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Photodynamic therapy (PDT) is a well-described technique that is primarily used for thin and superficial tumors. Despite the advantages of immune response upregulation, high complete response rates and excellent cosmetics and preservation of tissue structure, the limited light penetration into tissue complicates achieving full-thickness/large-volume treatment of pigmented, thicker, deep-seated or diffuse metastatic tumors1. Reported in vitro studies in melanoma and breast cancer cells show increased expression of major histocompatibility complex I after the combination of psoralen and X-radiation, which is representative of a potential immune response upregulation2. The aim here is to investigate the clinical photosensitizer Verteporfin (VP) as a radiosensitizer to achieve deep tissue penetration while retaining immune upregulation, and thereby enhance tumor-specific radiation responses in pancreatic cancer3 and melanoma4, which are aggressive tumors with high metastatic potential and low survival rates. In vitro studies were carried out with bioluminescent human pancreatic cancer (Panc-1-Luc-2) and murine melanotic melanoma (B16F10) cell lines. The cells were irradiated using 225 kVp (XRAD) or 6 MeV (Linac) X-ray beams, and the treatment response was measured by clonogenicity. In all cases, the presence of VP in the cells reduced survival compared with X-ray only controls: e.g. the group irradiated in the Linac, which includes a contribution from VP activation by X-ray induced Cherenkov light, reached up to 5 Logs of cell death after a single fraction of 10 Gy. In the ex-ovo model, duck eggs at 8 days post fertilization were engrafted with 15 µL (∼5 × 107) of Panc-1-Luc-2 or B16F10-Luc cells. Treatment was given 3 days later using topical VP administration with irradiation 1.5 h later. Combining a single fraction of 5 Gy with 5 µg/mL VP gave >2-fold reduction of the bioluminescence compared to <1 fold for radiation alone. After 3 daily fractions, the in ovo tumors treated with VP + radiation showed undetectable bioluminescence signal until sacrificed at 2 d after the last fraction. These studies are intended primarily to generate baseline response data for radiodynamic therapy with different nanoparticle formulations, including both lipid-porphyrin porphysomes and metal nanoclusters. ACKNOWLEDGEMENTS This work is supported by the Canadian Institutes of Health Research, The Terry Fox research institute and a Tri-Council NRFR grant. L. Pires is supported by the Banting Fellowship. [ABSTRACT FROM AUTHOR]

Pythiosis is an infectious disease caused by Pythium insidiosum, a fungus-like organism. Due to the lack of ergosterol on its cell membrane, antibiotic therapy is ineffective. The conventional treatment is surgery, but lesion recurrence is frequent, requiring several resections or limb amputation. Photodynamic therapy uses photo-activation of drugs and has the potential to be an attractive alternative option. The in vitro PDT response on the growing of Pythium insidiosum culture was investigated using three distinct photosensitizers: methylene blue, Photogem, and Photodithazine. The photosensitizer distribution in cell structures and the PDT response for incubation times of 30, 60, and 120 minutes were evaluated. Methylene blue did not penetrate in the pathogen's cell and consequently there was no PDT inactivation. Photogem showed heterogenous distribution in the hyphal structure with small concentration inside the cells. Porphyrin-PDT response was heterogenous, death and live cells were observed in the treated culture. After 48 hours, hyphae regrowth was observed. Photodithazine showed more homogenous distribution inside the cell and with the specific intracellular localization dependent on incubation time. Photodithazine first accumulates in intracellular vacuoles, and at incubation times of one hour, it is located at all cell membranes. Higher inhibition of the growing rates was achieved with Photodithazine -PDT, over 98%. Our results showed that the photosensitizers that cross more efficiently the Pythium insidiosum membranes are able to cause extensive damage to the organism under illumination and therefore, are the best options for clinical treatment. [ABSTRACT FROM AUTHOR]

Radiodynamic therapy (RDT) is a recent extension of conventional photodynamic therapy, in which visible/near infrared light irradiation is replaced by a well-tolerated dose of high-energy X-rays. This enables greater tissue penetration to allow non-invasive treatment of large, deep-seated tumors. We report here the design and testing of a drug delivery system for RDT that is intended to enhance intra- or peri-nuclear localization of the photosensitizer, leading to DNA damage and resulting clonogenic cell kill. This comprises a photosensitizer (Verteporfin, VP) incorporated into poly (lactic-co-glycolic acid) nanoparticles (PLGA NPs) that are surface-functionalized with a cell-penetrating HIV trans-activator of transcription (TAT) peptide. In addition to a series of physical and photophysical characterization studies, cytotoxicity tests in pancreatic (PANC-1) cancer cells in vitro under 4 Gy X-ray exposure from a clinical 6 MV linear accelerator (LINAC) showed that TAT targeting of the nanoparticles markedly enhances the effectiveness of RDT treatment, particularly when assessed by a clonogenic, i.e., DNA damage-mediated, cell kill. [ABSTRACT FROM AUTHOR]

Background - Pythiosis is a life-threatening disease caused by Pythium insidiosum. Photodynamic therapy (PDT) is an alternative treatment to surgery that uses the interaction of a photosensitizer, light and molecular oxygen to cause cell death. Objectives - To evaluate the effect of PDT on the in vitro growth of P. insidiosum and in an in vivo model of pythiosis. Methods - For in vitro studies, two photosensitizers were evaluated: a haematoporphyrin derivative (Photogem®) and a chlorine (Photodithazine®). Amphotericin B was also evaluated, and the control group was treated with sterile saline solution. All experiments (PDT, porphyrin, chlorine and light alone, amphotericin B and saline solution) were performed as five replicates. For in vivo studies, six rabbits were inoculated with 20,000 zoospores of P. insidiosum, and an area of 1 cm3 was treated using the same sensitizers. The PDT irradiation was performed using a laser emitting at 660 nm and a fluence of 200 J/cm2. Rabbits were clinically evaluated daily and histopathological analysis was performed 72 h after PDT. Results - For in vitro assays, inhibition rates for PDT ranged from 60 to 100% and showed better results in comparison to amphotericin B. For the in vivo assays, after PDT, histological analysis of lesions showed a lack of infection up to 1 cm in depth. Conclusions and clinical importance - In vitro and in vivo studies showed that PDT was effective in the inactivation of P. insidiosum and may represent a new approach to treating pythiosis. [ABSTRACT FROM AUTHOR]