Interplay of Nuclear Factor-κB and B-myb in the Negative Regulation of Androgen Receptor Expression by Tumor Necrosis Factor α

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 TNFα 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-κB (NF-κB) 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-κB activity was inhibited by a superrepressor of the inhibitory κB protein. In contrast, androgen-independent C4-2 (LNCaP-derived) cells fail to show AR down-regulation by TNFα, despite expression of B-myb and TNFα-induced NF-κB activity similar to that in LNCaP cells. The negatively regulated AR gene chromatin region showed TNFα-dependent enrichment of B-myb and the NF-κB 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-κB and B-myb, nor any of the corepressor components, were detected at the negative site in response to TNFα. Apoptosis was induced in TNFα-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 TNFα-induced apoptosis. The results linking androgen dependence to the NF-κB and AR pathways may be insightful in identifying novel treatment targets for prostate cancer.

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Role of Testosterone Levels on the Combinatorial Effect of Boswellia serrata Extract and Enzalutamide on Androgen Dependent LNCaP Cells and in Patient Derived Cells

Integrative Cancer Therapies ◽

10.1177/1534735421996824 ◽

2021 ◽

Vol 20 ◽

pp. 153473542199682

Author(s):

Prathesha Pillai ◽

Ginil Kumar Pooleri ◽

Shantikumar V. Nair

Keyword(s):

Prostate Cancer ◽

Androgen Receptor ◽

Early Stage ◽

Therapeutic Option ◽

Specific Antigen ◽

Cell Killing ◽

Receptor Expression ◽

Lncap Cells ◽

Boswellia Serrata ◽

Physiological Serum

Co-therapy with herbal extracts along with current clinical drugs is being increasingly recognized as a useful complementary treatment for cancer. The anti-cancer property of the phyto-derivative acetyl-11 keto β boswellic acid (AKBA) has been studied in many cancers, including prostate cancer. However, the whole extract of the gum resin Boswellia serrata (BS) and anti-androgen enzalutamide has not been explored in prostate cancer to date. We hypothesized that the BS extract containing 30% (AKBA) with enzalutamide acted synergistically in the early phase of cancer, especially in LNCaP cells, by inhibiting androgen receptor (AR) and by reducing cell proliferation, and further, that the extract would be superior to the action of the active ingredient AKBA when used alone or in combination with enzalutamide. To test our hypothesis, we treated LNCaP cells with BS extract or AKBA and enzalutamide both individually and in combination to analyze cell viability under different levels of dihydrotestosterone (DHT). The inhibition of androgen receptor (AR) followed by the expression of prostate-specific antigen (PSA) and the efflux mechanism of the cells were analyzed to determine the effect of the combination on the cellular mechanism. Cells derived from prostate cancer patients were also tested with the combination. Only 6 µM enzalutamide along with BS in the range of 4.1 µg/ml to 16.4 µg/ml gave the best synergistic results with nearly 50% cell killing even though standard enzalutamide doses were as high as 48 µM. Cell killing was most effective at intermediate DHT concentrations of approximately 1 nM, which corresponds to normal physiological serum levels of DHT. The Pgp expression level and the androgen receptor expression levels were reduced under the combination treatment; the former helping to minimize drug efflux and the latter by reducing the sensitivity to hormonal changes. Furthermore, the combination reduced the PSA level secreted by the cells. In contrast, AKBA could not achieve the needed synergism for adequate cell killing at equivalent concentrations. The combination of enzalutamide and BS extract containing 30% AKBA because of their synergistic interaction is an attractive therapeutic option for treating early stage (hormone-dependent) prostate cancer and is superior to the use of AKBA alone.

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Tumor protein D52 (isoform 3) contributes to prostate cancer cell growth via targeting nuclear factor-κB transactivation in LNCaP cells

Tumor Biology ◽

10.1177/1010428317698382 ◽

2017 ◽

Vol 39 (5) ◽

pp. 101042831769838 ◽

Cited By ~ 8

Author(s):

Chandrashekhar Dasari ◽

Dattu Prasad Yaghnam ◽

Reinhard Walther ◽

Ramesh Ummanni

Keyword(s):

Prostate Cancer ◽

Cell Adhesion ◽

Cancer Progression ◽

Underlying Mechanism ◽

Nuclear Factor Κb ◽

Tissue Inhibitor Of Metalloproteinase ◽

Nuclear Factor ◽

Prostate Cancer Progression ◽

Lncap Cells ◽

Cancer Cell Growth

Our previous study showed that TPD52 overexpression could increase migration and proliferation of LNCaP cells contributing to the development of prostate cancer. However, mechanism of TPD52 in prostate cancer initiation and progression remains elusive. In this study, we investigated the possible underlying mechanism of TPD52 in prostate cancer progression. In LNCaP cells, TPD52 expression was altered by transfecting with either EGFP-TPD52 or specific short hairpin RNA. Overexpression of TPD52 protected LNCaP cells from apoptosis through elevated anti-apoptotic proteins XIAP, Bcl-2, and Cyclin D1, whereas Bax was downregulated. Mechanistically, we found that TPD52 confers transactivation of nuclear factor-κB, thereby enhancing its target gene expression in LNCaP cells. TPD52 promotes LNCaP cell invasion probably via increased matrix metalloproteinase 9 expression and its activity while tissue inhibitor of metalloproteinase expression is significantly downregulated. Notably, TPD52 might be involved in cell adhesion, promoting tumor metastasis by inducing loss of E-cadherin, expression of vimentin and vascular cell adhesion molecule, and additionally activation of focal adhesion kinase. Furthermore, TPD52 directly interacts with nuclear factor-κB p65 (RelA) and promotes accumulation of phosphorylated nuclear factor-κB (p65)S536 that is directly linked with nuclear factor-κB transactivation. Indeed, depletion of TPD52 or inhibition of nuclear factor-κB in TPD52-positive cells inhibited secretion of tumor-related cytokines and contributes to the activation of STAT3, nuclear factor-κB, and Akt. Interestingly, in TPD52 overexpressing LNCaP cells, nuclear factor-κB inhibition prevented the autocrine/paracrine activation of STAT3. TPD52 activates STAT3 through ascertaining a cross talk between the nuclear factor-κB and the STAT3 signaling systems. Collectively, these results reveal mechanism by which TPD52 is associated with prostate cancer progression and highlight the approach for therapeutic targeting of TPD52 in prostate cancer.

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