Antiproliferative and cytostatic effects of the natural product eupatorin on MDA-MB-468 human breast cancer cells due to CYP1 mediated metabolism

Vasilis P Androutsopoulos , Randolph RJ Arroo , John F Hall , Somchaiya Surichan and Gerry A Potter

Breast Cancer Research 2008, 10:R39doi:10.1186/bcr2090


Published:	2 May 2008

Abstract (provisional)

Background

The natural product eupatorin has been reported to have antiproliferative activity in tumor cell lines, but the exact mechanism is unclear. The cytochromes P450 CYP1B1, CYP1A1 and CYP1A2 have been shown to participate in the activation of various xenobiotics, compounds derived from the diet as well as chemotherapeutic drugs. CYP1B1 and CYP1A1 have also been proposed as targets for cancer chemotherapy for their differential and selective overexpression in tumor cells. In this study we aimed to identify a possible mechanism of action for the antiproliferative effect of eupatorin, which can be attributed to CYP1 family mediated metabolism.

Methods

The study focuses on the antiproliferative action of eupatorin on the human breast carcinoma cell line MDA-MB-468, and on a cell line derived from normal mammary tissue, MCF-10A. The cytotoxicity of the flavone, its effect on the cell cycle of the abovementioned cell lines, and its metabolism by CYP1 family enzymes were examined.

Results

Eupatorin showed a dose dependent inhibitory effect of cell growth on MDA-MB-468 cells with a sub-micromolar IC50 whereas the IC50 of this compound in MCF-10A cells was considerably higher. The antiproliferative effect was mainly attributed to CYP1A1 expression in MDA-MB-468 cells but not in MCF-10A cells, as measured by EROD assay and western immunoblotting. Moreover, CYP1 family enzymes were shown to metabolize eupatorin in vitro to the flavone cirsiliol and two other unidentified metabolites. Metabolism of eupatorin was also detected in MDA-MB-468 cell cultures, whereas metabolism by MCF-10A cells was negligible. Eupatorin was further shown to arrest the cell cycle of the CYP1-expressing cell line MDA-MB-468 in G2/M phase, whereas no effect was noticed in MCF-10A cells which do not express CYP1 enzymes. The effect of eupatorin on the MDA-MB-468 cell cycle could be reversed by co-application of the CYP1-inhibitor acacetin.

Conclusion

The flavone eupatorin is selectively activated in breast cancer cells, but not in normal breast cells, due to CYP1 family metabolism. This provides a basis for selectivity which is desired against breast tumor cells. In this sense, eupatorin is shown by this study to be a very promising chemopreventative candidate, which should be further examined in an in vivo study.