Methods for production of monoclonal antibodies with specificity for human lung cancer cells

Detection by a human monoclonal antibody of a glycoprotein associated with malignant proliferation of mammary epithelial cells

A tumour-associated antigen (TAA.62) with an apparent mol. wt. of 62 kd, identified by a human monoclonal antibody (IgG2, kappa-light chain), was found to be expressed at elevated levels in the cytoplasmic compartment of malignant as compared with normal mammary epithelial cells in both tissues and cultured cells. Increased levels of cytoplasmic expression of the antigen were also observed in malignant cells of cervix, colon, kidney, lung, and stomach. The patterns of expression of TAA.62 in cultured cells mirrored those of tissues and the antigen was expressed at elevated levels in the established breast cancer lines or oncogenically transformed mammary carcinoma cell line (tumourigenic) compared with the immortalised mammary epithelial cell line (non-tumourigenic). Aliquots of TAA.62 were purified to homogeneity from the conditioned-medium of malignant and immortalised breast cells by immunoaffinity chromatography using immobilised anti-TAA.62 antibody, and gel filtration. Both preparations of TAA.62 yielded a single band with an apparent molecular weight of 62 kd under reducing condition on sodium dodecyl sulphate-polyacrylamide gel electrophoresis, and both were identical in terms of size and immunoreactivity to anti-TAA.62 antibody. However, TAA.62(T) isolated from tumourigenic cell lines itself interacted with a cell surface molecule having an apparent molecular weight of 160 kd on both the malignant and immortalised cells: TAA.62(I) isolated from immortalized cell lines, showed no comparable interaction. Scatchard analysis of the concentration-dependent binding of TAA.62(T) to 160 kd-receptor molecule revealed a 2.6 x 10(4) binding sites per cell. The association constant of such binding was determined to be approximately 16.6 nM. Finally, addition of anti-TAA.62 antibody to culture medium resulted in the inhibition of proliferation of the malignant cells, but showed no effect on the normal cells. The results suggest that TAA.62 may interact as a ligand with its 160 kd cell surface receptor with a possible growth related function.

In vitro chemical eradication of small cell lung cancer: application in autologous bone marrow transplantation

Autologous bone marrow transplantation raises the question of the possible reinjection of tumour cells together with marrow. This paper investigates the ability of chemical compounds other than cyclophosphamide derivatives to eradicate small cell lung cancer (SCLC) in bone marrow. The responsiveness of SCLC lines to cis-platinum, doxorubicin, VP16, Celiptium (an ellipticine derivative), Ditercalinium, a new drug belonging to the pyridocarbazole series, and Asta Z were measured in an agar-agar clonogenic assay. Cis-platinum and Ditercalinium exhibited a high tumouricidal effect. The low cloning efficiencies of SCLC lines in an agar-agar clonogenic assay did not allow tumour cells to be detected among bone marrow cells with sufficient sensitivity. Therefore cis-platinum and Ditercalinium were tested on bone marrow-tumour cell mixtures cultured in a liquid medium allowing the detection of one tumour cell per 10(4) bone marrow cells. As cis-platinum exhibited a low myelotoxicity, it is proposed for purging bone marrows of patients with SCLC.

Recent advances in the biology of small cell lung cancer

Advances in the techniques for culturing human tumors in vitro, especially lung cancer cells, have greatly facilitated studies of the biologic properties of both small cell and non-small cell lung cancer cells. Detailed analysis has been done of well-characterized cell lines of both groups with respect to growth properties, biomarker and antigen expression, cytogenetics, and oncogene amplification and expression. Two major conclusions have emerged from these studies: (1) considerable heterogeneity exists within a given tumor type (eg, SCLC) in the expression of a given biomarker, and (2) overlap in the expression of biomarkers exists between cells of SCLC and non-SCLC, suggesting a common stem cell for all types lung cancer. In the future, clinical trials the impact of the biologic properties of cells on responses to therapy and survival will need assessment.

