Posters— Diagnostic Imaging/Pathology

TISSUE MICROARRAY BLOCKS: AN EFFICIENT METHOD FOR SCREENING SOFT TISSUE AND BONY SARCOMAS

Thomas D, Baker L, Giordano T,. (University of Michigan Comprehensive Cancer Center, Ann Arbor, MI 48109)

As the human genome project reaches conclusion, the number of oncology related genes and corresponding antibodies and nucleic add probes will continue to proliferate. Evaluation of these new markers using conventional tissue based assays will require significant resources. The recently developed tissue microarray technique allows for the efficient screening of large numbers of tumor specimens with multiple probes. To-date, no one has applied this technique to the screening of soft tissue and bony sarcomas. Basically the technique involves the cutting of several core tissue biopsies (diameter 0.6 rrLm; height 3-4 mm) taken from representative ‘donor’ paraffin embedded tumor blocks and precisely arrayed into a ‘recipient’ paraffin block. Several tissue microarray blocks containing multiple cores from soft tissue and bony sarcomas were produced containing over 100 sarcoma specimens.

Sections cut from these arrays allow parallel detection of DNA or RNA by nonradioactive in-situ hybridization and protein by immunohistochemistry. At least 200 consecutive 5 ~tm thick sections can be cut from each tumor block.This allows consecutive analysis of a large number of molecular markers. In order to validate this approach of using small representative cores, the original donor blocks were also examined retrospectively for the expression of oncology related markers such as telomerase reverse transcriptase (by in-situ hybridization and immunohistochemistry), p53, Mb-l, ErbB2 (by immunohistochemistry) and apoptosis (by TUNEL assay) and was shown to correlate well with the results obtained with the tissue microarray blocks.

This technique represents an effective means of screening large numbers of specimens with multiple probes and antibodies. Kindly supported by the Walther Cancer Institute.