Thrombospondin-1, vascular endothelial growth factor expression and their relationship with p53 status in prostate cancer and benign prostatic hyperplasia

Thrombospondin 1 and cathepsin D improve prostate cancer diagnosis by avoiding potentially unnecessary prostate biopsies

Objectives

To investigate and further validate if two novel cancer‐related glycoproteins, discovered by a genetic‐guided proteomics approach, can distinguish benign disease from prostate cancer (PCa) in men with enlarged prostates.

Patients and Methods

A retrospective study was performed that included men with a total prostate‐specific antigen (PSA) concentration of 2.0–10 ng/mL, negative digital rectal examination and enlarged prostate (volume ≥35 mL). Serum samples were collected between 2011 and 2016 at a single centre from 474 men before they underwent prostate biopsy. Serum concentrations of thrombospondin 1 (THBS1) and cathepsin D (CTSD) glycoproteins were combined with the percentage of free PSA to total PSA ratio (%fPSA) to predict any or significant cancer at biopsy.

Results

The multivariable logistic regression model including THBS1, CTSD and %fPSA discriminated among biopsy‐positive and biopsy‐negative patients in the validation set with an area under the curve (AUC) of 0.86 (P < 0.001, 95% confidence interval (CI) 0.82–0.91), while %fPSA alone showed an AUC of 0.64 (P < 0.001, 95% CI 0.57–0.71). At 90% sensitivity for PCa, the specificity of the model was 62%, while %fPSA had a specificity of 23%. For high grade (Gleason score ≥ 7 in prostatectomy specimen) PCa, the specificity was 48% at 90% sensitivity, with an AUC of 0.83, (P < 0.001, 95% CI 0.77 to 0.88). Limitations of the study include the retrospective set‐up and single‐centre cohort.

Conclusions

A model combining two cancer‐related glycoproteins (THBS1 and CTSD) and %fPSA can improve PCa diagnosis and may reduce the number of unnecessary prostate biopsies because of its improved specificity for PCa when compared to %fPSA alone.

Human expression patterns: qualitative and quantitative analysis of thrombospondin-1 under physiological and pathological conditions

Thrombospondin-1 (TSP-1), a matricellular protein and one of the first endogenous anti-angiogenic molecules identified, has long been considered a potent modulator of human diseases. While the therapeutic effect of TSP-1 to suppress cancer was investigated in both research and clinical settings, the mechanisms of how TSP-1 is regulated in cancer remain elusive, and the scientific answers to the question of whether TSP-1 expressions can be utilized as diagnostic or prognostic marker for patients with cancer are largely inconsistent. Moreover, TSP-1 plays crucial functions in angiogenesis, inflammation and tissue remodelling, which are essential biological processes in the progression of many cardiovascular diseases, and therefore, its dysregulated expressions in such conditions may have therapeutic significance. Herein, we critically analysed the literature pertaining to TSP-1 expression in circulating blood and pathological tissues in various types of cancer as well as cardiovascular and inflammation-related diseases in humans. We compare the secretion rates of TSP-1 by different cancer and non-cancer cells and discuss the potential connection between the expression changes of TSP-1 and vascular endothelial growth factor (VEGF) observed in patients with cancer. Moreover, the pattern and emerging significance of TSP-1 profiles in cardiovascular disease, such as peripheral arterial disease, diabetes and other related non-cancer disorders, are highlighted. The analysis of published TSP-1 data presented in this review may have implications for the future exploration of novel TSP-1-based treatment strategies for cancer and cardiovascular-related diseases.

Development and clinical testing of individual immunoassays for the quantification of serum glycoproteins to diagnose prostate cancer

Prostate Cancer (PCa) diagnosis is currently hampered by the high false-positive rate of PSA evaluations, which consequently may lead to overtreatment. Non-invasive methods with increased specificity and sensitivity are needed to improve diagnosis of significant PCa. We developed and technically validated four individual immunoassays for cathepsin D (CTSD), intercellular adhesion molecule 1 (ICAM1), olfactomedin 4 (OLFM4), and thrombospondin 1 (THBS1). These glycoproteins, previously identified by mass spectrometry using a Pten mouse model, were measured in clinical serum samples for testing the capability of discriminating PCa positive and negative samples. The development yielded 4 individual immunoassays with inter and intra-variability (CV) <15% and linearity on dilution of the analytes. In serum, ex vivo protein stability (<15% loss of analyte) was achieved for a duration of at least 24 hours at room temperature and 2 days at 4°C. The measurement of 359 serum samples from PCa positive (n = 167) and negative (n = 192) patients with elevated PSA (2-10 ng/ml) revealed a significantly improved accuracy (P <0.001) when two of the glycoproteins (CTSD and THBS1) were combined with %fPSA and age (AUC = 0.8109; P <0.0001; 95% CI = 0.7673-0.8545). Conclusively, the use of CTSD and THBS1 together with commonly used parameters for PCa diagnosis such as %fPSA and age has the potential to improve the diagnosis of PCa.

FGF7/FGFR2 signal promotes invasion and migration in human gastric cancer through upregulation of thrombospondin-1

Fibroblast growth factor 7 (FGF7) is a mesenchyme-specific heparin-binding growth factor that binds FGF receptor 2 (FGFR2) to regulate numerous cellular and physiological processes. FGF7/FGFR2 signal is associated with gastric cancer progression. In the present study, we investigated the molecular mechanism by which FGF7/FGFR2 promotes invasion and migration in human gastric cancer. We first demonstrated that increased FGFR2 expression in human gastric cancer tissues was significantly associated with tumor depth and clinical stage in human gastric cancer tissues. Thrombospondin 1 (THBS1) is an extracellular glycoprotein that plays multiple roles in cell-matrix and cell-cell interactions. Increased expression of THBS1 significantly correlated with tumor differentiation. FGFR2 and THBS1 expression were both increased in cancer tissues as compared with adjacent normal tissues and their expression was positively correlated. In vitro, FGF7 stimulation of cell invasion and migration was partially suppressed by the FGFR2 knockdown. In addition, FGF7/FGFR2 upregulated THBS1, and cell invasion and migration were decreased by knockdown of THBS1. Furthermore, the PI3K/Akt/mTOR signaling pathway was predominantly responsible for FGF7/FGFR2-induced THBS1 upregulation. Taken together, our data suggest that FGF7/FGFR2/THBS1 is associated with the regulation of invasion and migration in human gastric cancer.

Expression and localization of members of the thrombospondin family during final follicle maturation and corpus luteum formation and function in the bovine ovary

The aim of this study was to characterize the expression patterns and localization of the thrombospondin family members (THBS1, THBS2) and their receptors (CD36 and CD47) in bovine ovaries. First, the antral follicles were classified into 5 groups based on the follicle size and estradiol-17beta (E2) concentration in the follicular fluid (< 0.5, 0.5-5, 5-40, 40-180 and >180 E2 ng/ml). Second, the corpus luteum (CL) was assigned to the following stages: days 1-2, 3-4, 5-7, 8-12, 13-16 and >18 of the estrous cycle and of pregnancy (month 1-2, 3-4, 6-7 and > 8). Third, the corpora lutea were collected by transvaginal ovariectomy before and 0.5, 2, 4, 12, 24, 48 and 64 h after inducing luteolysis by injecting a prostaglandin F2alpha analog. The mRNA expression of examined factors was measured by RT-qPCR, steroid hormone concentration by EIA, and localization by immunohistochemistry. The mRNA expression of THBS1, THBS2, CD36, and CD47 in the granulosa cells and theca interna was high in the small follicles and reduced in the preovulatory follicles. The mRNA expression of THBS1, THBS2, and CD47 in the CL during the estrous cycle was high, but decreased significantly during pregnancy. After induced luteolysis, thrombospondins increased significantly to reach the maximum level at 12 h for THBS1, 24 h for THBS2, and 48 h for CD36. The temporal expression and localization pattern of the thrombospondins and their specific receptors in the antral follicles and corpora lutea during the different physiological phases of the estrous cycle and induced luteolysis appear to be compatible with their inhibitory role in the control of ovarian angiogenesis.

