Secreted Frizzled-related protein-1 is a negative regulator of androgen receptor activity in prostate cancer

Combination therapies with Wnt signaling inhibition: A better choice for prostate cancer treatment

The intractability and high mortality rate of castration-resistant prostate cancer (CRPC) remain the most challenging problems in the field of prostate cancer (PCa). Emerging evidence has shown that the dysregulation of Wnt signaling pathways, which are highly conserved cascades that regulate embryonic development and maintain tissue homeostasis, is involved in various stages of PCa occurrence and progression. In this review, we systemically discuss the mechanisms by which the androgen receptor (AR) signaling pathway and Wnt signaling pathways participate in the occurrence of PCa and its progression to CRPC. Specifically, we elaborate on how Wnt signaling pathways induce the malignant transformation of prostate cells, promote the malignant progression of PCa and establish an immunosuppressive prostate tumor microenvironment through interaction with the AR pathway or in an AR-independent manner. We also discuss how Wnt signaling pathways enhances the stemness characteristics of prostate cancer stem cells (PCSCs) to induce the occurrence and metastasis of CPPC. Additionally, we discuss the latest progress in the use of different types of drugs that inhibit the Wnt signaling pathways in the treatment of PCa. We believe that the combination of Wnt signaling-based drugs with endocrine and other therapies is necessary and may enhance the clinical efficacy in the treatment of all types of PCa.

Novel treatment from a botanical formulation Si-Miao-Yong-an decoction inhibits vasa vasorum angiogenesis and stabilizes atherosclerosis plaques via the Wnt1/β-catenin signalling pathway

CONTEXT

Si-Miao-Yong-An (SMYA) has been widely used for the clinical treatment of atherosclerosis (AS). Yet, its complete mechanism of action is not fully understood.

OBJECTIVE

To investigate the mechanism by which SMYA stabilizes AS plaques from the perspective of inhibiting vasa vasorum (VV) angiogenesis.

MATERIALS AND METHODS

We used male ApoE-/- mice to establish an AS model. The mice were divided into model, SMYA (11.7 mg/kg/d), and simvastatin (SVTT) (2.6 mg/kg/d) groups. Mice were given SMYA or SVTT by daily gavage for 8 weeks. HE staining, immunofluorescence double-labelling staining, and immunohistochemical staining were used to observe the pathological changes in the plaques. Finally, the protein and mRNA expression levels of the Wnt1/β-catenin signalling pathway were detected by Western blot and qRT-PCR, respectively.

RESULTS

SMYA significantly attenuated cholesterol crystallization, and lipid accumulation in AS plaques, resulting in smaller plaque size (0.25 mm2 vs. 0.46 mm2), and lowering ratio of plaque to lumen area (20.04% vs. 38.33%) and VV density (50.64/mm2 vs. 98.02/mm2). Meanwhile, SMYA suppressed both the positive area percentage of Wnt1 (2.53 vs. 3.56), β-catenin (3.33 vs. 5.65) and Cyclin D1 (2.10 vs. 3.27) proteins in the aortic root plaques, and mRNA expression of Wnt1 (1.38 vs. 2.09), β-catenin (2.05 vs. 3.25) and Cyclin D1 (1.39 vs. 2.57).

DISCUSSION AND CONCLUSIONS

SMYA has a protective effect against AS, which may be related to its anti-VV angiogenesis in plaques, suggesting that SMYA has the potential as a novel botanical formulation in the treatment of AS.

Wnt Signaling and Therapeutic Resistance in Castration-Resistant Prostate Cancer

Purpose of Review

Castration-resistant prostate cancer (CRPC) is a lethal form of prostate cancer (PCa) due to the development of resistance to androgen deprivation therapy and anti-androgens. Here, we review the emerging role of Wnt signaling in therapeutic resistance of CRPC.

Recent Findings

Convincing evidence have accumulated that Wnt signaling is aberrantly activated through genomic alterations and autocrine and paracrine augmentations. Wnt signaling plays a critical role in a subset of CRPC and in resistance to anti-androgen therapies. Wnt signaling navigates CRPC through PCa heterogeneity, neuroendocrine differentiation, DNA repair, PCa stem cell maintenance, epithelial-mesenchymal-transition and metastasis, and immune evasion.

Summary

Components of Wnt signaling can be harnessed for inhibiting PCa growth and metastasis and for developing novel therapeutic strategies to manage metastatic CRPC. There are many Wnt pathway-based potential drugs in different stages of pre-clinical development and clinical trials but so far, no Wnt signaling-specific drug has been approved by FDA for clinical use in CRPC.

Exploring the Wnt Pathway as a Therapeutic Target for Prostate Cancer

Aberrant activation of the Wnt pathway is emerging as a frequent event during prostate cancer that can facilitate tumor formation, progression, and therapeutic resistance. Recent discoveries indicate that targeting the Wnt pathway to treat prostate cancer may be efficacious. However, the functional consequence of activating the Wnt pathway during the different stages of prostate cancer progression remains unclear. Preclinical work investigating the efficacy of targeting Wnt signaling for the treatment of prostate cancer, both in primary and metastatic lesions, and improving our molecular understanding of treatment responses is crucial to identifying effective treatment strategies and biomarkers that help guide treatment decisions and improve patient care. In this review, we outline the type of genetic alterations that lead to activated Wnt signaling in prostate cancer, highlight the range of laboratory models used to study the role of Wnt genetic drivers in prostate cancer, and discuss new mechanistic insights into how the Wnt cascade facilitates prostate cancer growth, metastasis, and drug resistance.

