Superior Induction of Apoptosis by Blue Light Compared to Red Light Photodynamic Therapy in Cutaneous Squamous Cell Carcinoma Keratinocytes

This study compared apoptosis induction in squamous cell carcinoma keratinocytes following exposure to 5-aminolevulinic acid combined with either blue light (417 ± 5 nm) or red light (635 ± 5 nm) photodynamic therapy, with apoptotic activity quantified via levels of Annexin V expression. Our results demonstrated that blue light induces superior levels of apoptosis in squamous cell carcinoma keratinocytes compared to red light at the parameters tested. Both wavelengths demonstrate additional dose- and temperature-dependent effects across two squamous cell carcinoma cell lines. These conclusions had significant implications for the clinical selection of a light source in combination with 5-aminolevulinic acid photodynamic therapy in the treatment of actinic keratosis and early squamous cell carcinoma lesions.