Conversely, p-S6 correlated strongly not only with p-Erk1/2 (< 0.001) but also with p-mTOR (= 0.010), whereas p-Erk1/2 expression correlated weakly with p-mTOR (= 0.014), suggesting that Erk1/2 seems to regulate S6 through mTOR. It is striking that an association between p-AKT expression and p-Erk1/2 expression was not observed, although p-AKT and p-Erk1/2 strongly correlated with p-TSC2 and p-S6, which was shown to be an independent predictive factor in our study. 5.1%, 46.7%, 27.1%, and 16.6% of tumors, respectively. The phenotype of p-eIF4E correlated positively with that of p-AKT, p-TSC2, and p-S6 (< 0.001). Overall survival in NSCLC patients was significantly shorter in cases with overexpression of p-eIF4E and p-AKT alone and in combination (log-rank < 0.001, each). Cases with underexpression of PTEN were limited (6.4%), and this phenotype did not correlate with any clinical variable. In cluster analysis, the p-AKT/p-mTOR/p-eIF4E/p-S6Cpositive group experienced significantly shorter survival compared with the survival of all cases (< 0.001). Multivariate analysis showed that p-eIF4E overexpression is an impartial prognostic factor for NSCLC (= 0.004). Conclusions: This study shows that D-69491 p-eIF4E expression in addition to p-AKT predicts poor prognosis in NSCLC. Moreover, the correlation between expression of p-eIF4E with p-AKT, as well as p-TSC2 and p-S6, indicates that eIF4E activation through the AKT pathway plays an important role in the progression of NSCLC. Lung malignancy remains the leading cause of cancer-related deaths in the world; the overall 5-year survival is only 16% (1). More than 75% to 85% of lung cancers are nonCsmall cell lung carcinoma (NSCLC) at diagnosis (2). The AKT pathway regulates many diverse biological functions. It is activated by tyrosine kinase receptor growth factors, such as the epidermal growth factor receptor, that lead to the generation of membrane-bound phosphoinositides, which then recruit and phophorylate AKT (3-5). Phosphorylated AKT results in gain or loss of function of its downstream proteins and contributes to cell proliferation, cell survival, cell size, and response to nutrient availability (3-5). The deregulation of these proteins promotes tumorigenesis in many cancers (3-5). Investigators have recently reported frequent activation of AKT kinases in a variety of tumor types, such as brain, breast, prostate, and endometrium (6-10). They also point out that this investigation of this pathway is critical because its numerous proteins provide attractive targets for therapy, and several inhibitors are being developed and tested in early clinical trials (4, 11, 12). The mammalian target of rapamycin (mTOR) has been proposed to play a central role in tumor progression in the downstream D-69491 signaling of the AKT pathway (13-15). mTOR has also Rabbit Polyclonal to C1R (H chain, Cleaved-Arg463) been recognized as a promising therapeutic target because its activation can be inhibited by rapamycin or its homologue (4, 12). However, the status of mTOR and its relationship with the proteins of the AKT pathway in lung malignancy are still unclear (16-18). It is known that mTOR can D-69491 be activated directly by phosphorylated AKT or indirectly through the tuberous sclerosis complex, which consists of hamartin (TSC1) and tuberin (TSC2; refs. 13, 14). Few reports describe that the loss of heterogeneity of either TSC1 or TSC2, whose gene mutations are responsible for the multiorgan syndrome lymphoangioleiomyomatosis, can be found in atypical adenomatous hyperplasia and adenocarcinoma of lung (19, 20). Little is known about the status of TSC1 or TSC2 in NSCLC and their associations with AKT and mTOR. Two major signaling pathways downstream of mTOR are the ribosomal S6 kinase and the 4E-binding protein 4EBP-1, both of which have been implicated in control of protein translation (21). The phosphorylation of 4EBP-1 by mTOR results in the release of a cap-binding protein eukaryotic translation initiation factor complex 4E (eIF4E), which is usually held inactive when bound to the hypophosphorylated 4EBP-1 complex (14, 15, 22). It is reported that many transformed cell lines express higher levels of eIF4E (23), and a variety of human cancers, such as breast, bladder, colorectum, uterine cervix, non-Hodgkin lymphoma, and head and neck cancers, overexpress eIF4E (24). Although overexpression.