title: Interplay of nuclear factor-kappaB and B-myb in the negative regulation of androgen receptor expression by tumor necrosis factor alpha.
abstract: Increased androgen receptor (AR) levels are associated with prostate cancer progression to androgen independence and therapy resistance. Evidence has suggested that chronic inflammation is closely linked to various cancers including prostate cancer. Herein we show that the proinflammatory cytokine TNFalpha negatively regulates AR mRNA and protein expression and reduces androgen sensitivity in androgen-dependent LNCaP human prostate cancer cells. Decreased AR expression results from transcription repression involving essential in cis interaction of nuclear factor-kappaB (NF-kappaB) with the B-myb transcription factor at a composite genomic element in the 5'-untranslated region of AR. The negative regulation was abrogated when NF-kappaB activity was inhibited by a superrepressor of the inhibitory kappaB protein. In contrast, androgen-independent C4-2 (LNCaP-derived) cells fail to show AR down-regulation by TNFalpha, despite expression of B-myb and TNFalpha-induced NF-kappaB activity similar to that in LNCaP cells. The negatively regulated AR gene chromatin region showed TNFalpha-dependent enrichment of B-myb and the NF-kappaB proteins p65 and p50. In parallel, the histone deacetylase 1, corepressor silencing mediator of retinoid and thyroid hormone receptor and the corepressor-associated scaffold protein mSin3A were recruited to the inhibitory site. In C4-2 cells, neither NF-kappaB and B-myb, nor any of the corepressor components, were detected at the negative site in response to TNFalpha. Apoptosis was induced in TNFalpha-treated LNCaP cells, likely in part due to the down-regulation of AR. The androgen-independent, AR-expressing C4-2 and C4-2B (derived from C4-2) cells were resistant to TNFalpha-induced apoptosis. The results linking androgen dependence to the NF-kappaB and AR pathways may be insightful in identifying novel treatment targets for prostate cancer.
authors.affiliation: Department of Molecular Medicine/Institute of Biotechnology, The University of Texas Health Science Center at San Antonio, 15355 Lambda Drive, San Antonio, TX 78245, USA.
authors.forename: Soyoung
authors.initials: S
authors.lastname: Ko
authors.forename: Liheng
authors.initials: L
authors.lastname: Shi
authors.forename: Soyoung
authors.initials: S
authors.lastname: Kim
authors.forename: Chung S
authors.initials: CS
authors.lastname: Song
authors.forename: Bandana
authors.initials: B
authors.lastname: Chatterjee
mesh_terms: D000256:Adenoviridae / Q000235:genetics; D000728:Androgens / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D047369:Chromatin Immunoprecipitation; D024202:Electrophoretic Mobility Shift Assay; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D020287:In Situ Nick-End Labeling; D008297:Male; D008954:Models, Biological; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism*; D011401:Promoter Regions, Genetic / Q000235:genetics; D011471:Prostatic Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D034741:RNA, Small Interfering / Q000235:genetics; D011944:Receptors, Androgen / Q000235:genetics*; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D020218:Response Elements / Q000235:genetics; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
chemical_list: D000728:Androgens; D018797:Cell Cycle Proteins; C064352:MYBL2 protein, human; D016328:NF-kappa B; D034741:RNA, Small Interfering; D011944:Receptors, Androgen; D011994:Recombinant Proteins; D015534:Trans-Activators; D014409:Tumor Necrosis Factor-alpha