Pre-clinical analysis of changes in intra-cellular biochemistry of glioblastoma multiforme (GBM) cells due to c-Myc silencing

C-Myc Signaling Pathway in Treatment and Prevention of Brain Tumors

Brain tumors are responsible for high morbidity and mortality worldwide. Several factors such as the presence of blood-brain barrier (BBB), sensitive location in the brain, and unique biological features challenge the treatment of brain tumors. The conventional drugs are no longer effective in the treatment of brain tumors, and scientists are trying to find novel therapeutics for brain tumors. In this way, identification of molecular pathways can facilitate finding an effective treatment. c-Myc is an oncogene signaling pathway capable of regulation of biological processes such as apoptotic cell death, proliferation, survival, differentiation, and so on. These pleiotropic effects of c-Myc have resulted in much fascination with its role in different cancers, particularly brain tumors. In the present review, we aim to demonstrate the upstream and down-stream mediators of c-Myc in brain tumors such as glioma, glioblastoma, astrocytoma, and medulloblastoma. The capacity of c-Myc as a prognostic factor in brain tumors will be investigated. Our goal is to define an axis in which the c-Myc signaling pathway plays a crucial role and to provide direction for therapeutic targeting in these signaling networks in brain tumors.

Under explored epigenetic modulators: role in glioma chemotherapy

Patients with somatic mutations of epigenetic regulators are characterized by aberrant chromatin modification patterns. Recent mechanistic studies pairing chemical tool compounds and deep-sequencing technology have greatly broadened our understanding of epigenetic regulation in glioma progression and underpinned alternative treatment of epigenetic inhibitors. However, the effect of most inhibitors is condition-dependent, and the overall results of clinical trials still have not been applied to patients. There is an intense need to develop more potent and specific compounds as well as identify the population who may achieve clinical benefits. Besides, combination therapy with conventional therapeutics is another alternative strategy. In this review, we summarize well-characterized chemical probes in glioma research and clinical translation. We also discuss the target population and combination of therapy regimens of various agents. In a holistic sense, we try to provide guidance for selecting targeted chemical probes and pave the way for personalized rational therapy.

Ubenimex enhances Brd4 inhibition by suppressing HEXIM1 autophagic degradation and suppressing the Akt pathway in glioma cells

Inhibition of Brd4 by JQ1 treatment showed potential in the treatment of glioma, however, some cases showed low sensitivity of JQ1. In addition, the pre-clinical analysis showed its limitation by demonstrating that transient treatment with JQ1 leads to aggressive tumor development. Thus, an improved understanding of the mechanisms underlying JQ1 is urgently required to design strategies to improve its efficiency, as well as overcome its limitation. HEXIM1 has been confirmed to have an important role in regulating JQ1 sensitivity. In our study, ubenimex, a classical anti-cancer drug showed potential in regulating the JQ1 sensitivity of glioma cells using the WST-1 proliferation assay. Further studies demonstrated that ubenimex inhibited autophagy and downregulated the autophagic degradation of HEXIM1. The role of HEXIM1 in regulating JQ1 sensitivity was verified by the HEXIM1 knockdown. Since ubenimex was verified as an Akt inhibitor, we further studied the role of Akt inhibition in regulating JQ1 sensitivity and migration of glioma cells. Data showed that ubenimex improved the efficiency of JQ1 treatment and suppressed migration both in the in vitro and in vivo xenografts models. The Akt agonist attenuated these effects, pointing to the role of Akt inhibition in JQ1 sensitivity and suppressed migration. Our findings suggest the potential of ubenimex adjuvant treatment to enhance JQ1 efficiency and attenuate parts of its side effect (enhancing tumor aggressive) by regulating the autophagic degradation of HEXIM1 and Akt inhibition.

Targeting the cancer epigenome: synergistic therapy with bromodomain inhibitors

Epigenetic and genomic alterations regulate the transcriptional landscape of cells during cancer onset and progression. Recent clinical studies targeting the epigenetic 'readers' (bromodomains) for cancer therapy have established the effectiveness of bromodomain (BRD) and extraterminal (BET) inhibitors in treating several types of cancer. In this review, we discuss key mechanisms of BET inhibition and synergistic combinations of BET inhibitors with histone deacetylase inhibitors (HDACi), histone methyltransferase inhibitors (HMTi), DNA methyltransferase inhibitors (DNMTi), kinase, B-cell lymphoma 2 (Bcl-2) and proteosome inhibitors, and immunomodulatory drugs for cancer therapy. We also highlight the potential of such combinations to overcome drug resistance, and the evolving approaches to developing novel BET inhibitors.

