TY - JOUR AB - The radiosensitizing activity of celastrol, a quinone methide triterpene was examined. We found that celastrol treatment of the NCI-H460 lung cancer cell line increased radiation-induced cell killing. The increased radiosensitivity was correlated with decreased levels of Hsp90 clients, such as EGFR, ErbB2 and survivin as well as with increased p53 expression. Celastrol inhibited the ATP-binding activity of Hsp90. Furthermore, celastrol treatment dissociated an Hsp90 client protein, EGFR, and this in turn resulted in degradation of the client protein. These results were not observed with another structurally similar triterpenoid, 6β-acetonyl-22β-hydroxytingenol (TG), suggesting that a specific structural feature of the triterpenoid is required for radiosensitization. Moreover celastrol treatment increased p53 levels by phosphorylating Ser15 and Ser20 residues as well as by inhibiting its proteasomal degradation. Celastrol may be considered an effective radiosensitizer acting as an inhibitor of Hsp90 and a p53 activator. The two activities could be applicable to a broad range of cancer cells with either wild-type or mutant p53 because either activity could be effective for the enhancement of radiation cell killing. Further analysis with other triterpenoids should identify the functional moiety of the structure and additional candidates for effective radiosensitizers, which can be used in combined radiotherapy. AD - Laboratory of Modulation of Radiobiological Responses, Korea Institute of Radiological and Medical Sciences (KIRAMS), Seoul 139-706, Republic of Korea null Laboratory of Modulation of Radiobiological Responses, Korea Institute of Radiological and Medical Sciences (KIRAMS), 75 Nowon-gil, Nowon-gu, Seoul 139-706, Republic of Korea AU - Lee,Ji-Hyun AU - Choi,Kyu ,Jin AU - Seo,Woo ,Duck AU - Jang,Soon ,Young AU - Kim,Mira AU - Lee,Byong ,Won AU - Kim,Jun ,Young AU - Kang,Seongman AU - Park,Ki ,Hun AU - Lee,Yun-Sil AU - Bae,Sangwoo DA - 2011/03/01 DO - 10.3892/ijmm.2011.601 EP - 446 IS - 3 JO - Int J Mol Med KW - radiation sensitivity celastrol Hsp90 client proteins p53 PY - 2011 SN - 1107-3756 1791-244X SP - 441 ST - Enhancement of radiation sensitivity in lung cancer cells by celastrol is mediated by inhibition of Hsp90 T2 - International Journal of Molecular Medicine TI - Enhancement of radiation sensitivity in lung cancer cells by celastrol is mediated by inhibition of Hsp90 UR - https://doi.org/10.3892/ijmm.2011.601 VL - 27 ER -