Synthesis of 1,4-azaphosphinine nucleosides and evaluation as inhibitors of human cytidine deaminase and APOBEC3A.

Nucleoside and polynucleotide cytidine deaminases (CDAs), such as CDA and APOBEC3, share a similar mechanism of cytosine to uracil conversion. In 1984, phosphapyrimidine riboside was characterised as the most potent inhibitor of human CDA, but the quick degradation in water limited the applicability as a potential therapeutic. To improve stability in water, we synthesised derivatives of phosphapyrimidine nucleoside having a CH2 group instead of the N3 atom in the nucleobase. A charge-neutral phosphinamide and a negatively charged phosphinic acid derivative had excellent stability in water at pH 7.4, but only the charge-neutral compound inhibited human CDA, similar to previously described 2'-deoxyzebularine (Ki = 8.0 ± 1.9 and 10.7 ± 0.5 µM, respectively). However, under basic conditions, the charge-neutral phosphinamide was unstable, which prevented the incorporation into DNA using conventional DNA chemistry. In contrast, the negatively charged phosphinic acid derivative was incorporated into DNA instead of the target 2'-deoxycytidine using an automated DNA synthesiser, but no inhibition of APOBEC3A was observed for modified DNAs. Although this shows that the negative charge is poorly accommodated in the active site of CDA and APOBEC3, the synthetic route reported here provides opportunities for the synthesis of other derivatives of phosphapyrimidine riboside for potential development of more potent CDA and APOBEC3 inhibitors.

A drug-delivery depot for epigenetic modulation and enhanced cancer immunotherapy.

DNA methyltransferase inhibitors (DNMTis) have found widespread application in the management of cancer. Zebularine (Zeb), functioning as a demethylating agent, has exhibited notable advantages and enhanced therapeutic efficacy in the realm of tumour immunotherapy. Nevertheless, due to its lack of targeted functionality, standalone Zeb therapy necessitates the administration of a substantially higher dosage. In this investigation, we have devised an innovative nanodrug formulation, comprising the DNA methyltransferase inhibitor Zeb and pH-responsive chitosan (CS), hereinafter referred to as CS-Zeb nanoparticles (NPs). Our findings have unveiled that CS-Zeb NPs manifest heightened drug release within an acidic milieu (pH 5.5) in comparison to a neutral environment (pH 7.4). Furthermore, in vivo studies have conclusively affirmed that, in contrast to equivalent quantities of Zeb in isolation, the nanocomplex significantly curtailed tumour burden and protracted the survival duration of the B16F10 tumour-bearing murine model. Additionally, CS-Zeb NPs elicited an augmentation of CD8+ T cells within the peripheral circulation of mice and tumour-infiltrating lymphocytes (TILs). Notably, the dosage of CS-Zeb NPs was reduced by a remarkable 70-fold when juxtaposed with Zeb administered in isolation. To summarise, our study underscores the potential of CS-Zeb NPs as an alternative chemotherapeutic agent for cancer treatment.

Effect of Zebularine on Apoptotic Pathways in Hepatocellular Carcinoma Cell Lines.

Background: The alteration of DNA cytosine methylation is one of the most common epigenetic changes that can play a significant role in human cancers. The enzymes involved in DNA methylation of promoter regions of the genes are DNA methyltransferases (DNMTs). The therapeutic activities and apoptotic effects of DNA methyltransferase inhibitors (DNMTIs) have been reported in various cancers. This study was assigned to assess the effect of zebularine on intrinsic and extrinsic pathways, DNAT 1, 3a, and 3b, p21, and p53, viability, and apoptosis in hepatocellular carcinoma (HCC) cell lines. Methods: Hepatocellular carcinoma cell lines (HCCLM3, MHCC97H, and MHCC97L) were purchased from the National Cell Bank of Iran, Pasteur Institute, treated with zebularine, and the MTT assay was performed. Then, flow cytometry assay and real-time RT-PCR analysis were performed with zebularine. Statistical comparisons between groups were made using GraphPad Prism software version 8.0. A significant difference was considered as P < 0.05. Results: Zebularine up-regulated DR4, DR5, FAS, FAS-L, TRAIL, Bax, Bak, Bim, p21WAF/CIP1 (p21), and p53 and down-regulated DNMTs (DNAT 1, 3a, and 3b), Bcl-2, Bcl-xL, and Mcl-1, significantly resulting in apoptosis induction in HCC cell lines. Maximal and minimal apoptosis was seen in HCCLM3 and MHCC97L cell lines, respectively. Conclusions: Our findings indicated that DNMTI zebularine can induce apoptosis and inhibit cell growth through both pathways (extrinsic and intrinsic) in HCC cell lines HCCLM3, MHCC97H, and MHCC97L.

