Enhanced nuclear Y-box binding protein-1 expression predicts poor prognosis in close association with mammalian target of rapamycin expression in endometrial cancer

Abstract

Abstract Background Enhanced expression of oncogenic Y-box binding protein-1 (YB-1) predicts prognostic outcomes in patients with various human malignancies, including ovarian cancer, in close association with aberrant expression of genes involved cell proliferation, survival, and resistance to anti-cancer therapy. We examined whether YB-1 could predict the prognostic outcomes of patients with endometrial cancer and whether enhanced YB-1 expression affects the expression of mammalian target of rapamycin (mTOR), a key effector of the phosphatidylinositol-3 kinase (PI3K)/protein kinase B (AKT)/mTOR pathway, in endometrial cancer. Methods We examined expression levels of YB-1 and mTOR in tumor samples of 166 patients with endometrial cancer who underwent surgery at our hospital, including those with endometrioid grade 1–3 tumors, serous carcinoma, and stage I-IV disease. Expression levels of YB-1 and mTOR were assessed by immunohistochemical analysis. The correlation between expression levels of YB-1 or mTOR and prognosis was confirmed by biostatistical analysis. Results The positivity rate of nuclear YB-1 expression was 9.4%. YB-1 expression was significantly associated with poor progression-free survival (P = 0.012) and overall survival (P = 0.003). Among 166 tumors, 59 (35.5%) expressed mTOR. Nuclear YB-1 expression also correlated with mTOR expression (P = 0.006). We observed similar results when examining only patients who underwent adjuvant chemotherapy. Conclusions Enhanced nuclear YB-1 expression could predict poor outcomes in endometrial cancer, and was significantly closely associated with enhanced mTOR expression. Herein, we discuss whether activation of the PI3K/AKT/mTOR pathway through enhanced mTOR expression relates to enhanced YB-1 expression, thereby affecting the prognostic status of endometrial cancer.