Human-human hybridomas for the study of anti-tumor immune response in patients with colorectal cancer

Modified cytokeratins expressed on the surface of carcinoma cells undergo endocytosis upon binding of human monoclonal antibody and its recombinant Fab fragment

Previously, we have reported on successful imaging of colon, rectal, and pancreatic carcinomas in patients by using a radiolabeled all-human monoclonal antibody, COU-1, directed against modified cytokeratin. To further develop this antibody for use as an immunoconjugate, COU-1 was cloned by phage display selection and the human Fab fragment was expressed in bacteria. Analysis by confocal laser scanning microscopy demonstrated that COU-1 bound in a uniform punctate pattern to the surface of viable carcinoma cells stained at 4 degrees C, and binding increased significantly when cells were cultured on fibronectin, laminin, or collagen IV. In the case of fibronectin, COU-1 staining was particularly enhanced at intercellular junctions. When carcinoma cells were cultured with COU-1 at 37 degrees C for 6 hr, the antibody was found in large perinuclear vesicles and the punctate surface staining was significantly reduced. Similar results were obtained using intact IgM COU-1 and the recombinant Fab fragment. Immunohistological studies indicated that COU-1, in contrast to murine monoclonal antibodies against normal cytokeratin 8 and 18, could differentiate between malignant and normal colon epithelia, and between colon cancer metastasis in the liver and surrounding normal hepatocytes. Within biopsies of malignant tissue, COU-1 exhibited membrane-associated staining of proliferating cells, while resting cells had a filamentous pattern. Thus, modified cytokeratin at the surface of carcinoma cells may represent a new target for immunoconjugates and may explain the promising results of the phase I/II clinical study.

Successful in vitro antigen-dependent activation of 24-hour-old peripheral blood lymphocytes

We describe a simple, rapid and reproducible in vitro culture system in which human peripheral blood lymphocytes (PBLs), donated 24 h prior to initiation of culture can be stimulated to produce antigen-specific antibodies. Peripheral blood lymphocytes purified by Ficoll-Hypaque centrifugation were passed over a G10 Sephadex column and then activated in vitro in the presence of 0.003% staphylococcus Cowan A, 2.8 x 10(-6) M indomethacin and appropriate concentrations of tetanus toxoid antigen. After the first 24 h in culture, a five-fold concentrated supernatant from an allogeneic mixed lymphocyte culture was added. The cell surface phenotypes of the PBLs were analyzed by flow cytometry at the initiation and termination of culture, in order to provide a comprehensive characterization of the cellular composition of a successful in vitro stimulation system. Our results clearly show that the majority of peripheral blood B cells can be induced to an activated stage (blast transformation) and interleukin 2 (IL-2) receptor expression, following very simple manipulations of the lymphoid population. Tetanus toxoid-specific antibody production can be readily generated in this cell population. In contrast, T cells were not activated to express IL-2 receptors and reach blast transformation, and did not show appreciable proliferation. Our system provides a population of B cells producing antibodies of desired specificity which could be utilized for the generation of human hybridomas or could serve as a donor population for antibody engineering via the combinatorial library approach. Careful light scattering and cell surface phenotypic analyses of the cells entering, proliferating and differentiating in these cultures enabled several novel observations to be made.

Immunoscintigraphy of colon cancers with the human monoclonal antibody COU-1

The human monoclonal immunoglobulin M (IgM) antibody, COU-1 is obtained from a human-human hybridoma, which is derived by fusion between a human B-lymphoblastoid cell line and lymphocytes obtained from mesenteric lymph nodes from a patient with colorectal cancer. COU-1 recognizes a 43 kilodaltons intracellularly located cytokeratin-like protein, strongly expressed by adenocarcinoma tissue as compared to normal tissues. In tumor-bearing nude mice, antibody COU-1 labeled with 125I has been shown to accumulate in human colon cancer grafts when compared to human melanoma grafts and the normal mouse tissues. The observed accumulation was sufficient to be detected externally by immunoscintigraphy. Antigen-binding fragments of the antibody were also prepared and were shown to accumulate in colon cancer grafts. Improved tumor to normal tissue ratio was seen with the half-monomeric fragment, and the time required was reduced. In the clinic, five patients with suspected colorectal cancer were given 2 mg of 131I-labeled COU-1. No adverse effects were detected in any of the patients. Planar images were obtained on days 1, 2, 3, 5, and 7 after administration. The best images were obtained on days 5 and 7. Tumors were localized by immunoscintigraphy in four of the patients. Of these patients, surgery revealed that three of them had primary colorectal cancers located in the cecum, the ascending colon, and the rectum, respectively, while one patient had a pancreatic cancer. The smallest lesion observed had a diameter of 3 cm. In one of the patients, otherwise undiagnosed multiple liver metastases were revealed by the immunoscintigraphy and confirmed at surgery. An x-ray of the colon performed on the fifth patient had shown a stricture in the descending colon suspected to be caused by cancer. The tumor scintigraphy showed no accumulation of the antibody. Surgery revealed that the stricture was caused by adherence and not cancer. These findings are encouraging for further studies of this human monoclonal antibody in cancer patients.