Glycoconjugates in nervous tissue and small cell lung cancer share immunologically cross-reactive carbohydrate determinants

Small cell lung cancer (SCLC) is a bronchogenic carcinoma of neuroectodermal origin that expresses a variety of nervous system markers characteristic of neuroendocrine cells. In addition, SCLC cell lines and biopsies have been shown immunocytochemically to express an antigen recognized by HNK-1, a mouse monoclonal antibody which recognizes a surface antigen on natural killer cells and on the myelin-associated glycoprotein (MAG) and other nervous system glycoconjugates. Immunoblot data are presented which identify 2 groups of HNK-1-reactive plasma membrane glycoproteins with Mrs of about 80 000 and 130 000, respectively, from several SCLC cell lines. Using antibodies to MAG carbohydrate and protein determinants as probes, it is shown that the SCLC glycoproteins reacting with HNK-1 do not appear to share structural similarity with MAG apart from carbohydrate determinants. Using similar techniques with a panel of polyclonal antibodies, data are shown indicating that there is no cross-reactivity of SCLC proteins with other myelin proteins including P0, P1, P2, proteolipid protein and myelin basic protein. A possible role of the carbohydrate antigen in mediating nervous system disease associated with SCLC is suggested.

Bombesin-like peptides can function as autocrine growth factors in human small-cell lung cancer

The autocrine hypothesis proposes that a cell produces and secretes a hormone-like substance that can interact with specific membrane receptors on its surface to induce effects such as proliferation. Thus, a cancer cell could act to stimulate its own growth. Bombesin and bombesin-like peptides (BLPs) such as gastrin-releasing peptide (GRP) cause various physiological responses in mammals, including stimulation of proliferation of 3T3 mouse fibroblasts and normal human bronchial epithelial cells in vitro and induction of gastrin cell hyperplasia and increased pancreatic DNA content in vivo in rats. Human small-cell lung cancer (SCLC) cell lines produce and secrete BLPs and can express a single class of high-affinity receptors for BLPs. Exogenously added BLPs can also stimulate the clonal growth and DNA synthesis of SCLC in vitro. These findings suggest that BLPs function as autocrine growth factors for this tumour. One way to test this hypothesis is to interrupt the function of the endogenously produced BLPs. Here, we demonstrate that a monoclonal antibody to bombesin binds to the C-terminal region of BLPs, blocks the binding of the hormone to cellular receptors and inhibits the clonal growth of SCLC in vitro and the growth of SCLC xenografts in vivo. These results demonstrate that BLPs can function as autocrine growth factors for human SCLC.

Monoclonal-antibody-defined human lung tumour cell-surface antigens

A panel of 3 monoclonal antibodies (MAbs) directed against human lung tumour cell-surface antigens has been produced following immunizations with the established small-cell lung cancer (SCLC) cell line, NCI-H69, and with another SCLC cell line, COR-L32, recently derived from clinical material. One MAb, B10/12, reacted strongly with SCLC, immunoprecipitated a protein having an MW of 100kd and failed to react significantly with non-small-cell lung cancer (NSCLC) in radioimmunoassay and in an immunohistochemical assay. MAbs E10/5 and 2G3 reacted extensively with SCLC but also showed significant reactivity with NSCLC. MAb E10/5 immunoprecipitated a protein with an MW of 80kd but no appreciable protein was specifically precipitated by MAb 2G3. Unlike MAb 2G3, both MAbs B10/12 and E10/5 reacted strongly with selected neuroblastomas whereas only MAbs 2G3 and E10/5 reacted significantly with melanoma. All 3 MAbs reacted with breast carcinomas. Other non-pulmonary tumours thus far examined failed to react with the MAbs in radioimmunoassay or immunohistochemical assay. Immunocytochemistry and the use of viable cells in radioimmunoassay confirmed that the antigenic determinants recognized by these MAbs were surface located.

Improved antigen detection in ethanol-fixed cytologic specimens. A modified avidin-biotin-peroxidase complex (ABC) method

A new amplification technique is described for the detection of small amounts of antigen in ethanol-fixed cytologic specimens and formalin-fixed tissues. By adding a third antibody layer to the already sensitive avidin-biotin immunoperoxidase system, we have demonstrated a considerable increase in both the quantitative and qualitative aspects of this immunostaining method. In evaluating this technique, we employed a previously defined small cell lung carcinoma cell surface antigen system and monoclonal antibodies.

