Overexpression of Cyclin Dl Enhances Gene Amplification1

Defects in cell cycle control and increased genomic instability, including gene amplification, often occur during cancer development. Cyclin Dl plays a pivotal role in G1, and this gene is frequently amplified and overexpressed in several types of human cancer. This study demonstrates that ectopic overexpression of cyclin Dl in a rat liver epithelial cell line markedly increased the yield of cells containing amplified copies of the CAD gene. This effect was associated with a loss of G5-S checkpoint control, although the cycin Di-overexpressing cells had a normal p53 gene. The capacity of cydlin Dl to enhance gene amplification may con tribute to the process of genomic instability during tumor development.