Multistage-promotion and carcinogenesis studies in rat tracheal epithelial cells in culture

In summary, two in vitro systems with rat tracheal epithelial cells were used to demonstrate that initiated respiratory tract epithelial cells can be promoted or enhanced to transform at a higher frequency by exposure to a noncarcinogenic tumor promoter. The latter two studies suggest possible mechanisms for this enhancement: 1) TPA amplifies the chromosomal instability brought about by initiating doses of carcinogen and 2) TPA alters gene expression and cellular differentiation such that it causes the initiated cell to escape the normal differentiation and senescence process thereby enhancing the proliferative lifespan of initiated cells.