Enhanced cell death in NR-S1 tumor by photodynamic therapy: possible involvement of Fas and Fas ligand system.
OBJECTIVE
To investigate the effect of photodynamic therapy (PDT) on cell death in malignant tumor tissue, the frequency of terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL)-positive cells and the possible involvement of Fas and Fas ligand system were evaluated.


METHODS
NR-S1 tumor-bearing C3H/HeNCrj mice were treated by PDT with Photofrin(R) (12 mg/kg body weight) and Nd:YAG dye laser (630 nm, 10 Hz, 150 J/cm(2)). Paraffin-embedded tissue sections from the excised tumor tissues at 6, 12, 24, 48 hours after PDT were analyzed by TUNEL for the occurrence of apoptosis and by immunohistochemistry for Fas and Fas ligand (FasL) expression. TUNEL-positive cells as well as Fas- or FasL-positive cells were counted and expressed as a percentage of positive cells per total cells.


RESULTS
Based on the percent area of tumor necrotic foci, the most effective conditions for PDT were first determined. Under these conditions, PDT increased the number of TUNEL-positive tumor cells at 12 hours after irradiation. In parallel with the increase in TUNEL-positive cells, Fas-positive tumor cells were also found in the same area where many TUNEL-positive tumor cells were found. The expression of Fas ligand was found in the tumor cells surrounding TUNEL-positive cells on serial sections. A significant increase in FasL-positive lymphocytes was observed at 12 hours, whereas the infiltration of such lymphocytes into the area where TUNEL-positive tumor cells were observed was rare.


CONCLUSIONS
The possible role of Fas/FasL system in the cell death induced by PDT with Photofrin(R) and Nd:YAG dye laser was suggested. Moreover, the role of infiltrated lymphocytes seemed not to be so much in this model.
Yokota
T
T
Second Department of Oral and Maxillofacial Surgery, Nagasaki University School of Dentistry, Sakamoto, Nagasaki 852-8588, Japan. yokota@nova.dh.nagasaki-u.ac.jp
Ikeda
H
H
Inokuchi
T
T
Sano
K
K
Koji
T
T
D000818:Animals; D000954:Antigens, Surface / Q000378:metabolism; D017209:Apoptosis; D002294:Carcinoma, Squamous Cell / Q000378:metabolism* / Q000628:therapy*; D017323:Dihematoporphyrin Ether / Q000627:therapeutic use; D053222:Fas Ligand Protein; D007150:Immunohistochemistry; D020287:In Situ Nick-End Labeling; D053685:Laser Therapy; D008214:Lymphocytes / Q000378:metabolism; D008297:Male; D008562:Membrane Glycoproteins / Q000378:metabolism*; D051379:Mice; D008809:Mice, Inbred C3H; D009374:Neoplasms, Experimental / Q000378:metabolism / Q000628:therapy; D010778:Photochemotherapy / Q000379:methods; D017319:Photosensitizing Agents / Q000627:therapeutic use; D014407:Tumor Cells, Cultured / Q000378:metabolism; D019014:fas Receptor / Q000378:metabolism*
D000954:Antigens, Surface; D053222:Fas Ligand Protein; C505658:Fasl protein, mouse; D008562:Membrane Glycoproteins; D017319:Photosensitizing Agents; D019014:fas Receptor; D017323:Dihematoporphyrin Ether