Oncogene Amplification Detection by Fluorescence In Situ Hybridization (FISH).

Abstract

Fluorescence in situ hybridization (FISH) represents the newest methodological approach for testing for genetic alterations in individual cells. FISH can detect gene amplification both in metaphase chromosomes and in interphase nuclei. FISH allows the determination of the amplification levels and amplification patterns: clustered signals and multiple scattered signals found by FISH correspond respectively to amplicons in homogeneous staining regions and in double-minute chromosomes found in conventional cytogenetics. Using dual-colour FISH, differentiation of low level amplification from increased gene number by polysomy is also possible. FISH can detect gene amplification not only in isolated nuclei and imprinted cells, but also in formalin-fixed paraffin-embedded tissues, and is therefore a potent tool to detect gene amplification in archival solid tumor specimens. A direct correlation can be made with the morphology, so that tissue localization of such genetic events as tumor heterogeneity and tumor progression is feasible. Furthermore, in combination with immunohistochemistry, direct correlation with the oncogene amplification and the oncoprotein overexpression are possible. Although there have been numerous FISH studies examining oncogene amplifications using clinical materials, at the present time the most important clinical application of FISH is the identification of breast cancer patients eligible for the new adjuvant therapy by humanized monoclonal antibody to c-erbB-2 protein (trastuzumab).