Role of transforming growth factor-beta1 in prostate cancer

Rat Sertoli cells express epithelial but also mesenchymal genes after immortalization with SV40

A new immortal Sertoli cell line from pubertal rat testis was established and characterized. We have generated the clonal line SCIT-C8 expressing established markers for Sertoli cells (SC) like transferrin, clusterin and steel factor/stem cell factor (SCF). Additionally, the immortalized cells express afadin, a protein which is a member of tight and adherens junctions, therefore the cells may be useful for studies of the blood-testis barrier (BTB) in vitro. In contrast to primary SC, the immortalized cells lost expression of androgen receptor and responsiveness to androgens and follicle-stimulating hormone. Surprisingly, we found mRNA expression and protein secretion of the mesenchymal markers, fibronectin and entactin-1, which we also observed for the immortalized SC lines, ASC-17D and 93RS2. In comparison to primary SC, the immortalized cells demonstrated enhanced adhesion in vitro. This correlated with the expression of entactin-1 because adhesion was strongly reduced by antibody perturbation experiments. Additionally, we found the alternatively spliced and primarily muscle cell-specific long variant of TGF-beta2 not only in peritubular cells (PC), but also in the primary and immortalized SC. Furthermore, all immortalized cell lines secreted higher amounts of TGF-beta2 than primary SC. In conclusion, the immortalized SC lines from different developmental stages showed a similar pattern of epithelial and mesenchymal markers.

In vivo real-time imaging of TGF-beta-induced transcriptional activation of the RANK ligand gene promoter in intraosseous prostate cancer

BACKGROUND

Current animal models of prostate cancer (CaP) bone metastasis do not allow measurement of either tumor growth in bone over time or activation of gene promoters in intraosseous tumors. To develop these methods, we used bioluminescent imaging (BLI) to determine if expression of receptor activator of NF-kappaB ligand (RANKL), a pro-osteoclastogenic factor that promotes CaP bone metastases, is modulated by the bone matrix protein transforming growth factor-beta (TGF-beta) in vivo.

METHODS

C4-2B human CaP cells were treated with TGF-beta in vitro and RANKL mRNA and protein production were measured by polymerase chain reaction (PCR) and ELISA, respectively. Then C4-2B cells stably transfected with the RANKL promoter driving luciferase (lux) were injected intra-tibially into severe combined immundeficient (SCID) mice. Tumors were subjected to BLI every 2 weeks for 6 weeks and serum prostate specific antigen (PSA) was measured using ELISA. Vehicle (V), 1,25 dihydroxyvitamin D (VitD), or TGF-beta was administered to mice with established tumors and BLI to measure RANKL promoter activity was performed. Tumors were then subjected to immunohistochemistry for lux and assayed for RANKL mRNA levels.

RESULTS

TGF-beta induced RANKL protein and mRNA expression and activated the RANKL promoter activity in a dose-dependent manner in vitro. BLI demonstrated an increase in intraosseous tumor size over time, which correlated with serum PSA levels. Administration of TGF-beta and VitD to mice with established intraosseous tumors increased lux activity compared to V. Intratibial tumor RANKL mRNA expression paralleled the increased promoter activity. Immunohistochemistry confirmed the presence of lux in the intraosseous tumors.

CONCLUSIONS

These results demonstrate the ability to measure intraosseous tumor growth over time and gene promoter activation in an established intraosseous tumor in vivo and also demonstrate that TGF-beta induces activates the RANKL promoter. These results provide a novel method to explore the biology of CaP bone metastases.

