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  • Title: Effect of 5-aminolevulinic acid-mediated photodynamic therapy on MCF-7 and MCF-7/ADR cells.
    Author: Tsai T, Hong RL, Tsai JC, Lou PJ, Ling IF, Chen CT.
    Journal: Lasers Surg Med; 2004; 34(1):62-72. PubMed ID: 14755426.
    Abstract:
    BACKGROUND AND OBJECTIVES: Photodynamic therapy (PDT) has been proposed as an alternative approach in overcoming multidrug resistance (MDR) phenotype. To verify whether 5-aminolevulinic acid (ALA)-mediated PDT is effective in MDR cells, we studied the protoporphyrin IX (PpIX) content, intracellular localization, and phototoxicity in human breast cancer cells MCF-7 and derived MDR subline, MCF-7/ADR. STUDY DESIGN/MATERIALS AND METHODS: The fluorescence kinetics of ALA-induced PpIX was evaluated by spectrofluorometer. The phototoxicity of MCF-7 and MCF-7/ADR cells was determined by tetrazolium (MTT) assays and clonogenic assay. Furthermore, Annexin V and propidium iodide (PI) binding assays were performed to analyze the characteristics of cell death after ALA-PDT. RESULTS: MCF-7/ADR accumulated a lower level of PpIX as compared to parental MCF-7 cells. Significant phototoxicity was observed in MCF-7 and increased in a fluence-dependent manner with LD(50) around 8 J/cm(2). Compared to its parental counterpart, MCF-7/ADR cells were less sensitive to ALA photodynamic treatment and PDT-induced cytotoxicity did not increase in a dose responsive manner as the concentration of ALA increased or the fluence of light increased. ALA-PDT was less effective for MCF-7/ADR cells than MCF-7 cells even under the condition when these two cell lines contained the similar amounts of PpIX. CONCLUSIONS: These results indicate that, except for the MDR related characteristics, MCF-7/ADR cells might possess intrinsic mechanisms that render them less sensitive to ALA-PDT induced phototoxicity.
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