The development of prognostic and diagnostic biomarkers, such as those from gene expression studies, requires independent validation in clinical specimens. Immunohistochemical analysis on tissue microarrays (TMAs) of formalin-fixed paraffin-embedded tissue is often used to increase the statistical power, and it is used more often than in situ hybridization, which can be technically limiting. Herein, we introduce a method for performing quantitative gene expression analysis across a TMA using an adaptation of 2D-RT-qPCR, a recently developed technology for measuring transcript levels in a histologic section while maintaining 2-dimensional positional information of the tissue sample. As a demonstration of utility, a TMA with tumor and normal human prostate samples was used to validate expression profiles from previous array-based gene discovery studies of prostate cancer. The results show that 2D-RT-qPCR expands the utility of TMAs to include sensitive and accurate gene expression measurements.
‡Tissue Array Research Program, Laboratory of Pathology, Center for Cancer Research, National Cancer Institute, Bethesda
†Fischell Department of Bioengineering and the Institute for Systems Research
§Department of Mechanical Engineering, University of Maryland, College Park, MD
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M.A., M.R.E.-B., M.T., B.S., and E.S. are inventors on patent applications, including issue US patent 8283158 covering the underlying technology and may receive future royalties through the NIH or University of Maryland technology transfer programs.
This work was supported in part by the Intramural Research Program of the NIH, National Cancer Institute, Center for Cancer Research.
The authors declare no conflict of interest.
Reprints: Stephen M. Hewitt, MD, PhD, 10 Center Drive, Room 2 A 33, Rockville, MD 20892 (e-mail: firstname.lastname@example.org).