Disease relevance of Zebularine

• Most important, zebularine demonstrated a complete lack of toxicity in nonirradiated control mice [1].
• The novel DNA methylation inhibitor zebularine is effective against the development of murine T-cell lymphoma [1].
• While 2'-ara-fluorozebularine (7b) is only marginally active (40% ILS) at high doses against L1210 leukemia, 5-fluoro analogue 6b is more active than zebularine and is ca. 100 times more potent [2].
• Zebularine provides increase in life span (ILS) values of ca. 70% against intraperitoneal (ip) murine B16 melanoma and 50% against P388 leukemia [2].
• Zebularine inhibits human acute myeloid leukemia cell growth in vitro in association with p15INK4B demethylation and reexpression [3].

High impact information on Zebularine

• The level of GlyR alpha3-C554U RNA editing is sensitive to experimentally induced brain lesion, inhibition of cytidine deamination by zebularine and inhibition of mRNA transcription by actinomycin D, but not to blockade of protein synthesis by cycloheximide [4].
• We then analyzed the ability of zebularine to inhibit DNA methylation in C3H 10T1/2 Cl8 (10T1/2) mouse embryo cells as assayed by induction of a myogenic phenotype and in T24 human bladder carcinoma cells, using the methylation-sensitive single nucleotide primer extension (Ms-SNuPE) assay [5].
• RESULTS: In N. crassa, zebularine inhibited DNA methylation and reactivated a gene previously silenced by methylation [5].
• Zebularine reactivated a silenced p16 gene and demethylated its promoter region in T24 bladder carcinoma cells in vitro and in tumors grown in mice [5].
• Zebularine induced the myogenic phenotype in 10T1/2 cells, which is a phenomenon unique to DNA methylation inhibitors [5].

Chemical compound and disease context of Zebularine

• The cytidine analog zebularine is a stable DNA methylation inhibitor that has minimal toxicity in vitro and in vivo [3].
• In this report, we examined the demethylating agent zebularine [1-(beta-D-ribofuranosyl)-1,2-dihydropyrimidin-2-one], in comparison with the well-known methylation inhibitor 5-aza-2'-deoxycytidine (5-aza-dC), for its ability to inhibit ovarian cancer cell proliferation and to demethylate and induce tumor suppressor genes [6].
• Based on the distinct properties of action we hypothesized that the newer DNMTI Zebularine might differ from 5-Azacytidine in its potential to induce switching from latent to lytic EBV [7].

Biological context of Zebularine

• Inhibition of DNA methylation and reactivation of silenced genes by zebularine [5].
• We used the demethylating drug zebularine to induce changes in DNA methylation, then examined patterns of gene expression using cDNA array analysis and Restriction Landmark Genomic Scanning followed by RNase protection assay and reverse transcription-PCR to confirm the results [8].
• We found that DNMT inhibitors 5-aza-2'-deoxycytidine and zebularine, as well as HDAC inhibitor trichostatin A, reexpressed intercellular adhesion molecule-1 (ICAM-1) on tumor-conditioned endothelial cells in vitro, resulting in restored leukocyte-endothelial cell adhesion [9].
• Moreover, zebularine and 5-aza-2-deoxycytidine, inhibitors of DNMT activity, blocked the induction of long term potentiation at Schaffer collateral synapses [10].
• It is believed that the TSA formed at the active site is zebularine 3,4-hydrate [11].

Anatomical context of Zebularine

• Combined treatment of HCC cell lines with Ras and Jak/Stat inhibitors as well as with the demethylating agent zebularine induced a strong apoptotic response [12].
• Three human tumor cell lines were used in this study (MiaPaCa, DU145, and U251) and the methylation status of three genes frequently hypermethylated in tumor cells (RASSF1A, HIC-1, and 14-3-3sigma) was determined as a function of zebularine exposure [13].
• To aid in the clinical evaluation of zebularine, a potential oral antitumor agent, we initiated studies on the metabolism of zebularine in liver cytosol from humans and other mammals [14].
• In addition, zebularine preferentially depleted DNA methyltransferase 1 (DNMT1) and induced expression of cancer-related antigen genes in cancer cells relative to normal fibroblasts [15].

Associations of Zebularine with other chemical compounds

• METHODS: We tested the ability of zebularine to reactivate a silenced Neurospora crassa gene using a hygromycin gene reactivation assay [5].
• Zebularine is a stable DNA cytosine methylation inhibitor that is currently in development as an epigenetic therapy for cancer [16].
• In the present study we investigated the effects of the deaminase inhibitors Zebularine, 5-F-Zebularine, and diazepinone riboside on the deamination of CR, ARA-C, and 5-AZA-CdR using highly purified human CR deaminase (EC 3.5.4.5) [17].
• In addition to the four well-characterized nucleoside analogue methylation inhibitors, 5-azacytidine, 5-aza-2'-deoxycytidine (5-Aza-CdR), 5-fluoro-2'-deoxycytidine, and zebularine, there is a growing list of non-nucleoside inhibitors [18].
• Global analyses of DNA methylation revealed similar overall demethylation (2.5- to 3-fold) by 5-aza-dC and zebularine as determined by methyl acceptance assay [6].

Gene context of Zebularine

• This hypermethylation was significantly abated by Zebularine, a potent demethylating agent, with a consequent increase in the hHR23B mRNA level [19].
• Treatment of MDAPCa2b prostate cancer cells with the methylation inhibitors 5-aza-2-deoxycitidine and Zebularine reactivated expression of ASC [20].
• Here we show that continuous application of zebularine to T24 cells induces and maintains p16 gene expression and sustains demethylation of the 5' region for over 40 days, preventing remethylation [21].
• The DNA methyltransferase inhibitor zebularine reverses the methylation of the p53 promoter, allowing the resumption of its expression [22].
• EXPERIMENTAL DESIGN: Real-time reverse transcription-PCR was used to evaluate the ability of zebularine and 5-aza-2'-deoxycytidine (5-aza-dCyd) to re-express VHL in four ccRCC cell lines with documented VHL gene silencing through hypermethylation [23].

Analytical, diagnostic and therapeutic context of Zebularine

• CONCLUSIONS: Zebularine is a stable DNA demethylating agent and the first drug in its class able to reactivate an epigenetically silenced gene by oral administration [5].
• Compared with those in control mice, tumor volumes were statistically significantly reduced in mice treated with high-dose zebularine administered by intraperitoneal injection (P<.001) or by oral gavage (P<.001) [5].
• p53 expression after treatment with zebularine is not due to demethylation [24].
• Zebularine administration to mice reactivated gene expression in U251 xenografts; irradiation of U251 tumors in mice treated with zebularine resulted in an increase in radiation-induced tumor growth delay [13].
• Zebularine: a unique molecule for an epigenetically based strategy in cancer chemotherapy [25].

References