Comparison of the sensitivity of Fanconi's anemia and normal fibroblasts to the induction of sister-chromatid exchanges by photoaddition of mono- and bi-functional psoralens.

The induction of sister-chromatid exchanges (SCE) by photoaddition of a monofunctional furocoumarin (pyrido[3,4-c]psoralen, PyPs) and a bifunctional furocoumarin (8-methoxypsoralen, 8-MOP) in a normal and three Fanconi anemia (FA) fibroblastic cell lines was investigated. When compared to normal cells, the three FA cell lines demonstrated: a higher sensitivity to 8-MOP photoaddition; an equal or reduced sensitivity to PyPs photoaddition in the low dose range. Normal cells demonstrated a higher sensitivity to photoaddition of PyPs than to 8-MOP in the range of doses used; this is likely to be related to the higher amount of lesions induced by PyPs in DNA. Since FA cells were almost equally sensitive to 8-MOP and PyPs photoaddition and demonstrated a higher sensitivity to SCE induction by 8-MOP than normal cells, it can be concluded that this latter difference is mainly due to cross-links.