Promotes Prostate Cancer Cell Growth Research Articles

A novel intronic circular RNA circFGFR1int2 up-regulates FGFR1 by recruiting transcriptional activators P65/FUS and suppressing miR-4687-5p to promote prostate cancer progression

Fibroblast growth factor receptor 1 (FGFR1) is a core component of the FGFs/FGFR pathway that activates multiple signalling pathways, including ERK1/2, PI3K/AKT, PLCγ, and NF-κB. Aberrant expression of FGFR1 due to gene amplification, chromosome rearrangement, point mutation, and epigenetic deregulations, have been reported in various cancers. FGFR1 overexpression has also been reported in prostate cancer (PCa), but the underlining mechanisms are not clear. Here we report a novel circular RNA, circFGFR1int2, derived from intron 2 of FGFR1 gene, which is overexpressed in PCa and associated with tumor progression. Importantly, we show that circFGFR1int2 facilitates FGFR1 transcription by recruiting transcription activators P65/FUS and by interacting with FGFR1 promoter. Moreover, we show that circFGFR1int2 suppresses post-transcriptional inhibitory effects of miR-4687-5p on FGFR1 mRNA. These mechanisms synergistically promote PCa cell growth, migration, and invasion. Overexpression of circFGFR1int2 is significantly correlated with higher tumor grade, Gleason score, and PSA level, and is a significant unfavorable prognosticator for CRPC-free survival (CFS) (RR = 3.277, 95% confidence interval: 1.192–9.009; P = 0.021). These findings unravelled novel mechanisms controlling FGFR1 gene expression by intronic circRNA and its potential clinicopathological utility as a diagnostic or therapeutic target.Graphic

Prognostic and therapeutic potential of senescent stromal fibroblasts in prostate cancer.

The stromal component of the tumour microenvironment in primary and metastatic prostate cancer can influence and promote disease progression. Within the prostatic stroma, fibroblasts are one of the most prevalent cell types associated with precancerous and cancerous lesions; they have a vital role in the structural composition, organization and integrity of the extracellular matrix. Fibroblasts within the tumour microenvironment can undergo cellular senescence, which is a stable arrest of cell growth and a phenomenon that is emerging as a recognized hallmark of cancer. Supporting the idea that cellular senescence has a pro-tumorigenic role, a subset of senescent cells exhibits a senescence-associated secretory phenotype (SASP), which, along with increased inflammation, can promote prostate cancer cell growth and survival. These cellular characteristics make targeting senescent cells and/or modulating SASP attractive as a potential preventive or therapeutic option for prostate cancer.

Gain-of-function mutant p53 together with ERG proto-oncogene drive prostate cancer by beta-catenin activation and pyrimidine synthesis

Whether TMPRSS2-ERG fusion and TP53 gene alteration coordinately promote prostate cancer (PCa) remains unclear. Here we demonstrate that TMPRSS2-ERG fusion and TP53 mutation / deletion co-occur in PCa patient specimens and this co-occurrence accelerates prostatic oncogenesis. p53 gain-of-function (GOF) mutants are now shown to bind to a unique DNA sequence in the CTNNB1 gene promoter and transactivate its expression. ERG and β-Catenin co-occupy sites at pyrimidine synthesis gene (PSG) loci and promote PSG expression, pyrimidine synthesis and PCa growth. β-Catenin inhibition by small molecule inhibitors or oligonucleotide-based PROTAC suppresses TMPRSS2-ERG- and p53 mutant-positive PCa cell growth in vitro and in mice. Our study identifies a gene transactivation function of GOF mutant p53 and reveals β-Catenin as a transcriptional target gene of p53 GOF mutants and a driver and therapeutic target of TMPRSS2-ERG- and p53 GOF mutant-positive PCa.

