Wnt signaling in prostate development and carcinogenesis

Instrumental and transcriptome analysis reveals the chemotherapeutic effects of doxorubicin-loaded black phosphate nanosheets on abiraterone-resistant prostate cancer

Prostate cancer is the second most common cause of cancer-related deaths in men and is common in most developed countries. Androgen deprivation therapy (ADT) that uses abiraterone acetate (AA) is an effective second-line treatment for prostate cancer. However, approximately 20-40% of patients develop primary resistance to abiraterone post-treatment. In this study, we aimed to understand the molecular mechanisms underlying the development of abiraterone resistance in prostate cancer cells and the potential use of black phosphorus nanosheets (BPNS) for treating abiraterone-resistant prostate cancer. We first established abiraterone-resistant prostate cancer PC-3 cells and found that these cells have higher migration ability than normal prostate cancer cells. Using comparative transcriptomic and bioinformatics analyses between abiraterone-sensitive PC-3 and abiraterone-resistant PC-3 cells, we highlighted the differentially expressed genes (DEGs) involved in the biological processes related to prostate gland morphogenesis, drug response, immune response, angiogenesis. We further studied the therapeutic effects of BPNS. Our results show that BPNS reduced the proliferation and migration of abiraterone-resistant PC-3 cells. Bioinformatics analysis, including gene ontology, Kyoto encyclopedia of genes and genomes enrichment analysis, and ingenuity pathway analysis (IPA) of the DEGs, suggested that BPNS treatment controlled cancer cell proliferation, metastasis, and oncogenic signaling pathways. Furthermore, the IPA gene network highlighted the involvement of the MMP family, ATF, and notch families in the anti-prostate cancer function of BPNS. Our findings suggest that BPNS may have a chemotherapeutic function in treating abiraterone-resistant prostate cancer.

Bone Health Management in the Continuum of Prostate Cancer Disease

Prostate cancer (PCa) is the second-leading cause of cancer-related deaths in men. PCa cells require androgen receptor (AR) signaling for their growth and survival. Androgen deprivation therapy (ADT) is the preferred treatment for patients with locally advanced and metastatic PCa disease. Despite their initial response to androgen blockade, most patients eventually will develop metastatic castration-resistant prostate cancer (mCRPC). Bone metastases are common in men with mCRPC, occurring in 30% of patients within 2 years of castration resistance and in >90% of patients over the course of the disease. Patients with mCRPC-induced bone metastasis develop lesions throughout their skeleton; the 5-year survival rate for these patients is 47%. Bone-metastasis-induced early changes in the bone that proceed the osteoblastic response in the bone matrix are monitored and detected via modern magnetic resonance and PET/CT imaging technologies. Various treatment options, such as targeting osteolytic metastasis with bisphosphonates, prednisone, dexamethasone, denosumab, immunotherapy, external beam radiation therapy, radiopharmaceuticals, surgery, and pain medications are employed to treat prostate-cancer-induced bone metastasis and manage bone health. However, these diagnostics and treatment options are not very accurate nor efficient enough to treat bone metastases and manage bone health. In this review, we present the pathogenesis of PCa-induced bone metastasis, its deleterious impacts on vital organs, the impact of metastatic PCa on bone health, treatment interventions for bone metastasis and management of bone- and skeletal-related events, and possible current and future therapeutic options for bone management in the continuum of prostate cancer disease.

MicroRNAs as biomarker and novel therapeutic target for posttraumatic stress disorder in Veterans

Posttraumatic stress disorder (PTSD) is a common psychiatric disorder for military Veterans, characterized by hyperarousal, intrusive thoughts, flashbacks, hypervigilance, and distress after experiencing traumatic events. Some of the known physiological effects of PTSD include hypothalamic-pituitary-adrenal (HPA)-axis imbalance, a cortical function resulting in neuronal deficit and changes in behavior. Moreover, excessive discharge of inflammatory molecules and a dysregulated immune system are implicated in the pathophysiology of PTSD. Due to complex nature of this disorder, the biological underpinnings of PTSD remain inexplicable. Investigating novel biomarkers to understanding the pathogenesis of PTSD may reflect the underlying molecular network for therapeutic use and treatment. Circulatory microRNAs (miRNAs) and exosomes are evolving biomarkers that have shown a key role in psychiatric and neurological disorders including PTSD. Given the unique nature of combat trauma, as well as evidence that a large portion of Veterans do not benefit from frontline treatments, focus on veterans specifically is warranted. In the present review, we delineate the identification and role of several miRNAs in PTSD among veterans. An association of miRNA with HPA-axis regulation through FKBP5, a key modulator in PTSD is discussed as an emerging molecule in psychiatric diseases. We conclude that miRNAs may be used as circulatory biomarker detection in Veterans with PTSD.

