CYCLINS AND BREAST-CANCER

D-type cyclins, the product of the retinoblastoma tumor suppressor gen e and the inhibitors of cyclin-dependent kinases p16 and p27 play a ce ntral role in controlling the rate of G0/G1 to S phase transition of t he cell cycle. Recent data suggest that deregulation of either one of these factors results in development of neoplasia. Furthermore, differ ent expression patterns for cyclin D1 and p27 have been shown to be as sociated with prognosis of malignant disease. In particular, emerging evidence suggests a prognostic relevance of cyclin D1 and p27 gene exp ression in breast cancer. Loss of cyclin D1 expression was shown to co rrelate with relapse-free survival and overall survival. The ability o f antisense oligodeoxy nucleotides to cyclin D1 to block proliferation of malignant cells provides evidence that cyclin D1 and related prote ins should be tested as possible targets for cancer chemoprevention an d might also become a tool in gene therapy.