A Gain of Function TGFB1 Polymorphism May Be Associated With Late Stage Prostate Cancer

Transforming growth factor β (TGFβ) is known to exert both positive and negative effects on different stages of tumor formation. Of the TGFβisoforms, TGFβ1 is highly expressed in prostate cancer and leads to tumor promotion and metastasis. Increased expression of TGFβ1 is associated with more aggressive tumors and poor prognosis. Several polymorphisms in TGFB1 have been identified, and two variants in strong linkage disequilibrium, C−509T and T+29C, show increased serum levels. Because of the potential role of TGFB1 variants in prostate cancer and progression, we hypothesized that these two TGFB1 variants would be associated with prostate cancer risk, particularly later, more aggressive stage tumors. To test this, we conducted a nested case-control study of 492 men diagnosed with prostate cancer from the Physicians Health Study and 492 age-matched controls. In this study, cases who were homozygous for the T allele at position −509 had a 2.4-fold increased risk of more advanced stage of prostate cancer [95% confidence interval (95% CI) 1.03–5.43; P = 0.04]. The T allele frequencies in cases and controls were 32.7% and 31.4%, respectively. The same polymorphism showed a 1.23 nonsignificant odds ratio (OR) for overall prostate cancer risk (95% CI 0.80–1.87). Cases who were homozygous for the C allele at position +29 did not show any significant increase in risk for either total prostate cancer (OR 1.19, 95% CI 0.82–1.74) or advanced stage prostate cancer (OR 1.33, 95% CI 0.66–2.68). The C allele frequency in cases and controls were 39.9% and 38.5%, respectively. Our data suggest that the TGFB1 C−509T variant that affects expression of TGFβ1 may play a role in advanced stage prostate cancer.

Secreted transforming growth factor beta2 activates NF-kappaB, blocks apoptosis, and is essential for the survival of some tumor cells

The basis of constitutive activation of NF-kappaB, essential for survival and resistance to apoptosis in many tumors, is not well understood. We find that transforming growth factor beta2 (TGFbeta2), predominantly in its latent form, is secreted by several different types of tumor cell lines that exhibit constitutively active NF-kappaB and that TGFbeta2 potently stimulates the activation of NF-kappaB in reporter cells. Suppression of TGFbeta2 expression by small interfering RNA kills prostate cancer PC3 cells, indicating that the TGFbeta2-NF-kappaB pathway is important for their viability. These findings identify TGFbeta2 as a potential target for therapeutic strategies to inhibit the growth of tumor cells that depend on constitutively active NF-kappaB, or to sensitize them to treatment with cytotoxic drugs.

The Cytoskeleton Differentially Localizes the Early Growth Response Gene-1 Protein in Cancer and Benign Cells of the Prostate

Prostate cancer is the most prevalent malignancy and the second leading cause of cancer mortality in men. Early growth response gene-1 (EGR-1) plays a crucial role in the development and progression of prostate cancer. The presented data show that EGR-1 differs in cellular localization in benign cells compared with malignant prostate cells and that this localization is critical for the transcriptional activation of EGR-1-dependent genes. Immunohistochemistry of human prostate cancer specimens demonstrated higher levels of EGR-1 in malignant cells located predominantly in the cytoplasm, whereas benign cells contained lower levels of EGR-1 located predominantly in the nucleus. Benign prostate cells responded to mitogens in vitro, with increased levels of EGR-1, rapid nuclear translocation, and enhanced transcriptional activity, whereas malignant prostate cells did not exhibit the same responses, and the protein remained in the cytoplasm. The central aspect of this difference is the association of EGR-1 with microtubules, which is exclusive to the benign cells of the prostate and is requisite for the nuclear translocation and transcriptional activity of EGR-1. Our in vitro data demonstrate that the differences in EGR-1 between benign and malignant prostate cells extend beyond cellular levels, which was confirmed by immunohistochemistry in human tissues. Thus, we add the novel concept that microtubules regulate EGR-1 localization in benign prostate cells but not in malignant prostate cells.

Egr1 promotes growth and survival of prostate cancer cells. Identification of novel Egr1 target genes

In the majority of aggressive tumorigenic prostate cancer cells, the transcription factor Egr1 is overexpressed. We provide new insights of Egr1 involvement in proliferation and survival of TRAMP C2 prostate cancer cells by the identification of several new target genes controlling growth, cell cycle progression, and apoptosis such as cyclin D2, P19ink4d, and Fas. Egr1 regulation of these genes, identified by Affymetrix microarray, was confirmed by real-time PCR, immunoblot, and chromatin immunoprecipitation assays. Furthermore we also showed that Egr1 is responsible for cyclin D2 overexpression in tumorigenic DU145 human prostate cells. The regulation of these genes by Egr1 was demonstrated using Egr1 antisense oligonucleotides that further implicated Egr1 in resistance to apoptotic signals. One mechanism was illustrated by the ability of Egr1 to inhibit CD95 (Fas/Apo) expression, leading to insensitivity to FasL. The results provide a mechanistic basis for the oncogenic role of Egr1 in TRAMP C2 prostate cancer cells.

