Comparison of the anti-cancer effect of Disulfiram and 5-Aza-CdR on pancreatic cancer cell line PANC-1

Effects of 5-Aza on neurogenesis contribute to learning and memory in the mouse hippocampus

BACKGROUND

5-Aza-2'-deoxycytidine (5-Aza-CdR) is a demethylating agent that has various biological effects related to DNA methylation. DNA methylation plays important roles in learning and memory. We have reported that 5-Aza-CdR improved the performance of mice in the water maze and step-down tests. Some behaviours have been well recognized to be mediated by neurogenesis in the hippocampus. The Notch signalling pathway plays a key role in adult hippocampal neurogenesis. In this study, we examined whether 5-Aza-CdR (DNA methyltransferase inhibitor) affects neurogenesis and Notch1 expression.

METHODS

The learning and memory behaviour of mice was evaluated by a conditioned avoidance learning 24 h after 5-Aza-CdR treatment. The mRNA and protein expression levels of Notch1 and HES1 were measured by real-time PCR and Western blotting. The 5-bromo-2'-deoxyuridine (BrdU)-positive cells and the expression of Notch1 in the hippocampal DG were observed through laser confocal microscopy. To further clarify whether 5-Aza-CdR affects behaviour through neurogenesis, the expression level of Notch1, cell viability and cell cycle were analysed using the HT22 cell line.

RESULTS

The behaviour in conditioned avoidance learning was improved, while neurogenesis and the Notch1 pathway were increased in the hippocampus of mice that were injected with 5-Aza-CdR. In vitro experiments showed that 5-Aza-CdR increased the expression of the Notch1 pathway and upregulated S-phase in the cell cycle and cell viability.

CONCLUSIONS

Our results suggest that the effect of 5-Aza-CdR on behaviour may be related to an increase in neurogenesis with upregulation of the Notch1 pathway in the hippocampus.

Disulfiram Improves the Anti-PD-1 Therapy Efficacy by Regulating PD-L1 Expression via Epigenetically Reactivation of IRF7 in Triple Negative Breast Cancer

Immune checkpoint blockade (ICB), particularly programmed death 1 (PD-1) and its ligand (PD-L1), has shown considerable clinical benefits in patients with various cancers. Many studies show that PD-L1 expression may be biomarkers to help select responders for anti-PD-1 treatment. Therefore, it is necessary to elucidate the molecular mechanisms that control PD-L1 expression. As a potential chemosensitizer and anticancer drug, disulfiram (DSF) kills tumor cells via regulating multiple signaling pathways and transcription factors. However, its effect on tumor immune microenvironment (TIME) remains unclear. Here, we showed that DSF increased PD-L1 expression in triple negative breast cancer (TNBC) cells. Through bioinformatics analysis, we found that DNMT1 was highly expressed in TNBC tissue and PD-L1 was negatively correlated with IRF7 expression. DSF reduced DNMT1 expression and activity, and hypomethylated IRF7 promoter region resulting in upregulation of IRF7. Furthermore, we found DSF enhanced PD-L1 expression via DNMT1-mediated IRF7 hypomethylation. In in vivo experiments, DSF significantly improved the response to anti-PD-1 antibody (Ab) in 4T1 breast cancer mouse model. Immunohistochemistry staining showed that granzyme B+ and CD8+ T cells in the tumor tissues were significantly increased in the combination group. By analyzing the results of the tumor tissue RNA sequencing, four immune-associated pathways were significantly enriched in the DSF joint anti-PD-1 Ab group. In conclusion, we found that DSF could upregulate PD-L1 in TNBC cells and elucidated its mechanism. Our findings revealed that the combination of DSF and anti-PD-1 Ab could activate TIME to show much better antitumor efficacy than monotherapy.

Aberrant Methylation of Tumour Suppressor Gene ADAM12 in Chronic Lympocytic Leukemia Patients: Application of Methylation Specific-PCR Technique

Objective:

Chronic Lymphocytic Leukemia (CLL) is a common leukemia among Caucasians but rare in Asians population. We postulated that aberrant methylation either hypermethylation or partial methylation might be one of the silencing mechanisms that inactivates the tumour suppressor genes in CLL. This study aimed to compare the methylation status of tumour suppressor gene, ADAM12, among CLL patients and normal individuals. We also evaluated the association between methylation of ADAM12 and clinical and demographic characteristics of the participants.

Methods:

A total of 25 CLL patients and 25 normal individuals were recruited in this study. The methylation status of ADAM12 was determined using Methylation-Specific PCR (MSP); whereas, DNA sequencing method was applied for validation of the MSP results.