A cancer-reactive human monoclonal antibody derived from a colonic cancer patient treated with local immunotherapy

A human monoclonal antibody, YJ-37 (IgM) was generated through the fusion of human B lymphoblastoid cell line HO-323 with the regional lymph node lymphocytes from a colonic cancer patient who was treated with a local immunotherapy. This antibody was purified and conjugated with biotin, after which direct immunohistochemical staining was performed. The results revealed that YJ-37 selectively reacted with colonic cancer (7/19), gastric cancer (3/6), endometrial cancer (1/2) and colonic adenoma (7/13), but not with normal epithelia. Membrane immunofluorescence and FACS analysis also showed that YJ-37 bound to tumor cell surfaces. Furthermore, the chemical structure of the antigen defined by YJ-37 was analyzed by means of thin-layer chromatography immunostaining and ELISA. The results indicated that YJ-37 reacted with sialylated lacto-series carbohydrate chains, which have been reported to accumulate in cancer cells.

Tumour localization and pharmacokinetics of iodine-125 human monoclonal IgM antibody (COU-1) and its monomeric and half-monomeric fragments analysed in nude mice grafted with human tumour

Human monoclonal IgM antibodies reactive with cancer-associated antigens may not have the optimal imaging capability due to their large size. Fragmentation of human IgM is less than straight-forward due to the loss of immunoreactivity. From the human monoclonal IgM antibody COU-1 we have prepared monomeric and half-monomeric fragments, which retain the ability to bind to colon cancer cells in vitro. The pharmacokinetics and tumour localization were evaluated in nude mice bearing human colon adenocarcinoma and human melanoma grafts. Faster clearance from the circulation was seen for the smaller half-monomeric fragment with a half-life (rapid phase/slow phase) of 2 h/16 h compared with the intact antibody, 4 h/25 h, and the monomeric fragment, 3 h/27 h. Intact COU-1 as well as the fragments accumulated in the colon tumour graft. Higher amounts of radioactivity were found in the colon tumour as compared to normal organs for intact COU-1 at days 4 and 6, for the monomeric fragment at day 4, and for the half-monomeric fragment at day 2 after injection. This investigation demonstrates the favourable biodistribution of the half monomeric COU-1 fragment. The fast clearance of this fragment resulted in a tumour-to-muscle ratio as high as 22 on day 2 after injection. Also, only this fragment gave a positive tumour-to-blood ratio. Normal IgM and its fragments were used as controls. Radioimmunoscintigraphy demonstrated the colon tumour discriminatory properties of each of the three iodine-labelled antibody preparations.(ABSTRACT TRUNCATED AT 250 WORDS)

Use of a local immunotherapy as an adjunctive tool for the generation of human monoclonal antibodies from regional lymph nodes of colonic cancer patients

Human hybridomas were generated through the fusion of the human B-lymphoblastoid cell line HO-323 with the regional lymph node lymphocytes of colonic cancer patients who had received a local immunotherapy. A total of 353 hybridomas were obtained from 4 patients and 116 of these were found to secrete greater than or equal to 100 ng/ml human immunoglobulin. The efficiency was remarkably high as compared with that from patients without the local immunotherapy. Further immunohistological examination showed that 5 hybridomas secreted IgM which selectively reacted with colonic cancers. The results indicate that local immunotherapy could be an adjunctive tool for the generation of highly potent human hybridomas through augmenting the host's immunity.

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.

