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Interleukin-6 enhances transforming growth factor-alpha mRNA expression in macrophage-like human monocytoid (U-937-1) cells
Linköping University, Department of Clinical and Experimental Medicine, Cell Biology. Linköping University, Faculty of Health Sciences.
Linköping University, Department of Clinical and Experimental Medicine, Oncology . Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Oncology UHL.
Linköping University, Department of Clinical and Experimental Medicine, Cell Biology. Linköping University, Faculty of Health Sciences.
2001 (English)In: Bioscience Reports, ISSN 0144-8463 (print) 1573-4935 (online), Vol. 21, no 3, 325-339 p.Article in journal (Refereed) Published
Abstract [en]

We have previously reported that the human monocytoid cell line U-937-1 constitutively expresses transforming growth factor-alpha (TGF-α) and that the steady-state levels of TGF-α mRNA as well as TGF-α protein release increase when U-937-1 cells are differentiated towards monocytes/macrophages. Interleukin-6 (IL-6), which has been shown to have growth-stimulatory effects on a number of cell types, has recently been shown to enhance TGF-α expression in keratinocytes. In the present study we investigated whether TGF-α expression in macrophage-like cells could be regulated by IL-6 using U-937-1 cells as a model system of monocyte/macrophage differentiation.

U-937-1 cells were differentiated with retinoic acid (RA), vitamin D3 (Vit-D3) or phorbol-12-myristate-13-acetate (PMA) for 4 days and were then treated with human recombinant IL-6 (1000 IU/ml) for up to 24 hr. Northern blot analysis revealed that cells differentiated with PMA, inducing the phenotype of a secretory macrophage, markedly increased their TGF-α mRNA levels (2.7-fold) when treated with IL-6; the response was maximal at 6 hr and remained high at 12 hr. The expression of the TGF-α gene was accompanied by release of TGF-α protein into the cell culture medium, irrespective of differentiating agent, as demonstrated by enzyme-linked immunosorbent assay (ELISA), as well as by surface expression of pro-TGF-α as determined by indirect immunofluorescent cytometry. However, the superinduction of the TGF-α gene by IL-6 in cells differentiated with PMA was not accompanied by any increase in TGF-α protein release or pro-TGF-α surface expression.

We conclude that since IL-6 causes increased steady-state levels of TGF-α mRNA in macrophage-like cells, it may prime these cells for production of this growth factor. Furthermore, we have shown that the IL-6 receptor complex is functional in U-937-1 cells induced to differentiate towards a secretory macrophage by treatment with PMA.

Place, publisher, year, edition, pages
2001. Vol. 21, no 3, 325-339 p.
National Category
Medical and Health Sciences
URN: urn:nbn:se:liu:diva-12778DOI: 10.1023/A:1013238300100OAI: diva2:17031
Available from: 2007-11-22 Created: 2007-11-22 Last updated: 2009-08-18
In thesis
1. Studies of transforming growth factor alpha in normal and abnormal growth
Open this publication in new window or tab >>Studies of transforming growth factor alpha in normal and abnormal growth
2007 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Regulation of growth is of fundamental importance for development of the organism and to maintain health. The induction of cell proliferation and matrix production are influenced by several different signaling systems, most importantly by growth factors.

The human HER-family of growth factor ligands and receptors is one of the most studied and, at present, one of the most complex including 4 tyrosine kinase receptors and at least 11 different ligands cooperating in the transfer of signals. The HER-family growth responses are also influenced by other intercellular and extracellular signals, including matrix components, cytokines and hormones mediating e.g. inflammation.

HER-1 (EGFR) is one of the best known and most extensively studied growth factor receptors. TGF-alpha is possibly the most potent HER-1 ligand and influences wound healing, epidermal maintenance, gastrointestinal function, lactation, pulmonary function and more. Several studies have shown important regulatory functions for some inflammatory cytokines on TGF-alpha production in white blood cells. HER-1 is widespread in epithelial cells but also in mesenchymal cells such as fibroblasts, osteogenic and chondrogenic cells. Consequently, many tumors arising from these cell types express HER family members and often show TGF-alpha and/or HER activation. Indeed, mammary cancer development has been shown when over expressing both TGF-alpha and HER-2 in mouse mammary cells in vivo.

In recent years the first HER-1 and HER-2 inhibitors have come into clinical practice for treatment of breast cancer, lung cancer and gastrointestinal cancers, sometimes with great success. However, more knowledge is needed concerning the inflammatory regulation of HER-family expression including where and how the ligands and receptors cooperate. Therefore we were interested in studying the role of TGF-alpha in normal and abnormal growth.

First we showed that the acute inflammatory cytokine IL-6 regulates TGF-alpha expression in U-937-1 monocytoid cells. Secondly, we detected a possible long-term enhancing influence of singledose UVR on HER-1 expression in normal human melanocytes. We continued thirdly by revealing TGF-alpha production concomitant with HER-2 in normal human synovia and release of soluble TGF-alpha into the synovial fluid. Both TGF-alpha and HER-2 production were significantly increased in inflammatory joint conditions, e.g. RA. Fourthly, we demonstrated expression of TGF-alpha, HER-1 and HER-2 in synovial sarcoma cells in culture; the observed HER-2 phosphorylation was dependent on ligand induced HER-1 activation.

The presented results indicate that TGF-alpha expression can be enhanced by acute inflammatory cytokine IL-6, possibly contributing to growth stimulatory effects assigned to IL-6 itself.

The acute effects of UVR on melanocytes mediate up-regulated steady-state expression of HER-1, constituting a potential target for locally produced TGF-alpha that may induce melanocyte proliferation.

TGF-alpha and HER-2 seem to have a role in the maintenance of

synovial joint tissues. Upregulation of TGF-alpha and HER-2 in inflammatory joint conditions, e.g. RA, represents a novel mechanism for synovial proliferation contributing to joint deterioration.

TGF-alpha, HER1 and HER-2 may have a role in synovial sarcoma proliferation; further investigation is needed to evaluate HER-family inhibitors as a possible treatment alternative in this type of cancer.

Place, publisher, year, edition, pages
Institutionen för klinisk och experimentell medicin, 2007
Linköping University Medical Dissertations, ISSN 0345-0082 ; 1025
TGF-alpha, HER, EGFR, synovia, synovial sarcoma, RA, synovitis
National Category
Cell and Molecular Biology
urn:nbn:se:liu:diva-10286 (URN)978-91-85895-61-8 (ISBN)
Public defence
2007-11-23, Berzeliussalen, Ing 64, Campus US, Linköpings universitet, Linköping, 13:00 (English)
Available from: 2007-11-22 Created: 2007-11-22 Last updated: 2009-08-22

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Hallbeck, Anna-LottaWalz, Thomas M.Wasteson, Åke
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