Several studies have shown that tumour-expressed FasL is capable of killing Fas-bearing, sensitive cells in vitro (O'Connell et al, 1996; Yoong et al, 1999), while expression of FasL by human tumours in vivo is associated with apoptosis and loss of TILs (Bennett et al, 1998). This evidence concerns the gene FASLG and neoplasm.