Thioredoxin upregulation by 5‐aminolaevulinic acid‐based photodynamic therapy in human skin squamous cell carcinoma cell line

Abstract

5-aminolaevulinic acid-based photodynamic therapy (ALA-PDT) is widely performed in the clinical setting for superficial skin cancers, giving favorable results, but residual tumor and recurrence occur occasionally. Thioredoxin is a common antioxidant that suppresses apoptosis and facilitates cell growth. We investigated the expression of thioredoxin following ALA-PDT in human skin squamous cell carcinoma cell line, HSC-5. ALA-PDT was performed in HSC-5 cells using low-dose (5 J/cm(2), 100 mW/cm(2)) or high-dose (30 J/cm(2), 100 mW/cm(2)) irradiation, and the expression of thioredoxin was measured by Western blotting. An MTT assay was used to assess cell growth following a low dose of multiple irradiations. Cell death was examined by Western blotting for caspase-3 and PARP. Immunofluorescence double staining using annexin V and propidium iodine was also performed. Expression of thioredoxin was only observed following low-dose exposure ALA-PDT. Multiple low-dose exposure ALA-PDT significantly proliferated cell growth. With high-dose exposure ALA-PDT, caspase-3 and PARP expression were seen, and cell death due to apoptosis and/or necrosis was observed, but thioredoxin was barely detected. Low-dose exposure ALA-PDT increased the expression of thioredoxin and facilitated the growth of HSC-5 cells.