CRISPR activation screen identifies TGFβ-associated PEG10 as a crucial tumor suppressor in Ewing sarcoma

As the second most common pediatric bone and soft tissue tumor, Ewing sarcoma (ES) is an aggressive disease with a pathognomonic chromosomal translocation t(11;22) resulting in expression of EWS-FLI1, an “undruggable” fusion protein acting as transcriptional modulator. EWS-FLI1 rewires the protein expression in cancer cells by activating and repressing a multitude of genes. The role and contribution of most repressed genes remains unknown to date. To address this, we established a CRISPR activation system in clonal SKNMC cell lines and interrogated a custom focused library covering 871 genes repressed by EWS-FLI1. Among the hits several members of the TGFβ pathway were identified, where PEG10 emerged as prime candidate due to its strong antiproliferative effect. Mechanistic investigations revealed that PEG10 overexpression caused cellular dropout via induction of cell death. Furthermore, non-canonical TGFβ pathways such as RAF/MEK/ERK, MKK/JNK, MKK/P38, known to lead to apoptosis or autophagy, were highly activated upon PEG10 overexpression. Our study sheds new light onto the contribution of TGFβ signalling pathway repression to ES tumorigenesis and suggest that its re-activation might constitute a novel therapeutic strategy.

Functional Genomic Screening During Somatic Cell Reprogramming Identifies DKK3 as a Roadblock of Organ Regeneration

Somatic cell reprogramming and tissue repair share relevant factors and molecular programs. Here, Dickkopf-3 (DKK3) is identified as novel factor for organ regeneration using combined transcription-factor-induced reprogramming and RNA-interference techniques. Loss of Dkk3 enhances the generation of induced pluripotent stem cells but does not affect de novo derivation of embryonic stem cells, three-germ-layer differentiation or colony formation capacity of liver and pancreatic organoids. However, DKK3 expression levels in wildtype animals and serum levels in human patients are elevated upon injury. Accordingly, Dkk3-null mice display less liver damage upon acute and chronic failure mediated by increased proliferation in hepatocytes and LGR5+ liver progenitor cell population, respectively. Similarly, recovery from experimental pancreatitis is accelerated. Regeneration onset occurs in the acinar compartment accompanied by virtually abolished canonical-Wnt-signaling in Dkk3-null animals. This results in reduced expression of the Hedgehog repressor Gli3 and increased Hedgehog-signaling activity upon Dkk3 loss. Collectively, these data reveal Dkk3 as a key regulator of organ regeneration via a direct, previously unacknowledged link between DKK3, canonical-Wnt-, and Hedgehog-signaling.

BZW1 promotes cell proliferation in prostate cancer by regulating TGF-β1/Smad pathway

Recently, basic leucine zipper and the W2 domain-containing protein 1 (BZW1) are reported to be implicated in tumor progression. However, the role of BZW1 in prostate cancer remains unknown. This study is aimed to investigate the expression of BZW1 and its influence on cell proliferation in prostate cancer. Then, the expression levels of BZW1 were measured in 136 cases of prostate cancer and matched adjacent non-cancerous prostate tissues by quantificational real-time polymerase chain reaction (qRT-PCR) and immunohistochemistry (IHC). The effect of BZW1 on cell proliferation was further explored. QRT-PCR analysis showed that the mRNA levels of BZW1 in prostate cancer were significantly greater compared with those in matched adjacent non-cancerous prostate tissues (P< 0.001). IHC results showed that the high-expression rates of BZW1 in prostate cancer and matched adjacent non-cancerous prostate tissues were 68.4% and 32.4%, and the difference was statistically significant (P< 0.001). BZW1 high expression significantly correlated with T stage, lymph node metastasis, prostate-specific antigen (PSA) and Gleason score (P< 0.05). Patients with BZW1 high expression presented unfavorable prognosis compared with those with BZW1 low expression (P= 0.002). In addition, CCK-8 and colony formation assays revealed that BZW1 overexpression significantly promoted cell proliferation in vitro. Tumor xenograft has shown that BZW1 knockdown significantly inhibited tumor growth in vivo. Moreover, BZW1 overexpression activated the TGF-β1/Smad1/Smad3 pathway. Therefore, these data indicate that BZW1 overexpression predicts poorer prognosis and promotes cell proliferation in prostate cancer by regulating TGF-β1/Smad pathway.

