Overexpressed Skp2 within 5p amplification detected by array-based comparative genomic hybridization is associated with poor prognosis of glioblastomas - PubMed (original) (raw)

Overexpressed Skp2 within 5p amplification detected by array-based comparative genomic hybridization is associated with poor prognosis of glioblastomas

Kuniyasu Saigusa et al. Cancer Sci. 2005 Oct.

Abstract

To better understand the pathogenesis of glioblastoma multiforme (GBM) and to increase the accuracy of predicting outcomes for patients with this disease, we performed genome-wide screening for DNA copy-number aberrations in 22 glioma-derived cell lines using a custom-made comparative genomic hybridization-array. Copy-number gains were frequently detected at 3q, 7p, 7q, 20q, Xp and Xq, and losses at 4q, 9p, 10p, 10q, 11q, 13q, 14q, 18q, and 22q. Among several non-random chromosomal aberrations, the gain/amplification of DNA at 5p, which has never been reported before in GBM, was detected with a relatively high ratio (log2 ratio = 0.41-1.19) in four cell lines. Amplification and subsequent overexpression of SKP2, a possible target of amplification within 5p, were detected in four of the 22 cell lines. We also investigated the expression of the gene product in primary GBM by immunohistochemistry, which revealed increased levels of Skp2 in 11 of the 35 tumors examined (31.4%). Heightened expression of Skp2 was associated with shorter overall survival (P = 0.001, logrank test), especially in patients younger than 65 years. These results suggest that overexpression of Skp2 through gene amplification may contribute to the pathogenesis of GBM, and that overabundance of the protein might be a useful prognostic tool in patients with this disease.

PubMed Disclaimer

Figures

Figure 1

Figure 1

Genome‐wide frequencies of copy‐number gains (above zero, green) and losses (below zero, red) in 22 glioma‐derived cell lines. Clones are ordered as chromosomes 1–22, X, and Y, and within each chromosome on the basis of the University of California, Santa Cruz mapping position.

Figure 2

Figure 2

(a) Genetic changes observed on chromosome 5 in the KNS‐60 and SF126 cell lines. Comparative genomic hybridization‐based (CGH) array analysis identified amplification of almost the entire short arm of chromosome 5, but no amplification in the long arm. A red arrow indicates the clone containing the SKP2 gene. (b) Representative images of fluorescence in situ hybridization (FISH) experiments using BAC RP11–36A10 (green) on metaphase chromosomes from the KNS‐60 and SF126 cell lines. This BAC generated 10 and 11 signals, respectively, in the KNS‐60 and SF126 cells.

Figure 3

Figure 3

Relative expression levels of SKP2 mRNA determined by real‐time reverse transcription–polymerase chain reaction. Results are presented as the ratio between SKP2 and a reference gene (GAPDH). Significant correlation (P = 0.0411) between copy‐number gains and relative expression levels of SKP2 was observed in 22 glioma cell lines. Copy number ratios (log2) of four cell lines with gain of SKP2 are shown in parentheses.

Figure 4

Figure 4

Immunohistochemical presentation of Skp2 expression in (a) a glioblastoma multiforme (GBM) tumor with high expression of Skp2, where nuclear Skp2 staining was positive in 32.3% of tumor cells on average; and (b) a GBM tumor with low Skp2 expression, where nuclear staining for Skp2 was positive in an average of only 7.3% of tumor cells. (c) Kaplan–Meier curves for overall survival of all patients (n = 35) with GBM after surgery, stratified according to the nuclear level of Skp2 (P = 0.0010). (d) Kaplan–Meier curves for overall survival of patients younger than 65 years (n = 25); patients with high Skp2 expression showed significantly poorer prognosis in overall survival than patients with low Skp2 expression (P = 0.0004). (e) Kaplan–Meier curves for overall survival of patients older than 65 years (n = 10); Skp2 expression showed no correlation with prognosis in this group (P = 0.6521).

References

    1. Ohgaki H, Dessen P, Jourde B et al. Genetic pathways to glioblastoma: a population‐based study. Cancer Res 2004; 64: 6892–9. - PubMed
    1. Kleihues P, Ohgaki H. Primary and secondary glioblastomas: from concept to clinical diagnosis. Neuro-oncology 1999; 1: 44–51. - PMC - PubMed
    1. Vogelstein B, Kinzler KW. The multistep nature of cancer. Trends Genet 1993; 9: 138–41. - PubMed
    1. Wong AJ, Bigner SH, Bigner DD et al. Increased expression of the epidermal growth factor receptor gene in malignant gliomas is invariably associated with gene amplification. Proc Natl Acad Sci USA 1987; 84: 6899–903. - PMC - PubMed
    1. Fleming TP, Sexena A, Clark WC et al. Amplification and/or overexpression of platelet‐derived growth factor receptors and epidermal growth factor receptor in human glial tumors. Cancer Res 1992; 52: 4550–3. - PubMed

Publication types

MeSH terms

Substances

LinkOut - more resources