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Biomedical subjects

M Sela

Publications and source records attributed to M Sela.

At least 19 recordsLinked to original sources
PubMed1992

Tumor-inhibitory monoclonal antibodies to the HER-2/Neu receptor induce differentiation of human breast cancer cells.

The HER-2/neu protooncogene (also called erbB-2) encodes a tyrosine kinase receptor for a polypeptide growth-regulatory molecule. Amplification and overexpression of the gene have been frequently observed in human adenocarcinomas and correlated with poor prognosis. To explore the potential of antibody therapy directed at the HER-2/Neu receptor, we have raised a panel of murine monoclonal antibodies to the human protein, and tested their effect on the tumorigenic growth of HER-2/neu-transfected fibroblasts in athymic mice. We previously reported that the i.p. injected antibodies either inhibited or accelerated the tumorigenic growth of HER-2/neu transfectants in athymic mice. Here we report that these opposing effects were induced also by i.v. injected antibodies, they lasted over 7 weeks, and were probably mediated by distinct epitopes on the receptor molecule. To understand the cellular mechanisms underlying antibody-induced tumor inhibition, we tested the effect of the monoclonal antibodies on various cultured human breast cancer cells. Our analysis revealed that the tumor-inhibitory antibodies specifically induced phenotypic cellular differentiation that included growth arrest at late S or early G2 phase of the cell cycle, markedly altered cytoplasm and nuclear morphology, synthesis and secretion of milk components (casein and lipids), and translocation of the HER-2/Neu protein to cytoplasmic and perinuclear sites. The extent of cellular differentiation by various antibodies could be correlated with their tumor-inhibitory potential, whereas a tumor-stimulatory monoclonal antibody or control immunoglobulin were completely inactive with respect to cellular differentiation. Taken together, our in vivo and in vitro studies correlate the tumor inhibitory potential of monoclonal antibodies to HER-2/Neu with their capacity to induce cellular differentiation in vitro. This observation may hold promise for immunotherapy of cancers that express the HER-2/neu oncogene.

Animals↗
PubMed1992

[A decade of experience in craniofacial surgery].

Our craniofacial surgery team includes experts from the following fields: plastic surgery, neurosurgery, ophthalmology, genetics, neurology, orthodontics, pedodontics, facial rehabilitation, psychiatry, social work, anesthesiology and intensive care. Craniofacial surgery became to a large extent pediatric surgery, following evidence that careful, early surgery does not impair growth and that development following surgery is almost normal. The malformations that were repaired included those of the Crouzon and Apert syndromes, requiring frontal remodelling and advancement of the middle third of the facial skeleton; hypertelorism in which orbits were moved to the midline; large craniofacial clefts in which the hemiface from either side was moved to the midline; and different types of craniostenosis in which frontal advancement and remodelling with reconstruction of the vault was performed. The series consisted of 78 patients who presented between 1979-1989. 3 illustrative cases are described.

Craniofacial Dysostosis↗
PubMed1992

Synthetic copolymer 1 inhibits human T-cell lines specific for myelin basic protein.

Copolymer 1 (Cop 1) is a synthetic basic random copolymer of amino acids that has been shown to be effective in suppression of experimental allergic encephalomyelitis and has been proposed as a candidate drug for multiple sclerosis. Cop 1 is immunologically cross reactive with myelin basic protein (BP) and was shown to inhibit murine BP-specific T-cell lines of various H-2 restrictions. In the present study these findings were extended to include human T-cell lines. Cop 1 competitively inhibited the proliferative responses and interleukin 2 secretion of six BP-specific T-cell lines and 13 clones with several DR restrictions and epitope specificities. Conversely, BP inhibited--albeit to a lesser extent--the response of all the Cop 1-specific T-cell lines and clones, irrespective of their DR restrictions. Another random copolymer of tyrosine, glutamic acid, and alanine, denoted TGA, had no effect on these lines. Neither Cop 1 nor BP inhibited the response of lines and clones specific for purified protein derivative. Cop 1 and BP exerted their cross-inhibitory effects only in the presence of antigen-presenting cells. These results suggest that Cop 1 can compete with BP for the binding to human major histocompatibility complex molecules. In view of recent studies implicating BP reactivity in multiple sclerosis, these findings suggest a possible mechanism for the beneficial effect of Cop 1 in this disease.

