PURPOSE: Tumor hypoxia is unequivocally linked to poor radiotherapy outcome. This study aimed to identify enhancer sequences that respond maximally to a combination of radiation and hypoxia for use in genetic radiotherapy approaches. METHODS AND MATERIALS: The influence of radiation (5 Gy) and hypoxia (1% O2) on reporter-gene expression driven by hypoxia (HRE) and radiation (Egr-1) responsive elements was evaluated in tumor cells grown as monolayers or multicellular spheroids. Hypoxia-inducible factor-1alpha (HIF-1alpha) and HIF-2alpha protein expression was monitored in parallel. RESULTS: Of the sequences tested, an HRE from the phosphoglycerate kinase-1 gene (PGK-18[5+]) was maximally induced in response to hypoxia plus radiation in all 5 cell lines tested. The additional radiation treatment afforded a significant increase in the induction of PGK-18[5+] compared with hypoxia alone in 3 cell lines. HIF-1alpha/2alpha were induced by radiation but combined hypoxia/radiation treatment did not yield a further increase. The dual responsive nature of HREs was maintained when spheroids were irradiated after delivery of HRE constructs in a replication-deficient adenovirus. CONCLUSIONS: Hypoxia-responsive enhancer element sequences are dually responsive to combined radiation and hypoxic treatment. Their use in genetic radiotherapy in vivo could maximize expression in the most radio-resistant population at the time of radiation and also exploit microenvironmental changes after radiotherapy to yield additional switch-on.
PURPOSE: Tumor hypoxia is unequivocally linked to poor radiotherapy outcome. This study aimed to identify enhancer sequences that respond maximally to a combination of radiation and hypoxia for use in genetic radiotherapy approaches. METHODS AND MATERIALS: The influence of radiation (5 Gy) and hypoxia (1% O2) on reporter-gene expression driven by hypoxia (HRE) and radiation (Egr-1) responsive elements was evaluated in tumor cells grown as monolayers or multicellular spheroids. Hypoxia-inducible factor-1alpha (HIF-1alpha) and HIF-2alpha protein expression was monitored in parallel. RESULTS: Of the sequences tested, an HRE from the phosphoglycerate kinase-1 gene (PGK-18[5+]) was maximally induced in response to hypoxia plus radiation in all 5 cell lines tested. The additional radiation treatment afforded a significant increase in the induction of PGK-18[5+] compared with hypoxia alone in 3 cell lines. HIF-1alpha/2alpha were induced by radiation but combined hypoxia/radiation treatment did not yield a further increase. The dual responsive nature of HREs was maintained when spheroids were irradiated after delivery of HRE constructs in a replication-deficient adenovirus. CONCLUSIONS: Hypoxia-responsive enhancer element sequences are dually responsive to combined radiation and hypoxic treatment. Their use in genetic radiotherapy in vivo could maximize expression in the most radio-resistant population at the time of radiation and also exploit microenvironmental changes after radiotherapy to yield additional switch-on.
Authors: Suvobroto Nandi; Ilya V Ulasov; Matthew A Tyler; Adam Quasar Sugihara; Luciana Molinero; Yu Han; Zeng B Zhu; Maciej S Lesniak Journal: Cancer Res Date: 2008-07-15 Impact factor: 12.701
Authors: N Burrows; J Resch; R L Cowen; R von Wasielewski; C Hoang-Vu; C M West; K J Williams; G Brabant Journal: Endocr Relat Cancer Date: 2010-01-29 Impact factor: 5.678
Authors: Daniela Schilling; Christine Bayer; Anneke Geurts-Moespot; Fred C G J Sweep; Martin Pruschy; Karin Mengele; Lisa D Sprague; Michael Molls Journal: BMC Cancer Date: 2007-07-30 Impact factor: 4.430