Mutations in the glutathione-gated KefC K+ efflux system of Escherichia coli that cause constitutive activation

The kefC gene of Escherichia coli encodes a potassium efflux system that is gated by glutathione (GSH) and by GSH adducts. Independently isolated kefC mutations that result in spontaneous activation of the efflux system have been analyzed. Three mutations affect residues located adjacent to the conserved Rossman fold in the carboxyl-terminal domain. Two mutations lie in a sequence predicted to form a cytoplasmically located loop in the membrane domain of KefC. All of the mutants retain normal regulation by the YabF protein and by GSH adducts. A mutation in the Rossman fold, R416S, alters the normal regulation of KefC by GSH. In contrast to the wild-type protein, which is inactive in the presence of GSH, the R416S mutant is only active in the presence of GSH or its analogue, ophthalmic acid. Other mutations in this region or elsewhere in the protein have their spontaneous activity augmented by depletion of the GSH pool. These data identify a specific role for the carboxyl-terminal domain of KefC in regulating KefC activity and are discussed in the light of recent data that suggest that GSH adducts can bind within a Rossman fold.

The most frequently prescribed medications in the elderly and their impact on dental treatment

The high prevalence of multiple chronic medical conditions in the elderly and the likelihood of multiple drug therapies dramatically increase the chance of drug-specific adverse effects and drug-drug interactions. This article reviews the age-associated alterations in pharmacokinetics and pharmacodynamics along with the most frequently prescribed medications for the elderly. Adverse drug reactions, drug-drug interactions and oral side effects are reviewed along with the impact these medications may have on dental treatment planning and management.

Glutamate transport regulation of renal glutaminase flux in vivo

We proposed that glutamate transport into cultured kidney cells represses cellular glutaminase activity and hence regulates glutamine utilization. To test this putative regulatory mechanism in vivo, glutamine uptake and conversion to glutamate as well as ammonium production were measured in the intact functioning rat kidney. Glutamine uptake was determined as net removal, arteriovenous concentration difference times renal plasma flow, and also as unidirectional uptake from the fractional extraction of tracer L-[14C]glutamine. Ammonium production was measured as that released into the renal vein plus that excreted, and intracellular glutamine conversion to glutamate was assessed from the rise in cortical glutamate radiolabel specific activity. Cellular glutamate content was reduced 50-60% by infusing D-aspartate (a high-affinity glutamate transporter inhibitor) over 30 min, consistent with interdiction of glutamate uptake. This reduction in the glutaminase repressor was associated with a three- to fivefold increase in glutamine uptake and intracellular conversion to glutamate and ammonium. These results are consistent with and predictable from our previous in vitro model and point to an important role for this regulatory mechanism in the intact functioning organ.

Elevated expression of eIF4E and FGF-2 isoforms during vascularization of breast carcinomas

The translation initiation factor eIF4E is a novel protooncogene found over expressed in most breast carcinomas (Kerekatte et al., 1995), but the pathology where this elevation is initially manifested and its possible role in cancer progression are unknown. We report that eIF4E is markedly increased in vascularized malignant ductules of invasive carcinomas, whereas necrotic and avascular ductal carcinomas in situ display significantly lower levels. eIF4E facilitates the synthesis of FGF-2, a powerful tumor angiogenic factor. Conversely, reducing eIF4E with antisense RNA in MDA-435 cells suppresses their tumorigenic and angiogenic properties, consistent with loss of FGF-2 synthesis. These findings suggest a causal role for eIF4E in tumor vascularization.

Engineering antibodies for imaging and therapy

Several advances made during the past year will probably facilitate the development of therapeutic antibodies. Most notably, significant progress has been made in the rapid isolation of high affinity human antibodies from phage display libraries and by immunization of transgenic mice. The therapeutic potential of bispecific antibody fragments and Fc-containing proteins has been greatly enhanced by improved production methods. The utility of radiolabeled antibody fragments has been improved by the development of site-specific labeling methods and by the advent of the 'minibody', an engineered fragment that has proved to be highly successful for tumor imaging in mice.

