Tumor burden and clonality in multiple intestinal neoplasia mouse/normal mouse aggregation chimeras

Abstract

Aggregation chimeras were formed between C57BL͞6 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 C57BL͞6J-Apc min͞؉ epithelium in individual mice. These results unexpectedly show that there was no apparent inhibitory effect of the SWR-derived (Pla2g2a wildtype) tissue on adenoma formation in the C57BL͞6J-Apc min͞؉ 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 C57BL͞6J-Apc min/؉ -derived epithelium, confirming that the germline 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.

Generation of a unique strain of multiple intestinal neoplasia (Apc+/Min‐FCCC) mice with significantly increased numbers of colorectal adenomas

“…The conventional Apc +/ Min mouse has a nonsense mutation at codon 850 of the Apc gene and rarely lives beyond 120 d of age (as reported in the literature) [12]—(http://jaxmice.jax.org/jaxmice-cgi/jaxmicedb-cgi). These mice develop mammary tumors, 30–60 small intestinal adenomas and less than 2 colonic adenomas per mouse [8,12,13,20–43]. In contrast, the Apc Δ716 mice, which carry a neomycin cassette at codon 716, express a truncated Apc protein of approximately 80 kD and develop hundreds (250–650) of small intestinal adenomas but only 0.7–2.0 colorectal adenomas; the latter noted in mice fed a high fat diet [8,9,47].…”

“…The histopathological features of colorectal adenomas in both humans and Apc +/ Min mice are similar. However, the predominance of small intestinal adenomas, relatively few colorectal adenomas, the lack of colorectal adenocarcinoma [13,20–43] combined with the fact that the second hit of Apc is always LOH of the wild type Apc allele rather than a second mutation [62,63], is in contradistinction to human colorectal neoplasia [64,65]. We believe that the Apc +/ Min‐FCCC mouse is an ideal model to study chemoprevention of colorectal neoplasia for the following reasons: (1) The increased life span in our facility provides a larger window of opportunity of chemopreventive intervention.…”

“…The resulting point mutation in codon 850 produces a premature stop codon and a truncated polypeptide of approximately 95 kD [19]. These Apc +/ Min mice rarely live beyond 120 d of age [12] (http://jaxmice.jax.org/jaxmice-cgi/jaxmicedb.cgi) and are reported to develop 30–60 small intestinal adenomas and less than 2 colonic adenomas per mouse [13,20–43]. We undertook this present study based upon our initial observations that the Min breeding colony at the Fox Chase Cancer Center had an increased life span and greater numbers of colorectal adenomas than those mice housed at the Jackson Laboratory.…”

Bone Marrow Cells in Murine Colitis: Multi-Signal Analysis Confirms Pericryptal Myofibroblast Engraftment without Epithelial Involvement

“…The intestines were rinsed through with cold PBS, gently pressed flat and rolled in a proximal (inside) to distal (outside) manner and pinned as a “Swiss roll”, immersed in 20 volumes of methacarn fixative (methanol: chloroform: glacial acetic acid = 60∶30∶10) for 3 hours and stored in 70% ethanol at room temperature until routine paraffin wax embedding. In previous work [49] , we found that methacarn provided cleaner lectin histochemistry than neutral-buffered formalin (NBF)-fixed tissues, and our IHC was unaffected by this. Other visceral organs were also harvested (liver, kidney, spleen) as well as skin.…”

Multi‐ancestral origin of intestinal tumors: Impact on growth, progression, and drug efficacy

“…19 Numerous studies have demonstrated that some tumors from mice and humans have a multi-ancestral architecture. [20][21][22][23][24][25][26][27][28][29][30][31][32][33][34] While multi-ancestral adenomas and adenocarcinomas have been identified in both sporadic and familial cases of colorectal cancer in humans, previous studies did not address the fate of ancestral clones that carry mutations in key tumor driver genes such as KRAS, PIK3CA encoding PI3K, or TP53, which are commonly mutated in colorectal cancers. 15,35,36 Expression of a tumor driver gene within a single ancestral clone might result in a clonal sweep, eliminating other less fit clones that contribute to a tumor.…”