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Biomedical subjects

I Hellström

Publications and source records attributed to I Hellström.

At least 73 records · Page 4Linked to original sources
PubMed1992

Recent advances in antitumor vaccines.

Immunization with anti-idiotypic antibodies can induce cell-mediated and humoral antitumor immunity in animal models. This immunity can sometimes cause tumor destruction. However, more needs to be learned about how best to induce the type of immune response that is responsible for tumor destruction, since the presence of anti-idiotypic antibodies has been shown occasionally to enhance, rather than to inhibit, tumor growth. There is evidence suggesting that immunization of human cancer patients with Ab2 can have therapeutic benefit, and also that patients who mount a vigorous Ab2 response following treatment with an Ab1 may do clinically better than those who do not make any Ab2. Although the generation of Ab2 related to infused antitumor Ab1 does not cause tumor rejection in the majority of patients, and although the clinical data from patients given Ab2 are scarce, the suggestion that Ab2 may cause destruction of human cancers indicates that further work in this area may become rewarding.

Antibodies, Anti-Idiotypic↗
PubMed1991

The influence of periodate oxidation on monoclonal antibody avidity and immunoreactivity.

Eight monoclonal antibodies of different classes and isotypes and rabbit IgG were oxidized under a variety of conditions with 5-50 mM periodate. The number of aldehyde groups generated per immunoglobulin were measured by reduction with tritiated sodium borohydride or coupling of fluoresceinthiosemicarbazide. There were up to 25.5 aldehyde groups detected on the periodate-oxidized antibody 96.5, measured by borohydride reduction whereas the same conditions led to only 9.6 aldehydes per IgG on the antibody L6 of the same IgG2A isotype. Fluoresceinthiosemicarbazide bound to oxidized antibodies but not to the same extent as tritium. On mildly oxidized IgMs it was possible to generate more than 200 aldehyde groups per antibody molecule. Depending on the conditions and the antibody used periodate oxidation could lead to antibody crosslinking. The avidities of the modified antibodies were determined by Scatchard analyses and inhibition assays. A new mathematical method to evaluate the immunoreactivities of modified antibodies relative to the unlabeled native antibody from inhibition binding data was established. Periodate concentrations higher than 50 mM decreased the avidities and immunoreactivities of all IgGs tested. This effect is more pronounced if the oxidation is performed at pH 5.6 and 25 degrees C instead of pH 4.6 and 0 degree C. The BR96 antibody is inactivated even under mild oxidation conditions.

Animals↗
PubMed1991

CD4+ T cell clones specific for the human p97 melanoma-associated antigen can eradicate pulmonary metastases from a murine tumor expressing the p97 antigen.

p97 is a human tumor-associated Ag present on most melanoma cells that represents a possible target for immunologic attack. To evaluate the capacity of T cells reactive with this protein to promote elimination of melanoma cells expressing p97, a murine model was developed by transfecting a C3H/HeN melanoma with the p97 cDNA, generating p97-specific CD4+ T cells by in vivo immunization of C3H/HeN mice with a vaccinia/p97 recombinant virus followed by in vitro cloning with soluble p97 protein, and determining whether these CD4+ T cells could mediate rejection of pulmonary metastases. Characterization of the T cell clones demonstrated the presence of both I-Ak and I-Ek-restricted clones, although the majority of clones recognized p97 in the context of I-Ek. Analysis of clonal specificity using truncated p97 proteins revealed that at least three epitopes were immunogenic, and further studies with overlapping 15-amino acid peptides from a region of the p97 molecule defined by these truncated proteins identified an immunodominant epitope responsible for the majority of the I-Ek response. The T cell clones were not capable of directly recognizing the p97-expressing melanoma cells but responded to the tumor if syngeneic APC were present to process the tumor-derived p97 Ag. The therapeutic efficacy of these CD4+ T cell clones was evaluated in an adoptive therapy model in which mice bearing metastatic pulmonary lesions were treated by i.v. administration of the p97-specific cells. Despite the inability of the CD4+ clones to directly respond to or lyse the tumor cells, the clones were effective in promoting tumor eradication. In vitro studies demonstrated that this may have reflected secretion of lymphokines that activated macrophages to lyse the tumor. The results suggest that noncytolytic p97-specific CD4+ T cell clones can be effective in therapy of pulmonary melanoma metastases. Moreover, if human T cells reactive with the p97 protein could be generated, the expression of this tumor-associated Ag in melanoma cells might be adequate for such T cells to mediate a therapeutic antitumor response.

Animals↗
PubMed1991

Human papillomavirus type 16 nucleoprotein E7 is a tumor rejection antigen.