Vitamin D sufficiency enhances differentiation of patient-derived prostate epithelial organoids

Vitamin D is an essential steroid hormone that regulates systemic calcium homeostasis and cell fate decisions. The prostate gland is hormonally regulated, requiring steroids for proliferation and differentiation of secretory luminal cells. Vitamin D deficiency is associated with an increased risk of lethal prostate cancer, which exhibits a dedifferentiated pathology, linking vitamin D sufficiency to epithelial differentiation. To determine vitamin D regulation of prostatic epithelial differentiation, patient-derived benign prostate epithelial organoids were grown in vitamin D-deficient or -sufficient conditions. Organoids were assessed by phenotype and single-cell RNA sequencing. Mechanistic validation demonstrated that vitamin D sufficiency promoted organoid growth and accelerated differentiation by inhibiting canonical Wnt activity and suppressing Wnt family member DKK3. Wnt and DKK3 were also reduced by vitamin D in prostate tissue explants by spatial transcriptomics. Wnt dysregulation is a known contributor to aggressive prostate cancer, thus findings further link vitamin D deficiency to lethal disease.

Differential gene methylation patterns in cancerous and non‑cancerous cells

Large-scale projects, such as The Cancer Genome Atlas (TCGA), Human Epigenome Project (HEP) and Human Epigenome Atlas (HEA), provide an insight into DNA methylation and histone modification markers. Changes in the epigenome significantly contribute to the initiation and progression of cancer. The goal of the present study was to characterize the prostate cancer malignant transformation model using the CpG island methylation pattern. The Human Prostate Cancer EpiTect Methyl II Signature PCR Array was used to evaluate the methylation status of 22 genes in prostate cancer cell lines: PC3, PC3M, PC3MPro4 and PC3MLN4, each representing different metastatic potential in vivo. Subsequently, it was ascertained whether DNA methylation plays a role in the expression of these genes in prostate cancer cells. Hypermethylation of APC, DKK3, GPX3, GSTP1, MGMT, PTGS2, RASSF1, TIMP2 and TNFRSF10D resulted in downregulation of their expression in prostate cancer cell lines as compared to WT fibroblasts. Mining of the TCGA data deposited in the MetHC database found increases in the methylation status of these 9 genes in prostate cancer patients, further supporting the role of methylation in altering the expression of these genes in prostate cancer. Future studies are warranted to investigate the role of these proteins in prostate cancer development.

Crosstalk of Intercellular Signaling Pathways in the Generation of Midbrain Dopaminergic Neurons In Vivo and from Stem Cells

Dopamine-synthesizing neurons located in the mammalian ventral midbrain are at the center stage of biomedical research due to their involvement in severe human neuropsychiatric and neurodegenerative disorders, most prominently Parkinson’s Disease (PD). The induction of midbrain dopaminergic (mDA) neurons depends on two important signaling centers of the mammalian embryo: the ventral midline or floor plate (FP) of the neural tube, and the isthmic organizer (IsO) at the mid-/hindbrain boundary (MHB). Cells located within and close to the FP secrete sonic hedgehog (SHH), and members of the wingless-type MMTV integration site family (WNT1/5A), as well as bone morphogenetic protein (BMP) family. The IsO cells secrete WNT1 and the fibroblast growth factor 8 (FGF8). Accordingly, the FGF8, SHH, WNT, and BMP signaling pathways play crucial roles during the development of the mDA neurons in the mammalian embryo. Moreover, these morphogens are essential for the generation of stem cell-derived mDA neurons, which are critical for the modeling, drug screening, and cell replacement therapy of PD. This review summarizes our current knowledge about the functions and crosstalk of these signaling pathways in mammalian mDA neuron development in vivo and their applications in stem cell-based paradigms for the efficient derivation of these neurons in vitro.

