[Show abstract][Hide abstract] ABSTRACT: Anti-apoptotic Bcl2 family proteins such as Bcl-x(L) protect cells from death by sequestering apoptotic molecules, but also contribute to normal neuronal function. We find in hippocampal neurons that Bcl-x(L) enhances the efficiency of energy metabolism. Our evidence indicates that Bcl-x(L)interacts directly with the β-subunit of the F(1)F(O) ATP synthase, decreasing an ion leak within the F(1)F(O) ATPase complex and thereby increasing net transport of H(+) by F(1)F(O) during F(1)F(O) ATPase activity. By patch clamping submitochondrial vesicles enriched in F(1)F(O) ATP synthase complexes, we find that, in the presence of ATP, pharmacological or genetic inhibition of Bcl-x(L) activity increases the membrane leak conductance. In addition, recombinant Bcl-x(L) protein directly increases the level of ATPase activity of purified synthase complexes, and inhibition of endogenous Bcl-x(L) decreases the level of F(1)F(O) enzymatic activity. Our findings indicate that increased mitochondrial efficiency contributes to the enhanced synaptic efficacy found in Bcl-x(L)-expressing neurons.
[Show abstract][Hide abstract] ABSTRACT: The ability to isolate and accurately position single cells in three dimensions is becoming increasingly important in many areas of biological research. The authors describe the design, theoretical modelling and testing of a novel dielectrophoretic (DEP) tweezer for picking out and relocating single target cells. The device is constructed using facilities available in most electrophysiology laboratories, without the requirement of sophisticated and expensive microfabrication technology, and offers improved practical features over previously reported DEP tweezer designs. The DEP tweezer has been tested using transfected HEI-193 human schwannoma cells, with visual identification of the target cells being aided by labelling the incorporated gene product with a green fluorescent protein.
IET Nanobiotechnology 04/2011; · 1.72 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Ivermectin is an old anti-parasitic antibiotic which selectively kills nematodes at a very low dose (0.2 mg/kg) by inhibiting their GABA (gamma-aminobutyric acid) receptor, but not mammalian counterpart. Interestingly, several years ago it was reported by a Russian group that Ivermectin can suppress almost completely the growth of human melanoma and a few other cancer xenografts in mice at the much higher doses (3-5 mg/kg) without any adverse effect on mice. However, its anti-cancer mechanism still remained to be clarified at the molecular levels, that would determine the specific type of cancers susceptible to this drug. The first hint towards its anti-PAK1 potential was a recent finding that Ivermectin at its sublethal doses dramatically reduces the litter size (number of eggs laid) of the tiny nematode C. elegans. Interestingly, either a PAK1-deficiency (gene knock-out) or treatment with natural anti-PAK1 products such as CAPE (caffeic acid phenethyl ester) and ARC (artepillin C), the major anti-cancer ingredients in propolis, also causes the exactly same effect on this nematode, suggesting the possibility that the kinase PAK1 might be a new target of Ivermectin. This kinase is required for the growth of more than 70% of human cancers such as pancreatic, colon, breast and prostate cancers and NF (neurofibromatosis) tumors. Here we demonstrate for the first time that Ivermectin blocks the oncogenic kinase PAK1 in human ovarian cancer and NF2-deficient Schwannoma cell lines to suppress their PAK1-dependent growth in cell culture, with the IC50 between 5-20 μM depending on cell lines.
Drug discoveries & therapeutics. 12/2009; 3(6):243-6.
