Targeting the leukemic stem cell: the Holy Grail of leukemia therapy

Since the discovery of leukemic stem cells (LSCs) over a decade ago, many of their critical biological properties have been elucidated, including their distinct replicative properties, cell surface phenotypes, their increased resistance to chemo-therapeutic drugs and the involvement of growthpromoting chromosomal translocations. Of particular importance is their ability to transfer malignancy to non-obese diabetic-severe combined immunodeficient (NOD-SCID) mice. Furthermore, numerous studies demonstrate that acute myeloid leukemia arises from mutations at the level of stem cell, and chronic myeloid leukemia is also a stem cell disease. In this review, we will evaluate the main characteristics of LSCs elucidated in several well-documented leukemias. In addition, we will discuss points of therapeutic intervention. Promising therapeutic approaches include the targeting of key signal transduction pathways (for example, PI3K, Rac and Wnt) with smallmolecule inhibitors and specific cell surface molecules (for example, CD33, CD44 and CD123), with effective cytotoxic antibodies. Also, statins, which are already widely therapeutically used for a variety of diseases, show potential in targeting LSCs. In addition, drugs that inhibit ATP-binding cassette transporter proteins are being extensively studied, as they are important in drug resistance â a frequent characteristic of LSCs. Although the specific targeting of LSCs is a relatively new field, it is a highly promising battleground that may reveal the Holy Grail of cancer therapy. Originally published Leukemia, Vol. 23, No. 1, Jan 200

Computational Modeling of PI3K/AKT and MAPK Signaling Pathways in Melanoma Cancer

Background Malignant melanoma is an aggressive tumor of the skin and seems to be resistant to current therapeutic approaches. Melanocytic transformation is thought to occur by sequential accumulation of genetic and molecular alterations able to activate the Ras/Raf/MEK/ERK (MAPK) and/or the PI3K/AKT (AKT) signalling pathways. Specifically, mutations of B-RAF activate MAPK pathway resulting in cell cycle progression and apoptosis prevention. According to these findings, MAPK and AKT pathways may represent promising therapeutic targets for an otherwise devastating disease. Result Here we show a computational model able to simulate the main biochemical and metabolic interactions in the PI3K/AKT and MAPK pathways potentially involved in melanoma development. Overall, this computational approach may accelerate the drug discovery process and encourages the identification of novel pathway activators with consequent development of novel antioncogenic compounds to overcome tumor cell resistance to conventional therapeutic agents. The source code of the various versions of the model are available as S1 Archive

Activation of mGlu3 Receptors Stimulates the Production of GDNF in Striatal Neurons

Metabotropic glutamate (mGlu) receptors have been considered potential targets for the therapy of experimental parkinsonism. One hypothetical advantage associated with the use of mGlu receptor ligands is the lack of the adverse effects typically induced by ionotropic glutamate receptor antagonists, such as sedation, ataxia, and severe learning impairment. Low doses of the mGlu2/3 metabotropic glutamate receptor agonist, LY379268 (0.25–3 mg/kg, i.p.) increased glial cell line-derived neurotrophic factor (GDNF) mRNA and protein levels in the mouse brain, as assessed by in situ hybridization, real-time PCR, immunoblotting, and immunohistochemistry. This increase was prominent in the striatum, but was also observed in the cerebral cortex. GDNF mRNA levels peaked at 3 h and declined afterwards, whereas GDNF protein levels progressively increased from 24 to 72 h following LY379268 injection. The action of LY379268 was abrogated by the mGlu2/3 receptor antagonist, LY341495 (1 mg/kg, i.p.), and was lost in mGlu3 receptor knockout mice, but not in mGlu2 receptor knockout mice. In pure cultures of striatal neurons, the increase in GDNF induced by LY379268 required the activation of the mitogen-activated protein kinase and phosphatidylinositol-3-kinase pathways, as shown by the use of specific inhibitors of the two pathways. Both in vivo and in vitro studies led to the conclusion that neurons were the only source of GDNF in response to mGlu3 receptor activation. Remarkably, acute or repeated injections of LY379268 at doses that enhanced striatal GDNF levels (0.25 or 3 mg/kg, i.p.) were highly protective against nigro-striatal damage induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine in mice, as assessed by stereological counting of tyrosine hydroxylase-positive neurons in the pars compacta of the substantia nigra. We speculate that selective mGlu3 receptor agonists or enhancers are potential candidates as neuroprotective agents in Parkinson's disease, and their use might circumvent the limitations associated with the administration of exogenous GDNF

Current Neuropharmacology Volume 9, Supplement 1, September 2011

International audienc

Generalized and focal dystonic syndromes: possible therapy with salmon calcitonin.

