(double minute chromosomes/chromosome aberrations/retroviruses/

Two human neuroendocrine tumor cell lines de- rived from a colon carcinoma contain either numerous double min- ute chromosomes (COLO 320 DM) or a homogeneously staining marker chromosome (COLO 320 HSR). We found amplification and enhanced expression of the cellular oncogene c-myc in both COLO 320 DM and HSR cells, and we were able to show that the homogeneously staining regions of the COLO 320 HSR marker chromosome contain amplified c-myc. From previous and present karyotypes, it appears that the homogeneously staining regions re- side on a distorted X chromosome. Therefore, amplification of c- myc has been accompanied by translocation of the gene from its normal position on chromosome 8 (8q24). Because double minute