[Show abstract][Hide abstract] ABSTRACT: P-glycoprotein (Pgp) is an ATP-dependent efflux pump involved in transport of xenobiotics from cells that, when overexpressed, can mediate multidrug resistance in mammalian cells. Pgp may be a candidate target for new anthelmintics, as it plays critical roles in normal cell physiology, in removal of drugs from cells, and potentially in the development of drug resistance. Schistosomes are parasitic flatworms that cause schistosomiasis, which affects hundreds of millions of people worldwide. Here, we express SMDR2, a Pgp homologue from Schistosoma mansoni (Platyhelminthes), in Chinese hamster ovary (CHO) cells and use fluorescence-based assays to examine the functional and pharmacological properties of this transporter. Membrane vesicles from stably transfected CHO cells expressing recombinant SMDR2 show significant increases in rhodamine transport and ATP hydrolysis compared with those from control cells or cells transfected with empty vector. SMDR2-mediated transport is inhibited by the Pgp modulators verapamil (IC(50)=12.1 muM) and nifedipine, and also by praziquantel, the current drug of choice against schisotosomiasis (IC(50)=17.4 muM). Efflux measurements of a fluorescent analog of praziquantel indicate that it is also a substrate for SMDR2. The interaction of praziquantel with SMDR2 may offer new strategies for potentiating the action of praziquantel and possibly overcoming drug resistance.
The FASEB Journal 10/2009; 24(1):128-35. · 5.48 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Schwannomas are benign tumors forming along peripheral nerves that can cause deafness, pain and paralysis. Current treatment involves surgical resection, which can damage associated nerves. To achieve tumor regression without damage to nerve fibers, we generated an HSV amplicon vector in which the apoptosis-inducing enzyme, caspase-1 (ICE), was placed under the Schwann cell-specific P0 promoter. Infection of schwannoma, neuroblastoma and fibroblastic cells in culture with ICE under the P0 promoter showed selective toxicity to schwannoma cells, while ICE under a constitutive promoter was toxic to all cell types. After direct intratumoral injection of the P0-ICE amplicon vector, we achieved marked regression of schwannoma tumors in an experimental xenograft mouse model. Injection of this amplicon vector into the sciatic nerve produced no apparent injury to the associated dorsal root ganglia neurons or myelinated nerve fibers. The P0-ICE amplicon vector provides a potential means of 'knifeless resection' of schwannoma tumors by injection of the vector into the tumor with low risk of damage to associated nerve fibers.
Cancer gene therapy 10/2009; 17(4):266-74. · 3.13 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: One potential physiological target for new antischistosomals is the parasite's system for excretion of wastes and xenobiotics. P-glycoprotein (Pgp), a member of the ATP-binding-cassette superfamily of proteins, is an ATP-dependent efflux pump involved in transport of toxins and xenobiotics from cells. In vertebrates, increased expression of Pgp is associated with multidrug resistance in tumor cells. Pgp may also play a role in drug resistance in helminths. In this report, we examine the relationship between praziquantel (PZQ), the current drug of choice against schistosomiasis, and Pgp expression in Schistosoma mansoni. We show that levels of RNA for SMDR2, a Pgp homolog from S. mansoni, increase transiently in adult male worms following exposure to sub-lethal concentrations (100-500 nM) of PZQ. A corresponding, though delayed, increase in anti-Pgp immunoreactive protein expression occurs in adult males following exposure to PZQ. The level of anti-Pgp immunoreactivity in particular regions of adult worms also increases in response to PZQ. Adult worms from an Egyptian S. mansoni isolate with reduced sensitivity to PZQ express increased levels of SMDR2 RNA and anti-Pgp-immunoreactive protein, perhaps indicating a role for multidrug resistance proteins in development or maintenance of PZQ resistance.
Molecular and Biochemical Parasitology 06/2009; 167(1):54-9. · 2.24 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: There are mainly three types of propolis whose major anticancer ingredients are entirely different: (1) CAPE (caffeic acid phenethyl ester)-based propolis in Europe, Far East and New Zealand, (2) artepillin C (ARC)-based Brazilian green propolis and (3) Brazilian red propolis. It was shown previously that NF (neurofibromatosis)-associated tumors require the kinase PAK1 for their growth, and CAPE-based propolis extracts such as Bio 30 suppress completely the growth of NF tumors in vivo by blocking PAK1 signaling. Also it was demonstrated that ARC suppresses angiogenesis, suggesting the possibility that ARC also blocks oncogenic PAK1 signaling. Here it is shown for the first time that both ARC and green propolis extract (GPE) indeed block the PAK1 signaling selectively, without affecting another kinase known as AKT. Furthermore, it was confirmed that ARC as well as GPE suppress almost completely the growth of human NF tumor xenografts in mice, as does Bio 30. These results suggest that both CAPE-based and ARC-based propolis extracts are natural anti-PAK1 remedies and could be among the first effective NF therapeutics available on the market. Since more than 70% of human cancers such as breast and prostate cancers require the kinase PAK1 for their growth, it is quite possible that GPE could be potentially useful for the treatment of these cancers, as is Bio 30.