Distribution of immunoglobulins and secretory component in gastric cancer of the aged

The secretory immune system plays an important role in the local humoral immunity of the gastrointestinal tract. In order to evaluate humoral immunity in gastric cancer, distribution of immunoglobulins (Ig) and secretory component was immunohistochemically studied in 74 early and 15 advanced primary gastric cancers. In non-cancerous gastric mucosa, IgA and IgM, and secretory component were mainly identified in the cytoplasm of the intestinal metaplasia. In early gastric cancer of well-differentiated type, the localization of IgA and IgM, and secretory component was similar to that of intestinal metaplasia. In advanced gastric cancer, they were faintly observed and showed low positivity. The number of Ig-containing cells infiltrating cancerous stroma was enumerated. Immunoglobulin A-containing cells were dominant in the stroma of early gastric cancer. On the other hand, there were few Ig-containing cells in the stroma of advanced gastric cancer, and the number of IgA-containing and IgM-containing cells was also decreased. These results suggest that local humoral immunity is suppressed in gastric cancer, especially in advanced gastric cancer.

Human-human hybridoma producing monoclonal antibodies against colorectal cancer-associated antigens

Lymphocytes from lymph nodes draining the tumor region in patients with colorectal cancer were fused with two different human B-lymphoblastoid cell lines, LICR-LON-HMy-2 (HMy-2) and WI-L2-729-HF2 (729-HF2), to generate hybridomas synthesizing antibodies reacting with tumor-associated antigens. In this way 220 hybridomas were obtained which produce antibody reacting with colon cancer cells. All established clones produced IgM. Four human monoclonal antibodies have been further analyzed. The cell lines producing these antibodies are all hybrids based on DNA analysis. Three of the antibodies (G4146, B9165 and D4213) showed binding to differentiation antigens by immunocytochemical analysis on different cancer cell lines and normal human leucocytes and by immunohistochemical analysis on sections of frozen malignant and normal tissues, while the fourth (F11348) showed a reaction with all cells and tissues tested. Western blots of tumor extracts showed binding of G4146 to two components from colon cancer cells with Mr of 59 K and 61 K, while B9165 bound to a 43 K component and F11348 to several components with Mr from 30 to 200K. D4213 showed no binding in this analysis. The results obtained demonstrate the successful application of hybridoma technology to produce human monoclonals with reactivity to differentiation antigens.

A human monoclonal antibody derived from axillary lymph nodes of a breast cancer patient

A human hybridoma clone (A4-33) was established by fusion of human lymphoblastoid cells, HO-323, with lymphocytes of axillary lymph nodes obtained from a breast cancer patient. This clone has been stable, producing IgM for over 24 months. Enzyme-linked immunosorbent assay (ELISA) showed that monoclonal antibody A4-33 reacted strongly to MCF-7, and weakly to PANC-1 and HT-29, but not to other human malignant cell lines. The reactivity of A4-33 to MCF-7 was markedly reduced by treatment with periodate, but not affected or enhanced by neuraminidase or trypsin. Immunoperoxidase staining of normal human tissue sections showed that A4-33 reacted to acinar and ductal cells of the mammary gland and to ductal epithelial cells of the salivary gland, sweat gland, pancreas and bile duct. With malignant tumor sections, A4-33 reacted to breast cancer, pancreatic cancer and parotid cancer. These results suggested that A4-33 recognized the antigen which commonly exists on ductal epithelial cells of the exocrine gland.

Rat serum antibodies binding to high-molecular-weight glycoprotein(s) on syngeneic colon carcinomas, demonstrated by competition with rat monoclonal antibody

Sera from rats immunized to syngeneic 1,2-dimethylhydrazine colon carcinomas were analyzed for their ability to inhibit the binding of a syngeneic rat IgM monoclonal antibody (10B12) specific for high-molecular-weight glycoprotein(s) from rat colon carcinoma. Immunization with irradiated tumour cells or with tumour tissue extracts resulted in the appearance of a strong inhibiting activity. Sera of animals with established growing tumours and of females shortly after partus also inhibited binding of the monoclonal antibody, while unimmunized animals or animals immunized with irrelevant antigens had no inhibiting antibodies in their sera. Dimethylhydrazine-treated animals showed an increased titer of antibodies binding to the high-molecular-weight glycoprotein, but showed no inhibition of binding of the 10B12 monoclonal antibody. The syngeneic 10B12 rat antibody obviously does not reflect a rare event captured from a hyperimmune animal by the hybridoma technique but rather represents an antibody specificity frequently appearing in the immune response to tumours expressing the high-molecular-weight glycoprotein.