Anticancer effects of fullerene [C60] included in polyethylene glycol combined with visible light irradiation through ROS generation and DNA fragmentation on fibrosarcoma cells with scarce cytotoxicity to normal fibroblasts

Abstract

Fullerene [C60] included in polyethylene glycol (PEG) at a composing ratio of 1:350 w/w was examined for anticancer effects upon photodynamic therapy (PDT). Human connective tissue-derived fibrosarcoma cells HT1080 were decreased for a viability of 50% or 30%, by 3-h administration with PEG-fullerene [C60] at 50 or 100 ppm fullerene [C60] equivalent, respectively, subsequent rinsing out and irradiation with visible light (400-600 nm, 140 J/cm2: 450-fold as intense as in average outdoor), whereas the same tissue type-derived normal fibroblastic cells DUMS16 retained a viability of 93% or 85% under the same conditions. Anticancer effects were dependent on PEG-fullerene [C60] concentrations and irradiation doses, and scarcely exerted by PEG-fullerene [C60] alone, irradiation alone, or by fullerene [C60]-free PEG combined with irradiation, suggesting that the active principle may be fullerene [C60] as small as 0.0028 wt% versus the whole compound. Irradiation with PEG-fullerene [C60] occurred in intracellular DNA fragmentation according to TUNEL assay, and produced reactive oxygen species (ROS) such as hydroperoxides and peroxyl radicals or superoxide anion radicals in HT1080 cells as demonstrated by CDCFH-DA assay or nitroblue tetrazolium assay, respectively. Thus, PEG-fullerene [C60] is expected to be applied to anticancer PDT with scarce side effects on normal cells.