An anti-diabetic drug targets NEET (CISD) proteins through destabilization of their [2Fe-2S] clusters

Elevated levels of mitochondrial iron and reactive oxygen species (ROS) accompany the progression of diabetes, negatively impacting insulin production and secretion from pancreatic cells. In search for a tool to reduce mitochondrial iron and ROS levels, we arrived at a molecule that destabilizes the [2Fe-2S] clusters of NEET proteins (M1). Treatment of db/db diabetic mice with M1 improved hyperglycemia, without the weight gain observed with alternative treatments such as rosiglitazone. The molecular interactions of M1 with the NEET proteins mNT and NAF-1 were determined by X-crystallography. The possibility of controlling diabetes by molecules that destabilize the [2Fe-2S] clusters of NEET proteins, thereby reducing iron-mediated oxidative stress, opens a new route for managing metabolic aberration such as in diabetes.

Photosynthesis Z-Scheme biomimicry: Photosystem I/BiVO4 photo-bioelectrochemical cell for donor-free bias-free electrical power generation

Photo-bioelectrochemical cells that are based on photosynthetic proteins are drawing increased attention for both fundamental and applied research. While novel photosynthetic based systems have been introduced, further optimization in terms of stability and efficiency is required. Photosystem I has been utilized extensively in bioelectronic devices, often in conjugation with viologen moieties which act as electron acceptors. It has been shown previously that a partial reduction of oxygen to H₂O₂ can facilitate damage to proteins hence, limits their long-term activation. Here, we show a newly developed bias-free, donor-free photo-bioelectrochemical system that mimics the natural photosynthetic Z-scheme. Polymethylene blue and polybutyl-viologen were tailored to fit the photosystem I donor and acceptor sides, respectively. Furthermore, we show that by coupling the developed biocathode with a BiVO₄/CoP photoanode, a power output of 25 μW/cm² can be achieved. We further show that our configuration can minimize the damaging effect of H₂O₂ by two different pathways, oxidation at the photoanode or reduction by the polymethylene blue layer at the biocathode.

Activation of apoptosis in NAF-1-deficient human epithelial breast cancer cells

Maintaining iron (Fe) ion and reactive oxygen species homeostasis is essential for cellular function, mitochondrial integrity and the regulation of cell death pathways, and is recognized as a key process underlying the molecular basis of aging and various diseases, such as diabetes, neurodegenerative diseases and cancer. Nutrient-deprivation autophagy factor 1 (NAF-1; also known as CISD2) belongs to a newly discovered class of Fe-sulfur proteins that are localized to the outer mitochondrial membrane and the endoplasmic reticulum. It has been implicated in regulating homeostasis of Fe ions, as well as the activation of autophagy through interaction with BCL-2. Here we show that small hairpin (sh)RNA-mediated suppression of NAF-1 results in the activation of apoptosis in epithelial breast cancer cells and xenograft tumors. Suppression of NAF-1 resulted in increased uptake of Fe ions into cells, a metabolic shift that rendered cells more susceptible to a glycolysis inhibitor, and the activation of cellular stress pathways that are associated with HIF1α. Our studies suggest that NAF-1 is a major player in the metabolic regulation of breast cancer cells through its effects on cellular Fe ion distribution, mitochondrial metabolism and the induction of apoptosis.

Structure-function analysis of NEET proteins uncovers their role as key regulators of iron and ROS homeostasis in health and disease

A novel family of 2Fe-2S proteins, the NEET family, was discovered during the last decade in numerous organisms, including archea, bacteria, algae, plant and human; suggesting an evolutionary-conserved function, potentially mediated by their CDGSH Iron-Sulfur Domain. In human, three NEET members encoded by the CISD1-3 genes were identified. The structures of CISD1 (mitoNEET, mNT), CISD2 (NAF-1), and the plant At-NEET uncovered a homodimer with a unique "NEET fold", as well as two distinct domains: a beta-cap and a 2Fe-2S cluster-binding domain. The 2Fe-2S clusters of NEET proteins were found to be coordinated by a novel 3Cys:1His structure that is relatively labile compared to other 2Fe-2S proteins and is the reason of the NEETs' clusters could be transferred to apo-acceptor protein(s) or mitochondria. Positioned at the protein surface, the NEET's 2Fe-2S's coordinating His is exposed to protonation upon changes in its environment, potentially suggesting a sensing function for this residue. Studies in different model systems demonstrated a role for NAF-1 and mNT in the regulation of cellular iron, calcium and ROS homeostasis, and uncovered a key role for NEET proteins in critical processes, such as cancer cell proliferation and tumor growth, lipid and glucose homeostasis in obesity and diabetes, control of autophagy, longevity in mice, and senescence in plants. Abnormal regulation of NEET proteins was consequently found to result in multiple health conditions, and aberrant splicing of NAF-1 was found to be a causative of the neurological genetic disorder Wolfram Syndrome 2. Here we review the discovery of NEET proteins, their structural, biochemical and biophysical characterization, and their most recent structure-function analyses. We additionally highlight future avenues of research focused on NEET proteins and propose an essential role for NEETs in health and disease. This article is part of a Special Issue entitled: Fe/S proteins: Analysis, structure, function, biogenesis and diseases.