Trailing TRAIL Resistance in Human Breast Adenocarcinoma Cells with Trichostatin A and Zebularine.

AIMS: The aim of this study was to sensitize the resistant breast adenocarcinoma cells towards Tumour Necrosis Factor-related Apoptosis-inducing Ligand (TRAIL)-induced apoptosis. BACKGROUND: Breast cancer is a heterogeneous disease involving complex mechanisms. TRAIL is a potential anticancer candidate for targeted treatment due to its selective killing effects on neoplastic cells. Nonetheless, resistance occurs in many cancers either intrinsically or after multiple treatments. OBJECTIVE: Therefore, this research investigated whether the combination of Trichostatin A (TSA) and Zebularine (Zeb) (TZ) followed by TRAIL (TZT) could sensitize the human breast adenocarcinoma cells towards apoptosis. METHODS: The breast adenocarcinoma cells, MDA-MB-231, MCF-7 and E-MDA-MB-231 (E-cadherin re-expressed MDA-MB-231) were treated with TSA, Zeb, TZ, TRAIL and TZT. The cells were subjected to hematoxylin and eosin (H & E) staining and FITC-Annexin V/Propidium Iodide apoptosis detection prior to proteome profiling. RESULTS: Based on morphological observation, apoptosis was induced in all cells treated with all treatment regimens though it was more evident for the TZT-treated cells. In the apoptosis detection analysis, TZ increased early apoptosis significantly in MDA-MB-231 and MCF-7 while TRAIL induced late apoptosis significantly in E-MDA-MB-231. Based on the proteome profiling on MDA-MB-231, TRAIL R2 and Fas expression was increased. For E-MDA-MB- 231, down-regulation of catalase, paraoxonase-2 (PON2), clusterin, an inhibitor of apoptosis proteins (IAPs) and cell stress proteins validated the notion that E-cadherin re-expression enhances TZT anti-cancer efficacy. Similar trend was observed in MCF-7 whereby TZT treatment down-regulated the anti-apoptotic catalase and PON2, increased the proapoptotic, B cell lymphoma 2 (Bcl-2)-associated agonist of cell death (Bad) and Bcl-2-associated X (Bax), second mitochondria-derived activator of caspase (SMAC) and HtrA serine peptidase 2 (HTRA2) as well as TRAIL receptors (TRAIL R1 and TRAIL R2). CONCLUSION: TZ treatment serves as an efficient treatment regimen for MDA-MB-231 and MCF-7, while TRAIL serves as a better treatment option for E-MDA-MB-231. Therefore, future studies on E-cadherin's positive regulatory role in TRAIL-induced apoptosis are warranted.

Comparison the effects of 5-Aza-2'-deoxycytidine and zebularine on the in vitro development, blastocyst quality, methylation pattern and conception rate on handmade cloned buffalo embryos.

In this study we treated the handmade cloned (HMC) buffalo embryos with the DNA methylation inhibitors; 5-aza-2'-deoxycytidine (AzadC) or Zebularine individually after post-fusion and during in vitro culture till eighth day. The blastocysts production rate significantly improved (p < .01) after treating embryos independently with 5 nM AzadC and 5 nM zebularine compared with 2 and 10 nM AzadC or zebularine groups, respectively. The highest cleavage rates were obtained for 5 nM treatment of AzadC and zebularine compared with other treatments and untreated control group. Quality of blastocysts were evaluated using total cell number (TCN) and the ratio of number of inner cell mass (ICM) cells/total cell number (ICM/TCN). Zebularine treatments (2/5/10 nM) significantly improved both TCN and ICM/TCN ratio compared with AzadC treatments (2/5/10 nM); however, control group TCN and ICM/TCN ratio was found lower. The methylation percentage of pDS4.1 and B. bubalis satellite DNA were comparatively more attenuated with 5 nM zebularine than 5 nM AzadC treatment. The increased in vitro development rates of the treated embryos were correlated with the decreased level of DNA methylation and the improved blastocyst quality. Following transfer of 5 nM zebularine treated embryos to 6 recipients, 4 were found to be pregnant, though the pregnancies were not carried to full term.

