676 research outputs found
Association of depression and pain interference with disease-management self-efficacy in community-dwelling individuals with spinal cord injury
No full textThe AURKA/TPX2 axis drives colon tumorigenesis cooperatively with MYC
No full textWe identified TPX2 and AURAKA as novel co-regulators on the MYC pathway and proposed a new model of MYC-driven cancer. Co-amplification between 8q24 and 20q leads to co-overexpression of MYC and AURKA/TPX2, which cooperatively induce MYC downstream target genes. Based on this model, inhibiting the AURKA/TPX2 axis would be a novel synthetic lethal therapeutic approach for MYC-driven cancers.
Background
The MYC oncogene has long been established as a central driver in many types of human cancers including colorectal cancer. However, the realization of MYC-targeting therapies remains elusive; as a result, synthetic lethal therapeutic approaches are alternatively being explored. A synthetic lethal therapeutic approach aims to kill MYC-driven tumors by targeting a certain co-regulator on the MYC pathway.
Patients and methods
We analyzed copy number and expression profiles from 130 colorectal cancer tumors together with publicly available datasets to identify co-regulators on the MYC pathway. Candidates were functionally tested by in vitro assays using colorectal cancer and normal fibroblast cell lines. Additionally, survival analyses were carried out on another 159 colorectal cancer patients and public datasets.
Results
Our in silico screening identified two MYC co-regulator candidates, AURKA and TPX2, which are interacting mitotic regulators located on chromosome 20q. We found the two candidates showed frequent co-amplification with the MYC locus while expression levels of MYC and the two genes were positively correlated with those of MYC downstream target genes across multiple cancer types. In vitro, the aberrant expression of MYC AURKA and TPX2 resulted in more aggressive anchorage-independent growth in normal fibroblast cells. Furthermore, knockdown of AURKA or TPX2, or treatment with an AURKA-specific inhibitor effectively suppressed the proliferation of MYC-expressing colorectal cancer cells. Additionally, combined high expression of MYC AURKA and TPX2 proved to be a poor prognostic indicator of colorectal cancer patient survival.
Conclusions
Through bioinformatic analyses and experiments, we proposed TPX2 and AURKA as novel co-regulators on the MYC pathway. Inhibiting the AURKA/TPX2 axis would be a novel synthetic lethal therapeutic approach for MYC-driven cancers.CRESTJapan Science and Technology AgencyNext Generation World-Leading ResearchersJapan Society for the Promotion of ScienceGrant-in-Aid for Scientific ResearchGrants-in-Aid for Scientific Research on Innovative Areas of MEXT ‘Systems Cancer Research’MEXT Strategic Programs on Innovative Research ‘Supercomputational Life Science’Osaka Cancer Societ
Structure and expression of B-myc, a new member of the myc gene family
No full textThe myc family of genes contains five functional members. We describe the cloning of a new member of the myc family from rat genomic and cDNA librariers, designated B-myc. A fragment of cloned B-myc was used to map the corresponding rat locus by Southern blotting of DNA prepared from rat x mouse somatic cell hybrids. B-myc mapped to rat chromosome 3. We have previously mapped the c-myc to rat chromosome 7 and N-myc and L-myc to rat chromosomes 6 and 5, respectively. A partial sequence of B-myc had extensive sequence homology to the c-myc protein-coding region, and the detection of intron homology further indicated that these two genes are closely related. The DNA regions conserved among the myc family members, designated myc boxes, were highly conserved between c-myc and B-myc. A lower degree of homology was detected in other parts of the coding region in c-myc and B-myc not present in N-myc and L-myc. A 1.3 -kilobase B-myc-specific mRNA was detected in most rat tissues, with the highest expression in the brain. This resembled the expression pattern of c-myc, although at different relative levels, and was in contrast to the more tissue-specific expression of N-myc and L-myc. B-myc was expressed at uniformly high levels in all fetal tissues and during subsequent postnatal development, in contrast to the stage-specific expression of c-myc
PIAS1 Promotes Lymphomagenesis through MYC Upregulation
