| 1. |
- Klionsky, Daniel J., et al.
(author)
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Guidelines for the use and interpretation of assays for monitoring autophagy in higher eukaryotes
- 2008
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In: Autophagy. - : Landes Bioscience. - 1554-8627 .- 1554-8635. ; 4:2, s. 151-175
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Research review (peer-reviewed)abstract
- Research in autophagy continues to accelerate,1 and as a result many new scientists are entering the field. Accordingly, it is important to establish a standard set of criteria for monitoring macroautophagy in different organisms. Recent reviews have described the range of assays that have been used for this purpose.2,3 There are many useful and convenient methods that can be used to monitor macroautophagy in yeast, but relatively few in other model systems, and there is much confusion regarding acceptable methods to measure macroautophagy in higher eukaryotes. A key point that needs to be emphasized is that there is a difference between measurements that monitor the numbers of autophagosomes versus those that measure flux through the autophagy pathway; thus, a block in macroautophagy that results in autophagosome accumulation needs to be differentiated from fully functional autophagy that includes delivery to, and degradation within, lysosomes (in most higher eukaryotes) or the vacuole (in plants and fungi). Here, we present a set of guidelines for the selection and interpretation of the methods that can be used by investigators who are attempting to examine macroautophagy and related processes, as well as by reviewers who need to provide realistic and reasonable critiques of papers that investigate these processes. This set of guidelines is not meant to be a formulaic set of rules, because the appropriate assays depend in part on the question being asked and the system being used. In addition, we emphasize that no individual assay is guaranteed to be the most appropriate one in every situation, and we strongly recommend the use of multiple assays to verify an autophagic response.
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| 2. |
- Garrison, Sean P, et al.
(author)
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Selection against PUMA gene expression in Myc-driven B-cell lymphomagenesis.
- 2008
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In: Molecular and cellular biology. - 1098-5549. ; 28:17, s. 5391-402
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Journal article (peer-reviewed)abstract
- The p53 tumor suppressor pathway limits oncogenesis by inducing cell cycle arrest or apoptosis. A key p53 target gene is PUMA, which encodes a BH3-only proapoptotic protein. Here we demonstrate that Puma deletion in the Emu-Myc mouse model of Burkitt lymphoma accelerates lymphomagenesis and that approximately 75% of Emu-Myc lymphomas naturally select against Puma protein expression. Furthermore, approximately 40% of primary human Burkitt lymphomas fail to express detectable levels of PUMA and in some tumors this is associated with DNA methylation. Burkitt lymphoma cell lines phenocopy the primary tumors with respect to DNA methylation and diminished PUMA expression, which can be reactivated following inhibition of DNA methyltransferases. These findings establish that PUMA is silenced in human malignancies, and they suggest PUMA as a target for the development of novel chemotherapeutics.
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| 3. |
- Nilsson, Jonas A, et al.
(author)
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Targeting ornithine decarboxylase in Myc-induced lymphomagenesis prevents tumor formation.
- 2005
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In: Cancer Cell. - 1535-6108. ; 7:5, s. 433-44
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Journal article (peer-reviewed)abstract
- Checkpoints that control Myc-mediated proliferation and apoptosis are bypassed during tumorigenesis. Genes encoding polyamine biosynthetic enzymes are overexpressed in B cells from E mu-Myc transgenic mice. Here, we report that disabling one of these Myc targets, Ornithine decarboxylase (Odc), abolishes Myc-induced suppression of the Cdk inhibitors p21(Cip1) and p27(Kip1), thereby impairing Myc's proliferative, but not apoptotic, response. Moreover, lymphoma development was markedly delayed in E mu-Myc;Odc(+/-) transgenic mice and in E mu-Myc mice treated with the Odc inhibitor difluoromethylornithine (DFMO). Strikingly, tumors ultimately arising in E mu-Myc;Odc(+/-) transgenics lacked deletions of Arf, suggesting that targeting Odc forces other routes of transformation. Therefore, Odc is a critical Myc transcription target that regulates checkpoints that guard against tumorigenesis and is an effective target for cancer chemoprevention.
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| 4. |
- Cardone, Monica, et al.
(author)
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The novel ETS factor TEL2 cooperates with Myc in B lymphomagenesis.
