SKP1 and cancer: To begin to assess the potential relevance of SKP1 or CUL1 alterations in cancer, the frequency of SKP1 or CUL1 copy number losses was assessed using TCGA data obtained for 12 common cancer types (Fig. 1a).50,51 In general, deep (i.e., homozygous) deletions are rare for both genes and typically range from 0 to 1%.