Słabicki et al. analyzed cytotoxicity data of 4518 clinical and preclinical small molecules against 578 cancer cell lines to show correlation between cytotoxicity and expression level of 499 E3 ligase mRNA.118 They found that pan cyclin-dependent kinase (CDK) inhibitor CR8 shows a level of correlation between cytotoxicity of each cell line and the mRNA levels in the same cell line of CDK12 and DNA damage-binding protein-1 (DDB1), which is a component of DDB1–CUL4 E3 ligase complexes. Here, DDB1 is linked to cancer.