FUSION AND AMPLIFICATION OF 2 ORIGINALLY NONSYNTENIC CHROMOSOMAL REGIONS IN A MAMMARY-CARCINOMA CELL-LINE

The FLG/FGFRI gene, encoding a receptor for members of the FGF family, is located at 8p11.2-p12. It is amplified, overexpressed, and not grossly rearranged in the MDA-MB-134 breast carcinoma cell line, whereas other genes from the pericentromeric 8p region are not amplified. The FGF4/HSTFI gene, located at 11q13, is also amplified with a substantial portion of the 11q13 region, but is not overexpressed in MDA-MB-134 cells. In this cell line, amplified sequences constitute a large homogeneously staining region (HSR) which is part of a marker chromosome containing chromosome 8 and chromosome 11 sequences. Using probes for the FGF4/HSTFI and the FLG/FGFRI genes in fluorescence chromosomal in situ hybridization, we show that the HSR contains de novo fused and amplified 11q13 and 8p 11-p12 sequences associated in a complex structure containing approximately the same number of FGF4 and FGFRI genes. The significance of this genetic abnormality for MDA-MB-134 cells, and for breast carcinogenesis in general, is unknown, but may underlie a particular type of oncogene activation.