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MECHANISMS BEHIND THE RESISTANCE OF SPHEROIDS TO PHOTODYNAMIC TREATMENT: A FLOW CYTOMETRY STUDY
Author(s) -
West Catharine M. L.,
Moore James V.
Publication year - 1992
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1992.tb04257.x
Subject(s) - spheroid , hematoporphyrin , flow cytometry , photodynamic therapy , cell , biophysics , cell culture , fluorescence , chemistry , biology , in vitro , microbiology and biotechnology , biochemistry , optics , genetics , physics , organic chemistry
— The influence of cell heterogeneity on response to photodynamic treatment (PDT) has been investigated using the human colon adenocarcinoma line WiDr, grown as spheroids and exposed to hematoporphyrin derivative. The spheroids show a marked spheroid size‐dependent resistance to PDT. Using a flow cytometer, cell sub‐populations have been separated, on the basis of drug fluorescence, from single cell suspensions prepared from 500 μm diameter spheroids. Cells low in fluorescence have been shown to be resistant to PDT, have a smaller median cell volume, and be enhanced in G 1 ‐type cells. These cells also show reduced low density lipoprotein uptake. The results suggest that spheroid size‐dependent resistance to PDT is related to a decreasing growth fraction with increasing spheroid size. Heterogeneity of drug uptake could be a potential limitation to clinical PDT.