The radiosensitising effect of gemcitabine and its main metabolite dFdU under low oxygen conditions is in vitro not dependent on functional HIF-1 protein

• Published in: BMC cancer Vol. 14; no. 1; p. 594
• Main Authors: Wouters, An, Pauwels, Bea, Burrows, Natalie, Baay, Marc, Deschoolmeester, Vanessa, Vu, Trung Nghia, Laukens, Kris, Meijnders, Paul, Van Gestel, Dirk, Williams, Kaye J, Van den Weyngaert, Danielle, Vermorken, Jan B, Pauwels, Patrick, Peeters, Marc, Lardon, Filip
• Format: Journal Article
• Language: English
• Published: England BioMed Central 16.08.2014
• Subjects: Breast cancer; Breast Neoplasms; Cancer therapies; Cell culture; Cell cycle; Cell Cycle - drug effects; Cell Cycle - radiation effects; Cell Hypoxia - drug effects; Cell Hypoxia - radiation effects; Cell Line, Tumor; Cytotoxicity; Deoxycytidine - analogs & derivatives; Deoxycytidine - pharmacology; Deoxyribonucleic acid; Deoxyuridine - analogs & derivatives; Deoxyuridine - pharmacology; DNA; DNA repair; Female; Fluorides; Humans; Hypoxia; Hypoxia-Inducible Factor 1 - metabolism; Hypoxia-Inducible Factor 1, alpha Subunit - metabolism; In Vitro Techniques; Oxygen; Proteins; Radiation therapy; Radiation-Sensitizing Agents - pharmacology; Studies; Transcription factors; Tumors
• ISSN: 1471-2407; 1471-2407
• DOI: 10.1186/1471-2407-14-594

Regions within solid tumours often experience oxygen deprivation, which is associated with resistance to chemotherapy and irradiation. The aim of this study was to evaluate the radiosensitising effect of gemcitabine and its main metabolite dFdU under normoxia versus hypoxia and to determine whether hypoxia-inducible factor 1 (HIF-1) is involved in the radiosensitising mechanism. Stable expression of dominant negative HIF-1α (dnHIF) in MDA-MB-231 breast cancer cells, that ablated endogenous HIF-1 transcriptional activity, was validated by western blot and functionality was assessed by HIF-1α activity assay. Cells were exposed to varying oxygen environments and treated with gemcitabine or dFdU for 24 h, followed by irradiation. Clonogenicity was then assessed. Using radiosensitising conditions, cells were collected for cell cycle analysis. HIF-1 activity was significantly inhibited in cells stably expressing dnHIF. A clear radiosensitising effect under normoxia and hypoxia was observed for both gemcitabine and dFdU. No significant difference in radiobiological parameters between HIF-1 proficient and HIF-1 deficient MDA-MB-231 cells was demonstrated. For the first time, radiosensitisation by dFdU, the main metabolite of gemcitabine, was demonstrated under low oxygen conditions. No major role for functional HIF-1 protein in radiosensitisation by gemcitabine or dFdU could be shown.