Photosynthetic reaction center-functionalized electrodes for photo-bioelectrochemical cells

During the last few years, intensive research efforts have been directed toward the application of several highly efficient light-harvesting photosynthetic proteins, including reaction centers (RCs), photosystem I (PSI), and photosystem II (PSII), as key components in the light-triggered generation of fuels or electrical power. This review highlights recent advances for the nano-engineering of photo-bioelectrochemical cells through the assembly of the photosynthetic proteins on electrode surfaces. Various strategies to immobilize the photosynthetic complexes on conductive surfaces and different methodologies to electrically wire them with the electrode supports are presented. The different photoelectrochemical systems exhibit a wide range of photocurrent intensities and power outputs that sharply depend on the nano-engineering strategy and the electroactive components. Such cells are promising candidates for a future production of biologically-driven solar power.

Photosystem I (PSI)/Photosystem II (PSII)-based photo-bioelectrochemical cells revealing directional generation of photocurrents

Layered assemblies of photosystem I, PSI, and/or photosystem II, PSII, on ITO electrodes are constructed using a layer-by-layer deposition process, where poly N,N'-dibenzyl-4,4'-bipyridinium (poly-benzyl viologen, PBV(2+) ) is used as an inter-protein "glue". While the layered assembly of PSI generates an anodic photocurrent only in the presence of a sacrificial electron donor system, such as dichlorophenol indophenol (DCPIP)/ascorbate, the PSII-modified electrode leads, upon irradiation, to the formation of an anodic photocurrent (while evolving oxygen), in the absence of any sacrificial component. The photocurrent is generated by transferring the electrons from the PSII units to the PBV(2+) redox polymer. The charge-separated species allow, then, the injection of the electrons to the electrode, with the concomitant evolution of O2 . A layered assembly, consisting of a PSI layer attached to a layer of PSII by the redox polymer PBV(2+) , leads to an anodic photocurrent that is 2-fold higher, as compared to the anodic photocurrent generated by a PSII-modified electrode. This observation is attributed to an enhanced charge separation in the two-photosystem assembly. By the further nano-engineering of the two photosystems on the electrode using two different redox polymers, vectorial electron transfer to the electrode is demonstrated, resulting in a ca. 6-fold enhancement in the photocurrent. The reversed bi-layer assembly, consisting of a PSII layer linked to a layer of PSI by the PBV(2+) redox polymer, yields, upon irradiation, an inefficient cathodic current. This observation is attributed to a mixture of photoinduced electron transfer reactions of opposing effects on the photocurrent directions in the two-photosystem assembly.

Nutrient-deprivation autophagy factor-1 (NAF-1): biochemical properties of a novel cellular target for anti-diabetic drugs

Nutrient-deprivation autophagy factor-1 (NAF-1) (synonyms: Cisd2, Eris, Miner1, and Noxp70) is a [2Fe-2S] cluster protein immune-detected both in endoplasmic reticulum (ER) and mitochondrial outer membrane. It was implicated in human pathology (Wolfram Syndrome 2) and in BCL-2 mediated antagonization of Beclin 1-dependent autophagy and depression of ER calcium stores. To gain insights about NAF-1 functions, we investigated the biochemical properties of its 2Fe-2S cluster and sensitivity of those properties to small molecules. The structure of the soluble domain of NAF-1 shows that it forms a homodimer with each protomer containing a [2Fe-2S] cluster bound by 3 Cys and one His. NAF-1 has shown the unusual abilities to transfer its 2Fe-2S cluster to an apo-acceptor protein (followed in vitro by spectrophotometry and by native PAGE electrophoresis) and to transfer iron to intact mitochondria in cell models (monitored by fluorescence imaging with iron fluorescent sensors targeted to mitochondria). Importantly, the drug pioglitazone abrogates NAF-1's ability to transfer the cluster to acceptor proteins and iron to mitochondria. Similar effects were found for the anti-diabetes and longevity-promoting antioxidant resveratrol. These results reveal NAF-1 as a previously unidentified cell target of anti-diabetes thiazolidinedione drugs like pioglitazone and of the natural product resveratrol, both of which interact with the protein and stabilize its labile [2Fe-2S] cluster.

Electrochemical switching of photoelectrochemical processes at CdS QDs and photosystem I-modified electrodes

Photoactive inorganic CdS quantum dots (QDs) or the native photosystem I (PSI) is immobilized onto a pyrroloquinoline quinone (PQQ) monolayer linked to Au electrodes to yield hybrid relay/QDs (or photosystem) assemblies. By the electrochemical biasing of the electrode potential, the relay units are retained in their oxidized PQQ or reduced PQQH(2) states. The oxidized or reduced states of the relay units dictate the direction of the photocurrent (anodic or cathodic). By the cyclic biasing of the electrode potential between the values E ≥ -0.05 V and E ≤ -0.3 V vs Ag quasi-reference electrode (Ag QRE), retaining the relay units in the oxidized PQQ or reduced PQQH(2) states, the photocurrents are respectively switched between anodic and cathodic values. Different configurations of electrically switchable photoelectrochemical systems are described: (i) the PQQ/CdS QDs/(triethanolamine, TEOA) or PQQ/PSI/(ascorbic acid/dichlorophenolindophenol, DCPIP) systems, leading to anodic photocurrents; (ii) the PQQ/CdS QDs (or PSI)/(flavin adenine dinucleotide) systems, leading to cathodic photocurrents; (iii) the PQQ/CdS QDs (or PSI)/(O(2)) switchable systems, leading to cyclic anodic/cathodic switching of the photocurrents.

