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Myc suppression of Nfkb2 accelerates lymphomagenesis.

Keller U, Huber J, Nilsson JA, Fallahi M, Hall MA, Peschel C, Cleveland JL - BMC Cancer (2010)

Bottom Line: NFKB2 suppression by Myc was also confirmed in primary human BL.Nfkb2 is suppressed by c-Myc and harnesses Myc-driven lymphomagenesis.These data thus link Myc-driven lymphomagenesis to the non-canonical NF-kappaB pathway.

View Article: PubMed Central - HTML - PubMed

Affiliation: III. Medical Department, Technische Universität München, Munich, Germany. ulrich.keller@lrz.tum.de

ABSTRACT

Background: Deregulated c-Myc expression is a hallmark of several human cancers where it promotes proliferation and an aggressive tumour phenotype. Myc overexpression is associated with reduced activity of Rel/NF-kappaB, transcription factors that control the immune response, cell survival, and transformation, and that are frequently altered in cancer. The Rel/NF-kappaB family member NFKB2 is altered by chromosomal translocations or deletions in lymphoid malignancies and deletion of the C-terminal ankyrin domain of NF-kappaB2 augments lymphocyte proliferation.

Methods: Precancerous Emicro-Myc-transgenic B cells, Emicro-Myc lymphomas and human Burkitt lymphoma samples were assessed for Nfkb2 expression. The contribution of Nfkb2 to Myc-driven apoptosis, proliferation, and lymphomagenesis was tested genetically in vivo.

Results: Here we report that the Myc oncoprotein suppresses Nfkb2 expression in vitro in primary mouse fibroblasts and B cells, and in vivo in the Emicro-Myc transgenic mouse model of human Burkitt lymphoma (BL). NFKB2 suppression by Myc was also confirmed in primary human BL. Promoter-reporter assays indicate that Myc-mediated suppression of Nfkb2 occurs at the level of transcription. The contribution of Nfkb2 to Myc-driven lymphomagenesis was tested in vivo, where Nfkb2 loss was shown to accelerate lymphoma development in Emicro-Myc transgenic mice, by impairing Myc's apoptotic response.

Conclusions: Nfkb2 is suppressed by c-Myc and harnesses Myc-driven lymphomagenesis. These data thus link Myc-driven lymphomagenesis to the non-canonical NF-kappaB pathway.

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Nfkb2 loss accelerates Myc-induced lymphomagenesis by impairing apoptosis. a) Effects of Nfkb2 deficiency on Myc-induced lymphomagenesis. The survival of Eμ-Myc transgenic littermates of the indicated Nfkb2 genotypes is shown. The differences in the rates of tumor incidence between the Nfkb2+/+ and the Nfkb2-/- littermates is statistically significant (p = 0.0307). b) Eμ-Myc transgenic littermates of the indicated Nfkb2 genotypes were injected with BrdU, and cells from bone marrow and spleen were harvested 12 hr later. BrdU-incorporation was analyzed using an antibody-dependent fluorescence assay. The bars show the mean percentage of cells in S phase ± SEM (three independent experiments). c) The apoptotic index of the indicated genotypes was analyzed using an antibody dependent fluorescence assay. Annexin V+ B220+ cells of sIgM- or sIgM+ phenotype are shown. The bars represent the mean ± SEM from three independent experiments. * indicates p < 0.05.
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Figure 4: Nfkb2 loss accelerates Myc-induced lymphomagenesis by impairing apoptosis. a) Effects of Nfkb2 deficiency on Myc-induced lymphomagenesis. The survival of Eμ-Myc transgenic littermates of the indicated Nfkb2 genotypes is shown. The differences in the rates of tumor incidence between the Nfkb2+/+ and the Nfkb2-/- littermates is statistically significant (p = 0.0307). b) Eμ-Myc transgenic littermates of the indicated Nfkb2 genotypes were injected with BrdU, and cells from bone marrow and spleen were harvested 12 hr later. BrdU-incorporation was analyzed using an antibody-dependent fluorescence assay. The bars show the mean percentage of cells in S phase ± SEM (three independent experiments). c) The apoptotic index of the indicated genotypes was analyzed using an antibody dependent fluorescence assay. Annexin V+ B220+ cells of sIgM- or sIgM+ phenotype are shown. The bars represent the mean ± SEM from three independent experiments. * indicates p < 0.05.

