Abstract
Many functional molecules controlling diverse cellular function are included in low-molecular weight proteins and peptides. To identify proteins controlling function in lung adenocarcinomas (AC), we performed two-dimensional gel electrophoresis employing tricine-SDS polyacrylamide in the second dimension (tricine 2-DE). This system was able to detect proteins under 1 kDa even with post- translational modifications. To confirm the utility of detected proteins as novel tumor markers for AC, we performed immunohistochemical analysis using 170 formalin-fixed and paraffin-embedded lung AC tissues. Tricine 2-DE revealed that five proteins including S100A16 were overexpressed in lung AC-derived cells compared with lung squamous cell carcinoma, small cell carcinoma, and large cell neuroendocrine carcinoma- derived cells. Immunohistochemically, S100A16 showed various subcellular localization in lung cancer tissues and a membranous staining status was correlated with the T-factor (P=0.0008), pathological stage (P=0.0015), differentiation extent (P=0.0001), lymphatic invasion (P=0.0007), vascular invasion (P=0.0001), pleural invasion (P=0.0087), and gender (P=0.039), but not with the age or smoking history. More importantly, membranous staining of S100A16 was significantly correlated with a poorer overall survival of either stage I (P=0.0088) or stage II / III (P=0.0003) lung AC patients, and multivariate analysis confirmed that membranous expression of S100A16 was an independent adverse prognostic indicator (P=0.0001). The present results suggest that S100A16 protein is a novel prognostic marker for lung AC.
Highlights
Lung cancer is the leading cause of cancerrelated death worldwide for both males and females
Expression of S100A16 protein in lung cancer tissues S100A16 expression was observed at various levels as cytoplasmic, nuclear (Figure 2A), or membranous staining (Figure 2B) in cancer cells of lung ACs
S100A16 membranous staining in tumor cells was observed in 73 of 170 (42.9%) ACs (Table 2)
Summary
Lung cancer is the leading cause of cancerrelated death worldwide for both males and females. Since the amount and repertoire of peptides in the circulation change dynamically according to the physiological or pathological state of an individual, it is possible that comprehensive peptide analysis may lead to the discovery of novel biomarkers or new diagnostic approaches (Diamandis, 2006) He et al reported that measuring panels of peptide markers might be more sensitive and specific than conventional approaches (He et al, 2013). Dong et al reported that shotgun proteomics most commonly involved the digestion of proteins by trypsin, followed by the identification of product peptides, and the use of this information to infer protein identities and possibly targeted PTMs (Dong et al, 2014) They reported that since digestion is a highly complex chemical process, a large proportion of identifiable products are not targeted for analysis. Conclusions: The present results suggest that S100A16 protein is a novel prognostic marker for lung AC
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