Phytotherapy Research 11/2008; 23(3):423-7. · 2.40 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Dysfunction of the NF1 gene coding a RAS GAP is the major cause of neurofibromatosis type 1 (NF1), whereas neurofibromatosis type 2 (NF2) is caused primarily by dysfunction of the NF2 gene product called merlin that inhibits directly PAK1, an oncogenic Rac/CDC42-dependent Ser/Thr kinase. It was demonstrated previously that PAK1 is essential for the growth of both NF1 and NF2 tumors. Thus, several anti-PAK1 drugs, including FK228 and CEP-1347, are being developed for the treatment of NF tumors. However, so far no effective NF therapeutic is available on the market. Since propolis, a very safe healthcare product from bee hives, contains anticancer ingredients called CAPE (caffeic acid phenethyl ester) or ARC (artepillin C), depending on the source, both of which block the oncogenic PAK1 signaling pathways, its potential therapeutic effect on NF tumors was explored in vivo. Here it is demonstrated that Bio 30, a CAPE-rich water-miscible extract of New Zealand (NZ) propolis suppressed completely the growth of a human NF1 cancer called MPNST (malignant peripheral nerve sheath tumor) and caused an almost complete regression of human NF2 tumor (Schwannoma), both grafted in nude mice. Although CAPE alone has never been used clinically, due to its poor bioavailability/water-solubility, Bio 30 contains plenty of lipids which solubilize CAPE, and also includes several other anticancer ingredients that seem to act synergistically with CAPE. Thus, it would be worth testing clinically to see if Bio 30 and other CAPE-rich propolis are useful for the treatment of NF patients.
Phytotherapy Research 09/2008; 23(2):226-30. · 2.40 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Schwannomas are benign tumors composed of dedifferentiated Schwann cells that form along peripheral nerves causing nerve compression often associated with pain and loss of function. Current surgical therapy involves total or subtotal surgical removal of the tumor, which may cause permanent nerve damage. In the present study, we explore an alternate means of therapy in which schwannomas are injected with a replication-conditional herpes simplex virus (HSV) vector to shrink the tumor through cell lysis during virus propagation. The oncolytic vector used, G47Delta, has deletions in HSV genes, which allow it to replicate selectively in dividing cells, sparing neurons. Two schwannoma cell lines were used to generate subcutaneous tumors in nude mice: HEI193, an immortalized human line previously established from an NF2 patient and NF2S-1, a newly generated spontaneous mouse line. Subcutaneous HEI193 tumors grew about ten times as fast as NF2S-1 tumors, and both regressed substantially following injection of G47Delta. Complete regression of HEI193 tumors was achieved in most animals, whereas all NF2S-1 tumors resumed growth within 2 weeks after vector injection. These studies provide a new schwannoma model for testing therapeutic strategies and demonstrate that oncolytic HSV vectors can be successfully used to shrink growing schwannomas.