- 2005
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In: Mol Cell Biol. - 0270-7306. ; 25:6, s. 2395-405
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Journal article (peer-reviewed)abstract
- The human ETS family gene TEL2/ETV7 is highly homologous to TEL1/ETV6, a frequent target of chromosome translocations in human leukemia and specific solid tumors. Here we report that TEL2 augments the proliferation and survival of normal mouse B cells and dramatically accelerates lymphoma development in Emu-Myc transgenic mice. Nonetheless, inactivation of the p53 pathway was a hallmark of all TEL2/Emu-Myc lymphomas, indicating that TEL2 expression alone is insufficient to bypass this apoptotic checkpoint. Although TEL2 is infrequently up-regulated in human sporadic Burkitt's lymphoma, analysis of pediatric B-cell acute lymphocytic leukemia (B-ALL) samples showed increased coexpression of TEL2 and MYC and/or MYCN in over one-third of B-ALL patients. Therefore, TEL2 and MYC also appear to cooperate in provoking a cadre of human B-cell malignancies.
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| 5. |
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| 6. |
- Gatenby, Robert A., et al.
(author)
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Lung adenocarcinomas without driver genes converge to common adaptive strategies through diverse genetic, epigenetic, and niche construction evolutionary pathways
- 2024
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In: Medical Oncology. - 1357-0560. ; 41:6
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Journal article (peer-reviewed)abstract
- Somatic evolution selects cancer cell phenotypes that maximize survival and proliferation in dynamic environments. Although cancer cells are molecularly heterogeneous, we hypothesized convergent adaptive strategies to common host selection forces can be inferred from patterns of epigenetic and genetic evolutionary selection in similar tumors. We systematically investigated gene mutations and expression changes in lung adenocarcinomas with no common driver genes (n = 313). Although 13,461 genes were mutated in at least one sample, only 376 non-synonymous mutations evidenced positive evolutionary selection with conservation of 224 genes, while 1736 and 2430 genes exhibited ≥ two-fold increased and ≥ 50% decreased expression, respectively. Mutations under positive selection are more frequent in genes with significantly altered expression suggesting they often “hardwire” pre-existing epigenetically driven adaptations. Conserved genes averaged 16-fold higher expression in normal lung tissue compared to those with selected mutations demonstrating pathways necessary for both normal cell function and optimal cancer cell fitness. The convergent LUAD phenotype exhibits loss of differentiated functions and cell–cell interactions governing tissue organization. Conservation with increased expression is found in genes associated with cell cycle, DNA repair, p53 pathway, epigenetic modifiers, and glucose metabolism. No canonical driver gene pathways exhibit strong positive selection, but extensive down-regulation of membrane ion channels suggests decreased transmembrane potential may generate persistent proliferative signals. NCD LUADs perform niche construction generating a stiff, immunosuppressive microenvironment through selection of specific collagens and proteases. NCD LUADs evolve to a convergent phenotype through a network of interconnected genetic, epigenetic, and ecological pathways.
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| 7. |
- Hemann, Michael T, et al.
(author)
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Evasion of the p53 tumour surveillance network by tumour-derived MYC mutants.
- 2005
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In: Nature. - 1476-4687. ; 436:7052, s. 807-11
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Journal article (peer-reviewed)abstract
- The c-Myc oncoprotein promotes proliferation and apoptosis, such that mutations that disable apoptotic programmes often cooperate with MYC during tumorigenesis. Here we report that two common mutant MYC alleles derived from human Burkitt's lymphoma uncouple proliferation from apoptosis and, as a result, are more effective than wild-type MYC at promoting B cell lymphomagenesis in mice. Mutant MYC proteins retain their ability to stimulate proliferation and activate p53, but are defective at promoting apoptosis due to a failure to induce the BH3-only protein Bim (a member of the B cell lymphoma 2 (Bcl2) family) and effectively inhibit Bcl2. Disruption of apoptosis through enforced expression of Bcl2, or loss of either Bim or p53 function, enables wild-type MYC to produce lymphomas as efficiently as mutant MYC. These data show how parallel apoptotic pathways act together to suppress MYC-induced transformation, and how mutant MYC proteins, by selectively disabling a p53-independent pathway, enable tumour cells to evade p53 action during lymphomagenesis.
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| 8. |
- Hoellein, Alexander, et al.
(author)
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Myc-induced SUMOylation is a therapeutic vulnerability for B-cell lymphoma.