Antigen-Presenting Cells↗
PubMed1992

Immunotargeting of daunomycin to localized and metastatic human colon adenocarcinoma in athymic mice.

A monoclonal antibody (designated SF25), which recognizes a protein antigen expressed on a large number of human colon carcinomas, was used for drug targeting. Daunomycin-antibody conjugates were prepared by two previously described procedures. In one, the drug was bound to the antibody through a spacer of small molecular mass (cis-aconitic acid), while in the other a dextran bridge served as the link between drug and antibody. High substitution rates of drug to antibody were obtained using the latter binding procedure. Both conjugates were tested in vitro against two human colon carcinoma cell lines, LS180 and KM-12. The efficacy of a daunomycin-dextran-SF25 antibody conjugate was tested against colon carcinoma LS180 tumors transplanted at different sites into athymic mice. The specific conjugate was significantly more inhibitory to a subcutaneous tumor growth than its components or their mixture. SF25 antibody alone showed antitumoral effects against all three forms of transplanted tumor tested, namely, local, metastatic or intrahepatic, whereas daunomycin, on its own, was effective only against the subcutaneous tumor. Binding of daunomycin to dextran partially improved its inhibitory activity against the metastatic tumor. The conjugate, daunomycin-dextran-SF25 antibody reduced the number of metastatic foci, increased the survival rate and delayed death. Yet against lymph node metastases it was not significantly better than a mixture of both constituents. However, results obtained with an intrahepatic tumor, a model that mimics the natural progression of the disease, resembled those described with the subcutaneous tumor. Daunomycin-dextran-SF25 antibody was significantly more effective than all components separately and than a mixture of drug and antibody, provided a highly drug-substituted conjugate was used.

Adenocarcinoma↗
PubMed1992

Structural origin of the immunological diversity of two closely related tetrapeptides: CIDNP study of TyrTyrGluGlu and TyrGluTyrGlu epitopes.

Photochemically induced dynamic nuclear polarization (photoCIDNP) measurements, specific for exposed tyrosine residues, have been applied to elucidate conformational differences responsible for the immunological diversity of the synthetic multichain copolymers, Tyr1Tyr2Glu3Glu4-poly-DL-Ala-poly-Lys and Tyr1Glu2Tyr3Glu4-poly-DL-Ala-poly-LS. These two copolymers are essentially identical in their molecular weight, size, shape and composition, and differ only in the order of the two internal amino acid residues within the sequence of the tetrapeptide epitopes. Nonetheless, previous studies have shown that the two macromolecules behave differently, as evidenced by their immunological and immunogenic properties. As immunogens they act under different genetic control mechanisms, and differ in their interactions with antigen presenting cells, T cells and B cells. Antibodies elicited against these two antigens do not cross react. The photoCIDNP measurements of these two polymers, intended to elucidate discrete structural differences controlling immune recognition, showed that in the TyrTyrGluGlu polymer, Tyr1 and Tyr2 rings are free, non-interacting and undergo fast internal rotation. Computed minimum energy conformations confirm these conclusions and indicate that Tyr1 and Tyr2 point to different regions in space. In TyrGluTyrGlu, however, CIDNP measurements give rise to one broad tyrosine 3,5 proton signal, the result of a strong Tyr1-Tyr3 hydrophobic interaction. These two tyrosine residues are thus close in space, and undergo slow internal rotation. These results are in agreement with the computed minimum energy conformations.

Amino Acid Sequence↗
PubMed1992

Synthetic approaches to vaccines for infectious and autoimmune diseases.

The development is outlined of some synthetic vaccines against infectious diseases, in particular cholera, shigella and influenza. In the last case, use of the synthetic adjuvant MDP in combination with a haemagglutinin peptide has led to a synthetic vaccine with built-in adjuvanticity. The production of vaccines both by chemical synthesis and genetic engineering is described. The successful use of the synthetic amino acid copolymer COP-1 as an immunomodulatory vaccine to suppress the onset of allergic encephalomyelitis in experimental animals has led to clinical trials with patients suffering from exacerbating remitting multiple sclerosis. T-cell vaccination is an alternative approach to immunization against autoimmune diseases.

Adjuvants, Immunologic↗
PubMed1992

Signal transduction by the neu/erbB-2 receptor: a potential target for anti-tumor therapy.