Mentions: The remarkable changes in the expression of components of the Rel/NF-κB signalling pathway, and particularly the suppression of Nfkb2 by c-Myc, suggested that NF-kB2 might play critical roles in Myc-driven tumorigenesis. If Myc-mediated reductions in Nfkb2 expression in Eμ-Myc B cells were important for Myc-mediated lymphomagenesis, we reasoned that total loss of Nfkb2 should affect lymphoma development. To test this hypothesis, Eμ-Myc transgenic mice were mated to Nfkb2-/- mice [6] and F1 offspring were bred to Nfkb2+/- mice to obtain the desired Eμ-Myc;Nfkb2+/+ and Eμ-Myc;Nfkb2-/- cohorts. These littermates were then observed for lymphoma onset. Eμ-Myc transgenic mice usually succumb to aggressive lymphoma within 4-8 months of birth [23]. As expected, non-transgenic Nfkb2-/- littermates showed no signs of tumour development throughout their lifespan (data not shown). Importantly, Eμ-Myc;Nfkb2-/- transgenic displayed a moderately accelerated course of lymphoma development and, accordingly, had a shorter lifespan, with a median survival of 171 days compared to 205 days median survival in their Eμ-Myc;Nfkb2+/+ littermates (Figure 4a, p = 0.0307). The lymphomas that arose in Eμ-Myc;Nfkb2-/- transgenics were phenotypically identical to those that arose in Eμ-Myc;Nfkb2+/+ mice, and full necropsy and histopathological examination demonstrated similar dissemination of disease in Eμ-Myc;Nfkb2+/+ versus Eμ-Myc;Nfkb2-/- mice (data not shown). Thus, Nfkb2 loss accelerates Myc-driven lymphomagenesis without overtly affecting the disease phenotype.


Myc suppression of Nfkb2 accelerates lymphomagenesis.

Keller U, Huber J, Nilsson JA, Fallahi M, Hall MA, Peschel C, Cleveland JL - BMC Cancer (2010)

