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Activation of NFκB in all-trans retinoic acid induced differentiation, cell cycle arrest and p21 (CDKN1A/Waf1) expression in U-937
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Genetics and Pathology.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Genetics and Pathology.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Genetics and Pathology.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Genetics and Pathology.
(English)Article in journal (Refereed) Submitted
National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:uu:diva-97438OAI: oai:DiVA.org:uu-97438DiVA: diva2:172390
Available from: 2008-08-29 Created: 2008-08-29 Last updated: 2013-09-04Bibliographically approved
In thesis
1. Epigenetic Regulation of Gene Transcription in Hematopoietic Tumors
Open this publication in new window or tab >>Epigenetic Regulation of Gene Transcription in Hematopoietic Tumors
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Epigenetic modifications were shown to play an essential role in tumorigenesis. Epigenetic mechanisms can alter transcription in several ways, through DNA methylation and/or through histone modification. DNA methylation at the TSS (transcriptional start site) has been implicated in tumor development and gene silencing. However, several examples of atypical methylation were shown. In Paper I we present the ICSBP/IRF8 gene that belongs to the IRF family and has characteristics of a tumor suppressor gene. The ICSBP/IRF8 is fully methylated in the promoter and TSS regions in U-937 and despite high expression of the gene. Presence of positive histone marks suggests that methylated DNA can be overridden by histone modification.

In Paper II a panel of 13 MM (multiple myeloma) cell lines and 9 primary patient tumors were analysed for methylation status of the ICSBP/IRF8 gene. In most cell lines (8/13) the gene was partially or fully methylated and partial methylation was also observed in 1/9 primary tumors. In vitro methylation analysis and treatment with 5-aza-2’deoxycytidine (DAC) proved that the ICSBP/IRF8 gene is silenced by methylation and may be associated with the malignant phenotype.

In Paper III and IV the NFκB signalling pathway was analysed and the role of ATRA and TNFα induction. In Paper III the data shows that activation of the NFκB pathway is essential in ATRA-induced terminal differentiation in the U-937 cell line and IκBα (S32A/S36A) inhibits ATRA-induced differentiation and G1 cell cycle arrest. This was accompanied by delayed down-regulation of several cyclins (A and E) and up-regulation of p21WAF1/CIP1 (CDKN1A) and p27KIP1 (CDKN1B).

TNFα alone did not induce expression of RA-induced genes analysed in Paper IV. However, ATRA in combination with TNFα showed enhanced activation of RA-induced genes. TNFα triggers demethylation of H3K9me3/H3K9me2 and H3K4me3 at RAR/RXR target genes, which were not accompanied by changes in the level of H3K9-ac. This decrease in H3 methylation by TNFα may pave way for the later ATRA-induced gene transcription.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2008. 53 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 1651-6206 ; 368
Keyword
Medical sciences, IRF family, ICSBP/IRF8, epigenetics, ATRA, TNFα, histone modifications, methylation, transcription, MEDICIN OCH VÅRD
Identifiers
urn:nbn:se:uu:diva-9206 (URN)978-91-554-7257-3 (ISBN)
Public defence
2008-09-19, Rudbeck Hall, Rudbeck Laboratory, Dag Hammarskjölds väg. 20 Uppsala, 13:15
Opponent
Supervisors
Available from: 2008-08-29 Created: 2008-08-29Bibliographically approved
2. Signal Transduction in Malignant Cells – Transformation, Activation and Differentiation
Open this publication in new window or tab >>Signal Transduction in Malignant Cells – Transformation, Activation and Differentiation
2006 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

All aspects of cell life are regulated by signal transduction mechanisms. This thesis describes the regulatory roles of a few key signal transduction molecules involved in three major biological responses. The studied pathways include platelet derived growth factor (PDGF)-BB induced transformation of murine fibroblasts, interferon (IFN)-γ stimulated monocyte activation and all-trans retinoic acid (ATRA) induced myeloid differentiation.

We found that intact phosphoinositide 3OH-kinase (PI3K) activity is essential in the signaling pathway that leads to the morphological alterations and migration pattern characteristic of PDGF-BB transformed NIH/sis and NIH/COL1A1 fibroblasts. Furthermore, our data indicated that the small Rho-GTPase, Rac1 is the predominant mediator of these signals downstream of PI3K.

The study of the IFN-γ induced activation of monocytic U-937 cells showed that upregulation of the high affinity receptor for IgG (FcγRI) is dependent on the coordination of several regulatory events: the PKR-mediated serine 727 phosphorylation of Stat1, the expression of the hematopoietic lineage specific transcription factor PU.I, and the activation of the NFκB pathway.

ATRA-induced differentiation and cell cycle arrest are impaired in U-937 sublines expressing phosphorylation deficient Stat1 (Stat1Y701F and Stat1S727A). The findings in paper III indicated that the expression pattern of the myeloid specific transcription factors Stat2, ICSBP and c/EBPε was altered in the sublines and that intact Stat1 activation is critical for maintaining the balance of the transcriptional network during ATRA induced terminal differentiation.

Finally, ATRA-induced differentiation and growth arrest were blocked by treatment with the IKKα/β inhibitor BMS345541 or by ectopic expression of the NFκB super repressor IκBα (S32A/S36A). The fact that IκB(AA) sublines differentiated normally in response to vitamin D3, showed that NFκB inhibition specifically affected ATRA induced responses. Notably we suggest that the activity of the NFκB pathway may interfere with the differentiation process via a direct effect on the RAR/RXR mediated transcription.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2006. 49 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 1651-6206 ; 107
Keyword
Molecular medicine, transformation, PDGF, PI3K, Rho-GTPase, U-937, FcγRI, macrophage, Stat1, PKR, NFκB, ATRA, differentiation, Molekylärmedicin
National Category
Medical Genetics
Research subject
Pathology
Identifiers
urn:nbn:se:uu:diva-6346 (URN)91-554-6465-3 (ISBN)
Public defence
2006-03-10, Rudbecksalen, Rudbecklaboratoriet, Dag Hammarsköldsväg 20, Uppsala, 09:15
Opponent
Supervisors
Available from: 2006-02-10 Created: 2006-02-10 Last updated: 2013-09-04Bibliographically approved

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