Berberine is a pure phenanthren alkaloid isolated from the roots and bark of herbal plants such as Berberis, Hydrastis canadensis and Coptis chinensis. Berberine has been established to inhibit the growth of breast cancer cells, but its effects on the drug resistance and anoikis-resistance of breast cancer cells have yet to be elucidated. Anoikis, or detachment-induced apoptosis, may prevent cancer progression and metastasis by blocking signals necessary for survival of localized cancer cells. Resistance to anoikis is regarded as a prerequisite for metastasis; however, little is known about the role of berberine in anoikis-resistance. We established anoikis-resistant cells from the breast cancer cell lines MCF-7 and MDA-MB-231 by culturing them on a Poly-Hema substratum. We then investigated the effects of berberine on the growth of these cells. The anoikis-resistant cells had a reduced growth rate and were more invasive than their respective adherent cell lines. The effect of berberine on growth was compared to that of doxorubicine, which is a drug commonly used to treat breast cancer, in both the adherent and anoikis-resistant cell lines. Berberine promoted the growth inhibition of anoikis-resistant cells to a greater extent than doxorubicine treatment. Treatment with berberine-induced cell cycle arrest at G0/G1 in the anoikis-resistant MCF-7 and MDA-MB-231 cells as compared to untreated control cells. In summary, these results revealed that berberine can efficiently inhibit growth by inducing cell cycle arrest in anoikis-resistant MCF-7 and MDA-MB-231 cells. Further analysis of these phenotypes is essential for understanding the effect of berberine on anoikis-resistant breast cancer cells, which would be relevant for the therapeutic targeting of breast cancer metastasis.
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