Vitamin E (α-tocopherol) enhances the PDT action of hematoporphyrin derivatives on cervical cancer cells

Abstract

Objective: The effect of antioxidant vitamin E (VE) on PDT (a mainly reactive oxygen species-driven process) has in the past shown contradicting results. Hence, we studied the effect of different concentrations and different incubation periods of VE on the PDT cytotoxicity of the cervical adenocarcinoma HeLa cell line. Materials and methods: HeLa cells were incubated with 25mg/ml of hematoporphyrin derivatives (HpD) for 25 min (1st PDT regimen) or 24 h (2nd PDT regimen), then irradiated with visible light (total light dose of 10 J/cm 2 ) either with or without different concentrations of VE (1–1000mM) which had been incubated with the cells for 1 h or 24 h prior to PDT. After irradiation, viability was measured using MTT assay. Results: The results obtained showed that PDT is effective against cervical cancer cells. Incubation of HpD for 24 h leads to improved PDT action. Higher concentrations of VE incubated in HeLa cells for 1 h before the 2nd PDT regimen significantly enhanced cytotoxicity of PDT and the maximal enhancement was at 1000mM of VE. The cytotoxic effect of VE on HeLa cells after incubation for 24 h before PDT is enhanced by the PDT action. Conclusion: In conclusion 1000mM of VE can be used 1 h before PDT to enhance its effect on cervical adenocarcinoma, a disease which is steadily increasing in young women. It is well-known that the cervical adenocarcinoma is resistant to anticancer agents and radiotherapy and it was previously considered to be HpD-PDT resistant.