Differences in the consequences of the decay of radioactive64Cu atoms incorporated in cells under either in vitro or in vivo conditions

Summary To study the lethal effect of⁶⁴Cu under in vitro conditions, asynchronous mammalian cells were used. A lethal effect does exist as a consequence of the decay itself of a few⁶⁴Cu atoms incorporated in cellular DNA. This lethal effect is characterized by an exponential survival curve with no shoulder and no tail; it exists even for non-dividing cells. The lethal efficiency per decay is very high. To test the⁶⁴Cu lethal effect under in vivo conditions, experiments were performed with ascitic cells developing in mice. In this case, the lethal effect also exists, but it is not a function of the⁶⁴Cu doses injected in the mice. Faced with this puzzling result, a systemic approach was necessary to understand and counteract ascitic cells developing in mice.Dedicated to Prof. L.E. Feinendegen on the occasion of his 60th birthday