PSMA, EpCAM, VEGF and GRPR as imaging targets in locally recurrent prostate cancer after radiotherapy

In this retrospective pilot study, the expression of the prostate-specific membrane antigen (PSMA), the epithelial cell adhesion molecule (EpCAM), the vascular endothelial growth factor (VEGF) and the gastrin-releasing peptide receptor (GRPR) in locally recurrent prostate cancer after brachytherapy or external beam radiotherapy (EBRT) was investigated, and their adequacy for targeted imaging was analyzed. Prostate cancer specimens were collected of 17 patients who underwent salvage prostatectomy because of locally recurrent prostate cancer after brachytherapy or EBRT. Immunohistochemistry was performed. A pathologist scored the immunoreactivity in prostate cancer and stroma. Staining for PSMA was seen in 100% (17/17), EpCAM in 82.3% (14/17), VEGF in 82.3% (14/17) and GRPR in 100% (17/17) of prostate cancer specimens. Staining for PSMA, EpCAM and VEGF was seen in 0% (0/17) and for GRPR in 100% (17/17) of the specimens’ stromal compartments. In 11.8% (2/17) of cases, the GRPR staining intensity of prostate cancer was higher than stroma, while in 88.2% (15/17), the staining was equal. Based on the absence of stromal staining, PSMA, EpCAM and VEGF show high tumor distinctiveness. Therefore, PSMA, EpCAM and VEGF can be used as targets for the bioimaging of recurrent prostate cancer after EBRT to exclude metastatic disease and/or to plan local salvage therapy.

Development of a reactive stroma associated with prostatic intraepithelial neoplasia in EAF2 deficient mice

ELL-associated factor 2 (EAF2) is an androgen-responsive tumor suppressor frequently deleted in advanced prostate cancer that functions as a transcription elongation factor of RNA Pol II through interaction with the ELL family proteins. EAF2 knockout mice on a 129P2/OLA-C57BL/6J background developed late-onset lung adenocarcinoma, hepatocellular carcinoma, B-cell lymphoma and high-grade prostatic intraepithelial neoplasia. In order to further characterize the role of EAF2 in the development of prostatic defects, the effects of EAF2 loss were compared in different murine strains. In the current study, aged EAF2^−/− mice on both the C57BL/6J and FVB/NJ backgrounds exhibited mPIN lesions as previously reported on a 129P2/OLA-C57BL/6J background. In contrast to the 129P2/OLA-C57BL/6J mixed genetic background, the mPIN lesions in C57BL/6J and FVB/NJ EAF2^−/− mice were associated with stromal defects characteristic of a reactive stroma and a statistically significant increase in prostate microvessel density. Stromal inflammation and increased microvessel density was evident in EAF2-deficient mice on a pure C57BL/6J background at an early age and preceded the development of the histologic epithelial hyperplasia and neoplasia found in the prostates of older EAF2^−/− animals. Mice deficient in EAF2 had an increased recovery rate and a decreased overall response to the effects of androgen deprivation. EAF2 expression in human cancer was significantly down-regulated and microvessel density was significantly increased compared to matched normal prostate tissue; furthermore EAF2 expression was negatively correlated with microvessel density. These results suggest that the EAF2 knockout mouse on the C57BL/6J and FVB/NJ genetic backgrounds provides a model of PIN lesions associated with an altered prostate microvasculature and reactive stromal compartment corresponding to that reported in human prostate tumors.

Thrombospondin-1 in urological cancer: pathological role, clinical significance, and therapeutic prospects

Angiogenesis is an important process for tumor growth and progression of various solid tumors including urological cancers. Thrombospondins (TSPs), especially TSP-1, are representative “anti”-angiogenic molecules and many studies have clarified their pathological role and clinical significance in vivo and in vitro. In fact, TSP-1 expression is associated with clinicopathological features and prognosis in many types of cancers. However, TSP-1 is a multi-functional protein and its biological activities vary according to the specific tumor environments. Consequently, there is no general agreement on its cancer-related function in urological cancers, and detailed information regarding regulative mechanisms is essential for a better understanding of its therapeutic effects and prognostic values. Various “suppressor genes” and “oncogenes” are known to be regulators and TSP-1-related factors under physiological and pathological conditions. In addition, various types of fragments derived from TSP-1 exist in a given tissue microenvironment and TSP-1 derived-peptides have specific activities. However, a detailed pathological function in human cancer tissues is not still understood. This review will focus on the pathological roles and clinical significance of TSP-1 in urological cancers, including prostate cancer, renal cell carcinoma, and urothelial cancer. In addition, special attention is paid to TSP-1-derived peptide and TSP-1-based therapy for malignancies.

Vascular endothelial growth factor (VEGF) expression in locally advanced prostate cancer: secondary analysis of radiation therapy oncology group (RTOG) 8610

Background

Angiogenesis is a key element in solid-tumor growth, invasion, and metastasis. VEGF is among the most potent angiogenic factor thus far detected. The aim of the present study is to explore the potential of VEGF (also known as VEGF-A) as a prognostic and predictive biomarker among men with locally advanced prostate cancer.

Methods

The analysis was performed using patients enrolled on RTOG 8610, a phase III randomized control trial of radiation therapy alone (Arm 1) versus short-term neoadjuvant and concurrent androgen deprivation and radiation therapy (Arm 2) in men with locally advanced prostate carcinoma. Tissue samples were obtained from the RTOG tissue repository. Hematoxylin and eosin slides were reviewed, and paraffin blocks were immunohistochemically stained for VEGF expression and graded by Intensity score (0–3). Cox or Fine and Gray’s proportional hazards models were used.

Results

Sufficient pathologic material was available from 103 (23%) of the 456 analyzable patients enrolled in the RTOG 8610 study. There were no statistically significant differences in the pre-treatment characteristics between the patient groups with and without VEGF intensity data. Median follow-up for all surviving patients with VEGF intensity data is 12.2 years. Univariate and multivariate analyses demonstrated no statistically significant correlation between the intensity of VEGF expression and overall survival, distant metastasis, local progression, disease-free survival, or biochemical failure. VEGF expression was also not statistically significantly associated with any of the endpoints when analyzed by treatment arm.

Conclusions

This study revealed no statistically significant prognostic or predictive value of VEGF expression for locally advanced prostate cancer. This analysis is among one of the largest sample bases with long-term follow-up in a well-characterized patient population. There is an urgent need to establish multidisciplinary initiatives for coordinating further research in the area of human prostate cancer biomarkers.

Non-steroidal anti-inflammatory drugs for lower urinary tract symptoms in benign prostatic hyperplasia: systematic review and meta-analysis of randomized controlled trials

OBJECTIVE

To assess the effects of non-steroidal anti-inflammatory drugs (NSAIDs) in men with benign prostatic hyperplasia (BPH) using systematic review and meta-analysis of clinical trials.

SUBJECTS

Men treated with NSAIDs in comparison with placebo or other BPH medications.

METHODS

All aspects of the Preferred Reporting for Systematic Reviews and Meta-Analyses (PRISMA) statement were followed. Trials were eligible for inclusion provided they (i) randomized men with BPH to receive NSAIDs in comparison with placebo or other BPH medications, and (ii) included clinical outcomes such as urological symptom scales, symptoms or urodynamic measurements. Data analysis was performed using REVIEW MANAGER Version 5.0 software. Study weight was calculated by the inverse variances of the study effect estimates.

