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Eukaryotic elongation factor 1 alpha 2 (eEF1A2) encodes an isoform of the alpha subunit of the elongation factor 1 complex and is responsible for the enzymatic delivery of aminoacyl tRNA to the ribosome. Our proteomic analysis has identified eEF1A2 as one of the proteins expressed during malignant progression from adenocarcinoma in situ (AIS) to early invasive lung adenocarcinoma. The expression level of eEF1A2 in 175 lung adenocarcinomas was examined by immunohistochemical staining in relation to patient prognosis and clinicopathological factors. Quantitative PCR analysis and fluorescence in situ hybridization (FISH) were performed to evaluate the amplification of the eEF1A2 gene. Relatively high expression of eEF1A2 was observed in invasive adenocarcinoma (39/144 cases) relative to minimally invasive adenocarcinoma (1/10 cases) or AIS (0/21 cases). Among invasive adenocarcinomas, solid‐type adenocarcinoma (15/32 cases, 47%) showed higher expression than other histological subtypes (23/92, 25%). Patients with eEF1A2‐positive tumors had a significantly poorer prognosis than those with eEF1A2‐negative tumors. Of the five tumors that were eEF1A2‐positive, two cases showed amplified genomic eEF1A2 DNA, which was confirmed by both qPCR and FISH. These findings indicate that eEF1A2 overexpression occurs in the course of malignant transformation of lung adenocarcinomas and is partly due to eEF1A2 gene amplification. [ABSTRACT FROM AUTHOR]

Introduction: Lung adenocarcinoma progresses stepwise from atypical adenomatous hyperplasia to adenocarcinoma in situ (AIS), followed by minimally invasive adenocarcinoma (MIA), and then obvious invasive adenocarcinoma. In this study, we examined the protein expression profiles of early and epidermal growth factor receptor (EGFR) mutation‐positive lung adenocarcinomas. Methods: Fifteen cases of small and EGFR mutation‐positive adenocarcinomas were collected, including AIS, MIA, and small invasive adenocarcinoma (SIA). We examined their protein expression profiles by tandem mass tag (TMT)‐labeling liquid chromatography‐mass spectrometry (LC–MS/MS) and compared the results between AIS and MIA versus SIA. The differentially expressed proteins were then verified by Western blot analysis and immunohistochemistry (IHC). The clinicopathological implications of the proteins were also examined by IHC. Results: A total of 4220 proteins were identified by LC–MS/MS analysis. Pathway analysis of the differentially expressed proteins revealed that pathways related to interferon α/β signaling, glutamate and glutamine metabolism, and gluconeogenesis were upregulated in SIA relative to AIS. Among the 13 differentially expressed proteins, cellular retinoic acid binding protein 2 (CRABP2), delta(24)‐sterol reductase (DHCR24), and adenylate kinase 4 (AK4) were expressed significantly more strongly in SIA than in AIS. Patients with high expression of CRABP2, DHCR24, and AK4 showed a significantly poorer outcome than those with low expression. Conclusion: In comparison with AIS, SIA shows differences in several different protein expression pathways. Furthermore, CRABP2, DHCR24, and AK4 are useful IHC markers for diagnosis of lung adenocarcinoma invasiveness and may be associated with malignant progression of AIS. [ABSTRACT FROM AUTHOR]