Tsai, TsuiminTsuiminTsaiRUEY-LONG HONGJUI-CHANG TSAIPEI-JEN LOULing, I-FangI-FangLingChen, Chin-TinChin-TinChen2021-03-092021-03-0920040196-8092https://www.scopus.com/inward/record.uri?eid=2-s2.0-0347762872&doi=10.1002%2flsm.10246&partnerID=40&md5=e96ca3642a64983c6958f37bc569f1dbhttps://scholars.lib.ntu.edu.tw/handle/123456789/551264Background 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 LD50 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.[SDGs]SDG33 (4,5 dimethyl 2 thiazolyl) 2,5 diphenyltetrazolium bromide; aminolevulinic acid; lipocortin 5; propidium iodide; protoporphyrin; article; cell line; cell strain MCF 7; cellular distribution; clonogenic assay; controlled study; cytotoxicity; dose response; fluorescence; human; human cell; light; multidrug resistance; photodynamic therapy; photosensitivity; phototoxicity; priority journal; spectrofluorometry; Aminolevulinic Acid; Cell Death; Cell Line, Tumor; Humans; Mitochondria; Photochemotherapy; Photosensitizing Agentsjournal article10.1002/lsm.10246147554262-s2.0-0347762872