Premium
5‐Aminolevulinic Acid–based Photochemical Internalization of the Immunotoxin MOC31‐gelonin Generates Synergistic Cytotoxic Effects In Vitro ¶
Author(s) -
Selbo Pål Kristian,
Kaalhus Olav,
Sivam Gowsala,
Berg Kristian
Publication year - 2001
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1562/0031-8655(2001)0740303aabpio2.0.co2
Subject(s) - immunotoxin , chemistry , endosome , acridine orange , protoporphyrin ix , internalization , endocytic cycle , microbiology and biotechnology , saporin , cytosol , biochemistry , cytotoxicity , in vitro , photodynamic therapy , endocytosis , biology , cell , apoptosis , organic chemistry , enzyme
Photochemical internalization (PCI) is a novel method for the endosomal or lysosomal release of membrane‐impermeable molecules into the cytosol of target cells. This novel technology is based on the photodynamically induced rupture of endocytic vesicles preloaded with molecules of therapeutic interest. PCI of the ribosome‐inactivating plant toxin gelonin and the immunotoxin monoclonal antibody 31 (MOC31)‐gelonin has been performed previously by the use of the endocytic vesicle–localizing photosensitizers TPPS 2a and AlPcS 2a and light, demonstrating synergistic toxicity against the more than 20 different cell lines tested, most of them of neoplastic origin. In this study we demonstrate that 5‐aminolevulinic acid (5‐ALA)–induced protoporphyrin IX (PpIX) is also capable of inducing PCI of MOC31‐gelonin in the human colon adenocarcinoma cell line WiDr. The cells were incubated with 1 m M 5‐ALA for up to 8 h in serum‐free medium and from 24 to 96 h in serum‐containing medium. Fluorescence microscopical studies indicate a partial plasma membrane localization of PpIX when 5‐ALA was applied under serum‐free conditions. This plasma membrane localization was not seen when 5‐ALA was given in the presence of serum. There was a granular component of the PpIX localization in addition to a diffuse cytoplasmic localization. The granular component resembled the localization of the fluorescent dye conjugate Alexa‐gelonin and the lysosomal localizing dye acridine orange. Our present results provide evidence for an endocytic vesicle–associated fraction of PpIX after 5‐ALA incubation of the WiDr cells. We demonstrate that PCI, by combining 5‐ALA, MOC31‐gelonin and light, induces a synergistic cytotoxic effect against the WiDr cells.