Beta-sitosterol sensitizes MDA-MB-231 cells to TRAIL-induced apoptosis.
OBJECTIVE
To investigate whether subtoxic concentration of beta-sitosterol (SITO) combined with TNF-related apoptosis-inducing ligand (TRAIL) induces apoptosis in TRAIL-resistant MDA-MB-231 breast cancer cells.


METHODS
Cell viability and growth were assessed by 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphnyl-2H-tetrazolim bromide assays, chromatin condensation, release of lactate dehydrogenase (LDH), and Annexin V+ cells. The apoptosis-related proteins were detected by Western blotting.


RESULTS
Treatment with TRAIL in combination with subtoxic concentrations of SITO sensitized MDA-MB-231 breast cancer cells to TRAIL-mediated apoptosis. The synergistic treatment induced chromatin condensation, DNA fragmentation, the release of LDH, and Annexin V+ cells. The indicators of apoptosis are correlated to the induction of caspase activities, which results in the cleavage of poly(ADP-ribose)polymerase. Both the cytotoxic effects and apoptotic characteristics induced by the synergistic treatment were significantly inhibited by a pan-caspase inhibitor z-VAD-fmk, demonstrating the important role of caspases. These results indicate that caspases are crucial regulators of apoptosis induced by the combined treatment of SITO and TRAIL in MDA-MB-231 cells.


CONCLUSIONS
The synergistic treatment of SITO and TRAIL induces apoptosis, which can serve as a potential preventive and therapeutic agent.
Park
Cheol
C
Department of Biochemistry, Dongeui University College of Oriental Medicine, Busan 614-052, Korea.
Moon
Dong-oh
DO
Ryu
Chung-ho
CH
Choi
Byung tae
Bt
Lee
Won ho
Wh
Kim
Gi-young
GY
Choi
Yung hyun
Yh
D017304:Annexin A5 / Q000378:metabolism; D017209:Apoptosis / Q000187:drug effects*; D001943:Breast Neoplasms / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology*; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D005260:Female; D016650:Fluorescein-5-isothiocyanate / Q000378:metabolism; D005456:Fluorescent Dyes / Q000378:metabolism; D005562:Formazans / Q000378:metabolism; D006801:Humans; D000960:Hypolipidemic Agents / Q000494:pharmacology*; D012855:Sitosterols / Q000494:pharmacology*; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000494:pharmacology*; D013778:Tetrazolium Salts / Q000378:metabolism
D017304:Annexin A5; D005456:Fluorescent Dyes; D005562:Formazans; D000960:Hypolipidemic Agents; D012855:Sitosterols; D053221:TNF-Related Apoptosis-Inducing Ligand; C505653:TNFSF10 protein, human; D013778:Tetrazolium Salts; C079782:MTT formazan; C025473:gamma-sitosterol; D016650:Fluorescein-5-isothiocyanate