As much as that a disturbance of tissue homeostasis through dysregulated apoptosis is generally associated with carcinogenesis, gastric carcinogenesis after Helicobacter pylori infection could be the accumulated consequence of imbalances between apoptosis and proliferation. Since sonic hedgehog (Shh) has been reported to play versatile roles in various tumorigenesis, we hypothesized that late reactivation of sonic hedgehog by H. pylori infection results in population of gastric epithelial cells that are resistant to apoptosis. The Resistant Clones against H. pylori-induced Apoptosis (RCHA) were established and maintained up to 19th cell passages, during which the serial changes of Shh expression were measured. Apoptosis was measured in N-Shh over-expressed stable cell lines and compared with parent cell line after either infected with H. pylori or treated with cyclopamine. For clinical relevance, the expressions of Shh were compared in tissues from gastric adenoma or adenocarcinoma according to H. pylori infection. Longer passages of RCHA after H. pylori infection, the higher expressions of Shh, suggesting RCHA was associated with the reactivation of Shh. Significant decrement in subG1 phase of cell cycle and attenuated executions of apoptosis after H. pylori infection in cells of Shh overexpression, whereas either Shh siRNA or cyclopamine increased the H. pylori-induced cytotoxicity and significantly abrogated anti-apoptotic actions imposed by Shh. Significantly higher expressions of Shh were seen in H. pylori-associated gastric cancers than H. pylori-not associated gastric cancer. Late reactivation of sonic hedgehog by H. pylori infection results in population of gastric epithelial cells that are resistant to apoptosis and imposes proliferative changes under the background of atrophic gastritis, providing the carcinogenic basis.
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