Downregulation of C-Terminal Tensin-Like Protein (CTEN) Suppresses Prostate Cell Proliferation and Contributes to Acinar Morphogenesis

C-terminal tensin-like protein (CTEN) is a member of tensin family, which is crucial for the assembly of cell-matrix adhesome. Unlike other tensins, CTEN is selectively expressed only in a few tissues such as the prostate. However, the biological relevance of CTEN in normal prostate is poorly understood. In this study, we revealed that CTEN is selectively expressed in the prostate epithelial cells and enriched in the basal compartment. Knockdown of CTEN in RWPE-1 cells suppresses cell proliferation and results in G1/S cell cycle arrest as well as the accumulation of cyclin-dependent kinase (CDK) inhibitors, p21 and p27. Moreover, the expression of CTEN is decreased during acinar morphogenesis using Matrigel-based three-dimensional (3D) culture. In the course of acinar formation, induction of CTEN reactivates focal adhesion kinase (FAK) Y³⁹⁷ phosphorylation and disrupts the acini structure. This study, to our knowledge, is the first report demonstrating that downregulation of CTEN is required for luminal differentiation and acinar formation.

Therapeutic potency of Wnt signaling antagonists in the pathogenesis of prostate cancer, current status and perspectives

Prostate cancer is a major cause of cancer-related death in males. Wnt/β-catenin signaling plays a critical role in the pathogenesis of this disease by regulating angiogenesis, drug resistance, cell proliferation, and apoptosis. Suppression of Wnt canonical or noncanonical signaling pathways via Wnt biological or pharmacological antagonists is a potentially novel therapeutic approach for patients with prostate cancer. This review summarizes the role of Wnt signaling inhibitors in the pathogenesis of prostate cancer for a better understanding and hence a better management of this disease.

Protective effect of stromal Dickkopf-3 in prostate cancer: opposing roles for TGFBI and ECM-1

Aberrant transforming growth factor-β (TGF-β) signaling is a hallmark of the stromal microenvironment in cancer. Dickkopf-3 (Dkk-3), shown to inhibit TGF-β signaling, is downregulated in prostate cancer and upregulated in the stroma in benign prostatic hyperplasia, but the function of stromal Dkk-3 is unclear. Here we show that DKK3 silencing in WPMY-1 prostate stromal cells increases TGF-β signaling activity and that stromal cell-conditioned media inhibit prostate cancer cell invasion in a Dkk-3-dependent manner. DKK3 silencing increased the level of the cell-adhesion regulator TGF-β-induced protein (TGFBI) in stromal and epithelial cell-conditioned media, and recombinant TGFBI increased prostate cancer cell invasion. Reduced expression of Dkk-3 in patient tumors was associated with increased expression of TGFBI. DKK3 silencing reduced the level of extracellular matrix protein-1 (ECM-1) in prostate stromal cell-conditioned media but increased it in epithelial cell-conditioned media, and recombinant ECM-1 inhibited TGFBI-induced prostate cancer cell invasion. Increased ECM1 and DKK3 mRNA expression in prostate tumors was associated with increased relapse-free survival. These observations are consistent with a model in which the loss of Dkk-3 in prostate cancer leads to increased secretion of TGFBI and ECM-1, which have tumor-promoting and tumor-protective roles, respectively. Determining how the balance between the opposing roles of extracellular factors influences prostate carcinogenesis will be key to developing therapies that target the tumor microenvironment.

