title: Small-molecule activation of p53 blocks hypoxia-inducible factor 1alpha and vascular endothelial growth factor expression in vivo and leads to tumor cell apoptosis in normoxia and hypoxia.
abstract: The p53 tumor suppressor protein negatively regulates hypoxia-inducible factor 1alpha (HIF-1alpha). Here, we show that induction of p53 by the small-molecule RITA (reactivation of p53 and induction of tumor cell apoptosis) [2,5-bis(5-hydroxymethyl-2-thienyl) furan] (NSC-652287) inhibits HIF-1alpha and vascular endothelial growth factor expression in vivo and induces significant tumor cell apoptosis in normoxia and hypoxia in p53-positive cells. RITA has been proposed to stabilize p53 by inhibiting the p53-HDM2 interaction. However, induction of p53 alone was insufficient to block HIF-1alpha induced in hypoxia and has previously been shown to require additional stimuli, such as DNA damage. Here, we identify a new mechanism of action for RITA: RITA activates a DNA damage response, resulting in phosphorylation of p53 and gammaH2AX in vivo. Unlike other DNA damage response-inducing agents, RITA treatment of cells induced a p53-dependent increase in phosphorylation of the alpha subunit of eukaryotic initiation factor 2, requiring PKR-like endoplasmic reticulum kinase activity, and led to the subsequent downregulation of HIF-1alpha and p53 target proteins, including HDM2 and p21. Through the identification of a new mechanism of action for RITA, our study uncovers a novel link between the DNA damage response-p53 pathway and the protein translational machinery.
authors.affiliation: Cancer Research UK Centre for Cancer Therapeutics, the Institute of Cancer Research, Surrey, United Kingdom.
authors.forename: Jun
authors.initials: J
authors.lastname: Yang
authors.forename: Afshan
authors.initials: A
authors.lastname: Ahmed
authors.forename: Evon
authors.initials: E
authors.lastname: Poon
authors.forename: Nina
authors.initials: N
authors.lastname: Perusinghe
authors.forename: Alexis
authors.initials: A
authors.lastname: de Haven Brandon
authors.forename: Gary
authors.initials: G
authors.lastname: Box
authors.forename: Melanie
authors.initials: M
authors.lastname: Valenti
authors.forename: Suzanne
authors.initials: S
authors.lastname: Eccles
authors.forename: Kasper
authors.initials: K
authors.lastname: Rouschop
authors.forename: Brad
authors.initials: B
authors.lastname: Wouters
authors.forename: Margaret
authors.initials: M
authors.lastname: Ashcroft
mesh_terms: D017209:Apoptosis; D015687:Cell Hypoxia; D045744:Cell Line, Tumor; D004249:DNA Damage; D004260:DNA Repair; D015852:Eukaryotic Initiation Factor-2 / Q000378:metabolism*; D005663:Furans / Q000494:pharmacology; D006657:Histones / Q000378:metabolism; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000037:antagonists & inhibitors*; D010766:Phosphorylation; D016159:Tumor Suppressor Protein p53 / Q000819:agonists / Q000502:physiology*; D042461:Vascular Endothelial Growth Factor A / Q000037:antagonists & inhibitors*
chemical_list: D015852:Eukaryotic Initiation Factor-2; D005663:Furans; C468783:H2AX protein, human; D006657:Histones; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D016159:Tumor Suppressor Protein p53; D042461:Vascular Endothelial Growth Factor A