No full textSummaryThe MYC proto-oncogene is a transcription factor implicated in a broad range of cancers. MYC is regulated by several post-translational modifications including SUMOylation, but the functional impact of this post-translational modification is still unclear. Here, we report that the SUMO E3 ligase PIAS1 SUMOylates MYC. We demonstrate that PIAS1 promotes, in a SUMOylation-dependent manner, MYC phosphorylation at serine 62 and dephosphorylation at threonine 58. These events reduce the MYC turnover, leading to increased transcriptional activity. Furthermore, we find that MYC is SUMOylated in primary B cell lymphomas and that PIAS1 is required for the viability of MYC-dependent B cell lymphoma cells as well as several cancer cell lines of epithelial origin. Finally, Pias1-null mice display endothelial defects reminiscent of Myc-null mice. Taken together, these results indicate that PIAS1 is a positive regulator of MYC
Microcystin-LR stabilizes c-myc protein by inhibiting protein phosphatase 2A in HEK293 cells
No full textMicrocystin-LR is the most toxic and the most frequently encountered toxin produced by the cyanobacteria in the contaminated aquatic environment. Previous studies have demonstrated that Microcystin-LR is a potential carcinogen for animals and humans, and the International Agency for Research on Cancer has classified Microcystin-LR as a possible human carcinogen. However, the precise molecular mechanisms of Microcystin-LR-induced carcinogenesis remain a mystery. C-myc is a proto-oncogene, abnormal expression of which contributes to the tumor development. Although several studies have demonstrated that Microcystin-LR could induce c-myc expression at the transcriptional level, the exact connection between Microcystin-LR toxicity and c-myc response remains unclear. In this study, we showed that the c-myc protein increased in HEK293 cells after exposure to Microcystin-LR. Coexpression of protein phosphatase 2A and two stable c-myc protein point mutants (either c-myc(T58A) or c-myc(562A)) showed that Microcystin-LR increased c-myc protein level mainly through inhibiting protein phosphatase 2A activity which altered the phosphorylation status of serine 62 on c-myc. In addition, we also showed that Microcystin-LR could increase c-myc promoter activity as revealed by luciferase reporter assay. And the TATA box for P1 promoter of c-myc might be involved. Our results suggested that Microcystin-LR can stimulate c-myc transcription and stabilize c-myc protein, which might contribute to hepatic tumorigenesis in animals and humans. (C) 2014 Elsevier Ireland Ltd. All rights reserved.Microcystin-LR is the most toxic and the most frequently encountered toxin produced by the cyanobacteria in the contaminated aquatic environment. Previous studies have demonstrated that Microcystin-LR is a potential carcinogen for animals and humans, and the International Agency for Research on Cancer has classified Microcystin-LR as a possible human carcinogen. However, the precise molecular mechanisms of Microcystin-LR-induced carcinogenesis remain a mystery. C-myc is a proto-oncogene, abnormal expression of which contributes to the tumor development. Although several studies have demonstrated that Microcystin-LR could induce c-myc expression at the transcriptional level, the exact connection between Microcystin-LR toxicity and c-myc response remains unclear. In this study, we showed that the c-myc protein increased in HEK293 cells after exposure to Microcystin-LR. Coexpression of protein phosphatase 2A and two stable c-myc protein point mutants (either c-myc(T58A) or c-myc(562A)) showed that Microcystin-LR increased c-myc protein level mainly through inhibiting protein phosphatase 2A activity which altered the phosphorylation status of serine 62 on c-myc. In addition, we also showed that Microcystin-LR could increase c-myc promoter activity as revealed by luciferase reporter assay. And the TATA box for P1 promoter of c-myc might be involved. Our results suggested that Microcystin-LR can stimulate c-myc transcription and stabilize c-myc protein, which might contribute to hepatic tumorigenesis in animals and humans. (C) 2014 Elsevier Ireland Ltd. All rights reserved
Author Correction: IRE1α-XBP1s pathway promotes prostate cancer by activating c-MYC signaling
No full textSheng X, Nenseth HZ, Qu S, et al. Author Correction: IRE1alpha-XBP1s pathway promotes prostate cancer by activating c-MYC signaling. Nature Communications . 2024;15(1): 6190
Functional analysis of N-MYC downstream regulated gene 1 (NDRG1) in Oesophageal squamous cell carcinoma