Cancer associated fibroblasts secreted exosomal miR-1290 contributes to prostate cancer cell growth and metastasis via targeting GSK3β

Cancer-associated fibroblasts (CAFs) play crucial roles in mediating tumor growth and metastasis via transferring exosomes to neighboring cells, whereas the mechanisms by which CAFs regulate the tumorgenesis of prostate cancer (PC) remain largely unknown. In this study, CAFs and normal fibroblasts (NFs) were isolated from PC tissues and adjacent normal tissues, respectively. Exosomes (NFs-Exo and CAFs-Exo) were then isolated from the supernatant of NFs and CAFs. Next, the differentially expressed miRNAs (DEMs) between NFs-Exo and CAFs-Exo were identified using RNA-sequencing. Cell viability, migration and invasion were detected with CCK-8 and Transwell assays. Protein expression was measured with western blot. We found that CAFs-Exo remarkably enhanced PC cell migration, invasion, stemness, epithelial-mesenchymal transition (EMT) and metastasis. Significantly, miR-1290 level was upregulated in CAFs-Exo compared to NFs-Exo. In addition, CAFs could transfer exosomes to PC cells, resulting in a marked increase of miR-1290 level in cells. Moreover, exosomal miR-1290 could inhibit GSK3β/β-catenin signaling by binding with the downstream target GSK3β mRNA. Meanwhile, miR-1290 antagomir notably reversed the effects of CAFs-Exo on PC cells through activating GSK3β/β-catenin signaling. Collectively, exosomal miR-1290 from CAFs could promote PC cell growth and metastasis via inhibiting GSK3β/β-catenin signaling, suggesting that miR-1290 may serve as potential therapeutic target for the treatment of PC.

Systemic Ablation of Camkk2 Impairs Metastatic Colonization and Improves Insulin Sensitivity in TRAMP Mice: Evidence for Cancer Cell-Extrinsic CAMKK2 Functions in Prostate Cancer.

Despite early studies linking calcium-calmodulin protein kinase kinase 2 (CAMKK2) to prostate cancer cell migration and invasion, the role of CAMKK2 in metastasis in vivo remains unclear. Moreover, while CAMKK2 is known to regulate systemic metabolism, whether CAMKK2’s effects on whole-body metabolism would impact prostate cancer progression and/or related comorbidities is not known. Here, we demonstrate that germline ablation of Camkk2 slows, but does not stop, primary prostate tumorigenesis in the TRansgenic Adenocarcinoma Mouse Prostate (TRAMP) genetic mouse model. Consistent with prior epidemiological reports supporting a link between obesity and prostate cancer aggressiveness, TRAMP mice fed a high-fat diet exhibited a pronounced increase in the colonization of lung metastases. We demonstrated that this effect on the metastatic spread was dependent on CAMKK2. Notably, diet-induced lung metastases exhibited a highly aggressive neuroendocrine phenotype. Concurrently, Camkk2 deletion improved insulin sensitivity in the same mice. Histological analyses revealed that cancer cells were smaller in the TRAMP;Camkk2−/− mice compared to TRAMP;Camkk2+/+ controls. Given the differences in circulating insulin levels, a known regulator of cell growth, we hypothesized that systemic CAMKK2 could promote prostate cancer cell growth and disease progression in part through cancer cell-extrinsic mechanisms. Accordingly, host deletion of Camkk2 impaired the growth of syngeneic murine prostate tumors in vivo, confirming nonautonomous roles for CAMKK2 in prostate cancer. Cancer cell size and mTOR signaling was diminished in tumors propagated in Camkk2-null mice. Together, these data indicate that, in addition to cancer cell-intrinsic roles, CAMKK2 mediates prostate cancer progression via tumor-extrinsic mechanisms. Further, we propose that CAMKK2 inhibition may also help combat common metabolic comorbidities in men with advanced prostate cancer.

LncRNA-AP006284.1 promotes prostate cancer cell growth and motility by forming RNA-DNA triplexes and recruiting GNL3/SFPQ complex to facilitate RASSF7 transcription

LncRNA-AP006284.1 promotes prostate cancer cell growth and motility by forming RNA-DNA triplexes and recruiting GNL3/SFPQ complex to facilitate RASSF7 transcription

MED12 Mutations Promote Castration Resistant Prostate Cancer Through Hyper‐activated SHH Signaling

