p53-induced apoptosis in human lung cancer cells

Treating lung cancer cell lines using low-dose 5-aza-2'-deoxycytidine (DAC) caused an accumulation of procaspase-9 through mRNA upregulation, but the cells did not undergo apoptosis. However, when cells were treated with DAC and infected with a low dose of a recombinant wild-type p53 adenovirus vector (Ad-p53), a synergistic growth inhibitory effect was observed. Combination treatment induced Apaf-1 and procaspase-9 expression in which cytochrome c releases by Ad-p53 triggered the mitochondrial pathway of apoptosis. Selective blockage of caspase-9 activities by Z-LEHD-FMK completely attenuated DAC-induced enhancement of apoptosis mediated by Ad-p53 infection, and ectopic overexpression of procaspase-9 sensitized cells to Ad-p53-induced apoptosis in p53-null cells. In addition, DAC sensitized lung cancer cells to cisplatin and paclitaxel. Induction of the mitochondrial pathway of apoptosis using a slightly toxic dose of DAC may therefore be a strategy for treating lung cancer, and DAC treatment may have clinical implications when combined with chemotherapy or apoptosis-inducing gene therapy.     

The DNA demethylating agent 5-aza-2'-deoxycytidine activates NY-ESO-1 antigenicity in orthotopic human glioma

Cancer/testis antigens (CTAs) are considered to be suitable targets for the immunotherapy of human malignancies. It has been demonstrated that in a variety of tumors, the expression of certain CTAs is activated via the demethylation of their promoter CpG islands. In our study, we have shown that while the composite expression of 13 CTAs in 30 human glioma specimens and newly established cell lines from the Japanese population was nearly imperceptible, the DNA-demethylating agent 5-aza-2'-deoxycytidine (5-aza-CdR) markedly reactivated CTA expression in glioma cells but not in normal human cells. We quantified the diminished methylation status of NY-ESO-1-one of the most immunogenic CTAs-following 5-aza-CdR treatment by using a novel Pyrosequencing technology and methylation-specific PCR. Microarray analysis revealed that 5-aza-CdR is capable of signaling the immune system, particularly, human leukocyte antigen (HLA) class I upregulation. (51)Cr-release cytotoxicity assays and cold target inhibition assays using NY-ESO-1-specific cytotoxic T lymphocyte (CTL) lines demonstrated the presentation of de novo NY-ESO-1 antigenic peptides on the cell surfaces. In an orthotopic xenograft model, the systemic administration of 5-aza-CdR resulted in a significant volume reduction of the transplanted tumors and prolonged the survival of the animals after the adoptive transfer of NY-ESO-1-specific CTLs. These results suggested that 5-aza-CdR induces the expression of epigenetically silenced CTAs in poorly immunogenic gliomas and thereby presents a new strategy for tumor immunotherapy targeting 5-aza-CdR-induced CTAs.     

Delivery of 5-aza-2'-deoxycytidine to cells using oligodeoxynucleotides

The major goal of epigenetic therapy is to reverse aberrant promoter hypermethylation and restore normal function of tumor suppressor genes by the use of chromatin-modifying drugs. Decitabine, or 5-aza-2'-deoxycytidine (5-aza-CdR), is a well-characterized drug that is now Food and Drug Administration approved for the treatment of myelodysplastic syndrome. Although 5-aza-CdR is an extremely potent inhibitor of DNA methylation, it is subject to degradation by hydrolytic cleavage and deamination by cytidine deaminase. We show that short oligonucleotides containing a 5-aza-CdR can also inhibit DNA methylation in cancer cells at concentrations comparable with 5-aza-CdR. Detailed studies with S110, a dinucleotide, showed that it works via a mechanism similar to that of 5-aza-CdR after incorporation of its aza-moiety into DNA. Stability of the triazine ring in aqueous solution was not improved in the S110 dinucleotide; however, deamination by cytidine deaminase was dramatically decreased. This is the first demonstration of the use of short oligonucleotides to provide effective delivery and cellular uptake of a nucleotide drug and protection from enzymatic degradation. This approach may pave the way for more stable and potent inhibitors of DNA methylation as well as provide means for improving existing therapeutics.     

5-aza-2'-deoxycytidine sensitizes hepatoma and pancreatic cancer cell lines

Hepatocellular carcinoma (HCC) and pancreatic cancer are at the forefront of chemotherapy-resistant tumors with poor prognosis. Even with innovative treatment regimens, response rates remain low and the duration of response is short. We examined whether the suppression of DNA methylation was capable of enhancing the sensitivity of hepatoma and pancreatic cancer cell lines to 5-fluorouracil (5-FU). 5-aza-2'-deoxycytidine (5-aza-dC) at 2 microM, a specific DNA methylation inhibitor, did not induce cell death in Huh-7 with or without HCV, HLE, HepG2 and MIA PaCa-2 cells. However, a combination of 5-aza-dC with 5-FU showed a reduction in cell viability and induction of apoptosis in these cell lines to a greater degree than with 5-FU only. These findings underline the fact that DNA methylation plays a key role in conferring chemoresistance to hepatoma and pancreatic cancer, and the combination of DNA methylation inhibitor with chemotherapy could be a novel and highly effective tool for future targeted therapy of chemoresistant tumors.     

Induction of MAGE Genes in Lymphoid Cells by the Demethylating Agent 5-Aza-2'-deoxycytidine

MAGE genes encoding tumor antigens recognized by cytotoxic T lymphocytes are appropriate target molecules for specific immunotherapy of cancer. We have investigated whether the demethylating agent 5-aza-2'-deoxycytidine (DAC) induces MAGE-1, -2, -3 , and - 6 in normal and malignant lymphoid cells. DAC induced these MAGE genes in both PHA/interleukin-2 (IL-2)-activated T cells from healthy donors and MAGE -negative T and B cell leukemias in most cases. It also induced MAGE-1 in IL-2-dependent T cell clones and all MAGE genes tested in Epstein-Barr virus-transformed B cell lines. Expression of MAGE-1 protein in the cells was confirmed by western blot analysis with anti-MAGE-1 polyclonal antibody. Therefore, demethylation is a potent stimulus to induce MAGE genes in both normal and malignant lymphoid cells.     