Amniotic stromal stem cell-loaded hydrogel repairs cardiac tissue in infarcted rat hearts via paracrine mediators

The use of stem cells to repair the heart after a myocardial infarction (MI) remains promising, yet clinical trials over the past 20 years suggest that cells fail to integrate into the native tissue, resulting in limited improvements in cardiac function. Here, we demonstrate the cardioprotective potential of a composite inserting human amniotic stromal mesenchymal stem cells (ASMCs) in a chitosan and hyaluronic acid (C/HA) based hydrogel in a rat MI model. Mechanical characterization of the C/HA platform indicated a swift elastic conversion at 40°C and a rapid sol-gel transition time at 37°C. Cell viability assay presented active and proliferating AMSCs in the C/HA. The ASMCs + C/HA injected composite significantly increased left ventricular ejection fraction, fractional shortening, and neovessel formation. The encapsulated AMSCs were abundantly detected in the infarcted myocardium 6 weeks post-administration and co-expressed cardiac proteins and notably proliferative markers. Proteomic profiling revealed that extracellular vesicles released from hypoxia preconditioned ASMCs contained proteins involved in cytoprotection, angiogenesis, cardiac differentiation and non-canonical Wnt-signaling. Independent activation of non-canonical Wnt-signaling pathways in ASMCs induced cardiogenesis. Despite a low injected cellular density at baseline, the encapsulated AMSCs were abundantly retained and increased cardiac function. Furthermore, the C/HA hydrogel provided an active milieu for the AMSCs to proliferate, co-express cardiac proteins, and induce new vessel formation. Hence, this novel composite of AMSCs + C/HA scaffold is a conceivable candidate that could restore cardiac function and reduce remodeling.

Secreted Frizzled-Related Protein 1 Promotes Odontoblastic Differentiation and Reparative Dentin Formation in Dental Pulp Cells

Direct pulp capping is an effective treatment for preserving dental pulp against carious or traumatic pulp exposure via the formation of protective reparative dentin by odontoblast-like cells. Reparative dentin formation can be stimulated by several signaling molecules; therefore, we investigated the effects of secreted frizzled-related protein (SFRP) 1 that was reported to be strongly expressed in odontoblasts of newborn molar tooth germs on odontoblastic differentiation and reparative dentin formation. In developing rat incisors, cells in the dental pulp, cervical loop, and inner enamel epithelium, as well as ameloblasts and preodontoblasts, weakly expressed Sfrp1; however, Sfrp1 was strongly expressed in mature odontoblasts. Human dental pulp cells (hDPCs) showed stronger expression of SFRP1 compared with periodontal ligament cells and gingival cells. SFRP1 knockdown in hDPCs abolished calcium chloride-induced mineralized nodule formation and odontoblast-related gene expression and decreased BMP-2 gene expression. Conversely, SFRP1 stimulation enhanced nodule formation and expression of BMP-2. Direct pulp capping treatment with SFRP1 induced the formation of a considerable amount of reparative dentin that has a structure similar to primary dentin. Our results indicate that SFRP1 is crucial for dentinogenesis and is important in promoting reparative dentin formation in response to injury.

Increased expression of secreted frizzled related protein 1 (SFRP1) predicts ampullary adenocarcinoma recurrence

Ampullary adenocarcinoma is a rare gastrointestinal cancer in which WNT signalling dysregulation has been previously reported. Secreted frizzled related protein 1 (SFRP1) is one of the extracellular ligands of WNT signalling. We performed bioinformatics analyses of SFRP1 expression in human cancer. Microarray analysis of SFRP1 in periampullary adenocarcinoma was obtained from the Gene Expression Omnibus GSE39409 dataset. SFRP1 expression in ampullary adenocarcinoma was detected by immunohistochemistry staining and correlated with patients’ clinical outcomes. Our results showed that SFRP1 expression had different clinical applications in all types of human cancer. No detected alteration of SFPR1 gene and SFRP1 expression in ampullary adenocarcinoma was lower than that in other periampullary adenocarcinomas. However, high expression levels of SFRP1 protein were correlated with cancer recurrence, peritoneal carcinomatosis and poor patient prognosis. Gene set enrichment analysis showed downregulation of multiple WNT-related genes in primary culture cells from ampullary adenocarcinoma, but SFRP1 expression was increased. We found an interaction between WNT, bone morphogenetic protein and hedgehog signalling with SFRP1. Furthermore, a high expression of SFRP1 predicted poor prognosis for ampullary adenocarcinoma patients. Because it is a multifunctional protein, SFRP1 targeting serves as a potential therapy for ampullary adenocarcinoma patients.

SFRP1 increases TMPRSS2-ERG expression promoting neoplastic features in prostate cancer in vitro and in vivo

Background

Prostate cancer (PCa) is the second cause of cancer related death in North American men. Androgens play an important role in its progression by regulating the expression of several genes including fusion ones that results from structural chromosome rearrangements. TMPRSS2-ERG is a fusion gene commonly observed in over 50% of PCa tumors, and its expression can be transcriptionally regulated by the androgen receptor (AR) given its androgen responsive elements. TMPRSS2-ERG could be involved in epithelial–mesenchymal transition (EMT) during tumor development. ERG has been reported as a key transcriptional factor in the AR-ERG-WNT network where five SFRP proteins, structurally similar to WNT ligands and considered to be WNT pathway antagonists, can regulate signaling in the extracellular space  by binding to WNT proteins or Frizzled receptors. It has been shown that over-expression of SFRP1 protein can regulate the transcriptional activity of AR and inhibits the formation of colonies in LNCaP cells. However, the effect of SFRP1 has been controversial since differential effects have been observed depending on its concentration and tissue location. In this study, we explored the role of exogenous SFRP1 protein in cells expressing the TMPRSS2-ERG fusion.

Methods

To evaluate the effect of exogenous SFRP1 protein on PCa cells expressing TMPRSS2-ERG, we performed in silico analysis from TCGA cohort, expression assays by RT-qPCR and Western blot, cell viability and cell cycle measurements by cytometry, migration and invasion assays by xCELLigance system and murine xenografts.

Results

We demonstrated that SFRP1 protein increased ERG expression by promoting cellular migration in vitro and increasing tumor growth in vivo in PCa cells with the TMPRSS2-ERG fusion.

