Search

Background: Mutations and loss of the von Hippel-Lindau (VHL) tumor suppressor gene are associated with most renal cancers as well as several other types of human tumors, but the potential role of the VHL protein (pVHL) in patients with chondrosarcoma has not been characterized. The purpose of the present study was to investigate the expression profiles of pVHL in chondrosarcoma and its association with clinicopathologic parameters, Bax expression, the apoptosis index, and overall survival of patients with chondrosarcoma., Methods: The messenger RNA (mRNA) and protein levels of VHL in fresh specimens from eight chondrosarcomas were studied with use of real-time polymerase chain reaction and Western blot, respectively. The protein expression of VHL and Bax was investigated by means of immunohistochemical analysis of paraffin-embedded clinical specimens from seventeen benign cartilage tumors and thirty-four chondrosarcomas. The apoptosis index in chondrosarcoma was examined by means of the TUNEL (terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling) assay. Curves for overall survival were drawn according to the Kaplan-Meier method, and differences were analyzed with the log-rank test. The association of pVHL expression with the clinicopathologic parameters, Bax expression, apoptosis index, and overall survival for patients with chondrosarcoma was also analyzed., Results: Levels of VHL protein (p = 0.005) and mRNA (p = 0.008) were significantly reduced in chondrosarcoma tissues as compared with the paired adjacent normal tissues. Immunohistochemical analysis showed decreased pVHL in a significantly higher proportion of chondrosarcomas (64.7%) than benign cartilage tumors (29.4%). pVHL expression was positively correlated with Bax expression and the apoptosis index in chondrosarcoma. Longitudinal studies of a cohort of patients with chondrosarcomas showed that decreased pVHL expression significantly correlated with increased tumor grade (p = 0.026) but was not independently predictive of overall survival., Conclusions: Reduced pVHL expression was associated with decreased apoptosis and increasing chondrosarcoma grade, but the relationship between these findings and chondrosarcoma pathogenesis requires further study.

Hypoxia-inducible factor (HIF)-1α is a key nuclear transcription factor that regulates the cellular response to hypoxia, and is important for solid tumor growth and survival. However, the underlying role of HIF-1α in human chondrosarcoma has not been well characterized. This study aims to investigate the expression patterns of HIF-1α in chondrosarcoma, and its association with clinicopathologic features, Bcl-xL expression, apoptosis index (AI), and overall survival of patients with chondrosarcoma. Our results shown that the protein levels of HIF-1α were increased, and the mRNA and protein levels of Bcl-xL were also increased in SW1353 cells under hypoxic conditions. In eight patients with chondrosarcoma, increased expression of HIF-1α and Bcl-xL was detected in chondrosarcoma tissues compared with the paired adjacent normal tissues. Of 34 archival specimens of chondrosarcomas, 20 (58.8%) showed high HIF-1α protein expression as compared to benign cartilage tumors. Increased HIF-1α expression was correlated with a higher pathological grade and MSTS stage of chondrosarcoma. Moreover, HIF-1α expression was significantly associated with Bcl-xL expression and AI. More significantly, the survival rate of patients with HIF-1α high tumors was significantly lower than that of patients with HIF-1α low tumors. These findings suggest that increased HIF-1α levels mediated up-regulation of Bcl-xL play a prominent role in evasion of apoptosis and tumor progression, and can be predictive for the prognosis in human chondrosarcoma., (Copyright © 2010 Orthopaedic Research Society.)

Clinical management of chondrosarcoma remains a challenging problem, largely due to the toxicity and resistance of this tumor to conventional chemotherapy. Programmed Cell Death 5 (PDCD5) is a protein that accelerates apoptosis in different cell types in response to various stimuli, and has been shown to be down-regulated in many cancer tissues. In this study, mRNA and protein levels of PDCD5 were found to be up-regulated in cisplatin-treated SW1353 chondrosarcoma cells compared with untreated cells. Recombinant human PDCD5 (rhPDCD5) was also shown to sensitize chondrosarcoma cells to cisplatin-based chemotherapy, with inhibition of cell growth and apoptosis detected both in vitro and in vivo. Increased expression of Bax and decreased expression of Bcl-2 were also observed, along with release of cytochrome c from mitochondria into the cytosol. Additionally, cleavage of caspase-9 and caspase-3, as well as the cleavage of poly (ADP-ribose) polymerase (PARP), were detected, suggesting that sensitization of chondrosarcoma cells involves the intrinsic mitochondrial apoptosis pathway. In vivo, the treatment of a xenograft model of chondrosarcoma with rhPDCD5 and cisplatin significantly inhibited tumor cell proliferation and induced apoptosis compared to treatment with cisplatin alone. Overall, these data provide a theoretical basis for the administration of rhPDCD5 and cisplatin for the treatment of patients with chondrosarcoma.

The tyrosine kinase, c-Abl, plays important roles in many aspects of cellular function. The activity of c-Abl is tightly controlled, but the underlying mechanism is unclear. Recent studies suggest that c-Abl function is regulated by distinct lipids in different cell types. In the present study, we show that the DNA replication factor, proliferating cell nuclear antigen (PCNA), interacts with c-Abl and destabilizes c-Abl by promoting its polyubiquitination and degradation. Moreover, deletion of a domain in c-Abl, the PIP box, disrupts its interaction with PCNA, abolishes the PCNA-induced degradation of nuclear c-Abl, and substantially increases the nuclear c-Abl apoptotic function. These findings indicate that PCNA negatively regulates the stability of c-Abl and thereby inhibits apoptosis in the response to DNA damage.

Abstract: The CCAAT/enhancer-binding protein beta (C/EBPβ) is a critical transcription factor that regulates gene expression during numerous biological processes, including differentiation, metabolism, homeostasis, proliferation, tumorigenesis, inflammation, and apoptosis. In this study, interactions between C/EBPβ and either the Abelson murine leukemia viral oncogene homolog 1 (c-Abl) or the Abl-related gene (Arg) were demonstrated in vitro and in vivo with a direct binding assay and by co-immunoprecipitation, respectively. The Y79 amino acid residue of C/EBPβ was phosphorylated by c-Abl or Arg. The phosphorylation of C/EBPβ resulted in an increased C/EBPβ stability and a potentiation of C/EBPβ transcription activation activity in cells. Expression of the C/EBPβ(Y79F) mutant in HEK293, and K562, and in other cell lines, resulted in less of a delay in the cell cycle compared to the wild type C/EBPβ; furthermore, the C/EBPβ (Y79F) mutant induced an increased apoptosis compared to the wild type C/EBPβ. These findings suggest that the c-Abl family non-receptor tyrosine kinases have a role in the regulation of the C/EBPβ transcription factor. [Copyright &y& Elsevier]