Heat Shock Treatment Protects Human Hl-60 Cells from Apoptosis Induced by Lectin II Isolated from Korean Mistletoe, Viscum Album Var. Coloratvm

Abstract

Mistletoe lectin II (ML II) isolated from Korean mistletoe (Viscum album var. Coloratum), an effective therapeutic agent for cancers, is known to induce cell death via apoptosis. In the present study, we found the protective effect of heat shock treatment of human leukemia HL-60 cells against ML II-induced apoptosis. Exposure of HL-60 cells to ML II for 4 h resulted in apoptosis of the cells, which was evaluated by examining “DNA ladder” formation and DNA fragmentation assay. The DNA fragmentation was significantly reduced in the cells subjected to heat shock treatment by incubation at 42 °C for 1 h and subsequently allowed to recover for 2-16 h at 37 °C., prior to exposure to ML II. HL-60 cells transfected with heat shock protein (hsp) 70 gene exhibited resistance to ML II-induced apoptosis very similar to that seen when untransfected cells were heat-shocked. These results indicate that ML II-induced apoptosis in HL-60 cells is inhibited by heat shock treatment, at least in part, via a hsp 70-mediated mechanism.