Examination of epigenetic inhibitor zebularine in treatment of skin wounds in healthy and diabetic mice.

DNA methyltransferase inhibitor zebularine was proven to induce regeneration in the ear pinna in mice. We utilized a dorsal skin wound model to further evaluate this epigenetic inhibitor in wound healing. Full-thickness excisional wounds were made on the dorsum of 2 and 10-month-old healthy BALB/c and 3 and 8-month-old diabetic (db/db) mice, followed by topical or intraperitoneal zebularine delivery. Depending on the strain, age, dose, and delivery, the zebularine treatments either had no effect or accelerated or delayed wound closure. In principle, zebularine applied topically moderately promoted wound closure in the healthy but markedly delayed in the diabetic mice, which was in line with decreased viability of cultured keratinocytes from diabetic patients exposed to zebularine. The histological analysis revealed an improvement in the architecture of restored skin in zebularine-treated mice, manifested as a distinct layered pattern resembling panniculus carnosus. The finding corresponds with the zebularine-mediated activation of the Wnt5a gene, an essential regulator of Wnt signaling, the pathway involved in hair follicle development, the process which in turn is connected with regenerative skin healing. Although zebularine did not remarkably accelerate wound healing, zebularine and other epigenetic inhibitors deserve further testing as potential drugs to improve the quality of restored skin.

Combination of mesenchymal stem cells and three-dimensional collagen scaffold preserves ventricular remodeling in rat myocardial infarction model.

BACKGROUND: Cardiovascular diseases are the major cause of mortality worldwide. Regeneration of the damaged myocardium remains a challenge due to mechanical constraints and limited healing ability of the adult heart tissue. Cardiac tissue engineering using biomaterial scaffolds combined with stem cells and bioactive molecules could be a highly promising approach for cardiac repair. Use of biomaterials can provide suitable microenvironment to the cells and can solve cell engraftment problems associated with cell transplantation alone. Mesenchymal stem cells (MSCs) are potential candidates in cardiac tissue engineering because of their multilineage differentiation potential and ease of isolation. Use of DNA methyl transferase inhibitor, such as zebularine, in combination with three-dimensional (3D) scaffold can promote efficient MSC differentiation into cardiac lineage, as epigenetic modifications play a fundamental role in determining cell fate and lineage specific gene expression. AIM: To investigate the role of collagen scaffold and zebularine in the differentiation of rat bone marrow (BM)-MSCs and their subsequent in vivo effects. METHODS: MSCs were isolated from rat BM and characterized morphologically, immunophenotypically and by multilineage differentiation potential. MSCs were seeded in collagen scaffold and treated with 3 µmol/L zebularine in three different ways. Cytotoxicity analysis was done and cardiac differentiation was analyzed at the gene and protein levels. Treated and untreated MSC-seeded scaffolds were transplanted in the rat myocardial infarction (MI) model and cardiac function was assessed by echocardiography. Cell tracking was performed by DiI dye labeling, while regeneration and neovascularization were evaluated by histological and immunohistochemical analysis, res pectively. RESULTS: MSCs were successfully isolated and seeded in collagen scaffold. Cytotoxicity analysis revealed that zebularine was not cytotoxic in any of the treatment groups. Cardiac differentiation analysis showed more pronounced results in the type 3 treatment group which was subsequently chosen for the transplantation in the in vivo MI model. Significant improvement in cardiac function was observed in the zebularine treated MSC-seeded scaffold group as compared to the MI control. Histological analysis also showed reduction in fibrotic scar, improvement in left ventricular wall thickness and preservation of ventricular remodeling in the zebularine treated MSC-seeded scaffold group. Immunohistochemical analysis revealed significant expression of cardiac proteins in DiI labeled transplanted cells and a significant increase in the number of blood vessels in the zebularine treated MSC-seeded collagen scaffold transplanted group. CONCLUSION: Combination of 3D collagen scaffold and zebularine treatment enhances cardiac differentiation potential of MSCs, improves cell engraftment at the infarcted region, reduces infarct size and improves cardiac function.

