Inhibitors of the Oncogenic PA2G4-MYCN Protein-Protein Interface.

MYCN is a major oncogenic driver for neuroblastoma tumorigenesis, yet there are no direct MYCN inhibitors. We have previously identified PA2G4 as a direct protein-binding partner of MYCN and drive neuroblastoma tumorigenesis. A small molecule known to bind PA2G4, WS6, significantly decreased tumorigenicity in TH-MYCN neuroblastoma mice, along with the inhibition of PA2G4 and MYCN interactions. Here, we identified a number of novel WS6 analogues, with 80% structural similarity, and used surface plasmon resonance assays to determine their binding affinity. Analogues #5333 and #5338 showed direct binding towards human recombinant PA2G4. Importantly, #5333 and #5338 demonstrated a 70-fold lower toxicity for normal human myofibroblasts compared to WS6. Structure-activity relationship analysis showed that a 2,3 dimethylphenol was the most suitable substituent at the R1 position. Replacing the trifluoromethyl group on the phenyl ring at the R2 position, with a bromine or hydrogen atom, increased the difference between efficacy against neuroblastoma cells and normal myofibroblast toxicity. The WS6 analogues inhibited neuroblastoma cell phenotype in vitro, in part through effects on apoptosis, while their anti-cancer effects required both PA2G4 and MYCN expression. Collectively, chemical inhibition of PA2G4-MYCN binding by WS6 analogues represents a first-in-class drug discovery which may have implications for other MYCN-driven cancers.

The Anticancer Agent, Di-2-Pyridylketone 4,4-Dimethyl-3-Thiosemicarbazone (Dp44mT), Up-Regulates the AMPK-Dependent Energy Homeostasis Pathway in Cancer Cells.

Adenosine monophosphate-activated protein kinase (AMPK) is a cellular energy sensor that monitors ATP levels. There is also evidence that AMPK has onco-suppressive properties. Iron plays a crucial role in cellular energy transducing pathways and tumor cell proliferation. Therefore, metals (e.g., iron) could play an important role in the regulation of AMPK-dependent pathways. Hence, this investigation examined the effect of the iron and copper chelator and potent anti-cancer agent, di-2-pyridylketone 4,4-dimethyl-3-thiosemicarbazone (Dp44mT), on the AMPK-mediated pathway. These studies demonstrated that Dp44mT, which forms intracellular redox-active complexes with iron and copper, significantly activated AMPK (i.e., p-AMPK/AMPK ratio) in 5 different tumor cell-types. Furthermore, examination of the Dp44mT-metal complexes demonstrated that the effect of Dp44mT on AMPK was due to a dual mechanism: (1) its ability to chelate metal ions; and (2) the generation of reactive oxygen species (ROS). The activation of the AMPK-pathway by Dp44mT was mediated by the upstream kinase, liver kinase B1 (LKB1) that is a known tumor suppressor. Moreover, using AMPKα1-selective silencing, we demonstrated that Dp44mT activated AMPK, resulting in inhibition of acetyl CoA carboxylase 1 (ACC1) and raptor, and activation of Unc-51 like kinase (ULK1). These effects are vital for inhibition of fatty acid synthesis, suppression of protein synthesis and autophagic activation, respectively. Together, this AMPK-mediated repair response aims to rescue the loss of metal ions via chelation and the induction of cytotoxic damage mediated by redox cycling of the Dp44mT-metal ion complex. In conclusion, this study demonstrates for the first time that chelators target the AMPK-dependent pathway.

IRON METABOLISM AND AUTOPHAGY: A POORLY EXPLORED RELATIONSHIP THAT HAS IMPORTANT CONSEQUENCES FOR HEALTH AND DISEASE.