It has been speculated that immunological mechanisms play an important role in the control of carcinomas associated with human papillomavirus (HPV), such as cervical cancers. We have now demonstrated that immunization of C3H/HeN mice by syngeneic nontumorigenic fibroblast-like cells that contain the transfected HPV-16 E7 gene conferred protection against transplanted cells from a HPV-16 E7-positive syngeneic tumor. This protection was HPV-16 E7-specific and was mediated by CD8+ lymphocytes, which presumably were cytotoxic T lymphocytes. These results indicate that tumor cells containing HPV-16 E7, either as a result of transfection, as in our studies, or naturally, as occurs in many human carcinomas, can induce a tumor-specific rejection response and serve as targets for such a response. The system described here provides an animal model to further study immune responses to HPV-associated malignancies and to test the efficacy of anti-HPV vaccines toward the therapy and prevention of such tumors.

Animals↗
PubMed1990

Epitope mapping and use of anti-idiotypic antibodies to the L6 monoclonal anticarcinoma antibody.

Mouse monoclonal anti-idiotypic antibodies (anti-ids) were raised against L6, a murine IgG2a monoclonal antibody specific for a cell surface antigen expressed by many human carcinomas. Ten distinct anti-ids were generated. Eight anti-ids were shown to inhibit the binding of L6 to its target antigen and were characterized in detail. The heavy and light chain variable region gene segments of the monoclonal antibody L6 linked to human constant regions (chimeric L6) were expressed separately or together, to map the epitopes recognized by the anti-ids. Individual anti-ids were shown to recognize heavy chain, light chain, or combinatorial variable region determinants. Defining these specificities enabled us to select particular anti-ids for assays to monitor the pharmacokinetics of either murine or chimeric L6 antibodies in the circulation of human patients. A quantitative enzyme-linked immunosorbent assay developed with two anti-ids accurately detects less than 5 ng/ml. Anti-ids specific for light chain variable region-encoded determinants were capable of recognizing L6 antigen-binding fragments bound to the surface of human carcinoma cells. These anti-ids can be used to study the binding of chimeric L6 antibody at the surface of tumor cells in histological sections of tumor biopsies.

Animals↗
PubMed1990

Highly tumor-reactive, internalizing, mouse monoclonal antibodies to Le(y)-related cell surface antigens.

Two monoclonal antibodies, designated BR64 (IgG1) and BR96 (IgG3), were generated that, according to immunohistology, bind selectively to carcinomas of the colon, breast, ovary, and lung. They have no or very low reactivity with normal human tissues, except for the fact that BR64 strains capillaries in the hearts from certain normal donors and that both monoclonal antibodies stain some epithelial cells from the gastrointestinal system, including stomach. Preliminary studies indicate that at least a portion of the epitope recognized by BR64 and BR96 is a Le(y) carbohydrate chain. Both monoclonal antibodies can be "internalized" by antigen-positive tumor cells, since immunoconjugates with ricin A-chain are cytotoxic. BR96 has the additional properties of being cytotoxic by itself, and it can mediate antibody-dependent cellular cytotoxicity and complement dependent cytotoxicity.

Antibodies, Monoclonal↗
PubMed1990

Antibody-penicillin-V-amidase conjugates kill antigen-positive tumor cells when combined with doxorubicin phenoxyacetamide.

The two monoclonal antibodies (mAb), L6 (anti-carcinoma), and 1F5 [anti-(B-cell-lymphoma)], were chemically linked to the enzyme penicillin-V amidase (PVA), which hydrolyzes phenoxyacetamides, to explore the potential of using mAb-enzyme conjugates for the localization of chemotherapeutic drugs at tumor cells. The phenoxyacetamide derivatives of doxorubicin and melphalan were prepared, yielding the less toxic amides, doxorubicin-N-p-hydroxyphenoxyacetamide (DPO) and melphalan-N-p-hydroxyphenoxyacetamide (MelPO). These were hydrolyzed by PVA to doxorubicin and melphalan respectively. In vitro studies with the L6-positive lung carcinoma cell line, H2981, and the 1F5-positive B-cell lymphoma line, Daudi, showed that DPO was 80-fold less toxic to H2981 cells and 20-fold less toxic to Daudi cells than doxorubicin, and its toxicity was substantially increased when the H2981 cells were pretreated with L6-PVA or the Daudi cells were pretreated with 1F5-PVA. The cytotoxic effect was antigen-specific, since only the binding mAb-enzyme conjugate increased the cytotoxicity of the prodrug. MelPO was more than 1000-fold less toxic than melphalan to H2981 cells and more than 100-fold less toxic than melphalan to Daudi cells. Pretreatment with the mAb-PVA conjugates did not enhance the toxicity of MelPO in either cell line, because PVA hydrolyzes the phenoxyacetamide bond of MelPO too slowly to generate a toxic level of melphalan.

Amidohydrolases↗
PubMed1990

Expression of neurophysin-related precursor in cell membranes of a small-cell lung carcinoma.