Prostate cancer is the most common malignancy and the second leading cause of cancer associated deaths among US men. As an androgen-driven disease, prostate cancer is critically dependent upon androgen receptor (AR) signaling. Accordingly, most prostate cancer patients respond very well to androgen deprivation therapy. The current problem lies with the fact that nearly all patients progress to a lethal form of the disease after androgen deprivation therapy known as castration resistant prostate cancer (CRPC). Once patients reach the stage of CRPC, treatment options are frustratingly limited and average survival times range from two to three years only. Thus, there is a compelling need to develop effective treatments for patients suffering from CRPC. Sonic hedgehog (SHH) signaling is a stromal-epithelial interacting pathway that is critical for prostate development and cell growth. SHH signaling is induced by androgen deprivation thereby leading to re-activation of AR target genes to promote prostate cancer cell growth in the absence of androgens. Furthermore, AR interacts with GLI proteins, downstream effectors in the SHH pathway. Therefore, GLI3-dependent SHH signaling in androgen deprived cells could promote re-activation of AR target genes and consequently lead to CRPC. It is currently unknown how GLI3-dependent SHH signaling is induced in CRPC. Several studies have found that MED12, a subunit of Mediator, is commonly mutated in prostate cancer and, interestingly, MED12 has been shown to play a critical role in restricting GLI3-dependent SHH signaling. We therefore hypothesize that MED12 mutations promote GLI3-dependent SHH signaling in prostate cancer to drive progression towards CRPC. We generated stable MED12 knockdown cells, which likely recapitulates a MED12 mutant setting, followed by proliferation and qPCR assays in androgen replete and androgen deprived conditions to test our hypothesis. Our results show that MED12 knockdown promotes prostate cancer growth specifically in an androgen deprived setting and that this hyper-active growth is dependent upon GLI3. Furthermore, we also show that GLI3 target genes are sharply upregulated when MED12 expression is low and androgens are absent. The collective results of our study therefore indicate that prostate cancer patients with MED12 mutations could relapse to CRPC after androgen deprivation therapy by hyperactivating the GLI3 dependent SHH signaling pathway. Importantly, our results thus suggest that therapeutic agents that target the SHH signaling pathway could prove to be beneficial for MED12 mutant prostate cancer patients.

CLICK-enabled analogues reveal pregnenolone interactomes in cancer and immune cells

SummaryPregnenolone (P5) promotes prostate cancer cell growth, and de novo synthesis of intratumoural P5 is a potential cause of development of castration resistance. Immune cells can also synthesize P5 de novo. Despite its biological importance, little is known about P5's mode of actions, which appears to be context dependent and pleiotropic. A comprehensive proteome-wide spectrum of P5-binding proteins that are involved in its trafficking and functionality remains unknown. Here, we describe an approach that integrates chemical biology for probe synthesis with chemoproteomics to map P5-protein interactions in live prostate cancer cells and murine CD8+ T cells. We subsequently identified P5-binding proteins potentially involved in P5-trafficking and in P5's non-genomic action that may drive the promotion of castrate-resistance prostate cancer and regulate CD8+ T cell function. We envisage that this methodology could be employed for other steroids to map their interactomes directly in a broad range of living cells, tissues, and organisms.

Dietary Fructose Promotes Prostate Cancer Growth.

Clinical localization of primary tumors and sites of metastasis by PET is based on the enhanced cellular uptake of 2-deoxy-2-[18F]-fluoro-D-glucose (FDG). In prostate cancer, however, PET-FDG imaging has shown limited clinical applicability, suggesting that prostate cancer cells may utilize hexoses other than glucose, such as fructose, as the preferred energy source. Our previous studies suggested that prostate cancer cells overexpress fructose transporters, but not glucose transporters, compared with benign cells. Here, we focused on validating the functional expression of fructose transporters and determining whether fructose can modulate the biology of prostate cancer cells in vitro and in vivo. Fructose transporters, Glut5 and Glut9, were significantly upregulated in clinical specimens of prostate cancer when compared with their benign counterparts. Fructose levels in the serum of patients with prostate cancer were significantly higher than healthy subjects. Functional expression of fructose transporters was confirmed in prostate cancer cell lines. A detailed kinetic characterization indicated that Glut5 represents the main functional contributor in mediating fructose transport in prostate cancer cells. Fructose stimulated proliferation and invasion of prostate cancer cells in vitro. In addition, dietary fructose increased the growth of prostate cancer cell line-derived xenograft tumors and promoted prostate cancer cell proliferation in patient-derived xenografts. Gene set enrichment analysis confirmed that fructose stimulation enriched for proliferation-related pathways in prostate cancer cells. These results demonstrate that fructose promotes prostate cancer cell growth and aggressiveness in vitro and in vivo and may represent an alternative energy source for prostate cancer cells. SIGNIFICANCE: This study identifies increased expression of fructose transporters in prostate cancer and demonstrates a role for fructose as a key metabolic substrate supporting prostate cancer cells, revealing potential therapeutic targets and biomarkers.

