DIFFERENTIAL SUPPRESSION BY PROTEASE INHIBITORS AND CYTOKINES OF APOPTOSIS INDUCED BY WILD-TYPE P53 AND CYTOTOXIC AGENTS

Apoptosis induced in myeloid leukemic cells by wild-type p53 was suppr essed by different cleavage-site directed protease inhibitors, which i nhibit interleukin-1 beta-converting enzyme-like, granzyme B and cathe psins B and L proteases. Apoptosis was also suppressed by the serine a nd cysteine protease inhibitor N-tosyl-L-phenylalanine chloromethylket one (TPCK), E64, but not by other serine or cysteine protease inhibito rs including N-alpha-p-tosyl-L-lysine chloromethylketone (TLCK), E64, pepstatin A, or chymostatin. Protease inhibitors suppressed induction of apoptosis by gamma-irradiation and cycloheximide but not by doxorub icin, vincristine, or withdrawal of interleukin 3 from interleukin 3-d ependent 32D non-malignant myeloid cells, Induction of apoptosis in no rmal thymocytes by gamma-irradiation or dexamethasone was also suppres sed by the cleavage-site directed protease inhibitors, but in contrast to the myeloid leukemic cells apoptosis in thymocytes was suppressed by TLCK but not by TPCK. The results indicate that (i) inhibitors of i nterleukin-1 beta-converting enzyme-like proteases and some other prot ease inhibitors suppressed induction of apoptosis by wild-type p53 and certain p53-independent pathways of apoptosis; (ii) the protease inhi bitors together with the cytokines interleukin 6 and interferon-gamma or the antioxidant butylated hydroxyanisole gave a cooperative protect ion against apoptosis; (iii) these protease inhibitors did not suppres s induction of apoptosis by some cytotoxic agents or by viability-fact or withdrawal from 32D cells, whereas these pathways of apoptosis were suppressed by cytokines; (iv) there are cell type differences in the proteases involved in apoptosis; and (v) there are multiple pathways l eading to apoptosis that can be selectively induced and suppressed by different agents.