Zebularine, a DNA Methylation Inhibitor, Activates Anthocyanin Accumulation in Grapevine Cells.

Through its role in the regulation of gene expression, DNA methylation can participate in the control of specialized metabolite production. We have investigated the link between DNA methylation and anthocyanin accumulation in grapevine using the hypomethylating drug, zebularine and Gamay Teinturier cell suspensions. In this model, zebularine increased anthocyanin accumulation in the light, and induced its production in the dark. To unravel the underlying mechanisms, cell transcriptome, metabolic content, and DNA methylation were analyzed. The up-regulation of stress-related genes, as well as a decrease in cell viability, revealed that zebularine affected cell integrity. Concomitantly, the global DNA methylation level was only slightly decreased in the light and not modified in the dark. However, locus-specific analyses demonstrated a decrease in DNA methylation at a few selected loci, including a CACTA DNA transposon and a small region upstream from the UFGT gene, coding for the UDP glucose:flavonoid-3-O-glucosyltransferase, known to be critical for anthocyanin biosynthesis. Moreover, this decrease was correlated with an increase in UFGT expression and in anthocyanin content. In conclusion, our data suggest that UFGT expression could be regulated through DNA methylation in Gamay Teinturier, although the functional link between changes in DNA methylation and UFGT transcription still needs to be demonstrated.

Possible Involvement of DNA Methylation and Protective Effect of Zebularine on Neuronal Cell Death after Glutamate Excitotoxity.

Neuronal cell death after cerebral ischemia consists various steps including glutamate excitotoxity. Excessive Ca2+ influx through the N-methyl-D-aspartate (NMDA) receptor, which is one of the ionotropic glutamate receptors, plays a central role in neuronal cell death after cerebral ischemia. We previously reported that DNA methylation is transiently increased in neurons during ischemic injury and that this aberrant DNA methylation is accompanied by neuronal cell death. Therefore, we performed the present experiments on glutamate excitotoxicity to gain further insight into DNA methylation involvement in the neuronal cell death. We demonstrated that knockdown of DNA methyltransferase (DNMT)1, DNMT3a, or DNMT3b gene in Neuro2a cells was performed to examine which DNMTs were more important for neuronal cell death after glutamate excitotoxicity. Although we confirmed a decrease in the levels of the target DNMT protein after small interfering RNA (siRNA) transfection, the Neuro2a cells were not protected from injury by transfection with siRNA for each DNMT. We next revealed that the pharmacological inhibitor of DNMTs protected against glutamate excitotoxicity in Neuro2a cells and also in primary cultured cortical neurons. This protective effect was associated with a decrease in the number of 5-methylcytosine (5 mC)-positive cells under glutamate excitotoxicity. In addition, the increased level of cleaved caspase-3 was also reduced by a DNMT inhibitor. Our results suggest the possibility that at least 2 or all DNMTs functionally would cooperate to activate DNA methylation after glutamate excitotoxicity and that inhibition of DNA methylation in neurons after cerebral ischemia might become a strategy to reduce the neuronal injury.

Role of Wnt/ß-catenin pathway in cardiac lineage commitment of human umbilical cord mesenchymal stem cells by zebularine and 2'-deoxycytidine.

Wnt/ß-catenin, a highly conserved signaling pathway, is involved in determining cell fate. During heart development, Wnt signaling controls specification, proliferation and differentiation of cardiac cells. This study is aimed to investigate the role of Wnt/ß-catenin signaling in cardiac lineage commitment of human umbilical cord mesenchymal stem cells (hUCMSCs) after treatment with demethylating agents, zebularine and 2'-deoxycytidine (2-DC). hUCMSCs were treated with 20 µM zebularine or 2-DC for 24 h and cultured for 14 days. Control and treated MSCs were analyzed for cardiac lineage commitment at gene and protein levels. Significant upregulation of early and late cardiac markers, GATA4, Nkx2.5, cardiac myosin heavy chain (cMHC), α-actinin, cardiac troponin T (cTnT) and cardiac troponin I (cTnI) was observed in treated MSCs as compared to the untreated control. We also analyzed gene expression of key Wnt/ß-catenin signaling molecules in cultures of treated and untreated hUCMSCs at 24 h, and days 3, 7 and 14. The pattern of mRNA gene expression showed that Wnt/ß-catenin signaling is regulated during cardiac lineage commitment of hUCMSCs in a time-dependent manner, with the pathway being activated early but inhibited later in cardiac development. Findings of this study can lead us to identify more specific and effective strategies for cardiac lineage commitment.