RESULTS

In all, 183 men from three randomized, placebo-controlled trials (lasting 4-24 weeks) were assessed. NSAIDs improved urinary symptom scores and flow measures. The weighted mean difference for the International Prostate Symptom Score (IPSS) was -2.89 IPSS points (95% CI -3.84 to -1.95, P < 0.001, n = 3 studies). The weighted mean difference for peak urine flow was 0.89 mL/s (95% CI 0.21-1.58, P = 0.01, n = 3 studies) and for reported adverse effects was 1.51 (95% CI 0.66-3.43, P = 0.32, n = 3 studies,). All patients assigned to NSAIDs continued the treatment. There were no serious adverse effects and there were no withdrawals or losses to follow-up.

CONCLUSION

The evidence suggests that NSAIDs improve urinary symptoms and flow measures. Their long-term effectiveness, safety and ability to prevent BPH complications are not known.

Gene Expression Profiling Reveals Regulation of ERK Phosphorylation by Androgen-Induced Tumor Suppressor U19/EAF2 in the Mouse Prostate

U19/EAF2 is regulated by androgens in the prostate and capable of regulating transcriptional elongation of RNA Pol II via interaction with the ELL family proteins. Inactivation of U19/EAF2 induces tumorigenesis in multiple organs; however the mechanism of U19/EAF2 tumor suppression remains unclear. To elucidate potential mechanisms of U19/EAF2 action, we performed cDNA microarray analysis and identified 164 mRNA transcripts regulated by U19/EAF2 in the mouse ventral prostate. Bioinformatics analysis indicated that U19/EAF2 knockout activates the RAS-BRAF-ERK signaling pathway, which is known to play important roles in carcinogenesis. qPCR verified increased expression of BRAF mRNA, and immunostaining and Western blot analysis demonstrated increased expression of p-ERK at the protein level suggested U19/EAF2 knockout activates this important pathway. These findings indicate that loss of EAF2 up-regulates transcription of RAS cascade genes including Grb2, PI3K, and BRAF, leading to elevated p-ERK levels, which may represent a major functional role of U19/EAF2 in the prostate. Furthermore, these observations suggest that U19/EAF2 is a key player in crosstalk between androgen receptor and the RAS-BRAF-ERK signaling pathway.

β-blockers: a novel class of antitumor agents

β-adrenergic signaling modulates key signaling pathways that are important for tumor-promoting processes, and numerous mechanisms of action have been elucidated. Preclinical studies have demonstrated that β-adrenergic antagonists, or β-blockers, can block multiple fundamental biologic processes underlying the progression and metastasis of tumors, including the inhibition of cell proliferation, migration, invasion, resistance to programmed cell death, and tumor angiogenesis and metastasis. Human pharmacoepidemiologic studies suggest that β-blockers have a role in inhibiting cancer progression and metastasis in combination with standard therapies. Furthermore, a number of prospective studies have demonstrated that β-blockers are effective at halting infantile hemangioma growth. These findings shed light on the novel perspective of using β-blockers as a class of potential antitumor agents in clinical oncology.

VEGF/neuropilin-2 regulation of Bmi-1 and consequent repression of IGF-IR define a novel mechanism of aggressive prostate cancer

We show that the VEGF receptor neuropilin-2 (NRP2) is associated with high-grade, PTEN-null prostate cancer and that its expression in tumor cells is induced by PTEN loss as a consequence of c-Jun activation. VEGF/NRP2 signaling represses insulin-like growth factor-1 receptor (IGF-IR) expression and signaling, and the mechanism involves Bmi-1-mediated transcriptional repression of the IGF-IR. This mechanism has significant functional and therapeutic implications that were evaluated. IGF-IR expression positively correlates with PTEN and inversely correlates with NRP2 in prostate tumors. NRP2 is a robust biomarker for predicting response to IGF-IR therapy because prostate carcinomas that express NRP2 exhibit low levels of IGF-IR. Conversely, targeting NRP2 is only modestly effective because NRP2 inhibition induces compensatory IGF-IR signaling. Inhibition of both NRP2 and IGF-IR, however, completely blocks tumor growth in vivo.

Anti-angiogenesis effect of 3'-sulfoquinovosyl-1'-monoacylglycerol via upregulation of thrombospondin 1

We previously reported that 3'-sulfoquinovosyl-1'-monoacylglycerol (SQMG) effectively suppresses the growth of solid tumors, likely via its anti-angiogenic activity. To investigate how SQMG affects angiogenesis, we performed DNA microarray analysis and quantitative real-time polymerase chain reaction. Consequently, upregulation of thrombospondin 1 (TSP-1) in SQMG-treated tumors in vitro and in vivo was confirmed. To address the mechanisms of TSP-1 upregulation by SQMG, we established stable TSP-1-knockdown transformants (TSP1-KT) by short hairpin RNA induction and performed reporter assay and in vivo assessment of anti-tumor assay. On the reporter assay, transcriptional upregulation of TSP-1 in TSP1-KT could not be induced by SQMG, thus suggesting that TSP-1 upregulation by SQMG occurred via TSP-1 molecule. In addition, growth of TSP1-KT xenografted tumors in vivo was not inhibited by SQMG, thus suggesting that anti-angiogenesis via TSP-1 upregulation induced by SQMG did not occur, as the SQMG target molecule TSP-1 was knocked down in TSP1-KT transformants. These data provide that SQMG is a promising candidate for the treatment of tumor-induced angiogenesis via TSP-1 upregulation.

Thrombospondin-1 triggers cell migration and development of advanced prostate tumors

The antitumor effects of pharmacologic inhibitors of angiogenesis are hampered in patients by the rapid development of tumor resistance, notably through increased invasiveness and accelerated metastasis. Here, we reevaluated the role of the endogenous antiangiogenic thrombospondin 1 (TSP1) in prostate carcinomas in which angiogenesis is an active process. In xenografted tumors, we observed that TSP1 altogether inhibited angiogenesis and fostered tumor development. Our results show that TSP1 is a potent stimulator of prostate tumor cell migration. This effect required CD36, which also mediates TSP1 antiangiogenic activity, and was mimicked by an antiangiogenic TSP1-derived peptide. As suspected for pharmacologic inhibitors of angiogenesis, the TSP1 capacities to increase hypoxia and to trigger cell migration are thus inherently linked. Importantly, although antiangiogenic TSP1 increases hypoxia in vivo, our data show that, in turn, hypoxia induced TSP1, thus generating a vicious circle in prostate tumors. In radical prostatectomy specimens, we found TSP1 expression significantly associated with invasive tumors and with tumors which eventually recurred. TSP1 may thus help select patients at risk of prostate-specific antigen relapse. Together, the data suggest that intratumor disruption of the hypoxic cycle through TSP1 silencing will limit tumor invasion.

Norepinephrine induces VEGF expression and angiogenesis by a hypoxia-inducible factor-1α protein-dependent mechanism

A growing number of studies have demonstrated that physiological factors can influence the progression of several cancers via cellular immune function, angiogenesis and metastasis. Recently, stress-induced catecholamines have been shown to increase the expression of various cancer progressive factors, including vascular endothelial growth factor (VEGF), matrix metalloproteinases and interleukins. However, a detailed mechanism remains to be identified. In this study, we investigated the role of adrenergic receptors and hypoxia-inducible factor (HIF)-1α protein in catecholamine-induced VEGF expression and angiogenesis. Treatment of the cells with norepinephrine (NE) or isoproterenol induced VEGF expression and HIF-1α protein amount in a dose-dependent manner. Induction of VEGF expression by NE was abrogated when the cells were transfected with HIF-1α-specific siRNA. Similarly, adenylate cyclase activator forskolin and cyclic AMP-dependent protein kinase A inhibitor H-89 enhanced and decreased HIF-1α protein amount, respectively. More importantly, conditioned medium of NE-stimulated cancer cells induced angiogenesis in a HIF-1α protein-dependent manner. In addition, pretreatment of cells with propranolol, a β-adrenergic receptor (AR) blocker, completely abolished induction of VEGF expression and HIF-1α protein amount by NE in all of the tested cancer cells. However, treatment with the α1-AR blocker prazosin inhibited NE-induced HIF-1α protein amount and angiogenesis in SK-Hep1 and PC-3 but not MDA-MB-231 cells. Collectively, our results suggest that ARs and HIF-1α protein have critical roles in NE-induced VEGF expression in cancer cells, leading to stimulation of angiogenesis. These findings will help to understand the mechanism of cancer progression by stress-induced catecholamines and design therapeutic strategies for cancer angiogenesis.

