hCDC4 gene mutations in endometrial cancer.

Cyclin-dependent kinase 2 activated by cyclin E is involved in the initiation of DNA replication and other S phase functions. Consistent with this role, cyclin E protein accumulates at the G1-S phase transition and declines during early S phase. This profile of expression is the result of periodic transcription and ubiquitin-mediated proteolysis directed by SCF(hCdc4). However, in many types of human tumors cyclin E protein is elevated and deregulated relative to the cell cycle by an unknown mechanism. Here, we show that the F-box protein hCdc4 that targets cyclin E to the SCF (Skp1-Cull-F-box) protein ubiquitin ligase is mutated in at least 16% of human endometrial tumors. Mutations were found either in the substrate-binding domain of the protein or at the amino terminus, suggesting a critical role for the region of hCdc4 upstream of the F-box. hCDC4 gene mutations were accompanied by loss of heterozygosity and correlated with aggressive disease. The hCDC4 gene is localized to chromosome region 4q32, which is deleted in over 30% of human tumors. Our results show that the hCDC4 gene is mutated in primary human tumors and suggest that it may function as a tumor suppressor in the genesis of many human cancers.