The effects of argon lasers on human melanoma cells sensitized with rhodamine-123 in vitro.

A human melanoma cell line, M14, was first exposed to a nontoxic dose of Rhodamine-123 (1 microgram/ml) for one hour, then subjected to a treatment with a single mode argon laser at 514.5 nm. The temperature and energy levels delivered to the target cells were determined by a reproducible method of dosimetry. Cell viability was assessed by the Trypan Blue exclusion test. Cell duplication and DNA synthesis were measured by the incorporation of 3H-thymidine at 6 and 24 hours post-treatment. At energy levels and temperatures higher or equal to 950 J/cm2 (40 degrees C), an immediate suppression of DNA synthesis was accompanied by nonviability of the M14 carcinoma cells. At energy levels between 130-900J/cm2 corresponding to temperatures between 28 to 39 degrees C, both an immediate and delayed inhibition of DNA synthesis was noted but the cells remained viable. The results indicate that Rhodamine-123 at nontoxic doses of 1 microgram/ml enhances the tumoricidal effects of the argon laser at reduced temperatures as low as 40 degrees C. Furthermore, at physiological temperature ranges as low as 28 to 30 degrees C, an immediate inhibition of cell duplication was demonstrated while cell viability was not affected. These observations suggest that Rhodamine-123 can be used effectively as a chemosensitizing agent in the treatment of human tumor cells with the argon laser at 514.5 nm.