Zebularine protects against blood-brain-barrier (BBB) disruption through increasing the expression of zona occludens-1 (ZO-1) and vascular endothelial (VE)-cadherin.

Blood-brain-barrier (BBB) disruption is an important pathological characteristic of ischemic stroke (IS) and mainly results from dysfunction of brain vascular endothelial cells and tight junctions. Zebularine is a novel inhibitor of DNA methyltransferase (DNMT). Here, we assessed its effects on BBB disruption in IS. Firstly, we reported that Zebularine maintained BBB integrity in middle cerebral artery occlusion (MCAO) mice by increasing the expressions of zona occludens-1 (ZO-1) and vascular endothelial (VE)-cadherin. Importantly, we found that Zebularine reduced the production of pro-inflammatory cytokines, attenuated brain edema, and improved neurological deficits. In in vitro experiments, the bEnd.3 brain endothelial cells were exposed to oxygen and glucose deprivation/reoxygenation (OGD/R), and the protective effects of Zebularine were assessed. Our findings demonstrated that Zebularine prevented OGD/R-induced cytotoxicity by reducing the release of lactate dehydrogenase (LDH). Additionally, Zebularine protected bEnd.3 cells against OGD/R-induced hyper-permeability and reduction of trans-endothelial electrical resistance (TEER). Notably, we found that treatment with Zebularine activated the Adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK) pathway by increasing the phosphorylation of adenosine monophosphate-activated protein kinase α (AMPKα). Blockage of AMPKα using its specific inhibitor compound C abolished the beneficial effects of Zebularine in mitigating endothelial hyper-permeability by reducing the expressions of ZO-1 and VE-cadherin. These findings suggest that the protective effects of Zebularine against OGD/R-induced endothelial hyper-permeability are mediated by the activation of AMPKα. In conclusion, our study sheds light on the potential application of Zebularine in the treatment of IS.

Anti-Cancer Effects of Epigenetics Drugs Scriptaid and Zebularine in Human Breast Adenocarcinoma Cells.

BACKGROUND: High relapse and metastasis progression in breast cancer patients have prompted the need to explore alternative treatments. Epigenetic therapy has emerged as an attractive therapeutic strategy due to the reversibility of epigenome structures. OBJECTIVE: This study investigated the anti-cancer effects of epigenetic drugs scriptaid and zebularine in human breast adenocarcinoma MDA-MB-231 and MCF-7 cells. METHODS: First, the half maximal Inhibitory Concentration (IC50) of scriptaid and zebularine, and the combination of both drugs on human breast adenocarcinoma MDA-MB-231 cells were determined. Next, MDA-MB-231 and MCF-7 cells were treated with IC50 of scriptaid, zebularine and the combination of both. After IC50 treatments, the anti-cancer effects were evaluated via cell migration assay, cell cycle analysis and apoptotic studies which included histochemical staining and reverse-transcriptase polymerase chain reaction (RT-PCR) of the apoptotic genes. RESULTS: Both epigenetic drugs inhibited cell viability in a dose-dependent manner with IC50 of 2 nM scriptaid, 8 µM zebularine and a combination of 2 nM scriptaid and 2 µM zebularine. Both MDA-MB-231 and MCF-7 cells exhibited a reduction in cell migration after the treatments. In particular, MDA-MB-231 cells exhibited a significant reduction in cell migration (p < 0.05) after the treatments of zebularine and the combination of scriptaid and zebularine. Besides, cell cycle analysis demonstrated that scriptaid and the combination of both drugs could induce cell cycle arrest at the G0/G1 phase in both MDA-MB-231 and MCF-7 cells. Furthermore, histochemical staining allowed the observation of apoptotic features, such as nuclear chromatin condensation, cell shrinkage, membrane blebbing, nuclear chromatin fragmentation and cytoplasmic extension, in both MDA-MB-231 and MCF-7 cells after the treatments. Further, apoptotic studies revealed the upregulation of pro-apoptotic Bax, downregulation of anti-apoptotic Bcl-2 and elevation of Bax/Bcl-2 ratio in MDA-MB-231 cells treated with zebularine and MCF-7 cells treated with all drug regimens. CONCLUSION: Collectively, these findings suggest that scriptaid and zebularine are potential anti-cancer drugs, either single or in combination, for the therapy of breast cancer. Further investigations of the gene regulatory pathways directed by scriptaid and zebularine are definitely warranted in the future.

