Acetylcholinesterase and butyrylcholinesterase histochemical activities and tumor cell growth in several brain tumors

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.

Azole derivatives inhibit wildtype butyrylcholinesterase and its common mutants

Azoles, which have been used for antifungal chemotherapy for decades, have recently been of interest for their efficacy against acetylcholinesterase (AChE) and butyrylcholinesterase (BChE). There is little known about the potential of azoles against BChE, however there is none regarding their inhibitory effects against mutants of BChE. In the current study, an azole library of 1-aryl-2-(1H-imidazol-1-yl)ethanol/ethanone oxime esters were tested against AChE and BChE, which yielded derivates more potent than the positive control, galantamine, against both isoforms. Kinetic analyses were performed for wildtype and mutant (A328F and A328Y) inhibition for the two most potent BChE inhibitors, pivalic and 3-bezoylpropanoic acid esters of 2-(1H-imidazol-1-yl)-1-(2-naphthyl)ethanol, which were found to have great affinity to the wildtype and mutant BChE types with Ki values as low as 0.173 ± 0.012 µM. The compounds were identified to show linear competitive or mixed type inhibition. Molecular modeling confirmed these kinetic data and provided further insights regarding molecular basis of BChE inhibition by the active derivatives. Thus, current study suggests new azole derivatives with promising cholinesterase inhibitory effects and reveals the first set of information to promote our understanding for the inhibitory behavior of this class against the mutant BChE forms.

Real-time visualization of butyrylcholinesterase activity using a highly selective and sensitive chemiluminescent probe

Butyrylcholinesterase (BChE), one of the critical human cholinesterases, plays crucial roles in numerous physiological and pathological processes. Accordingly, it is a striking and at the same time challenging target for bioimaging studies. Herein, we developed the first ever example of a 1,2-dixoetane-based chemiluminescent probe (BCC) for monitoring BChE activity in native biological contexts such as living cells and animals. BCC was initially shown to exhibit a highly selective and sensitive turn-on response in its luminescence signal upon reacting with BChE in aqueous solutions. Later, BCC was utilized to image endogenous BChE activity in normal and cancer cell lines. It was also shown through inhibition experiments that BChE can detect fluctuations of BChE levels successfully. In vivo imaging ability of BCC was demonstrated in healthy and tumor-bearing mice models. BCC enabled us to visualize the BChE activity in different regions of the body. Furthermore, it was successfully employed to monitor tumors derived from neuroblastoma cells with a very high signal to noise ratio. Thus, BCC appears as a highly promising chemiluminescent probe, which can be used to further understand the contribution of BChE to regular cellular processes and the formation of diseased states.

Multifarious Functions of Butyrylcholinesterase in Neuroblastoma: Impact of BCHE Deletion on the Neuroblastoma Growth In Vitro and In Vivo

The physiological functions of butyrylcholinesterase (BChE) and its role in malignancy remain unexplained. Our studies in children newly diagnosed with neuroblastoma indicated that BChE expressions is proportional to MYCN amplification suggesting that pathogenesis of high-risk disease may be related to the persistent expression of abnormally high levels of tumor-associated BChE. BChE-deficient neuroblastoma cells (KO [knockout]) were produced from MYCN -amplified BE(2)-C cells (WT [wild-type]) by the CRISPR-Cas9 targeted disruption of the BCHE locus. KO cells have no detectable BChE activity. The compensatory acetylcholinesterase activity was not detected. The average population doubling time of KO cells is 47.0±2.4 hours, >2× longer than WT cells. Reduced proliferation rates of KO cells were accompanied by the loss of N-Myc protein and a significant deactivation of tyrosine kinase receptors associated with the aggressive neuroblastoma phenotype including Ros1, TrkB, and Ltk. Tumorigenicity of WT and KO cells in male mice was essentially identical. In contrast, KO xenografts in female mice were very small (0.37±0.10 g), ~3× smaller compared with WT xenografts (1.11±0.30 g). Unexpectedly, KO xenografts produced changes in plasma BChE similarly to WT tumors but lesser in magnitude. The disruption of BCHE locus in MYCN -amplified neuroblastoma cells decelerates proliferation and produces neuroblastoma cells that are less aggressive in female mice.

