1764 Chromosomes and Oncogenes In

The cells from plasmacytomas induced in BALB/c and susceptible BALB/c congenic strains of mice by pristane (2,6,10,14-tetramethylpentadecane) (1) have non-random chromosomal translocations, rcpt (6;15) or rcpt(12;15) (2, 3). To date, the karyotypes of 27 early transfer generation or primary pristine-induced plasmacytomas have determined, and 26 of the tumors have either rcpt(6; 15) or rcpt(12;15) (3-5). The transiocation breakpoints on these chromosomes occur in the same chromosome bands in all the plasmacytomas studied to date. The breakpoints in chromosomes 12 and 15 have been studied by cloning and DNA sequencing. The breakpoint in chromosome 12 occurs in the immunoglobulin heavy chain gene (IgH) ~ complex, frequently, but not always, in the switch region of the alpha heavy chain gene (6-11). In chromosome 15 the breakpoint occurs close to or within the c-myc oncogene (8-12). The breakpoints in chromosome 6 have not yet been determined. Expression of c-myc RNA, often in relatively large amounts, characterized most of the plasmacytomas (11, 13, 14), and rearrangement of c-myc DNA was frequently seen. The development of plasma cell tumors in BALB/c mice injected with pristane alone requires a minimum of 120 d, but usually more than 200 d (15). In contrast, plasmacytomagenesis can be greatly accelerated (5, 16) by infecting pristane-injected mice with Abelson virus. This murine acute leukemia virus contains two retroviral elements, a replication competent Moloney leukemia virus helper and a defective component, A-MuLV (17). The defective element has lost part or all of the viral gag, pol, and env genes and has acquired sequences from the mouse c-abl gene (for review see reference 18). Adult mice of only a This work was supported in part by a Grant-in-Aid for Cancer Research from the Ministry of Education, Science and Culture, Japan, and by grants from the National Cancer Institute, Dept. of Health and Human Services, and The Swedish Cancer Society. 1 Abbreviations used in this paper: ABPC, plasmacytomas induced by Abelson virus plus pristane; A-MuLV, Abelson murine leukemia virus; IgH, immunoglobulin heavy chain; i.p., intraperitoneal; LTR, long terminal repeats of retroviruses; rcpt, reciprocal chromosome transiocation.