Delta-aminolevulinic acid as a photosensitizer precursor for the treatment of hepatoma cells in vitro

摘要

Abstract: Delta-aminolevulinic acid ($delta-ALA) has been recently proposed as a tumor photosensitizer precursor with increased selectivity and decreased toxicity for the treatment of neoplasms. We investigated the conversion and cytotoxicity of $delta-ALA in a human hepatoma cell line to determine its clinical potential. SK-HEP-1 (ATCC) cells were plated on 35 mm coverslips in media for use in a digital fluorescence microscopic imaging system. $delta-ALA was added to achieve final concentrations between 0-5 mM. Cells were excited with 450-490 nm light while a 610 nm long pass filter was used to assess fluorescence from conversion to protoporphyrin IX, the putative photosensitizer. After maximal fluorescence was obtained at each initial concentration of $delta-ALA, cells were radiated with 10 J/cm$+2 of light from a xenon lamp fitted with a 515 nm band pass filter. After photoradiation, cell death was assessed by flow cytometry using propidium iodide labeling. Protoporphyrin IX accumulation was constant at K$-s$/$EQ@0.001 until a plateau was achieved 2 hours after the addition of $delta-ALA. Photoradiation with 10 J/cm$+2 at a concentration of 1 mM $delta-ALA resulted in a linear increase in cell death over time with 5% cell death at 2 hours and 12% at 5 hours compared to controls. Interestingly, controls with $delta-ALA alone demonstrated a cytoprotective effect with a logarithmic relationship between increasing cell survival and increasing dose of drug. !13