Re-expression of the retinoblastoma-binding protein 2-homolog 1 reveals tumor-suppressive functions in highly metastatic melanoma cells

J Invest Dermatol. 2006 Aug;126(8):1850-9. doi: 10.1038/sj.jid.5700324. Epub 2006 Apr 27.


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cell Division / physiology
  • Cell Line, Tumor
  • DNA, Complementary
  • DNA-Binding Proteins / genetics*
  • DNA-Binding Proteins / metabolism
  • G1 Phase / physiology
  • Gene Expression Regulation, Neoplastic / physiology
  • Genes, Tumor Suppressor / physiology*
  • Humans
  • Jumonji Domain-Containing Histone Demethylases
  • Melanoma / genetics
  • Melanoma / physiopathology*
  • Melanoma / secondary*
  • Nuclear Proteins / genetics*
  • Nuclear Proteins / metabolism
  • Phosphorylation
  • Repressor Proteins / genetics*
  • Repressor Proteins / metabolism
  • Retinoblastoma Protein / metabolism
  • Serine / metabolism
  • Skin Neoplasms / genetics
  • Skin Neoplasms / pathology*
  • Skin Neoplasms / physiopathology*
  • Transcriptional Activation / physiology


  • DNA, Complementary
  • DNA-Binding Proteins
  • Nuclear Proteins
  • Repressor Proteins
  • Retinoblastoma Protein
  • Serine
  • Jumonji Domain-Containing Histone Demethylases
  • KDM5B protein, human