| Summary: | 碩士 === 長庚大學 === 基礎醫學研究所 === 89 === Photodynamic therapy (PDT) is one kind of photochemo-therapeutic treatment. It had been approved by FDA for treatment of some tumor. When cells uptake photosensitizers and exposed to specific wavelength of light, the photosensitizers can absorb the energy from photon and then transfer the energy to oxygen molecule to form reactive oxygen species (ROS), which can then induce cell death by intracellular signal transduction. Previous work from this laboratory had dissected the apoptotic signal pathway in human epidermal carcinoma A431 cell treated with PDT using Rose Bengal as photosensitizer (Chan et al., 2000). In this thesis, the death pathway of A431 cells treated with Photofrin®-PDT (a clinical PDT regime approved by FDA) was investigated. It was found that the effect of PDT on A431 cell is dependent on the dose of Photofrin®. PDT with low dose (3.5 mg/ml) Photofrin® had little effect on A431 cells. However, cell shrinkage and detachment from culture dish were observed following PDT with medium dose (7-14 mg/ml) Photofrin®. At high dose (28 mg/ml) Photofrin®, cell membrane disruption and cell swelling were detected immediately after PDT. The cell death process induced by high dose (28 mg/ml) Photofrin®-PDT was further studied in details. The results showed that Photofrin®-PDT can induce (i) ROS production, (ii) JNK and ERK phosphorylation/activation, (iii) PARP and PAK2 cleavage, and (iv) mitochondria membrane potential lost. Several scavengers for ROS and inhibitor for mitochondria MPT inhibitor were used to examine the cellular response to Photofrin®-PDT. It was found that, (i) Photofrin®-PDT-induced ROS production can’t be diminished even in the presence of mixed scavengers, and (ii) the MPT inhibitor can’t block Photofrin®-PDT-induced mitochondria membrane potential lost. In addition, the characteristics of typical apoptosis such as externalization of phosphatidylserine, caspase activation and DNA fragmentation can not be detected in the cell death process induced by Photofrin®-PDT. It is concluded that the type of death of A431 cells triggered by high dose (28 mg/ml) Photofrin®-PDT is necrosis but not apoptosis, which is distinctly different from that elicited by Rose Bengal-PDT.
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