Journal of the National Cancer Institute Advance Access published online on September 23, 2008
JNCI Journal of the National Cancer Institute, doi:10.1093/jnci/djn304
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
© The Author 2008. Published by Oxford University Press.
ARTICLES |
Quantitation of Aurora Kinase A Gene Copy Number in Urine Sediments and Bladder Cancer Detection
Affiliations of authors: Departments of Pathology (HSP, WSP, JB, SL, ZW, RLK, BC), Molecular Pathology (HK, SS), Urology (NT, PES, JRS, CD, HBG), and Bioinformatics and Computational Biology (KB), The University of Texas M. D. Anderson Cancer Center, Houston, TX; Department of Urology, The University of Texas Southwestern Medical Center, Dallas, TX (KJE, YL); Department of Pediatrics, Texas Children’s Cancer Center, Houston, TX (RCN)
Correspondence to: Bogdan Czerniak, MD, PhD, Department of Pathology, The University of Texas M. D. Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, TX 77030 (e-mail: bczernia{at}mdanderson.org).
Background: Chromosome missegregation and the resulting aneuploidy is a common change in neoplasia. The Aurora kinase A (AURKA) gene, which encodes a key regulator of mitosis, is frequently amplified and/or overexpressed in cancer cells, and the level of AURKA amplification is associated with the level of aneuploidy. We examined whether AURKA gene amplification is a biomarker for the detection of bladder cancer.
Methods: The effect of ectopic expression of Aurora kinase A (AURKA) using an adenoviral vector in simian virus 40–immortalized urothelial cells (SV-HUC) on centrosome multiplication and chromosome copy number was measured in vitro by immunofluorescence and fluorescence in situ hybridization (FISH), respectively. The FISH test was also used to examine AURKA gene copy number in exfoliated cells in voided urine samples from 23 patients with bladder cancer and 7 healthy control subjects (training set), generating a model for bladder cancer detection that was subsequently validated in an independent set of voided urine samples from 100 bladder cancer patients and 148 control subjects (92 healthy individuals and 56 patients with benign urologic disorders). An AURKA gene score (the proportion of cells with three or more AURKA signals) was used to produce receiver operating characteristic (ROC) curves and to calculate the specificity and sensitivity of the AURKA FISH test. Differences between mean AURKA scores in different pathogenetic groups of bladder cancer stratified according to histological grade and stage were tested by unpaired Mann–Whitney t tests or one-way Wilcoxon tests. All statistical tests were two-sided.
Results: Forced overexpression of AURKA in urothelial cells induced amplification of centrosomes, chromosome missegregation, and aneuploidy, and natural overexpression was detectable in in situ lesions from patients with bladder cancer. The FISH test for the AURKA gene copy number performed on the validation set yielded a specificity of 96.6% (95% confidence interval [CI] = 92.3% to 98.5%) and sensitivity of 87% (95% CI = 79.0% to 92.2%) and an area under the ROC curve of 0.939 (95% CI = 0.906 to 0.971; P < .001).
Conclusion: Overexpression of AURKA can cause aneuploidy in urothelial cells, and the AURKA gene copy number is a promising biomarker for detection of bladder cancer.
| CONTEXT AND CAVEATS Prior knowledge The Aurora kinase A (AURKA) gene, which encodes a key regulator of mitosis, is frequently amplified and/or overexpressed in cancer cells, and the level of AURKA amplification is associated with chromosome missegregation and, ultimately, the level of aneuploidy. Study design Molecular and cytogenetic studies to examine levels of AURKA gene amplification and overexpression in human bladder tumor samples and bladder cancer cell lines, the effect of forced overexpression of AURKA on centrosome multiplication and chromosome copy number, and whether fluorescence in situ hybridization (FISH) detection of AURKA gene copy number in urine sediments can be used to detect bladder cancer. Contribution Forced overexpression of AURKA in urothelial cells induced amplification of centrosomes, chromosome missegregation, and aneuploidy, and natural overexpression was detectable in in situ lesions from patients with bladder cancer. The FISH test for the AURKA gene copy number identified bladder cancer when it was present (sensitivity) in 96.6% of bladder cancer cases and correctly categorized a subject as cancer free (specificity) 87% of the time. Implications AURKA gene copy number may be a promising biomarker for the noninvasive detection of bladder cancer. Limitations It is unclear whether the presence of increased AURKA copy number in rare cells from voided urine sediments of normal subjects was due to nonspecific hybridization of the probe or signifies the presence of cells with the true amplification of the AURKA gene. From the Editors
|
Manuscript received September 10, 2007; revised July 14, 2008; accepted July 25, 2008.
Related Articles in JNCI
CiteULike 
Connotea 
Del.icio.us What's this?
J Natl Cancer Inst 2008 100: 1337.
J Natl Cancer Inst 2008 100: 1740.