A monoclonal antibody (mAb L6) to a small-cell lung carcinoma surface antigen recognizes a common epitope of vasopressin-neurophysin and oxytocin-neurophysin in hypothalamic nuclei. We now report on the identification of a neurophysin-like precursor in human lung carcinoma (LX-1) cell membrane. mAb L6 immunoaffinity chromatography of solubilized membranes resulted in a single band of approximately 45 kDa. Western blot analysis demonstrated immunoreactivity of this band with mAb L6, anti-vasopressin, and an antibody to the vasopressin precursor, pro-pressophysin. N-terminal sequencing of this band demonstrated a 21-amino acid homology with the N terminus of human pro-pressophysin, and substitution of a Cys33 residue in the tumor antigen with Arg33. Absence of immunoreactivity with the antibodies described above in cytosolic extracts and culture medium suggests nonsecretion of processed or intact pro-pressophysin-like peptide. Northern analysis of LX-1 mRNA with a 30-mer to the C terminus of rat pro-pressophysin resulted in a band of approximately 1000 base pairs, 250 base pairs larger than hypothalamic message. In situ hybridization of LX-1 tumor-bearing nude rat brain with the same probe demonstrated specific hybridization in rat hypothalamus and xenografted tumor. These findings suggest expression of a pro-pressophysin-like protein in this tumor cell line that is preferentially targeted to the cell membrane.

Amino Acid Sequence↗
PubMed1990

Identification of neurophysin immunoreactivity in hypothalamus by a monoclonal antibody to a carcinoma cell surface antigen.

Mouse monoclonal antibody (mAb) L6 identifies an antigen expressed on the cell surface of many different human carcinomas. While studying the binding activity of mAb L6 to intracerebral tumor xenografts of human lung carcinoma LX-1 cells in nude rats using immunohistological techniques, we observed that L6 can also bind to a cytoplasmic antigen expressed in the magnocellular component of the hypothalamo-neurohypophysial system. Double-labeling experiments with antisera to vasopressin and oxytocin confirmed the localization of L6 immunoreactivity within both peptide-containing cell groups. L6 immunoreactivity in Brattleboro rats (with genetic deletion in the vasopressin gene) was exclusively localized within oxytocin neurons. Oxytocin and vasopressin failed to block L6 staining which suggested that its target epitope resides within the neurophysin sequence, and this explanation was supported by the finding that adsorption of L6 with porcine neurophysin completely eliminated hypothalamic immunoreactivity. Western blot analysis of bovine neurophysin and human pituitary extracts identified L6-immunoreactive bands which corresponded to the position of neurophysin and pro-pressophysin, confirming that L6 immunoreactivity in hypothalamus is related to neurophysin. Thus, monoclonal antibody L6, which is highly reactive with a membrane antigen of human lung cancer cell line LX-1, recognizes a cytoplasmic epitope in hypothalamic neurons identified as neurophysin by immunohistochemistry and Western analysis.

Adsorption↗
PubMed1990

Phase I trial of murine monoclonal antibody L6 in breast, colon, ovarian, and lung cancer.

Murine monoclonal antibody (MAb) L6 binds to an antigen expressed on the surface of breast, colon, ovary, and nonsmall-cell lung cancer. This antibody effects antibody-dependent cellular cytotoxicity (ADCC) with human mononuclear cells and complement-dependent cytotoxicity (CDC) with human complement. Because of these activities, we conducted a phase I trial of MAb L6 in patients with advanced cancer. Nineteen patients whose tumors highly expressed antigen were selected for this trial. Eighteen were evaluable. MAb L6 was administered at dose levels ranging from 5 mg/m2/d to 400 mg/m2/d for 7 days and was well tolerated. The only side effects detected were fever and headaches at the highest dose levels. The serum half-life of L6 was directly related to dose and ranged from a mean of 7.7 hours at 5 mg/m2/d to 29.1 hours at 400 mg/m2/d. Peak serum concentrations ranged from 0.22 micrograms/mL to 362 micrograms/mL. Biopsies at the end of treatment showed L6 to localize well to tumor cells with apparent in vivo saturation occurring at dose levels above 100 mg/m2/d. Thirteen patients formed human antimouse antibodies (HAMA), some as early as day 13. One patient with recurrent breast cancer on the chest wall achieved a complete remission. The response was first noted at 5 weeks and a pathologic complete remission occurred at 14 weeks. Because of its favorable binding properties and the encouraging clinical effect observed, future evaluation of this MAb appears warranted.

Adult↗
PubMed1989

Enhancement of the in vitro and in vivo antitumor activities of phosphorylated mitomycin C and etoposide derivatives by monoclonal antibody-alkaline phosphatase conjugates.