The neu/erbB-2 protooncogene encodes a transmembrane tyrosine kinase homologous to receptors for polypeptide growth factors. The oncogenic potential of the presumed receptor is released through multiple genetic mechanisms including a point mutation, truncation of non-catalytic sequences and overexpression. The latter mechanism appears to be relevant to human cancers as elevated expression of the neu/erbB-2 gene is frequently observed in solid tumors of various adenocarcinomas. It is therefore conceivable that strategies aimed at the biochemical mechanism of action of the neu/erbB-2 tyrosine kinase may contribute to the treatment of certain human cancers. To this aim we undertook a multiple research approach consisting of the following directions: (i) The neu/erbB-2 ligand--a systematic screening of potential biological sources of the hypothetical hormone molecule, that presumably binds to the neu/erbB-2 protein, resulted in detection of a candidate activity in the medium of certain cultured transformed cells. Partial purification indicated that the factor is a 30-35 kDa glycoprotein. Further studies revealed several biochemical characteristics of the factor that may be helpful for complete purification and structural analysis of this novel hormone. (ii) Signal transduction by neu/erbB-2--using a chimeric receptor approach and various mutants we found that all the oncogenic forms of the neu/erbB-2 are constitutively coupled, both physically and functionally, to a multi-protein complex of signaling molecules. The latter includes the phosphatidylinositol-specific phospholipase C gamma and a phosphatidylinositol kinase. Thus, the metabolism of inositol lipids is probably a major biochemical pathway utilized by the neu/erbB-2 tyrosine kinase. (iii) Tumor inhibitory antibodies--we generated a panel of monoclonal antibodies to the presumed receptor. Surprisingly, some antibodies almost completely inhibited the growth of tumor cells in athymic mice, whereas one antibody significantly accelerated the rate of tumor growth in animals. Interestingly, the inhibitory antibodies conferred a mature phenotype to cultured breast cancer cells, implicating terminal differentiation in tumor retardation.

Amino Acid Sequence↗
PubMed1992

A tale of two peptides, TyrTyrGluGlu and TyrGluTyrGlu, and their diverse immune behaviour.

Studies on a synthetic multichain polypeptide antigen, (T,G)-A--L, prepared by polymerization techniques, led to a better understanding of the molecular basis of antigenicity, and of many other immunological phenomena, as well as to the discovery of determinant-specific genetic control of immune response. In view of the intensity of studies with this polymer, we were interested in elucidating its major B and T cell epitopes. We investigated two tetrapeptides, TyrTyrGluGlu and TyrGluTyrGlu. Both were attached to multichain branched poly(DLalanine). Even though the two resulting synthetic immunogens are essentially identical in their molecular weight, size, shape and composition, and differ chemically only in the sequence of the tetrapeptide epitopes, the immunological differences observed were profound. Antibodies in the two systems do not cross-react. The major B cell epitope of (T,G)-A--L is TyrTyrGluGlu, whereas the major T cell epitope is TyrGluTyrGlu. The two antigens are under different genetic controls, and differ in their uptake by macrophages. The TyrTyrGluGlu polymer is thymus-dependent, whereas the TyrGluTyrGlu polymer is thymus-independent. Investigation of the two tetrapeptides in their polymeric form, by photochemically induced dynamic nuclear magnetic polarization techniques, shows that they differ strongly in their intra-epitope aromatic interactions. Phenolic groups in TyrGluTyrGlu interact with each other, whereas they are far apart in TyrTyrGluGlu, as seen also in computer-derived models.

Amino Acid Sequence↗
PubMed1991

Cross-reactions and specificities of monoclonal antibodies against myelin basic protein and against the synthetic copolymer 1.

Antibody cross-reactivity is here demonstrated between basic protein (BP), the encephalitogenic molecule of myelin, and copolymer 1 (Cop 1), the synthetic amino acid copolymer, which has a suppressive effect on experimental allergic encephalomyelitis and is effective in reducing the number of relapses in exacerbating-remitting multiple sclerosis. This cross-reactivity is conclusively established using mouse monoclonal antibodies (mAbs). About a third of anti-rat BP mAbs and most of anti-mouse BP mAbs cross-reacted with Cop 1. This cross-reactivity could be demonstrated with anti-BP mAbs of different specificities. In addition, several anti-Cop 1 hybridomas cross-reacted with BP. This cross-reactivity was verified in several assay systems, including competitive inhibition experiments. Moreover, some anti-BP mAbs and anti-Cop 1 mAbs reacted in a heteroclitic manner and favored the cross-reactive antigen over the immunogen. In contrast to the mAbs, no cross-reactivity could be demonstrated with the antisera of immunized mice. This observation may reflect the different B-cell populations expressed in the mAb response as compared to the polyclonal response. Thus, the use of mAbs has uncovered specificities that are not evident in antisera and has revealed pronounced cross-reactivity between BP and Cop 1 at the B-cell level. These results further establish the immunological interrelationships between Cop 1 and BP, demonstrated earlier at the T-cell level.

