title: MAGE-A4 interacts with the liver oncoprotein gankyrin and suppresses its tumorigenic activity.
abstract: Hepatocellular carcinoma ranks among the most common malignancies in Southeast Asia and South Africa. Although there are many modalities of treatment, the recurrence and metastasis rates are high, and the prognosis is unsatisfactory. Gankyrin, a recently found oncoprotein, is a promising target for drug therapy because it is overexpressed in all studied hepatocellular carcinomas. Gankyrin contains six ankyrin repeats and interacts with Rb, Cdk4, and the S6 ATPase of the 26 S proteasome. In this study, a yeast two-hybrid screen with gankyrin has identified MAGE-A4 as another interacting protein. The interaction, mediated by the C-terminal half of MAGE-A4, was reproduced in mammalian cells. The interaction was specific to MAGE-A4, because other MAGE family proteins structurally similar to MAGE-A4, i.e. MAGE-A1, MAGE-A2, and MAGE-A12, did not bind to gankyrin. MAGE-A4 partially suppressed both anchorage-independent growth in vitro and tumor formation in athymic mice of gankyrin-overexpressing cells. The ability of mutant MAGE-A4 to interact with gankyrin correlated with the ability to suppress the anchorage-independent growth. These results demonstrate that MAGE-A4 binds to gankyrin and suppresses its oncogenic activity. So far, the major focus of studies on the MAGE proteins has been on their potential for cancer immunotherapy. Our results may also shed light on novel functions for MAGE-A proteins.
authors.affiliation: Department of Clinical Molecular Biology, Faculty of Medicine, Kyoto University, 54 Shogoin Kawaharacho, Sakyo-ku, Japan.
authors.forename: Toshikazu
authors.initials: T
authors.lastname: Nagao
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Higashitsuji
authors.forename: Kohsuke
authors.initials: K
authors.lastname: Nonoguchi
authors.forename: Toshiharu
authors.initials: T
authors.lastname: Sakurai
authors.forename: Simon
authors.initials: S
authors.lastname: Dawson
authors.forename: R John
authors.initials: RJ
authors.lastname: Mayer
authors.forename: Katsuhiko
authors.initials: K
authors.lastname: Itoh
authors.forename: Jun
authors.initials: J
authors.lastname: Fujita
mesh_terms: D016475:3T3 Cells; D000595:Amino Acid Sequence; D000818:Animals; D000951:Antigens, Neoplasm / Q000737:chemistry / Q000378:metabolism*; D002471:Cell Transformation, Neoplastic / Q000187:drug effects; D051358:Cyclin-Dependent Kinase 4; D018844:Cyclin-Dependent Kinases / Q000378:metabolism; D005260:Female; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D009363:Neoplasm Proteins; D009374:Neoplasms, Experimental / Q000517:prevention & control*; D015513:Oncogene Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex; D011518:Proto-Oncogene Proteins; D016160:Retinoblastoma Protein / Q000378:metabolism; D019893:Ribosomal Protein S6 Kinases / Q000378:metabolism
chemical_list: D000951:Antigens, Neoplasm; C095204:MAGEA4 protein, human; D009363:Neoplasm Proteins; D015513:Oncogene Proteins; C403591:PSMD10 protein, human; D011518:Proto-Oncogene Proteins; D016160:Retinoblastoma Protein; D019893:Ribosomal Protein S6 Kinases; C495902:Cdk4 protein, mouse; D051358:Cyclin-Dependent Kinase 4; D018844:Cyclin-Dependent Kinases; D046988:Proteasome Endopeptidase Complex