Results:

Among CLL patients, 12 (48%) were partially methylated and 13 (52%) were unmethylated. Meanwhile, 5 (20%) and 20 (80.6%) of healthy individuals were partially methylated and unmethylated, respectively. There was a statistically significant association between the status of methylation at ADAM12 and the presence of CLL (p=0.037).

Conclusion:

The aberrant methylation of ADAM12 found in this study using MSP assay may provide new exposure to CLL that may improve the gaps involved in genetic epigenetic study in CLL.

Involvement of the ERK/HIF-1α/EMT Pathway in XCL1-Induced Migration of MDA-MB-231 and SK-BR-3 Breast Cancer Cells

Chemokine–receptor interactions play multiple roles in cancer progression. It was reported that the overexpression of X-C motif chemokine receptor 1 (XCR1), a specific receptor for chemokine X-C motif chemokine ligand 1 (XCL1), stimulates the migration of MDA-MB-231 triple-negative breast cancer cells. However, the exact mechanisms of this process remain to be elucidated. Our study found that XCL1 treatment markedly enhanced MDA-MB-231 cell migration. Additionally, XCL1 treatment enhanced epithelial–mesenchymal transition (EMT) of MDA-MB-231 cells via E-cadherin downregulation and upregulation of N-cadherin and vimentin as well as increases in β-catenin nucleus translocation. Furthermore, XCL1 enhanced the expression of hypoxia-inducible factor-1α (HIF-1α) and phosphorylation of extracellular signal-regulated kinase (ERK) 1/2. Notably, the effects of XCL1 on cell migration and intracellular signaling were negated by knockdown of XCR1 using siRNA, confirming XCR1-mediated actions. Treating MDA-MB-231 cells with U0126, a specific mitogen-activated protein kinase kinase (MEK) 1/2 inhibitor, blocked XCL1-induced HIF-1α accumulation and cell migration. The effect of XCL1 on cell migration was also evaluated in ER^-/HER2⁺ SK-BR-3 cells. XCL1 also promoted cell migration, EMT induction, HIF-1α accumulation, and ERK phosphorylation in SK-BR-3 cells. While XCL1 did not exhibit any significant impact on the matrix metalloproteinase (MMP)-2 and -9 expressions in MDA-MB-231 cells, it increased the expression of these enzymes in SK-BR-3 cells. Collectively, our results demonstrate that activation of the ERK/HIF-1α/EMT pathway is involved in the XCL1-induced migration of both MDA-MB-231 and SK-BR-3 breast cancer cells. Based on our findings, the XCL1–XCR1 interaction and its associated signaling molecules may serve as specific targets for the prevention of breast cancer cell migration and metastasis.

Hamartin: An Endogenous Neuroprotective Molecule Induced by Hypoxic Preconditioning

Hypoxic/ischemic preconditioning (HPC/IPC) is an innate neuroprotective mechanism in which a number of endogenous molecules are known to be involved. Tuberous sclerosis complex 1 (TSC1), also known as hamartin, is thought to be one such molecule. It is also known that hamartin is involved as a target in the rapamycin (mTOR) signaling pathway, which functions to integrate a variety of environmental triggers in order to exert control over cellular metabolism and homeostasis. Understanding the role of hamartin in ischemic/hypoxic neuroprotection will provide a novel target for the treatment of hypoxic-ischemic disease. Therefore, the proposed molecular mechanisms of this neuroprotective role and its preconditions are reviewed in this paper, with emphases on the mTOR pathway and the relationship between the expression of hamartin and DNA methylation.

DNMT1 as a therapeutic target in pancreatic cancer: mechanisms and clinical implications

BACKGROUND

Pancreatic cancer or pancreatic ductal adenocarcinoma (PDAC) is one of the most devastating cancer types with a 5-year survival rate of only 9%. PDAC is one of the leading causes of cancer-related deaths in both genders. Epigenetic alterations may lead to the suppression of tumor suppressor genes, and DNA methylation is a predominant epigenetic modification. DNA methyltransferase 1 (DNMT1) is required for maintaining patterns of DNA methylation during cellular replication. Accumulating evidence has implicated the oncogenic roles of DNMT1 in various malignancies including PDACs.

CONCLUSIONS

Herein, the expression profiles, oncogenic roles, regulators and inhibitors of DNMT1 in PDACs are presented and discussed. DNMT1 is overexpressed in PDAC cases compared with non-cancerous pancreatic ducts, and its expression gradually increases from pre-neoplastic lesions to PDACs. DNMT1 plays oncogenic roles in suppressing PDAC cell differentiation and in promoting their proliferation, migration and invasion, as well as in induction of the self-renewal capacity of PDAC cancer stem cells. These effects are achieved via promoter hypermethylation of tumor suppressor genes, including cyclin-dependent kinase inhibitors (e.g., p14, p15, p16, p21 and p27), suppressors of epithelial-mesenchymal transition (e.g., E-cadherin) and tumor suppressor miRNAs (e.g., miR-148a, miR-152 and miR-17-92 cluster). Pre-clinical investigations have shown the potency of novel non-nucleoside DNMT1 inhibitors against PDAC cells. Finally, phase I/II clinical trials of DNMT1 inhibitors (azacitidine, decitabine and guadecitabine) in PDAC patients are currently underway, where these inhibitors have the potential to sensitize PDACs to chemotherapy and immune checkpoint blockade therapy.

