Evaluation of the efficacy of aminolevulinic acid-dependent photodynamic therapy on melanoma cancer cells treated with tocopherol succinate (in-vitro)

Background: Photodynamic therapy (PDT) using 5-aminolevulinic acid (ALA) to produce an intracellular  photo-sensitizer, a protoporphyrin molecule IX (PPIX) which absorbs light and targets cells, is a promising cancer treatment. Unfortunately, treatment failures are still a common occurrence when ALA is used. In this study, in order to enhance the efficacy of ALA-dependent photodynamic therapy, the effects of photodynamic therapy on melanoma cancer cells were studied after treating them with tocopherol succinate.

Materials and Methods: In this experimental study melanoma cells were cultured in RPMI 1640 medium for 24 h. then, cells were treated with tocopherol succinate (6μm/ml). After 48 and 72 hours, the mediums were replaced by serum-free medium in the darkness, with ALA, 0.1mg/ml and then cells incubated for 4h. After that, cells were irradiated by using Nd: YAG laser (532 nm). After 24h, cell survival was measured by the MTT assay.

Results: Twenty-four hours after PDT, among compared groups, pretreated cells with tocopherol succinate showed significant lower cell viability than control group.

Conclusion: Induction of differentiation by using tocopherol succinate augmented intracellular PPIX accumulation in cells treated with ALA. Therefore phototoxic cell death after exposure to 532nm light enhances significantly in tocopherol succinate-pretreated cells. This study suggests that tocopherol succinate may act as a biological enhancer of ALA based photodynamic therapy.