Construction of tissue micro array from prostate needle biopsies using vertical clustering re-arrangement technique

Abstract

22205 Background: Prostate cancer is heterogenic with variable natural history. Biomarkers defining prognosis and response to therapy at diagnosis are needed. Studies using highly sensitive genome-wide micro array highlighted some potential markers. However, as biomarkers, the value of these candidates must be validated on the protein rather than the gene level, and their predictive value should be tested on prostate biopsy material taken at diagnosis before treatment. Tissue microarray (TMA) is useful for profiling protein expression in a large number of samples simultaneously avoiding observer bias, providing standards for quality control and the potential for high-throughput analysis. In contrast to the relatively large amount of material available from Radical Prostatectomy (RP), prostate needle biopsies contains only very limited amount of tumor arranged within a very thin tissue core that limits TMA construction. Methods: Archival prostate needle biopsies from 48 patients with variable Gleason scores (6–10) were used. The paraffin blocks were melted. Each core, typically measured 0.5 mm and 1.5cm (diameter and length), was sectioned into equal parts of 3–4 mm. For each case, a group of fragments was then re- embedded in a vertical orientation. Using the Beecher Instruments' Manual TMA Apparatus, 2mm cores from each of the vertically rearranged fragments were harvested. Lung, kidney and RP specimens were inserted to the TMA block as negative and positive internal controls. Sections (4μ) from the TMA block were stained with H&E and anti-HMWCK, PIN-cocktail, and PSA stains. Results: A TMA from prostate needle biopsies was constructed. In all patients the same tumor and neighboring tissue (like HGPIN) morphology was evident with identical Gleason score. All tumors preserved their IHC phenotype and there was no loss of tissue. 50 serial sections of 4μ were performed with remaining capacity of 30. Conclusions: The Vertical Clustering Re-arrangement (VCR) technique developed by us is suitable for large scale construction of TMA blocks from prostate biopsies maintaining the morphological and imunohistochemical characteristics of the original samples. This method is promising both in terms of archival tissue preservation and biomarkers research. No significant financial relationships to disclose.