Does gene therapy become pharmacotherapy?

Defining the role of the JAK-STAT pathway in head and neck and thoracic malignancies: implications for future therapeutic approaches

Although the role of the Janus kinase (JAK)-signal transducer and activator of transcription (STAT) pathway has been most extensively studied in hematopoietic cells and hematologic malignancies, it is also activated in epithelial tumors, including those originating in the lungs and head and neck. The canonical pathway involves the activation of JAK following ligand binding to cytokine receptors. The activated JAKs then phosphorylate STAT proteins, leading to their dimerization and translocation into the nucleus. In the nucleus, STATs act as transcription factors with pleiotropic downstream effects. STATs can be activated independently of JAKs, most notably by c-Src kinases. In cancer cells, STAT3 and STAT5 activation leads to the increased expression of downstream target genes, leading to increased cell proliferation, cell survival, angiogenesis, and immune system evasion. STAT3 and STAT5 are expressed and activated in head and neck squamous cell carcinoma (HNSCC) where they contribute to cell survival and proliferation. In HNSCC, STATs can be activated by a number of signal transduction pathways, including the epidermal growth factor receptor (EGFR), alpha7 nicotinic receptor, interleukin (IL) receptor, and erythropoietin receptor pathways. Activated STATs are also expressed in lung cancer, but the biological effects of JAK/STAT inhibition in this cancer are variable. In lung cancer, STAT3 can be activated by multiple pathways, including EGFR. Several approaches have been used to inhibit STAT3 in the hopes of developing an antitumor agent. Although several STAT3-specific agents are promising, none are in clinical development, mostly because of drug delivery and stability issues. In contrast, several JAK inhibitors are in clinical development. These orally available, ATP-competitive, small-molecule kinase inhibitors are being tested in myeloproliferative disorders. Future studies will determine whether JAK inhibitors are useful in the treatment of HNSCC or lung cancer.

Nucleic acid drugs for prevention of cardiac rejection

Heart transplantation has been broadly performed in humans. However, occurrence of acute and chronic rejection has not yet been resolved. Several inflammatory factors, such as cytokines and adhesion molecules, enhance the rejection. The graft arterial disease (GAD), which is a type of chronic rejection, is characterized by intimal thickening comprised of proliferative smooth muscle cells. Specific treatments that target the attenuation of acute rejection and GAD formation have not been well studied in cardiac transplantation. Recent progress in the nucleic acid drugs, such as antisense oligodeoxynucleotides (ODNs) to regulate the transcription of disease-related genes, has important roles in therapeutic applications. Transfection of cis-element double-stranded DNA, named as “decoy,” has been also reported to be a useful nucleic acid drug. This decoy strategy has been not only a useful method for the experimental studies of gene regulation but also a novel clinical strategy. In this paper, we reviewed the experimental results of NF-κB, E2F, AP-1, and STAT-1 decoy and other ODNs using the experimental heart transplant models.

Targeting STAT3 in cancer: how successful are we?

BACKGROUND

Aberrant activation of the signal transducer and activator of transcription (STAT)3 occurs in many human tumors. Moreover, studies utilizing genetic and pharmacological approaches to modulate constitutive STAT3 activity have provided compelling evidence for the critical role of aberrant STAT3 activity in malignant transformation and tumor progression, and thereby validated STAT3 as a novel cancer drug target.

OBJECTIVE

This review is intended to be a full coverage of the efforts to develop direct STAT3 inhibitors and will provide a discussion on the inhibitory modalities developed to date.

METHODS

Review of the literature focused on the modalities and mechanisms that directly target and inhibit the STAT protein or its functions.

RESULTS/CONCLUSION

While a variety of STAT3 inhibitors have been identified that induce antitumor cell effects in vitro and in vivo, the landscape remains murky. With a few exceptions, most of the STAT3 inhibitors reported to date have not undergone an in vivo efficacy, pharmacology or toxicity testing. Also, there is no evidence, per the published literature of an impending clinical development for the few agents that were reported to exhibit in vivo efficacy. Overall, there is the need for a reassessment of the ongoing strategies to target STAT3 intended not only for refinement, but also for incorporating some new technologies to strengthen our efforts and ensure the success - sooner, rather than later - of identifying suitable anti-STAT3 agents for development into clinically useful anticancer therapeutics.