Thrombospondin-1 regulates the normal prostate in vivo through angiogenesis and TGF-beta activation

Castration experiments in rodents show that the stromal vasculature is critical to the androgen-mediated prostate growth regulation. However, the role of angiogenesis inhibitors, such as thrombospondin-1 (TSP-1), in this process is unclear. TSP-1 is a multifunctional glycoprotein that can function as a potent angiogenesis inhibitor and an in vivo activator of latent transforming growth factor-beta (TGF-beta) in some tissues. On the basis of these observations, we hypothesized that TSP-1 regulated androgen withdrawal-induced prostate regression and that this process was mediated not only through antiangiogenic activity but also through TGF-beta activation. To test this, we evaluated angiogenic activity in human prostate epithelial and stromal cells treated with androgens and hypoxia in vitro. TSP-1 knockout mice were characterized to investigate the in vivo functions of TSP-1. In vitro, we found that androgens and hypoxia differentially regulated TSP-1 and angiogenic activity. Androgens stimulated normal epithelial cell, but inhibited normal stromal cell, angiogenic activity. Conversely, hypoxia stimulated stromal while inhibiting epithelial activity. Thus, in vivo, net angiogenic activity must reflect cellular interactions. And, we found that media conditioned by epithelial cells grown under normoxic conditions stimulated stromal cell angiogenic activity, and if epithelial cells were grown under hypoxic conditions, stromal activity was further increased. TSP-1 levels, however, were unchanged. In vivo, TSP-1 loss in a mouse model led to prostate epithelial hyperplasia by 3 months of age with only a modest stromal effect. Androgens suppressed TSP-1 as expression increased after castration both in normal mouse prostate and in human prostate cancer tissues. In addition, TSP-1 expression corresponded to increased TGF-beta activation in mouse tissues, specifically in the stromal compartment. These data show a critical role for TSP-1 in prostate epithelial and stromal growth regulation through angiogenic inhibition and activation of latent TGF-beta. Therefore, loss of TSP-1 during tumorigenesis would eliminate two barriers to cancer progression.

Angiogenesis as a strategic target for prostate cancer therapy

It is becoming increasingly clear that angiogenesis plays a crucial role in prostate cancer (CaP) survival, progression, and metastasis. Tumor angiogenesis is a hallmark of advanced cancers and an attractive treatment target in multiple solid tumors. By understanding the molecular basis of resistance to androgen withdrawal and chemotherapy in CaP, the rational design of targeted therapeutics is possible. This review summarizes the recent advancements that have improved our understanding of the role of angiogenesis in CaP metastasis and the potential therapeutic efficacy of inhibiting angiogenesis in this disease. Current therapeutic options for patients with metastatic hormone-refractory CaP are very limited. Targeting vasculature is a developing area, which shows promise for the control of late stage and recurrent CaP disease and for overcoming drug resistance. We discuss angiogenesis and its postulated mechanisms and focus on the regulation of angiogenesis in CaP progression and the therapeutic beneficial effects associated with targeting of the CaP vasculature to overcome the resistance to current treatments and CaP recurrence.

Tumor suppressor U19/EAF2 regulates thrombospondin-1 expression via p53

Inactivation of U19/EAF2 has been shown previously to lead to tumorigenesis in multiple organs; however, the mechanism of U19/EAF2 tumor suppression remains unclear. In this paper, we report that the expression of an anti-angiogenic protein, thrombospondin-1 (TSP-1) is down-regulated in the prostate and liver of U19/EAF2 knockout mouse. The U19/EAF2 knockout liver displayed increased CD31-positive blood vessels, suggesting that the TSP-1 down-regulation can contribute to increased angiogenesis. TSP-1 is reported to be a p53-target gene and p53 is a known binding partner of ELL, which binds to U19/EAF2. Here, we show that U19/EAF2 can co-localize and co-immunoprecipitate with p53 in transfected cells. In a TSP-1 promoter-driven luciferase reporter assay, p53 transfection suppressed the TSP-1 promoter activity and U19/EAF2 co-transfection blocked the p53 suppression of TSP-1 promoter. However, U19/EAF2 transfection alone had little or no effect on the TSP-1 promoter. The above observations together suggest that U19/EAF2 regulates the expression of TSP-1 via blocking p53 repression of the TSP-1 promoter.

Beta1 integrin cytoplasmic variants differentially regulate expression of the antiangiogenic extracellular matrix protein thrombospondin 1

Beta(1) integrins play an important role in regulating cell proliferation and survival. Using small interfering RNA or an inhibitory antibody to beta(1), we show here that, in vivo, beta(1) integrins are essential for prostate cancer growth. Among the five known beta(1) integrin cytoplasmic variants, two have been shown to differentially affect prostate cell functions. The beta(1A) variant promotes normal and cancer cell proliferation, whereas the beta(1C) variant, which is down-regulated in prostate cancer, inhibits tumor growth and appears to have a dominant effect on beta(1A). To investigate the mechanism by which beta(1C) inhibits the tumorigenic potential of beta(1A), we analyzed changes in gene expression in cells transfected with either beta(1C) or beta(1A). The results show that beta(1C) expression increases the levels of an extracellular matrix protein, thrombospondin 1 (TSP1), an angiogenesis inhibitor. TSP1 protein levels are increased upon beta(1C) expression in prostate cancer cells as well as in beta(1)-null GD25 cells. We show that TSP1 does not affect proliferation, apoptosis, or anchorage-independent growth of prostate cancer cells. In contrast, the newly synthesized TSP1, secreted by prostate cancer cells expressing beta(1C), prevents proliferation of endothelial cells. In conclusion, our novel findings indicate that expression of the beta(1C) integrin variant in prostate glands prevents cancer progression by up-regulation of TSP1 levels and inhibition of angiogenesis.

Lack of immunohistochemical detection of VEGF in prostate carcinoma

BACKGROUND

Vascular endothelial growth factor (VEGF) has been implicated in tumor angiogenesis and is a potential therapeutic target in prostatic adenocarcinoma (PrCa). Immunohistochemical (IHC) analysis has been used to demonstrate VEGF expression in PrCa, and in various other tumors including breast carcinoma, renal cell carcinoma, hepatocellular carcinoma, and gliomas. Prior studies have reported markedly varied VEGF expression in benign prostatic hyperplasia (0% to 100%) and PrCa (40% to 100%). The objective of this study was to measure VEGF expression in PrCa specimens, using IHC analysis with antibodies from different manufacturers and different antigen retrieval techniques.

DESIGN

Cases were identified from an ongoing study analyzing 1270 cases of PrCa diagnosed at various Veterans Health Administration hospitals in the New England region during 1991 to 1995. From this study population, 50 cases (including 40 biopsies, 8 transurethral resections of prostate, and 2 radical resections) were selected. In all cases, tissues were fixed in 10% formalin and embedded in paraffin. Four different antibodies were used for IHC using indirect peroxidase method. For each antibody, different dilutions and antigen retrieval methods (steam with ethylene diamine tetra-acetate, steam with low pH, water bath with target unmasking fluid, trypsin, proteinase K) were tested. EnVision+ system was used to overcome nonspecific staining. Appropriate positive and negative controls were used.