No full textOesophageal squamous cell carcinoma (OSCC) ranks as one of the deadliest tumours with a high incidence in developing countries in the areas of Southern Africa, Middle East and Far East. Moreover, its unfavourable prognosis is further complicated by the lack of knowledge about the molecular biology of this disease. In this thesis, we describe our work analysing the function of N-myc downstream regulated gene 1 (NDRG1, also known as Cap43 or Drg-1) in the neoplastic progression and maintenance of OSCC. Although NDRG1 has previously been implicated in breast, prostate, colon and liver carcinoma, the exact role of NDRG1 in OSCC still remains unclear. According to the immunohistochemical analysis of clinical OSCC tissue samples (n=52), NDRG1 expression was gradually increased in tumour tissue versus normal, indicating the potential involvement of NDRG1 in the neoplastic progression of OSCC. We next performed ectopic NDRG1 gain-of-function and loss-of-function studies using transfectants established from transduced OSCC cell lines (KYSE30 and KYSE150) by lentiviral vector mediated gene delivery. In KYSE30 cells, although no substantial effects on in vitro cell proliferation and differentiation were observed with altered NDRG1 expression, the ectopic overexpression of NDRG1 was found to be positively linked to metastasis, angiogenesis and apoptotic evasion as measured in cell culture. Accordingly, in the nude mouse xenograft model system, NDRG1 overexpression promoted the in vivo growth and metastasis of KYSE30 derived xenografts, which could be attributed to the reduced apoptotic and enhanced angiogenic activities promoted by this gene. Nevertheless, no significant phenotypic changes were observed in response to NDRG1 knock-down, suggesting that this gene was not essential for the neoplastic progression of OSCC. Moreover, null effect of either ectopic NDRG1 overexpression or knock-down were observed in KYSE150 cells, indicating ix that the function of NDRG1 may be largely dependent on the cellular context (Chapter 2). In addition to direct functional assays, evidence from analysing the regulation pattern of NDRG1 in OSCC cells was also presented to provide clues to indirectly predict the function of NDRG1 in OSCC. In Chapter 3, we demonstrated that NDRG1 could be actively regulated by various oncogenic stimuli such as cellular stress (genotoxicity and hypoxia) and mitogenic factors (EGF and IGF). Although these oncogenic regulatory effects on NDRG1 expression in OSCC cells may be dichotomous, the functional significance of NDRG1 upregulation, especially by hypoxia and EGF signalling, is highlighted. In our studies, the regulatory pattern of NDRG1 in OSCC is highly consistent with its oncogenic function revealed in ectopic studies (Chapter 2), further suggesting that phenotypic changes observed in the functional studies may not be artifactual, but may reflect the role of NDRG1 in the neoplastic progression of OSCC in physiological conditions. Taken together, our current data implicate NDRG1 as an effective but non-essential promoter in the neoplastic progression of oesophageal squamous cell carcinoma. Although the mechanism still needed to be further explored, our study suggests important clues regarding these mechanistic roles considering the impact of this gene on apoptosis, metastasis and angiogenesis
Expression and regulation of N-Myc Downstream- Regulated gene 1 in squamous cell carcinoma of the oesphagus
No full textSquamous cell carcinoma of the oesophagus is a formidable disease which poses a significant health risk in developing countries where the incidence is frequently high and access to health care facilities is often limited. The identification of genes involved in oesophageal tumourigenesis may provide new targets for therapy and improved diagnostics techniques, thereby improving the prognosis of this pernicious disease. In this study, real-time RT-PCR and immunohistochemistry described the overexpression of N-Myc Downstream-Regulated Gene 1 (NDRG1) in oesophageal squamous cell carcinoma (OSCC) tissue compared to normal tissue in a cohort of South African cancer patients. Despite more than ten years of research into the role of NDRG1 in cancer, the precise function of this protein remains enigmatic. Reports have been contentious, suggesting both tumour suppressor and tumour promoter functions for NDRG1, implicating it in tumourigenic processes such as metastasis and angiogenesis. Our immunohistochemical analysis if NDRG1 expression in OSCC tissue and matched normal epithelium (n=83) showed that NDRG1 expression is elevated by 2.6-fold in cancer tissue compared to normal tissue. Moreover, the expression and localisation of NDRG1 appeared to track with epithelial cell maturation where basal cells of normal oesophageal epithelium displayed plasma membrane-associated NDRG1 while maturing cells were mostly positive for NDRG1 in the cytoplasm and nucleus. Likewise, NDRG1 displayed interesting patterns of localisation in tumour tissue of the xiii oesophagus. Dysplastic tissue and poorly differentiated tumour tissue stained positively for NDRG1 in the plasma membrane, while moderately and well differentiated tumours displayed mixed staining for NDRG1 in the plasma membrane, cytoplasm and nucleus. Analysis of NDRG1 expression in cell lines cultured under anchorage-independent conditions revealed that NDRG1 expression is strongly induced when cells are prevented from adhering to the surface of