Herbert F. Oettgen

We evaluated the ability of human recombinant granulocyte colony-stimulating factor (rhG-CSF) to prevent chemotherapy-induced neutropenia or to accelerate recovery from this complication and thus allow patients to receive full doses of antineoplastic agents on time, according to protocol design. Twenty-seven patients with transitional-cell carcinoma of the urothelium who were undergoing treatment with methotrexate, doxorubicin, vinblastine, and cisplatin were given rhG-CSF (up to 60 micrograms per kilogram of body weight per day) before their first cycle of combination chemotherapy, during the first cycle, or at both points. Treatment with rhG-CSF before chemotherapy resulted in a dose-dependent increase in the absolute neutrophil count. Treatment with rhG-CSF after chemotherapy significantly reduced the number of days (91 percent) per patient on which the absolute neutrophil count was 1000 per microliter or less (P = 0.0039), reduced the number of days (1 vs. 35) on which antibiotics were used to treat fever and neutropenia, and significantly increased the percentage (100 vs. 29 percent) of patients qualified to receive planned chemotherapy on day 14 of the treatment cycle (P = 0.0015). In addition, the incidence of mucositis was significantly decreased (11 vs. 44 percent, P = 0.041), as was its severity. These findings demonstrate that rhG-CSF is a potent stimulus of normal neutrophil proliferation and maturation. In addition, its administration can reduce both the hematopoietic and oral toxicity of chemotherapy.

Mouse monoclonal antibody AbR24 has a high degree of specificity for human melanoma cells when tested on viable cultured cells using the protein A mixed hemagglutinin serological assay. The antigen detected by this antibody has been isolated from melanoma cells and shown to be GD3 ganglioside by compositional and partial structural analysis and by comparison with authentic GD3 in thin layer chromatography (TLC). AbR24 reacts with authentic GD3, but not with any other ganglioside tested. Using TLC and reactivity with AbR24, a wide range of cells and tissues was examined for the presence of GD3. A new serological assay, termed glycolipid-mediated immune adherence, was devised for assaying the reactivity of AbR24 with gangliosides. Melanomas (cultured cells or tumor tissue) were shown to have GD3 and GM3 as major gangliosides. Other cells and tissues examined also contained GD3, but usually only in low amounts. Melanomas (and MOLT-4, a T cell line) were characterized by a simplified ganglioside profile with GD3 and GM3 as major components. The apparent discrepancy between the ubiquitous presence of GD3 and the serological specificity of AbR24 for melanoma cells can be explained in terms of localization and concentration of GD3 in different cells.

R24 is an IgG3 mouse monoclonal antibody that identifies GD3, a prominent ganglioside on the surface of melanoma cells and other cells of neuroectodermal origin. Twelve patients with metastatic melanoma were treated with R24 at three dose levels, 8, 80, or 240 mg/m2, over a period of 2 weeks. Peak antibody levels in the serum were dose related and ranged from less than 0.1 to 62 micrograms/ml. Inflammatory reactions (urticaria, pruritus, erythema, subcutaneous ecchymoses) were observed around tumor sites in patients treated at doses greater than or equal to 80 mg/m2. Tumor biopsies during and after treatment showed lymphocyte and mast cell infiltration, mast cell degranulation, and complement deposition. Side effects were mild and were readily controlled by antihistamines. Major tumor regression has been observed in three patients.

Eighteen mouse monoclonal antibodies were selected for reactivity with cell surface antigens of the immunizing human melanoma cell line SK-MEL-28. Six distinct antigenic systems were defined by direct serological assays and absorption tests with a panel of 41 cell lines derived from normal and malignant human tissues. Biochemical analysis indicated that two of the antigens are glycoproteins with molecular sizes of 95,000 and 150,000 daltons (gp95 and gp150). Two other antigenic systems (O5 and the R24 group) are associated with heat-stable molecules having the characteristics of glycolipids. The remaining two antigens (M19 and R8) are heat labile, but molecular characterization has not been possible. Each of the antigenic systems has a distinctive pattern of distribution on various cell types, varying from a broad representation to a more restricted occurrence. O5 appears to be a species antigen, being present on virtually every human cell type tested. gp95, gp150, M19, and R8 are found on a characteristic proportion of melanomas, astrocytomas, and epithelial cancers and on normal kidney cells. The antigen defined by the R24 antibody has the most restricted distribution of all. Reactivity is found with melanomas and astrocytomas, whereas epithelial cell types, fibroblasts, and cells of hematopoietic origin lack R24. Although occurrence of gp95, gp150, M19, and R8 distinguishes a small subset of melanomas not expressing these antigens, R24 is found on all melanoma cells.

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