SLFN11 and cancer: In work by others, SLFN11 staining was found to be present in the whole cell or preferentially localised in the cytosol of cancer cells.5,8,11,22 Here, we developed, validated and applied an in-house IHC assay for analysis of PDX models and demonstrate that, consistently with what was reported in cell lines, SLFN11 shows an almost exclusively nuclear localisation across a multitude of different cancer types tested.