Androgen downregulation of miR-760 promotes prostate cancer cell growth by regulating IL6.

Prostate cancer (PCa) is one of the most common malignancies in Western countries. Studies have shown that androgen contributes to the progression of PCa, but how androgen promotes PCa remains largely unknown. Here, we demonstrated that androgen suppressed the expression of miR-760 depending on the interaction between androgen and androgen receptor (AR). miR-760 was downregulated in prostate cancer tissues compared with normal tissues. Functional experiments showed that miR-760 downregulation promoted the proliferation and growth of LNCaP and 22rv1 cells. In contrast, miR-760 ectopic expression inhibited the proliferation of LNCaP and 22rv1 cells. DNA synthesis was suppressed by miR-760. Mechanistically, miR-760 bound to the 3'UTR of interleukin 6 (IL6). A mutation in the binding site disrupted their interaction. In addition, silencing of IL6 suppressed the proliferation of LNCaP and 22rv1 cells. IL6 was upregulated in PCa tissues. Our study reveals that androgen downregulates miR-760 to promote the growth of PCa cells by regulating IL6.

P53 Mutant p53N236S Regulates Cancer-Associated Fibroblasts Properties Through Stat3 Pathway.

BackgroundCancer-associated fibroblasts (CAFs) play important roles in cancer development and progression. Recent studies show that p53 plays a cell non-autonomous tumor-suppressive role to restrict tumor growth in CAFs. However, the role of p53 mutant in CAFs remains obscure.MethodsIn this study, the contribution of p53 mutant p53N236S (p53S) to CAFs activation was examined using mouse embryonic fibroblasts (MEFs) from wild-type (WT), p53 deficient (p53-/-) and p53S/S mice. The role of p53S in MEFs in inducing prostate cancer cell growth and metastasis was studied by utilizing xenograft models and transwell assays. The effects of p53S on the properties of CAFs were assessed by measuring CAFs-specific factors expression and functional collagen contraction assay. Moreover, Microarray data were analyzed by GSEA and Stat3 signaling was inhibited to further determine p53S’s role in the CAFs activation.ResultsWe found that p53S/S MEF accelerated cancer cells growth and metastasis compared with WT and p53-/- MEF. We also found that p53S induced significantly increasing collagen contraction in fibroblasts and overexpression of CAFs-specific factors, such as α-smooth muscle actin (α-SMA), FGF10 and CXCL12. p53S regulated these CAF-specific properties through Stat3 activation.ConclusionOur results illustrate that p53S plays an important role in CAFs activation by the Stat3 pathway. The study indicates that cancer cells and fibroblasts interaction promotes prostate cancer cell growth, migration and invasion due to p53S expression in fibroblasts.

Extracellular vesicle-derived circ_SLC19A1 promotes prostate cancer cell growth and invasion through the miR-497/septin 2 pathway.

The occurrence and development of prostate cancer (PCa) is complex, and the related mechanism is not fully understood. Current studies have found that extracellular vesicles (EVs) and circular RNAs (circRNAs) have important functions in various tumours and other diseases. In this study, the detection of circRNAs in PCa showed that circ_SLC19A1 was increased in PCa cells and their secreted EVs. EVs with high expression of circ_SLC19A1 could be taken up by PCa cells, which promoted cell proliferation and invasion. The sequence of circ_SLC19A1 contained multiple binding sites for miR-497, and circ_SLC19A1 could bind directly to miR-497 in cells. The expression of miR-497 was downregulated in PCa cells, while the expression of its target gene septin 2 (SEPT2) was upregulated significantly. Transfection of circ_SLC19A1 small interfering RNA (siRNA) or miR-497 mimics could significantly inhibit the expression of SEPT2 and the phosphorylation of extracellular signal-regulated kinase 1 and 2 (ERK1/2). After co-transfection of circ_SLC19A1 siRNA and miR-497 inhibitors or SEPT2 overexpression vector, the expression of SEPT2 and ERK1/2 phosphorylation levels showed no significant changes. Similar results were obtained with co-transfection of miR-497 mimics and the SEPT2 overexpression vector. Therefore, cancer cells can regulate the expression of SEPT2 through miR-497 by secreting EVs with high expression of circ_SLC19A1, thus affecting the activation of the downstream ERK1/2 pathway and ultimately regulating PCa cell growth and invasion. Therefore, EV-derived circ_SLC19A1 plays an important regulatory role in PCa and may be an important target for PCa prevention and treatment.

