Cell-killing efficiency and number of platinum atoms binding to DNA, RNA, and protein molecules of HeLa cells treated with combinations of hyperthermia and cis-diamine(glycolato)platinum(II)

HeLa S-3 cells were treated with195mPt-radiolabeledcisdiamine(glylato)platinum(II) (254-S) for 60 min at various temperatures, and the relationship between the lethal effect and the number of Pt atoms binding to DNA, RNA, and proteins was examined. The mean lethal concentration (Do) of 254-S for a 60-min treatment at 0‡C, 25‡C, 37‡C, 40‡C, 42‡C, and 44‡C was 233,132, 61.1, 42.7, 25.6, and 9.9 ΜM, respectively. By using identically treated cells, the numbers of Pt atoms combined with DNA, RNA, and protein molecules were determined in the subcellular fractions. Thus, the D0 values given as drug concentrations were replaced with the number of Pt atoms combined in each fraction. Then, the cell-killing efficiency of the Pt atom was expressed as the reciprocal of the number of Pt atoms combined and was calculated for each molecule. The efficiency for the DNA molecule was 0.61X104, 1.09xl04, 1.88xl04, 1.90xl04, 2.66xl04, and 5.88xl04 nucleotides, respectively, for the conditions described. From 0‡C to 44‡C, the cell-killing efficiency of Pt atoms increased by a factor of 9.6.