Monoclonal antibodies. Their promise for tumor diagnosis, staging, and therapy

Monoclonal antibodies will have utility as tools for diagnosis, staging, and therapy of malignant disease. Investigators have produced monoclonal antibodies that are directed against tumor-associated antigens and have varying degrees of cross-reactivity against normal tissues. These reagents have homogeneous molecular structure, recognize specific antigenic sites, can be produced in mass quantities, and are easily purified. Clinical trials with monoclonal antibodies are in progress and suggest modest toxicity and potential therapeutic efficacy.

Radioimmunoimaging of human small cell lung carcinoma with I-131 tumor specific monoclonal antibody

In this study, an IgM monoclonal antibody (MAb600D11) directed against human small cell lung cancer (NCI-H69) was radiolabeled with iodine-131, and the biodistribution and image quality of the radiolabeled antibody was evaluated. Radiolabeling was achieved in a solid-phase system consisting of 1,3,4,6-tetrachloro-3a,6a-diphenylglycoluril. Labeling efficiencies and protein purification were accomplished using gel exclusion chromatography while radioimmunoreactivity was determined using a solid-phase radioimmunoassay procedure. The biodistribution of I-131-labeled MAbs was determined in Sprague-Dawley rats up to 7 days after injection. Highest organ concentrations were observed in liver (3.91 +/- 0.47 (SD) and 0.17 +/- 0.04 (SD) mean percent injected dose at 1-7 days after injections) and in thyroid (5.33 +/- 0.71 (SD) and 5.32 +/- 2.01 (SD) mean percent injected dose at 1-7 days after injection). Nude mice, bearing either a small cell lung tumor (NCI-H69) or a nonspecific tumor (adenocarcinoma), were injected with 400-800 microCi of I-131 labeled monoclonal antibody. Optimum tumor visualization was observed 2-4 days after injection with tumor concentrations as high as 10.4% of the initial injected dose. The results demonstrated that radioimmunoimaging of human small cell lung carcinoma was feasible with the tumor-specific IgM I-131-labeled MAb.

Clinical uses of monoclonal antibodies

Immunization of animals for the purpose of generating antisera for clinical and experimental use results in the production of antibodies with multiple specificities directed at the parent antigen. Furthermore, if the immunogen contains contaminants of a highly immunogenic nature, large amounts of irrelevant antibody will be generated and which must subsequently be absorbed. The unpredictable nature of heteroantisera can be overcome by adopting the monoclonal antibody technique which allows one to produce standardized antibody with well defined and selected specificity toward a given epitope on a macromolecule. Cross-reactions are not eliminated by monoclonal antibodies.

Monoclonal antibodies specific for two different histological types of human lung carcinoma

Hybridomas secreting monoclonal antibodies specific for human lung cancer were produced by fusing immunized mouse spleen cells with mouse myeloma line X63-Ag8.653. Prior to fusion, BALB/c mice were immunized with two different histological types of human lung cancer (Squamous cell carcinoma and adenocarcinoma) obtained from surgery. An immunocytoadherence test was used to select hybridomas secreting antibodies that bound the patient's lung tumor, but did not bind to a B-lymphoblastoid cell line derived from the same patient. Five stable antibody-producing hybrids have been established and cloned. The antibodies produced by these clones have been characterized according to their light and heavy chain isotypes and for their specificity. In addition to binding to the tumor used for immunization, the antibodies bound to other lung tumors of the same histological type (i.e., squamous cell or adenocarcinoma). This reactivity was observed with both established lung tumor cell lines and with fresh tumors obtained from biopsy of patients in our clinic. Some significant reactivity was also observed with large cell carcinoma but the antibodies did not react with small cell carcinomas of the lung, bronchiolo-alveolar cell carcinoma, cancer of the esophagus and stomach, melanomas, several types of leukemias, normal human lung tissue, fibroblasts, or erythrocytes of type A, B, or O. Two of the five antibodies, 5C7 and 5E8 cross-reacted with one breast cancer obtained from surgery, and 5C7 also cross-reacted with one melanoma biopsy specimen. These results suggest that we have generated monoclonal antibodies that recognize a set of antigenic determinants that are commonly expressed on a portion of human lung tumors that are not detectable on a variety of other human tumors or normal human tissue.