The mouse Slfn family has been implicated in various physiological or pathological processes, including T-cell activation, thymocyte maturation, fibroblast and tumour cell proliferation.1–4 However, the human SLFN family has not been extensively studied, with the exception of SLFN11, which is capable of suppressing HIV replication, and positively correlates with the effect of topoisomerase inhibitors on human cancer cells.5–7 There are very few studies on human SLFN5, and the results are inconsistent. The gene discussed is SLFN5; the disease is cancer.