High-intensity focused ultrasound induced apoptosis with caspase 3, 8, and 9/6 activation in rat hepatoma.
OBJECTIVE
The purpose of the present study is to investigate anticancer efficacy and apoptosis confirmed by caspase under several exposure conditions of high-intensity focused ultrasound (HIFU).


METHODS
Twenty-five rats with KDH-8 hepatoma were treated by HIFU at several acoustic energies to evaluate treatment efficacy. Apoptosis was examined by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) and Hoechst 33258 staining, and caspase 3, 8, and 9/6 activity was respectively assayed.


RESULTS
The KDH-8 subcutaneous tumors were reduced by HIFU, and these rats survived longer than the nontreatment rats (P < 0.01). The minimal threshold of HIFU energy was 30 W × 1.0 s for tumor control and long-term survival. The tumors exposed to HIFU exhibited marked apoptotic features under conditions of less than 10 W × 1.0 s. In cultured KDH-8 cells, apoptosis was caused at less than 30 W × 1.0 s (P < 0.01), and more was induced as the energy went down. Caspase 3, 8, and 9/6 were more activated at low energy under 10 W × 1.0 s (P < 0.01), and caspase 8, which is death receptor dependent, was significantly more activated than caspase 9/6, which is mitochondria dependent (P < 0.01).


CONCLUSIONS
HIFU-induced apoptosis in vivo and in vitro is one of the mechanisms for tumor control and is mediated by caspase 3, 8, and 9/6. The significantly greater activation of caspase 8 than of caspase 9/6 suggests that the apoptosis pathway induced by HIFU might be more mitochondria dependent than death receptor dependent. However, further examination will be needed.
Department of Radiology, School of Medicine, Sapporo Medical University, Minami-1, Nishi-16, Chuo-ku, Sapporo, 060-8543, Japan. nhirokaw@sapmed.ac.jp.
Naoki
N
Hirokawa
Department of Radiology, School of Medicine, Sapporo Medical University, Minami-1, Nishi-16, Chuo-ku, Sapporo, 060-8543, Japan.
Kazumitsu
K
Koito
Department of Biomolecular Function, Graduate School of Medicine, Yamagata University, Yamagata, 990-9585, Japan.
Futoshi
F
Okada
Laboratory of Biochemical Instrumentation & Measurements Research Associate, Graduate School of Engineering, Hokkaido University, Sapporo, 060-8628, Japan.
Nobuki
N
Kudo
Laboratory of Biochemical Instrumentation & Measurements Research Associate, Graduate School of Engineering, Hokkaido University, Sapporo, 060-8628, Japan.
Katsuyuki
K
Yamamoto
Toshiba Medical Systems Corporation, Ohtawara, 324-8550, Japan.
Katsuhiko
K
Fujimoto
Division of Clinical Laboratory and Transfusion Medicine, Hokkaido University Hospital, Sapporo, 060-8628, Japan.
Mutsumi
M
Nishida
Department of Radiology, School of Medicine, Sapporo Medical University, Minami-1, Nishi-16, Chuo-ku, Sapporo, 060-8543, Japan.
Takeshi
T
Ichimura
Department of Radiology, School of Medicine, Sapporo Medical University, Minami-1, Nishi-16, Chuo-ku, Sapporo, 060-8543, Japan.
Masakazu
M
Hori
Department of Radiology, School of Medicine, Sapporo Medical University, Minami-1, Nishi-16, Chuo-ku, Sapporo, 060-8543, Japan.
Taishi
T
Satoh
Department of Radiology, School of Medicine, Sapporo Medical University, Minami-1, Nishi-16, Chuo-ku, Sapporo, 060-8543, Japan.
Masato
M
Hareyama
Apoptosis; Caspase; Hepatoma; High-intensity focused ultrasound; KDH-8