PLK1 likely inversely correlates with HLA activity in cancer. (a) The PLK1 expression levels inversely correlate with the HLA activity in 12 cancer types and cancer cell lines and positively correlate with the HLA activity in 3 cancer types (Spearman correlation, FDR<0.1). (b) Most of the 24 HLA genes show negative expression correlations with the PLK1 expression in the 12 cancer types in which the PLK1 expression inversely correlates with the HLA activity (Pearson correlation, FDR<0.1). (c) The PLK1 expression levels positively correlate with somatic mutation counts in cancer. (d) The PLK1 expression levels positively correlate with the numbers of mutations yielding predicted HLA-binding peptides. HLA: human leukocyte antigen. CCLs: cancer cell lines. R: Spearman or Pearson correlation coefficient. FDR: false discovery rate.