Melanoma antigen-11 inhibits the hypoxia-inducible factor prolyl hydroxylase 2 and activates hypoxic response.
Activation of hypoxia-inducible factors (HIF), responsible for tumor angiogenesis and glycolytic switch, is regulated by reduced oxygen availability. Normally, HIF-alpha proteins are maintained at low levels, controlled by site-specific hydroxylation carried out by HIF prolyl hydroxylases (PHD) and subsequent proteasomal degradation via the von Hippel-Lindau ubiquitin ligase. Using a yeast two-hybrid screen, we identified an interaction between melanoma antigen-11 (MAGE-11) cancer-testis antigen and the major HIF-alpha hydroxylating enzyme PHD2. The interaction was confirmed by a pull-down assay, coimmunoprecipitation, and colocalization in both normoxic and hypoxic conditions. Furthermore, MAGE-9, the closest homologue of MAGE-11, was also found to interact with PHD2. MAGE-11 inhibited PHD activity without affecting protein levels. This inhibition was accompanied by stabilization of ectopic or endogenous HIF-1alpha protein. Knockdown of MAGE-11 by small interfering RNA results in decreased hypoxic induction of HIF-1alpha and its target genes. Inhibition of PHD by MAGE-11, and following activation of HIFs, is a novel tumor-associated HIF regulatory mechanism. This finding provides new insights into the significance of MAGE expression in tumors and may provide valuable tools for therapeutic intervention because of the restricted expression of the MAGE gene family in cancers, but not in normal tissues.
Aprelikova
Olga
O
Laboratory of Tumor and Stem Cell Biology, National Cancer Institute, Bethesda, Maryland 20892, USA. apreliko@mail.nih.gov
Pandolfi
Silvia
S
Tackett
Sean
S
Ferreira
Mark
M
Salnikow
Konstantin
K
Ward
Yvona
Y
Risinger
John I
JI
Barrett
J Carl
JC
Niederhuber
John
J
D000595:Amino Acid Sequence; D000951:Antigens, Neoplasm / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D015687:Cell Hypoxia / Q000502:physiology; D045744:Cell Line, Tumor; D015536:Down-Regulation; D006367:HeLa Cells; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000096:biosynthesis; D064799:Hypoxia-Inducible Factor-Proline Dioxygenases; D008969:Molecular Sequence Data; D009363:Neoplasm Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D011393:Procollagen-Proline Dioxygenase / Q000037:antagonists & inhibitors* / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D034622:RNA Interference; D014158:Transcription, Genetic; D014162:Transfection; D025801:Ubiquitin / Q000378:metabolism
D000951:Antigens, Neoplasm; C497442:HIF1A protein, human; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; C110882:MAGEA11 protein, human; D009363:Neoplasm Proteins; D025801:Ubiquitin; C490190:EGLN1 protein, human; D011393:Procollagen-Proline Dioxygenase; D064799:Hypoxia-Inducible Factor-Proline Dioxygenases; D046988:Proteasome Endopeptidase Complex