Effects of HIF-1 inhibition by chetomin on hypoxia-related transcription and radiosensitivity in HT 1080 human fibrosarcoma cells.
BACKGROUND
Hypoxia-inducible factor-1 (HIF-1) overexpression has been linked to tumor progression and poor prognosis. We investigated whether targeting of HIF-1 using chetomin, a disrupter of the interaction of HIF-1 with the transcriptional coactivator p300, influences the radiosensitivity of hypoxic HT 1080 human fibrosarcoma cells.


METHODS
Optimal dose of chetomin was determined by EGFP-HRE gene reporter assay in stably transfected HT 1080 cells. Cells were assayed for expression of the hypoxia-inducible genes carbonic anhydrase 9 (CA9) and vascular endothelial growth factor (VEGF) by RT-PCR and for clonogenic survival after irradiation with 2, 5 or 10 Gy, under normoxic or hypoxic (0.1% O2, 12 h) conditions in the presence or absence of chetomin (150 nM, 12 h, pre-treatment of 4 h).


RESULTS
Chetomin treatment significantly reduced CA9 and VEGF mRNA expression in hypoxic cells to 44.4 +/- 7.2% and 39.6 +/- 16.0%, respectively, of untreated hypoxic controls. Chetomin clearly reduced the modified oxygen enhancement ratio (OER') compared to untreated cells, from 2.02 to 1.27, from 1.86 to 1.22 and from 1.49 to 1.06 at the 50%, 37% and 10% clonogenic survival levels, respectively.


CONCLUSIONS
HIF-1 inhibition by chetomin effectively reduces hypoxia-dependent transcription and radiosensitizes hypoxic HT 1080 human fibrosarcoma cells in vitro.
Staab
Adrian
A
Department of Radiation Oncology, University of Würzburg, 97080 Würzburg, Germany. staab_a@klinik.uni-wuerzburg.de
Loeffler
Jürgen
J
Said
Harun M
HM
Diehlmann
Désirée
D
Katzer
Astrid
A
Beyer
Melanie
M
Fleischer
Markus
M
Schwab
Franz
F
Baier
Kurt
K
Einsele
Hermann
H
Flentje
Michael
M
Vordermark
Dirk
D
D002256:Carbonic Anhydrases / Q000096:biosynthesis / Q000187:drug effects / Q000235:genetics; D015687:Cell Hypoxia / Q000502:physiology*; D045744:Cell Line, Tumor; D004220:Disulfides / Q000494:pharmacology*; D005354:Fibrosarcoma / Q000235:genetics / Q000378:metabolism*; D005434:Flow Cytometry; D015870:Gene Expression / Q000187:drug effects; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000187:drug effects*; D026121:Indole Alkaloids / Q000494:pharmacology*; D012333:RNA, Messenger / Q000032:analysis; D011836:Radiation Tolerance / Q000187:drug effects*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014158:Transcription, Genetic / Q000187:drug effects*; D042461:Vascular Endothelial Growth Factor A / Q000096:biosynthesis / Q000187:drug effects / Q000235:genetics
D004220:Disulfides; C497442:HIF1A protein, human; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D026121:Indole Alkaloids; D012333:RNA, Messenger; D042461:Vascular Endothelial Growth Factor A; C001598:chetomin; D002256:Carbonic Anhydrases