LncRNA BLACAT1 Promotes Proliferation, Migration and Invasion of Prostate Cancer Cells via Regulating miR-29a-3p/DVL3 Axis

Background:

Long non-coding RNA bladder cancer associated transcript 1 (BLACAT1) is oncogenic in several types of cancers. However, little is known concerning its expression and function in prostate cancer.

Methods:

Paired prostate cancer samples were collected, and the expression levels of BLACAT1, miR-29a-3p and disheveled segment polarity protein 3 (DVL3) were examined by quantitative real-time polymerase chain reaction (qRT-PCR); BLACAT1 shRNAs were transfected into PC-3 and LNCaP cell lines, and proliferative ability was detected by cell counting kit-8 (CCK-8) assay; qRT-PCR and Western blot were used to analyze the changes of miR-29a-3p and DVL3; dual-luciferase reporter gene assay was used to determine the regulatory relationships between miR-29a-3p and BLACAT1, and miR-29a-3p and DVL3.

Results:

BLACAT1 expression was significantly up-regulated in cancerous tissues of prostate cancer samples and positively correlated with the expression of DVL3, while negatively associated with miR-29a-3p. After the transfection of BLACAT1 shRNAs into prostate cancer cells, the proliferative ability and metastatic ability of cancer cells were significantly inhibited; BLACAT1 shRNAs could reduce the expression of DVL3 on both mRNA and protein expressions levels, the luciferase activity of BLACAT1 reporter was inhibited by miR-29a-3p, and DVL3 was validated as a target gene of miR-29a-3p.

Conclusion:

BLACAT1 expression is abnormally up-regulated in prostate cancer tissues. BLACAT1 can modulate the proliferative and metastatic ability of prostate cancer cells and have the potential to be the “ceRNA” to regulate the expression of DVL3 by sponging miR-29a-3p.

Olfactomedin 4 mediation of prostate stem/progenitor-like cell proliferation and differentiation via MYC

Olfactomedin 4 (OLFM4) is expressed in normal prostate epithelial cells and immortalized normal human prostate epithelial cells (RWPE1), but the identity of OLFM4-expressing cells within these populations and OLFM4's physiological functions in these cells have not been elucidated. Using single-cell RNA sequencing analysis, we found here that OLFM4 was expressed in multiple stem/progenitor-like cell populations in both the normal prostate epithelium and RWPE1 cells and was frequently co-expressed with KRT13 and LY6D in RWPE1 cells. Functionally, OLFM4-knockout RWPE1 cells exhibited enhanced proliferation of the stem/progenitor-like cell population, shifts stem/progenitor-like cell division to favor symmetric division and differentiated into higher levels PSA expression cells in organoid assays compared with OLFM4-wild RWPE1 cells. Bulk-cell RNA sequencing analysis pinpointed that cMYC expression were enhanced in the OLFM4-knockout RWPE1 cells compared with OLFM4-wild cells. Molecular and signaling pathway studies revealed an increase in the WNT/APC/MYC signaling pathway gene signature, as well as that of MYC target genes that regulate multiple biological processes, in OLFM4-knockout RWPE1 cells. These findings indicated that OLFM4 is co-expressed with multiple stem/progenitor cell marker genes in prostate epithelial cells and acts as a novel mediator in prostate stem/progenitor cell proliferation and differentiation.

Oncogenic and tumor-suppressive microRNAs in prostate cancer

MicroRNAs are known to be dysregulated in prostate cancer. These small noncoding RNAs can function as biomarkers and are involved in the biology of prostate cancer. The canonical mechanism for microRNAs is post-transcription regulation of gene expression via binding to the 3' untranslated region of mRNAs, resulting in RNA degradation and/or translational repression. Thus, oncogenic microRNAs, also known as oncomiRs, often have high expression in prostate cancer and target the mRNAs of tumor suppressors. Conversely, tumor-suppressive microRNAs have reduced expression in cancer and typically target oncogenes. Some microRNAs function outside the classical mechanism and serve to stabilize their mRNA targets. Herein, we review contemporary studies that demonstrate oncogenic and tumor-suppressive activity of microRNAs in prostate cancer.