CRISPR-Mediated Reactivation of DKK3 Expression Attenuates TGF-β Signaling in Prostate Cancer

The DKK3 gene encodes a secreted protein, Dkk-3, that inhibits prostate tumor growth and metastasis. DKK3 is downregulated by promoter methylation in many types of cancer, including prostate cancer. Gene silencing studies have shown that Dkk-3 maintains normal prostate epithelial cell homeostasis by limiting TGF-β/Smad signaling. While ectopic expression of Dkk-3 leads to prostate cancer cell apoptosis, it is unclear if Dkk-3 has a physiological role in cancer cells. Here, we show that treatment of PC3 prostate cancer cells with the DNA methyltransferase (DNMT) inhibitor decitabine demethylates the DKK3 promoter, induces DKK3 expression, and inhibits TGF-β/Smad-dependent transcriptional activity. Direct induction of DKK3 expression using CRISPR-dCas9-VPR also inhibited TGF-β/Smad-dependent transcription and attenuated PC3 cell migration and proliferation. These effects were not observed in C4-2B cells, which do not respond to TGF-β. TGF-β signals can regulate gene expression directly via SMAD proteins and indirectly by increasing DNMT expression, leading to promoter methylation. Analysis of genes downregulated by promoter methylation and predicted to be regulated by TGF-β found that DKK3 induction increased expression of PTGS2, which encodes cyclooxygenase-2. Together, these observations provide support for using CRISPR-mediated induction of DKK3 as a potential therapeutic approach for prostate cancer and highlight complexities in Dkk-3 regulation of TGF-β signaling.

Dkk3 dependent transcriptional regulation controls age related skeletal muscle atrophy

Age-related muscle atrophy (sarcopenia) is the leading cause for disability in aged population, but the underlying molecular mechanisms are poorly understood. Here we identify a novel role for the secreted glycoprotein Dickkopf 3 (Dkk3) in sarcopenia. Forced expression of Dkk3 in muscles in young mice leads to muscle atrophy. Conversely, reducing its expression in old muscles restores both muscle size and function. Dkk3 induces nuclear import of β-catenin and enhances its interaction with FoxO3, which in turn activates the transcription of E3 ubiquitin ligase Fbxo32 and Trim63, driving muscle atrophy. These findings suggest that Dkk3 may be used as diagnostic marker and as therapeutic target for age-related muscle atrophy, and reveal a distinct transcriptional control of Fbxo32 and Trim63.

Prostate organogenesis: tissue induction, hormonal regulation and cell type specification

Prostate organogenesis is a complex process that is primarily mediated by the presence of androgens and subsequent mesenchyme-epithelial interactions. The investigation of prostate development is partly driven by its potential relevance to prostate cancer, in particular the apparent re-awakening of key developmental programs that occur during tumorigenesis. However, our current knowledge of the mechanisms that drive prostate organogenesis is far from complete. Here, we provide a comprehensive overview of prostate development, focusing on recent findings regarding sexual dimorphism, bud induction, branching morphogenesis and cellular differentiation.

Roles of the ERK1/2 and PI3K/PKB signaling pathways in regulating the expression of extracellular matrix genes in rat pulmonary artery smooth muscle cells

Purpose:

To investigate the mechanisms by which PD98059 and LY294002 interfere with the abnormal deposition of extracellular matrix regulated by connective tissue growth factor (CTGF) of rat pulmonary artery smooth muscle cells (PASMCs).

Methods:

Rat PASMCs were cultured and separated into a control group. Real-time fluorescence quantitative PCR was performed to detect the expression of collagen III and fibronectin mRNA. Immunohistochemistry and western blot analyses were performed to detect the expression of collagen III protein.

Results:

The expression of collagen III and fibronectin mRNA was greater in PASMCs stimulated with CTGF for 48 h, than in the control group. After 72h of stimulation, the expression of collagen III protein in the PASMCs was greater than in the control. The equivalent gene and protein expression of the CPL group were much more significant.

