Expression of mTOR Signaling Pathway Molecules in Triple-Negative Breast Cancer.

Triple-negative breast cancer (TNBC), which lacks expression of estrogen receptor (ER), progesterone receptor (PgR), and epidermal growth factor receptor 2 (HER2), currently has no effective hormonal or molecular target therapy. To elucidate the role of the mammalian target of rapamycin (mTOR) signaling pathway in TNBC, the expression of molecules involved in mTOR signaling including mTOR, phosphorylated (p)-mTOR, p-4EBP1, GLUT1, GLUT3, HIF-1α, and Ki67 was investigated by immunohistochemistry in 35 TNBC and 81 non-TNBC cases. Expression of p-mTOR, the activated form of mTOR, but not unphosphorylated mTOR, was significantly higher in non-TNBC cases than in TNBC cases. Expression of p-4EBP1, GLUT1, and GLUT3 was higher in TNBC cases than in non-TNBC cases. When the localization of p-mTOR was classified as nuclear, perinuclear, or cytoplasmic, nuclear localization of p-mTOR was observed more frequently in TNBC than in non-TNBC cases and was correlated with the expression of GLUT1 and GLUT3, which was related to proliferation activity examined with Ki67. mTOR signaling regulates cell proliferation in some cases of TNBC and may be a potential target of molecular therapy for TNBC.

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© 2019 S. Karger AG, Basel.