Lichen-Derived Compounds and Extracts as Biologically Active Substances with Anticancer and Neuroprotective Properties

Lichens are a source of chemical compounds with valuable biological properties, structurally predisposed to penetration into the central nervous system (CNS). Hence, our research aimed to examine the biological potential of lipophilic extracts of Parmelia sulcata, Evernia prunastri, Cladonia uncialis, and their major secondary metabolites, in the context of searching for new therapies for CNS diseases, mainly glioblastoma multiforme (GBM). The extracts selected for the study were standardized for their content of salazinic acid, evernic acid, and (−)-usnic acid, respectively. The extracts and lichen metabolites were evaluated in terms of their anti-tumor activity, i.e., cytotoxicity against A-172 and T98G cell lines and anti-IDO1, IDO2, TDO activity, their anti-inflammatory properties exerted by anti-COX-2 and anti-hyaluronidase activity, antioxidant activity, and anti-acetylcholinesterase and anti-butyrylcholinesterase activity. The results of this study indicate that lichen-derived compounds and extracts exert significant cytotoxicity against GBM cells, inhibit the kynurenine pathway enzymes, and have anti-inflammatory properties and weak antioxidant and anti-cholinesterase properties. Moreover, evernic acid and (−)-usnic acid were shown to be able to cross the blood-brain barrier. These results demonstrate that lichen-derived extracts and compounds, especially (−)-usnic acid, can be regarded as prototypes of pharmacologically active compounds within the CNS, especially suitable for the treatment of GBM.

Imidazopyridazine Acetylcholinesterase Inhibitors Display Potent Anti-Proliferative Effects in the Human Neuroblastoma Cell-Line, IMR-32

Imidazo[1,2-b]pyridazine compounds are a new class of promising lead molecules to which we have incorporated polar nitro and amino moieties to increase the scope of their biological activity. Two of these substituted 3-nitro-6-amino-imidazo[1,2-b]pyridazine compounds (5c and 5h) showed potent acetylcholinesterase (AChE) inhibitory activity (IC₅₀ 40–50 nM), which we have previously reported. In this study, we wanted to test the biological efficacy of these compounds. Cytotoxicity assays showed that compound 5h mediated greater cell death with over 43% of cells dead at 100 μM and activation of caspase 3-mediated apoptosis. On the other hand, compound 5c mediated a dose-dependent decrease in cell proliferation. Both compounds showed cell cycle arrest in the G₀/G₁ phase and reduced cellular ATP levels leading to activation of adenosine monophosphate-activated protein kinase (AMPK) and enhanced mitochondrial oxidative stress. It has to be noted that all these effects were observed at doses beyond 10 μM, 200-fold above the IC₅₀ for AChE inhibition. Both compounds also inhibited bacterial lipopolysaccharide-mediated cyclooxygenase-2 and nitric oxide release in primary rat microglial cells. These results suggested that the substituted imidazo (1,2-b) pyridazine compounds, which have potent AChE inhibitory activity, were also capable of antiproliferative, anti-migratory, and anti-inflammatory effects at higher doses.

Acetylcholinesterase and human cancers

The enzyme acetylcholinesterase (AChE) is a serine hydrolase whose primary function is to degrade acetylcholine (ACh) and terminate neurotransmission. Apart from its role in synaptic transmission, AChE has several "non-classical" functions in non-neuronal cells. AChE is involved in cellular growth, apoptosis, drug resistance pathways, response to stress signals and inflammation. The observation that the functional activity of AChE is altered in human tumors (relative to adjacent matched normal tissue) has raised several intriguing questions about its role in the pathophysiology of human cancers. Published reports show that AChE is a vital regulator of oncogenic signaling pathways involving proliferation, differentiation, cell-cell adhesion, migration, invasion and metastasis of primary tumors. The objective of this book chapter is to provide a comprehensive overview of the contributions of the AChE-signaling pathway in the growth of progression of human cancers. The AChE isoforms, AChE-T, AChE-R and AChE-S are robustly expressed in human cancer cell lines as well in human tumors (isolated from patients). Traditionally, AChE-modulators have been used in the clinic for treatment of neurodegenerative disorders. Emerging studies reveal that these drugs could be repurposed for the treatment of human cancers. The discovery of potent, selective AChE ligands will provide new knowledge about AChE-regulatory pathways in human cancers and foster the hope of novel therapies for this disease.