Characterization of Arabidopsis NEET reveals an ancient role for NEET proteins in iron metabolism

The NEET family is a newly discovered group of proteins involved in a diverse array of biological processes, including autophagy, apoptosis, aging, diabetes, and reactive oxygen homeostasis. They form a novel structure, the NEET fold, in which two protomers intertwine to form a two-domain motif, a cap, and a unique redox-active labile 2Fe-2S cluster binding domain. To accelerate the functional study of NEET proteins, as well as to examine whether they have an evolutionarily conserved role, we identified and characterized a plant NEET protein. Here, we show that the Arabidopsis thaliana At5g51720 protein (At-NEET) displays biochemical, structural, and biophysical characteristics of a NEET protein. Phenotypic characterization of At-NEET revealed a key role for this protein in plant development, senescence, reactive oxygen homeostasis, and Fe metabolism. A role in Fe metabolism was further supported by biochemical and cell biology studies of At-NEET in plant and mammalian cells, as well as mutational analysis of its cluster binding domain. Our findings support the hypothesis that NEET proteins have an ancient role in cells associated with Fe metabolism.

Allostery in the ferredoxin protein motif does not involve a conformational switch

Regulation of protein function via cracking, or local unfolding and refolding of substructures, is becoming a widely recognized mechanism of functional control. Oftentimes, cracking events are localized to secondary and tertiary structure interactions between domains that control the optimal position for catalysis and/or the formation of protein complexes. Small changes in free energy associated with ligand binding, phosphorylation, etc., can tip the balance and provide a regulatory functional switch. However, understanding the factors controlling function in single-domain proteins is still a significant challenge to structural biologists. We investigated the functional landscape of a single-domain plant-type ferredoxin protein and the effect of a distal loop on the electron-transfer center. We find the global stability and structure are minimally perturbed with mutation, whereas the functional properties are altered. Specifically, truncating the L1,2 loop does not lead to large-scale changes in the structure, determined via X-ray crystallography. Further, the overall thermal stability of the protein is only marginally perturbed by the mutation. However, even though the mutation is distal to the iron-sulfur cluster (∼20 Å), it leads to a significant change in the redox potential of the iron-sulfur cluster (57 mV). Structure-based all-atom simulations indicate correlated dynamical changes between the surface-exposed loop and the iron-sulfur cluster-binding region. Our results suggest intrinsic communication channels within the ferredoxin fold, composed of many short-range interactions, lead to the propagation of long-range signals. Accordingly, protein interface interactions that involve L1,2 could potentially signal functional changes in distal regions, similar to what is observed in other allosteric systems.

An unusual guanyl oligonucleotide regulates cellulose synthesis in Acetobacter xylinum

The mechanism of GTP-specific activation of the membrane-bound cellulose synthase system of Acetobacter xylinum has been further elucidated. The supernatant fraction derived from washed membranes of this organism contains an enzyme which reacts with GTP to form a low molecular mass, heat-stable compound,tentatively characterized as a cyclic oligonuleotide composed of GMP residues, which is the immediate activator of the cellulose synthase. This activation is reversed by a membrane-bound enzyme that degrades the activator; the latter enzyme is inhibited by Ca (2+). It is suggested that the interaction between these enzymes and nucleotide derivatives, mediated by Ca (2+), may regulate cellulose synthesis in VIVO.

A phase II study of G17DT in gastric carcinoma

PURPOSE

G17DT is a gastrin immunogen, raising antibodies that blockade gastrin-stimulated growth. The aim of the study was to characterise antibody response and assess safety and tolerability of G17DT given to patients with gastric cancer.

EXPERIMENTAL DESIGN

G17DT was administered to 52 patients with gastric adenocarcinoma at weeks 0, 2 and 6 by intramuscular injection at doses of 10, 100 and 250 microg. Antibody levels were measured by an ELISA assay. A radioligand displacement assay determined the ability of G17DT-immunised patients' sera to inhibit binding of 125IG17 to cholecystokinin (CCK)-2 receptors.

RESULTS

By week 12 of the study, 6/12 evaluable stage I-III patients achieved an antibody response in the 10 microg group, 7/11 in the 100 microg group, and 11/12 in the 250 microg group. Stage IV patients dosed at 250 microg achieved a similar response rate to stage I-III patients dosed at 10 or 100 microg. G17DT was well tolerated in 47/52 patients. Two patients suffered significant adverse reactions including injection site pain and abscess. G17DT antibodies displaced iodinated gastrin from CCK-2 receptors, with the level of displacement correlating with antibody titre.

CONCLUSIONS

G17DT immunisation is a well-tolerated method of raising functional antibodies to 17 amino acid gastrin forms in patients with gastric carcinomas.

Phase II study of anti-gastrin-17 antibodies, raised to G17DT, in advanced pancreatic cancer

PURPOSE

The prognosis for advanced pancreatic cancer remains poor. Gastrin acts as a growth factor for pancreatic cancer. We describe the first study of the antigastrin immunogen G17DT in pancreatic cancer. Our aims were to determine the antibody response, safety, tolerability, and preliminary evidence of efficacy of G17DT in advanced pancreatic cancer.

PATIENTS AND METHODS

Thirty patients with advanced pancreatic cancer were immunized with three doses of either 100 micro g or 250 micro g of G17DT.

