Measurement of DNA content and of tritiated thymidine and bromodeoxyuridine incorporation by the same cells

We tested a method of measuring DNA content (Feulgen) and tritiated thymidine ([³H]-T) and bromodeoxyuridine (BrdU) incorporation by the same cell. Initial experiments showed that Feulgen hydrolysis denatured the DNA of fixed cells sufficiently to allow detection of incorporated BrdU with monoclonal antibodies. MCa-11 cells were then double-labeled with [³H]-T and BrdU, placed on slides, and Feulgen stained. Next, absorption cytometry was performed to measure the DNA content of randomly selected cells. Feulgen staining and the development and removal of either the [³H]-T or the BrdU grains after DNA measurements did not interfere with subsequent detection of the grains from the other label, and BrdU and [³H]-T can be used reliably in combination for identification of S-phase cells. This method may eventually allow the use of microscope-based image analysis to selectively measure the DNA contents and the BrdU/[³H]-T labeling of non-transformed stromal and cancer cells in solid tumors, thereby providing new insights into the growth kinetics of these heterogeneous cell populations.