5-Aza-2'-deoxycytidine increases hypoxia tolerance-dependent autophagy in mouse neuronal cells by initiating the TSC1/mTOR pathway

BACKGROUND

Our previous study found that 5-Aza-2'-deoxycytidine (5-Aza-CdR) can repress the expression and activity of protein serine/threonine phosphatase-1γ (PP1γ) in mouse hippocampus. It is well known that PP1γ regulates cell metabolism, which is related to hypoxia/ischaemia tolerance. It has been reported that it can also induce autophagy in cancer cells. Autophagy is important for maintaining cellular homeostasis associated with metabolism. In this study, we examined whether 5-Aza-CdR increases hypoxia tolerance-dependent autophagy by initiating the TSC1/mTOR/autophagy signalling pathway in neuronal cells.

METHODS

5-Aza-CdR was either administered to mice via intracerebroventricular injection (i.c.v) or added to cultured hippocampal-derived neuronal cell line (HT22 cell) in the medium for cell culture. The hypoxia tolerance of mice was measured by hypoxia tolerance time and Perl's iron stain. The mRNA and protein expression levels of tuberous sclerosis complex 1 (TSC1), mammalian target of rapamycin (mTOR) and autophagy marker light chain 3 (LC3) were measured by real-time PCR and western blot. The p-mTOR and p-p70S6k proteins were used as markers for mTOR activity. In addition, the role of autophagy was determined by correlating its intensity with hypoxia tolerance in a time-dependent manner. At the same time, the involvement of the TSC1/mTOR pathway in autophagy was also examined through transfection with TSC1 (hamartin) plasmid.

RESULTS

5-Aza-CdR was revealed to increase hypoxia tolerance and induce autophagy, accompanied by an increase in mRNA and protein expression levels of TSC1, reduction in p-mTOR (Ser2448) and p-p70S6k (Thr389) protein levels, and an increase in the ratio of LC3-II/LC3-I in both mouse hippocampus and hippocampal-derived neuronal cell line (HT22). The fluorescence intensity of hamartin was enhanced in the hippocampus of mice exposed to 5-Aza-CdR. Moreover, HT22 cells that over-expressed TSC1 showed more autophagy.

CONCLUSIONS

5-Aza-CdR can increase hypoxia tolerance by inducing autophagy by initiating the TSC1/mTOR pathway.

Synthesis and biological evaluation of dithiocarbamate esters of parthenolide as potential anti-acute myelogenous leukaemia agents

A series of dithiocarbamate esters of parthenolide (PTL) was designed, synthesised, and evaluated for their anti- acute myelogenous leukaemia (AML) activities. The most promising compound 7l showed greatly improved potency against AML progenitor cell line KG1a with IC₅₀ value of 0.7 μM, and the efficacy was 8.7-folds comparing to that of PTL (IC₅₀ = 6.1 μM). Compound 7l induced apoptosis of total primary human AML cells and leukaemia stem cell (LSCs) of primary AML cells while sparing normal cells. Furthermore, 7l suppressed the colony formation of primary human leukaemia cells. Moreover, compound 12, the salt form of 7l, prolonged the lifespan of mice in two patient-derived xenograft models and had no observable toxicity. The preliminary molecular mechanism study revealed that 7l-mediated apoptosis is associated with mitogen-activated protein kinase signal pathway. On the basis of these investigations, we propose that 12 might be a promising drug candidate for ultimate discovery of anti-LSCs drug.

An Effective Concentration of 5-Aza-CdR to Induce Cell Death and Apoptosis in Human Pancreatic Cancer Cell Line through Reactivating RASSF1A and Up-Regulation of Bax Genes

BACKGROUND

Promoter hyper-methylation of tumor suppressor genes is a common event that occurs in cancer. As methylation is a reversible modification, agents capable of reversing an abnormal methylation status should help to combat cancer. 5-Aza-CdR is a DNA methyl-transferase inhibitor. The present study aimed to evaluate the effect of 5-Aza-CdR on the proliferation of human pancreatic cancer cell line (PANC-1) and the expression of RASSF1A and Bax genes.

