A hydroxypyridinone (CP94) enhances protoporphyrin IX formation in 5-aminolaevulinic acid treated cells

Different cell lines were given photodynamic treatment with 5-aminolaevulinic acid (ALA) and light. In addition, the iron chelator 1,2-diethyl-3-hydroxypyridin-4-one (CP94) was used. The porphyrin species produced was spectrofluorimetrically identified as protoporphyrin IX. All the cell lines responded to treatment, including a multidrug resistance gene expressing bladder cancer line and, to a lesser degree, cells derived from untransformed human skin fibroblasts. CP94 enhanced both porphyrin fluorescence, total porphyrin content and photosensitivity of the cells. CCD fluorescence microscopy showed a granular extranuclear porphyrin fluorescence distribution for all the cell lines involved, but the untransformed cells showed a distribution pattern different from the ones seen in the other cells.