Effect of Zebularine in Comparison to Trichostatin A on the Intrinsic and Extrinsic Apoptotic Pathway, Cell Viability, and Apoptosis in Hepatocellular Carcinoma SK-Hep 1, Human Colorectal Cancer SW620, and Human Pancreatic Cancer PaCa-44 Cell Lines.

Aberrant histone modifications or promoter region hypermethylation of tumor suppressor genes (TSGs) have been recognized as the important epigenetic molecular mechanism in cancer induction. The potential anticancer activities of histone deacetylase inhibitors (HDACIs) and DNA methyltransferase inhibitors (DNMTIs) have been investigated in recent years. The current study was assigned to investigate the effect of trichostatin A (HDACI) in comparison to zebularine (DNMTI) on the intrinsic pro-apoptotic (Bax, Bim, and Bak) and anti-apoptotic (Bcl-2, Mcl-1, and Bcl-xL) genes and extrinsic (DR4, DR5, FAS, FAS-L, and TRAIL genes) pathways, DNA methyltransferase 1, 3a, and 3b, histone deacetylase inhibitors 1, 2, and 3, cell viability, and apoptosis in hepatocellular carcinoma (HCC) SK-Hep 1, colorectal cancer SW620, and pancreatic cancer PaCa-44 cell lines. The SK-Hep 1, SW620, and PaCa-44 cells were cultured and treated with TSA and zebularine. To determine cell apoptosis, cell viability, and the relative gene expression level, flow cytometry assay, MTT assay, and qRT-PCR were done respectively. The result indicated that zebularine and TSA changed the expression level of the Bax, Bak, Bim Bcl-2, Bcl-xL, Mcl-1, DR4, DR5, FAS, FAS-L, TRAIL, DNA methyltransferase 1, 3a, and 3b, histone deacetylase inhibitors 1, 2, and 3 by which induced cell apoptosis and inhibit cell growth in all three cell lines. Concluding, TSA induced its role through both extrinsic and intrinsic apoptotic pathways in three cell lines, whereas, zebularine played its role via both pathways in the SK-Hep 1cell line, it had no significant effect on Bcl-2, Bcl-xL, and Mcl-1 gene expression in SW620 and PaCa-44 cell lines.

Zebularine suppressed gemcitabine-induced senescence and improved the cellular and plasma pharmacokinetics of gemcitabine, augmented by liposomal co-delivery.

Chemoresistance is a major factor driving cancer recurrence. This study investigated the potential of zebularine, a dual cytidine deaminase (CDA)/epigenetic inhibitor, to circumvent gemcitabine-resistance in pancreatic cancer using a nanomedicine co-delivery approach. The mRNA expression of key metabolic enzymes, including CDA for gemcitabine deactivation in a gemcitabine-resistant cell line Gr2000 and its parental MIA PaCa-2 was compared using quantitative reverse transcription polymerase chain reaction. A highly gemcitabine-resistant population (HRP) in Gr2000 were characterised for their growth pattern, ß-galactosidase activity (a hallmark of senescence) and chemosensitivity to zebularine after isolation. The CDA inhibition effects of zebularine on the intracellular gemcitabine accumulation and pharmacokinetics in rats when co-delivered with pH-sensitive liposomes (pSL) were investigated. Gr2000 had a 3-time upregulated mRNA expression and enzyme activity for CDA. The HRP (28% of bulk Gr2000) were predominately senescent cells which re-proliferated following a growth arrest for a week. Zebularine suppressed the regrowth of senescent cells, meanwhile enhanced cellular gemcitabine concentration by 2-fold. When co-delivered with pSL, zebularine increased cellular gemcitabine concentration by 4-fold, and extended the half-life of gemcitabine in plasma by 22-fold in rats. In conclusion, multiple mechanisms including therapy-induced senescence were identified with gemcitabine-resistance. Co-delivery of zebularine using liposomes could provide multifaceted benefits in gemcitabine therapy for pancreatic cancer treatment.

