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Tumour-growth suppression in nude mice by a murine monoclonal antibody: factors hampering successful therapy
C Johansson1, S Segrén, L Lindholm
1Pharmacia CanAg, Göteborg, Sweden.
Abstract:
The murine MAb C215 has been shown to mediate ADMMC in vitro and to have a tumour-growth-suppressive effect on xenografted COLO 205 human colocarcinoma cells in nude mice. To overcome the limitations of MAb therapy, it is necessary to understand the underlying mechanisms of tumour-growth suppression. In the present work, we have used C215 to define the importance of different parameters involved in tumour therapy with murine IgG2a antibodies. The results show that there exists a period of roughly 2 days after inoculation into animals during which the tumour cells are sensitive to an inhibitory antibody-mediated effect. After this initial period, the in-vivo sensitivity of tumour cells to antibody-mediated inhibition is much reduced. Tumour cells can remain "dormant" and, despite ongoing antibody treatment, develop into tumours with a reduced growth rate, which is not caused by outgrowth of antigen-deficient tumour cells. Finally, a pronounced dependence of antibody-mediated tumour suppression on antibody dose was observed.
Insights
Murine MAb C215 shows tumor-suppressive effects, but efficacy depends on early treatment post-inoculation. Tumor cells become less sensitive after two days, with dose impacting antibody-mediated tumor suppression.
Area of Science:
- Oncology
- Immunology
- Pharmacology
Background:
- Murine monoclonal antibody (MAb) C215 demonstrates antibody-dependent cellular cytotoxicity (ADMMC) in vitro.
- C215 exhibits tumor-growth suppression against human colorectal carcinoma xenografts in nude mice.
- Understanding MAb therapy mechanisms is crucial for overcoming treatment limitations.
Purpose of the Study:
- To define parameters influencing tumor therapy with murine IgG2a antibodies using MAb C215.
- To investigate the temporal sensitivity of tumor cells to antibody-mediated inhibition.
- To assess the impact of antibody dose on tumor suppression.
Main Methods:
- Utilized murine MAb C215 in a xenograft model of human colorectal carcinoma.
- Administered antibody treatment at various time points post-tumor cell inoculation.
- Monitored tumor growth rate and characterized tumor cell populations.
Main Results:
- Tumor cells exhibit sensitivity to antibody-mediated inhibition for approximately two days post-inoculation.
- In vivo sensitivity significantly decreases after this initial two-day window.
- Tumor cells can enter a dormant state, showing reduced growth rates without antigen loss, despite continuous antibody treatment.
- A clear dose-dependent relationship was observed for antibody-mediated tumor suppression.
Conclusions:
- Early administration of MAb C215 is critical for effective tumor suppression.
- Tumor cell sensitivity to antibody therapy is time-dependent.
- Antibody dose is a significant factor in achieving tumor growth inhibition.