Rhodamine 123 as a Chemosensitizing Agent for Argon Laser Therapy: A New Technique for Treatment of Superficial Malignancies

Abstract

• Rhodamine 123 (Rh 123), a mitochondrial-specific dye with an absorption maxima at 511 nm, was tested as a new chemosensitizing agent for argon laser treatment of P₃ human squamous carcinoma cells. After exposure of P₃ cells in vitro to Rh 123 at doses of 1, 3, 6, and 10 μg/mL for one hour, we observed significant inhibition of DNA synthesis, except at the lowest dose. Rhodamine 123 at 1 μg/mL was selected to sensitize P₃ tumor cells for treatment with the monochromatic argon laser at 514.5 nm. Exposure of P₃ cells to laser energy levels of 700 to 950 J/cm² (36°C to 40°C after sensitization with Rh 123 completely inhibited tumor development of the P₃ cells transplanted subcutaneously into nude mice. Control P₃ cells treated with the laser alone at 36°C to 40°C or only with Rh 123 formed visible tumors by one week and continued to grow for the entire-week observation period. These results show that Rh 123 is a highly sensitive new fluorochrome for argon laser phototherapy of human squamous carcinoma cells. (Arch Otolaryngol Head Neck Surg 1987;113:1176-1182)