Conclusions

These results suggest the possible role of exogenous SFRP1 protein as a modulator of AR-ERG-WNT signaling network in cells positive to TMPRSS2-ERG. Further, investigation is needed to determine if SFRP1 protein could be a target in against this type of PCa.

Epigenetics of SFRP1: The Dual Roles in Human Cancers

Secreted frizzled-related protein 1 (SFRP1) is a gene that belongs to the secreted glycoprotein SFRP family. SFRP1 has been classified as a tumor suppressor gene due to the loss of expression in various human cancers, which is mainly attributed by epigenetic inactivation via DNA methylation or transcriptional silencing by microRNAs. Epigenetic silencing of SFRP1 may cause dysregulation of cell proliferation, migration, and invasion, which lead to cancer cells formation, disease progression, poor prognosis, and treatment resistance. Hence, restoration of SFRP1 expression via demethylating drugs or over-expression experiments opens the possibility for new cancer therapy approach. While the role of SFRP1 as a tumor suppressor gene is well-established, some studies also reported the possible oncogenic properties of SFRP1 in cancers. In this review, we discussed in great detail the dual roles of SFRP1 in cancers-as tumor suppressor and tumor promoter. The epigenetic regulation of SFRP1 expression will also be underscored with additional emphasis on the potentials of SFRP1 in modulating responses toward chemotherapeutic and epigenetic-modifying drugs, which may encourage the development of novel drugs for cancer treatment. We also present findings from clinical trials and patents involving SFRP1 to illustrate its clinical utility, extensiveness of each research area, and progression toward commercialization. Lastly, this review provides directions for future research to advance SFRP1 as a promising cancer biomarker.

Role of Secreted Frizzled-Related Protein 1 in Early Mammary Gland Tumorigenesis and Its Regulation in Breast Microenvironment

In mice, the lack of secreted frizzled-related protein 1 (SFRP1) is responsible for mammogenesis and hyperplasia, while, in bovines, its overexpression is associated with post-lactational mammary gland involution. Interestingly, there are no reports dealing with the role of SFRP1 in female involution. However, SFRP1 dysregulation is largely associated with human tumorigenesis in the literature. Indeed, the lack of SFRP1 is associated with both tumor development and patient prognosis. Considering the increased risk of breast tumor development associated with incomplete mammary gland involution, it is crucial to demystify the "grey zone" between physiological age-related involution and tumorigenesis. In this review, we explore the functions of SFRP1 involved in the breast involution processes to understand the perturbations driven by the disappearance of SFRP1 in mammary tissue. Moreover, we question the presence of recurrent microcalcifications identified by mammography. In bone metastases from prostate primary tumor, overexpression of SFRP1 results in an osteolytic response of the tumor cells. Hence, we explore the hypothesis of an osteoblastic differentiation of mammary cells induced by the lack of SFRP1 during lobular involution, resulting in a new accumulation of hydroxyapatite crystals in the breast tissue.

Heterogeneous cancer-associated fibroblast population potentiates neuroendocrine differentiation and castrate resistance in a CD105-dependent manner

Heterogeneous prostatic carcinoma associated fibroblasts (CAF) contribute to tumor progression and resistance to androgen signaling deprivation therapy (ADT). CAF subjected to extended passaging, compared to low passage CAF, were found to lose tumor expansion potential and heterogeneity. Cell surface endoglin (CD105), known to be expressed on proliferative endothelia and mesenchymal stem cells, was diminished in high passage CAF. RNA-sequencing revealed SFRP1 to be distinctly expressed by tumor-inductive CAF, which was further demonstrated to occur in a CD105-dependent manner. Moreover, ADT resulted in further expansion of the CD105⁺ fibroblastic population and downstream SFRP1 in 3-dimensional cultures and patient derived xenograft tissues. In patients, CD105⁺ fibroblasts were found to circumscribe epithelia with neuroendocrine differentiation. CAF-derived SFRP1, driven by CD105 signaling, was necessary and sufficient to induce prostate cancer neuroendocrine differentiation in a paracrine manner. A partially humanized CD105 neutralizing antibody, TRC105, inhibited fibroblastic SFRP1 expression and epithelial neuroendocrine differentiation. In a novel synthetic lethality paradigm, we found that simultaneously targeting the epithelia and its microenvironment with ADT and TRC105, respectively, reduced castrate resistant tumor progression, in a model where either ADT or TRC105 alone had little effect.

Cross talk between androgen and Wnt signaling potentially contributes to age-related skeletal muscle atrophy in rats

We sought to determine whether age-related gastrocnemius muscle mass loss was associated with parallel decrements in androgen receptor (AR) or select Wnt signaling markers. To test this hypothesis, serum-free and total testosterone (TEST) and gastrocnemius AR and Wnt signaling markers were analyzed in male Fischer 344 rats that were 3, 6, 12, 18, and 24 mo (mo) old ( n = 9 per group). Free and total TEST was greatest in 6 mo rats, and AR protein and Wnt5 protein levels linearly declined with aging. There were associations between Wnt5 protein levels and relative gastrocnemius mass ( r = 0.395, P = 0.007) as well as AR and Wnt5 protein levels (r = 0.670, P < 0.001). We next tested the hypothesis that Wnt5 affects muscle fiber size by treating C2C12-derived myotubes with lower (75 ng/ml) and higher (150 ng/ml) concentrations of recombinant Wnt5a protein. Both treatments increased myotube size ( P < 0.05) suggesting this ligand may affect muscle fiber size in vivo. We next tested if Wnt5a protein levels were androgen-modulated by examining 10-mo-old male Fischer 344 rats ( n = 10-11 per group) that were orchiectomized and treated with testosterone-enanthate (TEST-E); trenbolone enanthate (TREN), a nonaromatizable synthetic testosterone analogue; or a vehicle (ORX only) for 4 wk. Interestingly, TEST-E and TREN treatments increased Wnt5a protein in the androgen-sensitive levator ani/bulbocavernosus muscle compared with ORX only ( P < 0.05). To summarize, aromatizable and nonaromatizable androgens increase Wnt5a protein expression in skeletal muscle, age-related decrements in muscle AR may contribute Wnt5a protein decrements, and our in vitro data imply this mechanism may contribute to age-related muscle loss. NEW & NOTEWORTHY Results from this study demonstrate androgen and Wnt5 protein expression decrease with aging, and this may be a mechanism involved with age-related muscle loss.

