FLOW MICROFLUOROMETRIC ANALYSIS OF CELL KILLING WITH CYTOTOXIC DRUGS

Abstract

The relative deoxyribonucleic acid (DNA) content of cells in culture was determined in a flow microfluorometer after staining with a fluorescent DNA-specific technique. The distribution of the DNA content was used to study the effect of arabinosylcytosine (Ara-C), hydroxyurea, bleomycin and actinomycin D on the progression of the cells through the cell cycle. It was found that short exposures to 10^–5 M Ara-C reversibly blocks the cells predominantly in early S phase. The cells blocked in S died after prolonged treatment at low concentrations. A small population was blocked in G₁. Similar effects were observed at 10^–4 M Ara-C which were irreversible even after short exposures. A block of the majority of the cells in early S and a few cells in G₁ was also found with 10^–3 M hydroxyurea. Bleomycin resulted in a block in G₁ and G₂ phases. Actinomycin D treatment at 10^–8 M for 24 hr inhibited the initiation of DNA synthesis, since almost all cells were found in G₁. The method is very suitable for rapid studies of drug effects on cell cycle progression.