The L929sAhFas cells used in the previous reports were produced by expressing the human Fas gene in L929sA cells, a TNFα-sensitive derivative of the murine fibrosarcoma cell line L929 cells29,37; therefore, some differences between these two cell lines may underlie the different functions of RIP1 in mediating RIP3-independent apoptosis. Here, RIPK3 is linked to fibrosarcoma.