Biomedical subjects

M W Burk

Publications and source records attributed to M W Burk.

At least 19 recordsLinked to original sources

PubMed1994

In situ detection of PCR-amplified HIV-1 nucleic acids in lymph nodes and peripheral blood in patients with asymptomatic HIV-1 infection and advanced-stage AIDS.

This study determined the in situ detection rate of polymerase chain reaction (PCR)-amplified human immunodeficiency virus type 1 (HIV-1) DNA and RNA in lymph nodes and peripheral blood CD4+ cells in six patients with asymptomatic HIV-1 infection and from six people who died of advanced AIDS. The lymph nodes of patients with asymptomatic infection showed expanded germinal centers where, on average, 20% of the CD21+ dendritic cells contained HIV-1 DNA. From 5 to 80% of the CD4+ cells in these lymph nodes contained HIV-1 DNA, as compared with 1-11% of the CD4+ peripheral blood mononuclear cells. The infection in most cells was latent in the asymptomatic group. In contrast, the lymph nodes of patients with advanced AIDS showed marked depletion of both dendritic and CD4+ cells. The majority of the remaining CD4+ cells in the lymph nodes and blood showed PCR-amplified viral DNA and cDNA sequences suggesting the presence of genomic and multiple spliced transcripts. It is concluded that asymptomatic HIV-1 infection is associated with a wide range of latent to active viral-positive CD4+ lymphocytes and dendritic cells in the lymph nodes. Progression to AIDS is characterized by active viral replication in many of the remaining CD4+ cells in the lymph nodes and blood.

Acquired Immunodeficiency Syndrome↗

PubMed1986

Monoclonal antibody-ricin A chain conjugates (immunotoxins): potential therapeutic agents for human colon carcinoma.

With the advent of hybridoma technology, monoclonal antibodies (MAbs) can be produced against specific human tumor cell-surface antigens. 44X14, an MAb produced in our laboratory by the immunization of BALB/c mice with colon carcinoma cells, exhibits high affinity for breast, lung, and colon carcinomas. However, this MAb shows little evidence of in vitro cytotoxicity. To enhance the potency of this MAb, it was coupled to the A chain (RTA) of the castor-bean protein ricin. Ricin is composed of two subunits--RTA, which binds to ribosomes and inhibits protein synthesis, and the B chain (RTB), which binds to galactose residues on all human cells and facilitates entry of RTA into the cell. By chemically separating RTA from RTB, RTA can then be coupled to MAb 44X14 so as to redefine its specific toxicity. This immunotoxin 44X14-RTA was assayed for protein-synthesis inhibition in HT-29 colon carcinoma and HT-1080 sarcoma cells by [3H]leucine uptake. Intact ricin (RTA + RTB) inhibited protein synthesis by 50% at concentrations of 0.76 and 4.8 ng/ml in HT-29 and HT-1080 cells, respectively. MAb 44X14 showed the same level of inhibition on HT-29 cells at 6.4 micrograms/ml, whereas the immunotoxin MAb 44X14-RTA showed 50% inhibition at 0.15 micrograms/ml. No effect of either MAb 44X14 or MAb 44X14-RTA at concentrations up to 200 micrograms/ml was seen on HT-1080 cells. Thus, the coupling of RTA to carcinoma-specific MAb 44X14 increased its potency 50-fold without increasing its nonspecific binding to cells that do not contain the appropriate antigen.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1984

Imaging of human tumor xenografts in nude mice with radiolabeled monoclonal antibodies. Limitations of specificity due to nonspecific uptake of antibody.

To determine if in vivo binding specificities of monoclonal antibodies to tumor nodules would reflect in vitro antibody specificities as determined by radioimmunoassay, two monoclonal antibodies were selected for imaging of human tumor xenografts in nude mice. By in vitro radioimmunoassay, antibody 436 binds to the M20 melanoma cell line, but not to the P3 carcinoma cell line; antibody 44 binds to P3 but not to M20. Both antibodies are IgG1 isotypes. Nude mice bearing an M20 melanoma in one flank and a P3 carcinoma in the other were injected intravenously with 5 to 25 micrograms of each antibody labeled with either I-125 or I-131; in separate animals the labels were reversed. Animals were imaged daily with a scintillation camera equipped with a pinhole collimator. On day 6 the animals were sacrificed, and binding of the antibodies to the tumors and normal tissue were compared. Antibody 436 had up to a two-fold binding advantage in vivo for the melanoma, whereas antibody 44 had up to a two-fold binding advantage for the carcinoma, thus confirming the in vitro specificities of each. However, imaging on day 4 and computer analysis of percent radioactivity in the tumors showed that tumor images were related directly to tumor size and relatively uninfluenced by antibody specificity. Thus, even though antibody specificity can be demonstrated by differential tissue counting, imaging of tumor deposits appears to involve a nonspecific phenomenon that is largely dependent upon tumor weight.