USE OF TESTOSTERONE REPLACEMENT THERAPY AFTER RADICAL PROSTATECTOMY MIGHT KILL TWO BIRDS WITH ONE STONE FROM THE PERSPECTIVE OF MEN’S HEALTH AND DISEASE CONTROL

Testosterone plays an important role in promoting the differentiation and stimulation of prostate epi-thelial cells. Adding to the basic physiology of testosterone, several studies led to the dissemination of the historical androgen hypothesis that higher circulating androgen levels promote prostate cancer cell growth and make the tumor more aggressive. Whereas, the prostate saturation model accounted for the androgen sensitivity of testosterone stimulation in the prostate up to a saturation point, which occurred near the level of castration. Testosterone is related to prostate cancer metabolism in a com-plex manner; however, within the reference range, high or normal testosterone levels are expected to maintain benign and malignant prostate cells in a differentiated state. Accumulating evidence has suggested that testosterone replacement therapy (TRT) might prevent the development of prostate cancer and even reduce prostate cancer risk. There is no change in the clinical guidelines to be followed when considering TRT in patients with a history of prostate cancer, but it is necessary for the physician to inform patients of the positive effects of TRT on male health and prostate cancer.

Analysis of PMEPA1 Isoforms (a and b) as Selective Inhibitors of Androgen and TGF-β Signaling Reveals Distinct Biological and Prognostic Features in Prostate Cancer.

Dysfunctions of androgen/TGF-β signaling play important roles in prostate tumorigenesis. Prostate Transmembrane Protein Androgen Induced 1 (PMEPA1) inhibits androgen and TGF-β signaling via a negative feedback loop. The loss of PMEPA1 confers resistance to androgen signaling inhibitors and promotes bone metastasis. Conflicting reports on the expression and biological functions of PMEPA1 in prostate and other cancers propelled us to investigate isoform specific functions in prostate cancer (PCa). One hundred and twenty laser capture micro-dissection matched normal prostate and prostate tumor tissues were analyzed for correlations between quantitative expression of PMEPA1 isoforms and clinical outcomes with Q-RT-PCR, and further validated with a The Cancer Genome Atlas (TCGA) RNA-Seq dataset of 499 PCa. Cell proliferation was assessed with cell counting, plating efficiency and soft agar assay in androgen responsive LNCaP and TGF-β responsive PC3 cells. TGF-β signaling was measured by SMAD dual-luciferase reporter assay. Higher PMEPA1-a mRNA levels indicated biochemical recurrence (p = 0.0183) and lower PMEPA1-b expression associated with metastasis (p = 0.0173). Further, lower PMEPA1-b and a higher ratio of PMEPA1-a vs. -b were correlated to higher Gleason scores and lower progression free survival rate (p < 0.01). TGF-β-responsive PMEPA1-a promoted PCa cell growth, and androgen-responsive PMEPA1-b inhibited cancer cell proliferation. PMEPA1 isoforms -a and -b were shown to be promising candidate biomarkers indicating PCa aggressiveness including earlier biochemical relapse and lower disease specific life expectancy via interrupting androgen/TGF-β signaling.

Med12 Mutations Promote Castration Resistant Prostate Cancer through Hyperactivated GLI3/SHH Signaling

