AIM:Overexpression of tumor protein p53-inducednuclear protein 1(TP53INP1)induces G_1 cell cycle arrestand increases p53-mediated apoptosis.To clarify theclinical importance of TP53INP1,we analyzed TP53INP1and p53 expression in gastric cancer.METHODS:TP53INP1 and p53 expression wereexamined using immunohistochemistry in 142 casesof gastric cancer.The apoptosis of gastric cancercells was analyzed using the TUNEL method.Therelationship between the expression of TP53INP1 andclinicopathological factors was statistically analyzed.RESULTS:TP53INP1 was expressed in 98%(139/142cases)of non-cancerous gastric tissues and was down-expressed in 64%(91/142 cases)of gastric cancerlesions from the same patients.TP53INP1 expressionwas significantly decreased(43.9%)in poorlydifferentiated adenocarcinoma compared with well ormoderately differentiated adenocarcinoma(81.6%).Cancers invading the submucosa or deeper showedlower positively(59.1%)compared with mucosal cancers(85.2%).Decrease or loss of TP53INP1 expression wassignificantly correlated with lymphatic invasion(54.3%vs 82.0% without lymphatic invasion)and node-positivepatients(31.3% vs 68.3% in node-negative patients).P53 was expressed in 68(47.9%)patients of gastriccancer,whereas it was absent in normal gastric tissues.A significant association was also observed betweenTP53INP1 status and the level of apoptosis in tumorcells:the apoptotic index in TP53INP1-positive tissueswas significantly higher than that in TP53INP1-negativeportions.Finally,when survival data were analyzed,loss of TP53INP1 expression had a significant effect inpredicting a poor prognosis(P=0.0006). CONCLUSION:TP53INP1-positive rate decreases withthe progression of gastric cancer.TP53INP1 proteinnegativity is significantly associated with aggressivepathological phenotypes of gastric cancer.TP53INP1is related to the apoptosis of gastric cancer cells.Thedecreased expression of the TP53INP1 protein mayreflect the malignant grade of gastric cancer and isregarded as an adverse prognostic factor. AIM: Overexpression of tumor protein p53-induced nucleoprotein 1 (TP53INP1) induces G_1 cell cycle arrest and increases in p53-mediated apoptosis. Clarifying the clinical importance of TP53INP1, we analyzed TP53INP1 and p53 expression in gastric cancer. METHODS: TP53INP1 and p53 expression wereexamined using immunohistochemistry in 142 cases of gastric cancer. The apoptosis of gastric cancer cells was analyzed using the TUNEL method. Therelationship between the expression of TP53INP1 and clinicopathological factors was analyzed by PCRRESULTS: TP53INP1 was expressed in 98% (139 / 142cases) of non-cancerous gastric tissues and was down-expressed in 64% (91/142 cases) of gastric cancerlesions from the same patients. TP53INP1 expressionwas significantly decreased (43.9%) in poorly differentiated adenocarcinoma compared with well ormoderately differentiated adenocarcinoma (81.6%). Cancers invading the submucosa or deeper showedlower positively (59.1%) compared with mucosal cancers (85.2%). Decrease or loss of TP53IN P1 expression was statistically correlated with lymphatic invasion (54.3% vs 82.0% without lymphatic invasion) and node-positive patients (31.3% vs 68.3% in node-negative patients) .P53 was expressed in 68 (47.9%) patients of gastriccancer, absent in normal gastric tissues. A significant association was also observed betweenTP53INP1 status and the level of apoptosis in tumor cells: the apoptotic index in TP53INP1-positive tissues was significantly higher than that in TP53INP1-negativeportions. Finaally, when survival data were analyzed, loss of TP53INP1 CONCLUSION: TP53 INP1-positive rate decreases with the progression of gastric cancer. TP53 INP1 proteinnegativity is significantly associated with aggressivepathological phenotypes of gastric cancer. TP53 INP1 is related to the apoptosis of gastric cancer cells. Thedecreased expression of the TP53INP1 protein mayreflect the malignant grade of gastric cancer and isregardedas an adverse prognostic factor