Objective To investigate the expression of pseudokinase Tribbles homology 3(TRIB3)and its clinical prognostic value in Siewert type Ⅱ adenocarcinoma of esophagogastric junction(AEG).Methods Western blot and immunohistochemical method were used to detect the expression of TRIB3 in R0 resected Siewert type Ⅱ AEG and its corresponding adjacent tissues,and analyze its rela-tionship with clinical parameters,survival and prognosis.Results Western blot analysis showed that the expression level of TRIB3 in Siewert type Ⅱ AEG tissues was significantly lower than that in the adjacent tissues(P<0.05).The immunohistochemical Results showed that the positive expression rate of TRIB3 in cancer tissues was significantly lower than that in adjacent tissues(P<0.01).The expression of TRIB3 was significantly correlated with the degree of differentiation,clinical TNM stage and lymph node metastasis(P<0.05),but not with age,gender and pathological morphology(P>0.05).Kaplan-Meier survival analysis showed that the long-term survival of patients with positive TRIB3 expression was significantly better than that of patients with negative TRIB3 expression(P<0.01).Univariate(HR =0.290,95%CI:0.110-0.761,P =0.012)and multivariate(HR =0.179,95%CI:0.051-0.630,P = 0.007)COX regression analysis showed that TRIB3 could be used as an independent prognostic factor for patients with Siewert type ⅡAEG(P<0.05).Conclusion TRIB3 may be involved in the occurrence and development of Siewert typeⅡ AEG.It is expected to be-come a new target for early diagnosis and treatment of AEG,and can be used as an important indicator for judging the prognosis of patients.