title: Enhanced expression and state of the c-myc oncogene in chemically and X-ray-transformed C3H/10T1/2 Cl 8 mouse embryo fibroblasts.
abstract: We examined expression of the c-myc oncogene in nontransformed, in three chemically transformed, and in two X-ray-transformed C3H/10T1/2 Cl 8 cell lines. In nontransformed C3H/10T1/2 cells, c-myc was expressed when cells were logarithmically growing, and expression decreased as cells reached confluence. In a methylcholanthrene-transformed cell line, MCA Si 24, c-myc expression was similar to that observed in nontransformed cells, while in two chemically transformed cell lines, Bleo Cl 2 and DMBA Cl 2, and in two radiation-transformed cell lines, F17 and F29, steady-state levels of the c-myc transcript were 5-7-fold greater than observed in nontransformed C3H/10T1/2 cells. All cell lines, both transformed and nontransformed, produced a 2.3-kilobase c-myc transcript. There was no detectable amplification or rearrangement of c-myc DNA sequences in any of the cell lines examined as determined by DNA dot blot and restriction endonuclease-Southern blotting analyses. In addition, the c-myc gene in nontransformed and transformed cell lines showed similar methylation patterns as determined by HpaII/MpsI digestion analysis, except that F19 and F29 cells lost a 0.95-kilobase HpaII band, suggesting extra region-specific methylation in these two cell lines compared to C3H/10T1/2 cells. Therefore, increased c-myc expression in the four transformed lines did not generally correlate with changes in DNA methylation in the vicinity of the c-myc gene. Our results suggest that expression of the c-myc gene is growth related and that elevated steady-state levels of c-myc RNA in certain chemically and X-ray transformed C3H/10T1/2 cell lines, such as Bleo Cl 2, DMBA Cl 2, F17, and F29, are correlated with and may participate in conversion to or maintenance of cells in the transformed state.
mesh_terms: D015127:9,10-Dimethyl-1,2-benzanthracene; D000818:Animals; D001761:Bleomycin; D002460:Cell Line; D002471:Cell Transformation, Neoplastic; D004262:DNA Restriction Enzymes / Q000378:metabolism; D005347:Fibroblasts / Q000032:analysis* / Q000187:drug effects / Q000528:radiation effects; D005786:Gene Expression Regulation / Q000187:drug effects / Q000528:radiation effects; D008748:Methylcholanthrene; D051379:Mice; D008809:Mice, Inbred C3H; D009374:Neoplasms, Experimental / Q000139:chemically induced; D009857:Oncogenes; D012334:RNA, Neoplasm / Q000032:analysis
chemical_list: D012334:RNA, Neoplasm; D001761:Bleomycin; D008748:Methylcholanthrene; D015127:9,10-Dimethyl-1,2-benzanthracene; D004262:DNA Restriction Enzymes