Francis Wiener

Nonrandom chromosome changes involving the Ig gene-carrying chromosomes 12 and 6 in pristane-induced mouse plasmacytomas

The karyotypes of pristane-induced mouse plasmacytomas were studied by G banding. Only primary tumors or early passage generations were analyzed. In contrast to murine T cell leukemias that showed a regular trisomy of chromosome 15, all plasmacytomas showed a consistent translocation of the distal part of chromosome 15 to either chromosome 6 [rcpT(6;15)] or 12 [T(12;15)]. The specific breakpoints were at 6C, 15D3/E ro D2/3 and 12F2. Early passage generations often showed a mixed population with two different translocations, suggesting polyclonal origin. Considered together with the known karyotypic features of murine and human lymphomas, these findings support the theory that the nonrandom chromosomal changes in lymphoproliferative malignancies are associated with the type of the target cell, rather than with the etiological agent. Moreover, the involvement of the chromosomes known to carry the heavy chain (12) and the light chain (6) determinants, respectively, raises the question of whether the translocations may be related to the DNA level rearrangements known to occur during the differentiation of normal plasma cells.

Cytogenetic studies on IgA/lambda-producing murine plasmacytomas: Regular occurrence of a T(12;15) translocation

Seven IgA/lambda-producing murine plasmacytomas had the 12;15 translocation, previously found in IgA/kappa-producing plasmacytomas, and lacked the rcpT(6;15) translocation, also found in some kappa producers. The results suggest that the generation of the 12;15 translocation is an important, perhaps essential event during the genesis of plasmacytomas. The possibility that the distal region of chromosome 15 may contain a “supergene” area involved with the differentiation and/or normal responsiveness of various types of lymphoreticular cells, must be seriously considered on the basis of the present and previous evidence on plasmacytomas, as well as the extensive evidence now available on the role of chromosome 15-changes in the genesis of murine lymphomas. The involvement of chromosome 12 is of interest in view of the fact that it is known to carry the heavy-chain immunoglobulin determinants.

6;7 chromosomal translocation in spontaneously arising rat immunocytomas: evidence for c-myc breakpoint clustering and correlation between isotypic expression and the c-myc target.

Our previous studies have shown that spontaneously arising immunocytomas in the LOU/Ws1 strain of rats contain a t(6;7) chromosomal translocation in all seven tumors studied (F. M. Babonits, J. Spira, G. Klein, and H. Bazin, Int. J. Cancer 29:431-437, 1982). We have also shown that the c-myc is located on chromosome 7 (J. Sümegi, J. Spira, H. Bazin, J. Szpirer, G. Levan, and G. Klein, Nature (London) 306:497-499, 1983) and the immunoglobulin H cluster on chromosome 6 (W.S. Pear, G. Wahlström, J. Szpirer, G. Levan, G. Klein, and J. Sümegi, Immunogenetics 23:393-395, 1986). We now report a detailed cytogenetic and molecular analysis of nine additional rat immunocytomas. The t(6;7) chromosomal translocation is found in all tumors. Mapping of the c-myc breakpoints showed that in 10 of 14 tumors, the c-myc breakpoints are clustered in a 1.5-kilobase region upstream of exon 1. In contrast with sporadic Burkitts lymphoma and mouse plasmacytoma, only 1 of 14 tumors contains the c-myc breakpoints in either exon 1 or intron 1. Analysis of the sequences juxtaposed to the c-myc show that immunoglobulin H switch regions are the targets in at least five tumors and that there is a strong correlation between the secreted immunoglobulin and the c-myc target. Unlike sporadic Burkitts lymphoma and mouse plasmacytoma, at least two rat immunocytomas show recombination of the c-myc with sequences distinct from immunoglobulin switch regions.

Rearrangements of the telomeric region of mouse chromosome 11 in Pre-B ABL/MYC cells revealed by mBANDing, spectral karyotyping, and fluorescence in-situ hybridization with a subtelomeric probe

Previous work has demonstrated that chromosome 11 is trisomic or shows a duplicated region encompassing the E1/E2 band of chromosome 11 in 90% of v-abl/myc-induced plasmacytomas (Wiener et al. 1995). In the present report, we have studied BALB/c PreB lymphocytes that were immortalized by v-abl and stably transfected with a conditional MycER vector (Mai et al. 1999). These cells, termed PreB ABL/MYC, showed changes in the E1/E2 bands of chromosome 11 that are similar to those reported previously for v-abl/myc-induced plasmacytomas. This was shown by the use of chromosome painting, SKY, FISH and mBAND. Our findings suggest that the Pre-B ABL/MYC cells may be used to analyse the genetic changes affecting chromosome 11 that are associated with v-abl/myc-dependent tumorigenesis in mouse B cells.

Chromosomal, histopathological and cell surface marker studies on moloney virus induced lymphomas