Autophagy is an important cell survival pathway which is up-regulated under stress conditions.1) It is a well regulated catabolic process and enables the cell to recycle its constituents and organelles for re-use.1) Autophagy has been implicated to play an important role in a variety of disorders such as cancer and protein aggregatory neurodegenerative diseases e.g., Alzheimer's disease, Parkinson's disease and Huntington's disease.2) Iron is a critical metal required for normal cellular functioning.3) A very tightly regulated balance of iron levels is required for the normal physiological functioning of the cell.3) Both an excess and deficiency of iron can lead to cellular stress, and thereby, alters the autophagic status within the cell. Thus, it is important to completely understand how iron can affect the autophagic pathway and its potential implications under physiological as well as pathological conditions.

The use of iron chelators in biocidal compositions: evaluation of patent, WO2014059417A1.

Anti-microbial-potentiating compositions, containing one or more anti-microbial agents and an iron chelator, are claimed in the patent application. Different combinations of anti-microbial agents with various classes of iron chelators are claimed. The use of such formulations enhances the biocidal activity of the anti-microbial agents. The compositions can be used for a number of applications, such as preservatives, personal care formulations, water-based paints, household cleaning products, and so on. These compositions have therapeutic use in the treatment of acne where they have been shown to markedly potentiate the effect of anti-microbial agents. They also have possible use in wound-healing products.

Adenosine monophosphate-activated kinase and its key role in catabolism: structure, regulation, biological activity, and pharmacological activation.

Adenosine monophosphate-activated protein kinase (AMPK) is a cellular energy sensor, which once activated, plays a role in several processes within the cell to restore energy homeostasis. The protein enhances catabolic pathways, such as ß-oxidation and autophagy, to generate ATP, and inhibits anabolic processes that require energy, including fatty acid, cholesterol, and protein synthesis. Due to its key role in the regulation of critical cellular pathways, deregulation of AMPK is associated with the pathology of many diseases, including cancer, Wolff-Parkinson-White syndrome, neurodegenerative disorders, diabetes, and metabolic syndrome. In fact, AMPK is a target of some pharmacological agents implemented in the treatment of diabetes (metformin and thiazolidinediones) as well as other naturally derived products, such as berberine, which is used in traditional medicine. Due to its critical role in the cell and the pathology of several disorders, research into developing AMPK as a therapeutic target is becoming a burgeoning and exciting field of pharmacological research. A profound understanding of the regulation and activity of AMPK would enhance its development as a promising therapeutic target.

Gene of the month. AMP kinase (PRKAA1).

The PRKAA1 gene encodes the catalytic α-subunit of 5' AMP-activated protein kinase (AMPK). AMPK is a cellular energy sensor that maintains energy homeostasis within the cell and is activated when the AMP/ATP ratio increases. When activated, AMPK increases catabolic processes that increase ATP synthesis and inhibit anabolic processes that require ATP. Additionally, AMPK also plays a role in activating autophagy and inhibiting energy consuming processes, such as cellular growth and proliferation. Due to its role in energy metabolism, it could act as a potential target of many therapeutic drugs that could be useful in the treatment of several diseases, for example, diabetes. Moreover, AMPK has been shown to be involved in inhibiting tumour growth and metastasis, and has also been implicated in the pathology of neurodegenerative and cardiac disorders. Hence, a better understanding of AMPK and its role in various pathological conditions could enable the development of strategies to use it as a therapeutic target.

Gene of the month: BECN1.

The BECN1 gene encodes the Beclin-1 protein, which is a well-established regulator of the autophagic pathway. It is a mammalian orthologue of the ATG6 gene in yeast and was one of the first identified mammalian autophagy-associated genes. Beclin-1 interacts with a number of binding partners in the cell which can lead to either activation (eg, via PI3KC3/Vps34, Ambra 1, UV radiation resistance-associated gene) or inhibition (eg, via Bcl-2, Rubicon) of the autophagic pathway. Apart from its role as a regulator of autophagy, it is also shown to effect important biological processes in the cell such as apoptosis and embryogenesis. Beclin-1 has also been implicated to play a critical role in the pathology of a variety of disease states including cancer, neurological disorders (eg, Alzheimer's disease, Parkinson's disease) and viral infections. Thus, understanding the functions of Beclin-1 and its interactions with other cellular components will aid in its development as an important therapeutic target for future drug development.