Lung cancer is the leading cause of cancer mortality at least in part due to its diagnosis at advanced stages. Therefore, the identification of novel molecular markers for risk assessment and early detection is of paramount importance. Recently, we used a high throughput western immunoblotting technique and an in vitro lung carcinogenesis cell system to identify proteins that are expressed differentially in normal, immortalized, transformed, and tumorigenic human bronchial epithelial cells. In the present study, we selected four of these proteins for validation as potential important molecules in the sequential pathogenesis of non-small cell lung carcinomas in vivo. We performed an immunohistochemical analysis of E-cadherin (membranous), Caspase-8 (cytoplasmic), Stat-5 (cytoplasmic), and p70s6k (nuclear) in paraffin-embedded tissue samples from lung cancers (n=60) and adjacent normal and preneoplastic epithelial tissues (n=223) placed in tissue microarray (TMA). The lung samples examined included: 30 adenocarcinomas (ADCAs), 30 squamous cell carcinomas (SCCs), 30 normal bronchial epithelia, 72 bronchial hyperplasias, 29 squamous metaplasia, 28 squamous dysplasias, and 64 alveolar adenomatous hyperplasias (AAHs). The main findings were as follows: a) E-cadherin expression was reduced (p<0.001), and Caspase-8, Stat-5, and p70s6k were increased (p<0.001-0.008) in tumors compared to normal epithelium specimens. b) In SCCs, an increasing level of abnormal expression was detected for all four markers with increasing severity of histology, and significant differences (p<0.001) between normal epithelium and high-grade dysplasia were detected for E-cadherin, Stat-5, and p70s6k. c) In ADCAs, an abnormal expression trend was detected between normal bronchial epithelium, AAH and tumors for all markers except for p70s6k, with significant differences (p<0.001-0.017) between AAHs and ADCAs in E-cadherin, Caspase-8 and Stat-5. Our studies demonstrate that protein immunohistochemical expression analysis using TMAs of lung tumor and preneoplastic specimens are suitable methodology for the validation of proteomic data and the study of new markers in the pathogenesis of lung cancer. Our findings that E-cadherin, Caspase-8, Stat-5, and p70s6k are expressed differentially in the sequential pathogenesis of SCC and ADCA suggest that they play an important role in NSCLC tumorigenesis. Supported by Early Detection Research Network grant U01 CA86390 from the NCI and by the Department of the Army grant W81XWH-04-1-0142.

[Proc Amer Assoc Cancer Res, Volume 46, 2005]