Tissue microarrays: High-throughput analysis of large tumor collections and development of automated imaging capture and digital analysis (SMP).

By means of modern biochip applications it is possible to analyse a large number of genes or proteins which are specifically altered in individual tumor types (Fig. 1A). These changes provide first hints on molecular mechanisms which are involved in tumor development and reveal potential markers for clinical diagnostic or prognostic applications. In order to prove the relevance of novel molecular changes in a more statistical way large tumor collections of clinically well defined tumor samples have to be tested. This is performed by using tissue microarrays. Tumor biopsies of a diameter of 0.5 to 2 mm are positioned in a defined order in paraffin blocks. From these blocks several hundred slices can be obtained and subsequently transferred on glass-slides, where they are used for immunohistochemical or cytogenetic analyses (Fig. 1). Funded by the national genome research network in Germany (NGFN1) several tissue microarrays including more than 5000 tumors were generated in our group. Furthermore, protocols were developed allowing genomic analysis by means of fluorescence in-situ-hybridization in a highly sensitive and specific way. Finally, we are developing new strategies to automatically analyze immunhistochemical experiments performed on tissue microarrays. Currently we particularly focus on:

• the fabrication and analysis of further tissue microarrays, in particular colon carcinoma and malignant glioma
• the development of tissue microarrays from different types of leukaemia (cell suspension microarrays
• the analysis of cell-cycle regulating and anti-apoptotic genes and their role in tumor development
• the application and further development of an automated image-capture and digital analysis system for tissue microarrays