Arsenic trioxide inhibits viability and induces apoptosis through reactivating the Wnt inhibitor secreted frizzled related protein-1 in prostate cancer cells

Background

Growing evidence suggests that arsenic trioxide (As₂O₃) induces apoptosis and inhibits tumor cell growth in prostate cancer (PCa), although details of the mechanism are still inconclusive. We investigated the antitumor effect of As₂O₃ in human PCa cell lines LNCaP and PC3 and the underlying mechanisms by focusing on the Wnt signaling pathway.

Methods

The effect of As₂O₃ on the viability and apoptosis of PCa cells was investigated by cholecystokinin-8 and flow cytometry. The expression of the related proteins in the Wnt signaling pathway and the downstream target genes of the Wnt signaling pathway was examined by Western blot and quantitative real-time PCR assay. The methylation status of the SFRP1 gene promoter was assessed by bisulfite sequencing.

Results

As₂O₃ inhibited the viability of PCa cells and induced apoptosis of PCa cells in a dose-dependent manner. The protein level of phosphoglycogen synthase kinase-3β was upregulated, whereas the protein level of β-catenin and the mRNA levels of c-MYC, MMP-7, and COX-2 were downregulated in a dose-dependent manner in PCa cells treated with As₂O₃. In addition, As₂O₃ upregulated the protein and mRNA levels of secreted frizzled related protein-1, and increased the demethylation of the SFRP1 gene promoter.

Conclusion

Our results suggest that As₂O₃ may inhibit cell viability and induce apoptosis through reactivating the Wnt inhibitor secreted frizzled related protein-1 in both androgen-dependent and -independent human PCa.

Prognostic and predictive biomarkers in prostate cancer

Prostate cancer (PCa) is one of the leading causes of cancer death among males, especially in more developed countries. Diagnosis is often achieved at an early stage of the disease with prostate biopsy, following a screening test showing elevated serum levels of prostate-specific antigen or a positive digital rectal examination. Early detection of PCa has led to a substantial decline in the number of metastatic patients. However, the prostate-specific antigen screening test has proved to be a double-edged sword so far, as it also accounts for PCa overdiagnosis. Due to the variability of PCa features, accurate prognosis of PCa patients is very important for determining treatment options. Therefore, this review focuses on the most promising prognostic and predictive biomarkers in PCa, which are likely to play a pivotal role, alone or in panels, in the personalized medicine era that has recently emerged.

Immunohistochemical expression of SFRP1 and SFRP3 proteins in normal and malignant reproductive tissues of rats and humans

Secreted frizzled-related proteins 1 and 3 (SFRP1 and SFRP3) act as Wnt signaling pathway antagonists and play an important role in embryonic development and carcinogenesis. The aim of the present study was to analyze immunohistochemically the distribution of 2 SFRP family proteins, SFRP1 and SFRP3, in an experimental rat model, in normal and intrauterine growth-restricted (IUGR) human placentas, and in a subset of the corresponding human trophoblastic tumors (pure choriocarcinomas and mixed germ cell tumors with choriocarcinoma component). In rats, expression of both SFRP1 and SFRP3 was pronounced in the perimetrium and myometrium, whereas decidual cells showed only occasional positive cytoplasmic staining. The most prominent expression of both proteins was found in blood vessel endothelial cells. Stereological variable of volume density (Vv, mm) showed statistically higher expression of SFRP1 and SFRP3 in human IUGR placentas than in normal pregnancy placentas (P<0.0001). Compared with adjacent normal/benign tissues, reduced expression of SFRP1 and SFRP3 was observed in human trophoblastic tumors (58.5% and 31.25%, respectively), although none of the examined tumors exhibited complete loss of either protein. Our study indicates that increased expression of both SFRP1 and SFRP3 may contribute to the pathogenesis of IUGR placental dysfunction, whereas the loss of these proteins may be involved in the development of human trophoblastic tumors.

Diagnostic value of SFRP1 as a favorable predictive and prognostic biomarker in patients with prostate cancer

Growing genetic and molecular biological evidence suggests that the disruption of balance between Secreted Frizzled-Related Protein-1 (SFRP1) and β-catenin plays an important role in the initiation and development of multiple cancers. The aim of this study was to examine whether the expression of SFRP1 and β-catenin is associated with the clinical-pathologic features of patients with prostate cancer (PCa), and to evaluate their potential roles as predictive and prognostic biomarkers. In this study, a total of 61 patients with PCa and 10 patients with benign prostatic hyperplasia were included, and we showed that the expression of SFRP1 and β-catenin was correlated with the Gleason score, survival rate and response for endocrine therapy of PCa. The survival rates of PCa patients with low SFRP1 expression (P = 0.016) or high β-catenin expression (P = 0.004) were significantly poorer. A negative correlation (r = -0.275, P = 0.032) between SFRP1 and β-catenin was observed by Chi-square test. Multivariate analysis suggested that SFRP1 (hazard ratio, 0.429; 95% confidence intervals, 0.227–0.812; P = 0.009) may serve as an independent predictive and prognostic factor for PCa. We also showed that the protein and mRNA levels of SFRP1 in androgen-dependent PCa cell line LNCaP were significantly higher than those in androgen-independent PCa cell lines DU145 and PC3. However, the protein level of β-catenin in LNCaP cells was significantly lower than that in DU145 and PC3 cells, and no significant difference of β-catenin mRNA level was observed in LNCaP, DU145 and PC3 cells. Bisulfite sequencing PCR assay revealed significantly lower methylation level of SFRP1 promoter in LNCaP cells than that in DU145 and PC3 cells. Taken together, these findings suggest that SFRP1, which expression inversely correlates with that of β-catenin, is a favorable predictive and prognostic biomarker.