METHODS

PANC-1 cells were cultured and treated with 5 and 10 µM/L of 5-Aza-CdR for 24, 48, 72, and 96 hours and the percentages of cell viability and apoptosis were measured by MTT and flow cytometry. RASSF1A gene promoter methylation was assessed by methyl-specific primer-PCR (MSP-PCR) and the expression of RASSF1A and Bax genes was measured using quantitative real-time PCR (qPCR). All quantitative data are presented as mean±SD (standard deviation). The one-way analysis of variance (ANOVA) with the LSD post hoc test was performed for statistical analysis using the SPSS software package, version 16.0.

RESULTS

3-[4,5-dimethythiaziazol-2yl]-2,5-diphenyl tetrazoliumbr omide (MTT) assay revealed that 5-Aza-CdR significantly inhibit the growth and proliferation of PANC-1. The flow cytometry results showed over 40% and 70% of early and late apoptotic cells after treatment with 5 and 10 µm/L of 5-Aza-CdR, respectively. MSP-PCR data indicated that the treatment of cells with 10 µm/L 5-Aza-CdR resulted in partial demethylation of RASSF1A gene promoter. qPCR results showed significant re-expression of RASSF1A and up-regulation of Bax genes after 96 hours treatment of cells with 10 µm/L 5-Aza-CdR versus control cells (P<0.01).

CONCLUSION

The result demonstrated that 5 and 10 µM of 5-Aza-CdR induce cell death and apoptosis by epigenetic reactivation of RASSF1A and up-regulation of Bax genes.

A Concise Synthesis of Three Branches Derived from Polysaccharide RN1 and Anti-Pancreatic Cancer Activity Study

RN1, a polysaccharide from flowers of Panax pseudo-ginsieng Wall. Var. notoginseng (Burkill) Hoo &amp; Tseng, is a potential multi-targeting drug candidate for pancreatic cancer treatment. However, the active targeting domain of RN1 is still unknown. Herein, three RN1 derived branches were synthesized via [3+2] or [2+2] strategies, efficiently. Two pentasaccharides, 18 and 27, showed similar inhibition effect on pancreatic cancer BxPC-3 cells to that of RN1 at same concentration. Interestingly, tetrasaccharide 21 potently inhibited gemcitabineresistant cell line Panc-1 at high concentration. These suggest that the branches of RN1 might be the active targeting domain and tetrasaccharide 21 might be a potential leading compound for pancreatic cancer with gemcitabine resistance.

Nimbolide inhibits pancreatic cancer growth and metastasis through ROS-mediated apoptosis and inhibition of epithelial-to-mesenchymal transition

The mortality and morbidity rates of pancreatic cancer are high because of its extremely invasive and metastatic nature. Its lack of symptoms, late diagnosis and chemo–resistance and the ineffective treatment modalities warrant the development of new chemo–therapeutic agents for pancreatic cancer. Agents from medicinal plants have demonstrated therapeutic benefits in various human cancers. Nimbolide, an active molecule isolated from Azadirachta indica, has been reported to exhibit several medicinal properties. This study assessed the anticancer properties of nimbolide against pancreatic cancer. Our data reveal that nimbolide induces excessive generation of reactive oxygen species (ROS), thereby regulating both apoptosis and autophagy in pancreatic cancer cells. Experiments with the autophagy inhibitors 3-methyladenine and chloroquine diphosphate salt and the apoptosis inhibitor z-VAD-fmk demonstrated that nimbolide-mediated ROS generation inhibited proliferation (through reduced PI3K/AKT/mTOR and ERK signaling) and metastasis (through decreased EMT, invasion, migration and colony forming abilities) via mitochondrial-mediated apoptotic cell death but not via autophagy. In vivo experiments also demonstrated that nimbolide was effective in inhibiting pancreatic cancer growth and metastasis. Overall, our data suggest that nimbolide can serve as a potential chemo–therapeutic agent for pancreatic cancer.

Epigenetics and the overhealing wound: the role of DNA methylation in fibrosis

Fibrosis is a progressive and potentially fatal process that can occur in numerous organ systems. Characterised by the excessive deposition of extracellular matrix proteins such as collagens and fibronectin, fibrosis affects normal tissue architecture and impedes organ function. Although a considerable amount of research has focused on the mechanisms underlying disease pathogenesis, current therapeutic options do not directly target the pro-fibrotic process. As a result, there is a clear unmet clinical need to develop new agents. Novel findings implicate a role for epigenetic modifications contributing to the progression of fibrosis by alteration of gene expression profiles.

This review will focus on DNA methylation; its association with fibroblast differentiation and activation and the consequent buildup of fibrotic scar tissue. The potential use of therapies that modulate this epigenetic pathway for the treatment of fibrosis in several organ systems is also discussed.