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Proceedings Paper

Photodynamic therapy (PDT) as a biological modifier
Author(s): Modestus Obochi; Jing-Song Tao; David W. C. Hunt; Julia G. Levy
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Paper Abstract

The capacity of photosensitizers and light to ablate cancerous tissues and unwanted neovasculature constitutes the classical application of photodynamic therapy (PDT). Cell death results from either necrotic or apoptotic processes. The use of photosensitizers and light at doses which do not cause death has been found to affect changes in certain cell populations which profoundly effect their expression of cell surface molecules and secretion of cytokines, thereby altering the functional attributes of the treated cells. Cells of the immune system and the skin may be sensitive to modulation by 'sub-lethal PDT.' Ongoing studies have been conducted to assess, at the molecular level, changes in both lymphocytes and epidermal cells (EC) caused by treatment with low levels of benzoporphyrin derivative monoacid ring A (BPD) (a photosensitizer currently in clinical trials for cancer, psoriasis, endometriosis and age-related macular degeneration) and light. Treatment of skin with BPD and light, at levels which significantly enhanced the length of murine skin allograft acceptance, have been found to down-regulate the expression of Langerhans cell (LC) surface antigen molecules [major histocompatibility complex (MHC) class II and intracellular adhesion molecule (ICAM)-1] and the formation of some cytokines (tumor necrosis factor-alpha (TNF- (alpha) ).

Paper Details

Date Published: 2 April 1996
PDF: 10 pages
Proc. SPIE 2675, Optical Methods for Tumor Treatment and Detection: Mechanisms and Techniques in Photodynamic Therapy V, (2 April 1996); doi: 10.1117/12.237528
Show Author Affiliations
Modestus Obochi, QLT PhotoTherapeutics, Inc. (Canada)
Jing-Song Tao, QLT PhotoTherapeutics, Inc. (Canada)
David W. C. Hunt, QLT PhotoTherapeutics, Inc. (Canada)
Julia G. Levy, QLT PhotoTherapeutics, Inc. (Canada)

Published in SPIE Proceedings Vol. 2675:
Optical Methods for Tumor Treatment and Detection: Mechanisms and Techniques in Photodynamic Therapy V
Thomas J. Dougherty, Editor(s)

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