DBC1 re-expression alters the expression of multiple components of the plasminogen pathway

Deleted in bladder cancer 1 (DBC1) is a candidate gene for the bladder tumour suppressor locus at 9q33.1. The function of the gene is currently unknown but a cross-species sequence comparison suggests an important role, as it is highly evolutionarily conserved. Here, we transfected a nonexpressing human bladder cancer cell line with a set of human DBC1 cDNA constructs. The effect on global expression patterns was assessed using cDNA microarrays. The cell clone with the lowest level of DBC1 expression showed induced expression of 26 genes including plasminogen activator inhibitor 2 (SERPINB5; 4.6-fold), heparin-binding EGF-like growth factor precursor (DTR; 4.2-fold), small proline-rich protein 2B (SPRR2B; 3.6-fold), metallothionein 1 isoforms (MT1B/MT1A/MT-1F; from 2.9- to 3.2-fold), tissue-type plasminogen activator precursor (PLAT; 2.8-fold) and urokinase-type plasminogen activator precursor (PLAU; 2.7-fold). In clustering analysis, both PLAT and PLAU clustered with the functionally related urokinase plasminogen activator surface receptor (PLAUR; 1.9-fold). Furthermore, 14 human bladder tumours were analysed by real-time quantitative PCR using gene-specific primers for selected (n=20) genes. The expression levels of SERPINB5, PLAU, PLAUR and MT1 correlated with the DBC1 levels, suggesting previously unknown involvement of DBC1 in the urokinase-plasminogen pathway.