Objective: The objective of this study was to investigate the significance of the activated Akt-mammalian target of rapamycin (Akt-mTOR) signaling pathway in the progression of prostate cancer. Materials and Methods: The expression levels of Akt, phosphorylated Akt (p-Akt), mTOR and phosphorylated mTOR (p-mTOR) in 175 prostate specimens, including 61 normal prostate tissues as a control, 24 high-grade prostatic intraepithelial neoplasias (HGPINs) and 90 clinically localized prostate cancers, were evaluated by immunohistochemical staining. p-Akt and p-mTOR ratios, which were defined as the expression level of p-Akt in relation to that of Akt and the expression level of p-mTOR in relation to that of mTOR, respectively, in these specimens were calculated. Results: Expression levels of all four molecules, including Akt, p-Akt, mTOR and p-mTOR, were significantly greater in the HGPIN group compared with the normal control and prostate cancer groups. Furthermore, the p-Akt ratio in the prostate cancer group was significantly lower than that in the HGPIN group, while there was no significant difference in the p-mTOR ratio between the HGPIN and prostate cancer groups. In the prostate cancer group, no significant relationships were observed between major clinicopathological parameters and the expression levels as well as the ratios of p-Akt or p-mTOR. Conclusions: The Akt-mTOR signaling pathway may play a limited role in the progression of prostate cancer.

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