| 1. |
- Höglund, Andreas, 1980-, et al.
(författare)
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Chk2 deficiency in Myc overexpressing lymphoma cells elicits a synergistic lethal response in combination with PARP inhibition.
- 2011
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Ingår i: Cell Cycle. - Georgetown, TX : Landes Bioscience. - 1538-4101 .- 1551-4005. ; 10:20, s. 3598-3607
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Tidskriftsartikel (refereegranskat)abstract
- Myc is a transcription factor frequently found deregulated in human cancer. The Myc- mediated cellular transformation process is associated with fast proliferative cells and inherent genomic instability, giving rise to malignant, invasive neoplasms with poor prognosis for survival. Transcription-independent functions of Myc include stimulation of replication. Excessive Myc expression stimulates a replication-associated DNA damage response that signal via the phosphoinositide 3-kinase (PI3K) related protein kinases (PIKKs) ATM and ATR. These in turn activate the DNA damage transducers Chk1 and Chk2. Here, we show that Myc can stimulate Chek2 transcript indirectly in vitro, as well as in B cells of !-Myc transgenic mice or in the intestine of ApcMin mice. However, Chk2 is dispensable for Myc’s ability to transform cells in vitro and for the survival of established lymphoma cells from !-Myc transgenic mice. Chk2 deficiency induces polyploidy and slow growth but the cells are viable and protected against DNA damage. However, inhibition of both Chk1/Chk2 with AZD7762 induces cell death and significantly delays disease progression of transplanted lymphoma cells in vivo. DNA damage recruits PARP family members to sites of DNA breaks that in turn facilitate the induction of DNA repair. Strikingly, combining Chk2 and PARP inhibition elicits a synergistic lethal response in the context of Myc overexpression. Our data indicates that only certain types of chemotherapy would give rise to a synergistic lethal response in combination with specific Chk2 inhibitors, which will be important if Chk2 inhibitors enter the clinic.
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| 2. |
- Nilsson, Lisa M, 1976, et al.
(författare)
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Mouse genetics suggests cell-context dependency for Myc-regulated metabolic enzymes during tumorigenesis.
- 2012
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Ingår i: PLoS genetics. - : Public Library of Science (PLoS). - 1553-7404 .- 1553-7390. ; 8:3
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Tidskriftsartikel (refereegranskat)abstract
- c-Myc (hereafter called Myc) belongs to a family of transcription factors that regulates cell growth, cell proliferation, and differentiation. Myc initiates the transcription of a large cast of genes involved in cell growth by stimulating metabolism and protein synthesis. Some of these, like those involved in glycolysis, may be part of the Warburg effect, which is defined as increased glucose uptake and lactate production in the presence of adequate oxygen supply. In this study, we have taken a mouse-genetics approach to challenge the role of select Myc-regulated metabolic enzymes in tumorigenesis in vivo. By breeding λ-Myc transgenic mice, Apc(Min) mice, and p53 knockout mice with mouse models carrying inactivating alleles of Lactate dehydrogenase A (Ldha), 3-Phosphoglycerate dehydrogenase (Phgdh) and Serine hydroxymethyltransferase 1 (Shmt1), we obtained offspring that were monitored for tumor development. Very surprisingly, we found that these genes are dispensable for tumorigenesis in these genetic settings. However, experiments in fibroblasts and colon carcinoma cells expressing oncogenic Ras show that these cells are sensitive to Ldha knockdown. Our genetic models reveal cell context dependency and a remarkable ability of tumor cells to adapt to alterations in critical metabolic pathways. Thus, to achieve clinical success, it will be of importance to correctly stratify patients and to find synthetic lethal combinations of inhibitors targeting metabolic enzymes.
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| 3. |
- Plym Forshell, Tacha Zi, 1977-, et al.
(författare)
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Chemoprevention of B-cell lymphomas by inhibition of the Myc target spermidine synthase
- 2010
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Ingår i: Cancer Prevention Research. - Philadelphia, PA : American Association for Cancer Research. - 1940-6207 .- 1940-6215. ; 3:2, s. 140-147
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Tidskriftsartikel (refereegranskat)abstract
- The oncogenic transcription factor c-Myc (Myc) is frequently overexpressed in human cancers. Myc is known to induce or repress a large set of genes involved in cell growth and proliferation, explaining the selection for mutations in cancer that deregulate Myc expression. Inhibition of ornithine decarboxylase, an enzyme of the polyamine biosynthetic pathway and a Myc target, has been shown to be chemopreventive. In the present study, we have dissected the role of another enzyme in the polyamine biosynthetic pathway, spermidine synthase (Srm), in Myc-induced cancer. We find that Srm is encoded by a Myc target gene containing perfect E-boxes and that it is induced by Myc in a direct manner. RNA interference against Srm shows that it is important for Myc-induced proliferation of mouse fibroblasts but to a lesser extent for transformation. Using the compound trans-4-methylcyclohexylamine, we show that Srm inhibition can delay the onset of B-cell lymphoma development in λ-Myc transgenic mice. We therefore suggest that inhibition of Srm is an additional chemopreventive strategy that warrants further consideration.
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