RESULTS

Using different antibodies, positive staining of varying intensity was seen in benign glands, malignant glands, endothelial cells, and fibromuscular stroma. Some cases showed cytoplasmic and granular staining in prostatic glands. However, the staining disappeared in all cases when EnVision+ system was used to block nonspecific staining except for focal and minimal staining in the endothelial cells.

CONCLUSIONS

Our results show that when nonspecific staining is blocked, no staining is found for VEGF within the prostate, in either benign or malignant glands. The reasons for the granular and nonspecific staining are unclear at present. Our study may help to explain variable results reported in previous studies, and suggests caution in interpreting VEGF expression in studies of PrCa and benign glands.

Increased p53 immunoreactivity in proliferative inflammatory atrophy of prostate is related to focal acute inflammation

Proliferative inflammatory atrophy (PIA) of prostate has been proposed as a precursor lesion of prostate cancer. The aim of the current study was to evaluate the expression of p53 protein in PIA lesions and to investigate the relationship between p53 staining and Ki-67, glutathione S-transferase-pi (GSTP1) and cyclooxygenase-2 (COX-2) immunohistochemical expression. The results revealed that p53 nuclear immunostaining appeared in PIA lesions in 2.1+/-3.4% (mean+/-SD) of the basal and 0.9+/-2.3% of the luminal epithelial cells. Both these values were significantly higher than those in normal-appearing acini (p<0.0001). Increased p53 expression in luminal cells was related to focal infiltration of polymorphonuclear leucocytes. A positive correlation between p53 expression and Ki-67 was found in COX-2-positive PIA lesions (r=0.610, p<0.0001). Half of the p53-positive epithelial cells expressed diffuse GSTP1 immunostaining in the same lesions. The present study demonstrates an increased p53 expression in PIA lesions, and inflammation, especially acute inflammation, may play a role in the induction of p53 over-expression, particularly as cells in PIA lesions are known to have a reduced defence against DNA damage.

Androgenic dependence of exophytic tumor growth in a transgenic mouse model of bladder cancer: a role for thrombospondin-1

BACKGROUND

Steroid hormones influence mitogenic signaling pathways, apoptosis, and cell cycle checkpoints, and it has long been known that incidence of bladder cancer (BC) in men is several times greater than in women, a difference that cannot be attributed to environmental or lifestyle factors alone. Castration reduces incidence of chemically-induced BC in rodents. It is unclear if this effect is due to hormonal influences on activation/deactivation of carcinogens or a direct effect on urothelial cell proliferation or other malignant processes. We examined the effect of castration on BC growth in UPII-SV40T transgenic mice, which express SV40 T antigen specifically in urothelium and reliably develop BC. Furthermore, because BC growth in UPII-SV40T mice is exophytic, we speculated BC growth was dependent on angiogenesis and angiogenesis was, in turn, androgen responsive.

METHODS

Flat panel detector-based cone beam computed tomography (FPDCT) was used to longitudinally measure exophytic BC growth in UPII-SV40T male mice sham-operated, castrated, or castrated and supplemented with dihydrotestosterone (DHT). Human normal bladder and BC biopsies and mouse bladder were examined quantitatively for thrombospondin-1 (TSP1) protein expression.

RESULTS

Mice castrated at 24 weeks of age had decreased BC volumes at 32 weeks compared to intact mice (p = 0.0071) and castrated mice administered DHT (p = 0.0233; one-way ANOVA, JMP 6.0.3, SAS Institute, Inc.). Bladder cancer cell lines responded to DHT treatment with increased proliferation, regardless of androgen receptor expression levels. TSP1, an anti-angiogenic factor whose expression is inhibited by androgens, had decreased expression in bladders of UPII-SV40T mice compared to wild-type. Castration increased TSP1 levels in UPII-SV40T mice compared to intact mice. TSP1 protein expression was higher in 8 of 10 human bladder biopsies of normal versus malignant tissue from the same patients.

CONCLUSION

FPDCT allows longitudinal monitoring of exophytic tumor growth in the UPII-SV40T model of BC that bypasses need for chemical carcinogens, which confound analysis of androgen effects. Androgens increase tumor cell growth in vitro and in vivo and decrease TSP1 expression, possibly explaining the therapeutic effect of castration. This effect may, in part, explain gender differences in BC incidence and implies anti-androgenic therapies may be effective in preventing and treating BC.

Androgen receptor targets NFkappaB and TSP1 to suppress prostate tumor growth in vivo

The androgen role in the maintenance of prostate epithelium is subject to conflicting opinions. While androgen ablation drives the regression of normal and cancerous prostate, testosterone may cause both proliferation and apoptosis. Several investigators note decreased proliferation and stronger response to chemotherapy of the prostate cancer cells stably expressing androgen receptor (AR), however no mechanistic explanation was offered. In this paper we demonstrate in vivo anti-tumor effect of the AR on prostate cancer growth and identify its molecular mediators. We analyzed the effect of AR on the tumorigenicity of prostate cancer cells. Unexpectedly, the AR-expressing cells formed tumors in male mice at a much lower rate than the AR-negative controls. Moreover, the AR-expressing tumors showed decreased vascularity and massive apoptosis. AR expression lowered the angiogenic potential of cancer cells, by increasing secretion of an anti-angiogenic protein, thrombospondin-1. AR activation caused a decrease in RelA, a subunit of the pro-survival transcription factor NFkappaB, reduced its nuclear localization and transcriptional activity. This, in turn, diminished the expression of its anti-apoptotic targets, Bcl-2 and IL-6. Increased apoptosis within AR-expressing tumors was likely due to the NFkappaB suppression, since it was restricted to the cells lacking nuclear (active) NFkappaB. Thus we for the first time identified combined decrease of NFkappaB and increased TSP1 as molecular events underlying the AR anti-tumor activity in vivo. Our data indicate that intermittent androgen ablation is preferable to continuous withdrawal, a standard treatment for early-stage prostate cancer. (c) 2007 Wiley-Liss, Inc.

Expression of vascular endothelial growth factor in Taiwanese benign and malignant prostate tissues

BACKGROUND

The expression of vascular endothelium growth factor (VEGF) has been correlated to the grading and stage of prostate cancers. However, data regarding Taiwanese prostate cancer patients are lacking. The aim of the present study was to examine VEGF expression in our radical prostatectomy specimens.

METHODS

Fifty-one radical prostatectomy specimens with prostate cancer (15 stage pT2N0, 25 pT3N0, 11 pT2-4 N1) were stained using goat anti-human VEGF polyclonal antibody (AB-293NA; R&D Systems Inc., Minneapolis, MN, USA). The VEGF expression in malignant and nonmalignant prostate tissues was compared. The correlations of VEGF immunoreactivity with Gleason scores and pathologic stages were examined. MannWhitney U test was used for comparison of preoperative prostate-specific antigen levels between patients with and without VEGF expression.

RESULTS

Positive VEGF staining was observed in 80.4% of malignant epithelia, 39.2% of peritumoral stroma, 68.6% of benign hyperplastic glands, and 25.5% of adjacent stroma. There was no difference in VEGF expression between malignant and nonmalignant areas. Advanced disease had significantly higher frequency of stroma but not epithelium VEGF staining as compared to organ-confined disease (p = 0.002 and p = 0.412, respectively). The Gleason 7 and higher tumors had significantly higher frequency of VEGF staining in stroma but not glandular epithelium (p = 0.041 and p = 0.353, respectively). Tumors with positive epithelium VEGF staining had significantly higher PSA levels (21.3 18.1 vs. 10.8 6.8 ng/mL; p = 0.013).

CONCLUSION

There was no difference in VEGF immunoreactivity between malignant and benign prostatic epithelium in Taiwanese. High Gleason grade tumors and advanced disease had significantly higher frequency of VEGF expression in stroma but not glandular epithelium. Tumors with positive epithelium VEGF staining had significantly higher PSA levels.

