Characterization of marker chromosomes in Namalva cells by chromosomal in situ suppression (CISS) hybridization and R-banding.

Chromosomal in situ suppression (CISS) hybridization was used to investigate the distribution of material of chromosomes 1 and 5 present in marker chromosomes of Namalva cells. The Namalva cell line, established from a Burkitt's lymphoma, exhibits a highly variable female karyotype with a large number of marker chromosomes. Libraries from sorted human chromosomes 1 and 5 were used to delineate material of these chromosomes present in the Namalva karyotype. We used the DAB/peroxidase reaction and reflection contrast microscopy for detection of biotinylated hybrid molecules. Identification of chromosomes was achieved by fluorescent R-banding after CISS hybridization, which allowed the assignment of hybridized regions to the particular marker chromosomes. After CISS hybridization with a chromosome I library, the normal chromosome I was labelled as well as a large marker MI and the long arm of marker M3. Using a chromosome 5 library it could be shown that the distal part of the long arm of one chromosome 5 was translocated to marker M2. The normal chromosome 5 was completely labelled. The present investigation demonstrates the advantage of combining CISS hybridization and banding for the identification of complex, rearranged tumor karyotypes.