Efficiency of 5-ALA mediated photodynamic therapy on hypoxic prostate cancer: a preclinical study on the Dunning R3327-AT2 rat tumor model.

OBJECTIVES: To evaluate photodynamic therapy (PDT) using 5-ALA-induced protoporphyrin IX (PPIX) in an in vivo hypoxic tumor model and its monitoring using MRI. MATERIAL AND METHODS: Dunning R3327-AT2 tumors were grafted in the neck of Copenhagen rats. PDT using 150 mg 5-ALA/kg i.v. was performed by focal interstitial illumination of the photosensitized tumor (λ=633 nm; fluence=100 J/cm(2)). MRI at baseline and 2 days after treatment (T1, T2 and dynamic gadolinium enhanced sequences) were performed. Necrosis volumes were determined on post-procedure MRI. Tumors were resected 2 days post-PDT and obtained necrosis was determined histopathologically. Intra-tumoral PPIX distribution was evaluated using confocal microscopy and tissue porphyrin quantification. RESULTS: Twenty rats were treated divided into three groups: continuous (n=7), fractionated illumination (n=7), and a control group receiving only light or only ALA or neither (n=6). Baseline MRI confirmed the hypoxic character of tumors. Necrosis volumes determined on posttreatment MRI were not reproducible and presented with important geometric and volumetric variability. Average necrosis volumes of 0.39 cc (0-0.874 cc) in the continuous group, 0.24 cc (0.107-0.436 cc) in the fractionated group and 0.012 cc (0-0.071 cc) in the control group were observed. Intra-tumoral PPIX distribution was heterogeneous and PPIX quantification revealed low intra-tumoral concentration. CONCLUSION: Necrosis volumes induced by 5-ALA-mediated PDT were highly variable and non reproducible, probably because of lack of intra-tissular oxygen. Photosensitizer was poorly represented inside the tumor and its distribution was heterogeneous. Our study suggests that 5-ALA-mediated PDT might not be the best management option for hypoxic prostatic adenocarcinoma.

[Transpupillary thermotherapy and age-related macular degeneration]. / Thermothérapie transpupillaire et dégénérescence maculaire liée à l'âge.

Transpupillary thermotherapy (TTT) has been proposed over the last a few years for the treatment of subfoveal occult choroidal neovessels resulting from age-related degeneration (AMD) when they are symptomatic and associated with exudation. Several pilot studies have shown how this technique can decrease or slow down the progression of exudation related to choroidal neovessels. Based on these pilot studies, a randomized study (TTT4CNV) is in progress to evaluate the efficacy of TTT. While the inclusion of the patients in this study has come to an end, the therapeutic context of AMD has recently been changed with a permit to market Visudyn for photodynamic therapy (PDT) for some types of subfoveal occult choroidal neovessels. Moreover, the clinical studies in progress on photodynamic therapy and antiangiogenic drugs now make it possible to consider combined treatments possibly including TTT. This paper aims to provide a report on the current place and potential of TTT within the therapeutics available or soon available for subfoveal occult choroidal neovessels of AMD.

Heat shock protein hyperexpression on chorioretinal layers after transpupillary thermotherapy.

PURPOSE: To assess a biological effect induced by temperature elevation during transpupillary thermotherapy (TTT). METHODS: Six pigmented rabbits were anesthetized, and TTT was performed on the right eye using an 810-nm diode laser installed on a slit lamp (spot size, 1.3 mm; duration, 60 seconds; power, 92-150 mW). A series of laser pulses were aimed at the posterior pole of the retina. The left eyes were used as the control. Twenty-four hours after laser irradiation, a histologic study was performed on the chorioretinal layers. Tissue samples were fixed in formalin and embedded in paraffin. A monoclonal antibody was used to detect heat shock protein (Hsp)70 immunoreactivity, followed by a biotinylated goat anti-mouse antibody, revealed by the avidin-biotin complex and the 3-amino-9-ethyl-carbazole (AEC) chromogen. Retinal structures were further identified by hematoxylin erythrosin saffron (HES) coloration. RESULTS: The photocoagulation threshold was found to be at the 150-mW laser power. Under this threshold, Hsp70 immunostaining was the strongest at the 127-mW power, with staining of some choroidal cells, including capillary endothelial cells. No Hsp70 immunoreactivity was observed on the retina. At the 107-mW power, Hsp70 reactivity was observed only in occasional choroidal cells. At the 98-mW power, only mild, diffuse Hsp70 immunoreactivity was observed in the choroid. At the 92-mW power, as in nonirradiated eyes, no Hsp70 immunoreactivity was detected. CONCLUSIONS: Subthreshold transpupillary 810-nm laser irradiation induces choroidal Hsp hyperexpression. This confirms that choroidal Hsp hyperexpression can be induced during TTT, as has been recently hypothesized by several investigators.

[Choroidal heat shock overexpression in transpupillary thermotherapy: preliminary results]. / Hyperexpression choroïdienne de Heat Shock Proteins au cours de la thermothérapie transpupillaire: résultats préliminaires.

PURPOSE: To assess retinochoroidal overexpression of heat shock proteins (HSP-70) induced by a transpupillary laser irradiation below the photocoagulation threshold. METHODS: Four pigmented rabbits were anesthetized and TTT was performed on the right eye using a 810nm diode laser (Iridis, Quantel-Medical, France) adapted on slit lamp (spot size: 1.3 mm, duration: 60 seconds; power 92-150 mW). Series of laser impacts were aimed at the posterior pole of the retina. Left eyes were used as control. Twenty-four hours after laser irradiation, a histological study was done on chorioretinal layers. Tissue samples were fixed in formalin and embedded in paraffin. A monoclonal antibody was used to detect HSP-70 immunoreactivity (mouse IgGl, SPA-810, Stress Gen, Canada), followed by a biotinylated goat antimouse antibody (Dako, Denmark), revealed by the avidin-biotin complex (Vectastain kit, Vector, USA) and the AEC chromogen. Retinal structures were further identified by HES coloration. RESULTS: The photocoagulation threshold was obtained for laser power at 150 mW. Under this threshold, HSP-70 immunostaining was the strongest for power 127 mW with a staining of some choroidal cells, including capillary endothelial cells. No HSP-70 immunoreactivity was observed on the retina. For the laser power 107 mW, HSP-70 reactivity was observed only in occasional choroidal cells. For the laser power 92 mW, as for nonirradiated eyes, no HSP-70 immunoreactivity was detected. CONCLUSIONS: Transpupillary 810 nm laser irradiation under the photocoagulation threshold induces choroidal HSP overexpression. This study concludes that choroidal HSP overexpression can be induced during TTT.