Animals↗

PubMed1984

Monoclonal hybridoma antibodies in human melanoma: current status.

The advent of hybridoma monoclonal antibody technology has opened a new frontier in the biomedical sciences. Human tumor biology and immunology are fields that should particularly benefit from its application. Many advances already have been made in the definition of human melanoma-associated antigens. Most work has been done using mouse monoclonal antibodies, but it now appears that the production of human monoclonal antibodies against human tumor antigens is an achievable goal. Mouse and human monoclonal antibodies should provide us with the reagents to catalogue and characterize both biochemically and functionally the entire range of molecules associated with human melanoma cells. These same reagents will be essential to the development of immunodiagnostic and immunoprognostic assays, and also may be used in the future as highly specific probes for the delivery of radioisotopes, chemotherapeutic agents, and toxins to metastatic tumor deposits.

Animals↗

PubMed1984

Human leukocyte (alpha) interferon in metastatic malignant melanoma: the American Cancer Society phase II trial.

Forty-four evaluable patients with metastatic malignant melanoma confined to the skin, subcutaneous tissues, lymph nodes, and/or lung were randomly assigned to receive either 1 X 10(6), 3 X 10(6), or 9 X 10(6) units of partially purified human leukocyte (alpha) interferon by daily im injection for 42 days. One patient achieved a partial response, two had minor responses, and three others had mixed responses. The only partial response was observed at the lowest dose of interferon. Toxicity increased in frequency and intensity with increasing interferon dose. This preparation of interferon at the doses, route, and schedule used appears to have little efficacy in metastatic malignant melanoma.

Adolescent↗

PubMed1983

Definition of human melanoma-associated cell surface antigens by hybridoma monoclonal antibodies.

Many human melanoma cell lines express HLA-D antigens in addition to HLA-A, -B, and -C specificities. Hybridoma antibodies produced after sensitization with melanoma cells are directed not only against tumor-associated antigens but against HLA and Ia-like specificities. Paired human melanoma cell lines and autologous lymphoblast lines were used to identify those monoclonal hybridoma antibodies that define human melanoma-associated antigens. Autologous lymphoblast lines were used to exclude hybridoma antibodies directed against HLA and Ia-like specificities. Using this method, we have identified several cell surface antigens that are expressed on the majority of human melanoma cell lines tested.

Animals↗

PubMed1982

Cloning of human solid tumors in soft agar.

Of 1,014 human solid tumors of various histologic types, 690 (68%) showed evidence of colony formation within 2 to 4 weeks. Tumors which grew particularly well were colon carcinoma (104/175), melanoma (134/155), lung carcinoma (62/85), breast cancer (100/140), ovarian carcinoma (50/67), and sarcoma (72/122). Histologic examination indicated that the colony-forming cells retained functional and morphologic features similar to those of the original tumor. Plating efficiencies varied between 0.01% and 0.2%, and the numbers of colonies observed formed a direct linear correlation with the number of cells plated. Recovery of viable tumor cells was increased when enzymatic tumor dissociation was used rather than a mechanical method. A simplified, supplemented medium resulted in improved cloning efficiencies when compared to previously reported methods (Hamburger and Salmon, 1977 b).

Clone Cells↗

PubMed1982

Clinical correlations with drug sensitivities in the clonogenic assay: a retrospective study.

