RADIATION-INDUCED CARCINOGENESIS - INDIVIDUAL SENSITIVITY AND GENOMICINSTABILITY

In spite of a well-known relationship between exposure to radiation an d increased risk for cancer development, the biological mechanisms inv olved in radiation-induced carcinogenesis remain poorly documented. Va rious hypotheses are discussed in this paper. It appears that radiatio n cannot be directly responsible for the numerous genetic alterations of cancer cells. Most of them occur during tumor progression. Only one or a very limited number of them was induced by radiation many years before tumor growth. This long delay is a major difficulty for experim ental research and raises many questions. Recently, it has been shown that a genomic instability occurs after many generations in cells desc ending from irradiated cells. This instability leads to multiple genet ic alterations and, preferentially, affects some chromosome structures , particularly telomeres. This kind of telomeric instability - related to the shortening of telomeric DNA sequences - has also been observed in senescent cells as well as in non-senescent cells from patients pr edisposed to cancer, and this process may possibly also occur in the p rogeny of irradiated cells.