Cell kinetic changes in cultured tumor cells after treatment with radiation and chemotherapy.

Flow cytometry instantaneously determines the percentages of cells in various cell cycle phases to rapidly evaluate effects of irradiation and anti-cancer drugs. We studied these using growth curve analysis and 5-bromodeoxyuridine propidium iodine (BrdU)-(PI) double staining. With conventional DNA histogram methods, determination of S phase fraction was difficult because of overlapping DNA content between G1 and early S phases and between late S and G2 phases. Double staining directly differentiated G1, S, and G2 + M phases. By double staining, rapid transition from G1 to S occurred within 4 h after irradiation or after the drug treatments, and initial G1 arrest induced by irradiation was confirmed for the first time.