Prostate cancer is the highest diagnosed and second most common cause of cancer death among US men. The onset and progression of prostate cancer is critically dependent upon androgens through their interaction with the androgen receptor (AR). Accordingly, it has long been established that androgen deprivation therapy leads to prostate cancer regression. Though androgen deprivation therapies are initially highly successful, most patients eventually suffer from recurrence of the disease in the form of castration resistant prostate cancer (CRPC). Currently there is no effective treatment for CRPC thereby highlighting the compelling need to address resistance mechanisms for patients that suffer from this lethal disease. Sonic hedgehog (SHH) signaling is a stromal‐epithelial interacting pathway that is critical for prostate development and cell growth. SHH signaling is induced by androgen deprivation thereby leading to re‐activation of AR target genes to promote prostate cancer cell growth in the absence of androgens. Furthermore, AR interacts with GLI proteins, downstream effectors in the SHH pathway. Therefore, GLI3‐dependent SHH signaling in androgen deprived cells could promote re‐activation of AR target genes and consequently lead to CRPC. It is currently unknown how GLI3‐dependent SHH signaling is induced in CRPC. In this study we show that stabilized GLI3 leads to the induction of GLI3‐dependent SHH signaling in prostate cancers that harbor mutations in MED12. MED12 is an Xq13‐encoded 230 kDa subunit of the RNA pol II transcriptional Mediator that has been found to be mutated in ~5% of prostate cancers. Through stable knockdown and luciferase assays, we show that MED12 mutations disrupt a Mediator‐imposed constraint on GLI3‐dependent SHH signaling. Furthermore, through stable knockdown and xenograft studies, we show that stable GLI3 is critically dependent for CRPC growth. The results of our study therefore indicate that prostate cancer patients with MED12 mutations relapse to CRPC after androgen deprivation therapy by hyperactivating the GLI3 dependent SHH signaling pathway. Overall, this study provides critical insight into possible treatment strategies for prostate cancer patients with MED12 mutations by using the GLI3/SHH signaling axis as a therapeutic target.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Roles of the HOXA10 gene during castrate-resistant prostate cancer progression.

Homeobox A10 (HOXA10) is an important transcription factor that regulates the development of the prostate gland. However, it remains unknown whether it modulates prostate cancer (PCa) progression into castrate-resistant stages. In this study, we have applied RNA in situ hybridization assays to demonstrate that downregulation of HOXA10 expression is associated with castrate-resistant PCa. These findings are supported by public RNA-seq data showing that reduced HOXA10 expression is correlated with poor patient survival. We show that HOXA10 suppresses PCa cell proliferation, anchorage colony formation and xenograft growth independent to androgens. Using AmpliSeq transcriptome sequencing, we have found that gene groups associated with lipid metabolism and androgen receptor (AR) signaling are enriched in the HOXA10 transcriptome. Furthermore, we demonstrate that HOXA10 suppresses the transcription of the fatty acid synthase (FASN) gene by forming a protein complex with AR and prevents AR recruitment to the FASN gene promoter. These results lead us to conclude that downregulation of HOXA10 gene expression may enhance lipogenesis to promote PCa cell growth and tumor progression to castrate-resistant stage.

Tumor Cell Autonomous RON Receptor Expression Promotes Prostate Cancer Growth Under Conditions of Androgen Deprivation

Current treatment strategies provide minimal results for patients with castration-resistant prostate cancer (CRPC). Attempts to target the androgen receptor have shown promise, but resistance ultimately develops, often due to androgen receptor reactivation. Understanding mechanisms of resistance, including androgen receptor reactivation, is crucial for development of more efficacious CRPC therapies. Here, we report that the RON receptor tyrosine kinase is highly expressed in the majority of human hormone-refractory prostate cancers. Further, we show that exogenous expression of RON in human and murine prostate cancer cells circumvents sensitivity to androgen deprivation and promotes prostate cancer cell growth in both in vivo and in vitro settings. Conversely, RON loss induces sensitivity of CRPC cells to androgen deprivation. Mechanistically, we demonstrate that RON overexpression leads to activation of multiple oncogenic transcription factors (namely, β-catenin and NF-κB), which are sufficient to drive androgen receptor nuclear localization and activation of AR responsive genes under conditions of androgen deprivation and support castration-resistant growth. In total, this study demonstrates the functional significance of RON during prostate cancer progression and provides a strong rationale for targeting RON signaling in prostate cancer as a means to limit resistance to androgen deprivation therapy.

