Rhodamine-123 as a new chemosensitizing versus toxic agent on human squamous carcinoma cells and fibroblast cultures.

Rhodamine-123 is a specific dye with an absorption maxima at 511 nm which was tested as a potential chemosensitizing agent for laser treatment of tumor cells. Because Rhodamine, at high doses, has direct cytotoxic effects on human cells in the absence of laser exposure, we tested the human squamous P 3 carcinoma cell line and two normal fibroblast cell lines for sensitivity to various levels of this dye. These cells were exposed to Rhodamine-123 at concentrations of 1, 3, 6, and 10 mug/ml for 1, 8, and 24 hours. The results indicate that Rhodamine-123 is nontoxic to human P 3 carcinoma cells and normal fibroblast cultures at concentrations equal or lower than 1 mug/ml. However, at concentrations equal or higher than 3 mug/ml, a significant immediate and/or delayed inhibition of cell duplication was demonstrated. The results show that Rhodamine-123 at 1 mug/ml can be used to sensitize tumor cells for targeting by monochromatic 514.5 nm Argon lasers.