Improved procedure for fluorescence in situ hybridization on tissue microarrays

Background: The recently developed tissue microarray (TMA) technology allow s the arrangement of up to a thousand tissue specimens on a single microsco pe slide, This technology enables researchers to perform gene copy number s tudies on very large series of archival formalin-fixed tissues using fluore scence in situ hybridization (FISH), However, the hybridization properties of individual archival specimens can van, considerably. Therefore a highly optimized protocol is needed to fulfill the task of producing evaluable hyb ridization signals simultaneously in hundreds of specimens in a TMA. Methods: The performance of two different FISH protocols, the standard prot ocol for paraffin embedded tissues and our new optimized protocol, was test ed on TMAs using probes for the HER-2 and ZNF217 genes as well as the chrom osome 17 centromere. Results: The new protocol resulted in greatly increased signal intensity an d an almost 30% increase in the number of tissue samples with evaluable hyb ridization signals. Conclusions: Our improved protocol for FISH on TMAs provides standardized h ybridization conditions leading to high-quality hybridization signals in th e majority of specimens. The increases in the signal intensity and the numb er of evaluable samples are extremely important for the successful analyses of TMAs by FISH and will allow the utilization of the TMA technology in it s full potential. Published 2001 Wiley-Liss, Inc.