Differential expression of biomarkers in lung adenocarcinoma: a comparative study between smokers and never-smokers

Background: Non-small-cell lung cancer arising in never-smokers is usually of adenocarcinoma subtype. The oncogenic pathway of such tumors is poorly understood. To better define the biological characteristics of these tumors, we have compared the expression of a panel of epidermal growth factor receptor (EGFR)-related biomarkers in lung adenocarcinomas from smokers versus those in never-smokers. Patients and methods: Using immunohistochemical analysis, we retrospectively analyzed EGFR, pAKT, PTEN, Ki-67, p27 and hTERT expression in specimens from 190 patients with completely resected lung adenocarcinomas (43 never-smokers and 147 smokers). These analyses were performed on tissue microarrays. Results: EGFR expression was higher in tumors from smokers (P < 0.01), while pAKT was overexpressed mainly in tumors from never-smokers (P = 0.01). As expected, the tumors from smokers presented a higher expression of Ki-67 and a more frequent loss of expression of p27 (P < 0.01). In a multivariate model, two biological factors (p27 and Ki-67) and two clinical factors (age and sex) showed independent significant correlation with never-smoking status. Conclusions: Lung adenocarcinomas in never-smokers have a very distinct immunohistochemical expression profile of EGFR-related biomarkers as compared with lung adenocarcinomas in smokers. High levels of EGFR and Ki-67 are observed in smokers, while never-smokers are characterized by high levels of pAKT and p27.