We report that repeated administration of salmon calcitonin (20-40 micrograms daily for 30 days) improves dystonic symptoms in patients affected by idiopathic torsion dystonia, blepharospasm-oromandibular dystonia syndrome or writer's cramp syndrome. These results support the suggestion that calcitonin may act at central level influencing the extrapyramidal motor system

Metabotropic Glutamate 1 Receptor: Current Concepts and Perspectives

Almost 25 years after the first report that glutamate can activate receptors coupled to heterotrimeric G-proteins, tremendous progress has been made in the field of metabotropic glutamate receptors. Now, eight members of this family of glutamate receptors, encoded by eight different genes that share distinctive structural features have been identified. The first cloned receptor, the metabotropic glutamate ( mGlu) receptor mGlu1 has probably been the most extensively studied mGlu receptor, and in many respects it represents a prototypical subtype for this family of receptors. Its biochemical, anatomical, physiological, and pharmacological characteristics have been intensely investigated. Together with subtype 5, mGlu1 receptors constitute a subgroup of receptors that couple to phospholipase C and mobilize Ca(2+) from intracellular stores. Several alternatively spliced variants of mGlu1 receptors, which differ primarily in the length of their C-terminal domain and anatomical localization, have been reported. Use of a number of genetic approaches and the recent development of selective antagonists have provided a means for clarifying the role played by this receptor in a number of neuronal systems. In this article we discuss recent advancements in the pharmacology and concepts about the intracellular transduction and pathophysiological role of mGlu1 receptors and review earlier data in view of these novel findings. The impact that this new and better understanding of the specific role of these receptors may have on novel treatment strategies for a variety of neurological and psychiatric disorders is considered

PHARMACOLOGICAL CHARACTERIZATION OF METABOTROPIC GLUTAMATE RECEPTORS IN CULTURED CEREBELLAR GRANULE CELLS

A detailed pharmacological characterization of metabotropic glutamate receptors (mGluR) was performed in primary cultures of cerebellar granule cells at 6 days in vitro (DIV). The rank order of agonists induced polyphosphoinositide (PPI) hydrolysis (after correcting for the ionotropic component in the response) was as follows : in terms of efficiency, Glu > quisqualate (quis) = ibotenate (ibo) > (1S,3R)-1-amino-cyclopentane-1,3-dicarboxylic acid (ACPD) > beta-methyl-amino-L-alanine (BMAA) and in terms of potency, quis > ACPD > Glu > ibo = BMAA. Ionotropic excitatory amino acid (EAA) receptor agonists, such as alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) and N-methyl-D-aspartate (NMDA) were relatively inactive (in the presence of Mg2+). Quis and ACPD-induced PPI hydrolysis was unaffected by ionotropic Glu receptor antagonists, but was inhibited, in part by L-2-amino-3-phosphonopropionate (AP3). In contrast, Glu-or ibo- induced PPI hydrolysis was reduced, in part, by both AP3 and NMDA receptor antagonists. Characteristic interactions involving different transmitter receptors were noted. PPI hydrolysis evoked by quis and 1S,3R-ACPD was not additive. In contrast, PPI hydrolysis stimulated by quis/ACPD and carbamylcholine was additive (indicating different receptors/transduction pathways). In the presence of Mg2+, the metabotropic response to quis/AMPA and NMDA was synergistic (this being consistent with AMPA receptor-induced depolarization activating NMDA receptor). On the other hand, in Mg2+-free buffer the effects of quis and NMDA, at concentrations causing maximal PPI hydrolysis, were additive (indicating that PPI hydrolysis was effected by two different mechanisms). Thus, in cerebellar granule cells EAAs elicit PPI hydrolysis by acting at two distinct receptor types: (i) metabotropic Glu receptors (mGluR), with pharmacological characteristics suggesting the expression of a unique mGluR receptor that shows certain similarities to those observed for the mGluR1 subtype (Aramori and Nakanishi, 1992) and (ii) NMDA receptors. The physiological agonist, Glu, is able to stimulate both receptor classes

Shedding of microvesicles from microglia contributes to the effects induced by metabotropic glutamate receptor 5 activation on neuronal death

Metabotropic glutamate (mGlu) receptor 5 is involved in neuroinflammation and has been shown to mediate reduced inflammation and neurotoxicity and to modify microglia polarization. On the other hand, blockade of mGlu5 receptor results in inhibition of microglia activation. To dissect this controversy, we investigated whether microvesicles (MVs) released from microglia BV2 cells could contribute to the communication between microglia and neurons and whether this interaction was modulated by mGlu5 receptor. Activation of purinergic ionotropic P2X7 receptor with the stable ATP analog benzoyl-ATP (100 μM) caused rapid MVs shedding from BV2 cells. Ionic currents through P2X7 receptor increased in BV2 cells pretreated for 24 h with the mGlu5 receptor agonist CHPG (200 μM) as by patch-clamp recording. This increase was blunted when microglia cells were activated by exposure to lipopolysaccharide (LPS; 0.1 μg/ml for 6 h). Accordingly, a greater amount of MVs formed after CHPG treatment, an effect prevented by the mGlu5 receptor antagonist MTEP (100 μM), as measured by expression of flotillin, a membrane protein enriched in MVs. Transferred MVs were internalized by SH-SY5Y neurons where they did not modify neuronal death induced by a low concentration of rotenone (0.1 μM for 24 h), but significantly increased rotenone neurotoxicity when shed from CHPG-treated BV2 cells. miR146a was increased in CHPG-treated MVs, an effect concealed in MVs from LPS-activated BV2 cells that showed per se an increase in miRNA146a levels. The present data support a role for microglia-shed MVs in mGlu5-mediated modulation of neuronal death and identify miRNAs as potential critical mediators of this interaction