Premium
Effects of Combined Photodynamic Therapy and Ionizing Radiationon Human Glioma Spheroids ¶
Author(s) -
Madsen Steen J.,
Sun ChungHo,
Tromberg Bruce J.,
Yeh Alvin T.,
Sanchez Rogelio,
Hirschberg Henry
Publication year - 2002
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 - 10.1562/0031-8655(2002)0760411eocpta2.0.co2
Subject(s) - photodynamic therapy , glioma , spheroid , ionizing radiation , cancer research , non ionizing radiation , medicine , chemistry , irradiation , physics , optics , in vitro , biochemistry , organic chemistry , nuclear physics
The effects of combined photodynamic therapy (PDT) and ionizing radiation are studied in a human glioma spheroid model. The degree of interaction between the two modalities depends in a complex manner on factors such as PDT irradiation fluence, fluence rate and dose of ionizing radiation. It is shown that gamma radiation and PDT interact in a synergistic manner only if both light fluence and gamma radiation dose exceed approximately 25 J cm −2 and 8 Gy, respectively. Synergistic interactions are observed only for the lower fluence rate (25 mW cm −2 ) investigated. The degree of interaction appears to be independent of both sequence and the PDT or ionizing radiation time intervals investigated (1 and 24 h). Terminal deoxynucleotidyl transferase–mediated deoxyuridine triphosphate nick‐end labeling assays show that low‐fluence rate PDT is very efficient at inducing apoptotic cell death, whereas neither high‐fluence rate PDT nor ionizing radiation produces significant apoptosis. Although the mechanisms remain to be elucidated, the data imply that the observed synergism is likely not due to gamma‐induced cell cycle arrest or to PDT‐induced inhibition of DNA repair.