Geldanamycin and 17-allylamino-17-demethoxygeldanamycin potentiate the in vitro and in vivo radiation response of cervical tumor cells via the heat shock protein 90-mediated intracellular signaling and cytotoxicity.
Ansamycin antibiotics inhibit function of the heat shock protein (HSP) 90, causing selective degradation of several intracellular proteins regulating such processes as proliferation, cell cycle regulation, and prosurvival signaling cascades. HSP90 has been identified previously as a molecular target for anticancer agents, including ionizing radiation (IR). Therefore, we hypothesized that the ansamycin geldanamycin and its 17-allylamino-17-demethoxy analog (17-AAG), which inhibit HSP90, would enhance tumor cell susceptibility to the cytotoxicity of IR. Treatment of two human cervical carcinoma cell lines (HeLa and SiHa) with geldanamycin and 17-AAG resulted in cytotoxicity and, when combined with IR, enhanced the radiation response, each effect with a temporal range from 6 to 48 h after drug exposure. In addition, mouse in vivo models using 17-AAG at clinically achievable concentrations yielded results that paralleled the in vitro radiosensitization studies of both single and fractioned courses of irradiation. The increase in IR-induced cell death appears to be attributable to a combination of both programmed and nonprogrammed cell death. We also measured total levels of several prosurvival and apoptotic signaling proteins. Akt1, extracellular signal-regulated kinase-1, Glut-1, HER-2/neu, Lyn, cAMP-dependent protein kinase, Raf-1, and vascular endothelial growth factor expression were down-regulated in 17-AAG-treated cells, identifying these factors as molecular markers and potential therapeutic targets. Finally, a series of immortalized and human papillomavirus-transformed cell lines were used to demonstrate that the radiosensitizing effects of 17-AAG were limited to transformed cells, suggesting a possible differential cytotoxic effect. This work shows that altered HSP90 function induces significant tumor cytotoxicity and radiosensitization, suggesting a potential therapeutic utility.
Bisht
Kheem S
KS
Radiation Oncology Branch and. Radiation Biology Branch, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, Maryland 20892-1002, USA.
Bradbury
C Matthew
CM
Mattson
David
D
Kaushal
Aradhana
A
Sowers
Anastasia
A
Markovina
Stephanie
S
Ortiz
Karen L
KL
Sieck
Leah K
LK
Isaacs
Jennifer S
JS
Brechbiel
Martin W
MW
Mitchell
James B
JB
Neckers
Leonard M
LM
Gius
David
D
D000818:Animals; D000903:Antibiotics, Antineoplastic / Q000494:pharmacology*; D016227:Benzoquinones; D003131:Combined Modality Therapy; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D005260:Female; D018841:HSP90 Heat-Shock Proteins / Q000502:physiology*; D006367:HeLa Cells; D006801:Humans; D047029:Lactams, Macrocyclic; D051379:Mice; D008809:Mice, Inbred C3H; D008819:Mice, Nude; D011809:Quinones / Q000494:pharmacology*; D011838:Radiation-Sensitizing Agents / Q000494:pharmacology*; D017828:Rifabutin / Q000031:analogs & derivatives* / Q000494:pharmacology*; D015398:Signal Transduction / Q000187:drug effects; D002583:Uterine Cervical Neoplasms / Q000188:drug therapy* / Q000532:radiotherapy*; D023041:Xenograft Model Antitumor Assays
D000903:Antibiotics, Antineoplastic; D016227:Benzoquinones; D018841:HSP90 Heat-Shock Proteins; D047029:Lactams, Macrocyclic; D011809:Quinones; D011838:Radiation-Sensitizing Agents; D017828:Rifabutin; C112765:tanespimycin; C001277:geldanamycin