RESULTS

In the whole group, 20 (67%) of 30 patients produced an antibody response. The 250- micro g dose resulted in a significantly greater response rate of 82% compared with 46% for the 100- micro g group (P =.018). The most significant side effects, seen in three patients, were local abscess and/or fever. The median survival for the whole group from the date of the first immunization was 187 days; median survival was 217 days for the antibody responders and 121 days for the antibody nonresponders. The difference in survival between the antibody responders and nonresponders was significant (P =.0023).

CONCLUSION

Patients with advanced pancreatic cancer are able to mount an adequate antibody response to G17DT. The 250- micro g dose is superior to the 100- micro g dose, and it appears to be generally well tolerated. Antibody responders demonstrate significantly greater survival than antibody nonresponders. Phase III studies are currently underway in order to determine efficacy.

Gastrimmune-induced antigastrin-17 antibodies inhibit acid secretion in a rat fistula model

BACKGROUND

Gastrimmune is an immunogenic form of gastrin. It raises in situ antibodies against two proliferative forms of gastrin: amidated and glycine-extended gastrin-17. It has been shown to have a therapeutic action in several in vivo tumour models. Following immunization, due to the complex equilibrium that exists between the antibodies and gastrin, it is not technically feasible to assay for free gastrin.

AIM

To determine the effect of Gastrimmune-induced antigastrin antibodies on acid secretion.

METHOD

A rat gastric fistula model was used. Animals (six per group) were immunized with a control immunogen or ascending doses of Gastrimmune. Acid output was measured following infusion of increasing doses of gastrin-17 and pentagastrin.

RESULTS

Gastrimmune-induced antibodies significantly reduced gastrin-17-stimulated acid output compared to control animals (Gastrimmune at 200 microg/rat vs. control; acid output following 30 ng gastrin-17, 0.01 vs. 0.16, P < 0.001; following 120 ng gastrin-17, 0.022 vs. 0.29, P < 0.001).

CONCLUSIONS

Gastrimmune significantly inhibits gastrin-17-stimulated acid output. This biological assay suggests that the antigastrin antibodies effectively bind gastrin-17. In addition to its use as an antineoplastic agent, Gastrimmune may have a role as an acid-decreasing agent in oesophagogastric pathology.

Effect of gastrin and anti-gastrin antibodies on proliferation of hepatocyte cell lines

Gastrin (G-17) and its precursor glycine-extended gastrin (G-17-gly) have been shown to be trophic to some gastrointestinal tumors. This in vitro study assessed the effect of G-17, G-17-gly, anti-gastrin antibodies (anti-G-17), and the CCK-B receptor antagonist PD135,158 on three hepatoma cell lines (PLC/PRF/5, HepG2 and MCA-RH7777) and an embryonic liver cell line (WRL68). The pancreatic adenocarcinoma cell line AR42J was used as a positive control. G-17 and G-17-gly caused significant proliferation of AR42J and WRL68 cell lines. G-17-gly but not G-17 induced significant proliferation of the PLC/PRF/5 cell line. Anti-G-17 and PD135,158 significantly inhibited unstimulated AR42J and WRL68 cell lines. Anti-G-17 also inhibited the proliferative effects of G-17 and G-17-gly on AR42J, WRL68, and PLC/PRF/5 cell lines, whereas PD135,158 inhibited the proliferative effect of G-17 only. G-17 and G-17-gly as well as anti-G-17 and PD135,158 had no effect on HepG2 and MCA-RH77777 cell lines. It is concluded that G-17-stimulated proliferation is mediated via the CCK-B receptor and G-17-gly via a separate, as yet uncharacterized, receptor. There may therefore be a role for gastrin in embryonic hepatocellular proliferation and perhaps also in the proliferation of some hepatocellular tumors.

An insight into the assembly and organization of photosystem I complex in the thylakoid membranes of the thermophilic cyanobacterium, Mastigocladus laminosus

The present study characterizes the assembly and organization of Photosystem I (PSI) complex, and its individual subunits into the thylakoid membranes of the thermophilic cyanobacterium, Mastigocladus laminosus. PSI is a multiprotein complex that contains peripheral as well as integral subunits. Hence, it serves as a suitable model system for understanding the formation and organization of membrane protein complexes. In the present study, two peripheral cytosol facing subunits of PSI, namely, PsaD and PsaE were overexpressed in E. coli and used for assembly studies. The gene encoding PsaK, an integral membrane spanning subunit of PSI, was cloned and the deduced amino acid sequence revealed PsaK to have two transmembrane alpha-helices. The characterization of the in vitro assembly of the peripheral subunits, PsaD and PsaE, as well as of the integral subunit, PsaK, was performed by incubating each subunit with thylakoids isolated from Mastigocladus laminosus. All three subunits studied were found to assemble into the thylakoids in a spontaneous mechanism, showing no requirement for cytosolic factors or NTP's (nucleotide 5'-triphosphate). Nevertheless, further characterization of the assembly of PsaK revealed its membrane integration to be most efficient at 55 degrees C. The associations and protein-protein interactions between different subunits within the assembled PSI complex were directly quantified by measurements performed using the BIACORE technology. The preliminary results indicated the existence of specific interaction between PsaD and PsaE, and revealed a very high binding affinity between PsaD and the PSI electron acceptor ferridoxin (Kd = 5.8 x 10(-11) M). PsaE has exhibited a much lower binding affinity for ferridoxin (Kd = 3.1 x 10(-5) M), thereby supporting the possibility of PsaE being one of the subunits responsible for the dissociation of ferridoxin from the PSI complex.