- 2014
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In: Blood. - : American Society of Hematology. - 1528-0020 .- 0006-4971. ; 124:13, s. 2081-90
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Journal article (peer-reviewed)abstract
- Myc oncogenic transcription factors (c-Myc, N-Myc, and L-Myc) coordinate the control of cell growth, division, and metabolism. In cancer, Myc overexpression is often associated with aggressive disease, which is in part due to the destruction of select targets by the ubiquitin-proteasome system (eg, SCF(Skp2)-directed destruction of the Cdk inhibitor p27(Kip1)). We reasoned that Myc would also regulate SUMOylation, a related means of posttranslational modification of proteins, and that this circuit would play essential roles in Myc-dependent tumorigenesis. Here, we report marked increases in the expression of genes that encode regulators and components of the SUMOylation machinery in mouse and human Myc-driven lymphomas, resulting in hyper-SUMOylation in these tumors. Further, inhibition of SUMOylation by genetic means disables Myc-induced proliferation, triggering G2/M cell-cycle arrest, polyploidy, and apoptosis. Using genetically defined cell models and conditional expression systems, this response was shown to be Myc specific. Finally, in vivo loss-of-function and pharmacologic studies demonstrated that inhibition of SUMOylation provokes rapid regression of Myc-driven lymphoma. Thus, targeting SUMOylation represents an attractive therapeutic option for lymphomas with MYC involvement.
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| 9. |
- Keller, Ulrich B, et al.
(author)
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Myc targets Cks1 to provoke the suppression of p27Kip1, proliferation and lymphomagenesis.
- 2007
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In: EMBO J. - 0261-4189. ; 26:10, s. 2562-74
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Journal article (peer-reviewed)abstract
- Reduced levels of the cyclin-dependent kinase inhibitor p27(Kip1) connote poor prognosis in cancer. In human Burkitt lymphoma and in precancerous B cells and lymphomas arising in Emu-Myc transgenic mice, p27(Kip1) expression is markedly reduced. We show that the transcription of the Cks1 component of the SCF(Skp2) complex that is necessary for p27(Kip1) ubiquitylation and degradation is induced by Myc. Further, Cks1 expression is elevated in precancerous Emu-Myc B cells, and high levels of Cks1 are also a hallmark of Emu-Myc lymphoma and of human Burkitt lymphoma. Finally, loss of Cks1 in Emu-Myc B cells elevates p27(Kip1) levels, reduces proliferation and markedly delays lymphoma development and dissemination of disease. Therefore, Myc suppresses p27(Kip1) expression, accelerates cell proliferation and promotes tumorigenesis at least in part through its ability to selectively induce Cks1.
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| 10. |
- Keller, Ulrich, et al.
(author)
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Myc suppression of Nfkb2 accelerates lymphomagenesis
- 2010
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In: BMC Cancer. - : Springer Science and Business Media LLC. - 1471-2407. ; 10
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Journal article (peer-reviewed)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-kappa B, transcription factors that control the immune response, cell survival, and transformation, and that are frequently altered in cancer. The Rel/NF-kappa B family member NFKB2 is altered by chromosomal translocations or deletions in lymphoid malignancies and deletion of the C-terminal ankyrin domain of NF-kappa B2 augments lymphocyte proliferation. Methods: Precancerous E mu-Myc-transgenic B cells, E mu-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 E mu-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 E mu-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-kappa B pathway.
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| 11. |
- Keller, Ulrich, et al.
(author)
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Nfkb 1 is dispensable for Myc-induced lymphomagenesis.
- 2005
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In: Oncogene. - 0950-9232. ; 24:41, s. 6231-40
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Journal article (peer-reviewed)abstract
- Rel/NF-kappaB transcription factors are critical arbiters of immune responses, cell survival, and transformation, and are frequently deregulated in cancer. The p50 NF-kappaB 1 component of Rel/NF-kappaB DNA-binding dimers regulates genes involved in both cell cycle traverse and apoptosis. Nfkb 1 loss accelerates B cell growth and leads to increased B cell turnover in vivo, phenotypes akin to those manifested in B cells of Emu-Myc transgenic mice, a model of human Burkitt lymphoma. Interestingly, Emu-Myc B cells express reduced levels of cytoplasmic and nuclear NF-kappaB 1 and have reduced Rel/NF-kappaB DNA-binding activity, suggesting that Myc-mediated repression of NF-kappaB 1 might mediate its proliferative and apoptotic effects on B cells. Furthermore, Nfkb 1 expression was reduced in the majority of Emu-Myc lymphomas and was also suppressed in human Burkitt lymphoma. Nonetheless, loss of Nfkb 1 did not appreciably affect Myc's proliferative or apoptotic responses in B cells and had no effect on lymphoma development in Emu-Myc mice. Therefore, Nfkb 1 is dispensable for Myc-induced lymphomagenesis.. Oncogene (2005) 24, 6231-6240
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| 12. |
- Nilsson, Jonas A, et al.
