AIM: To investigate the expression of effector protease receptor-1 (EPR-1), proliferative index ki-67 and apoptosis index in patients with primary advanced gastric adenocarcinoma and to clarify the significance of EPR-1expression and its correlationship with the proliferation and apoptosis indexes.METHODS: Using immunohistochemical staining andterminal deoxynucleotidyl transferase mediated nick end labelling (TUNEL) technique, we determined the expression of EPR-1, proliferative index (Ki-67) and apoptotic index (AI) in 120 paraffin-embedded specimens of primary advanced gastric adenocarcinoma as well as lymph node metastasis and adjacent normal tissues.RESULTS: EPR-1 expression was distributed in the cytoplasm of normal gastric mycoderma, carcinoma cells and smooth muscle cells. The positive rate of EPR-1 expression in the primary gastric adenocarcinomas, invasion tumor node and lymph node metastasis was 65.83%, 55.29%and 68%, respectively. While the positive rate in normal gastric mycoderma and smooth muscle cells was 46.7%and 53.3%, respectively. The average positive rate of kj-67in EPR-1-positive tumors was 7.00% which was significantly lower than that of 8.53% in EPR-1-negative tumors, but the average AI in EPR-1-positive tumors was 1.25%, which was significantly higher than that of 1.00% observed in EPR-1-negative tumors. On the other hand, the average positive labeling index for Ki-67 (ki-67) in EPR-1-positive lymph node metastasis was 7.65%, which was significantly lower than that of 9.44% observed in EPR-1-negative lymph node metastasis. However, the average AI in EPR-1-positive lymph node metastasis tumors was 0.99%, which was significantly higher than that of 0.67% observed in EPR-1-negative lymph node metastasis.CONCLUSION: The frequency of EPR-1 expression was significantly higher in primary gastric adenocarcinoma and in its lymph node metastasis than that in normal gastric mucosa. Expression of EPR-1 was significantly correlated with tumor histological subtypes and tumor differentiation.Weighted EPR-1 Score is positively correlated with apoptosis index, but is negatively related with proliferative index.Thus, Weighted EPR-1 Score and EPR-1 expression in gastric adenocarcinoma cells maybe a potential marker in clinical setting.