One of the key findings of these studies is the cell line-specific function of mirSNPs. This is likely in part due to the cell type specific variation in miRNA expression profiles resulting in the effect of a mirSNP being evident in one cell line and not in another (Landgraf et al., 2007; Ludwig et al., 2016). We observed that the identity and number of functional mirSNPs reproducibly varied across the different cell types. This demonstrates one of the strengths of PASSPORT-seq in that it can identify cell line-specific effects of mirSNPs. These differences were validated using a second PASSPORT-seq run that reproduced the cell line effect. Additionally, the cell line-specific effect was also observed in the application of the assay to test 111 mirSNPs in pharmacogenes. The tissue/cell specificity of mirSNP function could also explain why the effects of mirSNPs are not always consistent across studies. This further complicates the bioinformatics predictions of the functional impact of the mirSNPs. Thus, when using this assay, the cell line must be carefully chosen to reflect the cell type of interest regarding the