(author)
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Id2 is dispensable for myc-induced lymphomagenesis.
- 2004
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In: Cancer Res. - 0008-5472. ; 64:20, s. 7296-301
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Journal article (peer-reviewed)abstract
- The Emu-Myc transgenic mouse appears to be an accurate model of human Burkitt's lymphoma that bears MYC/Immunoglobulin gene translocations. Id2, a negative regulator of basic helix-loop-helix transcription factors, has also been proposed as a Myc target gene that drives the proliferative response of Myc by binding to and overriding the checkpoint functions of the retinoblastoma tumor suppressor protein. Targeted deletion of Id2 in mice results in defects in B-cell development and prevents the development of peripheral lymphoid nodes. In precancerous B cells and lymphomas that arise in Emu-Myc transgenic mice and in Burkitt's lymphomas, Id2 is overexpressed, suggesting that it plays a regulatory role in lymphoma development. Surprisingly, despite these connections, Emu-Myc mice lacking Id2 succumb to lethal B-cell lymphoma at rates comparable with wild-type Emu-Myc transgenics. Furthermore, precancerous splenic B cells lacking Id2 do not exhibit any significant defects in Myc-induced target gene transactivation and proliferation. However, due to their lack of secondary lymph nodes, Emu-Myc mice lacking Id2 rather succumb to disseminated lymphoma with an associated leukemia, with pronounced infiltrates of the bone marrow and other major organs. Collectively these findings argue that targeting Id2 functions may be ineffective in preventing Myc-associated malignancies.
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| 13. |
- Nilsson, Jonas A, et al.
(author)
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Mnt : master regulator of the Max network.
- 2004
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In: Cell Cycle. - 1538-4101. ; 3:5, s. 588-90
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Journal article (peer-reviewed)abstract
- Recent findings indicate that we should rethink how Myc oncoproteins transactivate their target genes. It appears that Mnt, a transcription factor that mediates transrepression at Myc's E-boxes, plays a crucial role in keeping the cell cycle in check. By removing Mnt, either via conventional knockout techniques or via RNA interference, cells become hyper-proliferative, susceptible to apoptosis and can be transformed by Ras--all hallmarks of Myc overexpression. These findings indicate that Myc's ability to function as an oncogene may rely, at least in part, on its ability to effectively antagonize Mnt's transrepression and tumor suppressor functions.
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| 14. |
- Nilsson, Jonas A, et al.
(author)
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Mnt loss triggers Myc transcription targets, proliferation, apoptosis, and transformation.
- 2004
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In: Mol Cell Biol. - 0270-7306. ; 24:4, s. 1560-9
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Journal article (peer-reviewed)abstract
- Myc oncoproteins are overexpressed in most cancers and are sufficient to accelerate cell proliferation and provoke transformation. However, in normal cells Myc also triggers apoptosis. All of the effects of Myc require its function as a transcription factor that dimerizes with Max. This complex induces genes containing CACGTG E-boxes, such as Ornithine decarboxylase (Odc), which harbors two of these elements. Here we report that in quiescent cells the Odc E-boxes are occupied by Max and Mnt, a putative Myc antagonist, and that this complex is displaced by Myc-Max complexes in proliferating cells. Knockdown of Mnt expression by stable retroviral RNA interference triggers many targets typical of the "Myc" response and provokes accelerated proliferation and apoptosis. Strikingly, these effects of Mnt knockdown are even manifest in cells lacking c-myc. Moreover, Mnt knockdown is sufficient to transform primary fibroblasts in conjunction with Ras. Therefore, Mnt behaves as a tumor suppressor. These findings support a model where Mnt represses Myc target genes and Myc functions as an oncogene by relieving Mnt-mediated repression.
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