Proprotein convertases regulate activity of prostate epithelial cell differentiation markers and are modulated in human prostate cancer cells

Prostate derived factor (PDF) is a member of transforming growth factor-beta (TGF-beta) superfamily proteins involved in differentiation of the prostate epithelium. Proprotein convertases (PCs) such as furin are thought to mediate the processing of TGF-beta superfamily. In the present study, we demonstrated for the first time that human prostate cancer cell lines differentially synthesize and secret prostate derived factor (PDF), and that PDF secreted by LNCaP is processed by PCs. Exposure of LNCaP cells to the decanoyl-Arg-Val-Lys-Arg-chloromethylketone (CMK), a synthetic furin-like protease inhibitor, inhibited PDF processing and resulted in the loss of luminal cell phenotype and induction of basal cell phenotype in LNCaP cells as demonstrated by alternations in the expression of cytokeratins 8, 14, 18, and 19, markers of prostate epithelial cell differentiation. These results suggest that proprotein convertases may be involved in the regulation of prostate epithelial cell differentiation, and may be an important target of prostate cancer therapy.

Bone growth factors in maxillofacial skeletal reconstruction

A literature review was performed to survey the available information on the potential of bone growth factors in skeletal reconstruction in the maxillofacial area. The aim of this review was to characterize the biological and developmental nature of the growth factors considered, their molecular level of activity and their osteogenic potential in craniofacial bone repair and reconstruction. A total of 231 references were selected for evaluation by the content of the abstracts. All growth factors considered have a fundamental role in growth and development. In postnatal skeletal regeneration, PDGF plays an important role in inducing proliferation of undifferentiated mesenchymal cells. It is an important mediator for bone healing and remodelling during trauma and infection. It can enhance bone regeneration in conjunction with other growth factors but is unlikely to provide entirely osteogenic properties itself. IGFs have an important role in general growth and maintenance of the body skeleton. The effect of local application of IGFs alone in craniofacial skeletal defects has not yet shown a clear potential for enhancement of bone regeneration in the reported dosages. The combination of IGF-I with PDGF has been effective in promoting bone regeneration in dentoalveolar defects around implants or after periodontal bone loss. TGFbeta alone in skeletal reconstruction appears to be associated with uncertain results. The presence of committed cells is required for enhancement of bone formation by TGFbeta. It has a biphasic effect, which suppresses proliferation and osteoblastic differentiation at high concentrations. BMPs, BMP2, BMP4 and BMP7 in particular, appear to be the most effective growth factors in terms of osteogenesis and osseous defect repair. Efficacy of BMPs for defect repair is strongly dependent on the type of carrier and has been subject to unknown factors in clinical feasibility trials resulting in ambiguous results. The current lack of clinical data may prolong the period until this factor is introduced into routine clinical application. PRP is supposed to increase proliferation of undifferentiated mesenchymal cells and to enhance angiogenesis. There is little scientific evidence about the benefit of PRP in skeletal reconstructive and preprosthetic surgery yet and it is unlikely that peri-implant bone healing or regeneration of local bone into alloplastic material by the application of PRP alone will be significantly enhanced.

