Abstract: Objective To explore the combined detection of bromodomain protein 4(BRD4), mitochondrial single-stranded DNA binding protein(SSBP1) and proto-cadherin 17(PCDH17) in the diagnosis of early gastric cancer. 
Methods We collected 50 cases of gastric cancer tissues, 50 cases of precancerous tissues, and 50 cases of normal gastric mucosa tissues. The expression of BRD4, SSBP1 and PCDH17 proteins in tissue specimens was determined by immunohistochemical staining, followed by analysis in different tissue samples. The three groups of blood samples were collected to detect related serum indicators in the three groups. Receiver operating characteristic(ROC) curve was used to analyze the value of BRD4, SSBP1 and PCDH17 in the diagnosis of gastric cancer. 
Results BRD4 and SSBP1 were highly expressed in gastric cancer tissues, while PCDH17 was poorly expressed. Comparison of the positive rates of BRD4, SSBP1 and PCDH17 in the three groups of tissue samples was statistically significant(P＜0.05). The serum carbohydrate antigen(CA199), pepsinogen(PG)Ⅰ, PGⅡ, gastrin-17(G-17) levels and positive rate of helicobacter pylori(HP) in the three groups were significantly different(P＜0.05). The serum CA199, PGⅠ, G-17 levels and HP positive rate of patients in gastric cancer tissue group were significantly higher than those in precancerous tissue group and normal gastric mucosal tissue group, while PGⅡ level was lower than that that in precancerous tissue group and normal gastric mucosal tissue group(P＜0.05). The positive rates of BRD4, SSBP1 and PCDH17 in gastric cancer tissues of patients with clinical stage Ⅲ to Ⅳ and lymph node metastasis were significantly different(P＜0.05). The sensitivity and specificity of combined detection of BRD4+SSBP1+PCDH17 were higher than an indicator alone. 
Conclusion Combined detection of BRD4, SSBP1 and PCDH17 is conductive to the differential diagnosis of gastric cancer.

Key words: stomach neoplasms, early diagnosis,  , bromodomain protein 4