Adenocarcinomas are a very heterogeneous subgroup of
lung cancers, in which
oncogenesis is linked to different molecular events. Recent evidence suggests that the hormonal status may contribute to the pathogenesis of
lung adenocarcinoma.
TRAP220 is the main subunit of the TRAP/
Mediator complex and it binds to
nuclear hormone receptors in the presence of their cognate
ligand, as a cofactor of the transcription machinery. Since
TRAP220 is an essential coactivator that interacts directly with
estrogen receptor β (ERβ), we examined the expression of
TRAP220 protein to investigate its role in
lung adenocarcinoma, with particular attention being paid to its different histologic subtypes and the ERβ expression. We performed immunohistochemical detection of
TRAP220 and ERβ
protein in eighty-seven tissue samples from
lung adenocarcinoma patients by using a tissue microarray, and Western blotting was then done to confirm the immunohistochemical observations.
TRAP220 immunoreactivity was observed in 27 (31.0%) of the 87
adenocarcinoma cases. Analysis of the
TRAP220 expression by Western blotting confirmed the immunohistochemical results. The
TRAP220 expression was more frequently positive in the non-solid subtypes (bronchioloalveolar, acinar, and papillary patterns) than that in the solid subtype (P=0.027) and the
TRAP220 expression was more frequently positive in the well-differentiated
adenocarcinomas than that in the moderately or poorly differentiated
adenocarcinomas (P=0.005). The
tumors with a negative
TRAP220 expression were larger in size (P=0.048) and they more frequently showed
lymph node metastasis (P=0.002), pleural invasion (P=0.026) and an advanced TNM stage (P=0.012). The frequency of the
TRAP220 expression in the cases with an ERβ expression was significantly higher than that in those cases without an ERβ expression (P=0.003). The Kaplan-Meier survival curves demonstrated that the patients with a positive
TRAP220 expression had a significantly longer survival time than those patients with a negative
TRAP220 expression (P=0.014). The multivariate analysis revealed that a
TRAP220 expression was an independent good prognostic factor (P=0.049). Our data may be useful to understand the different
biologic basis for the development and progression of the subtypes of
lung adenocarcinoma.