Conclusions:

CTGF can stimulate the gene expression of collagen III and fibronectin in PASMCs, which may be one of the factors that promote pulmonary vascular remodeling (PVR) under the conditions of pulmonary arterial hypertension (PAH). PD98059 and LY294002 can inhibit the ERK1/2 and PI3K/PKB signaling pathways, respectively, thus interfering with the biological effects of CTGF. This may be a new way to reduce PAH-PVR.

Dickkopf-3 is upregulated in osteoarthritis and has a chondroprotective role

OBJECTIVE

Dickkopf-3 (Dkk3) is a non-canonical member of the Dkk family of Wnt antagonists and its upregulation has been reported in microarray analysis of cartilage from mouse models of osteoarthritis (OA). In this study we assessed Dkk3 expression in human OA cartilage to ascertain its potential role in chondrocyte signaling and cartilage maintenance.

METHODS

Dkk3 expression was analysed in human adult OA cartilage and synovial tissues and during chondrogenesis of ATDC5 and human mesenchymal stem cells. The role of Dkk3 in cartilage maintenance was analysed by incubation of bovine and human cartilage explants with interleukin-1β (IL1β) and oncostatin-M (OSM). Dkk3 gene expression was measured in cartilage following murine hip avulsion. Whether Dkk3 influenced Wnt, TGFβ and activin cell signaling was assessed in primary human chondrocytes and SW1353 chondrosarcoma cells using qRT-PCR and luminescence assays.

RESULTS

Increased gene and protein levels of Dkk3 were detected in human OA cartilage, synovial tissue and synovial fluid. DKK3 gene expression was decreased during chondrogenesis of both ATDC5 cells and humans MSCs. Dkk3 inhibited IL1β and OSM-mediated proteoglycan loss from human and bovine cartilage explants and collagen loss from bovine cartilage explants. Cartilage DKK3 expression was decreased following hip avulsion injury. TGFβ signaling was enhanced by Dkk3 whilst Wnt3a and activin signaling were inhibited.

CONCLUSIONS

We provide evidence that Dkk3 is upregulated in OA and may have a protective effect on cartilage integrity by preventing proteoglycan loss and helping to restore OA-relevant signaling pathway activity. Targeting Dkk3 may be a novel approach in the treatment of OA.

Determination of the substrate repertoire of ADAMTS2, 3, and 14 significantly broadens their functions and identifies extracellular matrix organization and TGF-β signaling as primary targets

A disintegrin and metalloproteinase with thrombospondin type I motif (ADAMTS)2, 3, and 14 are collectively named procollagen N-proteinases (pNPs) because of their specific ability to cleave the aminopropeptide of fibrillar procollagens. Several reports also indicate that they could be involved in other biological processes, such as blood coagulation, development, and male fertility, but the potential substrates associated with these activities remain unknown. Using the recently described N-terminal amine isotopic labeling of substrate approach, we analyzed the secretomes of human fibroblasts and identified 8, 17, and 22 candidate substrates for ADAMTS2, 3, and 14, respectively. Among these newly identified substrates, many are components of the extracellular matrix and/or proteins related to cell signaling such as latent TGF-β binding protein 1, TGF-β RIII, and dickkopf-related protein 3. Candidate substrates for the 3 ADAMTS have been biochemically validated in different contexts, and the implication of ADAMTS2 in the control of TGF-β activity has been further demonstrated in human fibroblasts. Finally, the cleavage site specificity was assessed showing a clear and unique preference for nonpolar or slightly hydrophobic amino acids. This work shows that the activities of the pNPs extend far beyond the classically reported processing of the aminopropeptide of fibrillar collagens and that they should now be considered as multilevel regulators of matrix deposition and remodeling.-Bekhouche, M., Leduc, C., Dupont, L., Janssen, L., Delolme, F., Vadon-Le Goff, S., Smargiasso, N., Baiwir, D., Mazzucchelli, G., Zanella-Cleon, I., Dubail, J., De Pauw, E., Nusgens, B., Hulmes, D. J. S., Moali, C., Colige, A. Determination of the substrate repertoire of ADAMTS2, 3, and 14 significantly broadens their functions and identifies extracellular matrix organization and TGF-β signaling as primary targets.

