1. ¹Molecular Diagnostic Laboratory, Department of Clinical Biochemistry, Aarhus University Hospital Skejby, 8200 Aarhus N, Denmark
2. ²Institute of Pathology, Aarhus University Hospital, Aarhus Hospital, 8000 Aarhus C, Denmark
3. ³Department of Urology, Aarhus University Hospital Skejby, 8200 Aarhus N, Denmark

Correspondence: Professor TF Ørntoft, E-mail: orntoft@ki.au.dk

Received 31 May 2005; Revised 19 September 2005; Accepted 20 September 2005; Published online 1 November 2005.

Abstract

At present, the mechanism leading to bladder cancer is still poorly understood, and our knowledge about early events in tumorigenesis is limited. This study describes the changes in gene expression occurring during the neoplastic transition from normal bladder urothelium to primary Ta tumours. Using DNA microarrays, we identified novel differentially expressed genes in Ta tumours compared to normal bladder, and genes that were altered in high-grade tumours. Among the mostly changed genes between normal bladder and Ta tumours, we found genes related to the cytoskeleton (keratin 7 and syndecan 1), and transcription (high mobility group AT-hook 1). Altered genes in high-grade tumours were related to cell cycle (cyclin-dependent kinase 4) and transcription (jun d proto-oncogene). Furthermore, we showed the presence of high keratin 7 transcript expression in bladder cancer, and Western blotting analysis revealed three major molecular isoforms of keratin 7 in the tissues. These could be detected in urine sediments from bladder tumour patients.