In vitro assessment of a synergistic combination of gemcitabine and zebularine in pancreatic cancer cells.

Pancreatic ductal adenocarcinoma (PDAC) is one of the deadliest cancers with an extremely poor prognosis. Gemcitabine (Gem) is still the mainstay drug for the treatment of PDAC. However, rapid inactivation by cytidine deaminase (CDA) present in pancreatic cancer cells severely limits anticancer efficacy of Gem. In this study, we investigated the effect of a CDA inhibitor - Zebularine (Zeb) on anticancer activity of Gem in pancreatic cancer cell lines MiaPaCa-2, BxPC-3, and Panc-1. Zeb treatment synergistically increased Gem-induced cytotoxicity in all three pancreatic cancer cell lines. The strongest synergistic activity was found at 1:10 M ratio of Gem/Zeb (combination index 0.04-0.4). Additionally, Gem + Zeb treated cells showed marked decreased in the expressions of anti-apoptotic protein including Bcl-2 and survivin while significantly increased the cleaved caspase-3, and loss of mitochondrial membrane potential was observed. Multicellular 3D spheroids of MiaPaCa-2 cells treated with combination showed significant reduction (25-60%) in spheroid size, weight compared to single drug and control group. Live/dead cell imaging showed that Gem + Zeb treated spheroids exhibited a highly distorted surface with significantly higher number of dead cells (red). The results of the present study confirm that this synergistic combination is worthy of future investigations as a potential approach for the treatment of PDAC.

Zebularine elevates STING expression and enhances cGAMP cancer immunotherapy in mice.

DNA methylation abnormality is closely related to tumor occurrence and development. Chemical inhibitors targeting DNA methyltransferase (DNMTis) have been used in treating cancer. However, the impact of DNMTis on antitumor immunity has not been well elucidated. In this study, we show that zebularine (a demethylating agent) treatment of cancer cells led to increased levels of interferon response in a cyclic guanosine monophosphate-AMP (cGAMP) synthase (cGAS)- and stimulator of interferon genes (STING)-dependent manner. This treatment also specifically sensitized the cGAS-STING pathway in response to DNA stimulation. Incorporation of zebularine into genomic DNA caused demethylation and elevated expression of a group of genes, including STING. Without causing DNA damage, zebularine led to accumulation of DNA species in the cytoplasm of treated cells. In syngeneic tumor models, administration of zebularine alone reduced tumor burden and extended mice survival. This effect synergized with cGAMP and immune checkpoint blockade therapy. The efficacy of zebularine was abolished in nude mice and in cGAS-/- or STING-/- mice, indicating its dependency on host immunity. Analysis of tumor cells indicates upregulation of interferon-stimulated genes (ISGs) following zebularine administration. Zebularine promoted infiltration of CD8 T cells and natural killer (NK) cells into tumor and therefore suppressed tumor growth. This study unveils the role of zebularine in sensitizing the cGAS-STING pathway to promote anti-tumor immunity and provides the foundation for further therapeutic development.

Distinct Responses of Arabidopsis Telomeres and Transposable Elements to Zebularine Exposure.

Involvement of epigenetic mechanisms in the regulation of telomeres and transposable elements (TEs), genomic regions with the protective and potentially detrimental function, respectively, has been frequently studied. Here, we analyzed telomere lengths in Arabidopsis thaliana plants of Columbia, Landsberg erecta and Wassilevskija ecotypes exposed repeatedly to the hypomethylation drug zebularine during germination. Shorter telomeres were detected in plants growing from seedlings germinated in the presence of zebularine with a progression in telomeric phenotype across generations, relatively high inter-individual variability, and diverse responses among ecotypes. Interestingly, the extent of telomere shortening in zebularine Columbia and Wassilevskija plants corresponded to the transcriptional activation of TEs, suggesting a correlated response of these genomic elements to the zebularine treatment. Changes in lengths of telomeres and levels of TE transcripts in leaves were not always correlated with a hypomethylation of cytosines located in these regions, indicating a cytosine methylation-independent level of their regulation. These observations, including differences among ecotypes together with distinct dynamics of the reversal of the disruption of telomere homeostasis and TEs transcriptional activation, reflect a complex involvement of epigenetic processes in the regulation of crucial genomic regions. Our results further demonstrate the ability of plant cells to cope with these changes without a critical loss of the genome stability.

