OBJECTIVE To evaluate the REGy expression in gastric cancer tissue and gastric cancer cell lines of various differentiation levels and its clinical significance.METHODS Immunohistochemistry was used to detect the expression of REGy protein in 70 specimens of gastric cancer and 30 specimens of normal gastric mucosa. The relationship between the expression of REGy protein and the biological behaviors of gastric cancer was analyzed. RT-PCR and West blot were used to detect the mRNA level and the protein expression of REGγ in normal gastric cell line GES-1, well differentiated gastric cancer cell line MKN-28, moderately differentiated gastric cancer cell line SGC-7901 and poorly differentiated gastric cancer cell line BGC-823.RESULTS The expression rate of REGγprotein in gastric cancer tissue (52/70, 74.29%) was significantly higher than that in normal gastric tissue (12/30, 40%) (P<0.01). The expression rate of REGywas correlated with tumor size (P<0.01), lymph node metastasis (P<0.05), differentiation degree (P<0.01), infiltration depth (P<0.01)and distant metastasis (P<0.05). RT-PCR analysis showed that theexpression of REGγ mRNA was 0.459±0.079 in the normal gastric mucosa cell line, 0.588±0.118 in the well differentiated gastric cancer cell line, 0.715±0.066 in the moderately differentiated gastric cancer cell line, and 0.873±0.099 in the poorly differentiated gastric cancer cell line, showing a negative correla- tion between REGγmRNA expression and differentiation level (P <0.05). West blot analysis showed that the expression of REGy protein was 0.712±0.065 in the normal gastric mucosa cell line, 1.176±0.185 in the well differentiated gastric cancer cell line, 1.533 ±0.127 in the moderately differentiated gastric cancer cell line, and 2.061±0.398 in the poorly differentiated gastric cancer cell line, showing a negative correlation between REGγprotein expression and differentiation level (P<0.05).CONCLUSION REGγ is expressed in gastric cancer tissue and normal gastric tissue. In gastric cancer tissues, REGγexpression is positively correlated with the tumor size, lymph node metastasis,differentiation degree, infiltration depth and distant metastasis. Detecting the expression of REGy mRNA and protein is helpful for early diagnosis and predicting prognosis of gastric cancer.