Effect of Proline on Cell Death, Cell Cycle, and Oxidative Stress in C6 Glioma Cell Line

Since proline metabolism has been implicated to play an underlying role in apoptotic signaling and cancer, and hyperprolinemic patients present susceptibility to tumors development, this study investigated the effect of proline on cell death, cell cycle, antioxidant enzymes activities, and immunocontent/activity of proteins involved in cell death/survival signaling pathways in C6 glioma cells. C6 cells were incubated with proline (0-5 mM) for 1 h, 24 h, 48 h, 72 h, or 7 days. Proline in high concentrations slightly decreased LDH release, and no cytotoxic effect was seen by Annexin-PI staining. Superoxide dismutase and catalase activities were increased by proline (1 mM) after 72 h, suggesting an increase in reactive species levels. Acetylcholinesterase activity was inhibited by proline at 1, 3, and 5 mM. The cell cycle progression was not altered. Results from Western blot analyses showed that proline at 1 mM after 72 h increased p-NF-ĸB and decreased acetylcholinesterase immunocontent but did not altered AKT, p-AKT, GSK3β, and p-GSK3β. Taken together, the data suggest that high proline levels seems to favor the signaling pathways towards cell proliferation, since acetylcholinesterase, which may act as tumor suppressor, is inhibited by proline. Also, p-NF-κB is increased by proline treatment and its activation is related to tumor cell proliferation and cellular response to oxidants. Proline also induced oxidative stress, but it appears to be insufficient to induce a significant change in cell cycle progression. These data may be related, at least in part, to the increased susceptibility to tumor development in hyperprolinemic individuals.

Early indicators of primary brain tumours: a population-based study with 10 years' follow-up

BACKGROUND AND PURPOSE

To improve diagnoses of primary brain tumours, knowledge about early indicators is needed. Nationwide Danish health registries were used to conduct a population-based case-control study including all persons diagnosed with a primary brain tumour between 2005 and 2014 in Denmark.

METHODS

All 5135 adults diagnosed with a primary brain tumour in the Danish Cancer Registry were matched to 19 572 general population comparisons from the Danish Civil Registration System. Conditional logistic regression analyses were applied to estimate age- and multivariable-adjusted odds ratios (ORs) for the occurrence of a primary brain tumour up to 10 years after hospital diagnoses or prescription of medications related to nervous system diseases and mental and behavioural disorders.

RESULTS

Increased odds for primary brain tumour after nervous system diseases and mental and behavioural disorders manifested up to 10 years before tumour diagnosis were found. Increased odds were seen especially for hospital contacts for inflammatory nervous system diseases [OR 11.3; 95% confidence interval (CI) 6.5-19.7], epilepsy (OR 9.0; 95% CI 7.6-10.7) and antiepileptic medications (OR 3.6; 95% CI 3.2-4.0), whilst antidementia medications provided a strong, protective association for primary brain tumours (OR 0.5; 95% CI 0.3-0.8).

CONCLUSIONS

Sub-groups of patients diagnosed with or being prescribed certain medications targeting nervous system diseases and mental and behavioural disorders may be at increased risk of being diagnosed with a primary brain tumour. Further studies should disentangle the potential underlying common pathogenetic pathways. The results are important for the development of systematic clinical approaches to ensure early diagnosis of primary brain tumours.

Exposure to radio-frequency electromagnetic waves alters acetylcholinesterase gene expression, exploratory and motor coordination-linked behaviour in male rats

Humans in modern society are exposed to an ever-increasing number of electromagnetic fields (EMFs) and some studies have demonstrated that these waves can alter brain function but the mechanism still remains unclear. Hence, this study sought to investigate the effect of 2.5 Ghz band radio-frequency electromagnetic waves (RF-EMF) exposure on cerebral cortex acetylcholinesterase (AChE) activity and their mRNA expression level as well as locomotor function and anxiety-linked behaviour in male rats. Animals were divided into four groups namely; group 1 was control (without exposure), group 2-4 were exposed to 2.5 Ghz radiofrequency waves from an installed WI-FI device for a period of 4, 6 and 8 weeks respectively. The results revealed that WiFi exposure caused a significant increase in anxiety level and affect locomotor function. Furthermore, there was a significant decrease in AChE activity with a concomitant increase in AChE mRNA expression level in WiFi exposed rats when compared with control. In conclusions, these data showed that long term exposure to WiFi may lead to adverse effects such as neurodegenerative diseases as observed by a significant alteration on AChE gene expression and some neurobehavioral parameters associated with brain damage.

