Evaluation of 24-color multifluor-fluorescence in-situ hybridization (M-FISH) karyotyping by comparison with reverse chromosome painting of the human breast cancer cell line T-47D.

Multifluor-fluorescence in-situ hybridization (M-FISH) chromosome paints for all the chromosomes in the human complement labeled with different combinations of fluorochromes is a recent technological development enabling assignment of chromosomal material to rearranged chromosomes. Little data is available on the accuracy and limitations of the approach to the analysis of complex karyotypes, which are characteristic of many malignant diseases. Here we compare M-FISH analysis of the breast-cancer-derived cell line T-47D with a previous analysis by reverse chromosome painting analysis of flow-sorted chromosomes from the same material. This demonstrated a high degree of concordance. It also illustrated the limitations of M-FISH analysis, including difficulties identifying small regions of chromosomal material and intrachromosomal rearrangements. Confirmation of selected aberrations using less-complex mixtures of painting probes and further definition of abnormalities using single copy markers may be required. The detailed karyotype description possible by M-FISH analysis contrasts with the definition in the original G-banding analysis. This and the level of concordance with reverse FISH painting supports the utility of the approach in the definition of complex karyotypes.