Bladder cancer is a common malignant disease characterized by frequent recurrences. The stage of disease at diagnosis and the presence of surrounding carcinoma in situ are important in determining the disease course of an affected individual. Despite considerable effort, no accepted immunohistological or molecular markers have been identified to define clinically relevant subsets of bladder cancer. Here we report the identification of clinically relevant subclasses of bladder carcinoma using expression microarray analysis of 40 well characterized bladder tumors. Hierarchical cluster analysis identified three major stages, Ta, T1 and T2-4, with the Ta tumors further classified into subgroups. We built a 32-gene molecular classifier using a cross-validation approach that was able to classify benign and muscle-invasive tumors with close correlation to pathological staging in an independent test set of 68 tumors. The classifier provided new predictive information on disease progression in Ta tumors compared with conventional staging (P < 0.005). To delineate non-recurring Ta tumors from frequently recurring Ta tumors, we analyzed expression patterns in 31 tumors by applying a supervised learning classification methodology, which classified 75% of the samples correctly (P < 0.006). Furthermore, gene expression profiles characterizing each stage and subtype identified their biological properties, producing new potential targets for therapy.

The results point towards psoriasin, alone or as part of a biomarker profile, as a potential marker for the noninvasive follow-up of patients with SCC.

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In recent years, significant information has been accumulated on the molecular alterations that take place during development of transitional cell carcinoma (TCC). A number of studies aimed at defining loss of heterozygosity have shown a general chromosomal instability in TCC with loss of parts of chromosome 9 at early stages of papillomas, and of chromosomes 11, 13, 3, 4, 8, 17 and 18 during further development of the tumor. Oncogenes are activated, exemplified by mutations in the ras gene family and overexpression of the c-erbB-2 gene, in a minor fraction of tumors. Alterations of tumor suppressors (involved in control of the cell cycle, DNA quality control and activation of apoptosis) seem to be frequently involved. Among these p53 has a key role, and one p53 allele is frequently lost in TCC followed by mutation of the remaining allele.These alterations are correlated with survival, disease progression, invasion and recurrence. Also frequently lost are the cell cycle control genes p16 and p15. The predictive value of this has not yet been determined. Studies of glycosylation genes have shown downregulation of the ABO gene, followed by loss of ABO blood group structures and accumulation of the Lewis cell adhesion molecules in high grade tumors. Functional proteome analysis has furthermore identified biomarkers that are correlated with grade and stage. Molecular models for TCC development can now be built, and clinical testing of these is urgently needed.

Fucosylated glycoproteins carrying ␣1-4 fucose residues are of importance for cell adhesion and as tumor markers. The Lewis gene, FUT3, encodes the only known ␣1-4-fucosyltransferase (FucT), and individuals who are deficient in this enzyme type as Lewis-negative on erythrocytes. We examined the mutational spectrum of the Lewis gene in Denmark and found 6 different mutations. Five, T59G, T202C, C314T, G508A, and T1067A, were frequent, and one, C445A, was only detected in one out of 40 individuals. Allele-specific polymerase chain reaction as well as cloning of FUT3 alleles showed that the 202 and 314 mutations were co-located on the same allele. COS7 cells transfected with an allele having the 202/314 mutations lacked enzyme activity. Polymerase chain reaction-cleavage assays were established for the genotyping of healthy individuals as well as 20 genuine Lewis-negative cancer patients and 10 non-genuine. The latter have Lewis-negative erythrocytes but saliva ␣1-4FucT activity. The genuine Lewis-negative individuals had mutations on both FUT3 alleles. In 66 healthy individuals, a gene dosage effect was detected as FUT3 heterozygous individuals had a lower ␣1-4FucT activity in saliva than did homozygous wild-type individuals. The lower enzyme level in heterozygous individuals resulted in a significantly (p < 0.04) lower level of circulating sialyl-Lewis a structure in serum. This has the clinical impact that cut-off levels in tumor marker assays should be defined on the basis of genotyping. In the group of non-genuine Lewis-negative cancer patients, whose erythrocytes convert from Lewis-positive to Lewis-negative during the disease, FUT3 heterozygosity was significantly (p < 0.05) more common.