Estimation of Serum Butyryl Cholinesterase in Patients with Oral Squamous Cell Carcinoma: A Cross-Sectional Study

INTRODUCTION

Oral cancer is a major global threat to public health. It is one of the most common causes of mortality and morbidity in the modern era. Oral Squamous Cell Carcinoma (OSCC) accounts for over 90% of the malignancies involving the oral cavity. The enzyme- Butyryl Cholinesterase (BChE) is proposed to have a role in cell proliferation, cell adhesion, cell differentiation, apoptosis and tumorigenesis. Few studies have been conducted for understanding the significance of serum BChE as a biomarker in oral cancer patients; however literature available is insufficient to arrive at a conclusion. There is a need of a simple, rapid, convenient, inexpensive and reliable biomarker of oral cancer. So, the present study is an attempt to estimate the level of BChE in oral cancer, prior to definitive therapy.

AIM

To estimate and compare the serum BChE levels in patients with OSCC with age and gender matched healthy controls.

MATERIALS AND METHODS

The study comprised of 80 subjects, of which 40 biopsy proven OSCC patients of either sex were selected as cases and 40 healthy, age and gender matched subjects as controls. Estimation of serum BChE levels was done by colorimetric method using RANDOX RX Imola Auto-Analyzer. The statistical analysis between the OSCC group and the control group were done using unpaired t-test. Comparison between serum BChE levels and TNM stages of OSCC were done using Kruskal-Wallis Test. Comparison between serum BChE levels and histopathological grades of OSCC were done using Mann-Whitney U Test.

RESULTS

There was statistically highly significant decrease in the mean serum BChE levels in the OSCC group compared to the control group (p<0.001). It was revealed that the serum BChE levels were further decreased in moderately differentiated squamous cell carcinoma than well differentiated squamous cell carcinoma and the difference was statistically significant (p <0.05).

CONCLUSION

The decrease in the serum BChE level demonstrates that it as a simple, rapid, convenient, inexpensive and reliable biomarker for oral cancer. Our findings support the concept of role of BChE in apoptosis, cell proliferation, differentiation and its related link in the pathophysiology of oral cancer.

Slowing of M1 oscillations in brain tumor patients in resting state and during movement

OBJECTIVE

Brain tumors may severely disrupt the structure and function of the brain. While abnormal low-frequency activity can be found around tumor borders, disrupted structural connectivity may also impinge on neural activity in distant brain regions and other frequency bands. We investigated how glioma in patients with normal motor functioning affects activity in primary motor areas (M1).

METHODS

Using magnetoencephalography in 12 patients with unilateral glioma located around the central sulcus, we studied activity in bilateral M1s in resting state and during movement with focus on motor-related mu (8-12Hz) and beta rhythms (15-30Hz). Principal component analysis served to test for differences in spectral content.

RESULTS

A shift was found towards lower frequencies for M1 in the tumor hemisphere compared to M1 in the healthy hemisphere, caused by an increase in mu and decrease in beta power. This pattern was observed both in resting state and during movement.

CONCLUSIONS

This 'slowing' of brain oscillations in M1 resembles findings in patients with monohemispheric stroke and Parkinson's disease. A loss of intra-cortical connectivity may account for these findings, possibly supplemented by tumor-induced changes in neurotransmitter systems.

SIGNIFICANCE

Motor functioning may be unaffected by a spectral shift of mu and beta oscillations.