Transforming growth factor-beta 2 heterozygous mutant mice exhibit Cowper's gland hyperplasia and cystic dilations of the gland ducts (Cowper's syringoceles)

Analyses of mutant mice with a deletion for the transforming growth factor beta 2 (Tgfbeta2) gene revealed cysts in the perineal/scrotal region of male mice. We present evidence from in situ, light and electron microscopy that the cysts observed in Tgfbeta2+/- heterozygous mice males derive from Cowper's gland tissue. The Cowper's glands of Tgfbeta2+/- heterozygous mutant mice display all steps of glandular hyperplasia and cystic dilation. TGF-beta isoforms and TGF-beta receptor (TbetaR-II) were localized immunocytochemically in sections of Cowper's glands. TGF-beta2 and TGF-beta3 were located predominantly in myoepithelial cells of the Cowper's gland whereas the TbetaRII was found in the plasma membrane of the acinar cells. TUNEL-assays revealed that apoptotic cell death is significantly reduced in Cowper's glands of TgfbetaB2+/- heterozygous mutant mice. The fact that Tgfbeta2+/- heterozygous mutant mice exhibit hyperplasia of Cowper's gland epithelium and Cowper's gland cysts suggests a disturbance of epithelial-stromal interaction most likely due to reduced TGF-beta2 level, accompanied by a significant decrease in apoptosis.

Endoglin (CD105) is expressed on immature blood vessels and is a marker for survival in prostate cancer

BACKGROUND

Endoglin, a receptor for some of the members of the transforming growth factor-beta (TGF-beta) family, is expressed on proliferating endothelial cells and has been suggested as a marker of ongoing angiogenesis. In this study, endoglin was evaluated as a prognostic factor for prostate cancer progression.

METHODS

Immunohistochemical staining of endoglin was examined in 72 cases of prostate cancer and compared with immunohistochemical staining of the pan-endothelial marker von Willebrand factor (vWf), clinicopathological factors, and cancer-specific survival. Micro-vessels were measured in the most vascularized fields. Double staining with antibodies against smooth muscle actin and endoglin or vWf, respectively, was performed in order to evaluate vessel maturation.

RESULTS

Endoglin-stained tumor vessels were generally small and only 19% also stained with actin. Endoglin was a better prognostic marker than vWf. The median survival times were shorter for patients with tumor vascular count (vc) above median than for patients with vc below median (4 vs. 12 years, P = 0.0007, and 5 vs. 10 years, P = 0.018, for endoglin and vWf, respectively). Endoglin vc was associated with Gleason score (P = 0.001), local tumor stage (P = 0.0006), metastasis (P = 0.01), tumor cell immunoreactivity for TGF-beta1 (P = 0.0003), and tumor cell proliferation index (r(s) = 0.319, P = 0.02). Endoglin, in contrast to vWf, vc was prognostic for survival in the subgroup of patients with Gleason score 5, 6, and 7 tumors.

CONCLUSIONS

Endoglin marks principally small, probably newly formed tumor vessels in zthe prostate, and is a promising prognostic marker for prostate cancer patients.

The androgen receptor represses transforming growth factor-beta signaling through interaction with Smad3

In the prostate, androgens negatively regulate the expression of transforming growth factor-beta (TGF-beta) ligands and receptors and Smad activation through unknown mechanisms. We show that androgens (dihydrotestosterone and R1881) down-regulate TGF-beta1-induced expression of TGF-beta1, c-Fos, and Egr-1 in the human prostate adenocarcinoma cell line, LNCaP. Moreover, 5alpha-dihydrotestosterone (DHT) inhibits TGF-beta1 activation of three TGF-beta1-responsive promoter constructs, 3TP-luciferase, AP-1-luciferase, and SBE4(BV)-luciferase, in LNCaP cells either with or without enforced expression of TGF-beta receptors (TbetaRI and TbetaRII). Similarly, DHT inhibits the activation of Smad-binding element (SBE)4(BV)-luciferase by either constitutively activated TbetaRI (T204D) or constitutively activated Smad3 (S3*). Activation of SBE4(BV)-luciferase by S3* in the NRP-154 prostatic cell line, which is androgen receptor (AR)-negative but highly responsive to TGF-beta1, is blocked by co-transfection with either full-length AR or AR missing the DNA binding domain. Immunoprecipitation and GST pull-down assays show that AR directly associates with Smad3 but not Smad2 or Smad4. Electrophoretic mobility shift assays indicate that the AR ligand binding domain directly inhibits the association of Smad3 to the Smad-binding element. In conclusion, our data demonstrate for the first time that ligand-bound AR inhibits TGF-beta transcriptional responses through selectively repressing the binding of Smad3 to SBE.