Expression and activity of mTOR and its substrates in different cell cycle phases and in oral squamous cell carcinomas of different malignant grade.
In order to study the relationship between mTOR (mammalian target of rapamycin) and tumorigenesis, we investigated the expression and activity of mTOR, and its substrates, alpha1, alpha2, beta1 and beta2 isoforms of p70S6 kinase (p70S6K) and eukaryotic initiation factor 4E binding protein-1 (4EBP-1) in oral squamous carcinoma and Hela cells using RT-PCR, immunohistochemistry, statistical analysis and Western blotting. The result of Western blots showed that in poorly differentiated oral squamous carcinoma, the expression level of mTOR and p70S6k increased in M phase, while that of 4EBP-1 decreased. The results of RT-PCR and immunohistochemistry assay are the same as that of Western blot. In Hela cells, the RT-PCR results showed that the level of mTOR mRNA did not change during the cell cycle. In M phase, the expression of alpha1, alpha2, beta1 and beta2 isoforms of p70S6K increased noticeably, while the expression of 4EBP-1 decreased. The immunoblot results in Hela cells were consistent with the RT-PCR results. Furthermore, the activity assays in Hela cells suggested that,in phase G2 and M, the activity of mTOR was maintained at a higher level than in any other phase, while 4EBP-1 decreased in phase M. These results may help in further investigations of the important role of mTOR in cell cycle and tumorigenesis.
Liu
Yi
Y
Orthodontic Department of Dentistry College, China Medical University, Shenyang 110001, People's Republic of China.
Hidayat
Sujuta
S
Su
Wen-hui
WH
Deng
Xin
X
Yu
Da-hai
DH
Yu
Bing-zhi
BZ
D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism*; D002294:Carcinoma, Squamous Cell / Q000235:genetics / Q000378:metabolism* / Q000473:pathology*; D002453:Cell Cycle; D018797:Cell Cycle Proteins; D015870:Gene Expression; D015972:Gene Expression Regulation, Neoplastic; D006367:HeLa Cells; D006801:Humans; D007150:Immunohistochemistry; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D009062:Mouth Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology*; D009367:Neoplasm Staging; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism*; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics; D038762:Ribosomal Protein S6 Kinases, 70-kDa / Q000235:genetics / Q000378:metabolism*; D013379:Substrate Specificity; D058570:TOR Serine-Threonine Kinases
D048868:Adaptor Proteins, Signal Transducing; D018797:Cell Cycle Proteins; C087000:EIF4EBP1 protein, human; D007527:Isoenzymes; D010750:Phosphoproteins; D012333:RNA, Messenger; D011494:Protein Kinases; C546842:MTOR protein, human; D038762:Ribosomal Protein S6 Kinases, 70-kDa; D058570:TOR Serine-Threonine Kinases