The careless repair of damaged DNA can cause mutations and can result in cancer. Cell biologists from the Erasmus University in Rotterdam studied the repair of double strand breaks. Such breaks can for example arise following radiotherapy.

The researchers simulated radiotherapy by specifically damaging the DNA of mouse cells. Mouse cells in which the gene Rad54 was first inactivated, more often chose a careless means of repairing the damaged DNA. In normal mouse cells no more than 60% of the repairs are done in a careless manner, whereas in cells with an inactivated Rad54 gene this figure was about 80%.

The results show that the Rad54 gene is important for repairing breaks in a neat manner and for preventing mutations. The scientists hope that their findings combined with future research will lead to improvements in the treatment of cancer. In the meantime the researchers are examining patients who overreact to radiotherapy. The idea is that physicians could for example give milder radiotherapy to patients who lack the Rad54 gene.

In another experiment the cell biologists examined the repair of cross-links. This type of damage arises after chemotherapy with, for example, melphalan, mitomycin C or cisplatin. The researchers inactivated the Snm1 gene in mice. After this the mice were given a small quantity of mitomycin.

Mice with a inactivated Snm1 gene died at a lower dose of mitomycin than mice with an intact Snm1 gene. This was probably because the mice with a inactivated Snm1 could not adequately repair the cross-links. Future research in patients who strongly react to chemotherapy must demonstrate whether this also involves a disrupted Snm1 gene.

DNA breaks can be repaired in three ways
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Contact: Michel Philippens
philippens@nwo.nl
31-70-344 0784
Netherlands Organization for Scientific Research
24-Jan-2002