Identification of S664 TSC2 phosphorylation as a marker for extracellular signal-regulated kinase mediated mTOR activation in tuberous sclerosis and human cancer.
Constitutive activation of extracellular signal-regulated kinases (Erk1/2) is frequently implicated in human cancers. Recently, aberrantly activated Erk was also found in brain lesions associated with tuberous sclerosis (TSC). We reported previously that Erk might contribute to tumorigenesis by phosphorylating TSC2 at specific residues, particularly S664. In our present study, 25 TSC-related cortical tubers or subependymal giant cell astrocytomas, as well as tissue microarrays of six types of human cancers, were analyzed for the expression of phospho-Erk (pErk) 1/2, S664-phospho-TSC2 (pTSC2), and phospho-S6 (pS6) by immunohistochemistry. We found that Erk-mediated TSC2 phosphorylation occurred at a high incidence and positively correlated with mitogen-activated protein kinase (MAPK) and mammalian target of rapamycin (mTOR) activation in TSC-associated brain lesions as well as in various cancers. Interestingly, in certain types of cancers (e.g., breast carcinoma and colon carcinoma), S664-pTSC2 seemed to be a more sensitive marker than pErk. Furthermore, most of the pTSC2-positive samples ( approximately 75%) were positive for pS6, but only 40% to 55% of the pS6-positive tumors exhibited TSC2 phosphorylation. Our results show that S664 TSC2 phosphorylation is a marker for Erk-mediated (as opposed to Akt-mediated) mTOR activation in TSC and human cancer. On the basis of these findings, TSC2 phosphorylation at S664 can be used to identify patients that may benefit from antitumor therapy with MAPK and mTOR inhibitors. Importantly, our results indicate that Erk-mediated phosphorylation and inactivation of TSC2 can be critical in development of hamartomatous lesions in TSC and cancer pathogenesis.
Ma
Li
L
Cancer Biology and Genetics Program, Sloan-Kettering Institute, Memorial Sloan-Kettering Cancer Center, New York, NY 10021, USA.
Teruya-Feldstein
Julie
J
Bonner
Pauline
P
Bernardi
Rosa
R
Franz
David Neal
DN
Witte
David
D
Cordon-Cardo
Carlos
C
Pandolfi
Pier Paolo
PP
D002478:Cells, Cultured; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D006801:Humans; D015151:Immunoblotting; D047468:Immunoprecipitation; D007668:Kidney / Q000166:cytology; D020935:MAP Kinase Signaling System / Q000502:physiology*; D009369:Neoplasms / Q000209:etiology / Q000378:metabolism* / Q000473:pathology; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism*; D012694:Serine / Q000378:metabolism; D058570:TOR Serine-Threonine Kinases; D046888:Tissue Array Analysis; D014162:Transfection; D014402:Tuberous Sclerosis / Q000209:etiology / Q000378:metabolism* / Q000473:pathology; D000077005:Tuberous Sclerosis Complex 2 Protein; D025521:Tumor Suppressor Proteins / Q000378:metabolism*
C000624653:TSC2 protein, human; D000077005:Tuberous Sclerosis Complex 2 Protein; D025521:Tumor Suppressor Proteins; D012694:Serine; D011494:Protein Kinases; C546842:MTOR protein, human; D058570:TOR Serine-Threonine Kinases; D048049:Extracellular Signal-Regulated MAP Kinases