title: X-ray-induced lymphomagenesis in E mu-pim-1 transgenic mice: an investigation of the co-operating molecular events.
abstract: Transgenic mice overexpressing the pim-1 oncogene in their lymphoid compartment display a low incidence of spontaneous T-cell lymphomas, but are highly susceptible to point mutation-inducing genotoxic carcinogens. We show here that total body X-irradiation, which causes mainly chromosomal deletions, rearrangements and amplifications, significantly enhances lymphoma development in E mu-pim-1 transgenic mice. The X-ray-induced E mu-pim-1 and non-transgenic lymphomas have a comparable high cell turnover as shown by a relatively high S-phase fraction and a high apoptotic activity. Consistent with previous observations, in 75% of all lymphomas c-myc mRNA levels are 5- to 20-fold higher than in control, non-lymphomatous spleen/thymus. The expression of other oncogenes, which have previously found to be activated in combination with pim-1 in lymphomagenesis, such as gfi-1/pal-1, frat-1 and tiam-1, and also of the mdm-2 and mdm-x oncogenes, appeared not to be affected. Deletions and/or rearrangements of the p16INK4A and p15INK4B tumor suppressor genes were seldom observed (in three out of 92 X-ray-induced lymphomas). Strikingly, in addition to the high mRNA levels of the pim-1 transgene, the levels of the endogenous pim-1 transcripts were elevated significantly in 16% of the X-ray-induced E mu-pim-1 lymphomas compared with control spleen, even surpassing the level of the pim-1 transgene mRNA by 3- to 5-fold. In combination with previous results, which showed that the lymphoma incidence increased concordantly with higher levels of pim-1, this supports the notion that pim-1 can contribute to lymphomagenesis in a dose-dependent manner.
authors.affiliation: MGC-Department of Molecular Cell Biology, Leiden University, The Netherlands.
authors.forename: C W
authors.initials: CW
authors.lastname: van der Houven van Oordt
authors.forename: T G
authors.initials: TG
authors.lastname: Schouten
authors.forename: J H
authors.initials: JH
authors.lastname: van Krieken
authors.forename: J H
authors.initials: JH
authors.lastname: van Dierendonck
authors.forename: A J
authors.initials: AJ
authors.lastname: van der Eb
authors.forename: M L
authors.initials: ML
authors.lastname: Breuer
mesh_terms: D000818:Animals; D002352:Carrier Proteins / Q000235:genetics; D018797:Cell Cycle Proteins; D050762:Cyclin-Dependent Kinase Inhibitor p15; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000235:genetics; D005260:Female; D017353:Gene Deletion; D008223:Lymphoma / Q000209:etiology / Q000235:genetics* / Q000473:pathology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D009381:Neoplasms, Radiation-Induced / Q000235:genetics* / Q000473:pathology; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000235:genetics*; D051573:Proto-Oncogene Proteins c-pim-1; D013953:Thymus Neoplasms / Q000235:genetics*; D025521:Tumor Suppressor Proteins; D014916:Whole-Body Irradiation
chemical_list: D002352:Carrier Proteins; C493968:Cdkn2b protein, mouse; D018797:Cell Cycle Proteins; D050762:Cyclin-Dependent Kinase Inhibitor p15; D019941:Cyclin-Dependent Kinase Inhibitor p16; D011518:Proto-Oncogene Proteins; D025521:Tumor Suppressor Proteins; C496636:Pim1 protein, mouse; D017346:Protein Serine-Threonine Kinases; D051573:Proto-Oncogene Proteins c-pim-1