Engineered repressors are potent inhibitors of androgen receptor activity

Prostate cancer growth is dependent upon the Androgen Receptor (AR) pathway, hence therapies for this disease often target this signalling axis. Such therapies are successful in the majority of patients but invariably fail after a median of 2 years and tumours progress to a castrate resistant stage (CRPC). Much evidence exists to suggest that the AR remains key to CRPC growth and hence remains a valid therapeutic target. Here we describe a novel method to inhibit AR activity, consisting of an interaction motif, that binds to the AR ligand-binding domain, fused to repression domains. These ‘engineered repressors’ are potent inhibitors of AR activity and prostate cancer cell growth and importantly inhibit the AR under circumstances in which conventional therapies would be predicted to fail, such as AR mutation and altered cofactor levels.

C5aR is frequently expressed in metastatic renal cell carcinoma and plays a crucial role in cell invasion via the ERK and PI3 kinase pathways

The anaphylatoxin C5a is a chemoattractant for leukocyte migration via the C5a receptor (C5aR). We recently reported that C5aR was aberrantly expressed in a wide variety of human related cancers, while it also promotes cancer cell invasion by C5a stimulation. However, the biological significance of C5aR expression in renal cell carcinoma (RCC) has not yet been clarified. In the present study, we aimed to elucidate the biological role of C5aR in RCC progression. Clinical RCC specimens were analyzed for C5aR expression and its relationship with baseline demographic data and clinicopathological parameters was analyzed. Moreover, renal carcinoma Renca cells stably expressing C5aR were generated and used to assess the effects of C5a-C5aR axis activation on various cellular phenomena in culture. Immunohistochemistry revealed that 96.7% of the metastatic RCCs (mRCCs) showed C5aR expression, whereas only 50.5% of the non-metastatic RCCs expressed C5aR (P<0.001). Although C5a stimulation did not significantly alter anoikis of C5aR‑expressing Renca cells, C5a elicited cell morphological change and scattering of those cells accompanied with dynamic actin rearrangement, which was not observed in the Renca cells harboring the empty vector only. Moreover, C5a triggered ERK and PI3K‑dependent invasion of the C5aR-expressing renal carcinoma cells. These results are consistent with the idea that the C5a-C5aR axis plays a crucial role in renal carcinoma cell invasion, which may be one of the key steps for RCC metastasis. The present study provides proof‑of‑concept that the C5a-C5aR axis may be a useful therapeutic target for preventing RCC progression.

Wnt signaling in castration-resistant prostate cancer: implications for therapy

Increasing evidence has indicated that Wnt signaling plays complex roles in castration resistant prostate cancer (CRPC). Although not all data were consistent, β-catenin nuclear localization and its co-localization with androgen receptor (AR) were more frequently observed in CRPC compared to hormone naïve prostate cancer. This direct interaction between AR and β-catenin seemed to elicit a specific expression of a set of target genes in low androgen conditions in CRPC. Paracrine Wnt signaling also was shown to aid resistance to chemotherapy and androgen deprivation therapy. Results from the next generation sequencing studies (i.e. RNA-seq and whole exosome sequcing) of CRPC specimens have identified the Wnt pathway as one of the top signaling pathways with significant genomic alterations in CRPC, whereas, Wnt pathway alterations were virtually absent in hormone naïve primary prostate cancer. Furthermore, Wnt signaling has been suggested to play an important role in cancer stem cell functions in prostate cancer recurrence and resistance to androgen deprivation therapy. Therefore, in this review we have summarized existing knowledge regarding potential roles of Wnt signaling in CRPC and underline Wnt signaling as a potential therapeutic target for CRPC. Further understanding of Wnt signaling in castration resistance may eventually contribute new insights into possible treatment options for this incurable disease.

Ligand-dependent stabilization of androgen receptor in a novel mouse ST38c Sertoli cell line

Mature Sertoli cells (SC) are critical mediators of androgen regulation of spermatogenesis, via the androgen receptor (AR) signaling. Available immortalized SC lines loose AR expression or androgen responsiveness, hampering the study of endogenous AR regulation in SC. We have established and characterized a novel clonal mouse immortalized SC line, ST38c. These cells express some SC specific genes (sox9, wt1, tjp1, clu, abp, inhbb), but not fshr, yet more importantly, maintain substantial expression of endogenous AR as determined by PCR, immunocytochemistry, testosterone binding assays and Western blots. Microarrays allowed identification of some (146) but not all (rhox5, spinlw1), androgen-dependent, SC expressed target genes. Quantitative Real-Time PCR validated regulation of five up-regulated and two down-regulated genes. We show that AR undergoes androgen-dependent transcriptional activation as well as agonist-dependent posttranslational stabilization in ST38c cells. This cell line constitutes a useful experimental tool for future investigations on the molecular and cellular mechanisms of androgen receptor signaling in SC function.

Downregulation of Dickkopf-3 disrupts prostate acinar morphogenesis through TGF-β/Smad signaling

Loss of tissue organization is a hallmark of the early stages of cancer, and there is considerable interest in proteins that maintain normal tissue architecture. Prostate epithelial cells cultured in Matrigel form three-dimensional acini that mimic aspects of prostate gland development. The organization of these structures requires the tumor suppressor Dickkopf-3 (Dkk-3), a divergent member of the Dkk family of secreted Wnt signaling antagonists that is frequently downregulated in prostate cancer. To gain further insight into the function of Dkk-3 in the prostate, we compared the prostates of Dkk3 null mice with those of control littermates. We found increased proliferation of prostate epithelial cells in the mutant mice and changes in prostate tissue organization. Consistent with these observations, cell proliferation was elevated in acini formed by human prostate epithelial cells stably silenced for Dkk-3. Silencing of Dkk-3 increased TGF-β/Smad signaling and inhibitors of TGF-β/Smad signaling rescued the defective acinar phenotype caused by loss of Dkk-3. These findings suggest that Dkk-3 maintains the structural integrity of the prostate gland by limiting TGF-β/Smad signaling.

