Effect of 5-Aminolevulinic Acid-mediated Photodynamic Therapy on Hep-2 and MCF-7c3 cells

M. G. ÁLVAREZ, M. S. LACELLI, V. RIVAROLA, H. FUKUDA, A. BATLLE

Salve Regina University, Newport, RI, USA,

Conferencia; Gordon Conferences Chemistry and Biology of Tetrapyrroles; 2006

Photodynamic therapy (PDT) is a novel cancer treatment receiving increased attention. PDT is a binary therapy involving the combination of visible light and a photosensitizer. Each component is harmless by itself, but, in combination with molecular oxygen, lead to the generation of singlet oxygen (1O2) and other reactive oxygen species (ROS), oxidative cell damage and cell death. 5-aminolevulinic acid (ALA) induced accumulation of protoporphyrin IX (PpIX) is a useful approach to the early detection and treatment of cancers. We evaluate the photodynamic effect of ALA on human larynx carcinoma (Hep-2) and human breast adenocarcinoma (MCF-7c3) cell lines, the latter stably transfected with human procaspase-3cDNA. Cell survival by means of MTT assay shows that in the absence of light ALA does not affect cell viability up to 1mM concentration in both cell lines. In contrast, the combination of ALA with visible light induces a decrease in cell survival that depends on the drug concentration and light dose. Morphologic analysis of MCF-7c3 cells performed with toluidine blue and Hoechst-33258, after incubation with 1mM ALA during 5 h and irradiation with 54 Jcm-2 light doses, revealed the typical morphological changes of necrosis 24 h post-PDT.  Instead, the same conditions applied to the Hep-2 cells produced chromatine fragmentation characteristic of apoptosis. These different mechanisms of cell death can be explained by the the difference in the pattern of PpIX accumulation: in Hep-2 cells fluorescence is confined into the lysosome, while in MCF-7c3 cells, in the nuclei. These results also confirm that the cell response to PDT is dependent on both the light dose and the cell type.