δ-aminolevulinic acid transport in murine mammary adenocarcinoma cells is mediated by beta transporters

delta-aminolevulinic acid, the precursor of porphyrin biosynthesis has been used to induce the endogenous synthesis of the photosensitiser protoporphyrin IX for photodynamic therapy in the treatment of various tumours. The aim of this work was to characterise the delta-aminolevulinic acid transport system in the murine mammary adenocarcinoma cell line LM3 using C-14-delta- aminolevulinic acid, to finally improve delta-aminolevulinic acid incorporation in mammalian cells. Our results showed that delta-aminolevulinic acid is incorporated into these cells by two different mechanisms, passive diffusion which is important at the beginning of the incubation, and active transport. Specificity assays suggested that the transporter involved in delta-aminolevulinic acid incorporation is a BETA transporter, probably GAT-2. (C) 2002 Cancer Research UK.