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Transcription factor C/ EBP ‐β mediates downregulation of dipeptidyl‐peptidase III expression by interleukin‐6 in human glioblastoma cells
Author(s) -
Singh Ratnakar,
Sharma Mehar C.,
Sarkar Chitra,
Singh Manmohan,
Chauhan Shyam S.
Publication year - 2014
Publication title -
the febs journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.981
H-Index - 204
eISSN - 1742-4658
pISSN - 1742-464X
DOI - 10.1111/febs.12728
Subject(s) - chromatin immunoprecipitation , microbiology and biotechnology , ccaat enhancer binding proteins , transcription factor , downregulation and upregulation , biology , small interfering rna , sp1 transcription factor , chemistry , gene expression , cancer research , promoter , transfection , gene , biochemistry , nuclear protein
Dipeptidyl‐peptidase III ( DPP III ) is a cytosolic metallo‐aminopeptidase implicated in various physiological and pathological processes. A previous study from our laboratory indicated an elevated expression of DPP III in glioblastoma (U87 MG ) cells. In the present study we investigated the role of interleukin‐6 ( IL ‐6), a pleiotropic cytokine produced by glial tumors, in the regulation of DPP III expression. Immunohistochemistry, western blotting and quantitative RT ‐ PCR were used for quantitation of DPP III and IL ‐6 in human glioblastoma cells and tumors. Cell transfections and DPP III promoter reporter assays were performed to study the transcriptional regulation of DPP III by IL ‐6. Promoter deletion analysis, site directed mutagenesis, chromatin immunoprecipitation assays and small interfering RNA (si RNA ) technology was employed to elucidate the molecular mechanism of IL ‐6 mediated regulation of DPP III expression in glioblastoma cells. Our results for the first time demonstrate a negative correlation ( r  =   0.632, P  =   0.01) between DPP III and IL ‐6 in both human tumors and cultured glioblastoma cells. Treatment of U87 MG cells with IL ‐6 significantly decreased DPP III expression with a concomitant increase in the levels of transcription factor CCAAT /enhancer binding protein beta (C/ EBP ‐β). Deletion/mutagenesis of C/ EBP ‐β binding motif of DPP III promoter significantly increased its activity and abolished its responsiveness to IL ‐6. This effect could also be mimicked by C/ EBP ‐β si RNA . In conclusion our study for the first time demonstrates C/ EBP ‐β mediated transcriptional downregulation of DPP III by IL ‐6. Our results demonstrating a negative correlation between IL ‐6 and DPP III taken together with the previously reported prognostic significance of this cytokine in glioblastoma suggests that DPP III may prove useful as a prognostic marker.

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