Identification of genes expressed differentially in an in vitro human lung carcinogenesis model

Lung cancer is the deadliest among all cancers in the US for both men and women. Early detection of premalignant lesions or tumors appears to be a promising approach to reducing the morbidity and mortality from lung cancer because the survival of early stage lung cancer patients is better than that of patients with advanced cancers. We approached the identification of early biomarkers of human lung carcinogenesis, by combining the use of cDNA array and an in vitro human lung carcinogenesis model that consists of normal (NHBE), immortalized (BEAS-2B and 1799), transformed (1198) and tumorigenic (1170-I) human bronchial epithelial (HBE) cells. We hypothesized that certain genes that are expressed differentially among these cells can serve as both biomarkers for early detection and targets for intervention. Nineteen genes were downregulated and six were upregulated in tumorigenic 1170-I HBE cells compared to normal HBE cells (NHBE) using cDNA array. Downregulated genes encode cell-to-cell and cell-to-matrix adhesion-related proteins, calcium-binding proteins and some enzymes or growth factor-related proteins. The functions of upregulated gene were more variable. Similar expression of selected genes was found in different nonsmall cell lung cancer cell lines analyzed by Northern blotting. Furthermore, the differential expression of some genes was also observed by in silico analysis of database of human lung tumors. The differentially expressed genes encode calcium-binding proteins and cell-cell and cell-matrix adhesion proteins. Furthermore, Northern blotting analysis of RNA from different cell lines comprising an in vitro carcinogenesis model including normal, immortalized, transformed, and tumorigenic cells indicated that the expression of subsets of the identified genes changed at different stages of carcinogenesis. These data show that the in vitro carcinogenesis cell system could be useful for discovering potential biomarkers of early and late stages of lung carcinogenesis and targets for chemoprevention.