Comparison of
5-Aminolevulinic Acid and Its Hexylester
Mediated Photodynamic Action on Human Hepatoma Cells
REN Qing-Guang1,2, WU Su-Min1,3,
PENG Qian4, CHEN Ji-Yao1*
( 1Department of Physics, 2Analysis and Measurement
Center, ª¤
ª©ªªª¬ª©3State Key Laboratory of Applied Surface Physics, Fudan
University, Shanghai 200433, China;ª¤
ª©ªªª¬ª©4Department of Pathology, Institute for Cancer Research,
University of Oslo, Montebello, 0310 Oslo, Norway )
Abstract
5-Aminolevulinic acid (ALA) is a precursor to heme synthesis pathway and
currently used to induce endogenous protoporphyrin IX (PpIX, a potent
photosensitizer) for photodynamic therapy of cancer. ALA has, however, a
limited ability to cross cellular membranes due to its low lipid solubility.
The use of lipophilic ALA esters may increase cellular uptake, which results in
an enhanced PpIX synthesis. In the present study, a comparison of ALA and its
hexyl ester (He-ALA) was made in the QGY human hepatoma cell line with respect
to PpIX production and its photocytotoxicity. The fluorescence emission
spectrum of the cells incubated with He-ALA was identical to that of PpIX,
indicating that He-ALA could induce PpIX in the cells. Fluorescence images
demonstrated that the He-ALA induced PpIX was localized in the cytoplasm of the
cells. Moreover, a similar amount of Pp IX was found in the cells incubated
with 0.2 mmol/L He-ALA or 2 mmol/L ALA and a similar level of cell survival was
reached following light exposure. These results suggest that He-ALA is much
more efficient at producing PpIX and photocytotoxicity than ALA itself in the
cells.
Key words 5-aminolevulinic acid (ALA); protoporphyrin;
photosensitization
*Corresponding author£º Tel, 86-21-65642366; Fax,
86-21-65104949; e-mail, [email protected]