Improved procedure for fluorescence in situ hybridization on tissue microarrays.

ABSTRACT

BACKGROUND: The recently developed tissue microarray (TMA) technology allows the arrangement of up to a thousand tissue specimens on a single microscope slide. This technology enables researchers to perform gene copy number studies on very large series of archival formalin-fixed tissues using fluorescence in situ hybridization (FISH). However, the hybridization properties of individual archival specimens can vary considerably. Therefore a highly optimized protocol is needed to fulfill the task of producing evaluable hybridization signals simultaneously in hundreds of specimens in a TMA. METHODS: The performance of two different FISH protocols, the standard protocol for paraffin embedded tissues and our new optimized protocol, was tested on TMAs using probes for the HER-2 and ZNF217 genes as well as the chromosome 17 centromere. RESULTS: The new protocol resulted in greatly increased signal intensity and an almost 30% increase in the number of tissue samples with evaluable hybridization signals. CONCLUSIONS: Our improved protocol for FISH on TMAs provides standardized hybridization conditions leading to high-quality hybridization signals in the majority of specimens. The increases in the signal intensity and the number of evaluable samples are extremely important for the successful analyses of TMAs by FISH and will allow the utilization of the TMA technology in its full potential.