Anticancer drugs induce hypomethylation of the acetylcholinesterase promoter via a phosphorylated-p38-DNMT1-AChE pathway in apoptotic hepatocellular carcinoma cells

Changes in the Acetylcholinesterase Enzymatic Activity in Tumor Development and Progression

Acetylcholinesterase is a well-known protein because of the relevance of its enzymatic activity in the hydrolysis of acetylcholine in nerve transmission. In addition to the catalytic action, it exerts non-catalytic functions; one is associated with apoptosis, in which acetylcholinesterase could significantly impact the survival and aggressiveness observed in cancer. The participation of AChE as part of the apoptosome could explain the role in tumors, since a lower AChE content would increase cell survival due to poor apoptosome assembly. Likewise, the high Ach content caused by the reduction in enzymatic activity could induce cell survival mediated by the overactivation of acetylcholine receptors (AChR) that activate anti-apoptotic pathways. On the other hand, in tumors in which high enzymatic activity has been observed, AChE could be playing a different role in the aggressiveness of cancer; in this review, we propose that AChE could have a pro-inflammatory role, since the high enzyme content would cause a decrease in ACh, which has also been shown to have anti-inflammatory properties, as discussed in this review. In this review, we analyze the changes that the enzyme could display in different tumors and consider the different levels of regulation that the acetylcholinesterase undergoes in the control of epigenetic changes in the mRNA expression and changes in the enzymatic activity and its molecular forms. We focused on explaining the relationship between acetylcholinesterase expression and its activity in the biology of various tumors. We present up-to-date knowledge regarding this fascinating enzyme that is positioned as a remarkable target for cancer treatment.

Long non-coding RNA HOTTIP exerts an oncogenic function by regulating HOXA13 in nasopharyngeal carcinoma

BACKGROUND

The long non-coding RNA HOXA transcript at the distal tip (HOTTIP) and homeobox A13 (HOXA13) have been identified as oncogenes that play a pivotal role in tumorigenesis. However, their specific mechanisms of action in nasopharyngeal carcinoma (NPC) progression remain unclear.

METHODS AND RESULTS

In the present study, RT-qPCR was employed to quantify RNA expression in NPC cells and tissues. Flow cytometry, MTT, CCK8 and colony formation assays were utilized to assess cell apoptosis and proliferation. Transwell assay was conducted to evaluate migration and invasion while Western blotting was performed for protein expression analysis. Our findings revealed that the expression of HOTTIP was significantly upregulated in NPC cell lines. Inhibition of HOTTIP could induce apoptosis and suppress proliferation, clonogenicity, invasion and metastasis in NPC cells. Knockdown of HOTTIP led to downregulation of HOXA13 expression, which subsequently inhibited the proliferation and metastasis in NPC cells. The inhibitory effects on cell proliferation and metastasis caused by HOTTIP silencing were rescued by HOXA13 overexpression. Additionally, there was a significant positive correlation between HOTTIP and HOXA13, which were found to be elevated in NPC tissues compared to normal tissues.

CONCLUSIONS

We have determined that LncRNA HOTTIP facilitates tumorigenesis by modulating the expression of HOXA13 in NPC cells. Targeting HOTTIP/HOXA13 may be a promising therapeutic strategy for NPC.

The multiple biological roles of the cholinesterases

It is tacitly assumed that the biological role of acetylcholinesterase is termination of synaptic transmission at cholinergic synapses. However, together with its structural homolog, butyrylcholinesterase, it is widely distributed both within and outside the nervous system, and, in many cases, the role of both enzymes remains obscure. The transient appearance of the cholinesterases in embryonic tissues is especially enigmatic. The two enzymes' extra-synaptic roles, which are known as 'non-classical' roles, are the topic of this review. Strong evidence has been presented that AChE and BChE play morphogenetic roles in a variety of eukaryotic systems, and they do so either by acting as adhesion proteins, or as trophic factors. As trophic factors, one mode of action is to directly regulate morphogenesis, such as neurite outgrowth, by poorly understood mechanisms. The other mode is by regulating levels of acetylcholine, which acts as the direct trophic factor. Alternate substrates have been sought for the cholinesterases. Quite recently, it was shown that levels of the aggression hormone, ghrelin, which also controls appetite, are regulated by butyrylcholinesterase. The rapid hydrolysis of acetylcholine by acetylcholinesterase generates high local proton concentrations. The possible biophysical and biological consequences of this effect are discussed. The biological significance of the acetylcholinesterases secreted by parasitic nematodes is reviewed, and, finally, the involvement of acetylcholinesterase in apoptosis is considered.