SOX4: The unappreciated oncogene

SOX4 is an essential developmental transcription factor that regulates stemness, differentiation, progenitor development, and multiple developmental pathways including PI3K, Wnt, and TGFβ signaling. The SOX4 gene is frequently amplified and overexpressed in over 20 types of malignancies, and multiple lines of evidence support that notion that SOX4 is an oncogene. Its overexpression is due to both gene amplification and to activation of PI3K, Wnt, and TGFβ pathways that SOX4 regulates. SOX4 interacts with multiple other transcription factors, rendering many of its impacts on gene expression context and tissue-specific. Nevertheless, there are common themes that run through many of the effects of SOX4 hyperactivity, such as the promotion of cell survival, stemness, the epithelial to mesenchymal transition, migration, and metastasis. Specific targeting of SOX4 remains a challenge for future cancer research and drug development.

Expression of WNT1 in ameloblastoma and its significance

The present study aimed to measure the expression of WNT1 in ameloblastoma (AB). Immunohistochemistry was used to observe changes in WNT1 expression in 80 AB samples, 10 keratocystic odontogenic tumor (KCOT) samples and 10 normal oral mucosa (NOM) samples. Western blotting and reverse transcription-quantitative polymerase chain reaction (RT-qPCR) were used to measure WNT1 protein and mRNA expression, respectively, in 30 AB samples, 5 KCOT samples, 5 NOM samples and 3 tooth germ samples. Ectopic cytoplasmic expression of WNT1 was detected in AB; 88.8% (71/80) of the samples were WNT1-positive. The western blotting results demonstrated that compared with NOM (0.57±0.05), WNT1 expression was significantly higher in AB tissue (1.74±0.36, P<0.05), whereas it was not significantly different between AB and KCOT samples (0.80±0.06, P>0.05). RT-qPCR revealed that the level of WNT1 gene expression in AB was increased 2.43-fold compared with normal mucosa, and 1.77-fold compared with tooth germ tissue. In conclusion, WNT1 protein and mRNA expression were increased in AB, and there was ectopic cytoplasmic expression. This indicates that WNT1 may serve an important role in AB occurrence and development.

Morphoregulatory pathways in prostate ductal development

The mouse prostate is a male sex-accessory gland comprised of a branched ductal network arranged into three separate bilateral lobes: the anterior, dorsolateral, and ventral lobes. Prostate ductal development is the primary morphogenetic event in prostate development and requires a complex regulation of spatiotemporal factors. This review provides an overview of prostate development and the major genetic regulators and signaling pathways involved. To identify new areas for further study, we briefly highlight the likely important, but relatively understudied, role of the extracellular matrix (ECM). Finally, we point out the potential importance of the ECM in influencing the behavior and prognosis of prostate cancer. Developmental Dynamics 246:89-99, 2017. © 2016 Wiley Periodicals, Inc.

Cytoplasmic, full length and novel cleaved variant, TBLR1 reduces apoptosis in prostate cancer under androgen deprivation

TBLR1/TBL1XR1, a core component of the nuclear receptor corepressor (NCoR) complex critical for the regulation of multiple nuclear receptors, is a transcriptional coactivator of androgen receptor (AR) and functions as a tumor suppressor when expressed in the nucleus in prostate. Subcellular localization of a protein is critical for its function, and although TBLR1, as a transcriptional cofactor, has been primarily viewed as a nuclear protein, many cells also express variable levels of cytoplasmic TBLR1 and its cytoplasmic specific functions have not been studied. Prostate cancer (PCa) cells express moderately higher level of cytoplasmic TBLR1 compared to benign prostate cells. When comparing androgen-dependent (AD) to androgen-independent (AI) PCa, AI cells contain very high levels of TBLR1 cytoplasmic expression and low levels of nuclear expression. Overexpression of cytoplasmic TBLR1 in AD cells inhibits apoptosis induced by androgen deprivation therapy, either in an androgen free condition or in the presence of bicalutamide. Additionally, we identified a cytoplasmic specific isoform of TBLR1 (cvTBLR1) approximately 5 kDa lower in molecular weight, that is expressed at higher levels in AI PCa cells. By immunoprecipitation, we purified cvTBLR1 and using mass spectrometry analysis combined with N-terminal TMPP labeling and Edman degradation, we identified the cleavage site of cvTBLR1 at amino acid 89, truncating the first 88 amino acids of the N-terminus of the full length protein. Functionally, cvTBLR1 expressed in the cytoplasm reduced apoptosis in PCa cells and promoted growth, migration, and invasion. Finally, we identified a nuclear export signal sequence for TBLR1 cellular localization by deletion and site-directed mutagenesis. The roles of TBLR1 and cvTBLR1 provide novel insights into the mechanism of castration resistance and new strategies for PCa therapy.

