Photodynamic therapy (PDT) is a clinically approved and ra pidly developing cancer treatment regimen, It is a minimally invasive procedure that requires the administration of a photosens iti zer foll owed by the illumination of the tumor with Iigh t of an appropriate wavelength, In the presence of molecular oxygen, cytotoxic intermedi a ries a re produced‘ thus damaging cellular structures containing the photosensitizer , In the present study. we exa mined the effectiveness of newly d evelped chlorin e6- induced PDT on malignant animal tumor model of 3prague-Da wley (3D) ra t Three-week-old male 3D rats we re inocula ted s ,c, on the right f1 ank with our previously esta blished k- ras-trans formed RK3E cell line (RK3E- ras. tota l, 5xl07 cell s) , The experiments were carried out 1 week after inoculation of tumor cell s , by which time the tumors had r eached about 0,7 mm to 1.0 cm in diameter, L3-chlorin e6 (L8 Pharm Co" Gwa ngju, Korea) was admin istrated intravenous ly by the tail vein of 3D rat at a dosage of 10 mg/kg after inhalation a nesthesia of ether, Twenty- four hours a fter L8-chlorin e6 ad ministration, PDT was pe rfol‘med using a laser diode (Geumgwang Co ‘ Ltd‘’ Daejeon, Korea) a t a light dose of 100 J /cm2 and wavelength of 664 nm, A..nimals were monitered daily and tumor volume was measured by calipel The tumor t reated with PDT using Ce6 had significant reduction in tumor s ize examined by gross tumor volume , softex x- ray image, molecular imaging a nalysis, respectively, PCNA immunostaining and TUNEL assay revealed that the treat ed tu mor caused signifi cant inlübition of tumor formati on with decreased tumor cell proliferation a nd increased a poptosis , Our dat a showed Ce6-induced PDT effecti vely arrested the tumor growth by inhibi t ing cell proliferation a nd inducing a poptosis , These findings provide the potential value of Ce6- induced PDT as an a lternative candidate for a nt i- tumor therapy, Furthel bi ochemical and cellular studies will reveal the precise molecul ar mecha ni sm of cell death induced by PDT