An update on the implications of cyclin D1 in oral carcinogenesis.

Cyclin D1 promotes cell cycle progression during G1 phase, a key event in G1-S transition. The protein is encoded by gene CCND1, located in chromosomal band 11q13. Cyclin D1 plays key roles in cell biology, including cell proliferation and growth regulation, mitochondrial activity modulation, DNA repair, and cell migration control. CCND1 gene and its protein cyclin D1 are frequently altered by different molecular mechanisms, including amplification, chromosomal translocations, mutations, and activation of the pathways involved in cyclin D1 expression, alterations which appear to be essential in the development of human cancers, including oral carcinoma. This is the first published review of the specific features of cyclin D1 overexpression in oral oncogenesis. Starting with the physiological regulation of cyclin D1, there is an evaluation of its functions, overexpression mechanisms, and the implications of the oncogenic activation of CCND1/cyclin D1 in oral squamous cell carcinoma. The potential diagnostic and prognostic value of cyclin D1 is reviewed. The influence of CCND1/cyclin D1 on tumor size and clinical stage is reported, and an update is provided on the utilization of cyclin D1 as therapeutic target and on the combination of cyclin D1 inhibitors with cytotoxic agents. Future research lines in this field are also proposed.