Gene expression and epigenetic discovery screen reveal methylation of SFRP2 in prostate cancer

Aberrant activation of Wnts is common in human cancers, including prostate. Hypermethylation associated transcriptional silencing of Wnt antagonist genes SFRPs (Secreted Frizzled-Related Proteins) is a frequent oncogenic event. The significance of this is not known in prostate cancer. The objectives of our study were to (i) profile Wnt signaling related gene expression and (ii) investigate methylation of Wnt antagonist genes in prostate cancer. Using TaqMan Low Density Arrays, we identified 15 Wnt signaling related genes with significantly altered expression in prostate cancer; the majority of which were upregulated in tumors. Notably, histologically benign tissue from men with prostate cancer appeared more similar to tumor (r = 0.76) than to benign prostatic hyperplasia (BPH; r = 0.57, p < 0.001). Overall, the expression profile was highly similar between tumors of high (≥ 7) and low (≤ 6) Gleason scores. Pharmacological demethylation of PC-3 cells with 5-Aza-CdR reactivated 39 genes (≥ 2-fold); 40% of which inhibit Wnt signaling. Methylation frequencies in prostate cancer were 10% (2/20) (SFRP1), 64.86% (48/74) (SFRP2), 0% (0/20) (SFRP4) and 60% (12/20) (SFRP5). SFRP2 methylation was detected at significantly lower frequencies in high-grade prostatic intraepithelial neoplasia (HGPIN; 30%, (6/20), p = 0.0096), tumor adjacent benign areas (8.82%, (7/69), p < 0.0001) and BPH (11.43% (4/35), p < 0.0001). The quantitative level of SFRP2 methylation (normalized index of methylation) was also significantly higher in tumors (116) than in the other samples (HGPIN = 7.45, HB = 0.47, and BPH = 0.12). We show that SFRP2 hypermethylation is a common event in prostate cancer. SFRP2 methylation in combination with other epigenetic markers may be a useful biomarker of prostate cancer.

Wnt/β-catenin signalling in prostate cancer

The Wnts are secreted cysteine-rich glycoproteins that have important roles in the developing embryo as well as in tissue homeostasis in adults. Dysregulation of Wnt signalling can lead to several types of cancer, including prostate cancer. A hallmark of the signalling pathway is the stabilization of the transcriptional co-activator β-catenin, which not only regulates expression of many genes implicated in cancer but is also an essential component of cadherin cell adhesion complexes. β-catenin regulates gene expression by binding members of the T-cell-specific transcription factor/lymphoid enhancer-binding factor 1 (TCF/LEF-1) family of transcription factors. In addition, β-catenin associates with the androgen receptor, a key regulator of prostate growth that drives prostate cancer progression. Wnt/β-catenin signalling can be controlled by secreted Wnt antagonists, many of which are downregulated in cancer. Activation of the Wnt/β-catenin pathway has effects on prostate cell proliferation, differentiation and the epithelial-mesenchymal transition, which is thought to regulate the invasive behaviour of tumour cells. However, whether targeting Wnt/β-catenin signalling is a good therapeutic option for prostate cancer remains unclear.

Clinical significance of sFRP1 protein expression in pancreatic ductal adenocarcinoma

AIM: To detect the expression of secreted frizzled-related protein 1 (sFRP1) protein in different pancreatic tissues (normal pancreatic duct, NP; pancreatic ductal adenocarcinoma, PDAC; pancreatic intraepithelial neoplasia, PanIN; and intraductal papillary mucinous neoplasm, IPMN) and evaluate its significance in the carcinogenesis of PDAC.

METHODS: Immunohistochemical detection of sFRP1 protein was performed in 21 foci of NP, 73 foci of PanIN-1, 29 foci of PanIN-2, 16 foci of PanIN-3, 20 cases of IPMN-adenoma (IPMA), 13 cases of IPMN-borderline (IPMB), 19 cases of IPMN-carcinoma (IPMC), and 50 cases of PDAC. The correlation between sFRP1 expression and clinicopathologic characteristics of PDAC was analyzed.

RESULTS: Immunohistochemical score (IHCS) of sFRP1 expression escalated with the severity of tissue atypia along the progressive multistage: NP→PanIN-1→PanIN-2, PanIN-3, PDAC or NP→IPMA, IPMB→IPMC, PDAC. sFRP1 expression was significantly associated with tumor differentiation and neural infiltration.

CONCLUSION: sFRP-1 expression enhancement is an early event in the carcinogenesis of PDAC, representing an important molecular characteristic of neural infiltration.

The SRA protein UHRF1 promotes epigenetic crosstalks and is involved in prostate cancer progression

Epigenetic silencing of tumour suppressor genes is an important mechanism involved in cell transformation and tumour progression. The Set and RING-finger-associated domain-containing protein UHRF1 might be an important link between different epigenetic pathways. Here, we report that UHRF1 is frequently overexpressed in human prostate tumours and has an important role in prostate cancer pathogenesis and progression. Analysis of human prostate cancer samples by microarrays and immunohistochemistry showed increased expression of UHRF1 in about half of the cases. Moreover, UHRF1 expression was associated with reduced overall survival after prostatectomy in patients with organ-confined prostate tumours (P < 0.0001). UHRF1 expression was negatively correlated with several tumour suppressor genes and positively with the histone methyltransferase (HMT) EZH2 both in prostate tumours and cell lines. UHRF1 knockdown reduced proliferation, clonogenic capability and anchorage-independent growth of prostate cancer cells. Depletion of UHRF1 resulted in reactivation of several tumour suppressor genes. Gene reactivation upon UHRF1 depletion was associated with changes in histone H3K9 methylation, acetylation and DNA methylation, and impaired binding of the H3K9 HMT Suv39H1 to the promoter of silenced genes. Co-immunoprecipitation experiments showed direct interaction between UHRF1 and Suv39H1. Our data support the notion that UHRF1, along with Suv39H1 and DNA methyltransferases, contributes to epigenetic gene silencing in prostate tumours. This could represent a parallel and convergent pathway to the H3K27 methylation catalyzed by EZH2 to synergistically promote inactivation of tumour suppressor genes. Deregulated expression of UHRF1 is involved in the prostate cancer pathogenesis and might represent a useful marker to distinguish indolent cancer from those at high risk of lethal progression.

