Aluminum phthalocyanine (AlPc) is a second-generation photosensitizer under study for photodynamic therapy (PDT) of cancer. Its mechanism of action is not known. Fluoride appears to be a powerful probe for the mechanistic study of AlPc derivatives. F^- forms a complex with the Al ligand, resulting in drastically reduced AlPc-induced phototoxicity. This is due to a modified binding of AlPc with certain target proteins, resulting in inhibition of electron transfer reactions (type I) but not singlet oxygen reactions (type II). In Chinese hamster ovary (CHO) cell membranes, Na⁺/K⁺-ATPase activity is selectively protected by F^- from photosensitized inhibition by AlPc, suggesting that this enzyme may be a critical target for AlPc-PDT. Another cellular response, not interfered with by F^-, is a transient increase of cytoplasmic free Ca²⁺ after AlPc-PDT. This increase was shown to trigger the induction of a recovery process.

Date Published: 1 March 1994
PDF: 5 pages
Proc. SPIE 2078, Photodynamic Therapy of Cancer, (1 March 1994); doi: 10.1117/12.168667

Published in SPIE Proceedings Vol. 2078:
Photodynamic Therapy of Cancer
Giulio Jori; Johan Moan; Willem M. Star, Editor(s)