Evaluation of protoporphyrin IX production, phototoxicity and cell death pathway induced by hexylester of 5-aminolevulinic acid in Reh and HPB-ALL cells

Production of protoporphyrin IX (PpIX) in human B-cell leukemia cell line (Reh) and T-cell lymphoma cell line (HPB-ALL) was studied by flow cytometry after incubation with 5-aminolevulinic acid (ALA) or its hexylester in vitro. Cell survival and cell death pathway were also investigated in these two cell lines by cell growth curves, flow cytometry, and electron microscopy after ALA hexylester-mediated photodynamic therapy. Both ALA and its hexylester could induce PpIX production in the two cell lines, but ALA hexylester was about 100 times more efficient than ALA. Reh cells appear to be more sensitive than HPB-ALL cells to ALA hexylester-mediated phototoxicity. Apoptosis was the major cell death pathway of Reh cells, while necrosis played a major role in the case of HPB-ALL cells.