Hematoporphyrin monomethyl ether (HMME) is a novel and promising porphyrin-related photosensitizer for
photodynamic therapy (PDT). We use the human breast cancer MCF-7 cells to investigate the photodamage effect of
HMME and reactive oxygen species (ROS) generation in HMME-PDT. Methods: The growth rates of MCF-7 cells at 24h
after irradiation by 532nm laser with HMME of 5~20μg/ml and light dose of 0.3~4.8J/cm<sup>2</sup> were determined by CCK-8
assays. Hoechst33342 staining was used to investigate the morphological change of the tumor cell. Flow cytometry
combined with dual Annexin V/PI staining was used to identify the death mode of the cells following PDT. The changes of
ROS labeled by DCFH-DA were observed by Laser Scanning Confocal Microscopy (LSCM). Our results show that
HMME-based PDT induced significant cell death, and the photocytotoxity to MCF-7 cells is dose-dependent at the range
of HMME concentration 5~20μg/ml and the light dose 0.3~4.8J/cm<sup>2</sup>. The nucleolus underwent apoptosis and/or necrosis
observed by LSCM with Hoechst33342 staining. The necrosis and apoptosis rate were 16.0% and 12.4% respectively by
FCM, showing the number of necrosic cells was more than that of apoptosis. There was an intense increase of fluorescence
intensity standing for ROS generation within 30min post-PDT, and the peak was at about 10min after PDT. Our results
suggest that HMME-PDT could inhibit the proliferation of MCF-7 cells remarkably. Because the MCF-7 cells lack
procaspase-3, the apoptosis rate is lower. ROS played an important role in the photodamage with HMME.
<b>Objective </b>To study the effects of HMME-based photodynamic therapy on proliferation and apoptosis of rabbit
vascular smooth muscle cells(VSMCs). <b>Method</b> The cytotoxic effect of HMME-PDT on rabbit vascular smooth
muscle cells was studied by means of Trypan Blue assay, HMME at 10&mgr;g/ml concentration and the light dose at 2.4~4.8
J/cm<sup>2</sup> were selected in the studies. The morphological character 24h post-PDT was investigated by HE Staining.
Annexin V and propidium iodide (PI) binding assays were performed to analyze the characteristics of cell death after
HMME-PDT. Furthermore, The intracellular distributions of the HMME were measured by the confocal laser scanning
microscope. <b>Result</b> It was showed the photocytotoxity to VSMC cells was dose related by Trypan Blue assay.
Histology observing suggests HMME-PDT could induce cell death through apoptosis or necrosis, and the apoptosic rate
was up to 50.5% by AnnexinV /PI assay. Moreover, the fluorescence images of HMME intracellular localization
demonstrated that the HMME diffused into the mitochondria. <b>Conclusion</b> HMME-PDT could significantly inhibite
VSMC proliferation and induce apoptosis.