Analysis of c-erb-1 (EGFR) and c-erb-2 (HER2) expression in bronchial dysplasia: Evaluation of potential targets for chemoprevention of lung cancer

Abstract

7070 Background: Lung cancer is preceded by a premalignant phase during which intervention could decrease associated morbidity and mortality. Molecular characterization of factors involved in controlling progression of bronchial dysplasia (BD) will provide markers of premalignant change and identify targets for chemoprevention. Methods: Immunohistochemical (IHC) analysis of EGFR, HER2, Ki67 and MCM2 expression in BD was undertaken in 268 bronchoscopically obtained biopsies from 134 consecutive subjects recruited to University of Colorado protocols as study subjects with prior sputum atypia and >20 pack years tobacco use or FEV1 < 75% predicted or as never- or healthy-smoker controls. IHC on the worst and best histologic biopsies from each subject were scored and linear regression tests were used to determine significance of correlation between marker expression and histology or proliferation. Results: Analysis of biopsies with the most severe diagnosis from each subject showed a linear relationship between increasing marker expression and severity of dysplastic change for EGFR (p < 0.001), Ki67 (p < 0.001) and MCM2 (p = 0.001) but not HER2 (p = 0.102). Increased expression of either EGFR or HER2 was associated with increased expression of proliferation markers Ki67and MCM2, and combined overexpression of these receptors was associated with the highest levels of proliferation. Finally, in a comparison of subjects that were grouped according to the degree of difference between their best and worst biopsy histology, the absence of an associated trend toward increased EGFR expression with increased difference in histology suggested a field effect in the induction of EGFR expression. Conclusions: Our results 1) demonstrate a direct correlation between levels of EGFR expression and degree of BD, 2) suggest a field effect in the induction of EGFR expression in the airways of subjects with BD and 3) indicate a potential synergistic effect on epithelial proliferation in lesions with increased expression of both EGFR and HER2. These findings suggest that EGFR plays a prominent role in the development and progression of BD and could provide a promising target for chemoprevention of lung cancer. [Table: see text]