The androgen receptor—lncRNASAT1-AKT-p15 axis mediates androgen-induced cellular senescence in prostate cancer cells

Abstract

The bipolar androgen therapy (BAT) to treat prostate cancer (PCa) includes cycles of supraphysiological androgen levels (SAL) under androgen-deprivation therapy (ADT). We showed previously that SAL induces cellular senescence in androgen-sensitive PCa cells and in ex vivo-treated patient PCa tumor samples. Here, we analyzed the underlying molecular pathway and reveal that SAL induces cellular senescence in both, castration-sensitive (CSPC) LNCaP and castration-resistant PCa (CRPC) C4-2 cells through the cell cycle inhibitor p15INK4b and increased phosphorylation of AKT. Treatment with the AKT inhibitor (AKTi) potently inhibited SAL-induced expression of p15INK4b and cellular senescence in both cell lines. Proximity-ligation assays (PLA) combined with high-resolution laser-scanning microscopy indicate that SAL promotes interaction of endogenous androgen receptor (AR) with AKT in the cytoplasm as well as in the nucleus detectable after three days. Transcriptome sequencing (RNA-seq) comparing the SAL-induced transcriptomes of LNCaP with C4-2 cells as well as with AKTi-treated cell transcriptomes revealed landscapes for cell senescence. Interestingly, one of the identified genes is the lncRNASAT1. SAL treatment of native patient tumor samples ex vivo upregulates lncRNASAT1. In PCa tumor tissues, lncRNASAT1 is downregulated compared with nontumor tissues of the same patients. Knockdown indicates that the lncRNASAT1 is crucial for SAL-induced cancer-cell senescence as an upstream factor for pAKT and for p15INK4b. Further, knockdown of lncRNASAT1 enhances cell proliferation by SAL, suggesting that lncRNASAT1 serves as a tumor suppressor at SAL. Interestingly, immunoprecipitation of AR detected lncRNASAT1 as an AR-interacting partner that regulates AR target-gene expression. Similarly, RNA-ChIP experiments revealed the interaction of AR with lncRNASAT1 on chromatin. Thus, we identified a novel AR-lncRNASAT1-AKT-p15INK4b signaling axis to mediate SAL-induced cellular senescence.

Sexually dimorphic activation of innate antitumour immunity prevents adrenocortical carcinoma development

“…Our data showing a strong association between induction of SASP and recruitment of macrophages suggest that androgens may stimulate the tumoricidal response by inducing release of senescence associated cytokines by Znrf3 cKO cells (Fig 6). In line with this hypothesis, AR activation was shown to induce p53-independent senescence in prostate cancer cells 66,67 and a short-term testosterone treatment was sufficient to induce SA-bgalactosidase activity in female Znrf3 cKO adrenals (Fig 6). This raises the question of the links between Znrf3 inactivation, AR signalling and senescence induction.…”

Senescence-Induced Immune Remodeling Facilitates Metastatic Adrenal Cancer in a Sex-Dimorphic Manner

“…These findings suggest that the renewal capacity of the male adrenal cortex is inherently lower at baseline compared with females, which could explain the earlier proliferative arrest in males. Additionally, androgens have independently been shown to activate cellular senescence in vitro 58,59 and the androgen receptor (AR) can directly activate p21 through an androgen response element in the proximal promoter 60 . Consequently, androgen signaling in males may help accelerate cellular senescence through parallel pathway activation.…”

PITX1 Is a Regulator of TERT Expression in Prostate Cancer with Prognostic Power

“…PCa cell lines were cultured in their respective growth medium up to a maximum of 80% confluence in a CO 2 incubator (5%). Respective Cell line/medium pairs were: LNCaP-tet (received 2003) in RPMI 1640 supplement with 10% FCS, 25 mM HEPES (pH 7.5), penicillin (100 U/mL), streptomycin (100 U/mL); C4-2 (received 2000) in DMEM containing phenol red supplemented with 5% FCS, 25 mM HEPES (pH 7.5), penicillin (100 U/mL), streptomycin (100 U/mL), 20% F-12 nutrient mix; PC3 (received 2004) and PC3-AR (received 2004) in RPMI 1640 supplement with 10% heat inactivated FCS, 25 mM HEPES (pH 7.5), penicillin (100 U/mL), streptomycin (100 U/mL) [ 46 , 47 , 48 ].…”