BACKGROUND

Multidrug resistance (MDR) of breast cancer is a major obstacle in chemotherapy of cancer treatments. Recently the anti-tumor effects of Chlorin e6 (Ce6) mediated photodynamic therapy (Ce6-PDT) were reported in skin cancer and hepatoma in vitro. However, its therapeutic potential in killing human breast cancer especially those with MDR and the differences between MCF-7 and MCF-7/ADR after PDT treatment has not been fully investigated.

METHODS

MTT assay was used to measure cell survival rate of MCF-7 cells and MCF-7/ADR cells. Intracellular reactive oxygen species (ROS) generation was measured by monitoring the fluorescence intensity of dichlorofluorescein (DCF) by flow cytometry. Nuclear morphology changes and DNA damage in both MCF-7 and MCF-7/ADR after Ce6-PDT were analyzed by hochest33342 staining and comet assay. Western blot and monodansylcadaverine (MDC) staining were used to monitor autophagic response in MCF-7/ADR.

RESULTS

Ce6-PDT induced cell viability decrease, intracellular ROS generation, and DNA damage in concentration-dependent and cell-specific manner, and MCF-7 was more sensitive to Ce6-PDT than MCF-7/ADR cells at the same PDT condition. PDT treatment could trigger cell death via apoptosis in MCF-7 cells but autophagic cell death in MCF-7/ADR cells.

CONCLUSION

These results suggested that MCF-7 was more sensitive to Ce6-PDT than MCF-7/ADR, and PDT treatment could trigger apoptotic response in MCF-7 cells, but stimulate autophagic response in MCF-7/ADR cells.