CCND1 and breast cancer: Perhaps most interesting, however, was the induction of cyclin D1 (CCND1; fold change = 1.5, Q = 0.009) in cells with reduced CRY2. CCND1 is a firmly established oncogene that is often overexpressed in primary breast cancers [15], and while aberrant overexpression of CCND1 is often due to gene amplification, up to 50% of breast cancers display increases in CCND1, many of which cannot be explained by copy number variations, indicating that alternative mechanisms such as transcriptional dysregulation must be involved [16].