Mitochondria-Targeted Photodynamic Therapy with a Galactodendritic Chlorin to Enhance Cell Death in Resistant Bladder Cancer Cells

Here, we report the rational design of a new third-generation photosensitizer (PS), a chlorin conjugated with galactodendritic units, ChlGal, to improve the effectiveness of bladder cancer treatment. ChlGal shows better photochemical and photophysical properties than a recently reported homologous porphyrin, PorGal. In addition to inheriting excellent photostability, the ability to generate singlet oxygen, and the ability to interact with the proteins galectin-1 and human serum albumin (HSA), ChlGal exhibits high absorption in the red region of the electromagnetic spectrum. In vitro studies of anticancer activity of ChlGal revealed that once this PS is taken up by UM-UC-3 bladder cancer cells, it induces high cytotoxicity after a single dose of light irradiation. In HT-1376 bladder cancer cells resistant to therapy, a second light irradiation treatment enhanced in vitro and in vivo photodynamic efficacy. The enhanced phototoxicity in HT-1376 cancer cells seems to be due to the ability of ChlGal to accumulate in the mitochondria, via facilitative glucose transporter 1 (GLUT1), in the period between single and repeated irradiation. A photodynamic therapy (PDT) regimen using an extra dose of light irradiation and ChlGal as PS represents a promising strategy in treating resistant cancers in a clinical setting.