A Tale of Two Signals: AR and WNT in Development and Tumorigenesis of Prostate and Mammary Gland

Prostate cancer (PCa) is one of the most common cancers and among the leading causes of cancer deaths for men in industrialized countries. It has long been recognized that the prostate is an androgen-dependent organ and PCa is an androgen-dependent disease. Androgen action is mediated by the androgen receptor (AR). Androgen deprivation therapy (ADT) is the standard treatment for metastatic PCa. However, almost all advanced PCa cases progress to castration-resistant prostate cancer (CRPC) after a period of ADT. A variety of mechanisms of progression from androgen-dependent PCa to CRPC under ADT have been postulated, but it remains largely unclear as to when and how castration resistance arises within prostate tumors. In addition, AR signaling may be modulated by extracellular factors among which are the cysteine-rich glycoproteins WNTs. The WNTs are capable of signaling through several pathways, the best-characterized being the canonical WNT/β-catenin/TCF-mediated canonical pathway. Recent studies from sequencing PCa genomes revealed that CRPC cells frequently harbor mutations in major components of the WNT/β-catenin pathway. Moreover, the finding of an interaction between β-catenin and AR suggests a possible mechanism of cross talk between WNT and androgen/AR signaling pathways. In this review, we discuss the current knowledge of both AR and WNT pathways in prostate development and tumorigenesis, and their interaction during development of CRPC. We also review the possible therapeutic application of drugs that target both AR and WNT/β-catenin pathways. Finally, we extend our review of AR and WNT signaling to the mammary gland system and breast cancer. We highlight that the role of AR signaling and its interaction with WNT signaling in these two hormone-related cancer types are highly context-dependent.

[Molecular mechanisms of niclosamide antitumor activity]

In this review the recent data regarding the antitumor activity of niclosamide and the molecular mechanisms of its antitumor activity are presented. Niclosamide has been used in the clinic for the treatment of intestinal parasite infections. In recent years in several screening investigations of various drugs and chemical compounds niclosamide was identified as a potential anticancer agent. Niclosamide not only inhibits the Wnt/β-catenin, mTORC1, STAT3, NF-κB and Notch signaling pathways, but also targets mitochondria in cancer cells to induce growth inhibition and apoptosis. A number of studies have established the anticancer activity of niclosamide in both in vitro and in vivo in xenotransplantation models using human tumors and immunodeficient mice. It is important that niclosamide is active not only against tumor cells but also cancer stem cells. Normal cells are resistant to niclosamide. The accumulated experimental data suggest niclosamide is a promising drug for the treatment of various types of cancer.

Hedgehog signaling in prostate epithelial-mesenchymal growth regulation

The prostate gland plays an important role in male reproduction, and is also an organ prone to diseases such as benign prostatic hyperplasia (BPH) and prostate cancer. The prostate consists of ducts with an inner layer of epithelium surrounded by stroma. Reciprocal signaling between these two cell compartments is instrumental to normal prostatic development, homeostasis, regeneration, as well as tumor formation. Hedgehog (HH) signaling is a master regulator in numerous developmental processes. In many organs, HH plays a key role in epithelial-mesenchymal signaling that regulates organ growth and tissue differentiation, and abnormal HH signaling has been implicated in the progression of various epithelial carcinomas. In this review, we focus on recent studies exploring the multipotency of endogenous postnatal and adult epithelial and stromal stem cells and studies addressing the role of HH in prostate development and cancer. We discuss the implications of the results for a new understanding of prostate development and disease. Insight into the cellular and molecular mechanisms underlying epithelial-mesenchymal growth regulation should provide a basis for devising innovative therapies to combat diseases of the prostate.

