SLFN5 and cancer: Recent studies demonstrate that the intermediate epithelial/mesenchymal state of cancer cells may allow them to re-epithelialise at distant metastatic sites and colonise.14,15,50 Therefore, if a gene, such as SLFN5, is considered for future cancer treatment, it needs to be efficiently and stably transfected and expressed in all target cancer cells to avoid the intermediate epithelial/mesenchymal states.