Elevated level of Wnt5a protein in localized prostate cancer tissue is associated with better outcome

BACKGROUND

Wnt5a is a non-canonical secreted glycoprotein of the Wnt family that plays an important role in cancer development and progression. Previous studies report that Wnt5a is upregulated in prostate cancer and suggested that Wnt5a affects migration and invasion of prostate tumor cell. This study aimed to evaluate the prognostic value of Wnt5a protein expression in prostate cancer tissue and its potential to predict outcome after radical prostatectomy in patients with localized prostate cancer.

METHODOLOGY AND RESULTS

Immunohistochemical analysis of a tissue microarray containing prostate specimens of 503 patients with localized prostate cancer showed significantly higher Wnt5a protein expression in cancer compared to benign cores from the same patients (p<0.0001). Patients with high expression of Wnt5a protein had significantly better outcome in terms of time to biochemical recurrence compared to patients with low expression levels (p = 0.001, 95%CI 1.361-3.570, Hazard's ratio 2.204). A combination of high Wnt5a expression with low levels of Ki-67 or androgen receptor expression had even better outcome compared to all other groups. Furthermore, we found that Wnt5a expression significantly correlated with VEGF and with Ki-67 and androgen receptor expression, although not highly significant. In vitro, we demonstrated that recombinant Wnt5a decreased invasion of 22Rv1 and DU145 cells and that siRNA knockdown of endogenous Wnt5a protein led to increased invasion of 22Rv1 and LNCaP cells.

CONCLUSION

We demonstrate that preserved overexpression of Wnt5a protein in patients with localized prostate cancer predicts a favorable outcome after surgery. This finding together with our in vitro data demonstrating the ability of Wnt5a to impair the invasive properties of prostate cancer cells, suggests a tumor suppressing effect of Wnt5a in localized prostate cancer. These results indicate that Wnt5a can be used as a predictive marker and that it also is a plausible therapeutic target for treatment of localized prostate cancer.

Wnt and SHH in prostate cancer: trouble mongers occupy the TRAIL towards apoptosis

Prostate cancer is a serious molecular disorder that arises because of reduction in tumour suppressors and overexpression of oncogenes. The malignant cells survive within the context of a three-dimensional microenvironment in which they are exposed to mechanical and physical cues. These signals are, nonetheless, deregulated through perturbations to mechanotransduction, from the nanoscale level to the tissue level. Increasingly sophisticated interpretations have uncovered significant contributions of signal transduction cascades in governing prostate cancer progression. To dismantle the major determinants that lie beneath disruption of spatiotemporal patterns of activity, crosstalk between various signalling cascades and their opposing and promoting effects on TRAIL-mediated activities cannot be ruled out. It is important to focus on that molecular multiplicity of cancer cells, various phenotypes reflecting expression of a variety of target oncogenes, reversible to irreversible, exclusive, overlapping or linked, coexist and compete with each other. Comprehensive investigations into TRAIL-mediated mitochondrial dynamics will remain a worthwhile area for underlining causes of tumourigenesis and for unravelling interference options.

DNA Methylation and the HOXC6 Paradox in Prostate Cancer

Overexpression of the classical homeobox transcription factor HOXC6 is frequent in prostate cancers and correlates with adverse clinical parameters. Since surprisingly many HOXC6 target genes are downregulated in prostate cancer, it has been posited that oncogenic effects of HOXC6 in prostate cancer may be unmasked by concurrent epigenetic downregulation of target genes exerting tumor suppressive effects. To test this hypothesis, we have studied the expression of three HOXC6 target genes, CNTN1 (encoding a cell adhesion protein), DKK3 and WIF1 (encoding WNT growth factor antagonists) as well as DNA methylation of DKK3 and WIF1. HOXC6 upregulation and association with poor prognosis were confirmed in our tissue series. The three target genes were each significantly downregulated in cancer tissues and expression of each one correlated inversely with that of HOXC6. Cases with lower WIF1 expression showed significantly earlier recurrence (p = 0.021), whereas no statistical significance was reached for CNTN1 and DKK3. Hypermethylation of DKK3 or WIF1 gene promoters was observed in a subset of cancers with downregulated expression, but was often weak. Our data support the hypothesis that HOXC6 target genes exerting tumor-suppressive effects are epigenetically downregulated in prostate cancer, but DNA methylation appears to follow or bolster rather than to cause their transcriptional inactivation.

Wnt signaling in prostate development and carcinogenesis

BACKGROUND

The Wnt signaling pathway is crucial for cell fate decisions, stem cell renewal, regulation of cell proliferation and differentiation. Deregulated Wnt signaling is also implicated in a number of hereditary and degenerative diseases and cancer.

METHODS AND RESULTS

This review highlights the role of the Wnt pathway in the regulation of stem/progenitor cell renewal and prostate gland development and how this signaling is altered in prostate cancer. Recent evidence suggests that Wnt signaling regulates androgen activity in prostate cancer cells, enhances androgen receptor expression and promotes the growth of prostate cancer even after androgen ablation therapy. There is also strong evidence that Wnt signaling is enhanced in androgen-ablation resistant tumors and bone metastases.