Phase I/II study of G17-DT, an anti-gastrin immunogen, in advanced colorectal cancer

Gastrin is a growth factor for colorectal cancer, and therefore, anti-gastrin hormone therapy has a potential role in treatment of this disease. The gastrin immunogen gastrin-17-diphtheria toxoid (G17-DT; Gastrimmune) produces anti-G17 antibodies that have been shown to be effective in the treatment of colorectal carcinoma in preclinical models. Fifty patients with advanced colorectal cancer were treated with G17-DT in a multicenter, sequential group, open label Phase I/II study. Primary injections with two booster doses were given by i.m. injection. The main aim of the study was to assess the safety and efficacy of the production of antigastrin antibodies. Locally developed and standard WHO toxicity measurements with RIA and Scatchard analysis for antibody assessment were used. One center measured tumor response radiologically. Eighty % of patients produced a measurable antibody response. Antibodies of high affinity (median Kd, 0.295 nM; interquartile range, 0.16-0.41 nM) were detected between 4 and 12 weeks after primary injection. The antigen binding capacity was high at 2.8 x 10(-9) M (interquartile range, 5.1 x 10(-10) to 7.25 x 10(-9) M). The treatment was well tolerated with no systemic side effects seen. Myalgia at the injection site was seen in 46% of patients with severe pain caused by the formation of a sterile abscess seen in 14% of patients. The abscesses were all drained under ultrasound guidance, and the patients recovered fully within 6 weeks. No radiological responses were seen, but two patients had stable disease. G17-DT immunization produces anti-G17 antibodies in patients with advanced colorectal cancer. The antibodies were of an affinity high enough to compete with the cholecystokinin B/gastrin receptor for G17 binding with adequate capacity to neutralize postprandial gastrin surges. Additional dose-ranging studies have been performed in patients with gastric cancer using 100- and 200-microg doses of G17-DT formulated without adjuvant and the emulsifier aluminum monostearate. In addition, the effect of immunizing at different time intervals has been determined.

Anti-GnRH antibodies can induce castrate levels of testosterone in patients with advanced prostate cancer

D17DT consists of the GnRH decapeptide linked to diphtheria toxoid. The aim of this pilot study was to assess the tolerance of D17DT and the production of anti-GnRH antibodies from two doses, 30 and 100 microg, in patients with locally advanced prostate cancer. Twelve patients with histologically proven prostate cancer in whom hormonal therapy was indicated were recruited. Patients received either 30 or 100 microg given intramuscularly on three separate occasions over six weeks. Patients were followed up and blood was taken for estimation of serum testosterone, PSA and anti-GnRH antibody titre. Overall the drug was well tolerated. In 5 patients a significant reduction in serum testosterone and PSA was seen. Castrate levels of testosterone were achieved in 4 and maintained for up to 9 months. Patients with the highest antibody titre had the best response in terms of testosterone suppression. This study shows that it is possible to immunize a patient with prostate cancer against GnRH to induce castrate levels of testosterone. This state appears to be reversible. This novel form of immunotherapy may have advantages over conventional forms of hormonal therapy and further studies are warranted in order to try and increase the proportion of responders.

Transforming growth factor-alpha-mediated growth pathways in human gastro-intestinal cell lines in relation to the gastrin autocrine pathway

Epidermal growth factor (EGF) and transforming growth factor-alpha (TGF-alpha) increase transcription of the gastrin gene, and the gastrin peptide may be phosphorylated by EGF-stimulated tyrosine kinase. Our aims were to compare EGF/TGF-alpha interactions in 2 human gastro-intestinal cell lines: MGLVA1, with a strong gastrin autocrine pathway, and C170HM2, with a weak pathway. Both cell lines expressed the TGF-alpha gene. MGLVA1 expressed TGF-alpha protein as determined by immuno-cytochemistry, which was absent in C170HM2. Both cell lines expressed the same level of EGF receptors, as assessed by flow cytometry; however, MGLVA1 did not have enhanced in vitro proliferation in response to EGF or TGF-alpha, unlike C170HM2. The basal growth of MGLVA1 was inhibited by anti-sera against TGF-alpha, the EGF receptor and G17. C170HM2 was not inhibited by any of the anti-sera. Neutralisation of TGF-alpha resulted in undetectable cell-associated progastrin levels in MGLVA1 (untreated had 391.7 fmol/5 x 10(6) cells). The progastrin level of C170HM2 remained unaffected. Tyrosine kinase activity, as assessed by phosphopeptide concentration, of unstimulated MGLVA1 was 2.6 times higher than that of C170HM2 in the cell membrane fraction (0.097 compared to 0.037 microg/mg protein, p < 0.001) and 4.8 times higher in the cytosolic fraction (0.269 compared to 0.056 microg/mg protein, p < 0.05). Following treatment with EGF, the phosphopeptide concentration increased in both the membrane and cytosolic fractions of both cell lines. Tyrphostin B42, which inhibits autophosphorylation of the EGF receptor, inhibited the basal growth of MGLVA1 (IC(50) 1.3 microM) and C170HM2 (9.5 microM, p < 0.05 from MGLVA1). Herbimycin, which inhibits pp60(c-src) kinase, reduced the basal growth of MGLVA1 (0.67 microM) but not C170HM2. Immunofluorescence studies confirmed the presence of tyrosine-phosphorylated proteins and pp60(c-src) within the cytoplasm of unstimulated MGLVA1 cells. There was no specific immunofluorescence for either parameter in C170HM2 cells until after treatment with EGF.