The Aplidin analogs PM01215 and PM02781 inhibit angiogenesis in vitro and in vivo

BACKGROUND

Novel synthesized analogs of Aplidin, PM01215 and PM02781, were tested for antiangiogenic effects on primary human endothelial cells in vitro and for inhibition of angiogenesis and tumor growth in vivo.

METHODS

Antiangiogenic activity of both derivatives was evaluated by real-time cell proliferation, capillary tube formation and vascular endothelial growth factor (VEGF)-induced spheroid sprouting assays. Distribution of endothelial cells in the different phases of the cell cycle was analyzed by flow cytometry. Aplidin analogs were tested in vivo in chicken chorioallantoic membrane (CAM) assays.

RESULTS

Both derivatives inhibited angiogenic capacities of human endothelial cells (HUVECs) in vitro at low nanomolar concentrations. Antiangiogenic effects of both analogs were observed in the CAM. In addition, growth of human multiple myeloma xenografts in vivo in CAM was significantly reduced after application of both analogs. On the molecular level, both derivatives induced cell cycle arrest in G1 phase. This growth arrest of endothelial cells correlated with induction of the cell cycle inhibitor p16(INK4A) and increased senescence-associated beta galactosidase activity. In addition, Aplidin analogs induced oxidative stress and decreased production of the vascular maturation factors Vasohibin-1 and Dickkopf-3.

CONCLUSIONS

From these findings we conclude that both analogs are promising agents for the development of antiangiogenic drugs acting independent on classical inhibition of VEGF signaling.

Effects of DKK-3, a Wnt signaling inhibitor, on dendritic cell phenotype and T cell polarization

Wnt signaling plays crucial roles in regulation of a wide range of processes in different cell types including immune cells and, in particular, dendritic cells and T cells. Growing indications point out that Wnt pathway components modulate the both innate and adaptive immune responses through regulating DC functions. We investigated the effects of recombinant DKK-3 protein on the phenotype and biological functions of bone marrow-derived DCs (BM-DCs) as well as T cell polarization. The phenotype and the cytokine production of BM-derived DCs in the presence DKK-3 were analyzed using flow cytometry and ELISA, respectively. Also, capability of DCs to activate T cells was evaluated by CFSE-labeled splenocytes. Regulatory T cell induction, T cell polarization, and cytokine secretion were assessed by flow cytometry and ELISA in splenocytes cultured in the presence of DKK-3. Our results showed that the expression of CD86 and CD40 increased in the DKK-3-treated DC, while the expression of PDL-1 and PDL-2 diminished. Furthermore, the presence of DKK-3 decreased IL-10 and IL-4 production and increased IFN-gamma production by treated DCs.DKK-3. Moreover, DKK-3 shifted naive CD4 T cells towards TH1 cells through up-regulation of T-bet and down-regulation of GATA-3. Our results, therefore, suggest that DKK-3 protein has the ability to promote the generation of Th1-immunostimulatory DCs from its precursors.

A screen for transcription factor targets of glycogen synthase kinase-3 highlights an inverse correlation of NFκB and androgen receptor signaling in prostate cancer