The expression of vascular endothelial growth factor is associated with the risk of cancer progression after radical prostatectomy

OBJECTIVE

To analyse the prognostic value of vascular endothelial growth factor (VEGF) in men with clinically localized prostate cancer.

PATIENTS AND METHODS

Paraffin wax-embedded sections from the radical prostatectomy (RP) specimens of 40 men operated for clinically localized prostate cancer were used to build tissue microarrays. Of these patients, 17 had cancer progression and bone metastases after RP (group 1), and 23 remained free-of-tumour recurrence after RP (group 2). VEGF-A expression was examined in the RP specimens using immunohistochemistry.

RESULTS

The groups had similar tumour characteristics in terms of prostate-specific antigen level, Gleason score, and pathological stage. VEGF-A expression was significantly higher in group 1 than in group 2 (P=0.046). In logistic regression analysis, VEGF-A expression was the most significant predictive factor of cancer progression after RP.

CONCLUSION

VEGF-A expression in prostate cancer tissue is associated with the risk of cancer progression after RP. These results suggest that VEGF-A expression has a prognostic impact in clinically localized prostate cancer.

Thrombospondin-1 inhibits VEGF levels in the ovary directly by binding and internalization via the low density lipoprotein receptor-related protein-1 (LRP-1)

VEGF is a potent pro-angiogenic factor whose effects are opposed by a host of anti-angiogenic proteins, including thrombospondin-1 (TSP-1). We have previously shown that VEGF has important extravascular roles in the ovary and that VEGF and TSP-1 are inversely expressed throughout the ovarian cycle. To date, however, a causal interaction between TSP-1 and VEGF has not been identified. Here, we show that TSP-1 has a direct inhibitory effect on VEGF by binding the growth factor and internalizing it via LRP-1. Mice lacking TSP-1 are subfertile and exhibited ovarian hypervascularization and altered ovarian morphology. Treatment of ovarian cells with TSP-1 decreased VEGF levels and rendered the cells more susceptible to TNFalpha-induced apoptosis. Knockdown of TSP-1, through RNA interference, resulted in overexpression of VEGF and reduced cytokine-induced apoptosis. In conclusion, we demonstrate a direct inhibitory effect of TSP-1 on VEGF in the ovary. TSP-1's regulation of VEGF appears to be an important mediator of ovarian angiogenesis and follicle development.

Antibody array profiling reveals serum TSP-1 as a marker to distinguish benign from malignant prostatic disease

BACKGROUND

Blood protein markers that provide more accurate or earlier diagnosis of prostate cancer should have a positive impact on prostate cancer treatment and management.

METHODS

Serum samples from control subjects and patients with benign or malignant prostatic disease were analyzed on antibody arrays targeting multiple candidate prostate cancer markers and detected with two-color, rolling-circle amplification (TC-RCA). The measurements of certain antibodies were validated using immunoblots, immunoprecipitation/mass spectrometry, and sandwich immunoassays.

RESULTS

Several potential disease-associated protein alterations were uncovered. The most significant was thrombospondin-1, which was strongly elevated in patients with benign prostatic disease and repressed in patients with prostate cancer. Thrombospondin-1 levels did not correlate with prostate-specific antigen (PSA) levels and differentiated benign from malignant disease with 79% sensitivity and 81% specificity.

CONCLUSIONS

The measurement of thrombospondin-1 could be used to assist the decision to obtain a biopsy in men with suspected prostate cancer, which could lead to a reduction in the number of unnecessary prostatic biopsies.

Microvessel density and regulators of angiogenesis in malignant and nonmalignant prostate tissue

The aim of this study was to investigate the relationship between microvessel density (MVD), positive and negative angiogenic factors, and established prognostic factors in prostate cancer (PC), and, to clarify the effect of angiogenic factors to angiogenesis. The vascularization of neoplastic, non-neoplastic prostate tissue was determined by CD34 immunostaining. Angiogenetic mediators VEGF, bFGF, TSP-1, and p53 were studied by immunohistochemistry. Neovascularization and p53, VEGF, and TSP-1 expressions of tumorous tissue were higher than non-tumorous tissue. The bFGF expression in these tissues was not different. The p53 expression was not correlated with the expressions of VEGF, bFGF, and TSP-1 in PC. Our results demonstrate a significant increase in MVD, VEGF, TSP-1, and p53 expressions in prostate tumorigenesis. The pretreatment sPSA was the only parameter demonstrating significant correlation with tumor grade and may have a value in the prediction of aggressive tumor behavior in PC.

Ultraviolet Radiation Attenuates Thrombospondin 1 Expression via PI3K-Akt Activation in Human Keratinocytes

Thrombospondin 1 (TSP1) is an extracellular glycoprotein and a recognized inhibitor of angiogenesis. Recent studies have demonstrated that UV radiation induces an angiogenic switch, by which it alters the balance between pro- and anti-angiogenic factors in the skin. Here we describe the effects of acute UV exposure on TSP1 expression in human skin epidermis, primary keratinocytes and the epidermal cell line HaCaT. We found that protein and mRNA expressions of TSP1 are significantly reduced in human skin in vivo and in keratinocytes in vitro by a single UV exposure. In human skin and keratinocytes, UV exposure induced the phosphorylation of Akt, a downstream target of the PI3K pathways. Specific inhibitors of PI3K, wortmannin and LY294002, completely blocked Akt activation and UV-induced TSP1 downregulation in keratinocytes. We showed that a specific Akt phosphorylation inhibitor and small interfering RNA-mediated Akt depletion were also blocked by UV-induced TSP1 downregulation in keratinocytes. In conclusion, our findings demonstrate that acute UV exposure downregulates TSP1 expression via PI3K-Akt activation in human keratinocytes. These novel findings may help us understand the regulatory mechanisms of UV-induced skin angiogenesis.

Regulation of tumor angiogenesis by thrombospondin-1

Angiogenesis plays a critical role in the growth and metastasis of tumors. Thrombospondin-1 (TSP-1) is a potent angiogenesis inhibitor, and down-regulation of TSP-1 has been suggested to alter tumor growth by modulating angiogenesis in a variety of tumor types. Expression of TSP-1 is up-regulated by the tumor suppressor gene, p53, and down-regulated by oncogenes such as Myc and Ras. TSP-1 inhibits angiogenesis by inhibiting endothelial cell migration and proliferation and by inducing apoptosis. In addition, activation of transforming growth factor beta (TGF-beta) by TSP-1 plays a crucial role in the regulation of tumor progression. An understanding of the molecular basis of TSP-1-mediated inhibition of angiogenesis and tumor progression will aid in the development of novel therapeutics for the treatment of cancer.

The anti-tumour effect of low-dose continuous chemotherapy may partly be mediated by thrombospondin

BACKGROUND

Tumour growth is dependent on angiogenesis. Antiangiogenic chemotherapy, i.e. continuous or metronomic low-dose chemotherapy, is a method for administrating cytostatics at a low and well-tolerated concentration without prolonged breaks. The target is the genetically stable endothelial cells playing a pivotal role in angiogenesis within the tumour. Different mediators could mediate the antiangiogenic effect of metronomic chemotherapy. One of these mediators could be thrombospondin (TSP). TSP is a potent inhibitor of angiogenesis and might therefore be important in controlling tumour growth. This study was designed to evaluate the effects of low-dose continuous or moderate-dose bolus chemotherapy on tumour growth and on tumour expression of TSP.

MATERIALS AND METHODS

Rats bearing a malignant prostate tumour (Dunning AT-1) not expressing TSP were treated systemically with cyclophosphamide, doxorubicin or paclitaxel and the combination of cyclophosphamide and doxorubicin. Tumour growth and body weight were measured during the treatment. CD36, one of TSP's main receptors, was also analysed. The expression pattern of TSP-1, TSP-2 and CD36 was investigated using immunohistochemistry and Western blot analyses. Q-PCR was used to analyse TSP-1 mRNA expression.

