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The mammalian target of rapamycin (mTOR) signaling pathway has emerged as a major effector of cell growth and proliferation, and is an attractive target for cancer therapy. However, the association between mTOR pathway and the malignancy grade of human gliomas has not been thoroughly investigated. Tumor tissues from 87 Chinese patients (49 males, average age of 51.7 ± 13.0 years, range 15-78) with glioma were prospectively collected. The expression of three key proteins of the mTOR pathway, pAKT, pmTOR and p-p70S6 kinase (p-p70S6K) was measured by semi-quantitative immunohistochemical techniques. Grade I-II, III and IV glioma was pathologically identified in 27 (31.0%), 24 (27.6%) and 36 (41.4%) patients, respectively. Of the 87 patients, pAKT, pmTOR and p-p70S6K were found in 63 (72.4%), 65 (74.7%), and 63 (72.4%) patients, respectively. The expression of all three pAKT, pmTOR and p-p70S6K proteins was found in 42 (48.3%) patients, while only one or two of the three proteins were found in the remaining patients (51.7%). The percentage of patients with very strong expression of pAKT, pmTOR and p-p70S6K in grade IV glioma was 13 (36.1%), 16 (44.4%) and 15 (41.7%), respectively, which was greater than in grade I or II tumors (0-3.7%, P < 0.01). In conclusion, expression of mTOR pathway proteins pAKT, pmTOR and p-p70S6K can be found in human glioma of all malignancy grades. However, higher levels of these proteins were associated with advanced malignancy grades of the tumor.

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