Chromosomal translocations with specific breakpoints in asbestos-induced rat mesotheliomas.

Cytogenetic analysis was conducted on cells of 15 rat mesotheliomas induced in rats by the i.p. inoculation of crocidolite or chrysotile asbestos. These tumor cells were diploid, triploid, or tetraploid. All tumor lines exhibited aneuploidy and marker chromosomes. Loss of at least one copy of the X chromosome was observed in each of the tumors analyzed, and loss of copies of chromosomes 8, 16, 20, or 18 characterized at least six of the tumors. Translocations were observed in 12 tumors, with six chromosome rearrangements present in at least two different tumors. However, the breakpoints were not always identical. On the other hand, translocations involving chromosomes 5, 10, and 13 exhibited repeated breakage at the same loci. Such specific and repetitive translocations may be involved in the process of asbestos-induced tumor development.