MYC favors the onset of tumorigenesis by inducing epigenetic reprogramming of mammary epithelial cells towards a stem cell-like state
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ABSTRACT:
ORGANISM(S): Homo sapiens
PROVIDER: GSE86416 | GEO | 2018/01/30
REPOSITORIES: GEO
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Project description:We address the molecular mechanisms through which MYC promotes loss of cell identity and acquisition of stem cell-like traits, favouring the onset of tumorigenesis, by performing gene expression profile analyses in a transition from WT IMEC, IMEC over-expressing MYC and mammospeheres formed from IMEC-MYC (named M2). We then investigated the global gene expression profile of the fraction of cells hyper-activating the WNT pathway in M2 spheres, compared to the ones with low activation
2018-01-30 | GSE86407 | GEO
Project description:Breast cancer consists of highly heterogeneous tumors, whose cell of origin and driver oncogenes are difficult to be uniquely defined. Here we report that MYC acts as tumor reprogramming factor in mammary epithelial cells by inducing an alternative epigenetic program, which triggers loss of cell identity and activation of oncogenic pathways. Overexpression of MYC induces transcriptional repression of lineage-specifying transcription factors, causing decommissioning of luminal-specific enhancers. MYC-driven dedifferentiation supports the onset of a stem cell-like state by inducing the activation of de novo enhancers, which drive the transcriptional activation of oncogenic pathways. Furthermore, we demonstrate that the MYC-driven epigenetic reprogramming favors the formation and maintenance of tumor-initiating cells endowed with metastatic capacity. This study supports the notion that MYC-driven tumor initiation relies on cell reprogramming, which is mediated by the activation of MYC-dependent oncogenic enhancers, thus establishing a therapeutic rational for treating basal-like breast cancers.
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Project description:We address the molecular mechanisms through which MYC promotes loss of cell identity and acquisition of stem cell-like traits, favouring the onset of tumorigenesis, by performing epigenetic profile analyses in a transition from WT IMEC, IMEC over-expressing MYC and mammospeheres formed from IMEC-MYC (named M2).
2018-01-30 | GSE86412 | GEO
Project description:MYC favors the onset of tumorigenesis by inducing epigenetic reprogramming of mammary epithelial cells towards a stem cell-like state
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Project description:Expression of the antioxidant enzyme EcSOD in normal human mammary epithelial cells was not recognized until recently. Although expression of EcSOD was not detectable in non-malignant human mammary epithelial cells (HMEC) cultured in conventional two-dimensional (2D) culture conditions, EcSOD protein expression was observed in normal human breast tissues, suggesting that the 2D-cultured condition induces a repressive status of EcSOD gene expression in HMEC. With the use of laminin-enriched extracellular matrix (lrECM), we were able to detect expression of EcSOD when HMEC formed polarized acinar structures in a 3D-culture condition. Repression of the EcSOD-gene expression was again seen when the HMEC acini were sub-cultured as a monolayer, implying that lrECM-induced acinar morphogenesis is essential in EcSOD-gene activation. We have further shown the involvement of DNA methylation in regulating EcSOD expression in HMEC under these cell culture conditions. EcSOD mRNA expression was strongly induced in the 2D-cultured HMEC after treatment with a DNA methyltransferase inhibitor. In addition, epigenetic analyses showed a decrease in the degree of CpG methylation in the EcSOD promoter in the 3D versus 2D-cultured HMEC. More importantly, >80% of clinical mammary adenocarcinoma samples showed significantly decreased EcSOD mRNA and protein expression levels compared with normal mammary tissues and there is an inverse correlation between the expression levels of EcSOD and the clinical stages of breast cancer. Combined bisulfite restriction analysis analysis of some of the tumors also revealed an association of DNA methylation with the loss of EcSOD expression in vivo. Furthermore, overexpression of EcSOD inhibited breast cancer metastasis in both the experimental lung metastasis model and the syngeneic mouse model. This study suggests that epigenetic silencing of EcSOD may contribute to mammary tumorigenesis and that restoring the extracellular superoxide scavenging activity could be an effective strategy for breast cancer treatment.
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Project description:In human breast cancer, overexpression of the protooncogene MET is strongly associated with poor prognosis and high risk of metastasis. It stands out as a reliable prognostic indicator of survival and defines a set of tumors exclusive of those that express HER2 or hormone receptors. Studies have shown that overexpression of mutant forms of MET cause cancer in mice. However, MET mutations have not been found in human breast cancer, and the consequences of overexpression of normal MET are unknown. To investigate the role of MET and other putative oncogenes in breast cancer, we developed an experimental system that involves retroviral delivery of genes into primary mammary epithelial cells, followed by transplantation of the transduced cells into mammary fat pads. Using this approach, we found that overexpression of wild-type MET leads to the development of nonprogressive neoplasms. The lesions progressed to mammary adenocarcinoma when a second protooncogene, MYC, was overexpressed, indicating that MET and MYC cooperate in mammary tumorigenesis. Both the nonprogressive neoplasms and adenocarcinomas display characteristics consistent with transformation and expansion of mammary progenitor cells. The approach described here should provide a useful model with which to efficiently test effects of various genes on tumor development in the breast.