5-氮杂脱氧胞苷增强苯丁酸钠对Kasumi-1细胞的诱导分化和凋亡作用

目的 探讨组蛋白脱乙酰化酶抑制剂苯丁酸钠(PB)联合DNA甲基化抑制剂5-氮杂脱氧胞苷(5-Aza-CdR)阻断AML1-ETO的生物学功能．消除AML1-ETO的转录抑制,诱导t(8;21)急性髓系白血病细胞系Kasumi-1细胞的分化和凋亡作用。方法 应用四甲基偶氮唑蓝(MTT)比色法观察PB单药或联合5-Aza-CdR对细胞生长的抑制作用;流式细胞术分析细胞周期和检测髓系分化抗原CD11b和CD13的表达,判断细胞分化;Annexin V和碘化丙啶(PI)双标记,经流式细胞术分析细胞早期凋亡。结果 (1)5-Aza-CdR可增强PB对Kasumi-1细胞的生长抑制作用,半数抑制浓度(IC50)下降为1．95mmol/L。(2)PB处理使Kasumi-1细胞阻滞于G0／G1期,5-Aza-CdR与PB联合则使细胞阻滞于G2／M期。(3)低剂量5-Aza-CdR增强PB诱导：Kasumi-1细胞髓系分化抗原CD11b和CD13的表达。(4)低剂量5-Aza-CAR不能增强PB诱导的Kasumi-1细胞凋亡,而高剂量5-Aza-CdR增强PB诱导的Kasumi-1细胞早期凋亡。结论 DNA甲基化抑制剂5-Aza-CdR增强脱乙酰化酶抑制剂PB抑制Kasumi-1细胞生长、诱导分化和凋亡的作用。     

5-氮-2'-脱氧胞苷抗肿瘤作用的研究进展

5-氮-2'-脱氧胞苷可通过DNA去甲基化影响组蛋白修饰包括组蛋白甲基化和乙酰化及直接引起DNA损伤等作用使调控细胞生长、分化和DNA修复有关的基因表达发生变化,引起肿瘤细胞周期阻滞、凋亡和分化从而抑制多种肿瘤细胞的生长,从而达到抗肿瘤作用.     

The absence of p53 is critical for the induction of apoptosis by 5-aza-2'-deoxycytidine

The absence of functional p53 has complex consequences on the cellular responses to cytotoxic drugs. Here, we have examined the role of p53 in the response to 5-aza-2'-deoxycytidine (5-aza-dC or decitabine). Primary mouse embryonic fibroblasts deficient for p53 undergo apoptosis after treatment with 5-aza-dC. When compared with other demethylating drugs or chemotherapeutic treatments, 5-aza-dC showed the highest selectivity ratio for triggering apoptosis in p53-deficient cells relative to wild-type cells. Moreover, the apoptotic efficacy of 5-aza-dC is proprietary of p53-deficient cells, not being observed in cells lacking other cell-cycle regulators, such as p19ARF, p16INK4a, p21(CIP1/WAF1), E2F-1, or E2F-2. Interestingly, treatment with 5-aza-dC results in the same degree of global genomic hypomethylation in wild-type and p53-null cells. However, wild-type cells activate p53 and arrest at G2/M, whereas p53-null cells accumulate severe chromosomal aberrations and undergo apoptosis. Significantly, the impact of p53-deficiency on the response to 5-aza-dC is not exclusive of primary non-neoplastic cells, but it is also present in neoplastically transformed cells. Finally, treatment of mice bearing genetically defined tumors with nontoxic doses of 5-aza-dC results in therapeutical responses only on tumors lacking p53, but not on tumors lacking p19ARF. Together, our results put forward the hypothesis that the absence of p53 may determine a higher chemotherapeutic index for 5-aza-dC.     

Epigenetic therapy of cancer with 5-aza-2'-deoxycytidine (decitabine)

Epigenetic events, such as aberrant DNA methylation, have been demonstrated to silence the expression of many genes that suppress malignancy. Since the event is reversible, it is an interesting target for intervention with specific inhibitors of DNA methylation, such as 5-aza-2'-deoxycytidine (5-AZA-CdR, decitabine). 5-AZA-CdR is a prodrug that requires activation via phosphorylation by deoxcytidine kinase. The nucleotide analog is incorporated into DNA, where it produces an irreversible inactivation of DNA methyltransferase. 5-AZA-CdR is an S-phase-specific agent. The demethylation of DNA by this analog in neoplastic cells can lead to the reactivation of silent tumor-suppressor genes, induction of differentiation or senescence, growth inhibition, and loss of clonogenicity. 5-AZA-CdR was demonstrated to be a potent antineoplastic agent against leukemia and tumors in animal models. Preliminary clinical trials of 5-AZA-CdR using different dose-schedules have shown interesting antineoplastic activity in patients with leukemia, myelodysplastic syndrome (MDS), and non-small cell lung cancer (NSCLC). Pharmacokinetic studies have shown that 5-AZA-CdR has a short in vivo half-life of 15 to 25 minutes. The major toxicity produced by this analog is granulocytopenia. To exploit the full chemotherapeutic potential of 5-AZA-CdR for the treatment of cancer, its optimal dose-schedule has to be found. This will require a good understanding of the pharmacology of this analog and its action on both normal and neoplastic cells.