Antimony enhances c-Myc stability in prostate cancer via activating CtBP2-ROCK1 signaling pathway

Antimony, one of the heavier pnictogens, is widely used in industry, and its toxicity has become a major concern. Although previous studies suggested that antimony might be a tumorigenic risk factor in several cancers, the molecular basis underlying antimony-mediated transformation remains unclear. Our results showed that the serum concentration of antimony was higher in prostate cancer specimens relative to that of benign prostate tissues, and this high serum concentration of antimony was closely associated with poorer outcome in prostate cancer patients. Additionally, we demonstrated that antimony could promote prostate cancer cell growth in vitro and in vivo. In order to gain insight into the potential mechanisms, we examined the effects of antimony exposure on downstream signaling that could contribute to tumor development. We found that low-dose antimony could regulate the expression of Ctbp2 by binding and regulating the activity of its MRE domain. Meanwhile, CtBP2 could transcriptionally regulate the expression of RhoC, which is a member of the RhoGTPase family. Subsequently, the kinase activity of ROCK1 is increased, which promotes the stability of oncogene c-Myc. Overall, our study demonstrated that antimony could enhance c-Myc protein stability and promote prostate cancer cell proliferation through activating CtBP2-ROCK1 signaling pathway. These findings also substantially highlighted the potential of targeting molecules within antimony induced CtBP2-c-Myc signaling pathway as a promising therapeutic approach for the treatment of prostate cancer.

Frequently rearranged and overexpressed δ-catenin is responsible for low sensitivity of prostate cancer cells to androgen receptor and β-catenin antagonists.

The mechanism of prostate cancer (PCa) progression towards the hormone refractory state remains poorly understood. Treatment options for such patients are limited and present a major clinical challenge. Previously, δ-catenin was reported to promote PCa cell growth in vitro and its increased level is associated with PCa progression in vivo. In this study we show that re-arrangements at Catenin Delta 2 (CTNND2) locus, including gene duplications, are very common in clinically significant PCa and may underlie δ-catenin overexpression. We find that δ-catenin in PCa cells exists in a complex with E-cadherin, p120, and α- and β-catenin. Increased expression of δ-catenin leads to its further stabilization as well as upregulation and stabilization of its binding partners. Resistant to degradation and overexpressed δ-catenin isoform activates Wnt signaling pathway by increasing the level of nuclear β-catenin and subsequent stimulation of Tcf/Lef transcription targets. Evaluation of responses to treatments, with androgen receptor (AR) antagonist and β-catenin inhibitors revealed that cells with high levels of δ-catenin are more resistant to killing with single agent treatment than matched control cells. We show that combination treatment targeting both AR and β-catenin networks is more effective in suppressing tumor growth than targeting a single network. In conclusion, targeting clinically significant PCa with high levels of δ–catenin with anti-androgen and anti β-catenin combination therapy may prevent progression of the disease to a castration-resistant state and, thus, represents a promising therapeutic strategy.

GLUT12 promotes prostate cancer cell growth and is regulated by androgens and CaMKK2 signaling.

Despite altered metabolism being an accepted hallmark of cancer, it is still not completely understood which signaling pathways regulate these processes. Given the central role of androgen receptor (AR) signaling in prostate cancer, we hypothesized that AR could promote prostate cancer cell growth in part through increasing glucose uptake via the expression of distinct glucose transporters. Here, we determined that AR directly increased the expression of SLC2A12, the gene that encodes the glucose transporter GLUT12. In support of these findings, gene signatures of AR activity correlated with SLC2A12 expression in multiple clinical cohorts. Functionally, GLUT12 was required for maximal androgen-mediated glucose uptake and cell growth in LNCaP and VCaP cells. Knockdown of GLUT12 also decreased the growth of C4-2, 22Rv1 and AR-negative PC-3 cells. This latter observation corresponded with a significant reduction in glucose uptake, indicating that additional signaling mechanisms could augment GLUT12 function in an AR-independent manner. Interestingly, GLUT12 trafficking to the plasma membrane was modulated by calcium/calmodulin-dependent protein kinase kinase 2 (CaMKK2)-5'-AMP-activated protein kinase (AMPK) signaling, a pathway we previously demonstrated to be a downstream effector of AR. Inhibition of CaMKK2-AMPK signaling decreased GLUT12 translocation to the plasma membrane by inhibiting the phosphorylation of TBC1D4, a known regulator of glucose transport. Further, AR increased TBC1D4 expression. Correspondingly, expression of TBC1D4 correlated with AR activity in prostate cancer patient samples. Taken together, these data demonstrate that prostate cancer cells can increase the functional levels of GLUT12 through multiple mechanisms to promote glucose uptake and subsequent cell growth.