A Comparison of the Cell Cycle in Induced Carcinomas and Their Normal Counterpart.

and clinical tumors is under study in many laboratories and is leading to the accumulation of a sizable catalogue of tumor cell parameters (1—6,8, 10—16,18, 20—24). On the basis of such measurements, there is as yet little to dis tinguish the tumor cell from a variety of normal cells which have also been analyzed. Since the tumor cell and normal cell have usually been measured independently and seldom derive from corresponding tissues, possible differences be tween tumor and normal may be obscured by larger differ ences between distinctive cell types. This study is an attempt to compare the kinetics of a carcinogenically in duced tumor and a normal tissue in an instance where the correspondence of these tissues is reasonably assured. The kinetic analysis is based on autoradiographic observations of the incorporation of tritiated thymidine in vivo in the epithelium and epithelial tumors of hamster cheek pouch.