RESULTS

Low-dose cyclophosphamide and paclitaxel re-induced the expression of TSP in the tumours. However, following a bolus dose of doxorubicin, tumours showed no expression of TSP. Both cyclophosphamide and doxorubicin treatments decreased the tumour weight by more than 60% compared with vehicle controls. When cyclophosphamide and doxorubicin were combined the tumour weight was reduced by 47%, while paclitaxel reduced the tumour weight by 18% compared to the vehicle controls.

CONCLUSIONS

Systemic low-dose continuous treatment of a rat prostate cancer model with cyclophosphamide and paclitaxel induced the expression of TSP in tumour tissue and inhibited tumour growth. These findings support the hypothesis that the anti-tumour effect of low-dose metronomic chemotherapy, at least with certain chemotherapeutics, is partly mediated by induction of endogenous antiangiogenic factors.

Vascular endothelial growth factor expression in untreated and androgen-deprived patients with prostate cancer

The aim of the study was to investigate immunohistochemically the expression of vascular endothelial growth factor (VEGF) in untreated and androgen-deprived patients with prostate cancer. The study included 20 patients with prostate cancer who had undergone transurethral prostatectomy due to infravesical obstruction. All patients had been receiving androgen deprivation therapy for at least 3 months. Transurethral prostatectomy specimens were examined for VEGF expression after androgen deprivation, and the biopsy samples of the same patients were used for the evaluation of VEGF expression before androgen deprivation. VEGF expression was analyzed using immunohistochemistry. Staining patterns determined by the staining scores were compared before and after treatment. The correlation of VEGF expression with PSA, Gleason score, and the percent change in PSA after treatment was also investigated. Eligible biopsy specimens were available in 15 of the 20 patients, allowing for the evaluation of VEGF expression before treatment. All prostate cancer specimens were positive. VEGF was localized mainly in the cytoplasm or on the membrane of carcinoma cells. Staining was strong in 86.7% of patients before androgen deprivation. Heterogeneous staining (strong in 25%, moderate in 35%, and weak in 40%) was observed after treatment. Staining scores were significantly higher in patients before androgen deprivation and showed a significant decrease after androgen deprivation (p = 0.007). Tumor staining correlated with Gleason score. No significant correlation was determined between VEGF expression and pre-treatment PSA and percent change of PSA after treatment. Immunohistochemical results indicate that VEGF expression is downregulated by androgen deprivation therapy. VEGF may be a potential target for therapeutic intervention in prostate cancer.

Downregulation of the angiogenesis inhibitor thrombospondin 1 in fibroblasts exposed to platelets and their related phospholipids

Platelets play many important roles in maintenance and formation of blood vessels. The latter is usually attributed to release of direct acting proangiogenic influences, e.g., vascular endothelial growth factor, sphingosine 1 phosphate, and other mediators, though their effects are normally opposed by endogenous angiogenesis inhibitors, including thrombospondin 1 (TSP-1/THSP1). Hence downregulation of TSP-1 is regarded as an important step in the generation of the pro-angiogenic (tumor) stroma. Here we report that platelets induce marked downregulation of TSP-1 (gene transcription and protein) in mouse dermal fibroblasts. This effect is: (i) blocked by inhibitors of sphingosine kinase, (ii) unaffected by inhibitors of G(i)-proteins (pertussis toxin), (iii) recapitulated by sphingosine, (iv) can also be induced by lysophosphatidic acid. These observations suggest a hitherto unappreciated, indirect role of platelets and their phospholipids in angiogenesis, i.e., proangiogenic conditioning of connective tissue stroma through lowering TSP-1 expression.

Androgens Repress the Expression of the Angiogenesis Inhibitor Thrombospondin-1 in Normal and Neoplastic Prostate

In order to understand why the angiogenesis inhibitor thrombospondin-1 (TSP1) is often, although not always, associated with prostatic tumors, we have investigated its relationship with the testosterone and the vasculature on which both normal and tumorigenic prostatic epithelia depend. In vivo, androgen withdrawal led to increased TSP1 production and decreased vascularization in the normal rat prostate which was reversed by androgen replacement. Androgen repression of TSP1 production occurred at the transcriptional level and was dependent on the presence of the first intron of the TSP1 gene. In an experimental model of prostate tumorigenesis, TSP1, when delivered by admixed stromal fibroblasts, markedly delayed LNCaP tumor growth and limited tumor vascularization. However, prolonged exposure to TSP1 resulted in the growth of tumors secreting high levels of vascular endothelial growth factor in the bloodstream of tumor-bearing animals and tumor growth was no longer sensitive to TSP1 inhibitory effects. Clinical evidence also suggested that prostate carcinomas are able to adapt to escape the antiangiogenic effects of TSP1. In human androgen–dependent localized prostate carcinomas, TSP1 expression was inversely correlated with blood vessel density. Androgen deprivation in patients with hormone-responsive tumors led to increased TSP1 expression and vascular regression. In contrast, despite a sustained expression in the tumor bed, TSP1 was no longer associated with decreased vascularization in hormone-refractory prostate tumors. Overall, these results suggest that the high in situ TSP1 exposure triggered by androgen deprivation in patients with prostate cancer could lead to early tumor resistance. Such patients could benefit from a combination of androgen deprivation and antiangiogenic therapy in order to minimize the induction of such tumor escape.

Thrombospondin and vascular endothelial growth factor are cyclically expressed in an inverse pattern during bovine ovarian follicle development

Angiogenesis does not normally occur in most adult tissues. However, in the ovary, there are cyclical vascular changes including angiogenesis that involve the interaction of numerous cytokines and growth factors. Angiogenic processes are regulated by a balance between pro- and antiangiogenic factors. The purpose of this study was to determine the expression of the antiangiogenic thrombospondin family and proangiogenic vascular endothelial growth factor (VEGF) in various sizes of healthy bovine follicles. Ovaries were collected from slaughterhouse animals and healthy follicles were sorted based on size (< 0.5 cm, small; 0.5-1.0 cm, medium; >1.0 cm, large). Thrombospondin (TSP) protein levels were significantly higher in small follicles. Immunohistochemistry confirmed the granulosa layer as the primary area within the follicle involved in TSP generation and that small follicles had the highest proportion of immunopositive cells. TSP-1 and -2 mRNA levels were significantly higher in small follicles than either medium or large follicles. TSP colocalized with CD36 on granulosa cells (GC) in the follicle and in cultured cells. In contrast with TSP, VEGF expression increased during growth and development of the follicle. FSH stimulated GC expression of TSP, while LH had no effect. In summary, TSP-1 and -2 were coordinately expressed in the extravascular compartment of the ovary during early follicle development. VEGF was inversely expressed, with expression increasing as follicles developed. Regulated expression and localization of these proteins suggests that they may be involved in regulating growth and development of the follicle in a novel fashion.

Thrombospondin 1: a multifunctional protein implicated in the regulation of tumor growth

Thrombospondins belong to a family of extracellular matrix (ECM) proteins widely found from embryonic to adult tissues. The modular structure of thrombospondins contains a series of peptide sequences implicated in a multiplicity of biological functions. Extracellular matrix undergoes important alterations under proteolysis that occurs in pathological processes like tumorigenesis. An elevated secretion of thrombospondin 1 (TSP1) is often observed in tumors and is sometimes considered as a predictive factor. However, the role of TSP1 in cancer progression remains controversial and must be carefully apprehended. The regulation of cell adhesion, proliferation, apoptosis by TSP1 is examined in the present review and it is clear from the literature and from our investigations that TSP1 presents both stimulatory and inhibitory effects. The exposition of cryptic sites upon conformational changes can partially explain this contradiction. More interestingly, the analysis of TSP1-directed intracellular signaling pathways activated through specific receptors or supramolecular receptors docking systems may be useful to discriminate the precise function of TSP1 in tumor progression. The central role played by TSP1 in the control of matrix-degrading enzyme activation and catabolism reveals attractive tracks of research and highlights the involvement of the lipoprotein receptor-related protein (LRP) receptor in these events. Therefore, TSP1-derived peptides constitute a source of potentially active matrikins which could provide essential tools in cancer therapy.

