PLK1 and cancer: After filtering out essential genes62,63 and genes that were unlikely to be expressed in HCT116 cells (based on CCLE data64; log2 expression score <5.0), we selected 20 genes whose expression strongly correlated with PLK1 levels (Spearman rank correlation coefficient, r ≥ 0.4 in a majority of cancer types) (Figure S3A).