Tissue Microarrays for Study of Biomarkers
Microarray experiments produce a large volume of data that require validation. The validation of these experiments can be carried out in many fashions. In the reduction to clinical utility, the use of tissue microarrays (TMAs) has become a common tool to both validate and generalize the results of microarray experiments. A TMA is a collection of tissue specimens presented on a glass slide in a grid layout. TMAs contain between tens and hundreds of samples allowing the generalization of microarray findings to a large number of samples. TMAs can be used for in situ hybridization (ISH) and immunohistochemical analysis (IHC), confirming the results of microarray experiments at both the transcriptional and the proteomic level.
The traditional IHC methods for study of biomarkers by TMAs are subjective approaches using manual analysis of tissues according to observable morphological patterns. Disparate results by these methods regarding the relationship between biomarker expression and patient outcome decrease the credibility of TMA studies. Some of these disparities result from subjective optimization of antibody concentrations. HistoRx Inc’s AQUA™ (Automated Quantitative Analysis) platform dramatically improves the accuracy and speed of tissue biomarker analysis while reducing error through objective, rigorous measurement of protein expression. TMAs are discussed further in Chap. 13 (Biomarkers of Cancer).