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Project description:Mesenchymal-to-epithelial transition (MET) is an important step in cell reprogramming from fibroblasts (a cell type frequently used for this purpose) to various epithelial cell types. However, the mechanism underlying MET induction in fibroblasts remains to be understood. The present study aimed to identify the transcription factors (TFs) that efficiently induce MET in dermal fibroblasts. OVOL2 was identified as a potent inducer of key epithelial genes, and OVOL2 cooperatively enhanced MET induced by HNF1A, TP63, and KLF4, which are known reprogramming TFs to epithelial lineages. In TP63/KLF4-induced keratinocyte-like cell-state reprogramming, OVOL2 greatly facilitated the activation of epithelial and keratinocyte-specific genes. This was accompanied by enhanced changes in chromatin accessibility across the genome. Mechanistically, motif enrichment analysis revealed that the target loci of KLF4 and TP63 become accessible upon induction of TFs, whereas the OVOL2 target loci become inaccessible. This indicates that KLF4 and TP63 positively regulate keratinocyte-associated genes whereas OVOL2 suppresses fibroblast-associated genes. The exogenous expression of OVOL2 therefore disrupts fibroblast lineage identity and facilitates fibroblast cell reprogramming into epithelial lineages cooperatively with tissue-specific reprogramming factors. Identification of OVOL2 as an MET inducer and an epithelial reprogramming enhancer in fibroblasts provides new insights into cellular reprogramming improvement for future applications.
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Project description:Deregulated Myc transcriptionally reprograms cell metabolism to promote neoplasia. Here we show that oncogenic Myc requires the Myc superfamily member MondoA, a nutrient-sensing transcription factor, for tumorigenesis. Knockdown of MondoA, or its dimerization partner Mlx, blocks Myc-induced reprogramming of multiple metabolic pathways, resulting in apoptosis. Identification and knockdown of genes coregulated by Myc and MondoA have allowed us to define metabolic functions required by deregulated Myc and demonstrate a critical role for lipid biosynthesis in survival of Myc-driven cancer. Furthermore, overexpression of a subset of Myc and MondoA coregulated genes correlates with poor outcome of patients with diverse cancers. Coregulation of cancer metabolism by Myc and MondoA provides the potential for therapeutics aimed at inhibiting MondoA and its target genes.
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Project description:Previous studies have demonstrated that cyclin D1, an upstream regulator of the Rb/E2F pathway, is an essential component of the ErbB2/Ras (but not the Wnt/Myc) oncogenic pathway in the mammary epithelium. However, the role of specific E2fs for ErbB2/Ras-mediated mammary tumorigenesis remains unknown. Here, we show that in the majority of mouse and human primary mammary carcinomas with ErbB2/HER2 overexpression, E2f3a is up-regulated, raising the possibility that E2F3a is a critical effector of the ErbB2 oncogenic signaling pathway in the mammary gland. We examined the consequence of ablating individual E2fs in mice on ErbB2-triggered mammary tumorigenesis in comparison to a comparable Myc-driven mammary tumor model. We found that loss of E2f1 or E2f3 led to a significant delay in tumor onset in both oncogenic models, whereas loss of E2f2 accelerated mammary tumorigenesis driven by Myc-overexpression. Furthermore, southern blot analysis of final tumors derived from conditionally deleted E2f3(-/loxP) mammary glands revealed that there is a selection against E2f3(-/-) cells from developing mammary carcinomas, and that such selection pressure is higher in the presence of ErbB2 activation than in the presence of Myc activation. Taken together, our data suggest oncogenic activities of E2F1 and E2F3 in ErbB2- or Myc-triggered mammary tumorigenesis, and a tumor suppressor role of E2F2 in Myc-mediated mammary tumorigenesis.
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Project description:This SuperSeries is composed of the following subset Series: GSE32727: EMT inducers catalyze malignant transformation of mammary epithelial cells and drive tumorigenesis towards claudin-low tumors [human] GSE32904: EMT inducers catalyze malignant transformation of mammary epithelial cells and drive tumorigenesis towards claudin-low tumors [mouse] Refer to individual Series
| S-ECPF-GEOD-32905 | biostudies-other