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.
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.
Yang
Jun
J
Cancer Research UK Centre for Cancer Therapeutics, the Institute of Cancer Research, Surrey, United Kingdom.
Ahmed
Afshan
A
Poon
Evon
E
Perusinghe
Nina
N
de Haven Brandon
Alexis
A
Box
Gary
G
Valenti
Melanie
M
Eccles
Suzanne
S
Rouschop
Kasper
K
Wouters
Brad
B
Ashcroft
Margaret
M
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*
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