Background The role of epigenetics in gene expression regulation and development significantly enhances our understanding of carcinogenesis.All the tumor related genes may be the target of epigenetical or genetic regulation.We selected some epigenetically regulated genes for cDNA array analysis and observed variability in the expression of the DICER1 gene in distinct stages of gastric cancer.The aim of this study was to assess the correlation between the expression of DICER1,an epigenetically regulated gene,and gastric cancer.Methods To detect the expression of 506 tumor-associated genes,including DICER1,in the matched cancerous mucosa,pre-malignant lesion (adjacent mucosa),non-cancerous gastric mucosa and distant lymphocyte metastatic lesion in 3 cases of gastric cancers using cDNA array.DICER1 mRNA expression and DICER1 protein expression were further analyzed by Real-time PCR and Western blot in 32 cases of progressive gastric cancer.DICER1 protein expression was also detected in 33 early and 30 progressive gastric cancers by the immunohistochemistry (IHC) method.Results In 3 cases of gastric cancer cDNA array showed dramatically decreased expression of DICER1 in pre-malignant Iesion,cancerous mucosa and distant lymphocyte metastatic lesions compared with matched noncancerous gastric mucosa,pre-malignant lesion and cancerous mucosa.Real-time PCR results showed that the expression level of DICER1 mRNA in gastric cancer was significantly down-regulated compared to normal gastric tissue (P