CUL1 and cervical squamous intraepithelial neoplasia: Indeed, while Cyclin E1 protein levels are elevated in ~45–50% of HGSOC cases,30,31 genomic amplification of the Cyclin E1 (CCNE1) gene only occurs in ~20% of cases.29 This study identifies a novel mechanism whereby diminished SKP1 or CUL1 expression, and thus reduced SCF complex activity, may lead to increased Cyclin E1 protein levels that correspond with increases in CIN.