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Proceedings Paper

Lysosome vs. mitochondrion as photosensitizer binding site: how does the tortoise overtake the hare?
Author(s): Nancy L. Oleinick; Kashif Azizuddin; Song-mao Chiu; Sheeba Joseph; Myriam E. Rodriguez; Liang-yan Xue; Ping Zhang; Malcolm E. Kenney; Minh Lam; Anna-Liisa Nieminen
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Paper Abstract

Pc 4, a photosensitizer first synthesized at Case Western Reserve University and now in clinical trial at University Hospitals Case Medical Center, has been shown to bind preferentially and with high affinity to mitochondrial and endoplasmic reticulum membranes. Upon photoirradiation of Pc 4-loaded cells, membrane components, especially the anti-apoptotic protein Bcl-2, are photodamaged. Apoptosis, as indicated by activation of caspase-3 and cleavage of poly(ADP-ribose) polymerase, is triggered by the initial photodamage. A series of analogues of Pc 4 has been synthesized containing two axial ligands, one identical to the single ligand of Pc 4 and the other either the same as the Pc 4 ligand or bearing one or more hydroxyl groups. The hydroxyl-bearing axial ligands reduce the aggregation of the Pc in polar environments and direct the Pc's to lysosomes. Photoirradiation of cells that have taken up these Pc's into their lysosomes is 4-6 times more efficient at killing cells, as defined by loss of clonogenicity, than with Pc 4. Whereas PDT with Pc 4 photodamages Bcl-2 and Bcl-xL over the same dose response range as for cell killing, PDT with Pc 181 or the other lysosome-localizing Pc's causes much less photodamage to Bcl-2 relative to cell killing. Furthermore, in the case of the lysosome-bound Pc's, little or no caspase-3-dependent apoptosis is observed.

Paper Details

Date Published: 11 February 2008
PDF: 9 pages
Proc. SPIE 6845, Optical Methods for Tumor Treatment and Detection: Mechanisms and Techniques in Photodynamic Therapy XVII, 684505 (11 February 2008); doi: 10.1117/12.769226
Show Author Affiliations
Nancy L. Oleinick, Case Western Reserve Univ. (United States)
Kashif Azizuddin, Case Western Reserve Univ. (United States)
Song-mao Chiu, Case Western Reserve Univ. (United States)
Sheeba Joseph, Case Western Reserve Univ. (United States)
Myriam E. Rodriguez, Case Western Reserve Univ. (United States)
Liang-yan Xue, Case Western Reserve Univ. (United States)
Ping Zhang, Case Western Reserve Univ. (United States)
Malcolm E. Kenney, Case Western Reserve Univ. (United States)
Minh Lam, Case Western Reserve Univ. (United States)
Anna-Liisa Nieminen, Medical Univ. of South Carolina (United States)


Published in SPIE Proceedings Vol. 6845:
Optical Methods for Tumor Treatment and Detection: Mechanisms and Techniques in Photodynamic Therapy XVII
David Kessel, Editor(s)

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