Comparison of bone mineral density of the phalanges, lumbar spine, hip, and forearm for the assessment of osteoporosis in postmenopausal women

The objective of this study was to compare peripheral bone mineral density (BMD) of the phalanges with BMD of the lumbar spine, total hip, femoral neck, and forearm and to determine the clinical value of measuring a single peripheral site (phalanges) in identifying postmenopausal women with osteoporosis. BMD was measured by dual energy X-ray absorptiometry using the accuDEXA((R)) (ADXA-finger) (Schick, New York, NY) and the QDR-4500 (DXA-lumbar spine, hip, forearm) (Hologic, Waltham, MA). Correlation coefficients between ADXA and DXA of the lumbar spine, total hip, femoral neck and one third radial site ranged from 0.53 to 0.73. The sensitivity of an ADXA T-score of -2.5 in identifying patients with a DXA T-score of < or = -2.5 at the femoral neck was 35%. An ADXA T-score cut point of -1.0 improved the sensitivity of ADXA in identifying patients with a femoral neck T-score of < or = -2.5 (85%), but the specificity declined from 88 to 49%. There was substantial discordance in the diagnosis of osteoporosis when a single site was measured, regardless of technique. Within the limitations of single-site measurements, BMD measured by ADXA has adequate sensitivity to identify women with low BMD at the femoral neck, if an appropriate T-score criterion is used.

A comparison of the therapeutic effectiveness of gastrin neutralisation in two human gastric cancer models: relation to endocrine and autocrine/paracrine gastrin mediated growth

BACKGROUND

Gastrin is a growth factor for established tumours.

AIMS

To investigate the therapeutic effect of antibodies, raised against the Gastrimmune immunogen, which neutralise the glycine extended and carboxy amidated forms of gastrin 17 in two human gastric cancer models.

METHODS

MGLVA1 cells (which have a gastrin autocrine/paracrine phenotype) and ST16 cells (which have an endocrine phenotype) were injected into the peritoneal cavity of SCID mice. Peritoneal tumours, ascites, and cachexia formation occurred, with the monitored endpoint being morbidity.

RESULTS

In MGLVA1 cells, intravenous administration of antibodies raised against Gastrimmune increased the 50% median survived by 25% at three different initial cell seeding concentrations (1 x 10(6)-5 x 10(5) per mouse). In ST16 cells, the effect of Gastrimmune induced antibodies on time to morbidity was greatest at the lowest cell seeding concentration (5 x 10(5) cells/mouse) with the 50% median survival increased by 74% and overall survival achieved in 38% of the mice.

CONCLUSIONS

Gastrimmune may have potential therapeutic benefit on gastrin sensitive gastric tumours and may interact with both endocrine and autocrine mediated growth pathways.

Demonstration of new sites of expression of the CCK-B/gastrin receptor in pancreatic acinar AR42J cells using immunoelectron microscopy

The CCK-B/gastrin receptor has been characterised in both normal and tumour tissues. Endocytosis of the CCK-B/gastrin receptor has recently been demonstrated and this has similarly been described for other peptide receptors. In addition, ligand and ligand-receptor translocation to the nucleus has been demonstrated for other peptides. The aim of this study was to identify the sites of expression of the CCK-B/gastrin receptor in the known CCK-B/gastrin receptor bearing pancreatic acinar AR42J cells. The specificity of the CCK-B/gastrin receptor antibody (alpha-CCKBR-Ser antibody) was demonstrated by inhibition ELISA studies, radioligand inhibition studies and immunofluorescence binding studies on AR42J cells. Western blotting and immunogold electron microscopy techniques were used to identify the receptor in AR42J cell preparations. The affinity purified alpha-CCKBR-Ser antibody was shown to be specific for the CCK-B/gastrin receptor. The receptor was expressed on the cell membrane, in the cytoplasm and within the nucleus. Isoforms of the receptor protein identified in extra-nuclear and nuclear extracts ranged in molecular weight from 58 to 66 kDa. We conclude that the CCK-B/gastrin receptor is not only expressed on the cell membrane, but also in the cytoplasm and nucleus of AR42J pancreatic acinar cells.

Antibodies raised by gastrimmune inhibit the spontaneous metastasis of a human colorectal tumour, AP5LV

Both precursor forms of gastrin and mature amidated gastrin peptides can enhance proliferation of colorectal tumours and may regulate growth in an autocrine manner. The purpose of this study was to evaluate the effect of neutralization of precursor and amidated gastrin on primary and secondary in vivo growth of a human colorectal tumour. The human colorectal cell line, AP5LV, when injected into the muscle layer of the abdominal wall of severe combined immunodeficient (SCID) mice, grows as a well-vascularized primary tumour and metastasis to the lung. AP5LV expressed the precursor gastrin forms; progastrin and glycine-extended gastrin and gastrin/CCKB receptors, as assessed by immunocytochemistry. Gastrimmune is a gastrin immunogen in which the amino terminus of the gastrin-17 molecule is linked to diphtheria toxoid and induces antibodies which neutralise the amidated and glycine-extended forms of gastrin-17. Rabbit antiserum, raised against Gastrimmune, was administered intravenously into SCID mice bearing AP5LV tumours. Control animals were treated with antiserum raised against diphtheria toxoid only. Antibodies raised against Gastrimmune significantly limited the growth of primary AP5LV tumours, as assessed by median cross-sectional area (controls = 244 mm2; antibody-treated = 179 mm2; P = 0.033). In addition Gastrimmune-induced antiserum limited the growth of lung metastasis as assessed by nodule number (controls = 3.5; antibody-treated = 1.0; P = 0.0001) and nodule cross-sectional as assessed by image analysis (controls = 11.9 mm2; antibody-treated = 3.75 mm2; P = 0.0064). In conclusion in vivo neutralization of gastrin forms, which may potentially be fueling growth by an autocrine pathway, inhibited both primary growth and, to a greater degree, lung metastasis of a human colorectal tumour cell line. Immunization against tumour-associated gastrin forms may provide an effective therapy for advanced colorectal cancer.

