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The use of daunomycin-antibody immunoconjugates in managing soft tissue sarcomas: nude mouse xenograft model
1Cancer Center, University of Illinois at Chicago 60612.
Abstract:
Analysis of human fibrosarcoma cells exposed to radiolabeled monoclonal antibody 19-24, which recognizes sarcoma-associated antigen p102, revealed that over 54% of the cell surface-bound radioactivity was internalized. No modulation of cell surface p102 antigen by monoclonal antibody 19-24 was observed in human fibrosarcoma cells. Monoclonal antibody 19-24 coupled to daunomycin via a dextran bridge was found to be most effective. In different preparations, the daunomycin:total protein molar ratio ranged from 1.9 to 6.1. In vitro cytotoxicity studies using human fibrosarcoma cells showed that, at 10 micrograms/ml concentration, this immunoconjugate was 79.4% as efficient as free daunomycin and, at 1 microgram/ml concentration, 36.8% as efficient. Control nonspecific murine monoclonal antibody P3 immunoconjugates were relatively ineffective. The distribution of 14C-Adriamycin, 125I-labeled monoclonal antibody 19-24, and 125I-labeled 19-24 immunoconjugate was also evaluated over a 24-h period in tumor and normal tissues of athymic mice bearing a human fibrosarcoma xenograft. Poor uptake of radiolabeled Adriamycin by the tumor tissue was observed. The level of 14C radioactivity in the tumor tissue never exceeded 1% of the total injected dose and was 24.8-fold lower than the radioactivity found in the spleen tissue. Tumor tissue uptake of radiolabeled monoclonal antibody 19-24 was characterized by the high tumor tissue:blood ratio of 1.62 +/- 0.28 (SD). However, for monoclonal antibody 19-24 immunoconjugates, this ratio decreased to 0.66 +/- 0.05, which was still higher than normal (liver, 0.48 +/- 0.02; lung, 0.48 +/- 0.07; spleen, 0.28 +/- 0.01) or nonspecific monoclonal antibody P3 immunoconjugates (0.22 +/- 0.03). Thus, it appears that, compared to free daunomycin, monoclonal antibody 19-24 immunoconjugates may be more efficient and less cytotoxic to normal tissues.
Insights
Monoclonal antibody 19-24 effectively internalizes into fibrosarcoma cells and, when conjugated with daunomycin, shows potent anti-cancer activity. This immunoconjugate demonstrates improved efficiency and reduced normal tissue toxicity compared to free daunomycin.
Area of Science:
- Oncology
- Immunology
- Pharmacology
Background:
- Monoclonal antibody 19-24 targets sarcoma-associated antigen p102 on human fibrosarcoma cells.
- Internalization of cell surface-bound radiolabeled antibody 19-24 was observed, with over 54% uptake.
- No modulation of p102 antigen expression was detected after antibody exposure.
Purpose of the Study:
- To evaluate the efficacy of monoclonal antibody 19-24 conjugated with daunomycin as an immunoconjugate for fibrosarcoma treatment.
- To compare the in vitro cytotoxicity and in vivo tissue distribution of the immunoconjugate against free daunomycin and control antibodies.
Main Methods:
- Human fibrosarcoma cells were exposed to radiolabeled monoclonal antibody 19-24.
- In vitro cytotoxicity assays were performed using the antibody-daunomycin immunoconjugate at varying concentrations.
- In vivo biodistribution studies were conducted in athymic mice bearing human fibrosarcoma xenografts, comparing radiolabeled Adriamycin, antibody 19-24, and the immunoconjugate.
Main Results:
- The antibody-daunomycin immunoconjugate exhibited significant in vitro cytotoxicity, reaching 79.4% of free daunomycin's efficiency at 10 µg/ml.
- In vivo studies showed poor tumor uptake of radiolabeled Adriamycin, while antibody 19-24 demonstrated favorable tumor tissue to blood ratios.
- The immunoconjugate showed improved tumor tissue targeting compared to non-specific antibody conjugates, with reduced uptake in normal organs.
Conclusions:
- Monoclonal antibody 19-24 immunoconjugates are a promising approach for targeted fibrosarcoma therapy.
- These immunoconjugates offer potential for increased anti-cancer efficacy and reduced systemic toxicity compared to conventional chemotherapy.
- Further investigation into antibody-drug conjugates for sarcoma treatment is warranted.