58 Bone Marrow Derived Lin-Cd44hisca1-Ckit+CD34- Can Give Rise to Mesenchymal Stem Cells and Delay Progression to Dysplasia in a Murine Helicobacter Model of Gastric Cancer

Abstract

G A A b st ra ct s by ELISA. The colon cancer cell line MC38 was used for wound healing and cell proliferation assays using MSC conditioned (50% MSC / 50% with fresh) or control (50% MC38/ 50% fresh) media, examined at intervals in triplicate. For In Vivo studies, 8 week old APC min mice were injected intravenously with 5 million RFP-MSC. At four weeks, small intestine and colons were removed, adenomas enumerated, examined by direct fluorescent microscopy and standard H&E. RESULTS: WT mice receiving sham injections or RFP-MSC did not develop tumors. APC min mice receiving sham injection did not develop colon tumors. APC mice receiving MSCs developed 3 colonic tumors (n=4 each group). One mouse had one tumor, one had 2 tumors and 2 mice did not have any tumors. There was no statistical difference between small bowel adenomas in the APC min mice +/-MSC. Tumors were adenomas, and adenocarcinoma. Colonic epithelium was host derived, with CD44+, alpha smooth muscle actin + RFP-MSC incorporated into the stroma as myofibroblasts. MSC conditioned media contains TNF-alpha (216+/-48 pg/ml), MCP-1 (153+/-75pg/ml), CCL-5 (12804+/-9750pg/mml, IL6(3971+/-98 pg/ml) and undetectable levels of IFN, IL2, IL4 or IL10. Conditioned media increased proliferation of MC38 monolayers at all time points and increased monolayer wound healing compared to control media at 18 and 21 hours. Addition of anti-TNF antibody decreased proliferation and wound healing to control levels stressing the importance of this cytokine. Conclusion: Culture derived MSC migrate to at-risk tissue and initiate colon neoplasia by incorporating into stroma. MSCs produce factors (such as TNF-alpha) that provide colon adenocarcinoma cells (MC38) with migration and growth advantage. A model in which we can manipulate stromal-tumor interactions will be useful for identifying new targets for colon cancer prevention and therapy.