Combined xanthorrhizol-curcumin exhibits synergistic growth inhibitory activity via apoptosis induction in human breast cancer cells MDA-MB-231.
BACKGROUND
It has been suggested that combined effect of natural products may improve the treatment effectiveness in combating proliferation of cancer cells. The present study was undertaken to evaluate the possibility that the combination of xanthorrhizol and curcumin might show synergistic growth inhibitory effect towards MDA-MB-231 human breast cancer cells via apoptosis induction. The effective dose that produced 50% growth inhibition (GI50) was calculated from the log dose-response curve of fixed-combinations of xanthorrhizol and curcumin generated from the sulforhodamine B (SRB) assay. The experimental GI50 value was used to determine the synergistic activity of the combination treatment by isobolographic analysis and combination-index method. Further investigation of mode of cell death induced by the combination treatment was conducted in the present study.


RESULTS
Isobole analysis revealed that substances interaction was synergistic when xanthorrhizol and curcumin were added concurrently to the cultures but merely additive when they were added sequentially. The synergistic combination treatment was then applied to the cultures to investigate the mode of cell death induced by the treatment. Immunofluorescence staining using antibody MitoCapturetrade mark revealed the possibility of altered mitochondrial transmembrane potential, which is one of the hallmark of apoptosis. Hoechst 33258 nuclear staining assay showed the rate of apoptosis of MDA-MB-231 cells to increase in response to the treatment. Apoptotic cell death was further confirmed by DNA fragmentation assay, where internucleosomal excision of DNA was induced upon treatment with xanthorrhizol-curcumin.


CONCLUSIONS
This is the first time the combined cytotoxic effect of xanthorrhizol and curcumin on MDA-MB-231 cells has been documented and our findings provide experimental support to the hypothesis that combined xanthorrhizol-curcumin showed synergistic growth inhibitory activity on MDA-MB-231 cells via apoptosis induction.
Cheah
Yew Hoong
YH
Bioassay Unit, Herbal Medicine Research Center, Institute for Medical Research, Jalan Pahang, Kuala Lumpur, Malaysia.|School of Biosciences and Biotechnology, Faculty of Science and Technology, National University of Malaysia, 43600 UKM Bangi, Selangor, Malaysia.
Nordin
Fariza Juliana
FJ
Bioassay Unit, Herbal Medicine Research Center, Institute for Medical Research, Jalan Pahang, Kuala Lumpur, Malaysia.|School of Biosciences and Biotechnology, Faculty of Science and Technology, National University of Malaysia, 43600 UKM Bangi, Selangor, Malaysia.
Sarip
Rozie
R
Bioassay Unit, Herbal Medicine Research Center, Institute for Medical Research, Jalan Pahang, Kuala Lumpur, Malaysia.
Tee
Thiam Tsui
TT
School of Biosciences and Biotechnology, Faculty of Science and Technology, National University of Malaysia, 43600 UKM Bangi, Selangor, Malaysia.
Azimahtol
Hawariah Lope Pihie
HLP
School of Biosciences and Biotechnology, Faculty of Science and Technology, National University of Malaysia, 43600 UKM Bangi, Selangor, Malaysia.
Sirat
Hasnah M
HM
Department of Chemistry, Faculty of Science, Universiti Teknologi Malaysia, 80310 Skudai, Johor, Malaysia.
Rashid
Badrul Amini Abd
BAA
Phytochemistry Unit, Herbal Medicine Research Center, Institute for Medical Research, Jalan Pahang, Kuala Lumpur, Malaysia.
Abdullah
Noor Rain
NR
Bioassay Unit, Herbal Medicine Research Center, Institute for Medical Research, Jalan Pahang, Kuala Lumpur, Malaysia.
Ismail
Zakiah
Z
Bioassay Unit, Herbal Medicine Research Center, Institute for Medical Research, Jalan Pahang, Kuala Lumpur, Malaysia.