Extracellular Caspase-8 Dependent Apoptosis on HeLa Cancer Cells and MRC-5 Normal Cells by ICD-85 (Venom Derived Peptides)

BACKGROUND Our previous studies revealed an inhibitory effect of ICD-85 (venom derived peptides) on MDA-MB231 and HL-60 cell lines, through induction of apoptosis. The purpose of this study was to investigate apoptosis-induced mechanism on HeLa and MRC-5 cells by ICD-85 through activation of caspase-8. METHODS Cell viability, cytosolic enzyme Lactate Dehydrogenase (LDH) and cell morphology were assessed under unexposed and ICD-85 exposed conditions.Caspase-8 activity was assayed by caspase-8 colorimetric assay Kit. RESULTS The results show that Inhibitory Concentration 50% (IC50) value of ICD-85 for HeLa cells at 24 h was estimated and found to be 25.32±2.15 µg/mL. Furthermore, treatment of HeLa cells with ICD-85 at concentrations of 1.6×10 and 2.6×10 µg/mL did not significantly increase LDH release. Morphological changes in HeLa cells on treatment with ICD-85 compared with untreated HeLa cells consistent with an apoptotic mechanism of cell death, such as cell shrinkage which finally results in the generation of apoptotic bodies. However, when MRC-5 cells were exposed to ICD-85, no significant changes in cell morphology and LDH were observed at concentrations below 2.6×10µg/ml. Also, the apoptosis-induction mechanism by ICD-85 on HeLa cells was found through activation of caspase-8 and the activity of caspase-8 in HeLa cells was 1.5 folds more than its activity on MRC-5 cells. CONCLUSION Therefore, the apoptosis-induced mechanisms by ICD-85 are through activation of caspase-8 and concerning the least cytotoxic effect on MRC-5 cells, ICD-85 may be used as anticancer compound to inhibit growth of cancer cells.