Selective activation of caspases during apoptotic induction in HL-60 cells

Apoptosis is a highly regulated biochemical process that results in the selective death of cells, Members of the caspase family of cysteine proteases play a pivotal role in the effector phase of apoptosis, We show that, in HL-60 cells, the addition of either anisomycin, a protein synthesis inhibitor, or geranylgeraniol, an intermediate in the cholesterol biosynthetic pathway, results in a rapid and en masse induction of apoptosis, The levels of actin, p42 and p44 MAPK, JNK1, JNK2, p38, and PCNA were not substantially altered during this process. Although these treatments appear to function by diverse pathways, they both result in the processing and activation of caspase-3 (CPP32 beta/Yama/Apopain). In contrast, no activation of caspase-1 (interleukin-1 beta converting enzyme (ICE)) was observed, Furthermore, we obtained ambiguous results regarding the activation of caspase-2 (Ich-1) depending on the antibody used, Pretreatment of the cells with benzyloxycarbonyl-val-Ala-Asp-(OMe)-fluoromethylketone (zVAD.fmk), a tetrapeptide inhibitor of caspases, prevented the induction of apoptosis for 24 h, Even after 72 h of treatment, some cells were still alive and progressing through the cell. cycle, suggesting that blockage of caspase activity is able to protect cells. These results suggest that selective activation of some caspases is necessary to induce apoptosis in HL-60 cells.