A novel strategy for the diagnosis, prognosis, treatment, and chemoresistance of hepatocellular carcinoma: DNA methylation

The cancer mortality rate of hepatocellular carcinoma (HCC) is the second highest in the world and the therapeutic options are limited. The incidence of this deadly cancer is rising at an alarming rate because of the high degree of resistance to chemo- and radiotherapy, lack of proper, and adequate vaccination to hepatitis B, and lack of consciousness and knowledge about the disease itself and the lifestyle of the people. DNA methylation and DNA methylation-induced epigenetic alterations, due to their potential reversibility, open the access to develop novel biomarkers and therapeutics for HCC. The contribution to these epigenetic changes in HCC development still has not been thoroughly summarized. Thus, it is necessary to better understand the new molecular targets of HCC epigenetics in HCC diagnosis, prevention, and treatment. This review elaborates on recent key findings regarding molecular biomarkers for HCC early diagnosis, prognosis, and treatment. Currently emerging epigenetic drugs for the treatment of HCC are summarized. In addition, combining epigenetic drugs with nonepigenetic drugs for HCC treatment is also mentioned. The molecular mechanisms of DNA methylation-mediated HCC resistance are reviewed, providing some insights into the difficulty of treating liver cancer and anticancer drug development.

Hypoxia induces hypomethylation of the HMGB1 promoter via the MAPK/DNMT1/HMGB1 pathway in cardiac progenitor cells

Apoptosis is involved in the death of cardiac progenitor cells (CPCs) after myocardial infarction (MI) in the heart. The loss of CPCs results in infarct scar and further deterioration of the heart function. Though stem cell-based therapy provides an effective approach for heart function recovery after MI, the retention of CPCs in the infarcted area of the heart is the main barrier that limits its promising therapy. Therefore, the underlying mechanisms of CPC apoptosis in hypoxia are important for the development of new therapeutic targets for MI patients. In this work, we found that the expression of high-mobility group box 1(HMGB1) was upregulated in CPCs under hypoxia conditions. Further study demonstrated that HMGB1 was regulated by DNA methyltransferases 1 (DNMT1) via changing the methylation state of CpGs in the promoter of HMGB1 in CPCs during hypoxia process. Additionally, mitogen-activated protein kinase (MAPK) signaling pathway was found to be involved in regulating DNMT1/HMGB1-mediated CPC apoptosis in hypoxia process. In conclusion, our findings demonstrate a novel regulatory mechanism for CPC apoptosis and proliferation under hypoxia conditions, which may provide a new therapeutic approach for MI patients.

Zebularine Promotes Hepatic Differentiation of Rabbit Bone Marrow Mesenchymal Stem Cells by Interfering with p38 MAPK Signaling

Demethylating agent zebularine is reported to be capable of inducing differentiation of stem cells by activation of methylated genes, though its function in hepatocyte differentiation is unclear. p38 signal pathway is involved in differentiation of hepatocytes and regulating of DNA methyltransferases 1 (DNMT1) expression. However, little is known about the impact of zebularine on bone marrow mesenchymal stem cells (BMMSCs) and p38 signaling during hepatic differentiation. The present study investigated the effects of zebularine on hepatic differentiation of rabbit BMMSCs, as well as the role of p38 on DNMT1 and hepatic differentiation, with the aim of developing a novel strategy for improving derivation of hepatocytes. BMMSCs were treated with zebularine at concentrations of 10, 20, 50, and 100 μM in the presence of hepatocyte growth factor; changes in the levels of hepatic-specific alpha-fetoprotein and albumin were detected and determined by RT-PCR, WB, and immunofluorescence staining. Expression of DNMT1 and phosphorylated p38 as well as urea production and ICG metabolism was also analyzed. Zebularine at concentrations of 10, 20, and 50 μM could not affect cell viability after 48 h. Zebularine treatment leads to an inhibition of DNMT activity and increase of hepatic-specific proteins alpha-fetoprotein and albumin in BMMSCs in vitro; zebularine addition also induced expression of urea production of and ICG metabolism. p38 signal was activated in BMMSCs simulated with HGF; inhibition of p38 facilitated the synthesis of DNMT1 and albumin in cells. Zebularine restrained DNMT1 and phosphorylated p38 which were induced by HGF. Therefore, this study demonstrated that treatment with zebularine exhibited terminal hepatic differentiation of BMMSCs in vitro in association with hepatocyte growth factor; p38 pathway at least partially participates in zebularine-induced hepatic differentiation of rabbit BMMSCs.

