title: Re-expression of the retinoblastoma-binding protein 2-homolog 1 reveals tumor-suppressive functions in highly metastatic melanoma cells.
abstract: The loss of cell cycle control in malignant melanomas is thought to be due to a lack of retinoblastoma protein (pRb) activity. We have recently reported a progressive deficiency of the retinoblastoma-binding protein 2-homolog 1 (RBP2-H1) in advanced and metastatic melanomas in vivo, suggesting a role of RBP2-H1 in loss of pRb-mediated control. Therefore, in this study, we re-established the pRb-modulating function of RBP2-H1 in highly metastatic A375-SM melanoma cells by re-expressing its C-term (cRBP2-H1). As previously shown, the corresponding domains comprise the pRb-binding region of the RBP2-H1 protein (non-T/E1A-pRb-binding domain (NTE1A)). As a result, we detected pRb-hypophosphorylation selectively at Ser795, but not at Ser780 and Ser807/811 throughout the G1 phase of the cell cycle. As a further consequence, a block in G1/S transition was observed accompanied by a significant decrease of DNA replication and cellular proliferation. As demonstrated by cDNA microarrays of cRBP2-H1-transduced cells and confirmed by quantitative TaqMan reverse transcriptase-PCR, differential expression of melanoma-progression-related genes was observed, among them bone morphogenetic protein 2, follistatin, transforming growth factor alpha, hepatocyte growth factor, transcription factor 4 and microphthalmia-associated transcription factor. Conclusively, these data suggest that RBP2-H1 exerts a broad tumor-suppressive function partially mediated by pRb modulation. Therefore, re-establishing of RBP2-H1 could evolve as an interesting novel approach in developing experimental treatments for metastatic melanomas.
authors.affiliation: Department of Dermatology, University of Regensburg, Regensburg, Germany.
authors.forename: Alexander
authors.initials: A
authors.lastname: Roesch
authors.forename: Bernd
authors.initials: B
authors.lastname: Becker
authors.forename: Wulf
authors.initials: W
authors.lastname: Schneider-Brachert
authors.forename: Ilja
authors.initials: I
authors.lastname: Hagen
authors.forename: Michael
authors.initials: M
authors.lastname: Landthaler
authors.forename: Thomas
authors.initials: T
authors.lastname: Vogt
mesh_terms: D002455:Cell Division / Q000502:physiology; D045744:Cell Line, Tumor; D018076:DNA, Complementary; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D016193:G1 Phase / Q000502:physiology; D015972:Gene Expression Regulation, Neoplastic / Q000502:physiology; D016147:Genes, Tumor Suppressor / Q000502:physiology*; D006801:Humans; D056484:Jumonji Domain-Containing Histone Demethylases; D008545:Melanoma / Q000235:genetics / Q000503:physiopathology* / Q000556:secondary*; D009687:Nuclear Proteins / Q000235:genetics* / Q000378:metabolism; D010766:Phosphorylation; D012097:Repressor Proteins / Q000235:genetics* / Q000378:metabolism; D016160:Retinoblastoma Protein / Q000378:metabolism; D012694:Serine / Q000378:metabolism; D012878:Skin Neoplasms / Q000235:genetics / Q000473:pathology* / Q000503:physiopathology*; D015533:Transcriptional Activation / Q000502:physiology
chemical_list: D018076:DNA, Complementary; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D012097:Repressor Proteins; D016160:Retinoblastoma Protein; D012694:Serine; D056484:Jumonji Domain-Containing Histone Demethylases; C119611:KDM5B protein, human