Cell cycle kinetic studies in human cancers. Development of three DNA-specific labels in three decades

Controversy has epitomized the prognostic and clinical significance accorded to cell cycle kinetic studies in neoplastic diseases. Recent introduction of monoclonal antibodies to thymidine analogues such as iododeoxyuridine and bromodeoxyuridine has unveiled a spectacular new area of research. Large numbers of patients with liquid and solid tumors have been interrogated by introducing iododeoxyuridine and bromodeoxyuridine as DNA-specific probes in vivo. Further in vitro incubation of S-phase cells already double-labeled in vivo with tritiated thymidine has added a whole new dimension to the kinds of questions that can now be addressed with alacrity. Time is rapidly approaching when this information will be available in a prompt enough fashion to be useful for planning therapeutic strategies. Reviewed are the salient features of the rapid progress achieved in the last decade in this exciting discipline.