Abstract:Objective To investigate the effect of X-prolyl aminopeptidase P2 (XPNPEP2) level on the long-term prognosis of patients with breast cancer. Methods The pathological specimens of breast cancer tissues and paracancerous tissues and the clinicopathological data were collected from 93 patients with breast cancer undergoing surgical treatment from January 2013 to June 2015. The expressions of XPNPEP2 were detected by immunohistochemistry and compared between breast cancer tissues and adjacent tissues, analyze the relationship between the expression of XPNPEP2 and the pathological parameters of breast cancer. The 5 year- survival rate associated with different XPNPEP2 expression levels was compared. The relationship between prognosis of breast cancer and expression of XPNPEP2 was analyzed by COX multivariate proportional hazards regression. Results The positive expression rate of XPNPEP2 in breast cancer tissues was significantly higher than that in adjacent tissues (72.73% vs 26.14%， χ²=38.209，P＜0.01). The positive expressions of XPNPEP2 were significantly related with the tumor differentiation, lymph node metastasis and TNM stages in breast cancer tissues(P＜0.05,P＜0.01). The 5-year overall survival rate of patients with XPNPEP2 positive expression was significantly lower than that of patients with XPNPEP2 negative expression(35.94% vs 79.17%， χ²=13.074，P＜0.01）. COX regression analysis showed that high XPNPEP2 expression (HR=3.476, 95%CI=1.531-7.892,P<0.01), poor tumor differentiation (HR=2.903, 95%CI=1.357-6.210,P<0.01), lymph node metastasis (HR=3.415, 95%CI=1.167-9.992,P<0.05) and high TNM stage (HR=2.767, 95%CI=1.125-6.803,P<0.05) were the independent risk factors affecting the prognosis of breast cancer patients. Conclusion The positive expression of XPNPEP2 is associated with a variety of pathological parameters and poor prognosis and is expected to be a potential marker for prognosis evaluation in breast cancer patients.