674 Concomitant Knockout of M1 Muscarinic Receptors (CHRM1) in Azoxymethane-Treated Chrm3−/− Mice Nullifies Reductions in Colon Tumor Number and Size

G A A b st ra ct s (HP). Animals were analyzed 3 and 12 months after inoculation. Morphology of the fundus was examined in sections stained with H&E. Expression of MIP-2, TNF-alfa, INF-gamma, DCAMKL1, villin, activation-induced cytidine deaminase (AID), TFF2 and COX-2 genes were measured by QRT-PCR. Distribution of parietaland DCAMKL1-positive cells was analyzed immunohistochemistry. Western blots were used to assess the phosphorylation of Smad1-5-8 and STAT3. RESULTS: The mucosa of the TG-mice exhibited decreased phosphorylation of Smad1-5-8, confirming inhibition of BMP signaling. Histological analysis showed increased height, dilated glands, decreased parietal cell number and amodest increase in inflammatory cells. The TG-mice also exhibited a 2to 3-fold increase in the expression of the inflammatory genes MIP-2, INF-gamma TNF-alfa, and COX-2. Inhibition of BMP signaling led to increased expression of the gastric progenitor cell (GPC) markers DCAMKL1 and villin, and of AID and TFF2, molecules associated with gastric carcinogenesis. Infection of the TG-mice with HP, led to a dramatic increase in inflammation, characterized by enhanced cytokine gene expression and by a robust influx of inflammatory cells. HP-infected non-TG mice exhibited inflammatory changes that were less severe then those seen in the infected TG-animals. Intraepithelial neoplasia was seen in TG-mice infected for 12 months but not in age matched, non-infected TG-mice, or HP-infected non-TG-mice. HP infection also led to enhanced expression of AID, TFF2, villin and DCAMKL1 and to the phosphorylation and activation of the oncogenic molecule STAT3. CONCLUSIONS: Loss of gastric BMP signaling leads to a pro-inflammatory state, resulting in extreme responses and accelerated development of intraepithelial neoplasia with HP infection, suggesting that BMPs normally temper gastric inflammatory responses. Low BMP signaling and heightened inflammation stimulate GPCs, including increased marker expression and cell number. Thus BMPs play an important role in modulating inflammatory responses in the development of gastric cancer.