Bisphosphonate-Functionalized Hydroxyapatite Nanoparticles for the Delivery of the Bromodomain Inhibitor JQ1 in the Treatment of Osteosarcoma

Osteosarcoma (OS) is one of the most common neoplasia among children, and its survival statistics have been stagnating since the combinatorial anticancer therapy triad was first introduced. Here, we report on the assessment of the effect of hydroxyapatite (HAp) nanoparticles loaded with medronate, the simplest bisphosphonate, as a bone-targeting agent and JQ1, a small-molecule bromodomain inhibitor, as a chemotherapeutic in different 2D and 3D K7M2 OS in vitro models. Both additives decreased the crystallinity of HAp, but the effect was more intense for medronate because of its higher affinity for HAp. As the result of PO₄^3--NH⁺ binding, JQ1 shielded the surface phosphates of HAp and pushed its surface charge to more positive values, exhibiting the opposite effect from calcium-blocking medronate. In contrast to the faster and more exponential release of JQ1 from monetite, its release from HAp nanoparticles followed a zero-order kinetics, but 98% of the payload was released after 48 h. The apoptotic effect of HAp nanoparticles loaded with JQ1, with medronate and with both JQ1 and medronate, was selective in 2D culture: pronounced against the OS cells and nonexistent against the healthy fibroblasts. While OS cell invasion was significantly inhibited by all of the JQ1-containing HAp formulations, that is, with and without medronate, all of the combinations of the targeting compound, medronate, and the chemotherapeutic, JQ1, delivered using HAp, but not HAp alone, inhibited OS cell migration from the tumor spheroids. JQ1 delivered using HAp had an effect on tumor migration, invasion, and apoptosis even at extremely low, subnanomolar concentrations, at which no effect of JQ1 per se was observed, meaning that this form of delivery could help achieve a multifold increase of this drug's efficacy. More than 80% of OS cells internalized JQ1-loaded HAp nanoparticles after 24 h of coincubation, suggesting that this augmentation of the activity of JQ1 may be due to the intracellular delivery and sustained release of the drug enabled by HAp. In addition to the reduction of the OS cell viability, the reduction of the migration and invasion radii was observed in OS tumor spheroids challenged with even JQ1-free medronate-functionalized HAp nanoparticles, demonstrating a definite anticancer activity of medronate alone when combined with HAp. The effect of medronate-functionalized JQ1-loaded HAp nanoparticles was most noticeable against OS cells differentiated into an osteoblastic lineage, in which case they surpassed in effect pure JQ1 and medronate-free compositions. The activity of JQ1 was mediated through increased Ezrin expression and decreased RUNX2 expression and was MYC and FOSL1 independent, but these patterns of gene expression changed in cells challenged with the nanoparticulate form of delivery, having been accompanied by the upregulation of RUNX2 and downregulation of Ezrin in OS cells treated with medronate-functionalized JQ1-loaded HAp nanoparticles.

Nardostachys jatamansi Targets BDNF-TrkB to Alleviate Ketamine-Induced Schizophrenia-Like Symptoms in Rats

OBJECTIVE

Schizophrenia, a common neurological disorder appearing in the late teens or early adulthood, is characterized by disorganized thinking, behaviour, and perception of emotions. Aberrant N-methyl-D-aspartate (NMDA) receptor-mediated synaptic plasticity is a major pathological event here due to dysfunction of dopamine and glutamate transmission at NMDA receptors. De-regulated brain-derived neurotrophic factor (BDNF), i.e., its signalling through the tropomyosin receptor kinase B (TrkB) receptor, is a major feature of schizophrenia. With recent global awareness of traditional plant medicines in reducing side effects, the aim of our study was to evaluate the efficacy of the ethanolic root extract of a herb belonging to the Valerianacea family, Nardostachys jatamansi, against ketamine-induced schizophrenia-like model in rats.

METHODS

The effect of the N. jatamansi drug (oral dosage of 500 mg/kg body weight for 14 days) in ketamine-administered male Wistar albino rats (30 mg/kg body weight for 5 days) on modulating behaviour and the level of neurotransmitters like dopamine and glutamate was studied in whole-brain homogenates, and its influence on BDNF and TrkB levels in 2 relevant brain regions, the hippocampus and prefrontal cortex, was assessed.

RESULTS

We observed that N. jatamansi treatment exhibited encouraging results in the modulation of ketamine-induced schizophrenia-like behaviours, principally the positive symptoms. Our drug both significantly upregulated the glutamate level and downregulated the dopamine level in whole-brain homogenates and retained the normal levels of BDNF (in the hippocampus but not in the prefrontal cortex) and TrkB (in both hippocampus and prefrontal cortex) induced by ketamine in rats.

CONCLUSION

These findings suggest a neuroprotective effect of the ethanolic root extract of N. jatamansi against ketamine-induced schizophrenia-like symptoms in rats; possibly, regarding its effect on TrkB signalling. Further research is warranted in the treatment of schizophrenic symptoms.

Epigenetics in cancer stem cells

Compelling evidence have demonstrated that bulk tumors can arise from a unique subset of cells commonly termed "cancer stem cells" that has been proposed to be a strong driving force of tumorigenesis and a key mechanism of therapeutic resistance. Recent advances in epigenomics have illuminated key mechanisms by which epigenetic regulation contribute to cancer progression. In this review, we present a discussion of how deregulation of various epigenetic pathways can contribute to cancer initiation and tumorigenesis, particularly with respect to maintenance and survival of cancer stem cells. This information, together with several promising clinical and preclinical trials of epigenetic modulating drugs, offer new possibilities for targeting cancer stem cells as well as improving cancer therapy overall.