Animals↗
PubMed1991

Direct binding of a synthetic multichain polypeptide to class II major histocompatibility complex molecules on antigen-presenting cells and stimulation of a specific T-cell line require processing of the polypeptide.

T-cell activation involves the recognition of foreign antigens as a complex with self-major histocompatibility complex (MHC) proteins on the surface of antigen-presenting cells (APC). Protein antigens usually require uptake by the APC and processing that results in the generation of peptide fragments. The branched synthetic polypeptide (Tyr, Glu)-Ala--Lys was chosen as a model antigen to follow the processing requirements, leading to T-cell activation. It has been demonstrated, by using fixed APC and various inhibitors of proteases, that (Tyr, Glu)-Ala--Lys has to be processed to stimulate a (Tyr, Glu)-Ala--Lys-specific T-cell line of C3H.SW (H-2b) origin to proliferate. To determine whether processing of (Tyr,Glu)-Ala--Lys is required to allow its association with the MHC class II molecules, biotin was covalently attached to it. Binding of the biotinylated (Tyr,Glu)-Ala--Lys to MHC class II gene products on the surface of intact normal APC was directly detected by phycoerythrin-streptavidin. The specificity of the binding was confirmed by its inhibition with anti-I-Ab antibodies as well as with excess of nonlabeled (Tyr,Glu)-Ala--Lys. Furthermore, introducing several inhibitors of proteases to the binding assay, we could substantiate that the proteolysis of (Tyr,Glu)-Ala--Lys is required to allow association of the resulting peptidyl T-cell epitopes with the MHC class II molecules themselves. The presence of the biotin moiety in the resulting peptides suggests that the T-cell epitopes of (Tyr,Glu)-Ala--Lys contain the N-terminal portion of the side chains of the branched polypeptide. An apparent Kd of 8.05 x 10(-8) M was determined, and optimal binding was detected after 10 hr of incubation with the antigen. The latter phenomenon is not due to slow uptake, since uptake of (Tyr,Glu)-Ala--Lys occurs mainly during the first 30 min of incubation, but rather reflects the events of processing that precede MHC interaction.

Animals↗
PubMed1991

Mechanistic aspects of the opposing effects of monoclonal antibodies to the ERBB2 receptor on tumor growth.

The ERBB2 (also called HER2, neu, and c-erbB-2) gene product, which encodes a growth factor receptor, was implicated in the malignancy of human adenocarcinomas. An antibody directed to the rat oncogenic receptor has been previously shown to have an antitumor effect in model systems. In an attempt to extend this observation to the protooncogenic human receptor and also to understand the underlying mechanism, we generated a panel of monoclonal antibodies specific to the extracellular portion of the ERBB2 protein. The effects of the antibodies on tumor growth were compared with their cellular and biochemical actions in vitro. Surprisingly, opposing in vivo effects were observed: although some antibodies almost completely inhibited the growth in athymic mice of transfected murine fibroblasts that overexpress Erbb-2, other antibodies either accelerated tumor growth or resulted in intermediate responses. When tested on cultured human breast carcinoma cells or ERBB2 transfectants, the tumor-stimulatory antibody was found to induce significant elevation of tyrosine phosphorylation of the ERBB2 protein. In contrast, only partial correlation was observed between the capacity to restrict tumor growth and the effects of the antibodies on receptor degradation and cellular proliferation in vitro. This suggests that the antitumor antibodies affect both receptor function and host-tumor interactions. Our results may help establish experimental criteria for the selection of specific antibodies for use either alone or in conjunction with other molecules as pharmacological antitumor agents.

Animals↗
PubMed1991

Indirect immunotargeting of cis-Pt to human epidermoid carcinoma KB using the avidin-biotin system.

