| 1. |
- Wang, Y, et al.
(author)
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Functional homology between N-myc and c-myc in murine plasmacytomagenesis : plasmacytoma development in N-myc transgenic mice
- 1992
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In: Oncogene. - 0950-9232. ; 7:6, s. 7-1241
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Journal article (peer-reviewed)abstract
- Mouse plasmacytomas induced by pristane oil alone, or in combination with Abelson murine leukemia virus (A-MuLV), regularly carry one of three alternative chromosomal translocations that juxtapose c-myc to immunoglobulin heavy- or light-chain loci. E mu-c-myc transgenic mice develop translocation-free plasmacytomas after induction by pristane oil and/or A-MuLV [Sugiyama, H., Silva, S., Wang, Y., Weber, G., Babonits, M., Rosen, A., Wiener, F. & Klein, G. (1990). Int. J. Cancer, 46, 845-852]. In order to test whether another member of the myc family, N-myc, could play a similar role as c-myc, we treated E mu-N-myc transgenic mice with pristane and helper-free A-MuLV. Of 20 mice that received a single pristane injection followed by A-MuLV, 17 developed plasmacytomas with a mean latency period of 54 +/- 20 days. In a corresponding group that only received a single pristane injection, five out of six transgenic mice developed plasmacytomas with a mean latency period of 142 +/- 32 days. However, after three monthly injections of pristane, all 15 transgenic mice developed plasmacytomas with a mean latency period of 128 +/- 20 days. All plasmacytomas expressed the N-myc transgene, while none of them expressed either c-myc or endogenous N-myc. None of the tumors carried the usual plasmacytoma-associated translocations.
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| 2. |
- Henriksson, M, et al.
(author)
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Nuclear colocalization of c-myc protein and hsp70 in cells transfected with human wild-type and mutant c-myc genes
- 1992
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In: Experimental Cell Research. - 0014-4827. ; 203:2, s. 94-383
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Journal article (peer-reviewed)abstract
- Using immunofluorescence and electron microscopy we have studied the localization of wild-type and mutant c-myc proteins transiently expressed in CV-1 cells. In agreement with our previous observations, wild-type c-myc protein accumulated in large amorphous globules in the nucleus. All mutant proteins tested accumulated in the nucleus as well, but gave rise to morphologically different inclusion bodies. Many small globules appeared in cells transfected with D145-262 (deletion of amino acids 145-262), while cells transfected with D371-412 or D414-433 generated structures looking like a fine network or like beads on a string. In addition, a particulate cytoplasmic staining appeared in some cells transfected with the wild-type gene and in cells transfected with mutants D145-262 or D414-433. Since the c-myc protein has been reported to stimulate expression of exogenous hsp70 protein, we also examined the intracellular distribution of hsp70 in the transfected cells. Double immunofluorescence microscopy revealed that hsp70 codistributed with the c-myc protein in distinct globules in the nucleus of many but not all myc-positive cells. However, the levels of hsp70 transcripts were not significantly raised compared to nontransfected and vector-transfected cells. Likewise, the levels of hsp70 protein did not vary significantly. These findings indicate that overexpression of c-myc stimulates translocation of preexisting hsp70 from the cytoplasm into the nucleus, rather than influencing hsp70 expression. Conceivably, this may represent one of several mechanisms whereby the cell deals with excessive amounts of c-myc protein.
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| 3. |
- Axelson, H, et al.
(author)
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Juxtaposition of N-myc and Ig kappa through a reciprocal t(6;12) translocation in a mouse plasmacytoma
- 1994
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In: Genes, Chromosomes and Cancer. - 1045-2257. ; 11:2, s. 85-90
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Journal article (peer-reviewed)abstract
- Nearly all mouse plasmacytomas (MPCs) carry an Ig/myc translocation. Any one of the three Ig loci may participate, while the myc contribution has been limited to c-myc, excluding other members of the myc gene family. The same is true for the other two known Ig/myc translocation-carrying tumors, Burkitt's lymphoma and rat immunocytoma. It is believed that the Ig/myc juxtaposition plays a decisive, rate limiting role in the genesis of the three tumors, acting through the constitutive activation of myc that makes it refractory to normal regulation. Here we describe the molecular analysis of a unique t(6;12)(CI;B) translocation that we previously identified in an exceptional MPC that expressed N-myc but not c-myc. We now show that the translocation led to the juxtaposition of N-myc and Ig kappa. This is the first case of an Ig/myc-carrying tumor that involves N-myc rather than c-myc. These findings suggest that the translocation may already have occurred at the pro- or pre-B cell stage at which N-myc is open for transcription. According to this interpretation, constitutive activation of N-myc would suppress the expression of c-myc, but would not interfere with the differentiation of the pro-B cell into a fully mature plasma cell. Its tumorigenic influence would become manifest only at the time when the cell would normally be programmed to leave the cycling compartment, in connection with its terminal differentiation.
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| 4. |
- Imreh, S, et al.
(author)
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Hypersomy of chromosome 15 with retrovirally rearranged c-myc, loss of germline c-myc and IgK/c-myc juxtaposition in a macrophage-monocytic tumour line
- 1994
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In: European Journal of Cancer. - 0959-8049. ; 30A:7, s. 994-1002
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Journal article (peer-reviewed)abstract
- From a lymphoid tumour induced by 7,12-dimethylbenz-[a]-anthracene (DMBA) + methyl-N-nitrose-N-urea (MNU) in an [AKR Rb(6.15) x CBAT6T6]F1 mouse, a macrophage- monocyte line (KT-10) was isolated. Following ethyl methanesulfonate (EMS) treatment, a bromodeoxyuridine (BUdR) resistant subline was selected. Serial propagation of this line in vitro in the presence of BUdR (28 months) with periodic cytogenetic and molecular examinations, has led to the definition of four successive stages. During stage I, the cells were trisomic for chromosome 15. They contained Rb(6.15) and Rb(del6.15) of AKR and T(14;15) of CBA origin. Southern blotting showed the presence of both germline (G) and rearranged (R) c-myc. At stage II, Rb(del6.15) has duplicated. Both Rb(6.15) and T(14;15) persisted together with G-myc and R-myc. In stage III, the CBA-derived T(14;15) was lost, in parallel with G-myc. At this stage, a Dic.In(6.15) was detected. One of its arms was cytogenetically identical with the long arm of In(6.15) in the variant IgK/myc translocations. This chromosome carried R-myc and IgK in juxtaposition, as indicated by comigration on pulsed field electrophoresis (PFGE). At stage IV, the R-myc carrying AKR-derived chromosome 15s were present in six copies. Possible relationships between the increasing R/G myc ratio and changed growth characteristics in vivo and in vitro are discussed.
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