Stable heterodimers from remodeling the domain interface of a homodimer using a phage display library

Structure-guided phage display was used to select for combinations of interface residues for antibody C(H)3 domains that promote the formation of stable heterodimers. A C(H)3 "knob" mutant was made by replacement of a small residue, threonine, with a larger one, tryptophan: T366W. A library of C(H)3 "hole" mutants was then created by randomizing residues 366, 368 and 407, which are in proximity to the knob on the partner C(H)3 domain. The C(H)3 knob mutant was fused to a peptide flag and the C(H)3 hole library was fused to M13 gene III. Phage displaying stable C(H)3 heterodimers were recovered by panning using an anti-flag antibody. Phage-selected C(H)3 heterodimers differed in sequence from the previously designed heterodimer T366W-Y407'A, and most clones tested were more stable to guanidine hydrochloride denaturation. The thermal stability of individual C(H)3 domains secreted from Escherichia coli was analyzed by differential scanning calorimetry. One heterodimer, T366W-T366'S:L368'A:Y407'V, had a t(m) of 69.4 degrees C, which is 4.0 deg.C higher than that for the designed heterodimer and 11.0 deg.C lower than that for the wild-type homodimer. The phage-selected C(H)3 mutant maintained the preference for forming heterodimers over homodimers as judged by near-quantitative formation of an antibody/immunoadhesin hybrid in a cotransfection assay. Phage optimization provides a complementary and more comprehensive strategy to rational design for engineering homodimers for heterodimerization.

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The provision of psychosexual services by genitourinary medicine physicians in the United Kingdom

A postal questionnaire survey, enquiring about the provision of psychosexual services, was sent to each GUM clinic in the UK. Of the 246 questionnaires distributed, replies were received from 166 directors responsible for 171 (69.5%) clinics. Of the 140 (84%) who supported the provision of a sexual dysfunction service, 59 (42%) currently provided such a service. Doctors and psychologists were the health care professionals most commonly involved in sexual dysfunction services for patients who were referred both internally and from external sources such as general practice and diabetic clinics. Patients with a variety of dysfunctions were being treated with a broad range of therapies, a reflection probably of the multidisciplinary nature of the team providing the service. However, it appears that junior doctors are not being trained in this field at present.

Prevalence of sexual dysfunction in heterosexual patients attending a central London genitourinary medicine clinic

Our objective was to determine the prevalence of sexual dysfunction among new heterosexual attendees at a central London genitourinary medicine (GUM) clinic. We carried out a cross-sectional study in which patients completed a self-administered questionnaire-the Golombok-Rust Inventory of Sexual Satisfaction (GRISS) and participated in a brief interview during which additional information was sought regarding the patient's sexual history. An overall transformed score of >5 on the GRISS was defined as indicative of overall sexual dysfunction and a score of >5 on any of the subscales as indicative of a specific sexual dysfunction. Twenty-five (24%) men and 10 (9%) women had a GRISS score in keeping with overall sexual dysfunction, the prevalence being significantly lower in women (P=0.01, chi2=6.56, 1df). Sixty-three men (59%) and 63 (60%) women produced scores indicative of significant abnormality on at least one subscale, including, in men: erectile dysfunction 20 (19%), premature ejaculation 23 (22%), and in women: vaginismus 26 (25%) and anorgasmia 23 (22%). Neither an abnormal overall or subscale score on the GRISS was associated with a current STD on KC60 diagnosis or a history of sexual assault for either men or women. There is a substantial prevalence of sexual dysfunction in new heterosexual attendees at our clinic, the service implications of which need to be addressed.

