Amplification of the c-myc Oncogene is associated with an abnormally banded region on chromosome 8 or double minute chromosomes in two HL-60 human leukemia sublines

Two sublines of HL-60 human promyelocytic leukemia cells were examined cytogenetically with banding techniques. The karyotype of one subline was 44,X,-X,-5,-9,-10, -15,-17,+18,8q+,14q-,16q+,16q+,+mar1,+mar2,+mar3. The defective chromosome #8 contained an expanded chromosomal segment at the end of the long arm at band q24. The segment appeared to be a homogeneously staining region on the basis of quinacrine fluorescence banding. Using G-banding technique, this segment showed some evidence of indistinct aberrant bands and, thus, was designated an abnormally banded region (ABR). Double minute chromosomes (DM) were not seen in these cells. The second subline showed a similar karyotype; however, these cells lacked the 8q+ marker and contained one to 37 DM in approximately 90% of the cells examined. Because HL-60 cells are known to contain multiple copies of the c-myc oncogene, in situ chromosomal hybridization of a c-myc probe to HL-60 metaphase cells was performed to localize the amplified genes. The hybridization studies revealed localization to the ABR, as well as to DM, which is consistent with amplification of c-myc within these novel interchangeable chromosomal aberrations.