Bleomycin (BLM) has demonstrated potent activity in treating
malignant lymphomas but its therapeutic efficacy is hampered by induction of lung
fibrosis. This side effect is related to the ability of the
drug to generate
reactive oxygen species in lung cells. In the present study, we evaluated the consequences of deglycosylation of BLM in term of cytotoxic activity and generation of
reactive oxygen species. When tested on U937 human
lymphoma cells, both compounds generated a typical apoptotic phenotype. Cell death induction was associated with Bax oligomerization, dissipation of the mitochondrial membrane potential, release of
cytochrome c,
caspase activation,
chromatin condensation and internucleosomal degradation. Whereas both
reactive oxygen species and c-jun NH(2)-terminal
kinase (JNK) inhibitors prevented BLM-induced U937 cell death, only JNK inhibition prevented
deglycosylated BLM-mediated cell death. Both compounds induced clustering of
TRAIL receptors (DR4 and DR5) and Fas at the cell surface but neither a chimeric soluble
DR5 receptor that inhibits TRAIL-induced cell death nor a dominant negative version of the adaptor molecule Fas-associated death domain prevented BLM-induced cytotoxicity. These observations indicate that deglycosylation of BLM does not impair the ability of the
drug to trigger cell death through activation of the intrinsic pathway but prevents induction of
reactive oxygen species. This observation suggests that
deglycosylated BLM could exhibit less toxic side effects and could warrant its use in clinic.