Cancer Gene Therapy 06/2007; 14(5):460-7. · 2.55 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Although usually benign and focal, schwannomas associated with neurofibromatosis type 2 (NF2) can severely compromise neural function leading to paralysis, deafness and death through compression of critical nerves. Our previous studies have shown that schwannoma cells are highly infectable with HSV-1 vectors. In the present studies we explored use of both the oncolytic HSV-1 vector, G47delta, and an HSV-1 amplicon vector expressing caspase-1 under a P0 Schwann cell-specific promoter to treat experimental tumors. The immortalized human schwannoma line, HEI193 (House Ear Institute, Hung et al., 2002) was implanted subcutaneously into nude mice and formed slow growing tumors. Tumors (400 – 600 mm3) were injected with the G47delta vector (deleted for gamma 34.5, ribonucleotide reductase (ICP6) and ICP47) twice on baseline day 0 and 5 with 2 × 107 pfu/injection. Tumors volumes were reduced by 64.33% +/-15.6% over the following period of 18 days. Long term studies are underway to determine if tumor growth recurs. To reduce the potential of any damage to nerves through replication of vectors in associated schwannoma, we have also genereated an amplicon vector in which a fusion protein consisting of the apoptotic protein, caspase-1 and LacZ (Friedlander et al., 1997) is placed under the P0 Schwann cell promoter (Brown and Lemke, 1997). Infection of schwannoma, neuroblastoma and fibroblast cells in culture with helper virus-free amplicon vectors revealed LacZ expression only in schwannoma cells with their consequent death. Injections of this amplicon vector are now being tested for therapeutic effect in this experimental schwannoma model. Both these HSV vector treatment regimes offer the chance to reduce the size of schwannoma tumors, which in itself would be therapeutic, without causing damage to neurons.
[Show abstract][Hide abstract] ABSTRACT: Gene therapy for schwannomas was evaluated in two mouse models of neurofibromatosis type 2 (NF2): (1) a transgenic model in which mice express a dominant mutant form of merlin and spontaneously develop schwannomas, and (2) a xenograft model in which human schwannoma tissue is implanted subcutaneously into immune- compromised mice. In both models, schwannoma volumes were monitored by magnetic resonance imaging (MRI) and showed strong gadolinium enhancement typical of these tumors in humans. Both types of tumor were positive for the Schwann cell marker S100, and highly infectable with herpes simplex virus (HSV) vectors. Schwannomas were injected with an oncolytic HSV-1 recombinant virus vector, G47Delta, which has deletions in genes for ribonucleotide reductase (ICP6), gamma34.5, and ICP47. In the NF2 transgenic model, schwannomas were reduced by more than half their original size by 10 days after infection. In the case of subcutaneous schwannoma xenografts, reduction in size after infection occurred more slowly, with a mean reduction of onethird by 42 days after treatment. Schwannomas injected with control vehicles continued to grow slowly over time in both schwannoma models. These studies demonstrate the ability of an oncolytic recombinant HSV vector to reduce the volume of schwannoma tumors in NF2 tumor models in mice and extend the possible therapeutic applications of oncolytic vectors for benign tumors to reduce mass while minimizing nerve damage.
Human Gene Therapy 02/2006; 17(1):20-30. · 3.62 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Abstract: Voltage-gated ion channels generate electrical activity in excitable cells. As such, they are essential components of neuromuscular and neuronal systems, and are targeted by toxins from a wide variety of phyla, including the cnidarians. Here, we review cnidarian toxins known to target voltage-gated ion channels, the specific channel types targeted, and, where known, the sites of action of cnidarian toxins on different channels.
[Show abstract][Hide abstract] ABSTRACT: Despite the progress made in our understanding of the biology of neurofibromatosis (NF), the long-term clinical outcome for affected patients has not changed significantly in the past decades, and both NF1 and NF2 are still associated with a significant morbidity and a decreased life span. A number of NF1 and NF2 murine models have been generated to aid in the study of NF tumor biology and in the development of targeted therapies for NF patients. A single, universal pathological classification of the lesions generated in these murine models is essential for the validation of the models, for their analysis and comparison with other models, and for their future effective use in preclinical treatment trials. For the formulation of a pathological classification of these lesions, the WHO classification of human tumors was used as a reference. However, it was not adopted for the classification of the GEM lesions because of some important differences between the human and murine lesions. A novel classification scheme for peripheral nerve sheath tumors in murine models was therefore devised.
