JAEA-Review-2010-065.pdf:15.99MB - 日本原子力研究開発機構

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Combination Effect of the Heat Shock Protein
Inhibitor, 17-AAG, with Carbon-beam and X-ray
Irradiation for Squamous Cell Carcinomas in Vitro
A. Musha a, b) c) d) a) e) e)
, Y. Yoshida , T. Nonaka , T. Takahashi , T. Funayama , Y. Kobayashi ,
H. Ishikawa a) , H. Kawamura c) , K. Ando c) , S. Yokoo b) and T. Nakano a,c)
a) Department of Radiation Oncology, Graduate School of Medicine, Gunma University, b) Department
of Stomatology and Oral Surgery, Graduate School of Medicine, Gunma University,
c) Gunma University Heavy Ion Medical Center, d) Department of Radiation Therapeutics,
Kanagawa Cancer Center, e) Radiation-Applied Biology Division, QuBS, JAEA
Heat shock protein 90 (Hsp90) is a molecular chaperone that plays a critical role in cellular stress signaling pathways.
The Hsp90 inhibitor, 17- allylamino-17-demethoxygeldanamycin (17-AAG), binds to the ATP binding site of Hsp90 protein
and specifically inhibits its chaperone functions in tumor cells. We investigated whether 17-AAG has any
radio-sensitization effects in vitro. We used two squamous cell carcinoma cell lines, LMF4 (oral cancer cell line) and TE1
(esophageal cancer cell line). Cells were irradiated with a FAXITRON RX-650 X-ray machine at a dose rate 1.1~
1.3 Gy/min at Gunma University and irradiated with the broad beam of carbon particles by the AVF cyclotron of TIARA
(Takasaki Ion Accelerators for Advanced Radiation Application) at Japan Atomic Energy Agency, operating 18.3 MeV/u,
108 keV/m. Cells were treated with 100 nM 17-AAG for 24 hours before irradiation. Cell survival was measured by
colony formation assay. Specifically, cells were irradiated with X-ray (0-10 Gy) and irradiated with the broad beam of
carbon particles (0-4 Gy), trypsinized, diluted, counted, and seeded in 60-mm dishes at various cell densities. After 2 weeks
of incubation, colonies were stained with crystal violet. Survival curves for both cell lines treated with X-ray irradiation and
17-AAG demonstrated an additive effect. However, this radio-sensitization effect seen with X-ray irradiations was not seen
in the carbon beam irradiations. A radiation dose to reduce surviving fraction to 10% (D 10) was 7.09 Gy or 7.73 Gy for TE1
or LM4 cells, respectively. Furthermore, treatment of cells with carbon-beam irradiation reduced D0 values to 0.5 Gy and
0.6 Gy for TE1 and LM4 cells, respectively. RBE (Relative Biological Effectiveness) was 5.14 and 5.12 for TE1 cells and
LMF4 cells, respectively. Treatment of cells with 17-AAG alone reduced the surviving fraction to 0.6 and 0.7 in TE1 and
LMF4 cells, respectively. 17-AAG showed radio-sensitization in cell killing of the two squamous cell lines in the
X-irradiation. However, the carbon beam irradiation plus 17AAG treatment did not show a radio-sensitization effect.
These results suggest that Hsp90 may be an appropriate target for selectively enhancing the radio-sensitivity of tumor cells in
the X-irradiation. However, the carbon beam irradiation suggests that Hsp90 may not be an appropriate target for
selectively enhancing the radio-sensitivity of tumor cells. The carbon-beam irradiation treatment is more effective than
chemoradiotherapy for locoregional treatment.
【目的】熱ショックタンパク質 90(Hsp90)は多くの
腫瘍細胞で高発現しており、シグナル伝達で重要な役
割をもつ。Hsp90 阻害剤の 17-AAG とX線、炭素線の併
用による放射線増感効果について in vitro にて検討した。
【材料および方法】細胞は口腔扁平上皮癌細胞株 LMF4
と食道扁平上皮癌細胞株 TE1 を用いた。X線単独、炭
素線単独、ならびに 17-AAG 併用群において、コロニ
ー形成法により細胞生残率を解析した。併用群は
17-AAG を 24 時間接触後に照射を施行した。
【結果】生存率 10%となる線量(D 10)はX線単独が TE1
では 7.09 Gy、LMF4 では 7.73 Gy であり、X 線+17-AAG
はそれぞれ 4.49 Gy と 4.69 Gy であった。炭素線単独が
TE1 では 1.38 Gy、LMF4 では 1.51 Gy であり、炭素線
+17-AAG はそれぞれ 0.95 Gy と 1.32 Gy であった。X 線
では両細胞とも 17-AAG による放射線増感効果を示し
たが(Fig. 1)、炭素線では、顕著な増感効果は認められ
なかった(Fig. 2)。両細胞の RBE(Relative Biological
Effectiveness)は、TE1 では 5.14、LMF4 では 5.12 であった。
【結論】両細胞とも X線で認められた 17-AAG 併用に
よる増感効果は、炭素線では認められなかった。上記
の結果より、炭素線に比べ X 線において HSP90 に関連
した増感効果の機序が存在することが示唆された。
JAEA-Review 2010-065
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Fig. 1 Cell survival (X-ray irradiation).
HSP90 inhibitor 17-AAG radio-sensitizes two
squamous cell carcinoma cell lines (LMF4 and TE1).
Fig. 2 Cell survival (carbon beam irradiation).
Carbon-beam irradiation plus 17AAG treatment did not
show a radio-sensitization effect.