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Nonimmunogenic sarcomas induced by 3-methylcholanthrene treatment of murine fibroblasts in diffusion chambers
Abstract:
A 30-mug dose of 3-methylcholanthrene (MCA) was applied for 1 week to normal BALB/c fibroblasts in cell-impermeable diffusion chambers (DC) in the peritoneal cavities of BALB/c micemtwo groups of DC cultures, in which the carcinogen was given during weeks 1 and 5 of cultivation, respectively, were compared for the frequency of malignant transformation and for the immunogenicity of the resulting neoplasms. The cells from each DC were transplanted sc into immunodepressed semisyngeneic mice for assay of their tumorigenicity. Although tumor yield was similar in the 2 groups (25 and 22%, respectively), there was clear difference in immunogenicity; 10 of 16 sarcomas from fibroblasts treated during week 1 of culture were nonimmunogenic, whereas 8 of 9 tumors from the older cultures were immunogenic (P less than 0.02). A kinetic study of normal fibroblasts in DC revealed that cells proliferated rapidly, with a peak at day 4 after seeding, then grew progressively more slowly and ceased to replicate between 14 and 28 days of culture. Thus there was a notable difference at the moment of MCA application in the growth phase of the target cell population of the first as compared with the fifth week of culture, possible related to the different expression of tumor-associated transplantation antigens in the resulting neoplasms.
Insights
Carcinogen exposure timing impacts cancer immunogenicity. Fibroblasts treated earlier with 3-methylcholanthrene (MCA) produced non-immunogenic tumors, while later exposure yielded immunogenic ones.
Area of Science:
- Oncology
- Immunology
- Cell Biology
Background:
- 3-methylcholanthrene (MCA) is a potent chemical carcinogen.
- Fibroblast cell cycle progression influences malignant transformation.
- Tumor-associated transplantation antigens (TATA) are crucial for immune recognition.
Purpose of the Study:
- To investigate the effect of carcinogen application timing on tumor immunogenicity.
- To compare malignant transformation and immunogenicity of BALB/c fibroblasts treated with MCA at different culture weeks.
- To correlate fibroblast growth phase with the immunogenicity of resulting neoplasms.
Main Methods:
- BALB/c fibroblasts were cultured in diffusion chambers (DC) in mice.
- MCA was administered during week 1 or week 5 of fibroblast culture.
- Cells were transplanted into immunodepressed mice to assess tumorigenicity.
- Tumor immunogenicity was evaluated based on rejection or acceptance.
Main Results:
- Tumor yield was similar (25% vs. 22%) regardless of MCA application timing.
- Fibroblasts treated in week 1 yielded 10/16 non-immunogenic tumors.
- Fibroblasts treated in week 5 yielded 8/9 immunogenic tumors (P < 0.02).
- Fibroblast proliferation peaked at day 4 and ceased by day 14-28.
Conclusions:
- The growth phase of target cells at the time of carcinogen exposure significantly impacts tumor immunogenicity.
- Early MCA exposure during rapid proliferation leads to non-immunogenic tumors.
- Later MCA exposure during slower growth or quiescence results in immunogenic tumors, potentially due to altered TATA expression.