Cancer Research 06/2004; 64(10):3718-24. · 9.28 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Here we describe a novel method for imaging apoptosis in cells using a near-infrared fluorescent (NIRF) probe selective for caspase-1 (interleukin 1beta-converting enzyme, ICE). This biocompatible, optically quenched ICE-NIRF probe incorporates a peptide substrate, which can be selectively cleaved by caspase-1, resulting in the release of fluorescence signal. The specificity of this probe for caspase-1 is supported by various lines of evidence: 1) activation by purified caspase-1, but not another caspase in vitro; 2) activation of the probe by infection of cells with a herpes simplex virus amplicon vector (HGC-ICE-lacZ) expressing a catalytically active caspase-1-lacZ fusion protein; 3) inhibition of HGC-ICE-lacZ vector-induced activation of the probe by coincubation with the caspase-1 inhibitor YVAD-cmk, but not with a caspase-3 inhibitor; and 4) activation of the probe following standard methods of inducing apoptosis with staurosporine, ganciclovir, or ionizing radiation in culture. These results indicate that this novel ICE-NIRF probe can be used in monitoring endogenous and vector-expressed caspase-1 activity in cells. Furthermore, tumor implant experiments indicate that this ICE-NIRF probe can be used to detect caspase-1 activity in living animals. This novel ICE-NIRF probe should prove useful in monitoring endogenous and vector-expressed caspase-1 activity, and potentially apoptosis in cell culture and in vivo.
[Show abstract][Hide abstract] ABSTRACT: The ability to noninvasively track the migration, engraftment, and proliferation of neural progenitor cells (NPCs) has significant clinical and research implications. The purpose of our study was to explore the macroscopic migratory capabilities of NPCs toward brain tumors after implantation into nude mice. We stably transfected C17.2 NPCs with the firefly luciferase gene (F-luc) and implanted cells into (1) the contralateral brain parenchyma (2 x 10(6) cells), (2) the ventricles (2 x 10(6) cells), (3) the vasculature (1 x 10(5) cells), or (4) the intraperitoneal cavity (5 x 10(6) cells) of mice bearing intracranial gliomas (Gli36). Using serial bioluminescence imaging, migration of parenchymally injected cells was observed across the corpus callosum, first detected at 1 week, with maximal density at the tumor site 2-3 weeks after implantation. Similar patterns were also observed with intraventricular injections; however, tumors were populated earlier, presumably because of the shorter distance to travel. Intravenous injections resulted in more modest tumoral NPC populations, whereas virtually no cells could be identified in tumors after intraperitoneal injection. These results confirm the migratory capability of NPCs over considerable distances and their preferential accumulation in brain tumors on CNS rather than peripheral injection.
Human Gene Therapy 10/2003; 14(13):1247-54. · 3.62 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Spontaneous schwannomas were detected by magnetic resonance imaging (MRI) in a transgenic murine model of neurofibromatosis type 2 (NF2) expressing a dominant mutant form of merlin under the Schwann cell-specific P0 promoter. Approximately 85% of the investigated mice showed putative tumors by 24 months of age. Specifically, 21% of the mice showed tumors in the intercostal muscles, 14% in the limb muscles, 7% in the spinal cord and spinal ganglia, 7% in the external ear, 14% in the muscle of the abdominal region, and 7% in the intestine; 66% of the female mice had uterine tumors. Multiple tumors were detected by MRI in 21% of mice. The tumors were isointense with muscle by T1-weighted MRI, showed strong enhancement following administration of gadolinium-DTPA, and were markedly hyperintense by T2-weighted MRI, all hallmarks of the clinical manifestation. Hematoxylin and eosin staining and immunohistochemistry indicated that the tumors consisted of schwannomas and Schwann cell hyperplasias. The lesions stained positively for S-100 protein and a marker antigen for the mutated transgenic NF2 protein, confirming that the imaged tumors and areas of hyperplasia were of Schwann cell origin and expressed the mutated NF2 protein. Tumors were highly infectable with a recombinant herpes simplex virus type 1 vector, hrR3, which contains the reporter gene, lacZ. The ability to develop schwannoma growth with a noninvasive imaging technique will allow assessment of therapeutic interventions.