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Enhancing the antitumoral effect of hypericin‐mediated photodynamic therapy by hyperthermia
Author(s) -
Chen Bin,
Roskams Tania,
de Witte Peter A.M.
Publication year - 2002
Publication title -
lasers in surgery and medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 112
eISSN - 1096-9101
pISSN - 0196-8092
DOI - 10.1002/lsm.10089
Subject(s) - hyperthermia , hypericin , photodynamic therapy , programmed cell death , apoptosis , in vivo , cancer research , cell , hyperthermia treatment , pathology , chemistry , medicine , pharmacology , biology , biochemistry , microbiology and biotechnology , organic chemistry
Background and Objectives In the previous study, we have found a synergistic effect on the RIF‐1 tumor cell killing when hypericin‐mediated photodynamic therapy (PDT) was combined with hyperthermia. The purpose of the present study was to investigate the antitumoral effect of hypericin‐PDT in combination with hyperthermia in the RIF‐1 mouse tumor model. Study Design/Materials and Methods Tumor response to PDT in combination with hyperthermia was compared to the response to PDT or hyperthermia alone. To explore the possible mechanism involved in the interaction of PDT and hyperthermia, we determined the tumor cell survival by in vivo/in vitro cell survival assay and analyzed the functional blood vessels by Hoechst 33342 staining. The mode of cell death was examined by TUNEL assay. Results Enhanced tumor response was obtained by PDT immediately followed by hyperthermia. Tumor cell survival assay revealed that indirect vascular effect contributed greatly to the overall tumor cell death induced by PDT with hypericin, whereas direct tumor cytotoxicity played a major role in hyperthermia‐induced tumor cell killing. Combining PDT with hyperthermia brought about a synergistic interaction on direct tumor cell killing. Even though PDT or hyperthermia alone induced severe blood vessel shutdown and the combined treatments led to significant potentiation of the vascular damage as examined by Hoechst staining, the gain in tumor cell death as a result of this secondary vascular effect was limited after the combined treatments. Following the cellular damage by PDT in combination with hyperthermia, tumor cells were triggered to undergo apoptosis. Conclusions Our study demonstrated the possibility of using hyperthermia to potentiate the antitumoral effect of hypericin‐mediated PDT. Lasers Surg. Med. 31:158–163, 2002. © 2002 Wiley‐Liss, Inc.