[Fluorescence analysis of oral squamous cell carcinoma with 5-aminolevulinic acid labeling]

Photodynamic diagnosis (PDD) is a form of cancer detection based on the administration of an exogenous photoactivated compound that accumulates in malignant cells, followed by appropriate photo-irradiation. 5-aminolevulinic acid (5-ALA), which is one of these compounds, is a prodrug of the photosensitizer protoporphyrin IX (PpIX). This report describes a spectroscopic study of 5-ALA-generated PpIX fluorescence in human oral cancer cell lines. After transplanting five human oral squamous carcinoma cell lines into scid mice, the degree of tumor differentiation was evaluated by hematoxylin-and-eosin staining. Two, one, and two cell lines were poorly, moderately, and well differentiated, respectively. Under cell culture conditions, well and moderately differentiated cancer cells showed higher positive staining rates of AE1/AE3 than poorly differentiated ones in immunohistochemistry. 5-ALA-induced PpIX fluorescence intensities of five cell lines, which were cultured in Dulbecco's Modified Eagle's Medium (DMEM) treated with or without deferoxamine mesylate (DFO), were measured. In all cell lines, the maximum 5-ALA-generated fluorescence intensity was found in the presence of DFO. The fluorescence intensity varied with the degree of tumor differentiation in the following order: poorly differentiated, moderately differentiated, well differentiated. These results suggest that the fluorescence intensity of oral cancer cells differs according to the degree of tumor differentiation. However, even with well differentiated cancer cells, addition of DFO could increase the photodynamic sensitivity of 5-ALA as a result of greater cellular accumulation of PpIX.