PDCD1 and melanoma: To assess the relative levels of PD-1 gene expression in large numbers of PDAC cell lines and clinical specimens, we obtained next generation sequencing data from a public dataset (the Broad Institute) and two prior studies of human PDACs.7–9 Query of the Broad Institute RNASeq profiling of cancer cell lines demonstrates that PDCD1 (i.e., PD-1) gene expression levels for PDAC cells were among the highest for solid organ cancers and notably higher than PDCD1 expression levels in cancers that are routinely treated with ICIs (e.g., colorectal cancer, lung cancer, and melanoma) (Fig. 2a).