Role of DNA Methylation in Mechanisms of Anterograde Amnesia

Previously, we found that impairment of conditioned food aversion memory consolidation or reconsolidation in snails by NMDA glutamate receptors antagonists led to the induction of amnesia changing over time. In particular, at the later amnesia stages (10 or more days), repeated aversion training for the same food type that was used in the initial training did not induce long-term memory formation. In these animals, long-term aversion memory for a new food type was formed. We characterized this amnesia as specific anterograde amnesia. In the present work, using DNA methyltransferases (DNMT) inhibitors, the DNA methylation processes role in mechanisms of anterograde amnesia and recovery from amnesia was investigated. It was found that in amnestic animals, DNMT inhibitor administration before or after repeated training led to the rapid long-term conditioned food aversion memory formation. It depended on proteins and mRNA synthesis at certain time windows. Thus, protein synthesis inhibitors administration before or immediately after repeated training, or RNA synthesis inhibitor injection after training, prevented memory formation induced by the DNMT inhibitor. The effects of DNMT inhibitors were specific for certain conditioned stimulus, since these inhibitors did not affect amnestic animals training for a new food stimulus. DNMT inhibition during second training removed blockade of these genes' expression, opening up access to them for transcription factors synthesized during training. Thus, this work was the first to study the molecular mechanisms of anterograde amnesia, as well as memory recovery, which can be important for search for pharmacological correction of this neuropsychic pathology.

The Identification of Novel Epigenetic Therapies for ALK-Driven Haematological Malignancies

Introduction Through conserved signalling pathways, Anaplastic Lymphoma Kinase (ALK) is well-described in driving haematological malignancies including Anaplastic Large Cell Lymphoma (ALCL) and Diffuse Large B-Cell Lymphoma (DLBCL) and as such presents itself as an amenable therapeutic target. Hence, directed therapeutics (ALK tyrosine kinase inhibitors; TKI) are being used in the treatment of ALK-driven cancers. Unfortunately, findings in the clinic and clinical research studies have taught us that resistance to ALK inhibitors can develop through the activation of ALK signalling bypass tracks. As such there is a need for the development of novel front-line, dual-combination, as well as second-line therapies. Methods A large-scale epigenetic targeted drug library consisting of approximately 300 FDA-approved drugs and novel agents was applied to a number of cell lines representing ALK-driven haematological malignancies: ALCL cell lines (DEL, JB-6, KARPAS-299, SU-DHL-1, SUP-M2) and the DLBCL cell line LM-1. Drugs which caused a >75% decrease in cell viability were classified as 'candidate drugs' and studied further. Results Several of the validated drugs have previously been used/trialled in the clinic for the treatment of various cancers, e.g. aurora kinase (XL-228), topoisomerase (Mitoxantrone HCl) and HDAC (Romidepsin) inhibitors - these functioned as internal controls for the drug screens. However, an assortment of novel drugs was also identified that have not previously been described in the context of the treatment of ALK-driven haematological malignancies; including the FLT3 inhibitor KW2449 which caused a >75% decrease in viability in all the tested cell lines and as such may serve as a novel front line therapy. In addition, a novel DNA methyltransferase (DNMT) inhibitor was identified which is efficacious and resulted in a >90% decrease in viability in all cell lines treated across both disease entities. Furthermore, we investigated the combinatorial potential of the identified DNMT inhibitor with ALK TKIs such as Brigatinib and observed the inhibitor acting synergistically (as per Bliss-Independence calculations) resulting in a further decrease in cell viability. Several cell lines that are resistant to ALK TKIs were also assessed for their sensitivity to the DNMT inhibitor and were shown to be susceptible to this drug, as demonstrated by a significant decrease in cell viability. Figure 1: (A) Viability following drug screen in a representative cell line. Those drugs which led to a >75% change in viability were taken forward for validation, as shown in (B). (C) Candidate drugs identified for each of the cell lines tested, grouped according to their molecular target. Conclusion In conclusion, an epigenetic drug library has been employed to identify novel therapeutic agents for the treatment of ALK-driven haematological malignancies including ALCL and DLBCL. Data reveal a potent inhibitor of DNA methylation as a candidate drug that suppresses the growth of ALK-driven malignancies both alone and in combination with ALK TKIs. Significantly, this identified drug also inhibits the growth of cell lines resistant to directed therapeutics such as ALK TKIs suggesting it has potential clinical use. Disclosures No relevant conflicts of interest to declare.

Anti-leukemic activity of DNA methyltransferase inhibitor procaine targeted on human leukaemia cells

Chromatin remodeling in DNA is fundamental to gene expression, DNA replication and repair processes. Methylation of promoter regions of tumor-suppressor genes and histone deacetylation leads to gene silencing and transcriptionally repressive chromatin. For the past few decades DNA methylation agents became very attractive as the targets for cancer therapy. The purpose of this work was to examine the effects of DNMT inhibitor procaine on growth inhibition, apoptosis and differentiation of human leukaemia cells. The changes in expression of genes, proteins and histone modifications caused by procaine were evaluated under different treatments. We demonstrated that procaine arrests growth of human leukaemia cells and in combination with all-trans retinoic acid (ATRA) induces cancer cell differentiation. Procaine causes reduction of expression of DNA methyltransferases as well. The treatment of human leukaemia cells with procaine increase the expression of molecules associated with differentiation (CD11b, E-cadherin, G-CSF) and apoptosis (PPARγ). Moreover, the examined DNMT inhibitor enhances certain gene transcription activation via chromatin remodelling – the changes in histone H3K4(Me)3 and H3K9Ac/S10P modifications were detected. Our results suggest, that DNMT inhibitor – procaine, can be used for further investigations on epigenetic differentiation therapy of leukaemia cells especially when used in combination with retinoic acid.