[Metaphase chromosomes of human multiple myeloma cells of line U-266: karyotype and morpho-functional characteristics of nucleolar organizer regions].

Human multiple myeloma (MM) cell lines are widely used to investigate chromosome rearrangements typical for this disease. However, during cell cultivation both numeral and structural chromosome rearrangements usually take place in addition to changes of structural and functional status of particular chromosome regions. We investigated karyotype and morpho-functional status of nucleolar organizer regions (NORs) in human cell line MM U-266. Cytogenetic analysis (G-banding) showed karyotypic stability and balanced chromosome set in hypodiploid (n = 44) U-266 cells. We found the presence of rearranged chromosomes, typical for U-266, which retained throughout many year cell cultivation. At the same time, further chromosome rearrangements were shown, along with a tendency of cells to polyploidization. Using FISH (rDNA-probe) and AgNOR-staining techniques, we found that only 4 of 8 NORS were Ag positive (AgNOR), whose dimensions varied from 1 to 3 units of arbitrary scale (u.a.s.). The average summarized AgNOR size was 7.19 +/- 0.03 u.a.s. Peculiarities of the NOR morpho-functional status in U-266 cells are discussed.