Studies of neoplastic development in respiratory tract epithelium.

The dynamics of neoplastic development in conducting airways were studied in an animal model using morphologic and tissue culture techniques. Evidence for the regression of many metaplastic-dysplastic lesions, including advanced "preneoplastic" lesions, was provided. This regression of lesions is not synonymous with reversion of the neoplastic process. The number of "carcinogen-altered" cells and the number of cells with neoplastic potential continued to increase as a function of time after carcinogen exposure. With the cell culture methods developed for these studies, it is possible to analyze qualitatively and quantitatively the progression of the neoplastic process as it takes place in vivo and to detect and enumerate the progenitor cells of later-appearing cancers. The investigations also provide strong evidence suggesting that carcinogen-exposed organs contain many more cells with neoplastic potential. This expression may, however, be sharply enhanced when permissive or promoting conditions prevail. The investigations open up new avenues to develop means for detection of preneoplastic cell populations and for therapeutic intervention during early phases of the neoplastic disease process.