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Tumor burden and clonality in multiple intestinal neoplasia mouse/normal mouse aggregation chimeras
M R Novelli1, H Wasan, I Rosewell
1Department of Histopathology, University College London, London WC1E 6JJ, United Kingdom. m.novelli@ucl.ac.uk
Abstract:
Aggregation chimeras were formed between C57BL/6 mice heterozygous for the Apc(min) (Min) mutation and wild-type SWR mice, that differ in their Pla2g2a status, a modifier of Apc(min), and also in their resistance to intestinal polyp formation. Variation in the dolichos biflorus agglutinin-staining patterns of the intestines of these mouse strains was used to determine the chimeric composition of the intestine in individual mice and to examine the clonal composition of adenomas. Macroscopic adenoma numbers in chimeric mice were compared with the expected adenoma numbers based on the percentage of C57BL/6J-Apc(min/+) epithelium in individual mice. These results unexpectedly show that there was no apparent inhibitory effect of the SWR-derived (Pla2g2a wild-type) tissue on adenoma formation in the C57BL/6J-Apc(min/+) epithelium. This suggests that the main genetic modifiers of the Min phenotype act at a cellular or crypt-restricted level with no discernable systemic effect. All adenomas were seen to contain C57BL/6J-Apc(min/+)-derived epithelium, confirming that the germ-line mutation of the mApc gene is necessary to initiate tumorigenesis in this model system, and that the mApc gene acts in a cell autonomous fashion.
Insights
Genetic modifiers of intestinal polyp formation in Apc(min) mice do not have systemic effects. Instead, they act at a cellular level, influencing adenoma development within specific tissues.
Area of Science:
- Genetics
- Cancer Biology
- Mouse Models
Background:
- The Apc(min) mouse model is crucial for studying intestinal tumorigenesis.
- Genetic modifiers, such as Pla2g2a, influence polyp formation in this model.
- Understanding modifier gene action is key to deciphering cancer development.
Purpose of the Study:
- To investigate the impact of genetic modifiers on intestinal adenoma formation using aggregation chimeras.
- To determine if wild-type tissue can inhibit polyp development in Apc(min) epithelium.
- To elucidate the level at which genetic modifiers of the Min phenotype exert their effects.
Main Methods:
- Formation of aggregation chimeras between C57BL/6 Apc(min/+) and wild-type SWR mice.
- Utilizing Dolichos biflorus agglutinin staining to assess chimeric intestinal composition.
- Comparing observed adenoma numbers with expected numbers based on epithelial contribution.
Main Results:
- No significant inhibitory effect of wild-type SWR-derived tissue on Apc(min/+) epithelium was observed.
- Adenoma formation was not systemically suppressed by the presence of wild-type tissue.
- All observed adenomas originated from C57BL/6J-Apc(min/+) epithelium, confirming the necessity of the Apc mutation.
Conclusions:
- Genetic modifiers of the Min phenotype primarily act at a cellular or crypt-restricted level.
- These modifiers do not appear to have a discernible systemic effect on intestinal tumorigenesis.
- The Apc gene mutation is essential for initiating intestinal tumorigenesis in a cell-autonomous manner.