5-Bromo-2′-deoxyuridine (BrdU) is used to analyze cell proliferation, because of its facile incorporation into DNA during the S phase of the cell cycle. BrdU stimulates cellular differentiation and maturation in leukemia cell lines, while it inhibits differentiation of friend erythroleukemia cells. Studies of BrdU incorporation often subsequently use BrdU-specific antibodies with fluorescent tags, for detection of the incorporated BrdU, via such methods as flow cytometry or fluorescence microscopy.