Acquisition of new genomic changes in multiple myeloma cells over time. Myeloma cells were cultured for various durations. Aliquots of cells were removed at specified intervals and genomic DNA was isolated and evaluated for LOH with the use of HuSNP chips (Affymetrix). DNA from the cells harvested and frozen at day 0 was used to define the allelotype baseline, departures from which identified new LOH loci in cells harvested at later time points. Blue lines show new LOH loci in the regions of genome indicated, whereas yellow lines represent retention of preexisting LOH sites. The numbers at the bottom of each figure indicate total number of new LOH loci throughout genome, per 1400 sites investigated. (A) New LOH loci in ARP myeloma cells cultured for either 1 or 12 months, in the region of genome spanning chromosomes 16, 17, and 18, are shown as an example. (B) New LOH loci in U266 myeloma cells cultured for 1 month. (C) New LOH loci in genomic DNA samples, derived from a patient at 1-year intervals.