Anti-gonadotrophin releasing hormone antibodies inhibit the growth of MCF7 human breast cancer xenografts

The human breast cancer cell line (MCF7) was established as xenografts in intact female nude mice. Xenografts did not require oestrogen supplementation for growth, although oestrogen supplementation caused more rapid tumour growth. GnRH Pharmaccine is an immunogen composed of gonadotrophin releasing hormone (GnRH) linked to diphtheria toxoid. Anti-GnRH antibodies purified from the serum of rabbits immunized with GnRH Pharmaccine, were used to passively immunize nude mice. In mice treated with anti-GnRH antibodies, xenograft growth was significantly inhibited relative to controls (median times of 71 and 29 days respectively taken for tumours to attain a predetermined cross-sectional area of 200 mm2, P < 0.001). The inhibition of tumour growth achieved by anti-GnRH antibodies was not significantly different from that produced by the anti-oestrogen, tamoxifen (59 days). Ovarian/uterine weights were reduced by 61% (P < 0.001) in anti-GnRH antibody-treated animals compared with controls. Histologically there was underdevelopment and atrophy of the reproductive organs. Serum levels of both oestrogen and luteinizing hormone were reduced by treatment with anti-GnRH antibodies (to 24.9% and 53% respectively of levels in controls, both P = 0.04). It is postulated that one of the mechanisms by which anti-GnRH antibody treatment inhibits tumour growth is indirectly, by reducing serum oestrogen levels.

A comparison of an anti-gastrin antibody and cytotoxic drugs in the therapy of human gastric ascites in SCID mice

The therapeutic effect of antibodies raised by the immunogen Gastrimmune was compared with both a CCKB/gastrin receptor antagonist, CI-988, and 5-Fluorouracil/leucovorin in a gastric cancer model. The human gastric ascites cell line, MGLVA1asc, produced and secreted progastrin and glycine-extended gastrin as determined by radioimmunoassay and immunocytochemistry. Cells were also stained with an antiserum directed against the human CCKB/gastrin receptor. MGLVAI asc cells were injected i.p. into SCID mice. Antibodies raised by Gastrimmune immunization of rabbits (affinity for G17 of 0.15 nM and GlyG17 of 0.47 nM) were passively infused i.p. and significantly enhanced survival by up to 5 days (p=0.0024 from vehicle controls). The enhancement in survival was not significantly different from that achieved by treatment with 5-Fluorouracil and leucovorin. A CCKB/gastrin receptor antagonist, CI-988, did not affect survival with cells injected at 7.5 x 10(5) cells/mouse but significantly increased the survival of mice injected with a lower cell innoculum of 5 x 10(5) cells/mouse from 30 to 35 days (p=0.0186). At this lower innoculum antibodies raised by Gastrimmune induced complete survival in 2 animals with the remaining dead by day 36 (p=0.0022). Thus, both endocrine and autocrine pathways mediated by precursor and mature gastrin molecules may be jointly operational in the gastric cancer scenario and may be important targets for therapeutic agents.

Expression and processing of gastrin in hepatocellular carcinoma, fibrolamellar carcinoma and cholangiocarcinoma

BACKGROUND/AIMS

Gastrin is a trophic factor within the normal gastrointestinal tract and is also a mitogen for a number of gastrointestinal and non-gastrointestinal tumours. Precursor forms of gastrin including progastrin (proG) and glycine-extended gastrin (G-gly) as well as the fully processed amidated gastrin (G-NH2) are expressed by tumours. There has been little study of the role of gastrin in either normal liver or liver tumours. The aim of this study was to identify the expression of CCK-B/gastrin receptor (CCK-BR), proG, G-gly and G-NH2 in normal liver and liver tumours.

METHODS

Tissue sections from patients with hepatocellular carcinoma, fibrolamellar carcinoma, cholangiocarcinoma as well as normal liver biopsies were assessed for expression of CCK-BR and gastrin isoforms.

RESULTS

Most liver tumours express CCK-BR and are able to process gastrin as far as proG and G-gly, although not as far as the amidated form. There appears to be little expression of the receptor and no expression of precursor forms of gastrin in normal liver.

CONCLUSIONS

Liver tumours express the CCK-BR and precursor forms of gastrin. This expression may be associated with tumour proliferation.