Acetylcholinesterase, a key prognostic predictor for hepatocellular carcinoma, suppresses cell growth and induces chemosensitization

Acetylcholinesterase (ACHE) plays important roles in the cholinergic system, and its dysregulation is involved in a variety of human diseases. However, the roles and implications of ACHE in hepatocellular carcinoma (HCC) remain elusive. Here we demonstrate that ACHE was significantly down-regulated in the cancerous tissues of 69.2% of HCC patients, and the low ACHE expression in HCC was correlated with tumor aggressiveness, an elevated risk of postoperative recurrence, and a low survival rate. Both the recombinant ACHE protein and the enhanced expression of ACHE significantly inhibited HCC cell growth in vitro and tumorigenicity in vivo. Further study showed that ACHE suppressed cell proliferation via its enzymatic activity of acetylcholine catalysis and degradation. Moreover, ACHE could inactivate mitogen-activated protein kinase and phosphatidyl inositol-3'-phosphate kinase/protein kinase B pathways in HCC cells and thereby increase the activation of glycogen synthase kinase 3β and lead to β-catenin degradation and cyclin D1 suppression. In addition, increased ACHE expression could remarkably sensitize HCC cells to chemotherapeutic drugs (i.e., adriamycin and etoposide).

CONCLUSION

For the first time, we describe the function of ACHE as a tumor growth suppressor in regulating cell proliferation, the relevant signaling pathways, and the drug sensitivity of HCC cells. ACHE is a promising independent prognostic predictor for HCC recurrence and the survival of HCC patients. These findings provide new insights into potential strategies for drug discovery and improved HCC treatment.

Counter-regulation of cholinesterases: differential activation of PKC and ERK signaling in retinal cells through BChE knockdown

The ubiquitous cholinesterase (ChE) enzymes, functioning in the termination of acetylcholine mediated neural transmission, are also reported to have additional functions. Through application of siRNAs against butyrylcholinesterase (BChE) in R28 cells, a retinal cell line with pluripotent properties, a counter-regulation between ChEs was revealed. BChE knock down resulted in an up-regulation of not only acetylcholinesterase (AChE), but also altered the signaling status of PKC and ERK. Knockdown of BChE modified ERK signaling most notably through ERK1/2 proteins, together with the transcription activator P90RSK1 and c-fos. Stimulation of the R28 cell line by forskolin revealed that ChEs are involved in an intricate cross talk between different signaling pathways. Forskolin-stimulated R28 cells displayed a robust cholinergic response, as detected by both electrophysiology and ChE expression, and changed the activation status of PKC/ERK signaling pathways. The findings in R28 cells show that ChE expressions are inversely co-regulated and act through the transcription factors c-fos and P90RSK1. Since R28 cells have the capacity to differentiate into different cell types through stimulation of signaling pathways, ChEs are likely to be associated with cell fate determination, rather than just terminating cholinergic responses.

Complex regulation of acetylcholinesterase gene expression in human brain tumors

To study the regulation of acetylcholinesterase (AChE) gene expression in human brain tumors, 3' splice variants of AChE mRNA and potentially relevant transcription factor mRNAs were labeled in primary astrocytomas and melanomas. AChE-S and AChE-R mRNA, as well as Runx1/AML1 mRNA accumulated in astrocytomas in correlation with tumor aggressiveness, but neither HNF3beta nor c-fos mRNA was observed in melanoma and astrocytomas. Immunohistochemistry demonstrated nuclear Runx1/AML1 and cellular AChE-S and AChE-R in melanomas, however, only AChE-S, and not the secreted AChE-R variant, was retained in astrocyte tumor cells. Runx1/AML1 revealed weak linkage with ACHE promoter sequences, yet enhanced ACHE gene expression in co-transfected COS1 cells. The p300 co-activator and the ACHE promoter's distal enhancer facilitated this effect, which was independent of much of the Runx1/AML1 trans-activation domain. Surprisingly, GASP, a fusion product of green fluorescence protein (GFP) and ASP(67), a peptide composed of the 67 C-terminal amino acid residues of AChE-S, localized to COS1 cell nuclei. However, GARP, the corresponding fusion product of GFP with a peptide having the 51 C-terminal residues of AChE-E or GFP alone, remained cytoplasmic. Runx1/AML1 exhibited improved nuclear retention in GASP-expressing COS1 cells, suggesting modulated nuclear localization processes. Together, these findings reveal brain tumor-specific regulation of both expression and cellular retention of variant ACHE gene products.