Remodeling domain interfaces to enhance heterodimer formation

An anti-p185HER2/anti-CD3 humanized bispecific diabody was previously constructed from two cross-over single-chain Fv in which YH and VL domains of the parent antibodies are present on different polypeptides. Here this diabody is used to evaluate domain interface engineering strategies for enhancing the formation of functional heterodimers over inactive homodimers. A disulfide-stabilized diabody was obtained by introducing two cysteine mutations, VL L46C and VH D101C, at the anti-p185HER2.VL/VH interface. The fraction of recovered diabody that was functional following expression in Escherichia coli was improved for the disulfide-stabilized compared to the parent diabody (> 96% versus 72%), whereas the overall yield was > 60-fold lower. Eleven "knob-into-hole" diabodies were designed by molecular modeling of sterically complementary mutations at the two VL/VH interfaces. Replacements at either interface are sufficient to improve the fraction of functional heterodimer, while maintaining overall recoverable yields and affinity for both antigens close to that of the parent diabody. For example, diabody variant v5 containing the mutations VL Y87A:F98M and VH V37F:L45W at the anti-p185HER2 VL/VH interface was recovered as 92% functional heterodimer while maintaining overall recovered yield within twofold of the parent diabody. The binding affinity of v5 for p185HER2 extracellular domain and T cells is eightfold weaker and twofold stronger than for the parent diabody, respectively. Domain interface remodeling based upon either sterically complementary mutations or interchain disulfide bonds can facilitate the production of a functional diabody heterodimer. This study expands the scope of domain interface engineering by demonstrating the enhanced assembly of proteins interacting via two domain interfaces.

Sterically stabilized anti-HER2 immunoliposomes: design and targeting to human breast cancer cells in vitro

Liposomes (70-100 nm) of 1-palmitoyl-2-oleoylphosphatidylcholine, cholesterol, and poly(ethylene glycol) (PEG)-modified phosphatidylethanolamine (PEG-DSPE) were conjugated to Fab' fragments of a humanized recombinant MAb against the extracellular domain of HER2/neu to create sterically stabilized immunoliposomes (anti-HER2 SL) as a drug carrier targeting HER2-overexpressing cancers. Conjugation employed maleimide-terminated membrane-anchored spacers of two kinds: a short spacer, providing attachment of Fab' close to the liposome bilayer, or a long spacer, with Fab' attachment at the distal terminus of the PEG chain. Confocal microscopy and spectrofluorometry of HER2-overexpressing breast cancer cells incubated with fluorescently labeled anti-HER2 SL prepared with either spacer showed binding of liposomes (8000-23000 vesicles/cell) followed by endocytosis (rate constant ke = 0.012-0.033 min-1) via the coated-pit pathway, evidenced by intracellular acidification and colocalization with transferrin. Uptake of anti-HER2 immunoliposomes by breast cancer cells with low HER2 expression, or after preincubation of cells with free anti-HER2 Fab', was less than 0.2% and 4.3%, respectively, of the uptake by HER2-overexpressing cells. Increasing PEG-DSPE content (up to 5.7 mol %) in anti-HER2-SL prepared with the short spacer decreased liposome-cell binding affinity 60-100-fold, while ke decreased only 2-fold; however, when Fab' fragments were conjugated via a PEG spacer, both binding affinity and ke were unaffected by PEG-DSPE content. Cell binding and internalization of anti-HER2 immunoliposomes increased at higher surface density of conjugated Fab' fragments, reaching plateaus at approximately 40 Fab'/liposome for binding and approximately 10-15 Fab'/liposome for internalization. Uptake of anti-HER2 immunoliposomes correlated with the cell surface density of HER2 and significantly (p < 0.005) correlated with the antiproliferative effect of the targeting antibody but not with the total level of cellular HER2 expression. The results obtained were used to optimize in vivo preclinical studies of anti-HER2 SL loaded with antineoplastic drugs.

'Knobs-into-holes' engineering of antibody CH3 domains for heavy chain heterodimerization

'Knobs-into-holes' was originally proposed by Crick in 1952 as a model for the packing of amino acid side chains between adjacent alpha-helices. 'Knobs-into-holes' is demonstrated here as a novel and effective design strategy for engineering antibody heavy chain homodimers for heterodimerization. In this approach a 'knob' variant was first obtained by replacement of a small amino acid with a larger one in the CH3 domain of a CD4-IgG immunoadhesin: T366Y. The knob was designed to insert into a 'hole' in the CH3 domain of a humanized anti-CD3 antibody created by judicious replacement of a large residue with a smaller one: Y407T. The anti-CD3/CD4-IgG hybrid represents up to 92% of the protein A purified protein pool following co-expression of these two different heavy chains together with the anti-CD3 light chain. In contrast, only up to 57% of the anti-CD3/CD4-IgG hybrid is recovered following co-expression in which heavy chains contained wild-type CH3 domains. Thus knobs-into-holes engineering facilitates the construction of an antibody/immunoadehsin hybrid and likely other Fc-containing bifunctional therapeutics including bispecific immunoadhesins and bispecific antibodies.

