2002 年 23 巻 1 号 p. 1-10
Fluorescence diagnosis is a form of cancer detection based on the administration of a photosensitizer, the subsequent exposure of the tissue to light of a specific wavelength and the detection of a characteristic fluorescence. 5-aminolevulinic acid (ALA) is not a photosensitizer but the natural precursor to photosensitizer protoporphyrin IX (PpIX). We have reported PpIX fluorescence in mouse NR-S1 squamous cell carcinoma of the tongue after oral administration of ALA (400mg kg-1) in a spectroscopic study. The aim of this study is to investigate the accumulation of ALA-induced PpIX to tumors, normal tissue, cancer cells and normal cells. Confocal laser scanning microscopic (CLSM) observation of ALA-induced PpIX was carried out at the tissular and cellular level. Strong PpIX fluorescence was revealed in the tumor tissue, clearly demonstrating the demarcation of the tumor and the normal tissues. In the normal tissues, PpIX fluorescence was pronounced in the epithelial layer, whereas no PpIX fluorescence was detected in the submucosa or muscle layer. In a study of cultured cells treated by ALA, tumor cells indicated heterogeneous distribution of intense PpIX fluorescence in the cytoplasm with nuclear exclusion, while weak PpIX fluorescence was detected in normal cells. CLSM imaging indicates that ALA-induced PpIX accumulates in the malignant tissue and cancer cells compared with normal tissue and cells. The present study supports our previous spectroscopic study.