Expression of Glycogen Synthase Kinase-3 (GSK-3) is elevated in prostate cancer and its inhibition reduces prostate cancer cell proliferation, in part by reducing androgen receptor (AR) signaling. However, GSK-3 inhibition can also activate signals that promote cell proliferation and survival, which may preclude the use of GSK-3 inhibitors in the clinic. To identify such signals in prostate cancer, we screened for changes in transcription factor target DNA binding activity in GSK-3-silenced cells. Among the alterations was a reduction in AR DNA target binding, as predicted from previous studies, and an increase in NFκB DNA target binding. Consistent with the latter, gene silencing of GSK-3 or inhibition using the GSK-3 inhibitor CHIR99021 increased basal NFκB transcriptional activity. Activation of NFκB was accompanied by an increase in the level of the NFκB family member RelB. Conversely, silencing RelB reduced activation of NFκB by CHIR99021. Furthermore, the reduction of prostate cancer cell proliferation by CHIR99021 was potentiated by inhibition of NFκB signaling using the IKK inhibitor PS1145. Finally, stratification of human prostate tumor gene expression data for GSK3 revealed an inverse correlation between NFκB-dependent and androgen-dependent gene expression, consistent with the results from the transcription factor target DNA binding screen. In addition, there was a correlation between expression of androgen-repressed NFκB target genes and reduced survival of patients with metastatic prostate cancer. These findings highlight an association between GSK-3/AR and NFκB signaling and its potential clinical importance in metastatic prostate cancer.

Dickkopf Homolog 3 Induces Stem Cell Differentiation into Smooth Muscle Lineage via ATF6 Signalling

Smooth muscle cells (SMCs) are a key component of healthy and tissue engineered vessels and play a crucial role in vascular development and the pathogenic events of vascular remodeling i.e. restenosis. However, the cell source from which they can be isolated is limited. Embryonic stem (ES) cells that have the remarkable capability to differentiate into vascular SMCs in response to specific stimuli provide a useful model for studying SMC differentiation. Previous studies suggested that dickkopf homolog 3 (DKK3) has a role in human partially induced pluripotent stem cell to SMC differentiation. Here, we demonstrate that the expression of DKK3 is essential for the expression of SMC markers and myocardin at both the mRNA and protein levels during mouse ES cell differentiation into SMCs (ESC-SMC differentiation). Overexpression of DKK3 leads to further up-regulation of the aforementioned markers. Further investigation indicates that DKK3 added as a cytokine activates activating transcription factor 6 (ATF6), leading to the increased binding of ATF6 on the myocardin promoter and increased its expression. In addition, inhibition of extracellular signal-regulated kinases 1/2 (ERK1/2) promotes the expression of ATF6 and leads to further increase of myocardin transcription. Our findings offer a novel mechanism by which DKK3 regulates ESC-SMC differentiation by activating ATF6 and promoting myocardin expression.

Essential roles of epithelial bone morphogenetic protein signaling during prostatic development

Prostate is a male sex-accessory organ. The prostatic epithelia consist primarily of basal and luminal cells that differentiate from embryonic urogenital sinus epithelia. Prostate tumors are believed to originate in the basal and luminal cells. However, factors that promote normal epithelial differentiation have not been well elucidated, particularly for bone morphogenetic protein (Bmp) signaling. This study shows that Bmp signaling prominently increases during prostatic differentiation in the luminal epithelia, which is monitored by the expression of phosphorylated Smad1/5/8. To elucidate the mechanism of epithelial differentiation and the function of Bmp signaling during prostatic development, conditional male mutant mouse analysis for the epithelial-specific Bmp receptor 1a (Bmpr1a) was performed. We demonstrate that Bmp signaling is indispensable for luminal cell maturation, which regulates basal cell proliferation. Expression of the prostatic epithelial regulatory gene Nkx3.1 was significantly reduced in the Bmpr1a mutants. These results indicate that Bmp signaling is a key factor for prostatic epithelial differentiation, possibly by controlling the prostatic regulatory gene Nkx3.1.

