Characterisation of the cellular uptake, of 5-aminolevulinic acid.

Photodynamic therapy with 5-aminolevulinic acid (5-ALA) is a promising alternative treatment for several types of cancer. This work represents a first approach to characterise the transport system for 5-ALA in human cancer cells, using WiDr cells from a primary adenocarcinoma of the rectosigmoid colon as a model system. The transport of 5-ALA in WiDr was found to be dependent on pH and temperature, and partially inhibited by inhibitors of the energetic metabolism. Although WiDr was shown to express System A, a common transport system for small aliphatic amino acids, the transport of 5-ALA in WiDr was not found to be mediated by this system.