Article

Nuclear expression of YB-1 protein correlates with P-glycoprotein expression in human osteosarcoma.

Department of Orthopaedic Surgery, Faculty of Medicine, Kyushu University, Fukuoka, Japan.
Clinical Cancer Research (Impact Factor: 8.19). 10/1998; 4(9):2273-7.
Source: PubMed

ABSTRACT The Y-box-binding protein, YB-1, is a member of the DNA-binding protein family. It binds to the Y-box, an inverted CCAAT box, in the promoter region of the human multidrug resistance 1 gene, which encodes P-glycoprotein (P-gp). Nuclear localization of YB-1 protein has been reported to be associated with the intrinsic expression of P-gp in human breast cancer. We studied the immunohistochemical expression of YB-1 protein in 69 untreated biopsy specimens of conventional osteosarcomas and compared it with the expression of P-gp. Furthermore, cell proliferation, as determined by the MIB-1-labeling index (MIB-1-LI), was measured by immunohistochemistry. In all 69 untreated osteosarcomas, YB-1 protein was expressed in the cytoplasm. In 32 of 69 (46%) cases, YB-1 was also localized in the nucleus. The expression of P-gp was evident in 23 of these 32 cases, and there was a significant correlation between the nuclear expression of YB-1 and P-gp expression (P < 0.0001). Chondroblastic osteosarcoma expressed YB-1 in the nucleus more frequently (eight of nine cases) than did other types of osteosarcoma, whereas P-gp was also frequently expressed in chondroblastic subtype. There was no correlation between the nuclear expression of YB-1 and histological grade. The MIB-1-LI was significantly higher in cases showing the nuclear expression of YB-1 (MIB-1-LI averaged 22.56 in cases with only cytoplasmic expression of YB-1 but averaged 28.20 in cases with cytoplasmic and nuclear expression of YB-1; P = 0.0477). In human osteosarcoma, nuclear localization of YB-1 protein was associated with the expression of P-gp, suggesting that YB-1 could be a prognostic marker for multidrug resistance in osteosarcoma.

0 Followers
 · 
69 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Background:Prognosis of osteosarcoma (OS) with distant metastasis and local recurrence is still poor. Y-box binding protein-1 (YB-1) is a multifunctional protein that can act as a regulator of transcription and translation and its high expression of YB-1 protein was observed in OS, however, the role of YB-1 in OS remains unclear.Methods:Y-box binding protein-1 expression in OS cells was inhibited by specific small interfering RNAs to YB-1 (si-YB-1). The effects of si-YB-1 in cell proliferation and cell cycle transition in OS cells were analysed in vitro and in vivo. The association of nuclear expression of YB-1 and clinical prognosis was also investigated by immunohistochemistry.Results:Proliferation of OS cell was suppressed by si-YB-1 in vivo and in vitro. The expression of cyclin D1 and cyclin A were also decreased by si-YB-1. In addition, si-YB-1 induced G1/S arrest with decreased cyclin D1 and cyclin A in OS cell lines. Direct binding of YB-1 in OS cell lines was also observed. Finally, the nuclear expression of YB-1 was significantly related to the poorer overall survival in OS patients.Conclusion:Y-box binding protein-1 would regulate cell cycle progression at G1/S and tumour growth in human OS cells in vitro and in vivo. Nuclear expression of YB-1 was closely associated with the prognosis of OS, thus, YB-1 simultaneously could be a potent molecular target and prognostic biomarker for OS.
    British Journal of Cancer 03/2013; 108(4):836-47. DOI:10.1038/bjc.2012.579 · 4.82 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Y-box-binding protein 1 (YB-1) is an oncogenic transcription factor whose overexpression and nuclear localization is associated with tumor progression and drug resistance. Transcriptional activation of YB-1 in response to genotoxic stress is believed to occur in the cytoplasm through sequence-specific endoproteolytic cleavage by the 20S Proteasome, followed by nuclear translocation of cleaved YB-1. To study the proteolysis model, we developed a two-step affinity purification of endogenous YB-1 protein species and characterized the products using mass spectrometry. Whereas full-length YB-1 was readily identified, the smaller protein band thought to be activated YB-1 was identified as hnRNP A1. An antibody specific for YB-1 was generated, which revealed only one YB-1 species, even after genotoxic stress-induced nuclear YB-1 translocation. These findings warrant re-evaluation of the mechanism of YB-1 nuclear translocation and transcriptional activation. The relationship between nuclear YB-1 and tumor progression may also have to re-evaluated in some cases.
    Oncogene 10/2009; 29(3):403-10. DOI:10.1038/onc.2009.321 · 8.56 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: F-Box proteins (FBPs) are variable adaptor proteins that earmark protein substrates for ubiquination and destruction by the proteasome. Through their N-terminal F-box motif, they couple specific protein substrates to a catalytic machinery known as SCF (Skp-1/Cul1/F-Box) E3-ubiquitin ligase. Typical FBPs bind the specific substrates in a phosphorylation dependent manner via their C-termini using either leucine rich repeats (LRR) or tryptophan-aspartic acid (WD40) domains for substrate recognition. By using a gene trap strategy that selects for genes induced during programmed cell death, we have isolated the mouse homolog of the hypothetical human F-Box protein 33 (FBX33). Here we identify FBX33 as a component of an SCF E3-ubiquitin ligase that targets the multifunctional regulator Y-box binding protein 1 (YB-1)/dbpB/p50 for polyubiquitination and destruction by the proteasome. By targeting YB-1 for proteasomal degradation, FBX33 negatively interferes with YB-1 mediated functions. In contrast to typical FBPs, FBX33 has no C-terminal LRR or WD40 domains and associates with YB-1 via its N-terminus. The present study confirms the existence of a formerly hypothetical F-Box protein in living cells and describes one of its substrates.
    FEBS Letters 08/2006; 580(16):3921-30. DOI:10.1016/j.febslet.2006.06.023 · 3.34 Impact Factor