The BET inhibitor JQ1 selectively impairs tumour response to hypoxia and downregulates CA9 and angiogenesis in triple negative breast cancer

The availability of bromodomain and extra-terminal inhibitors (BETi) has enabled translational epigenetic studies in cancer. BET proteins regulate transcription by selectively recognizing acetylated lysine residues on chromatin. BETi compete with this process leading to both downregulation and upregulation of gene expression. Hypoxia enables progression of triple negative breast cancer (TNBC), the most aggressive form of breast cancer, partly by driving metabolic adaptation, angiogenesis and metastasis through upregulation of hypoxia-regulated genes (for example, carbonic anhydrase 9 (CA9) and vascular endothelial growth factor A (VEGF-A). Responses to hypoxia can be mediated epigenetically, thus we investigated whether BETi JQ1 could impair the TNBC response induced by hypoxia and exert anti-tumour effects. JQ1 significantly modulated 44% of hypoxia-induced genes, of which two-thirds were downregulated including CA9 and VEGF-A. JQ1 prevented HIF binding to the hypoxia response element in CA9 promoter, but did not alter HIF expression or activity, suggesting some HIF targets are BET-dependent. JQ1 reduced TNBC growth in vitro and in vivo and inhibited xenograft vascularization. These findings identify that BETi dually targets angiogenesis and the hypoxic response, an effective combination at reducing tumour growth in preclinical studies.

Inhibition of c-MYC with involvement of ERK/JNK/MAPK and AKT pathways as a novel mechanism for shikonin and its derivatives in killing leukemia cells

Leukemia remains life-threatening despite remarkable advances in chemotherapy. The poor prognosis and drug resistance are challenging treatment. Novel drugs are urgently needed. Shikonin, a natural naphthoquinone, has been previously shown by us to be particularly effective towards various leukemia cell lines compared to solid tumors. However, the underlying mechanisms are still poorly understood. Here, we investigated shikonin and 14 derivatives on U937 leukemia cells. Four derivatives (isobutyrylshikonin, 2-methylbutyrylshikonin, isovalerylshikonin and β,β-dimethylacrylshikonin) were more active than shikonin. AnnexinV-PI analysis revealed that shikonins induced apoptosis. Cell cycle G1/S check point regulation and the transcription factor c-MYC, which plays a vital role in cell cycle regulation and proliferation, were identified as the most commonly down-regulated mechanisms upon treatment with shikonins in mRNA microarray hybridizations. Western blotting and DNA-binding assays confirmed the inhibition of c-MYC expression and transcriptional activity by shikonins. Reduction of c-MYC expression was closely associated with deregulated ERK, JNK MAPK and AKT activity, indicating their involvement in shikonin-triggered c-MYC inactivation. Molecular docking studies revealed that shikonin and its derivatives bind to the same DNA-binding domain of c-MYC as the known c-MYC inhibitors 10058-F4 and 10074-G5. This finding indicates that shikonins bind to c-MYC. The effect of shikonin on U937 cells was confirmed in other leukemia cell lines (Jurkat, Molt4, CCRF-CEM, and multidrug-resistant CEM/ADR5000), where shikonin also inhibited c-MYC expression and influenced phosphorylation of AKT, ERK1/2, and SAPK/JNK. In summary, inhibition of c-MYC and related pathways represents a novel mechanism of shikonin and its derivatives to explain their anti-leukemic activity.

Beating the odds: BETs in disease

Bromodomains (BRDs) are evolutionarily conserved protein interaction modules that specifically recognise acetyl-lysine on histones and other proteins, facilitating roles in regulating gene transcription. BRD-containing proteins bound to chromatin loci such as enhancers are often deregulated in disease leading to aberrant expression of proinflammatory cytokines and growth-promoting genes. Recent developments targeting the bromo and extraterminal (BET) subset of BRD proteins demonstrated remarkable efficacy in murine models providing a compelling rationale for drug development and translation to the clinic. Here we summarise recent advances in our understanding of the roles of BETs in regulating gene transcription in normal and diseased tissue as well as the current status of their clinical translation.

Small molecule inhibitors of bromodomain-acetyl-lysine interactions

Bromodomains are protein modules that bind to acetylated lysine residues. Their interaction with histone proteins suggests that they function as "readers" of histone lysine acetylation, a component of the proposed "histone code". Bromodomain-containing proteins are often found as components of larger protein complexes with roles in fundamental cellular process including transcription. The publication of two potent ligands for the BET bromodomains in 2010 demonstrated that small molecules can inhibit the bromodomain-acetyl-lysine protein-protein interaction. These molecules display strong phenotypic effects in a number of cell lines and affect a range of cancers in vivo. This work stimulated intense interest in developing further ligands for the BET bromodomains and the design of ligands for non-BET bromodomains. Here we review the recent progress in the field with particular attention paid to ligand design, the assays employed in early ligand discovery, and the use of computational approaches to inform ligand design.