Therapeutic regulation of gene expression in the inner ear using RNA interference

Targeting and downregulating specific genes with antisense and decoy oligonucleotides, ribozymes or RNA interference (RNAi) offer the theoretical potential of altering a disease phenotype. Here we review the molecular mechanism behind the in vivo application of RNAi-mediated gene silencing, focusing on its application to the inner ear. RNAi is a physiological phenomenon in which small, double-stranded RNA molecules (small interfering RNA, siRNA) reduce expression of homologous genes. Notable for its exquisite sequence specificity, it is ideally applied to diseases caused by a gain-of-function mechanism of action. Types of deafness in which gain-of-function mutations are observed include DFNA2 (KCNQ4), DFNA3 (GJB2) and DFNA5 (DFNA5). Several strategies can be used to deliver siRNA into the inner ear, including cationic liposomes, adeno-associated and lentiviral vectors, and adenoviral vectors. Transduction efficiency with cationic liposomes is low and the effect is transient; with adeno-associated and lentiviral vectors, long-term transfection is possible using a small hairpin RNA expression cassette.

Semi-synthetic ecdysteroids as gene-switch actuators: synthesis, structure-activity relationships, and prospective ADME properties

The ligand-inducible, ecdysteroid receptor (EcR) gene-expression system can add critical control features to protein expression in cell and gene therapy. However, potent natural ecdysteroids possess absorption, distribution, metabolism and excretion (ADME) properties that have not been optimised for use as gene-switch actuators in vivo. Herein we report the first systematic synthetic exploration of ecdysteroids toward modulation of gene-switch potency. Twenty-three semi-synthetic O-alkyl ecdysteroids were assayed in both a natural insect system (Drosophila B(II) cells) and engineered gene-switch systems in mammalian cells using Drosophila melanogaster, Choristoneura fumiferana, and Aedes aegypti EcRs. Gene-switch potency is maintained, or even enhanced, for ecdysteroids methylated at the 22-position in favourable cases. Furthermore, trends toward lower solubility, higher permeability, and higher blood-brain barrier penetration are supported by predicted ADME properties, calculated using the membrane-interaction (MI)-QSAR methodology. The structure-activity relationship (SAR) of alkylated ecdysteroids indicates that 22-OH is an H-bond acceptor, 25-OH is most likely an H-bond donor, and 2-OH and 3-OH are donors and/or acceptors in network with each other, and with the EcR. The strategy of alkylation points the way to improved ecdysteroidal actuators for switch-activated gene therapy.

Molecular targets in cerebral ischemia for developing novel therapeutics

Cerebral ischemia (stroke) triggers a complex series of biochemical and molecular mechanisms that impairs the neurologic functions through breakdown of cellular integrity mediated by excitotoxic glutamatergic signalling, ionic imbalance, free-radical reactions, etc. These intricate processes lead to activation of signalling mechanisms involving calcium/calmodulin-dependent kinases (CaMKs) and mitogen-activated protein kinases (MAPKs) such as extracellular signal-regulated kinase (ERK), p38, and c-Jun N-terminal kinase (JNK). The distribution of these transducers bring them in contact with appropriate molecular targets leading to altered gene expression, e.g. ERK and JNK mediated early gene induction, responsible for activation of cell survival/damaging mechanisms. Moreover, inflammatory reactions initiated at the neurovascular interface and alterations in the dynamic communication between the endothelial cells, astrocytes and neurons are thought to substantially contribute to the pathogenesis of the disease. The damaging mechanisms may proceed through rapid nonspecific cell lysis (necrosis) or by active form of cell demise (apoptosis or necroptosis), depending upon the severity and duration of the ischemic insult. A systematic understanding of these molecular mechanisms with prospect of modulating the chain of events leading to cellular survival/damage may help to generate the potential strategies for neuroprotection. This review briefly covers the current status on the molecular mechanisms of stroke pathophysiology with an endeavour to identify potential molecular targets such as targeting postsynaptic density-95 (PSD-95)/N-methyl-d-aspartate (NMDA) receptor interaction, certain key proteins involved in oxidative stress, CaMKs and MAPKs (ERK, p38 and JNK) signalling, inflammation (cytokines, adhesion molecules, etc.) and cell death pathways (caspases, Bcl-2 family proteins, poly (ADP-ribose) polymerase-1 (PARP-1), apoptosis-inducing factor (AIF), inhibitors of apoptosis proteins (IAPs), heat shock protein 70 (HSP70), receptor interacting protein (RIP), etc., besides targeting directly the genes itself. However, selecting promising targets from various signalling cascades, for drug discovery and development is very challenging, nevertheless such novel approaches may lead to the emergence of new avenues for therapeutic intervention in cerebral ischemia.