Co-operative functions between nuclear factors NFkappaB and CCAT/enhancer-binding protein-beta (C/EBP-beta) regulate the IL-6 promoter in autocrine human prostate cancer cells.
BACKGROUND
IL-6 is a growth and survival factor for prostate cancer cells through autocrine pathways. Here, we have systematically examined the transcriptional regulation mechanisms of IL-6 in autocrine prostate cancer cells.


METHODS
RT-PCR and immunohistochemical staining were used to determine IL-6 production in the cells. Serial mutant IL-6 promoter luciferase reporters were generated and their transcriptional activities were examined. The transcription factors involved in IL-6 regulation were identified with super-shift EMSA. Overexpression of NFkappaB p65 and C/EBP-beta, and blockade of NFkappaB with IkappaBalpha or CAPE were performed to demonstrate the cooperation between NFkappaB p65 and C/EBP-beta in activation of IL-6.


RESULTS
Transcription factor regulatory sites IL6-NFkappaB, IL6-C/EBP, IL6-CREB, and IL6-AP1, are responsive to constitutively activated IL-6 production in autocrine prostate cancer cell lines. Among these sites, IL6-AP1 and IL6-C/EBP appear most important, while IL6-NFkappaB shows the least effect for IL-6 promoter activity as determined by mutant IL-6 promoter luciferase reporter assay. Nevertheless, nuclear factor NFkappaB is activated and required. Such activation is minimally dependent upon the IL6-NFkappaB site, occurring through cooperation with other transcription factors that bind the IL-6 promoter. Cooperation between NFkappaB p65 and C/EBP-beta did not require a functional IL6-NFkappaB binding site.


CONCLUSIONS
These data support a unique role for NFkappaB p65 as the primary trigger in autocrine production of IL-6 in prostate cancer cells. Furthermore, we describe a novel transcriptional activation mechanism for NFkappaB that is independent of its regulatory binding site, occurring through cooperation with other transcription factors that facilitate the neighboring regulatory site.
Xiao
Weihua
W
Basic Research Program, SAIC Frederick, Laboratory of Molecular Immunoregulation, NCI-Frederick Cancer Research and Development Center; National Institute of Health, Frederick, Maryland 21702, USA.
Hodge
David R
DR
Wang
Lihua
L
Yang
Xiaoyi
X
Zhang
Xiaohu
X
Farrar
William L
WL
D001483:Base Sequence; D001665:Binding Sites; D015153:Blotting, Western; D022782:CCAAT-Enhancer-Binding Protein-beta / Q000235:genetics / Q000502:physiology*; D002109:Caffeic Acids / Q000494:pharmacology; D004247:DNA / Q000737:chemistry / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D020672:I-kappa B Proteins / Q000494:pharmacology; D007150:Immunohistochemistry; D015850:Interleukin-6 / Q000096:biosynthesis / Q000235:genetics*; D008297:Male; D008969:Molecular Sequence Data; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D010626:Phenylethyl Alcohol / Q000031:analogs & derivatives* / Q000494:pharmacology; D011401:Promoter Regions, Genetic / Q000235:genetics*; D011471:Prostatic Neoplasms / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014157:Transcription Factors; D014158:Transcription, Genetic / Q000187:drug effects; D014162:Transfection; D014407:Tumor Cells, Cultured
D022782:CCAAT-Enhancer-Binding Protein-beta; D002109:Caffeic Acids; D020672:I-kappa B Proteins; D015850:Interleukin-6; D016328:NF-kappa B; C000606204:NFKBIA protein, human; D014157:Transcription Factors; D000072000:NF-KappaB Inhibitor alpha; D004247:DNA; C055494:caffeic acid phenethyl ester; D010626:Phenylethyl Alcohol