Monoclonal antibodies against human astrocytomas and their reactivity pattern

The establishment of hybridomas after fusion of X63-Ag8.653 mouse myeloma cells and splenocytes from mice hyperimmunized against human astrocytomas is presented. The animals were primed with 5 × 106 chemically modified uncultured or cultured glioma cells. Six weeks after the last immunization step an intrasplenal booster injection was administrated and 3 days later the spleen cells were prepared for fusion experiments. According to the specificity analysis of the generated antibodies 7 hybridoma products (MUC 7-22, MUC 8-22, MUC 10-22, MUC 11-22, MUC 14-22, MUC 15-22 and MUC 2-63) react with gliomas, neuroblastomas and melanomas as well as with embryonic and fetal cells but do not recognize non-neurogenic tumors. The selected monoclonal antibodies (McAbs) of IgG1 and IgG2a isotypes are not extensively characterized but these antibodies have been demonstrated to be reactive with a panel of glioma cell lines with varying patterns of antigen distribution. Using the McAbs described above and a series of cryosections of glioma biopsies and paraffin sections of the same material as well as glioma cultures established from these, variable antigenic profiles among glioma cell populations could be demonstrated. From these results it is evident that there is not only a distinct degree of antigenic heterogeneity among and within brain tumors, but also that the pattern of antigenic expression can change continuously. Some of the glioma associated antigens recognized by the selected antibodies persist after fixation with methanol/acetone and Karnovsky's fixative and probably are oncoembryonic/oncofetal antigen(s). The data suggest that the use of McAbs recognizing tumor associated oncofetal antigens in immunohistochemistry facilitates objective typing of intracranial malignancies and precise analysis of fine needle brain/tumor biopsies in a sensitive and reproducible manner

Localization of experimental glioma grafts by means of iodinated monoclonal antibodies and radionuclide imaging.

Purified McAbs (14AC1) of IgG2a isotype raised against an experimental rat glioma (79 FR-G-41) were labeled with Na131I and used for in vivo imaging of glioma grafts by external body seintigraphy. Normal mouse131I-IgG was applied as control for non-specific uptake of proteins in the tumor. Nude mice bearing glioma grafts were injected i.v. with 15 μg of the131I-McAb or131I-IgG with an activity of approximately 150 μCi. Scands obtained 30 min, 24, 48, 72, and 96 h after injecting the intact131I-14AC1 antibody demonstrated enrichment of radioactivity in the tumors. The tumors were clearly visible 48 h after injection of131I-labeled antibody. The time course experiments showed that the uptake of131I-14AC1 antibody in the glioma grafts was the result of specific antigen binding. Intact antibody provided adequate tumor visualization in the scientigrams without background subtraction. Therefore, this technique appears promising for in vivo tumor detection and may offer the possibility of improvement in the evaluation of diagnostic and therapeutic approaches to human gliomas