Contribution of Bone Marrow Derived Cells to Four Mouse Models of Gastrointestinal Tumourigenesis.

Abstract

Introduction: Houghton and colleagues (2004) demonstrated bone marrow derived cells (BMDCs) to be the origin of epithelial cells in pre-­‐‑invasive and malignant gastric tumours in Helicobacter felis infected mice. However, this has yet to be replicated in any other experimental scenario. Methods: To clarify the significance of Houghton’s observation we examined four mouse models of gastrointestinal tumourigenesis: the Tff1-­‐‑/-­‐‑ mouse model of inflammatory gastric adenocarcinoma, the ApcMin/+ and Apc1322T mouse models of familial adenomatous polyposis, and the Il10-­‐‑/-­‐‑ mouse model of colitis-­‐‑ associated colorectal adenocarcinoma, employing sex-­‐‑mismatched bone marrow (BM) transplantation (male BM to female recipients) followed by the identification of BMDCs in tissues using Y-­‐‑chromosome in situ hybridisation (ISH) detection and immunohistochemical phenotyping of cells. To investigate the mechanism for BMDC recruitment into tissues, osteopontin (Opn) mRNA isotopic ISH was employed. Results: In four mouse models there was not a single instance of a gastric gland or intestinal crypt with a patch of clonal Y-­‐‑chromosome positive (Y+) cells. Y+ cells in the epithelium were very rare and were mostly positive for several markers of immune cells. In contrast, Y+ cells were frequently observed in the stroma. Quantification of BMD-­‐‑myofibroblasts demonstrated increased recruitment into larger Apc1322T mouse tumours and desmoplastic reaction sites in Tff1-­‐‑/-­‐‑ mouse tumours, but not into inflamed non-­‐‑fibrotic tissues. Similarly, Opn mRNA expression was unaffected by inflammation but increased with tumour burden and in desmoplastic reaction sites. In the desmoplastic reaction sites of Tff1-­‐‑/-­‐‑ mouse tumours, increased osteopontin mRNA expression correlated with increased BMD-­‐‑myofibroblasts, therefore suggesting some chemoattraction was occurring. Conclusions: In four mouse models of gastrointestinal tumourigenesis BMDCs were not a source of reparative, pre-­‐‑cancerous, or malignant epithelial cells. Analysis of BM contribution in the stroma demonstrated that BMD-­‐‑ myofibroblast engraftment is driven by increased tumour burden and fibrosis. In addition, the increased presence of BMD-­‐‑myofibroblasts at desmoplastic reaction sites of Tff1-­‐‑/-­‐‑ mouse tumours correlated with increased Opn mRNA expression, indicating that osteopontin may act as chemoattractant in desmoplasia.