Physiopathological aspects of the Wnt/β-catenin signaling pathway in the male reproductive system

The Wnt/β-catenin signaling pathway controls several biological processes throughout development and adult life. Dysregulation of Wnt/β-catenin signaling underlies a wide range of pathologies in animals and humans, including cancer in different tissues. In this review, we provide an update of the Wnt/β-catenin signaling pathway and the possible roles of the Wnt/β-catenin signaling in the biology of testis, epididymis and prostate. Data from our laboratory suggest the involvement of 17β-estradiol and estrogen receptors (ERs) on the regulation of β-catenin expression in rat Sertoli cells. We also provide emerging evidences of the involvement of Wnt/β-catenin pathway in testis and prostate cancer. Our understanding of the role of Wnt/β-Catenin signaling in male reproductive tissues is still evolving, and several questions are open to be addressed in the future.

In utero exposure to TCDD alters Wnt signaling during mouse prostate development: linking ventral prostate agenesis to downregulated β-catenin signaling

In utero exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) causes ventral prostate agenesis in C57BL/6J mice by preventing ventral prostatic budding in the embryonic urogenital sinus (UGS). TCDD (5 μg/kg, po) administered to pregnant dams on embryonic day 15.5 (E15.5) activates the aryl hydrocarbon receptor in the UGS mesenchyme, disrupting the mesenchymally derived paracrine signaling that instructs epithelial prostatic budding. How TCDD alters the mesenchymal milieu is not well understood. We previously showed that TCDD disrupts some aspects of Wnt signaling in UGSs grown in vitro. Here we provide the first comprehensive, in vivo characterization of Wnt signaling in male E16.5 UGSs during normal development, and after in utero TCDD exposure. Vehicle- and TCDD-exposed UGSs were probed by in situ hybridization to assess relative abundance and localization of RNA from 46 genes that regulate Wnt signaling. TCDD altered the staining pattern of five genes, increasing staining for Wnt10a and Wnt16 and decreasing staining for Ror2, Rspo2, and Wif1. We also used immunohistochemistry to show, for the first time, activation of β-catenin (CTNNB1) signaling in ventral basal epithelium of control UGSs at E16.5. This onset of CTNNB1 signaling occurred immediately prior to the initiation of ventral prostatic budding and is characterized by a pronounced increase in CTNNB1 nuclear localization and subsequent expression of the CTNNB1 signaling target gene, Lef1. In utero TCDD exposure prevented the onset of CTNNB1 signaling and LEF1 expression in the ventral basal epithelium, thereby elucidating a likely mechanism by which TCDD contributes to failed prostatic budding in the ventral UGS.

The role of cancer-associated fibroblasts, solid stress and other microenvironmental factors in tumor progression and therapy resistance

Tumors are not merely masses of neoplastic cells but complex tissues composed of cellular and noncellular elements. This review provides recent data on the main components of a dynamic system, such as carcinoma associated fibroblasts that change the extracellular matrix (ECM) topology, induce stemness and promote metastasis-initiating cells. Altered production and characteristics of collagen, hyaluronan and other ECM proteins induce increased matrix stiffness. Stiffness along with tumor growth-induced solid stress and increased interstitial fluid pressure contribute to tumor progression and therapy resistance. Second, the role of immune cells, cytokines and chemokines is outlined. We discuss other noncellular characteristics of the tumor microenvironment such as hypoxia and extracellular pH in relation to neoangiogenesis. Overall, full understanding of the events driving the interactions between tumor cells and their environment is of crucial importance in overcoming treatment resistance and improving patient outcome.

The structural analysis of MARK4 and the exploration of specific inhibitors for the MARK family: a computational approach to obstruct the role of MARK4 in prostate cancer progression

The binding of identified ATP competitors specific to MARK4, characterized by a unique DFG Asp-in/αC helix-out inactive state, hampers the progression of prostate cancer.

Post genome-wide association studies functional characterization of prostate cancer risk loci

Background

Over the last decade, genome-wide association studies (GWAS) have discovered many risk associated single nucleotide polymorphisms (SNPs) of prostate cancer (PCa). However, the majority of the associated PCa SNPs, including those in linkage disequilibrium (LD) blocks, are generally not located in protein coding regions. The systematical investigation of the functional roles of these SNPs, especially the non-coding SNPs, becomes very necessary and helpful to the understanding of the molecular mechanism of PCa.

