Lantadene A-induced apoptosis in human leukemia HL-60 cells

Objectives: Lantadene A (LA, 22β -angeloyloxy-3-oxoolean-12-en-28-oic acid) a pentacyclic, triterpenoid isolated from the leaves of the obnoxious weed, Lantana camara L. was evaluated for apoptosis induction in the human leukemia HL-60 cell line.
Materials and Methods : The effect of LA on cell proliferation of HL-60 cancer cells was determined by using the MTT assay. The morphological effects of LA-treated HL-60 cancer cells were observed under a fluorescence microscope. DNA fragmentation was observed using gel electrophoresis. Flow cytometry was carried out to observe changes in the cell cycle distribution of the cells. The expression of Bcl-2 and Bax proteins in HL-60 cells was visualized by means of an immunohistochemical assay and cell viability was determined upon treatment with DEVD-CHO (inhibitor of caspase-3) and LA.
Results : Typical morphological changes including cell shrinkage, chromatin condensation and characteristic DNA ladder formation in agarose gel electrophoresis were observed. LA-induced marked concentration- and time-dependent inhibition of cancer cell proliferation with an IC₅₀ value of 19.8 ± 0.10 µg/ml following 48 h incubation. Flow cytometric analysis showed suppressed cell proliferation associated with cell cycle arrest in the G₀ /G₁ phase. LA significantly inhibited cell proliferation of HL-60 cells and induced cell apoptosis by downregulating Bcl-2 and upregulating Bax expression. The peptidic caspase-3 inhibitor, DEVD-CHO (NH₂ -Asp-Glu-Val-Asp-CHO, 2 µM), increased the viability of HL-60 cells, which had been previously treated with LA.
Conclusions : The results indicated that LA induces efficient cell apoptosis by activating the caspase-3 pathway and through down- and upregulation of Bcl-2 and Bax expression respectively.