Abstract
The retinoblastoma binding protein RBP2 (KDM5A) is a histone demethylase that promotes gastric cancer cell growth and is enriched in drug-resistant lung cancer cells. In tumor-prone mice lacking the tumor suppressor gene RB or MEN1, genetic ablation of RBP2 can suppress tumor initiation, but the pathogenic breadth and mechanistic aspects of this effect relative to human tumors have not been defined. Here, we approached this question in the context of lung cancer. RBP2 was overexpressed in human lung cancer tissues where its depletion impaired cell proliferation, motility, migration, invasion, and metastasis. RBP2 oncogenicity relied on its demethylase and DNA-binding activities. RBP2 upregulated expression of cyclins D1 and E1 while suppressing the expression of cyclin-dependent kinase inhibitor p27 (CDKN1B), each contributing to RBP2-mediated cell proliferation. Expression microarray analyses revealed that RBP2 promoted expression of integrin-β1 (ITGB1), which is implicated in lung cancer metastasis. Mechanistic investigations established that RBP2 bound directly to the p27, cyclin D1, and ITGB1 promoters and that exogenous expression of cyclin D1, cyclin E1, or ITGB1 was sufficient to rescue proliferation or migration/invasion, respectively. Taken together, our results establish an oncogenic role for RBP2 in lung tumorigenesis and progression and uncover novel RBP2 targets mediating this role.
Highlights
Retinoblastoma binding protein-2 (RBP2) was originally identified as a retinoblastoma protein (Rb)-binding partner [1]
Note that the samples were diagnosed using hematoxylin and eosin (H&E) staining. These results are consistent with the oncogenic implication of RBP2 in gastric cancer [18] and in other cancers analyzed by Oncomine
Our current data indicate that the histone demethylase RBP2 is an oncoprotein overexpressed in lung cancer to promote cell proliferation, motility, migration, invasion, and metastasis
Summary
Retinoblastoma binding protein-2 (RBP2) was originally identified as a retinoblastoma protein (Rb)-binding partner [1]. In 2007, RBP2 was identified as a histone demethylase belonging to the JARID family of histone demethylases, which are able to remove diand trimethyl groups from lysine 4 of histone 3 (H3K4) depend-. Authors' Affiliations: 1Genomics Research Center, 2Agricultural Biotechnology Research Center, and 3Institute of Biological Chemistry, Academia Sinica; 4Institute of Biochemistry and Molecular Biology, National Yang-Ming University; 5Graduate Institute of Pathology, 6Institute of Biochemical Science, National Taiwan University, Taipei; 7Department of Biological Science and Technology, Institute of Bioinformatics and Systems Biology, National Chiao Tung University, Hsinchu, Taiwan; and 8Department of Pathology, Yale University School of Medicine, New Haven, Connecticut. Hsu: Division of Newborn Medicine, Children's Hospital Boston, Harvard Medical School, Boston, Massachusetts.
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