Pristimerin induces caspase-dependent apoptosis in MDA-MB-231 cells via direct effects on mitochondria.
Pristimerin, a naturally occurring triterpenoid, has been shown to cause cytotoxicity in several cancer cell lines. However, the mechanism for the cytotoxic effect of pristimerin was never explored. In the present study, human breast cancer MDA-MB-231 cells treated with pristimerin (1 and 3 micromol/L) showed rapid induction of apoptosis, as indicated by caspase activation, DNA fragmentation, and morphologic changes. Pretreatment of a pan-caspase inhibitor benzyloxycarbonyl-Val-Ala-Asp-fluoromethyl ketone (z-VAD-fmk) completely prevented pristimerin-induced apoptosis. Treatment of tumor cells with pristimerin resulted in a rapid release of cytochrome c from mitochondria, which preceded caspase activation and the decrease of mitochondrial membrane potential. In addition, neither benzyloxycarbonyl-Val-Ala-Asp-fluoromethyl ketone nor permeability transition pore inhibitor cyclosporin A markedly prevented pristimerin-induced mitochondrial cytochrome c release. Pristimerin did not significantly alter the protein level of Bcl-2 family members (Bcl-2, Bcl-X(L), and Bax), nor did it induce Bax translocation. Moreover, Bcl-2 overexpression fails to prevent pristimerin-induced apoptosis. The generation of reactive oxygen species in MDA-MB-231 cells was also not affected by pristimerin. In a cell-free system, pristimerin induced cytochrome c release from isolated mitochondria. Taken together, these results suggested that pristimerin is a novel mitochondria-targeted compound and may be further evaluated as a chemotherapeutic agent for human cancer.
Wu
Chin-Chung
CC
Graduate Institute of Natural Products, Kaohsiung Medical University, 100 Shin-Chuan 1st Road, Kaohsiung, Taiwan. ccwu@kmu.edu.tw
Chan
Mei-Ling
ML
Chen
Wen-Ying
WY
Tsai
Ching-Yi
CY
Chang
Fang-Rong
FR
Wu
Yang-Chang
YC
D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D000970:Antineoplastic Agents / Q000494:pharmacology / Q000627:therapeutic use*; D017209:Apoptosis; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000201:enzymology; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism*; D045304:Cytochromes c / Q000378:metabolism; D005260:Female; D006801:Humans; D007425:Intracellular Membranes / Q000187:drug effects / Q000378:metabolism; D008564:Membrane Potentials / Q000187:drug effects; D008928:Mitochondria / Q000187:drug effects*; D053978:Pentacyclic Triterpenes; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D014315:Triterpenes / Q000494:pharmacology / Q000627:therapeutic use*; D014407:Tumor Cells, Cultured
D000590:Amino Acid Chloromethyl Ketones; D000970:Antineoplastic Agents; D061945:Caspase Inhibitors; D053978:Pentacyclic Triterpenes; D019253:Proto-Oncogene Proteins c-bcl-2; D017382:Reactive Oxygen Species; D014315:Triterpenes; C096713:benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone; D045304:Cytochromes c; D020169:Caspases; C050414:celastrol