Cis-diamminedichloroplatinum (II) (cis-Pt) complexed to a carboxymethyl dextran-avidin conjugate was targeted to biotin-monoclonal antibody 108 (b-MAb 108). This MAb recognizes the extracellular domain of the epidermal growth factor receptor (EGF-R) on human epidermoid carcinoma (KB) cells over-expressing EGF-R. Cis-Pt-carboxymethyl-dextran-avidin (Pt-dex-Av) containing 60-90 M cis-Pt/M avidin was administered 24 hr following b-MAb108 containing 3-5 M biotin/M MAb. This treatment was potentially more effective in suppressing the growth of established KB tumor xenografts, or in inhibiting the development of lung metastases in nude mice, than free MAb 108, free drug or MAb 108 followed by drug. Replacing b-MAb 108 by unbiotinylated antibody or by b-MAb of a different specificity also yielded lower suppressive effects. The sequential administration of Pt-dex-Av following b-MAb was more effective than introduction of the Pt-dex-Av when already complexed to b-MAb 108. The results presented in this preliminary investigation suggest that Pt-dex-Av is specifically removed from the circulation by b-MAb 108 concentrated at the tumor site.

Animals↗
PubMed1991

Short latency vestibular evoked response to angular acceleration impulse in human beings.

Vestibular evoked response (VsEP) to acceleration stimuli were recorded in experimental animals and in human beings by scalp electrodes. The stimuli are angular acceleration impulses (up to 30,000 deg/sec2) transmitted to the skull by special devices. The short latency vestibular evoked response consisted of several waves during the first 10 msec. The first two waves (P1 and P2), which are the most consistent, have been shown in cats to originate from the vestibular nerve and nucleus, respectively. The middle latency response is believed to be of myogenic origin. It is hoped that the recording of VsEP in human beings will enable the localization of the site of lesion in vertiginous patients.

Adolescent↗
PubMed1990

The effect of anti-alpha-fetoprotein-adriamycin conjugate on a human hepatoma.

Conjugates between chemotherapeutic agents and antibodies, linked by a dextran bridge, were previously shown to be effective in suppression of hepatoma growth in vitro and in vivo. However, scaling up of production of such conjugates may lead to a high degree of variation in molar ratios of drug to antibody in different batches. In this study, an alternative link between drug and antibody was evaluated. A conjugate between adriamycin and murine IgGI monoclonal antibodies to human alpha-fetoprotein was prepared using a polyglutamic-acid bridge. The simple and reproducible method of linking adriamycin to a specific site on the antibody enabled the binding of the drug to alpha-fetoprotein with a high yield (63% to 68%); the molar ratio of drug/antibody was in the range of 110:1 to 120:1. The conjugate retained its capacity to bind to purified alpha-fetoprotein. Incorporation of [3H]-thymidine or [3H]-leucine into hepatoma cells, which express alpha-fetoprotein, was inhibited by the conjugate, compared with unconjugated antibody. Furthermore, 90% of this pharmacological activity was preserved, compared with free adriamycin. In vitro, the inhibitory activity of the polyglutamic acid conjugate was higher than that of a conjugate in which dextran was used as the linker between drug and antibody. In vivo, both conjugates were equally effective in suppression of hepatoma growth transplanted subcutaneously in athymic mice. However, this effect lasted only during the treatment period of 2 to 3 wk. Six days after discontinuation of therapy, reacceleration of tumor growth was observed regardless of the conjugate used.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Vestibular evoked potentials with short and middle latencies recorded in humans.

Following success in recording short latency vestibular evoked potentials in experimental animals, we have succeeded in our attempts to record such potentials in human subjects. The stimuli were repetitive, short steps of high intensity angular acceleration (10,000 degrees/sec2) with short rise times which would synchronously activate many neurons of the vestibular pathway. Stringent control procedures ensured that the recorded activity was not an artefact. Short latency vestibular evoked potentials were recorded in 10 normal subjects with peak latencies of 3.5, 6.0 and 8.4 msec and amplitudes of 0.5 microV. Middle latency potentials were also recorded with latencies of 8.8, 18.8 and 26.8 msec and amplitudes of 15 microV. These responses were absent in a cadaver and in patients with bilateral dead labyrinths. In normal subjects, these vestibular evoked potentials were not affected by white noise. In conclusion, short and middle latency vestibular evoked potentials were recorded in normal human subjects.

Adolescent↗