Yoshinaga Kajimoto

Massive apoptotic cell death of human glioma cells via a mitochondrial pathway following 5-aminolevulinic acid-mediated photodynamic therapy

The basic mechanism of cell death induced by 5-aminolevulinic acid (5-ALA)-mediated photodynamic therapy (PDT) (ALA-PDT) in glioma cells has not been fully elucidated. In this study, the details of the cell death mechanism induced by ALA-PDT were investigated in three human glioma cell lines (U251MG, U87MG, and U118MG) in vitro. To evaluate the manner of accumulation of protoporphyrin IX (PpIX), intracellular PpIX contents were measured by flow cytometry after incubation with 5-ALA. To analyze the mechanism of cell death, U251MG cells were assayed by the terminal deoxynucleotidyl transferase-mediated dUTP-FITC nick end-labeling (TUNEL) method, and the caspase activity was measured after ALA-PDT. Furthermore, the mitochondrial membrane potential (MMP) and the release of mitochondrial cytochrome c were determined. PpIX fluorescence reached a plateau 4xa0h after exposure to 5-ALA. The proportion of dead cells increased with increases in the dosage of light. These cells were confirmed by TUNEL staining to be apoptotic. Increases in the activity of both caspase-3 and -9, a decrease in MMP, and a marked increase in cytochrome c in the cytosolic fraction were found after cells were subjected to PDT. These results indicate that a dysfunction of MMP is followed by mitochondrial cytochrome c release, which triggers apoptosis through a mitochondrial pathway. ALA-PDT induces massive apoptosis due to the direct activation of a mitochondrial pathway, which is resistant to many anti-apoptotic processes, in human glioma cells. This finding implies that ALA-PDT is a promising therapy for the treatment of apoptosis-reluctant tumors such as malignant gliomas.

Fiber-optic spectroscopic detection of neoplasm by intraoperative fluorescence labeling

Abstract Objective: Because the appearances of the neoplasm are frequently similar to the surrounding tissue, it is not necessarily easy to recognize the extent of tumor intra-operatively and to develop the tumor sensor. The purpose of this study is to develop the tumor identification system by application of fluorescence labeling method and spectroscopic analysis. Methods: Light for fluorescence excitation was radiated to the operative field. Fluorescent and reflected excitation lights were conducted to a spectrometer via optical fiber. The spectrum was analyzed in real time every 10 ms. To evaluate the probability of tumor existence, the intensity ratio of fluorescence peak to reflected excitation light was simultaneously calculated. For a preliminary examination, Fluorescein Na and 5 aminorevulinic acid (5-ALA) was administered to two patients with malignant brain tumor. The fluorescent intensity ratio was measured at tumor and brain tissue. Though the brain tissue showed little fluorescence, the spectrum of the tumor part contained fluorescence component. The high contrast ratios of tumor to normal brain fluorescence up to 5.6 in fluorescein Na and 160 in 5-ALA were observed. Conclusions: These results indicated that the neoplasm could be identified using fluorescence labeling method and spectroscopic analysis. The optical fiber type probe is so thin and time resolution is so high that it may be easily integrated with tumor resection apparatus. In conclusion, this system has great potential for tumor identification and resection.