Inflammation‐mediated abrogation of androgen signaling: An in vitro model of prostate cell inflammation

Abstract

As a link between inflammation and cancer has been reported in many studies, we established an in vitro model of prostatic inflammation to investigate the loss of androgen receptor (AR)-mediated signaling in androgen responsive prostate cell lines. First, the U937 monocyte cell line was differentiated into macrophages using phorbol acetate (PMA), and cells were induced with lipopolysaccharide (LPS) for cytokine secretion. Next, the cytokine levels (TNFa, IL-6, and IL1b) in conditioned media (CM) were analyzed. Prostate cells were then fed with CM containing varying concentrations of TNFa, and IkB degradation, nuclear factor kappa B (NFkB) translocation and transactivation, and the expression of matrix metalloproteinase-8 (MMP8) and matrix metalloproteinase-9 (MMP9) were then assessed. As a result of CM treatment, ubiquitin-mediated AR degradation, which was restored using anti-TNFa antibody neutralization, led to both a decrease in KLK4, PSA, and NKX3.1 expression levels and the upregulation of GPX2. In addition to the loss of AR, acute and chronic CM exposure resulted in p53 degradation and consequent p21 downregulation, which was also restored by either androgen administration or ectopic NKX3.1 expression via the stabilization of MDM2 levels in LNCaP cells. Additionally, CM treatment enhanced H2AX (S139) phosphorylation (a hallmark of DNA damage) and genetic heterogeneity in the absence of androgens in prostate cells without activating mitochondrial apoptosis. Thus, the data suggest that inflammatory cytokine exposure results in the loss of AR and p53 signaling in prostate cells and facilitates genetic heterogeneity via ROS accumulation to promote prostate carcinogenesis.

Identification of Filamin-A and -B As Potential Biomarkers for Prostate Cancer

“…The expression levels of FLNA , FLNB , and KRT19 were not regulated by TNFα exposure in any cell type (Figure 2B). In contrast, PSA expression was significantly decreased by TNFα exposure in LnCAP cells, consistent with previous reports that androgen receptor (AR) signaling is suppressed by inflammation [19]. Similarly, when LnCAP, DU145 and PC-3 cells were treated with the R1881, FLNA , FLNB and KRT19 were not significantly affected, while PSA expression was significantly altered in LnCAP cells (19-fold increase; Figure 2C), which is expected for an AR target gene [20].…”

Non-Cell-Autonomous Regulation of Prostate Epithelial Homeostasis by Androgen Receptor

“…We demonstrate directly in vivo that attenuation of luminal epithelial AR signaling is capable of inducing prostate inflammation. On the other hand, inflammation has also been shown to suppress expression of AR and critical enzymes for testosterone metabolism (Debelec-Butuner et al, 2014; Khalili et al, 2010; Shinohara et al, 2013; Simons et al, 2014; Vignozzi et al, 2012a). Together, these results suggest a mutual induction between prostate inflammation and reduced luminal AR expression and imply the existence of a vicious cycle of prostate inflammation enforced by declining epithelial AR signaling.…”

Use of Non-steroidal Anti-inflammatory Drugs for Chemoprevention of Inflammation-induced Prostate Cancer

“…Surprisingly, it is known that NSAIDs such as indomethacin 31 can activate Akt signaling, which enhances S473 phosphorylation, consistent with our results. Increased p-Akt (S473) levels result in NKX3.1 suppression 9 ; the negative correlation between NKX3.1 recovery and Akt phosphorylation in our results suggests that NSAIDs that lead to unexpected activation of Akt signaling such as indomethacin should be taken into account for their effects on tumor suppressor NKX3.1. On the other hand, sulindac was shown to suppress this activation in our results, as well as in a previous study 32 , which supports its inhibition potential on inflammation-induced tumorigenic events.…”

“…A decrease in NKX3.1 protein level due to cytokine-induced degradation was observed after CM as detected in our previous studies. 9,10 It was also determined that indomethacin, celecoxib, and nimesulide at their NF-κB inhibitory concentrations enhanced this degradation. NKX3.1 levels remained the same with sulindac, ibuprofen, and naproxen.…”

“…[2][3][4][5][6][7] In addition, inflammation-related alterations of the androgen receptor (AR), NKX3.1, and Akt, which regulate cell proliferation in co-operation, have a significant role in prostate tumorigenesis. [8][9][10] The negative correlation between the use of anti-inflammatory drugs and cancer incidence proves that active inflammation supports carcinogenesis, and anti-inflammatory drugs can prevent inflammation-related tumorigenesis. 4,5 Inflammation leads to neoplastic transformation by altering gene expression levels of oncogenes and tumor suppressors.…”