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  • Title: Inhibition of HIF-1alpha by the anticancer drug TAS106 enhances X-ray-induced apoptosis in vitro and in vivo.
    Author: Yasui H, Ogura A, Asanuma T, Matsuda A, Kashiwakura I, Kuwabara M, Inanami O.
    Journal: Br J Cancer; 2008 Nov 04; 99(9):1442-52. PubMed ID: 18854835.
    Abstract:
    In a previous study, we showed that a novel anticancer drug, 1-(3-C-ethynyl-beta-D-ribo-pentofuranosyl)cytosine (TAS106, ECyd) increased the antitumour efficacy of X-irradiation. However, its effects on hypoxic cells in tumours remain unclarified. Here, we show that TAS106 enhances the induction of apoptosis in X-irradiated human gastric adenocarcinoma MKN45 and MKN28 cells under hypoxia in vitro. At the same time, the accumulation of HIF-1alpha observed under hypoxia was shown to be decreased to the level of normoxia in the presence of 0.1 microM TAS106. To study the function of HIF-1alpha protein in apoptosis of hypoxic cells, we employed an HIF-1alpha reductive approach using its specific antisense oligodeoxynucleotide. The reduction of HIF-1alpha gene expression dramatically enhanced X-ray-induced apoptosis in hypoxic cells. In in vivo experiments in which MKN45 cells were transplanted into severe combined immunodeficient (SCID) mice, TAS106 (0.5 mg kg(-1)) suppressed HIF-1alpha expression and subsequently reduced the area of the hypoxic region in the tumour and enhanced the induction of apoptosis in the hypoxic region when combined with 2 Gy of X-irradiation. These results suggest the possibility that TAS106 acts as a potent radiosensitiser through the inhibition of HIF-1alpha expression and can be a useful agent against radiotherapy-resistant hypoxic cells in solid tumours.
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