Aberrant DNA Double-strand break repair in the ovarian cancer cell line OVCAR-8

Abstract

Aberrant repair of DNA double strand breaks (DSBs) is thought to be important in the generation of gross chromosomal rearrangements. To examine how DSBs might lead to chromosomal rearrangements, we investigated the consequences of the repair of a single DSB in the human ovarian cancer cell line OVCAR-8. An I-SceI recognition site was introduced into chromosome 2 of the recipient cells. This 18-bp sequence was inserted between a constitutive promoter (EF1α) and the Herpes simplex virus thymidine kinase (Hstk) gene which confers sensitivity to gancyclovir (GCV). Transfection of an I-SceI expression vector caused a single DSB in a subset of cells; clones that had aberrant repair and separated the EF1α promoter from the Hstk gene were resistant to GCV treatment. The most common mutations were interstitial deletions flanking the I-SceI cleavage region. More complex rearrangements, including chromosomal insertions derived from distant chromosomes regions, were also detected in some clones. This model system provides an ideal tool to investigate the mechanism of DNA repair in human tumor cells.