1 Department of clinical biochemistry, Faculty of Health Sciences, Aarhus University, Aarhus University2 The Department of Urology K, Faculty of Health Sciences, Aarhus University, Aarhus University3 Center for Biological Sequence Analysis, Technical University of Denmark, DK 2100 Lyngby, Denmark4 Department of Clinical Medicine - Department of clinical biochemistry, Department of Clinical Medicine, Health, Aarhus University5 Department of Clinical Medicine - Molekylær Medicinsk afdeling (MOMA), Department of Clinical Medicine, Health, Aarhus University6 Molecular Diagnostic Laboratory, Departments of Clinical Biochemistry, Aarhus University Hospital, DK 8200 Skejby, Aarhus, Denmark7 Department of Clinical Medicine - Department of clinical biochemistry, Department of Clinical Medicine, Health, Aarhus University8 Department of Clinical Medicine - Molekylær Medicinsk afdeling (MOMA), Department of Clinical Medicine, Health, Aarhus University
Multiple transcriptional events take place when normal urothelium is transformed into tumor tissue. These can now be monitored simultaneously by the use of oligonucleotide arrays, and expression patterns of superficial and invasive tumors can be established. Single-cell suspensions were prepared from bladder biopsies (36 normal, 29 tumor). Pools of cells were made from normal urothelium and from pTa grade I and II and pT2 grade III and IV bladder tumors. From these suspensions, and from 10 single-tumor biopsies, labeled cRNA was hybridized to oligonucleotide arrays carrying probes for 6500 genes. The obtained expression data were sorted according to a weighting scheme and were subjected to hierarchical cluster analysis of tissues and genes. Northern blotting was used to verify the array data, and immunohistology was used to correlate between RNA and protein levels. Hierarchical clustering of samples correctly identified the stage using both 4076 genes and a subset of 400 genes covarying with the stages and grades of tumors. Hierarchical clustering of gene expression levels identified several stage-characteristic, functionally related clusters, encoding proteins that were related to cell proliferation, oncogenes and growth factors, cell adhesion, immunology, transcription, proteinases, and ribosomes. Northern blotting correlated well with array data. Immunohistology showed a good concordance between transcript level and protein staining. The study indicates that gene expression patterns may be identified in bladder cancer by combining oligonucleotide arrays and cluster analysis. These patterns give new biological insight and may form a basis for the construction of molecular classifiers and for developing new therapy for bladder cancer.
Cancer Research, 2001, Vol 15, Issue 61, p. 2492-2499