The relationship between cell killing effect and number of lanthanide atoms bound to DNA molecules in cultured HeLa cells treated with rare earth elements

Abstract

HeLa S-3 cells were treated with several rare earth elements, Ce, La, and Sm, at 37 °C for 1 hour and the relationship between the lethal effects of these elements and the number of the atoms bound to DNA, RNA, and proteins was examined. Among the 3 element, only Ce gave an exponential dose-survival relationship from which the value of mean lethal concentration (D ₀) was determined to be 6.75 mM. By using identically treated cells, the number of Ce atoms combined with DNA, RNA and protein molecules in HeLa cells were determined after fractionation of the cells using neutron activation analysis. In this way, theD ₀ value given as the Ce concentration was replaced by the number of Ce atoms combined with each fraction, then the target volumes, viz., cell killing efficiency, expressed as the reciprocal ofD ₀ value was calculated for each fraction. The results suggested that DNA and RNA could stochiometrically be the primary target molecule for cell killing by Ce.