Nfkb2 loss accelerates Myc-induced lymphomagenesis by impairing apoptosis. a) Effects of Nfkb2 deficiency on Myc-induced lymphomagenesis. The survival of Eμ-Myc transgenic littermates of the indicated Nfkb2 genotypes is shown. The differences in the rates of tumor incidence between the Nfkb2+/+ and the Nfkb2-/- littermates is statistically significant (p = 0.0307). b) Eμ-Myc transgenic littermates of the indicated Nfkb2 genotypes were injected with BrdU, and cells from bone marrow and spleen were harvested 12 hr later. BrdU-incorporation was analyzed using an antibody-dependent fluorescence assay. The bars show the mean percentage of cells in S phase ± SEM (three independent experiments). c) The apoptotic index of the indicated genotypes was analyzed using an antibody dependent fluorescence assay. Annexin V+ B220+ cells of sIgM- or sIgM+ phenotype are shown. The bars represent the mean ± SEM from three independent experiments. * indicates p < 0.05.
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Figure 4: Nfkb2 loss accelerates Myc-induced lymphomagenesis by impairing apoptosis. a) Effects of Nfkb2 deficiency on Myc-induced lymphomagenesis. The survival of Eμ-Myc transgenic littermates of the indicated Nfkb2 genotypes is shown. The differences in the rates of tumor incidence between the Nfkb2+/+ and the Nfkb2-/- littermates is statistically significant (p = 0.0307). b) Eμ-Myc transgenic littermates of the indicated Nfkb2 genotypes were injected with BrdU, and cells from bone marrow and spleen were harvested 12 hr later. BrdU-incorporation was analyzed using an antibody-dependent fluorescence assay. The bars show the mean percentage of cells in S phase ± SEM (three independent experiments). c) The apoptotic index of the indicated genotypes was analyzed using an antibody dependent fluorescence assay. Annexin V+ B220+ cells of sIgM- or sIgM+ phenotype are shown. The bars represent the mean ± SEM from three independent experiments. * indicates p < 0.05.
Mentions: The remarkable changes in the expression of components of the Rel/NF-κB signalling pathway, and particularly the suppression of Nfkb2 by c-Myc, suggested that NF-kB2 might play critical roles in Myc-driven tumorigenesis. If Myc-mediated reductions in Nfkb2 expression in Eμ-Myc B cells were important for Myc-mediated lymphomagenesis, we reasoned that total loss of Nfkb2 should affect lymphoma development. To test this hypothesis, Eμ-Myc transgenic mice were mated to Nfkb2-/- mice [6] and F1 offspring were bred to Nfkb2+/- mice to obtain the desired Eμ-Myc;Nfkb2+/+ and Eμ-Myc;Nfkb2-/- cohorts. These littermates were then observed for lymphoma onset. Eμ-Myc transgenic mice usually succumb to aggressive lymphoma within 4-8 months of birth [23]. As expected, non-transgenic Nfkb2-/- littermates showed no signs of tumour development throughout their lifespan (data not shown). Importantly, Eμ-Myc;Nfkb2-/- transgenic displayed a moderately accelerated course of lymphoma development and, accordingly, had a shorter lifespan, with a median survival of 171 days compared to 205 days median survival in their Eμ-Myc;Nfkb2+/+ littermates (Figure 4a, p = 0.0307). The lymphomas that arose in Eμ-Myc;Nfkb2-/- transgenics were phenotypically identical to those that arose in Eμ-Myc;Nfkb2+/+ mice, and full necropsy and histopathological examination demonstrated similar dissemination of disease in Eμ-Myc;Nfkb2+/+ versus Eμ-Myc;Nfkb2-/- mice (data not shown). Thus, Nfkb2 loss accelerates Myc-driven lymphomagenesis without overtly affecting the disease phenotype.

Bottom Line: NFKB2 suppression by Myc was also confirmed in primary human BL.Nfkb2 is suppressed by c-Myc and harnesses Myc-driven lymphomagenesis.These data thus link Myc-driven lymphomagenesis to the non-canonical NF-kappaB pathway.

View Article: PubMed Central - HTML - PubMed

Affiliation: III. Medical Department, Technische Universität München, Munich, Germany. ulrich.keller@lrz.tum.de

ABSTRACT

Background: Deregulated c-Myc expression is a hallmark of several human cancers where it promotes proliferation and an aggressive tumour phenotype. Myc overexpression is associated with reduced activity of Rel/NF-kappaB, transcription factors that control the immune response, cell survival, and transformation, and that are frequently altered in cancer. The Rel/NF-kappaB family member NFKB2 is altered by chromosomal translocations or deletions in lymphoid malignancies and deletion of the C-terminal ankyrin domain of NF-kappaB2 augments lymphocyte proliferation.

Methods: Precancerous Emicro-Myc-transgenic B cells, Emicro-Myc lymphomas and human Burkitt lymphoma samples were assessed for Nfkb2 expression. The contribution of Nfkb2 to Myc-driven apoptosis, proliferation, and lymphomagenesis was tested genetically in vivo.

Results: Here we report that the Myc oncoprotein suppresses Nfkb2 expression in vitro in primary mouse fibroblasts and B cells, and in vivo in the Emicro-Myc transgenic mouse model of human Burkitt lymphoma (BL). NFKB2 suppression by Myc was also confirmed in primary human BL. Promoter-reporter assays indicate that Myc-mediated suppression of Nfkb2 occurs at the level of transcription. The contribution of Nfkb2 to Myc-driven lymphomagenesis was tested in vivo, where Nfkb2 loss was shown to accelerate lymphoma development in Emicro-Myc transgenic mice, by impairing Myc's apoptotic response.

Conclusions: Nfkb2 is suppressed by c-Myc and harnesses Myc-driven lymphomagenesis. These data thus link Myc-driven lymphomagenesis to the non-canonical NF-kappaB pathway.

Show MeSH
Related in: MedlinePlus