Overexpression of the proto-oncogene/translation factor 4E in breast-carcinoma cell lines

The expression of the proto-oncogene, translation factor elF-4E, was examined in breast-cell lines: 5 carcinomas and 2 normal. At the protein level, elF-4E was 10 times higher in the carcinoma lines than in normal cells, which is comparable to the level found in breast-cancer biopsies. The elevation appears to be due to increased transcription, since the elF-4E mRNA was correspondingly increased. These results demonstrate that cells isolated from naturally occurring breast carcinomas maintain an elevated expression of the factor. Turnover rates for elF-4E (mRNA and protein) were determined for normal and cancer cells. We found that elF-4e mRNA is relatively stable during an 8-hr incubation with Actinomycin D, but the half-life of the protein is fairly short (approximately 4.5 hr). This suggests that, in proliferating cells, elF-4E may be turning over rapidly, possibly to fine-tune the changes in translation rates which occur during the cell cycle.

Stereotactic breast biopsy is accurate, minimally invasive, and cost effective

BACKGROUND

We reviewed our experience with stereotactic core needle breast biopsy (SCNBB) for accuracy, complication rate, and staging profile of malignancies diagnosed.

METHODS

Since March 1993, 530 stereotactic biopsies were performed. Of these, 25 cases underwent stereotactic core needle biopsy with subsequent wire-guided biopsy.

RESULTS

In 25 patients with stereotactic and open biopsy, there was an accuracy for SCNBB of 96%. The number of biopsies rose from 100 to 250 biopsies annually, with an equivalent pre-test positive predictive value for mammography (17% to 19% historical versus 20% with SCNBB). The total number of de novo cancer diagnoses have increased from a mean of 57 to a mean of 71 annually. The percentage of tumors in situ, stage I or stage II, has increased from 60% to 69%.

CONCLUSIONS

Stereotactic core needle biopsy combines a high accuracy with a low complication rate. Its aggressive application for tissue diagnosis in suspicious nonpalpable mammographic lesions has increased the proportion of early (in situ and T1 or T2) tumors discovered, and increased the total number of breast cancers diagnosed.

Overexpression of the proto-oncogene/translation factor 4E in breast-carcinoma cell lines

The expression of the proto-oncogene, translation factor elF-4E, was examined in breast-cell lines: 5 carcinomas and 2 normal. At the protein level, elF-4E was 10 times higher in the carcinoma lines than in normal cells, which is comparable to the level found in breast-cancer biopsies. The elevation appears to be due to increased transcription, since the elF-4E mRNA was correspondingly increased. These results demonstrate that cells isolated from naturally occurring breast carcinomas maintain an elevated expression of the factor. Turnover rates for elF-4E (mRNA and protein) were determined for normal and cancer cells. We found that elF-4e mRNA is relatively stable during an 8-hr incubation with Actinomycin D, but the half-life of the protein is fairly short (approximately 4.5 hr). This suggests that, in proliferating cells, elF-4E may be turning over rapidly, possibly to fine-tune the changes in translation rates which occur during the cell cycle.

High level secretion of a humanized bispecific diabody from Escherichia coli

Clinical development of bispecific antibodies (BsAb) has been effectively stymied by the lack of efficient production methods. We therefore attempted to produce a humanized BsAb fragment using an expression system that has proved very successful for secretion of monospecific Ab fragments from E. coli. An anti-p185HER2/anti-CD3 BsF(ab')2 was first recast into the diabody format and then periplasmically secreted from E. coli grown to high cell density in a fermentor. The diabody was recovered in very high yield (up to 935 mg/l) after protein A purification and predominantly (> or = 80%) as a dimer as judged by size exclusion chromatography. Diabody dimers were found to be mainly functional heterodimers (approximately 75%) by titration with p185HER2 extracellular domain. The diabody binds p185HER2 extracellular domain and human T lymphocytes with affinities close to those of the parent BsF(ab')2. Furthermore, the diabody is capable of simultaneous binding to tumor cells overexpressing p185HER2 and CD3 on T cells as shown by cellular rosetting. The diabody is equally potent as the parent BsF(ab')2 in retargeting IL-2 activated T-enriched peripheral blood lymphocytes to lyse tumor cells overexpressing p185HER2.