Manipulation of cytosine methylation does not remove latitudinal clines in two invasive goldenrod species in Central Europe.

Invasive species frequently differentiate phenotypically in novel environments within a few generations, often even with limited genetic variation. For the invasive plants Solidago canadensis and S. gigantea, we tested whether such differentiation might have occurred through heritable epigenetic changes in cytosine methylation. In a 2-year common-garden experiment, we grew plants from seeds collected along a latitudinal gradient in their non-native Central European range to test for trait differentiation and whether differentiation disappeared when seeds were treated with the demethylation agent zebularine. Microsatellite markers revealed no population structure along the latitudinal gradient in S. canadensis, but three genetic clusters in S. gigantea. Solidago canadensis showed latitudinal clines in flowering phenology and growth. In S. gigantea, the number of clonal offspring decreased with latitude. Although zebularine had a significant effect on early growth, probably through effects on cytosine methylation, latitudinal clines remained (or even got stronger) in plants raised from seeds treated with zebularine. Thus, our experiment provides no evidence that epigenetic mechanisms by selective cytosine methylation contribute to the observed phenotypic differentiation in invasive goldenrods in Central Europe.

Zebularine induces apoptosis of esophageal cancer cells via demethylation SFRP2/Dkk3 to regulate Wnt/β-catenin signaling pathway / 药学学报

To explore the effect and mechanisms of demethylation drug zebularine on esophageal cancer cells apoptosis, ECA109 cells and KYSE170 cells were treated with zebularine at different concentrations (25, 50, 100, 200, and 400 μmol·L-1). The cell viability was measured by CCK-8. Flow cytometry was used to detect the cell apoptosis rate, Western blot was performed to determine the expression of apoptosis protein (Bcl-2, Bax, cleaved-caspase-3, and cleaved-PARP) and Wnt signal pathway molecules (β-catenin, cyclin D1, and c-Myc), real-time quantitative PCR was used to detect the expression level of negative regulatory genes of Wnt signaling pathway, methylation specific PCR (MSP) was used to detect the methylation status of secreted frizzled related protein 2 (SFRP2) and dickkopf 3 (Dkk3) genes. After knockdown of SFRP2 and Dkk3, the effect of zebularine on apoptosis was detected. The studies showed that zebularine could inhibit the activity of ECA109 and KYSE170 cells in a dose-dependent and time-dependent manner; zebularine could induce cell apoptosis, down-regulate the expression of Bcl-2 protein, up-regulate the expression of Bax, cleaved-caspase-3, and cleaved-PARP protein, and inhibit the expression of β-catenin, cyclin D1, and c-Myc protein (P < 0.05); the mRNA expression levels of Dkk3 and SFRP2 were significantly up-regulated by zebularine, while the methylation levels of SFRP2 and Dkk3 promoters were decreased; knockdown of SFRP2 and Dkk3 could reduce the apoptosis induced by zebularine. In summary, zebularine could reduce the methylation level of SFRP2 and Dkk3 gene promoter, promote the expression of SFRP2 and Dkk3 gene, and then induce the apoptosis of esophageal cancer cells by inhibiting Wnt/β-catenin signaling pathway.

The effect of zebularine on the heat-activated retrotransposon ONSEN in Arabidopsis thaliana and Vigna angularis.

The Ty1/copia-like retrotransposon ONSEN is conserved among Brassica species, as well as in beans, including adzuki bean (Vigna angularis (Willd.) Ohwi & Ohashi), which is one of the economically important crops in Japan. ONSEN has acquired a heat-responsive element that is recognized by plant heat stress defense factors, resulting in its transcription and the production of full-length extrachromosomal DNA under conditions with elevated temperatures. DNA methylation plays an important role in regulating the activation of this transposon in plants. Therefore, chemical inhibition of DNA methyltransferases has been utilized to study the effect of DNA methylation on transposon activation. To understand the effect of DNA methylation on ONSEN activation, Arabidopsis thaliana and adzuki bean seedlings were treated with zebularine, which is known to be an effective chemical demethylation agent. The results showed that ONSEN transcription levels were upregulated in zebularine-treated plants. Extrachromosomal DNA of ONSEN also accumulated in the treated plants.