The thymidine analogue bromodeoxyuridine (BrdU) has a long, colorful history of heavy use in molecular and cytokinetic studies (1, 2). BrDU is incorporated into newly synthesized DNA only in S-phase cells, and then immunocytochemically detected with BrDU antibodies. This method allows for extremely accurate and comprehensive comparative studies of a variety of cells ranging from normal to neoplastic. Cells can be labeled in vitro or in vivo with the analogue, and then BrDU antibodies used to determine the resulting levels of incorporation. Such BrDU antibody studies allow quantitation of DNA-synthesis rates, cell fraction in S-phase, and construction of dynamic proliferation profiles (with such variables as S-phase transit rate and potential doubling time) using bivariate BrdU/DNA flow cytometry analyses. Some examples of the use of BrDU antibodies in oncology studies include their use to investigate replicative stress and DNA damage in cancers (3) and breast cancer survival rates in response to chemotherapy (4). In neurobiology, BrDU antibodies have helped illuminate the role of the 5-HT receptor in neurogenesis and neuron maintenance (5) and insights into how new neurons within the adult hippocampus function in learning and memory (6).
