Persisting and Increasing Neutrophil Infiltration Associates with Gastric Carcinogenesis and E-cadherin Downregulation

H. pylori-induced chronic inflammation is considered the most important cause of gastric cancer. The actual process how chronic inflammation triggers gastric carcinogenesis is still not clear. In this study, neutrophils and relative markers in gastric cancer development were examined with immunohistochemistry and fluorescence RNA in situ hybridization methods. On average, 24 times more neutrophils were found in gastric cancer tissues and about 9 times more neutrophils were found in gastric intestinal metaplasia tissues comparing to normal gastric tissue controls. CagA(+) H. pylori infection in cancer adjacent tissues or EBV infection in cancer tissues did not increase neutrophil infiltration into gastric cancer tissues significantly. Neutrophil density was positively correlated with cell proliferation while negatively correlated with E-cadherin intensity. E-cadherin is also transcriptionally downregulated in gastric cancer tissues comparing to adjacent tissue controls. The increased neutrophils in the gastric cancer tissues appear to be related to increased chemoattractant IL-8 levels. In gastric cancers, neutrophil numbers were higher comparing to cancer adjacent tissues and not associated with patient ages, tumor invasion depth, tumor staging, metastasis or cancer types. The conclusion is that persisting and increasing neutrophil infiltration is associated with E-cadherin downregulation, cell proliferation and gastric carcinogenesis.