TY - JOUR
T1 - Combined inhibition of extracellular signal-regulated kinases and HSP90 sensitizes human colon carcinoma cells to ionizing radiation
AU - Kobayashi, Shinichiro
AU - Nantz, Regan
AU - Kitamura, Tetsuya
AU - Higashikubo, Ryuji
AU - Horikoshi, Nobuo
N1 - Funding Information:
We thank Drs David Gius and Michael Freeman for providing the materials used in this study. We thank Dr Hisashi Kurosawa for his generous support. We also thank Nicholle Johnson for her technical assistance. This work was supported by the Department of Radiation Oncology, Washington University School of Medicine, American Cancer Society RPG0029201, National Institute of Health P01CA104457, and R01CA98666 to NH.
PY - 2005/4/21
Y1 - 2005/4/21
N2 - Indomethacin, a common nonsteroidal anti-inflammatory drug, has been shown to enhance radiation-mediated cell-killing effect through the activation of p38 mitogen-activated protein kinase (MAPK). We found that indomethacin strongly reduced the basal level of extracellular signal-regulated kinases 1 and 2 (ERK1/2) in HT-29 human colon carcinoma cells. The inhibition of ERK1/2 by indomethacin was only observed in cells with high basal activities of ERK1/2 such as HT-29 cells, but not in cells with low basal activities, such as HeLa. Cell cycle analysis of HT-29 cells exposed with indomethacin showed a partial G1/S arrest and slow DNA synthesis. However, the treatment with NS398, a specific COX-1/2 inhibitor, failed to show any effect on cell cycle, indicating that the inhibition of COX-1/2 is not responsible for cell cycle arrest. Since U0126, a specific inhibitor for MEK1/2, also induced a partial G1/S arrest, the G1/S arrest induced by indomethacin is, at least in part, caused by the inhibition of ERK1/2. Cell proliferation of HT-29 was inhibited by the treatment of U0126 but not in HeLa cells, and the treatment of HT-29 cells with U0126 enhanced radiation sensitivity possibly due to the accumulation of cells in G1 phase. We found that 17-allylamino-17-demethoxygeldanamycin, a geldanamycin delivative, radiosensitized HT-29 cells at a relatively low dose of irradiation, and indomethacin and U0126 further enhanced this effect. Therefore, tumor cells with elevated ERK1/2 activity can be effectively sensitized to radiation treatment by a combinational inhibition of HSP90 and MAPK activity.
AB - Indomethacin, a common nonsteroidal anti-inflammatory drug, has been shown to enhance radiation-mediated cell-killing effect through the activation of p38 mitogen-activated protein kinase (MAPK). We found that indomethacin strongly reduced the basal level of extracellular signal-regulated kinases 1 and 2 (ERK1/2) in HT-29 human colon carcinoma cells. The inhibition of ERK1/2 by indomethacin was only observed in cells with high basal activities of ERK1/2 such as HT-29 cells, but not in cells with low basal activities, such as HeLa. Cell cycle analysis of HT-29 cells exposed with indomethacin showed a partial G1/S arrest and slow DNA synthesis. However, the treatment with NS398, a specific COX-1/2 inhibitor, failed to show any effect on cell cycle, indicating that the inhibition of COX-1/2 is not responsible for cell cycle arrest. Since U0126, a specific inhibitor for MEK1/2, also induced a partial G1/S arrest, the G1/S arrest induced by indomethacin is, at least in part, caused by the inhibition of ERK1/2. Cell proliferation of HT-29 was inhibited by the treatment of U0126 but not in HeLa cells, and the treatment of HT-29 cells with U0126 enhanced radiation sensitivity possibly due to the accumulation of cells in G1 phase. We found that 17-allylamino-17-demethoxygeldanamycin, a geldanamycin delivative, radiosensitized HT-29 cells at a relatively low dose of irradiation, and indomethacin and U0126 further enhanced this effect. Therefore, tumor cells with elevated ERK1/2 activity can be effectively sensitized to radiation treatment by a combinational inhibition of HSP90 and MAPK activity.
KW - HSP90
KW - MAP kinase
KW - Nonsteroidal anti-inflammatory drug
KW - Radiosensitization
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U2 - 10.1038/sj.onc.1208508
DO - 10.1038/sj.onc.1208508
M3 - Article
C2 - 15735687
AN - SCOPUS:18344368893
SN - 0950-9232
VL - 24
SP - 3011
EP - 3019
JO - Oncogene
JF - Oncogene
IS - 18
ER -