Thiol antioxidants in combination with vitamin B12 induce apoptotic death of human lymphocytic leukemia cells by destabilization of lysosomes with the involvement of iron ions.

The extensively used thiol antioxidants (dithiothreitol, glutathione, and N-acetylcysteine) in combination with hydroxycobalamine (vitamin B12) gain toxic activity in relation to human lymphocytic leukemia cell line HL60. Combined treatment with thiol and vitamin B12 was followed by early destabilization of lysosomes and apoptotic death of cells. The cytotoxic effect was abolished by caspase inhibitors. An iron-chelating agent deferoxamine partly prevented cell death, while lysosomal protease inhibitor pepstatin produced no protective effect.