Nursing staff back injuries: prevalence and cost in long term care facilities

This report describes the period prevalence and cost of back injuries to nursing staff of long term care facilities in comparison to nurses employed industry wide and to other occupations industry wide. The period prevalence of back injuries to nursing staff in long term care facilities was highest for nurse aides, followed by LPNs and then RNs. Nurses (combined) had a period prevalence of back injuries nearly 1.5 times higher than all employees of long term care facilities and 6 times higher than all occupations combined industry wide. Within long term care facilities, nurses sustaining back injuries were younger and had been employed for a shorter period of time than the average for all nurses employed in long term care facilities. Back injuries accounted for more than half of the indemnity and medical costs for all injuries incurred in nursing homes and industry wide. The findings highlight the need for better prevention and rehabilitation

Translational enhancement of FGF-2 by eIF-4 factors, and alternate utilization of CUG and AUG codons for translation initiation

The FGF-2 mRNA of most mammals contains a long and inhibitory 5' UTR in addition to at least two CUG codons upstream and in frame with the AUG start codon. These CUGs are used for translation initiation to generate several polypeptides. Cells overexpressing the translation initiation factor 4E produce and secrete large amounts of FGF-2, and particularly the largest, CUG1-initiated form. Overexpression of FGF-2 is due to a translational enhancement of its mRNA, as indicated by its association with large polyribosomes in contrast to control cells, where it partitions mostly in fractions lighter than 80 S or small polyribosomes. Breast carcinomas expressing elevated eIF-4E also exhibited the large FGF-2 isoforms, which could play an important role in tumor angiogenesis. Translation of in vitro transcribed rat FGF-2 in reticulocyte lysates resulted in synthesis of four polypeptides, of similar size to those observed in vivo. Addition of purified eIF-4F preferentially increased translation of CUG1- and AUG-initiated isoforms. Since the different isoforms of FGF-2 may have different roles and intracellular distribution, the effects of the eIF-4 factors on FGF-2 expression could be important for the control of cell proliferation and differentiation.

Engineering linear F(ab')2 fragments for efficient production in Escherichia coli and enhanced antiproliferative activity

We developed a novel bivalent antibody fragment, the linear (L-) F(ab')2, comprising tandem repeats of a heavy chain fragment VH-CH1-VH-CH1 cosecreted with a light chain. Functional humanized L-F(ab')2 directed against p185HER2 was secreted from Escherichia coli at high titer (> or = 100 mg/l) and purified to homogeneity. The L-F(ab')2 binds two equivalents of antigen with an apparent affinity (Kd = 0.46 nM) that is within 3-fold of the corresponding thioether-linked F(ab')2 fragment. The N-terminal site binds antigen with an affinity (Kd = 1.2 nM) that is approximately 4-fold greater than that for the C-terminal site, as shown by the comparison of L-F(ab')2 variants containing a single functional binding site. L-F(ab')2 has greater antiproliferative activity than the thioether-linked F(ab')2 against the p185HER2-overexpressing tumor cell line BT474. Linear and thioether-linked F(ab')2 have very similar pharmacokinetic properties in normal mice, and their serum permanence times are respectively 7- and 8-fold longer than the corresponding Fab fragment. L-F(ab')2 offers a facile route to bivalent antibody fragments that are potentially suitable for clinical applications, and that may have improved biological activity compared with thioether-linked F(ab')2 fragments.

Toward the production of bispecific antibody fragments for clinical applications

The clinical potential of bispecific antibodies (BsAb) has been hindered by the difficulty of obtaining clinical grade material, together with the immunogenicity of rodent-derived BsAb in patients. The supply issue is being directly addressed by recombinant methods for BsAb fragment production reviewed here. The immunogenicity issue will likely be overcome by the use of humanized or human antibodies. Currently, three technologies appear suitable for the production of BsAb fragments for clinical applications: BsF(ab')2 assembled from Fab' fragments expressed in Escherichia coli, BsF(ab')2 assembled using leucine zippers, and diabodies.