To investigate the expression of early growth response 1 (EGR1) in gastroenterological cancers and its significance in the pathogenesis.RT-PCR was used to determine the expression of EGR1 in normal gastric mucosa tissues from 20 non-tumor patients, gastroenterological tumor tissues and matched para-cancer tissues normal morphologically. RT-PCR and Western blotting were used to analyze the mRNA and protein expression of EGR1 in 20 cancer cell lines. Immunohistochemistry (IHC) was preformed to measure the expression level of EGR1 protein on tissue microarray including 179 tumors and 159 normal tissues.EGR1 was overexpressed in gastric cancer (GC) and its matched adjacent normal tissue (ANT), but not expressed or expressed at a low level in the normal gastric mucosa from the non-tumor patients, which was consistent with the GC gene expression profiling data. Overexpression of EGR1 was seen in the 20 cancer cell lines at both mRNA and protein levels. IHC showed strong positive staining of EGR1 protein in the cytoplasm of both tumor tissues and matched normal tissues and showed negative or weaker nuclear staining in the normal gastric mucosa tissues from non-tumor patients. Overexpression of EGR1 was detected in 87% (49/56) of the GC tissues and 79% (43/54) of their ANTs; 83% (43/52) of the hepatocellular carcinoma tissues and 79% (32/42) of their ANTs; 78% (41/52) of colorectal cancer tissues and 63% (22/35) of their ANTs; and 79% (15/19) of the squamous cell carcinoma tissues and 78% (14/18) of their ANTs.EGR1 may be correlated with the abnormal proliferation of cells at the early stage of malignant transformation.
