Abstract

Background

The study aimed to assess the effects of polyphenols when used in combination with doxorubicin and etoposide, and to determine whether polyphenols sensitised leukaemia cells, causing induction of apoptosis. Quercetin, apigenin, emodin, rhein and cis-stilbene were investigated alone and in combination with etoposide and doxorubicin in two lymphoid and two myeloid leukaemia cells lines.

Method

Measurements were made of ATP levels using CellTiter-Glo assay as an indication of total cell number, cell cycle progression using PI staining and flow cytometry, and apoptosis by NucView caspase 3 assay and Hoechst 33342/PI staining. Effects of combination treatments on caspases 3, 8 and 9 activity were determined using Glo luminescent assays, glutathione levels were measured using the GSH-Glo Glutathione Assay and DNA damage determined by anti-γH2AX staining.

Results

Doxorubicin and etoposide in combination with polyphenols synergistically reduced ATP levels, induced apoptosis and arrested S and/or G2/M phases in lymphoid cell lines. However, in the myeloid cell lines the effects of the combination treatments varied; doxorubicin had a synergistic or additive effect when combined with quercetin, apigenin, emodin, and cis-stilbene, but had an antagonistic effect when combined with rhein. Combination treatment caused a synergistic downregulation of glutathione levels and increased DNA damage, driving apoptosis via caspase 8 and 9 activation. However, in myeloid cells where antagonistic effects were observed, this was associated with increased glutathione levels and a reduction in DNA damage and apoptosis.

Conclusion

In conclusion, doxorubicin and etoposide activity can be enhanced by polyphenols, particularly in lymphoid leukaemia cells, although effects were strongly dependent on type of cell line, with some interactions were antagonistic in myeloid cell lines.