CONCLUSIONS

Further study of the modulators of this pathway will be of therapeutic relevance as inhibition of Wnt signaling may have the potential to reduce the self-renewal and aggressive behaviour of prostate cancer while Wnt signaling activation might enhance stem cell activity when tissue regeneration is required.

Distinct roles for Wnt-4 and Wnt-11 during retinoic acid-induced neuronal differentiation

Retinoic acid and Wnt/β-catenin signals play important roles during neuronal differentiation but less is known about noncanonical Wnt signals in this context. We examined retinoic acid and Wnt signaling in two human embryonal carcinoma cell lines, NTERA-2 (clone D1), which undergoes neuronal differentiation in response to retinoic acid, and 2102Ep, which does not. Retinoic acid treatment inhibited β-catenin/Tcf activity in NTERA-2 cells but not in 2102Ep cells. Inhibition occurred downstream of β-catenin but did not involve competition between retinoic acid receptors and β-catenin for binding to p300 or Tcf-4. Ectopic expression of FZD1 partially restored inhibition in 2102Ep cells, suggesting the involvement of Wnt ligands. Retinoic acid treatment of NTERA-2 cells induced the expression of Wnt-4 and Wnt-11, both of which were able to inhibit β-catenin/Tcf activity. Wnt-4 and Wnt-11 were found at cell borders in islands of cells that expressed OCT4 and GFAP and were predominantly negative for Nestin, PAX6, and GATA6. Gene silencing of Wnt-4, but not Wnt-11, reduced retinoic acid downregulation of OCT4 and Nanog and upregulation of PAX6, ASCL1, HOXC5, and NEUROD1, suggesting that Wnt-4 promotes early neuronal differentiation. Gene expression analysis of NTERA-2 cells stably overexpressing Wnt-11 suggested that Wnt-11 potentiates retinoic acid induction of early neurogenesis. Consistent with this, overexpression of Wnt-11 maintained a population of proliferating progenitor cells in cultures treated with retinoic acid for several weeks. These observations highlight the distinct roles of two noncanonical Wnts during the early stages of retinoic acid-induced neuronal differentiation.

The advantages and disadvantages of sfrp1 and sfrp2 expression in pathological events

Secreted Frizzled Related Proteins (Sfrps) are a family of secreted proteins that can bind both to Wnt ligands and Frizzled receptors, thereby modulating the Wnt signalling cascades. Recent studies have shown that Sfrps can also interact with Wnt unrelated molecules such as RANKL, a member of the tumor necrosis factor family, Tolloid metalloproteinases or integrin-fibronectin complexes. Alterations in the levels of Sfrp expression have been recently associated with different pathological conditions, including tumor formation and bone and myocardial disorders. Here, we summarise the evidence that relates Sfrps with these diseases and discuss how the proposed multiple Sfrp interactions with Wnt related and unrelated pathways may explain their implication in such diverse pathologies.

A comprehensive panel of three-dimensional models for studies of prostate cancer growth, invasion and drug responses

Prostate epithelial cells from both normal and cancer tissues, grown in three-dimensional (3D) culture as spheroids, represent promising in vitro models for the study of normal and cancer-relevant patterns of epithelial differentiation. We have developed the most comprehensive panel of miniaturized prostate cell culture models in 3D to date (n = 29), including many non-transformed and most currently available classic prostate cancer (PrCa) cell lines. The purpose of this study was to analyze morphogenetic properties of PrCa models in 3D, to compare phenotypes, gene expression and metabolism between 2D and 3D cultures, and to evaluate their relevance for pre-clinical drug discovery, disease modeling and basic research. Primary and non-transformed prostate epithelial cells, but also several PrCa lines, formed well-differentiated round spheroids. These showed strong cell-cell contacts, epithelial polarization, a hollow lumen and were covered by a complete basal lamina (BL). Most PrCa lines, however, formed large, poorly differentiated spheroids, or aggressively invading structures. In PC-3 and PC-3M cells, well-differentiated spheroids formed, which were then spontaneously transformed into highly invasive cells. These cell lines may have previously undergone an epithelial-to-mesenchymal transition (EMT), which is temporarily suppressed in favor of epithelial maturation by signals from the extracellular matrix (ECM). The induction of lipid and steroid metabolism, epigenetic reprogramming, and ECM remodeling represents a general adaptation to 3D culture, regardless of transformation and phenotype. In contrast, PI3-Kinase, AKT, STAT/interferon and integrin signaling pathways were particularly activated in invasive cells. Specific small molecule inhibitors targeted against PI3-Kinase blocked invasive cell growth more effectively in 3D than in 2D monolayer culture, or the growth of normal cells. Our panel of cell models, spanning a wide spectrum of phenotypic plasticity, supports the investigation of different modes of cell migration and tumor morphologies, and will be useful for predictive testing of anti-cancer and anti-metastatic compounds.

The Sex-determining region Y-box 4 and homeobox C6 transcriptional networks in prostate cancer progression: crosstalk with the Wnt, Notch, and PI3K pathways

The transforming growth factor beta, Hedgehog, Notch, and Wnt signaling pathways all play critical roles in the development and progression of prostate cancer. It is becoming increasingly apparent that these pathways may intersect with developmentally important transcription factors such as the sex-determining region Y-box 4 (SOX4), homeobox C6, enhancer of zeste 2, and ETS-related gene, which are up-regulated in prostate cancers. For example, identification of the downstream targets of SOX4 and homeobox C6 suggests that these factors may cooperate to activate the Notch pathway and the PI3K/AKT pathway, possibly in response to Wnt signals. PI3K/AKT activation likely occurs indirectly via up-regulation of growth factor receptors, while Notch activation is secondary to up-regulation of Notch pathway components. In addition, SOX4 may affect terminal differentiation via regulation of other transcription factors such as NKX3.1 and MLL, and regulation of components of the microRNA pathway such as Dicer and Argonaute 1. The evidence supporting activation of these pathways in prostate cancer progression suggests that combinations of compounds targeting them may be of benefit to patients with aggressive, metastatic disease.