Chromosome banding patterns and breakpoints of three transplantable hepatomas induced in rats by aromatic amines

The chromosome constitution of transplantable hepatomas H-35tc1, 7316A, and 8994 induced in ACI male, BUF female, and BUF male rats, respectively, by monocyclic or polycyclic aromatic amines was studied by Giemsa banding techniques. Hepatoma H-35tc1 was hyperdiploid, with a dominant stemline of 46 chromosomes. The stemline of the heterogeneous 7316A was in the hypotetraploid region (75-8,). Hepatoma 8994 had a near-triploid complement; most metaphase cells and chromosome numbers from 62 to 68. Thirty marker chromosomes were detected. Nineteen rearanged chromosomes were in hepatoma 8994, whereas only 8-10 markers could be found in the 80 +/- 3 chromosome complement of hepatoma 7316A. Two constant common markers were noted: mar2, a chromosome No. 11 with translocation short arm in H-35tc1 and 8994, and mar10 (mar10a), a chromosome No. 1 with a duplicated segment at breakpoint q54 in hepatomas 7316A and 8994. An analysis of the distribution of 232 breakpoints in the rat karyotype, 26 identified in the hepatomas and 206 collected from the literature, revealed a statistically significant excess of breaks in chromosomes No. 1, 2, 3, and 10 (P less than 0.001). The X- and Y-chromosomes showed a considerably lower number of breaks than anticipated (P less than 0.01). Even after a history of continuous transplantation for 10 years, these 3 hepatomas retained intact sex chromosomes that corresponded to the phenotype of the primary host. Preservation of the sex chromosomes in the hepatomas may be attributed to a lower susceptibility of the sex chromosomes than of the autosomes to breakage.