The requirement that Bax must be activated and migrate to the mitochondria for the release of cytochrome c would predict (a) a delay in the cytochrome c release process after PDT, as we previously observed in mouse lymphoma LY-R cells and in human tumour A431 and MCF-7 cells (Chiu et al, 2001; Chiu and Oleinick, 2001; Lam et al, 2001; Xue et al, 2001b) and (b) temperature dependence of the processes of Bax migration and cytochrome c release (Kessel and Castelli, 2001). This evidence concerns the gene BAX and lymphoma.