The expression of thrombospondin-1 in benign prostatic hyperplasia and prostatic intraepithelial neoplasia is decreased in prostate cancer

OBJECTIVE

To evaluate the immunohistochemical expression of thrombospondin (TSP), a potent inhibitor of angiogenesis, in human benign prostatic hyperplasia (BPH) and prostate cancer.

MATERIALS AND METHODS

The expression of TSP-1, TSP-2 and CD36 receptor was assessed in 73 tissue specimens using immunohistochemistry; specimens were from 32 patients with BPH, seven with prostatic intraepithelial neoplasia (PIN) and 34 with cancer.

RESULTS

Immunohistochemistry showed that all 39 patients with BPH and PIN had TSP-1-positive glands. In contrast, none of the 34 patients with cancer had positive TSP-1 staining in the cancer tissue. All 73 patients were positive for TSP receptor CD36 and negative for TSP-2.

CONCLUSIONS

TSP is expressed in BPH, down-regulated in PIN and absent in prostate cancer tissue. This may indicate that TSP is important in prostate cancer progression. Further studies are needed to understand the significance of these findings for the malignant transformation of the prostate gland.

Multiple regulatory pathways of vascular permeability factor/vascular endothelial growth factor (VPF/VEGF) expression in tumors

VPF/VEGF is a multi-functional cytokine with important roles in both vasculogenesis and angiogenesis. Its production is generally regulated by local oxygen concentration. Hypoxia stimulates VPF/VEGF production by increasing its gene transcription and the stability of its mRNA. The increase in transcription in hypoxia occurs mainly through the stabilization and activation of the transcription factor, Hypoxia Inducible Factor (HIF). Cellular oxygen concentration is not the only regulator of VPF/VEGF synthesis. Some cancer cells can produce high levels of VPF/VEGF even in normoxia. Clear cell renal carcinoma cell line (RCC) like 786-0, pancreatic carcinoma cell line, ASPC-1, fibrocarcinoma cell line, HT1080, ovarian cancer cells, etc. produce an elevated level of VPF/VEGF, which is not dependent on hypoxia. In this article, we discuss different regulatory pathways in tumor cells comprised of oncogenes, tumor suppressor genes etc. that play important roles, in both the transcription and stability of VPF/VEGF mRNA.

Human prostate cancer risk factors

Prostate cancer has the highest prevalence of any nonskin cancer in the human body, with similar likelihood of neoplastic foci found within the prostates of men around the world regardless of diet, occupation, lifestyle, or other factors. Essentially all men with circulating androgens will develop microscopic prostate cancer if they live long enough. This review is a contemporary and comprehensive, literature-based analysis of the putative risk factors for human prostate cancer, and the results were presented at a multidisciplinary consensus conference held in Crystal City, Virginia, in the fall of 2002. The objectives were to evaluate known environmental factors and mechanisms of prostatic carcinogenesis and to identify existing data gaps and future research needs. The review is divided into four sections, including 1) epidemiology (endogenous factors [family history, hormones, race, aging and oxidative stress] and exogenous factors [diet, environmental agents, occupation and other factors, including lifestyle factors]); 2) animal and cell culture models for prediction of human risk (rodent models, transgenic models, mouse reconstitution models, severe combined immunodeficiency syndrome mouse models, canine models, xenograft models, and cell culture models); 3) biomarkers in prostate cancer, most of which have been tested only as predictive factors for patient outcome after treatment rather than as risk factors; and 4) genotoxic and nongenotoxic mechanisms of carcinogenesis. The authors conclude that most of the data regarding risk relies, of necessity, on epidemiologic studies, but animal and cell culture models offer promise in confirming some important findings. The current understanding of biomarkers of disease and risk factors is limited. An understanding of the risk factors for prostate cancer has practical importance for public health research and policy, genetic and nutritional education and chemoprevention, and prevention strategies.

Thrombospondin-1, vascular endothelial growth factor expression and microvessel density in renal cell carcinoma and their relationship with multifocality

OBJECTIVE

To evaluate the relevance of microvessel density (MVD) and the angiogenic factors, vascular endothelial growth factor (VEGF, an important angiogenic factor in solid tumors) and thrombospondin-1 (TSP-1, a potent inhibitor of angiogenesis), to multifocality of renal cell carcinoma (RCC).

PATIENTS AND METHODS

Using immunohistochemistry the expression of CD34, TSP-1 and VEGF was assessed in 38 archival tissue specimens from 19 patients with unifocal RCC and 19 with multifocal RCC. Immunostaining results for VEGF was scored for the appropriate percentage of positive tumor cells and relative immunostaining intensity (score range 0-12). Only extracellular immunoreactivity was considered positive for TSP-1 and the same method was used to score the stromal staining. The microvessel density was measured by immunohistochemical staining with anti-CD34 monoclonal antibody.

RESULTS

VEGF immunoreactivity> or =1% was detectable in all unifocal and multifocal tumors. TSP-1 immunoreactivity was detected in 14 (73.7%) of 19 unifocal RCCs and in 16 (84.2%) of 19 multifocal RCC specimens (p=0.69). There were no statistically significant differences in the immunostaining intensity, percentage of immunopositive cells and the staining scores of VEGF and TSP-1 among the two groups. Additionally, there was no difference in MVD in multifocal and unifocal tumors.

CONCLUSION

As there is no difference in MVD count, and expression of angiogenic factors (VEGF and TSP-1) in multifocal and unifocal tumors, multifocality of RCC is not determined by VEGF/TSP-1 expression.

Tumorigenesis and the angiogenic switch

It has become evident that we cannot understand tumour growth without considering components of the stromal microenvironment, such as the vasculature. At the same time, the tumour phenotype determines the nature of the tumour vasculature. Much research is now devoted to determining the impact of angiogenesis on tumour development and progression, and the reciprocal influences of tumour products on the microvasculature. A more detailed understanding of the complex parameters that govern the interactions between the tumour and vascular compartments will help to improve anti-angiogenic strategies-- not only for cancer treatment, but also for preventing recurrence.

Expression of thrombospondin-1 is correlated with microvessel density in gastric carcinoma

Thrombospondin-1 (TSP-1) has been shown to play a role in angiogenesis in a variety of cancers, but some studies indicated a difference in the mechanism of TSP-1 on neovascularization according to organ or histological type. Wild-type p53 protein has been shown to induce TSP-1 expression. We examined the expression of TSP-1 protein in 80 gastric carcinomas using immunohistochemistry and studied the relationship with microvessel counts, p53 expression and clinicopathological factors. We also performed reverse-transcriptase polymerase chain reaction analysis for the TSP-1 mRNA expression in gastric carcinoma cell lines and gastric cancer tissue after laser capture microdissection. Strong expression of TSP-1 protein was detected in 30 (38%) of the 80 cases. Positive staining for TSP-1 was seen in the cytoplasm of the cancer cells. TSP-1 mRNA expression was confirmed in a majority of gastric carcinoma cell lines and carcinoma tissues. Microvessel counts were significantly higher in tumors with strong TSP-1 protein expression than in those without expression or weak expression of TSP-1 ( P=0.011). No significant correlation was found between TSP-1 expression and p53 staining and clinicopathological factors. Our results support an idea that increased TSP-1 expression may be associated with an angiogenic phenotype in gastric carcinoma and suggest that TSP-1 may play diverse roles in each organ.