Mutations in FIE, a WD polycomb group gene, allow endosperm development without fertilization

A fundamental problem in biology is to understand how fertilization initiates reproductive development. Higher plant reproduction is unique because two fertilization events are required for sexual reproduction. First, a sperm must fuse with the egg to form an embryo. A second sperm must then fuse with the adjacent central cell nucleus that replicates to form an endosperm, which is the support tissue required for embryo and/or seedling development. Here, we report cloning of the Arabidopsis FERTILIZATION-INDEPENDENT ENDOSPERM (FIE) gene. The FIE protein is a homolog of the WD motif-containing Polycomb proteins from Drosophila and mammals. These proteins function as repressors of homeotic genes. A female gametophyte with a loss-of-function allele of fie undergoes replication of the central cell nucleus and initiates endosperm development without fertilization. These results suggest that the FIE Polycomb protein functions to suppress a critical aspect of early plant reproduction, namely, endosperm development, until fertilization occurs.

Expression of CCKB/gastrin receptor isoforms in gastro-intestinal tumour cells

Anti-serum raised against the human cholecystokinin B (CCKB)/gastrin receptor was used in Western blotting to differentiate the cellular locations of receptor isoforms expressed by human gastro-intestinal (GI) tumour cell lines. Using anti-serum directed against the amino-terminal extracellular tail of the CCKB/gastrin receptor, 8/9 cell lines were shown to express immunoreactive proteins of either m.w. 70 or 40 kDa, or both. Both isoforms were found to be associated with intracellular, non-nuclear membranes, whereas only the 70 kDa protein was expressed in the plasma membrane. Receptor expression was related to gastrin production and secretion. Both progastrin and glycine-extended gastrin-17 were produced and secreted by the tumour cell lines; however, carboxy amidated gastrin was not detected by radioimmunoassay. A CCKB/gastrin receptor transfectant NIH3T3 cell line did not produce detectable gastrin and showed exclusive expression of the 70 kDa receptor on the plasma membrane. One cell line had <50 pg/ml cell-associated progastrin and no detectable receptor form. Cell lines expressing 50-150 pg/ml had both 40 and 70 kDa receptor forms. Those expressing >150 pg/ml progastrin had only the 40 kDa isoform, which was shown to be exclusively expressed on intracellular, non-nuclear membranes, in one of the cell lines. Of the 4 cell lines exclusively expressing the lower m.w. receptor, 3 had gastrin present within the cell, which was not secreted. Thus, if cell-associated gastrin induces a proliferative effect, it may be by an intracrine pathway. Our study has identified the presence of CCKB/gastrin receptor isoforms in different cellular locations and may help toward understanding the complex autocrine and intracrine pathways mediated by gastrin peptides.

Coexpression of gastrin and gastrin receptors (CCK-B and delta CCK-B) in gastrointestinal tumour cell lines

BACKGROUND

The peptide hormone gastrin is a recognised growth factor for gastrointestinal (GI) tumour cells. Carboxyamidated gastrins bind to the cell surface gastrin/cholecystokinin B (CCK-B) receptor which can be expressed as either a normal or a truncated isoform (delta CCK-B).

AIMS

To compare gastrin gene expression with delta CCK-B and total CCK-B (both isoforms) gene expression in both GI and non-GI tract derived human tumour cell lines.

METHODS

Total RNA was extracted and gene expression was assayed by the reverse transcription-polymerase chain reaction followed by Southern blotting and hybridisation with specific oligo probes.

RESULTS

Gastrin was expressed by 5/5 gastric and 7/8 colorectal cell lines. Coexpression of gastrin CCK-B isoform was found in 80% of gastric and 75% of colorectal cell lines. Non-GI cell lines, with the exception of a lymphoblastic leukaemia cell line, showed no coexpression. The truncated receptor, delta CCK-B, was shown in 3/5 gastric and 5/8 colorectal cell lines and was always coexpressed with gastrin.

CONCLUSIONS

The truncated gastrin receptor, delta CCK-B, is coexpressed with gastrin in 8/13 GI tumour cell lines. Gastrin and CCK-B receptor isoforms may be involved in maintaining autocrine/paracrine growth pathways in GI cancer cells.

Gastrimmune raises antibodies that neutralize amidated and glycine-extended gastrin-17 and inhibit the growth of colon cancer

The effect of gastrin neutralization was evaluated on the in vivo growth of the rat colon line, DHDK12, which expressed cholecystokinin B/gastrin receptors and secreted glycine-extended gastrin-17 (G17). Gastrin neutralization was achieved by administration of the immunogen, Gastrimmune, which is composed of the amino terminal portion of G17 linked to a diphtheria toxoid. A rat-specific version of Gastrimmune was used to preimmunize rats, with control animals receiving diphtheria toxoid only. The antibodies raised neutralized both carboxy-amidated and glycine-extended G17. The tumor was implanted into the muscle layer of the abdominal wall, and rats immunized with Gastrimmune had significantly reduced median cross-sectional tumor areas (70.2% reduction; P = 0.005) and weights (56.5% reduction; P = 0.0078)) when compared to control rats. Histological analysis revealed that the tumors had an enhanced degree of necrosis, with the area of viable tumor in the Gastrimmune-immunized rat reduced to 40.3% compared to 58.6% in the control rats (P = 0.003). Immunization with Gastrimmune raised antibodies that inhibited the growth of a rat colon tumor. This could have been mediated by neutralization of both serum G17 and cell-associated precursor gastrin molecules.

Israel's National Health Insurance Law: expectations and concerns

An historical overview of the Israeli health care system is followed by detailed discussion of recent reforms mandated by the government to control rising yearly expenditures. The author examines the advantages and disadvantages of the reforms, concluding that they are only a first step toward long-term success.