G-bands without pretreatment of slides, in chemically defined conditions

Identification of a chromosomal aberration associated with a hepatitis B DNA integration site in human cells

Hepatitis B virus (HBV) DNA integrates into human cellular DNA during long-term persistent infections, implicating integration as one of the steps leading to hepatocarcinogenesis. The present study demonstrates that the integration of HBV DNA can result in or be accompanied by interchromosomal exchange of genomic material containing the integrated DNA. Unique cellular DNA to the left of an HBV DNA integration site cloned from a primary tumor mapped to chromosome 18q (18q11.1-q11.2); right hand flanking DNA mapped to chromosome #17 at a near-terminal region. The presence of chromosomal rearrangements in association with HBV integration may play a role in multistage hepatocarcinogenesis.

Immortalization of human fibroblasts transformed by origin-defective simian virus 40

Simian virus 40 (SV40)-mediated transformation of human diploid fibroblasts has provided an effective experimental system for studies of both "senescence" in cell culture and carcinogenesis. Previous interpretations may have been complicated, however, by the semipermissive virus-cell interaction. In earlier studies, we previously demonstrated that the human diploid fibroblast line HS74 can be efficiently transformed by DNA from replication-defective mutants of SV40 containing a deletion in the viral origin for DNA synthesis (SVori-). In the current study, we found that such SVori- transformants show a significantly increased life span in culture, as compared with either HS74 or an independent transformant containing an intact viral genome, but they nonetheless undergo senescence. We have clonally isolated six immortalized derivatives of one such transformant (SV/HF-5). Growth studies indicate that the immortalized cell lines do not invariably grow better than SV/HF-5 or HS74. Genetic studies involving karyotypic analysis and Southern analysis of integrated viral sequences demonstrated both random and nonrandom alterations. All immortalized derivatives conserved one of the two copies of SV40 sequences which expressed a truncated T antigen. These cloned SV40-transformed cell lines, pre- and postimmortalization, should be useful in defining molecular changes associated with immortalization.

Immortalization of human fibroblasts transformed by origin-defective simian virus 40

Simian virus 40 (SV40)-mediated transformation of human diploid fibroblasts has provided an effective experimental system for studies of both "senescence" in cell culture and carcinogenesis. Previous interpretations may have been complicated, however, by the semipermissive virus-cell interaction. In earlier studies, we previously demonstrated that the human diploid fibroblast line HS74 can be efficiently transformed by DNA from replication-defective mutants of SV40 containing a deletion in the viral origin for DNA synthesis (SVori-). In the current study, we found that such SVori- transformants show a significantly increased life span in culture, as compared with either HS74 or an independent transformant containing an intact viral genome, but they nonetheless undergo senescence. We have clonally isolated six immortalized derivatives of one such transformant (SV/HF-5). Growth studies indicate that the immortalized cell lines do not invariably grow better than SV/HF-5 or HS74. Genetic studies involving karyotypic analysis and Southern analysis of integrated viral sequences demonstrated both random and nonrandom alterations. All immortalized derivatives conserved one of the two copies of SV40 sequences which expressed a truncated T antigen. These cloned SV40-transformed cell lines, pre- and postimmortalization, should be useful in defining molecular changes associated with immortalization.

Oncogene mobility in a human leukemia line HL-60

HL-60, a cell line derived from a human promyelocytic leukemia, shows amplification of the oncogene c-myc. Chromosome aberrations reported in HL-60 include double minutes (DMs) and an abnormally banded region (ABR) on chromosome #8. A relationship between these chromosomal aberrations and amplification of c-myc DNA has been suggested. We report the localization by cytologic hybridization of amplified c-myc DNA to a marker chromosome, M3q+, in an early passage of HL-60. The localization of c-myc to an ABR on an 8q+ chromosome was confirmed in later passage clones. The most probable derivation of the M3q+ chromosome is t(5p;17q) with additional material associated with c-myc amplification inserted into 17q. This localization is of interest in light of the association between t(15:17) and promyelocytic leukemia. The results indicate that amplification and chromosome integration can occur at a site other than the native gene locus and at different integration sites in different lineages of the same tumor.