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Uptake kinetics of monoclonal antibodies by human malignant melanoma multicell spheroids
Abstract:
Detailed uptake kinetics by multicell spheroids of three tumor associated monoclonal antibodies was investigated. The spheroids were established from a human melanoma cell line and the human colon adenocarcinoma cell line HT29 as in vitro models of poorly vascularized micrometastases in vivo. The selected antibodies 96.5, 140.240, and OST15 showed a wide range of reactivity against the melanoma cell but they all had negligible binding with the colon cancer cell. Uptake of the antibodies by small spheroids (about 300 micron diameter) was generally sigmoidal in shape with respect to incubation time, and amount of uptake followed the same trend of immunoreactivity of the antibodies with single cells. The correlation was weaker for spheroids with diameter greater than 500 micron presumably due to the increasing size of the necrotic core. By varying the concentration of the antibodies in the incubation medium from tracer dose (0.2 microgram/ml) to a higher dose (3 micrograms/ml), negligible changes in the amount of antibodies bound with their target spheroids were observed. Nonspecific binding between antibodies and spheroids, however, resulted in proportional increase in uptake.
Insights
Antibody uptake kinetics in tumor spheroids were studied. Uptake correlated with single-cell binding for small spheroids, but was weaker in larger ones due to necrosis, with minimal changes in bound antibody amounts across concentrations.
Area of Science:
- Oncology
- Immunology
- Biomedical Engineering
Background:
- Tumor-associated monoclonal antibodies are crucial for targeted cancer therapy.
- Understanding antibody uptake in tumor models is vital for optimizing drug delivery.
- Multicell spheroids serve as in vitro models for poorly vascularized micrometastases.
Purpose of the Study:
- To investigate the uptake kinetics of three tumor-associated monoclonal antibodies in human melanoma and colon adenocarcinoma spheroids.
- To correlate antibody uptake with their immunoreactivity and spheroid size.
- To assess the impact of antibody concentration on specific and nonspecific binding.
Main Methods:
- Established multicell spheroids from human melanoma and HT29 colon adenocarcinoma cell lines.
- Incubated spheroids with monoclonal antibodies (96.5, 140.240, OST15) at varying concentrations.
- Analyzed antibody uptake kinetics and binding using spheroid size and immunoreactivity as parameters.
Main Results:
- Antibody uptake showed sigmoidal kinetics in small spheroids (approx. 300 micron), correlating with single-cell immunoreactivity.
- Uptake correlation weakened in larger spheroids (>500 micron) due to necrotic cores.
- Antibody concentration changes (0.2-3 microgram/ml) had minimal effect on specific binding, but increased nonspecific binding.
Conclusions:
- Antibody uptake in tumor spheroids is influenced by spheroid size and cellular immunoreactivity.
- Necrosis in larger spheroids impedes predictable antibody distribution.
- Nonspecific binding is a significant factor affecting overall antibody uptake, independent of target antigen levels.