culture dishes. Induced NDRG1 expression correlated inversely with mRNA expression of invasion genes, MMP-2 and MMP-9, as well as the mRNA expression of angiogenic factors Ang- 1, PDGF-B and VEGF-C but, in contrast, showed positive correlation with the angiogenesis cytokine, VEGF-A. Knock-down of NDRG1 expression with siRNA had no effect on anchorage-independent cell proliferation or apoptosis but did inhibit VEGF-A expression. Moreover, VEGF-A promoter activity, induced by culturing cells under anchorage-independent conditions was shown to be NDRG1-dependent. In order to identify factors that may drive NDRG1 transcription in cultured OSCC cell lines we cloned and partly characterised the NDRG1 promoter. Through the generation of promoter deletion constructs, site-directed mutagenesis and Chromatin Immunoprecipitation (ChIP) assays, we showed that both EGR-1 and cJun/AP-1 are capable of driving transcription of NDRG1 in response to 12-o-tetradecanoylphorbol- 13-acetate (TPA) through activation of PKC/MEK/ERK1/2 and JNK MAPK pathways. Taken together, we describe the regulation of NDRG1 expression by EGR-1 and AP-1 and we show that NDRG1 is overexpressed in squamous cell carcinoma of the oesophagus compared to normal oesophageal tissue. We associate NDRG1 with an xiv oncogenic function in OSCC through its potential role in angiogenesis via modulation of VEGF-A expression
Selective targeting of MYC by antisense oligonucleotides
Get PDFThesis: Ph. D. in Biomedical Engineering, Harvard-MIT Program in Health Sciences and Technology, 2018.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student-submitted PDF version of thesis.Includes bibliographical references (pages 181-208).MYC is one of the most commonly dysregulated genes across all cancers. As a master transcription factor with greater than 10,000 binding sites throughout the genome, the MYC oncoprotein coordinates a transcriptional regulatory network consisting of approximately 15% of all genes, controlling cancer hallmark expression programs responsible for cellular proliferation, growth, metabolism, and evasion from apoptosis. MYC dysregulation occurs genetically, epigenetically, and post-transcriptionally through a wide variety of mechanisms. Despite its well-characterized properties as a proto-oncogene, direct potent and selective inhibition of MYC remains a significant challenge. Models of systemic MYC inhibition utilizing inducible genetic constructs in mice have revealed that inhibition of MYC activity leads to potent tumor regression with an evident therapeutic window, suggesting that pharmacologic MYC inhibition may be a viable cancer therapeutic strategy. Small molecule inhibitors designed to block MYC protein activity exhibit low potency, display poor selectivity, and lack antitumor efficacy, which has led MYC to be historically classified as 'undruggable.' Efforts aimed at indirectly targeting MYC transcription often lead to development of resistance characterized by reinforced expression of MYC. Clearly, alternate strategies are needed to achieve selective and potent inhibition of MYC. The goals of this research were to develop antisense oligonucleotides specifically targeted against the MYC mRNA to achieve potent inhibition of MYC translation, and to characterize the activity of these molecules as specific modulators of MYC expression and as prototypical MYC-directed therapeutics. We designed and synthesized a library of MYC-targeting antisense oligonucleotides (MYCASOs) containing several chemical synthetic features to increase target affinity and stability. Treatment of MYC-expressing cancer cells with MYCASOs leads to RNase H-mediated cleavage of MYC mRNA and a potent decrease in MYC protein levels. MYC knockdown is accompanied by significant effects on cellular viability and inhibition of cellular proliferation. Furthermore, MYCASO treatment specifically perturbs MYC-driven gene expression signatures. In a MYC-induced murine model of hepatocellular carcinoma, MYCASO treatment leads to cleavage of the MYC transcript, decreased MYC protein levels within tumors, and reduced tumor burden. MYCASOs represent a new chemical tool for in vitro and in vivo modulation of MYC activity, and promising therapeutic agents for MYC-addicted tumors.by Taylor Elizabeth Gill.Ph. D. in Biomedical Engineerin
FBXO32 Targets c-Myc for Proteasomal Degradation and Inhibits c-Myc Activity
No full textBackground: FBXO32 is an E3 ubiquitin ligase that plays important roles in tumorigenesis and muscle atrophy. Results: c-Myc was found to be a target of FBXO32 for proteasomal degradation. Conclusion: FBXO32 targets Lys-326 of c-Myc to form polyubiquitin chains, resulting in inhibition of cell proliferation. Significance: FBXO32 may mediate c-Myc proteasomal degradation
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