Biomedical Engineering Reference
In-Depth Information
19
Tissue Microarrays for Miniaturized
High-Throughput Molecular Profiling
of Tumors
Ronald Simon, Martina Mirlacher, and Guido Sauter
19.1 Introduction
High throughput expression screening methods, like cDNA microarrays which
allow the simultaneous expression analysis of tens of thousands of genes in one
experiment, have fundamentally changed the way potentially significant genes
are discovered. More recently, modern proteomics tools have been employed
to survey the expression of hundreds or thousands of genes at the protein
level [1]. Such methods are now extensively used in both academic and in-
dustrial research. As a result, hundreds or thousands of ESTs, genes or gene
products with a potential role in non-neoplastic or neoplastic diseases have
been discovered.
Many of these findings may eventually lead to clinically useful applica-
tions. For example, disease specific overexpression of a gene can be exploited
in a diagnostic test. In the best case, a gene being overexpressed or function-
ally altered in a particular disease could serve as a therapeutic target. To
further investigate the potential utility of a newly detected gene alteration,
it is important to collect profound information on the epidemiology of the
candidate gene expression in a multitude of diseased and non-diseased tis-
sues. New technology is also facilitating high throughput analysis of multiple
different tissues. For example, this can be achieved by multi-tissue North-
ern blots, protein arrays, or high throughput real time PCR facilities [2-5].
However, all these methods share the disadvantage that disintegrated tis-
sues are used and that the cell types expressing a gene of interest cannot be
identified. This is problematic because candidate genes can be expressed in
multiple different tissue compartments. In-situ technologies such as immuno-
histochemistry (IHC), RNA in-situ hybridization (RNA-ISH) or fluorescence
in situ hybridization (FISH) are therefore optimal for molecular epidemiology
studies. However, such large-scale in-situ tissue analyses were cumbersome
and slow when traditional methods of molecular pathology were used. More-
over, cutting of traditional tissue sections for in-situ analysis would rapidly
exhaust valuable tissue resources since not more than 200 sections can typi-
