Elevated phospho-S6 expression is associated with metastasis in adenocarcinoma of the lung.
OBJECTIVE
The primary objective of this study was to determine whether markers of differentiation and activation of the Akt pathway are associated with metastasis in adenocarcinoma of the lung.


METHODS
Paired primary and metastatic tumor samples were obtained from 41 patients who had undergone resection of both primary lung adenocarcinoma and brain metastatic lesions. Paired samples were compared for relative expression of thyroid transcription factor 1 (TTF-1) and E-cadherin as potential markers of differentiation. Activation of the Akt pathway was assessed by expression of p-Akt and p-S6. Biomarkers that showed relative discordance in expression between the matched pairs were then assessed in a cohort of 77 primary lung adenocarcinomas. Validation was done in an independent cohort of 82 primary lung adenocarcinomas.


RESULTS
Among the 41 matched pairs, E-cadherin (23 discordant pairs) and TTF-1 (18 discordant pairs) were overexpressed in primary tumors (20 of 23 and 15 of 18, respectively). In contrast, p-S6 overexpression was significantly associated with metastatic tumors (20 of 21 discordant pairs). The expression of E-cadherin, p-S6, and TTF-1 was evaluated in 77 primary lung adenocarcinomas, in which high p-S6 expression was associated with shorter time to metastasis. The association of p-S6 with metastasis was then validated in an independent set of 82 tumors. In multivariable analysis, p-S6 expression was a negative independent predictor of metastasis-free survival after adjustment for tumor stage.


CONCLUSIONS
The biomarker p-S6 is overexpressed in metastatic tumors. In primary tumors, higher p-S6 expression is associated with shorter metastatic-free survival. This biomarker has the potential for risk stratification in future clinical trials.
McDonald
J Matthew
JM
Department of Pathology, The University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030, USA.
Pelloski
Christopher E
CE
Ledoux
Alicia
A
Sun
Menghong
M
Raso
Gabriela
G
Komaki
Ritsuko
R
Wistuba
Ignacio I
II
Bekele
B Nebiyou
BN
Aldape
Ken
K
D000230:Adenocarcinoma / Q000378:metabolism / Q000473:pathology*; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D014408:Biomarkers, Tumor / Q000032:analysis*; D001932:Brain Neoplasms / Q000378:metabolism / Q000556:secondary*; D015820:Cadherins / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D005260:Female; D006801:Humans; D053208:Kaplan-Meier Estimate; D008175:Lung Neoplasms / Q000378:metabolism / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D009361:Neoplasm Invasiveness / Q000473:pathology; D010766:Phosphorylation; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D012269:Ribosomal Proteins / Q000378:metabolism*; D014157:Transcription Factors
D014408:Biomarkers, Tumor; D015820:Cadherins; D004268:DNA-Binding Proteins; D012269:Ribosomal Proteins; C504003:TTF1 protein, human; D014157:Transcription Factors; D051057:Proto-Oncogene Proteins c-akt