We tested the ability of the in vitro clonogenic assay (CLAS) to predict clinical response for patients with solid tumors. Patients had objectively measurable disease and received at least one course of chemotherapy. The correlation between clinical responses and in vitro sensitivity was evaluated retrospectively. Tumor types included melanoma (19), sarcoma (five), hepatoma (one), and carcinoma of the stomach (two), colon (three), lung (one), and breast (one). Five patients received two separate courses of chemotherapy with different drugs or drug regimens. In nine of 11 (82%) instances, tumors were sensitive to a particular drug, and the patient had at least 50% regression of tumor following treatment with the tested drug. Two patients whose tumors were sensitive in vitro had no evidence of clinical response. In 25 of 26 assays, the CLAS accurately predicted tumor resistance, and only one patient had evidence of clinical response (96%). Associations of in vitro results with clinical responses were highly significant. The CLAS can accurately predict the chemosensitivity of a variety of solid tumors.

Antineoplastic Agents↗

PubMed1982

Monoclonal antibodies to 125 kd and 95 kd proteins on human melanoma cells: comparison with other monoclonal-defined melanoma antigens.

Two monoclonal antibodies produced by hybridomas were identified by an indirect 125I-protein A binding assay that define cell surface antigens expressed on cultured human melanoma cells but not on autologous lymphoblastoid cells. The first antibody, 705F6 (an IgG2b immunoglobulin), bound to 14/14 melanoma lines, 6/9 carcinomas and sarcomas, 7/7 gliomas and neuroblastomas, 2/2 fetal cell lines, 0/8 lymphoblastoid cell lines, and weakly to 2/4 leukemia lines. The second monoclonal antibody, 436G10 (IgG1), reacted with 10/14 melanomas 5/13 carcinomas and sarcomas, 2/7 gliomas and neuroblastomas, and weakly with the fetal cells, but not with the leukemic or lymphoblastoid cell lines. Comparison of 705F6 and 436G10 with 28 other monoclonal antibodies from different laboratories identified several with similar binding patterns to a panel of tumor and nontumor cell lines. Crossblocking of 125I-labeled 436G10 was not observed by R23, I12 or L10 antibodies. However, 705F6 was completely blocked by monoclonal 376.96S, showing that these two antibodies bind to the same antigenic determinant. The 705F6 antibody immunoprecipitated a 95 kd (kilodalton) membrane protein and the 436G10 antibody bound a 125 kd protein from 125I-labeled melanoma cells. The broad distribution of these two proteins on melanomas and other solid tumors suggests that they define common oncodevelopmental antigens expressed on proliferating cells.

Animals↗

PubMed1982

Systemic administration of human leukocyte interferon to melanoma patients. I. Effects on natural killer function and cell population.

Natural killer (NK) cytotoxicity was assessed against K562 targets in 14 melanoma patients who received daily im doses of human leukocyte interferon (IFN) for 42 consecutive days. The most common pattern of NK activity was a decline from pretreatment levels 1 day after initiation of treatment, followed by increasing cytotoxicity with peak activity at day 7 and a subsequent gradual decline to pretreatment levels during the remaining weeks of treatment. This pattern was particularly apparent in patients who received 3 x 10(6) or 9 x 10(6) U IFN/day, while patients who received 1 X 10(6) U IFN/day tended to lack the decline at day 1 and maintained the elevated NK activity past day 7. Changes in NK activity could not be related to changes in absolute lymphocyte counts; to proportions of cells bearing membrane receptors for erythrocyte-antibody-complement, of cells bearing FC gamma receptor; or to clinical response to IFN.

Cytotoxicity, Immunologic↗

PubMed1982

Monoclonal antibody against A1 Lewis d antigen produced by the hybridoma immunized with a pulmonary carcinoma.

A monoclonal antibody (CALed) against a human pulmonary squamous cell carcinoma line was cytotoxic to the line but did not react to an autologous B-lymphoblastoid line. Although the antibody was thought to be cancer specific, principally on the basis of this evidence, the antibody actually had the A1 Lewis d (Led) specificity. It reacted with approximately 2% of the random donor T-lymphocytes and with all six lymphocytes from donors who were A1 Led type without reacting to lymphocytes of any other type. The monoclonal antibody reactivity was also absorbed out by A1 Led red blood cells but not by red cells of other types. We conclude that the A1 Led antigen had been synthesized by the pulmonary carcinoma lines but not by the autologous lymphoblastoid line, resulting in disparity for this antigen. Since the combination A1 Led only occurs in 2% of the population, it is difficult to distinguish this type of antibody from tumor-specific antibodies.

Antibodies, Monoclonal↗

PubMed1981