AMPLIFIED EXTRACHROMOSOMAL ELEMENTS CONTAINING C-MYC AND PVT-1 IN A MOUSE PLASMACYTOMA

After adaptation of a mouse plasma cell tumor, MOPC265, to culture, we have found several unique chromosomal alterations in addition to the T(12;15) translocation and trisomy 11 frequently observed in plasmacyt omas. Among these alterations is a specific coamplification of the c-M yc and Pvt I gene loci from mouse chromosome 15. Further analysis by f luorescence in situ hybridization demonstrates that the amplicons of c -Myc and Pvt I exist as extrachromosomal elements as well as within in tact chromosomes. Most importantly, the presence of both Pvt I and c-M yc in these extrachromosomal elements indicates ongoing coselection fo r these loci in the propagation of MOPC265.