Activation of PAR4 Upregulates p16 through Inhibition of DNMT1 and HDAC2 Expression via MAPK Signals in Esophageal Squamous Cell Carcinoma Cells

A previous study showed that a downexpression of protease-activated receptor 4 (PAR4) is associated with the development of esophageal squamous cell carcinoma (ESCC). In this study, we explored the relationship between PAR4 activation and the expression of p16, and elucidated the underlying mechanisms in PAR4 inducing the tumor suppressor role in ESCC. ESCC cell lines (EC109 and TE-1) were treated with PAR4-activating peptide (PAR4-AP). Immunohistochemistry for DNA methyltransferase 1 (DNMT1) and histone deacetylase 2 (HDAC2) was performed in 26 cases of ESCC tissues. We found that DNMT1 and HDAC2 immunoreactivities in ESCC were significantly higher than those in adjacent noncancerous tissues. PAR4 activation could suppress DNMT1 and HDAC2, as well as increase p16 expressions, whereas silencing PAR4 dramatically increased HDAC2 and DNMT1, as well as reduced p16 expressions. Importantly, the chromatin immunoprecipitation-PCR (ChIP-PCR) data indicated that treatment of ESCC cells with PAR4-AP remarkably suppressed DNMT1 and HDAC2 enrichments on the p16 promoter. Furthermore, we demonstrated that activation of PAR4 resulted in an increase of p38/ERK phosphorylation and activators for p38/ERK enhanced the effect of PAR4 activation on HDAC2, DNMT1, and p16 expressions, whereas p38/ERK inhibitors reversed these effects. Moreover, we found that activation of PAR4 in ESCC cells significantly inhibited cell proliferation and induced apoptosis. These findings suggest that PAR4 plays a potential tumor suppressor role in ESCC cells and represents a potential therapeutic target of this disease.

Clarifying of the potential mechanism of Sinisan formula for treatment of chronic hepatitis by systems pharmacology method

Chronic hepatitis is a general designation class of diseases, which results in different degrees of liver necrosis and inflammatory reaction, followed by liver fibrosis, may eventually develop into cirrhosis. However, the molecular pathogenesis of chronic hepatitis is too complex to elucidate. Herbal medicines, featured with multiple targets and compounds, have long displayed therapeutic effect in treating chronic hepatitis, though their molecular mechanisms of contribution remain indistinct. This research utilized the network pharmacology to confirm the molecular pathogenesis of chronic hepatitis through providing a comprehensive analysis of active chemicals, drug targets and pathways' interaction of Sinisan formula for treating chronic hepatitis. The outcomes showed that 80 active ingredients of Sinisan formula interacting with 91 therapeutic proteins were authenticated. Sinisan formula potentially participates in immune modulation, anti-inflammatory and antiviral activities, even has regulating effects on lipid metabolism. These mechanisms directly or indirectly are involved in curing chronic hepatitis by an interaction way. The network pharmacology based analysis demonstrated that Sinisan has multi-scale curative activity in regulating chronic hepatitis related biological processes, which provides a new potential way for modern medicine in the treatment of chronic diseases.

Missing in metastasis B, regulated by DNMT1, functions as a putative cancer suppressor in human lung giant-cell carcinoma

Missing in metastasis B (MIM-B) has been widely reported to inhibit cancer cell invasion and proliferation in a variety of human cancers. However, the functions of MIM-B in lung cancers are still controversial. In addition, the mechanisms and regulation of MIM-B are poorly understood. In the present study, we found that the invasion level of 95C human lung giant-cell carcinoma cells was elevated when MIM-B was knocked down, while the invasion of 95D was suppressed when MIM-B was overexpressed, proving that MIM-B suppresses human lung giant-cell carcinoma cell invasion, which is similar to its function in most cancers. Furthermore, we reported that an increase in DNA methylation density in the promoter of MIM-B by DNA methyltransferase 1 (DNMT1) is correlated with the silencing of MIM-B expression and the high metastasis of 95D human lung giant-cell carcinoma cell line. Taken together, MIM-B, which is regulated by DNMT1 through DNA methylation, is a putative cancer suppressor in human lung giant-cell carcinoma.

Cholinergic system and cell proliferation

The cholinergic system, comprising acetylcholine, the proteins responsible for acetylcholine synthesis and release, acetylcholine receptors and cholinesterases, is expressed by most human cell types. Acetylcholine is a neurotransmitter, but also a local signalling molecule which regulates basic cell functions, and cholinergic responses are involved in cell proliferation and apoptosis. So, activation of nicotinic and muscarinic receptors has a proliferative and anti-apoptotic effect in many cells. The content of choline acetyltransferase, acetylcholine receptors and cholinesterases is altered in many tumours, and cholinesterase content correlates with patient survival in some cancers. During apoptosis, acetylcholinesterase is induced and appears in the nuclei. Acetylcholinesterase participates in the regulation of cell proliferation and apoptosis through hydrolysis of acetylcholine and by other catalytic and non catalytic mechanisms, in a variant-specific manner. This review gathers information on the role of cholinergic system and specially acetylcholinesterase in cell proliferation and apoptosis.