Results

In this work, we proposed a comprehensive framework at network level to integrate the SNP annotation, target gene assignment, gene ontology (GO) classification, pathway enrichment analysis and regulatory network reconstruction to illustrate the molecular functions of PCa associated SNPs. By LD expansion, we first identified 1828 LD SNPs using 49 reported GWAS SNPs as a start. We carefully annotated these 1828 LD SNPs via either UCSC known genes, UCSC regulation elements, or expression Quantitative Trait Loci (eQTL) data. As a result, we found 1154 SNPs were functionally annotated and obtained 205 unique PCa genes for further enrichment analysis. The enriched GO biological processes and pathways were found mainly related to regulation of cell death, apoptosis, cell proliferation, and metabolic process, which have been proved essential to cancer development. We constructed PCa genes specific transcription regulatory networks, finding several important genetic regulators for PCa, such as IGF-1/IGF-2 receptors, SP1, CREB1, and androgen receptor (AR).

Conclusions

A comprehensive framework was proposed for integrative and systematic analysis of PCa SNPs, the analysis can provide essential information for the understanding of the regulatory function of GWAS SNPs in PCa, and will facilitate the discovery of novel candidate biomarkers for diagnosis and prognosis of PCa.

Esculetin suppresses proliferation of human colon cancer cells by directly targeting β-catenin

The Wnt pathway is a promising therapeutic and preventive target in various human cancers. The transcriptional complex of β-catenin-T-cell factor (Tcf), a key mediator of canonical Wnt signaling, has been implicated in human colon cancer development. Current treatment of colon cancer depends on traditional cytotoxic agents with limited effects. Therefore, the identification of natural compounds that can disrupt the β-catenin-TcF complex to suppress cancer cell growth with fewer adverse side effects is needed. To identify compounds that inhibit the association between β-catenin and Tcf, we used computer docking to screen a natural compound library. Esculetin, also known as 6,7-dihydroxycoumarin, is a derivative of coumarin and was identified as a potential small-molecule inhibitor of the Wnt-β-catenin pathway. We then evaluated the effect of esculetin on the growth of various human colon cancer cell lines and its effect on Wnt-β-catenin signaling in cells and in an embryonic model. Esculetin disrupted the formation of the β-catenin-Tcf complex through direct binding with the Lys312, Gly307, Lys345, and Asn387 residues of β-catenin in colon cancer cells. In addition, esculetin effectively decreased viability and inhibited anchorage-independent growth of colon cancer cells. Esculetin potently antagonized the cellular effects of β-catenin-dependent activity, and in vivo treatment with esculetin suppressed tumor growth in a colon cancer xenograft mouse model. Our data indicate that the interaction between esculetin and β-catenin inhibits the formation of the β-catenin-Tcf complex, which could contribute to esculetin's positive therapeutic and preventive effects against colon carcinogenesis.

TCDD inhibition of canonical Wnt signaling disrupts prostatic bud formation in mouse urogenital sinus

In mice, in utero exposure to 2,3,7,8-tetrachlorodibenzo-p- dioxin (TCDD) reduces the number of dorsolateral prostatic buds resulting in a smaller dorsolateral prostate and prevents formation of ventral buds culminating in ventral prostate agenesis. The genes and signaling pathways affected by TCDD that are responsible for disrupting prostate development are largely unknown. Here we show that treatment of urogenital sinus (UGS) organ cultures with known inhibitors of canonical Wnt signaling also inhibits prostatic bud formation. In support of the hypothesis that TCDD decreases canonical Wnt signaling, we identify inhibitory effects of TCDD on multiple components of the canonical Wnt signaling pathway in the UGS that temporally coincide with the inhibitory effect of TCDD on prostatic bud formation: (1) expression of R-spondins (Rspo2 and Rspo3) that promote canonical Wnt signaling is reduced; (2) expression of Lef1, Tcf1, and Wif1, established canonical Wnt target genes, is decreased; (3) expression of Lgr5, a RSPO receptor that activates canonical Wnt signaling, is reduced; and (4) expression of Dickkopfs (Dkks), inhibitors of canonical Wnt signaling, is not increased by TCDD. Thus, the TCDD-induced reduction in canonical Wnt signaling is associated with a decrease in activators (Rspo2 and Rspo3) rather than an increase in inhibitors (Dkk1 and Dkk2) of the pathway. This study focuses on determining whether treatment of TCDD-exposed UGS organ cultures with RSPO2 and/or RSPO3 is capable of rescuing the inhibitory effects of TCDD on canonical Wnt signaling and prostatic bud formation. We discovered that each RSPO alone or in combination partially rescues TCDD inhibition of both canonical Wnt signaling and prostatic bud formation.

