CAT and neoplasm: One of the main reasons for utilizing MCF-7 tumor cells to identify free radical based pathways for TPT-induced tumor cell death was that we have shown that MCF-7 breast tumor cells are extremely efficient in activating adriamycin to its free radical species and these cells contain significant numbers of free radical-based detoxification enzymes e.g., SOD, catalase and GPx (Sinha et al., 1987, 1989).