Abstract Trisomy of chromosome 15 is a common feature in murine T-cell leukemias of chemical, viral and spontaneous origin. It is not present in all T-cell derived lymphomas, however. In order to study whether trisomy 15 was restricted to a specific T-cell subtype, diploid and chromosome 15 trisomic M-MuLV induced leukemias and derived in vitro lines were compared with regard to histology, karyotype, Thy-1,2 and Lyt-1, 2, 3 and 5 antigen expression. Histologically trisomic lymphomas showed a higher mitotic rate, higher peri-cellular reticulum content and less small cell infiltration than diploid tumors. It was not possible to distinguish trisomic from diploid lymphomas in blind tests based on these criterias, however. Trisomic and diploid lymphoma cells were indistinguishable in morphology. Three of nine lymphomas induced by M-MuLV inoculation were trisomic; two of them were thymomas. Transplantation to syngeneic recipients of the opposite sex and study of the sex chromosome marker was used to establish the origin of the enlarged organ. Upon subcutaneous transplantation, trisomic tumors and thymomas grew locally and were of donor cell type whereas splenic lymphomas caused spleen enlargement, as a rule, and were of donor or recipient type. Transplantation of bone marrow from mice infected with M-MuLV as newborns gave rise to lymphomas with the same sex as the donor and established the presence of preleukemic T-cells in the bone marrow of the donor. In vitro lymphoma lines expressed four different patterns of Lyt antigens: (a) 1.2 + , 2.2 + , 3.2 + , 5.1 + (4 lines); (b) 1.2 + , 2.2 − , 3.2 − , 5.1 + (5 lines); (c) 1.2 + , 2.2 + , 3.2 − , 5.1 + (7 lines); (d) individually distinct patterns (3 lines). Each group contained Thy-1.2 − and Thy-1.2 + lines. The trisomic tumors were mostly in group (a), all of them were Thy-1.2 positive. Diploid tumors were randomly distributed largely between groups (b) and (c). Two of three tumors in group (d) were aneuploid (not trisomic for 15). In spite of the differences observed between trisomic and diploid lymphomas, no specific T-cell subset could be assigned to the two groups. This is in line with the finding of trisomy 15 in some B-cell lymphomas suggesting that this anomaly may contribute to the neoplastic change in a variety of lymphocyte subsets, representing different lineages and steps of differentiation.

Suppression and reappearance of N-tropic L virus production in somatic cell hybrids after introduction and loss of chromosomes carrying Fv-1b.

Abstract Production of the N-tropic L virus was studied in segregating populations of hybrid somatic cells. The hybrids were derived from crosses between A 9 HT, a highly malignant L-cell variant, and normal C 57 Bl lymphocytes or fibroblasts. The presence of the chromosome(s) 4 , derived from the normal partner was assessed by the Gpd- 1 a marker. Chromosome 4 is known to carry the Fv- 1 b locus. Virus production was suppressed in hybrids of the Fv-1 nn × Fv-1 bb type but continued at the same level in Fv-1 nn × Fv-1 nn crosses. In segregating Fv-1 nn × Fv-1 bb hybrid cell populations, the loss of chromosome(s) 4 carrying the Fv- 1 b locus resulted in the reappearance of N-tropic L virus production. This indicates that the Fv- 1 restriction can operate in cells that carry integrated proviral DNA. The hybrids between the malignant and normal cells initially produced few tumors, but selection for tumorigenicity in vivo favored variants that had lost the chromosome(s) 4 derived from the normal parent cell. This provided a convenient method of selecting against the chromosomes carrying Fv- 1 b . The loss of the Gpd- 1 a marker of C 57 Bl origin was regularly accompanied by the resumption of virus production. These results confirm the role of the chromosome(s) 4 derived from the normal parent cell in the suppression of malignancy in somatic cell hybrids.

Cytogenetic Studies on H-2 Alloantigenic Loss Variants Selected from Heterozygous Tumors

Transplantation, serological, and cytogenetic analyses on alloantigenic loss variants selected from heterozygous mouse tumors induced in F1 animals demonstrate that both 17 chromosomes have been maintained in all variants despite complete loss of oneH-2 complex. Small, subchromosomal deletion or mutation remains the most plausible explanation for alloantigenic loss variant formation in diploid or near-diploid heterozygous tumors.

The impact of p53loss on murine plasmacytoma development

Mouse plasmacytomas (PCTs) are characterized by c-myc-activating translocations that juxtapose c-myc on chromosome 15 onto one of the immunoglobulin loci (IgH on chromosome 12, Igκ on chromosome 6, or Igλ on chromosome 16). To assess the impact of p53 loss on PCT genesis, we induced PCTs in p53-deficient BALB/cRb6.15 mouse strains. We show that p53 loss accelerates tumor development and causes a shift in the typical translocation patterns. PCTs that carry variant T(6;15) translocations become as frequent as those with typical T(12;15) translocations (41.66%). In addition, in the absence of p53, the number of translocation-negative PCTs increases from less than 1% to 16.66%. It is noteworthy that neither the shortened latency periods nor the shift in translocation patterns had an impact on the incidence of PCT development. The 42.2% incidence in N3p53−/− mice is similar to the percentages recorded in groups of conventional BALB/cAn mice. The possible mechanisms underlying the accelerated tumorigenesis and the shift in translocation patterns are discussed.

Robertsonian translocation studies on the significance of Trisomy 15 in murine T-cell leukemia☆

G-banding analysis was carried out on T-cell leukemias induced in various Robertsonian mice by 7,12 dimethylbenz(a)anthracene (DMBA), N-methyl-N-nitrosourea (MNU), or Moloney virus. Trisomy 15 was the only regularly seen chromosome aberration whether chromosome No. 15 was involved in a centric fusion or not. Translocated No. 15 chromosomes were not preferentially duplicated. These results show that it is not the translocated state of chromosome No. 15 but the genetic content that is of importance in leukemia development.

Alloantigenic variant selection in vitro from a mouse lymphoma — Sarcoma hybrid

TwoH-2a+/H-2s — alloantigenic loss variants have been obtained from anH-2a+/H-2s+ mouse lymphoma/sarcoma hybrid, YACIR/MSWBS, by in vitro selection, with repeated exposure toanti-H-2s serum and complement. Loss of the MSWBS derivedH-2s complex was associated with the loss of the morphologically distinguishable, translocated MSWBS derived chromosomes 17. The morphologically normal YACIR-derived chromosomes 17 were maintained.