Synergistic increase in osteosarcoma cell sensitivity to photodynamic therapy with aminolevulinic acid hexyl ester in the presence of hyperthermia.
OBJECTIVE
We observed that two osteosarcoma cell lines from the same tumor displayed marked differences in their sensitivities to photodynamic therapy (PDT) with aminolevulinic acid hexyl ester (hALA-PDT). We investigated why these two closely related lines had different hALA-PDT sensitivities and whether the PDT phototoxicity of the less sensitive cell line could be increased by a simultaneous application of hyperthermia (HT).


METHODS
Flow cytometry was used to evaluate the intracellular accumulation of protoporphyrin IX (PpIX), a metabolic product of aminolevulinic acid, in two human mandibular osteosarcoma cell lines (HOSM-1 and HOSM-2) treated with HT, hALA-PDT, or hALA-PDT combined with HT (PDT + HT). With hALA-PDT, cells treated with 0.2 mM hALA were irradiated with a light dose of 10-80 J/cm(2) from a near-infrared irradiator. With PDT + HT, the cells were treated as for hALA-PDT except that the temperature was raised to 43.5 degrees C during irradiation.


RESULTS
At 6 h after hALA treatment, HOSM-2 cells carried about 1.53-fold more PpIX than HOSM-1 cells. With hALA-PDT, the survival rate for HOSM-1 cells treated with 80 J/cm(2) irradiation was 35.7%, while that for HOSM-2 cells treated with 40-80 J/cm(2) was below 12%. With PDT + HT, the survival rate for HOSM-1 and HOSM-2 cells treated with 80 J/cm(2) irradiation was 14.1% and 10.7%, respectively.


CONCLUSIONS
A combination therapy comprising hALA-PDT + HT treatment may be very useful for the treatment of tumors containing cells that are insensitive to hALA-PDT, such as the HOSM-1 cell line described in this study.
Yanase
Shigeaki
S
Department of Oral and Maxillofacial Surgery, Division of Reparative and Regenerative Medicine, Mie University Graduate School of Medicine, Tsu, Mie, Japan. shigeaki@clin.medic.mie-u.ac.jp
Nomura
Jouji
J
Matsumura
Yoshihiko
Y
Watanabe
Yoshihiro
Y
Tagawa
Toshiro
T
D000622:Aminolevulinic Acid / Q000031:analogs & derivatives* / Q000494:pharmacology; D045744:Cell Line, Tumor / Q000187:drug effects; D003131:Combined Modality Therapy; D006801:Humans; D006979:Hyperthermia, Induced; D007259:Infrared Rays; D008339:Mandibular Neoplasms / Q000737:chemistry / Q000188:drug therapy*; D012516:Osteosarcoma / Q000737:chemistry / Q000188:drug therapy*; D010778:Photochemotherapy; D017319:Photosensitizing Agents / Q000494:pharmacology*; D011524:Protoporphyrins / Q000032:analysis
D017319:Photosensitizing Agents; D011524:Protoporphyrins; D000622:Aminolevulinic Acid; C028025:protoporphyrin IX; C419924:5-aminolevulinic acid hexyl ester