Public single cell RNAseq (scRNAseq) data for BT-549, MDA-MB-231, HCC1937, and SUM185PE confirmed bulk RNAseq patterns regarding the relational PD-L1/PD-L2 expression patterns seen in cell lines, but also demonstrated considerable heterogeneity in expression of both genes among cancer cells, with proportionally only few cancer cells showing detectable expression even in the cell line with highest expression (MDA-MB-231) (Supplementary Fig. S5i, j). This evidence concerns the gene PDCD1LG2 and cancer.