Epigenetic silencing of DKK2 and Wnt signal pathway components in human ovarian carcinoma

Wnt/β-Catenin signaling dysregulation is involved in tumorigenesis. Furthermore, epigenetic modification of the Dickkopf (DKK) family (DKK1-DKK4) has been shown to be important in Wnt signaling regulation. In this study, the role of DKK2, a Wnt antagonist, in epithelial ovarian cancer (EOC) was evaluated by examining the expression and methylation of DKK2 in SKOV3 and ES-2 ovarian cancer cell lines and 78 tissues collected from patients (50 ovarian carcinoma, 20 benign tumor and 8 normal ovarian tissues). DKK2 is highly downregulated in EOCs; however, DKK2 expression levels are higher in both normal tissues and benign tumors. In most cases of ovarian carcinoma, DKK2 is methylated, compared with the more common unmethylated form present in benign tumors and normal ovarian tissues. Additionally, DKK2 may be epigenetically silenced by methylation in higher grades and stages of EOC. Functional analysis revealed that overexpression of DKK2 suppressed malignant cell growth and invasion in SKOV3 and ES-2 cell lines. The expression of the downstream genes of Wnt signaling, including β-catenin, c-Myc and cyclin D1, was decreased in DKK2-transfected cells compared with mock cells. The expression of matrix metalloproteinase-2 and focal adhesion kinase were also decreased in DKK2 transfectants, supporting findings indicating inhibition of cell migration and invasion. This report provides novel indications that DKK2 is a unique hypermethylated target gene in EOC and that DKK2 may contribute to tumorigenesis in EOC through the Wnt/β-catenin signaling mechanisms.

Why are epididymal tumours so rare?

Epididymal tumour incidence is at most 0.03% of all male cancers. It is an enigma why the human epididymis does not often succumb to cancer, when it expresses markers of stem and cancer cells, and constitutively expresses oncogenes, pro-proliferative and pro-angiogenic factors that allow tumour cells to escape immunosurveillance in cancer-prone tissues. The privileged position of the human epididymis in evading tumourigenicity is reflected in transgenic mouse models in which induction of tumours in other organs is not accompanied by epididymal neoplasia. The epididymis appears to: (i) prevent tumour initiation (it probably lacks stem cells and has strong anti-oxidative mechanisms, active tumour suppressors and inactive oncogene products); (ii) foster tumour monitoring and destruction (by strong immuno-surveillance and -eradication, and cellular senescence); (iii) avert proliferation and angiogenesis (with persistent tight junctions, the presence of anti-angiogenic factors and misplaced pro-angiogenic factors), which together (iv) promote dormancy and restrict dividing cells to hyperplasia. Epididymal cells may be rendered non-responsive to oncogenic stimuli by the constitutive expression of factors generally inducible in tumours, and resistant to the normal epididymal environment, which mimics that of a tumour niche promoting tumour growth. The threshold for tumour initiation may thus be higher in the epididymis than in other organs. Several anti-tumour mechanisms are those that maintain spermatozoa quiescent and immunologically silent, so the low incidence of cancer in the epididymis may be a consequence of its role in sperm maturation and storage. Understanding these mechanisms may throw light on cancer prevention and therapy in general.

Oncogenic activation in prostate cancer progression and metastasis: Molecular insights and future challenges

Prostate cancer is a leading cause of death among men in the United States, and currently early diagnosis and appropriate treatment remain key approaches for patient care. Molecularly prostate cancer cells carry multiple perturbations that generate malignant phenotype capable of uncontrolled growth, survival, and invasion-metastasis to other organs. These alterations are acquired both by genetic and epigenetic changes in tumor cells resulting in the activation of growth factor receptors, signaling proteins, kinases, transcription factors and coregulators, and multiple proteases required for the progression of the disease. Recent advances provide novel insights into the molecular functions of these oncogenic activators, implicating potential therapeutic targeting opportunities for the treatment of prostate cancer.