ganglioside--gd2 and Chromosome-Deletion

Rare tumor cells circulating in the hematopoietic system can escape identification. On the other hand, the nature of these cells, positive for an immunologiCal tumor marker, cannot be determined without any genetic information.. To overcome these problems a novel computer assisted scanning system for automatic cell search, analysis, and sequential repositioning was developed. This system allows an exact quantitative analysis of rare tumor cells in the bone marrow and peripheral blood by sequential immunological and molecular cytogenetic characterization.. In that virtually all tumor cells in a mixing experiment could be recovered unambiguously, we can conclude that the sensitivity of this approach is set by the number of cells available for analysis. Sequential FISH analyses of immunologically positive cells improve both the specificity and the sensitivity of the microscopic minimal residual disease detection.

Topics: Biomarkers, Tumor; Blood Cell Count; Bone Marrow Examination; Chromosome Aberrations; Chromosome Deletion; Chromosomes, Human, Pair 1; Chromosomes, Human, Pair 17; Diagnosis, Computer-Assisted; DNA Probes; Fluorescein-5-isothiocyanate; Fluorescent Antibody Technique, Indirect; Fluorescent Dyes; Gangliosides; Gene Amplification; Gene Expression Profiling; Genes, myc; Humans; In Situ Hybridization, Fluorescence; Indoles; Neoplasm, Residual; Neoplastic Cells, Circulating; Neuroblastoma; Sensitivity and Specificity; Trisomy; Tumor Cells, Cultured

Recombinant techniques allow one to engineer an antibody molecule and, in this way, manipulate its properties and functions. We engineered a chimeric human/mouse antibody to the tumor-associated antigen ganglioside GD2, with the aim of decreasing its serum half-life, maintaining its full antigen-binding capacity, and deleting its effector functions, thus making it a potentially useful reagent for the radioimaging of tumors. To this end, the constant region of the human gamma 1 chain was mutated by deleting the second domain (CH2). Here we show that the CH2-deleted antibody (ch14.18-delta CH2) was cleared from the blood of athymic (nu/nu) mice bearing human melanoma tumors with the same kinetics as human IgG F(ab')2. At a beta t1/2 of 12 hr, 0.9% of the injected dose of 125I-labeled ch14.18-delta CH2 was found per milliliter of blood 24 hr after i.v. injection. In biodistribution experiments, 125I-labeled ch14.18-delta CH2 targeted specifically to melanoma xenografts, achieving optimal tumor-to-tissue ratios 12-16 hr after i.v. injection. ch14.18-delta CH2 was localized to the melanoma tumors more rapidly and with better localization ratios than the intact chimeric antibody ch14.18. Sixteen hours after i.v. injection, the tumor-to-blood and tumor-to-liver ratios of ch14.18-delta CH2 were 5 and 12, respectively, while optimal localization ratios obtained for ch14.18 were 1 and 5, respectively, but 96 hr after injection. A reagent such as ch14.18-delta CH2 should be useful for radioimmunodetection of human tumors because of reduced immunogenicity, increased targeting specificity, and rapid clearance from circulation.

Topics: Animals; Cell Line; Chimera; Chromosome Deletion; Fluorescent Antibody Technique; Gangliosides; Humans; Immunoglobulin Fab Fragments; Immunoglobulin G; Melanoma; Metabolic Clearance Rate; Mice; Mice, Nude; Neoplasm Transplantation; Transplantation, Heterologous