Double labeling of human leukemic cells using 3H-cytarabine and monoclonal antibody against bromodeoxyuridine

A new technique using immunofluorescence and autoradiography is described, in which the DNA of cells in S phase are labeled with two different probes. This method makes it possible to study the relationship between DNA synthesis and the uptake and/or incorporation of chemotherapeutic agents into normal or neoplastic cells. An example is provided in which the incorporation of 3H-cytarabine into DNA is demonstrated to occur only in cells which were synthesizing DNA during exposure to 3H-cytarabine. Other radioactively labeled probes can be used as well.