Adenovirus-mediated REIC/Dkk-3 gene therapy: Development of an autologous cancer vaccination therapy (Review)

Reduced expression in immortalized cells (REIC)/Dickkopf (Dkk)-3 is a tumor suppressor and therapeutic gene and has been studied with respect to the application of cancer gene therapy. Our previous studies demonstrated that the intratumoral injection of an adenovirus vector carrying the human REIC/Dkk-3 gene (Ad-REIC) suppresses tumor growth in mouse models of prostate, breast and testicular cancer and malignant mesothelioma. The mechanisms underlying these antitumor therapeutic effects have only been clarified recently. It has been demonstrated that Ad-REIC treatment inhibits cancer progression via the upregulation of systemic anticancer immunity. Under experimental conditions, autologous cancer vaccination via cancer-specific apoptosis and anticancer immune activation is a possible therapeutic mechanism. The robust anticancer effects observed in previous preclinical studies support the clinical utility of Ad-REIC. At present, a phase I–IIa study of Ad-REIC gene therapy in prostate cancer patients is ongoing. The current study reviews the observations of previous fundamental studies and summarizes the anticancer mechanisms of intratumoral Ad-REIC treatment in terms of cancer vaccination.

Dickkopf-related protein 3 promotes pathogenic stromal remodeling in benign prostatic hyperplasia and prostate cancer

BACKGROUND

Compartment-specific epithelial and stromal expression of the secreted glycoprotein Dickkopf-related protein (Dkk)-3 is altered in age-related proliferative disorders of the human prostate. This study aimed to determine the effect of Dkk-3 on prostate stromal remodeling that is stromal proliferation, fibroblast-to-myofibroblast differentiation and expression of angiogenic factors in vitro.

METHODS

Lentiviral-delivered overexpression and shRNA-mediated knockdown of DKK3 were applied to primary human prostatic stromal cells (PrSCs). Cellular proliferation was analyzed by BrdU incorporation ELISA. Expression of Dkk-3, apoptosis-related genes, cyclin-dependent kinase inhibitors and angiogenic factors were analyzed by qPCR, Western blot analysis or ELISA. Fibroblast-to-myofibroblast differentiation was monitored by smooth muscle cell actin and insulin-like growth factor binding protein 3 mRNA and protein levels. The relevance of Wnt/β-catenin and PI3K/AKT signaling pathways was assessed by cytoplasmic/nuclear β-catenin levels and phosphorylation of AKT.

RESULTS

Knockdown of DKK3 significantly attenuated PrSC proliferation as well as fibroblast-to-myofibroblast differentiation and increased the expression of the vessel stabilizing factor angiopoietin-1. DKK3 knockdown did not affect subcellular localization or levels of β-catenin but attenuated AKT phosphorylation in PrSCs. Consistently the PI3K/AKT inhibitor LY294002 mimicked the effects of DKK3 knockdown.

CONCLUSIONS

Dkk-3 promotes fibroblast proliferation and myofibroblast differentiation and regulates expression of angiopoietin-1 in prostatic stroma potentially via enhancing PI3K/AKT signaling. Thus, elevated Dkk-3 in the stroma of the diseased prostate presumably regulates stromal remodeling by enhancing proliferation and differentiation of stromal cells and contributing to the angiogenic switch observed in BPH and PCa. Therefore, Dkk-3 represents a potential therapeutic target for stromal remodeling in BPH and PCa.

Dickkopf-3 function in the prostate: implications for epithelial homeostasis and tumor progression

The tumor suppressor Dickkopf-3 (Dkk-3) is rather a unique molecule. Although it is related to the Dickkopf family of secreted Wnt antagonists, it does not directly inhibit Wnt signaling, and its function and mechanism of action are unknown. Endogenous Dkk-3 was recently found to be required to limit cell proliferation both in the developing mouse prostate and in 3D cultures of human prostate epithelial cells. Dkk-3 was further shown to modulate the response of normal prostate epithelial cells to transforming growth factor-β (TGF-β). These studies are consistent with a model in which Dkk-3 is required by normal cells to prevent the TGF-β switch from tumor suppressor to tumor promoter. Here, we discuss these findings and their potential impact on the development and progression of prostate cancer.