Increased levels of 5-fluorouracil-induced DNA lesions in Bloom's syndrome.

In Bloom's syndrome (BS) the regulation of uracil-DNA glycosylase, an enzyme involved in the repair of DNA containing 5-FU, is altered. 5-FU induces higher levels of DNA fragmentation in BS cells than in non-BS cells. The increase in DNA fragmentation is connected to the cytotoxic mechanism where 5-FU is incorporated into DNA. When 5-FU induces DNA fragmentation by a mechanism not involving the incorporation of drug into DNA, the levels of DNA fragmentation in BS and non-BS cells remain similar.