Alkaline phosphatase (AP) was covalently linked to the two antitumor monoclonal antibodies, L6 (anticarcinoma) and 1F5 (anti-B lymphoma), forming conjugates that could bind to antigen-positive tumor cells. The conjugates were able to convert the prodrugs, mitomycin phosphate (MOP) and etoposide phosphate (EP), into an active mitomycin C derivative, mitomycin alcohol, and etoposide, respectively. MOP and EP were less toxic to cultured cells from the H2981 lung adenocarcinoma than their respective hydrolysis products, mitomycin alcohol and etoposide, by a factor greater than 100, and they were also less toxic in mice. Pretreatment of H2981 cells with L6-AP greatly enhanced the cytotoxic effects of MOP and EP, while 1F5-AP caused no such enhancement. A strong antitumor response was observed in H2981-bearing mice that were treated with L6-AP followed 24 h later by either MOP or a combination of MOP and EP. This response was superior to that of MOP or combinations of MOP and EP given alone.

Adenocarcinoma↗
PubMed1989

Monoclonal antiidiotypic antibodies related to the p97 human melanoma antigen.

We have made monoclonal antiidiotypic antibodies (Ab2) relating to the p97 antigen of human melanoma. This was accomplished by immunizing BALB/c mice with 96.5, a monoclonal antibody (MAb) specific for epitope p97a, hybridizing their spleen cells with NS-1 myeloma cells, and selecting for hybridomas making antibody binding to Fab fragments prepared from MAb 96.5 (Fab 96.5). The Ab2 were tested for binding to Fab 96.5, as well as for their ability to inhibit the binding between MAb 96.5 and p97. Three monoclonal Ab2 were identified which competitively inhibited the binding between p97 and MAb 96.5 when injected into either BALB/c or C3H/HeN mice; two of them induced Ab3 which expressed the same idiotype as MAb 96.5 and which were specific for p97. These two Ab2 thus appear to functionally mimic p97. They were, however, unable to induce delayed-type hypersensitivity to p97 and to protect mice against transplants of p97-positive mouse melanoma cells, suggesting that the epitope recognized by MAb 96.5 may not be a target for cell-mediated rejection of tumors.

Animals↗
PubMed1989

Cyclophosphamide potentiates the antitumor activity of v-p97NY.

Previous work has demonstrated that a recombinant live vaccinia virus-based tumor vaccine, v-p97NY, induces an immune response in mice which can lead to the rejection of transfected lines of mouse melanoma cells expressing the human melanoma antigen p97 (S.-L. Hu et al., J. Virol. 62, 176, 1988; C. D. Estin et al., Proc. Natl. Acad. Sci. USA 85, 1052, 1988). We now show that the ability of v-p97NY to induce delayed-type hypersensitivity to p97 improved if the vaccinated mice were given cyclophosphamide (Cy) on the day of vaccination. Likewise, treatment of vaccinated mice with Cy increased the antitumor activity of vaccination so that tumor colony formation in the lungs was inhibited even when v-p9NY plus Cy was not given until 7 days after intravenous injection of tumor cells.

Animals↗
PubMed1989

Transfected mouse melanoma lines that express various levels of human melanoma-associated antigen p97.

The gene for the human melanoma-associated antigen p97 has been introduced by cDNA transfection into cells from clone M2 of the K1735 mouse melanoma, which metastasizes to the lung when injected iv into syngeneic C3H/HeN mice. Tumor clones were established from the transfected cells and found to differ in the level of p97 expression. Their outgrowth in immunocompetent syngeneic mice was shown to inversely correlate with p97 antigen expression, and lines that express higher p97 levels elicited a stronger delayed-type hypersensitivity response when injected into the footpads of mice immune to p97. Five clones which expressed very high levels of p97 failed to grow in immunocompetent C3H/HeN mice while they formed tumors in nude (nu/nu) mice. The highest expressing clone, 2A, grew slightly faster than any of the other clones when cultured in vitro. Since several of the transfected clones were found to express a stable level of p97 and have consistent in vivo growth behavior, they provide a useful model for various forms of antigen-specific active and passive immunotherapy with the same agents as those intended for human application.

Animals↗
PubMed1989

Evaluation of L6, an anti-carcinoma murine monoclonal antibody, in tumor-bearing nude mice.

L6 is a murine monoclonal antibody (MAb) binding to cells of most human carcinomas, mediating antibody-dependent cellular cytotoxicity and complement-dependent cytotoxicity, and inhibiting tumor growth in nude mice [10]. Fab and F(ab')2 fragments of L6, as well as intact MAb, have been evaluated for immunospecific localization in nude mice xenografted with a human lung carcinoma. They were compared with preparations of an isotype-matched control immunoglobulin, P1.17, after labelling with 125I or 131I. L6 Fab fragments prepared from MAb L6 and labelled with 67Ga via desferrioxamine were also tested. The data suggest that MAb L6 may be useful for in vivo detection of human carcinomas.

Animals↗