Blood vessels are regulators of growth, diagnostic markers and therapeutic targets in prostate cancer

Hyaluronan-Based Hydrogels for 3D Modeling of Tumor Tissues

Although routine two-dimensional (2D) cell culture techniques have advanced basic cancer research owing to their simplicity, cost-effectiveness, and reproducibility, they have limitations that necessitate the development of advanced three-dimensional (3D) tumor models that better recapitulate the tumor microenvironment. Various biomaterials have been used to establish these 3D models, enabling the study of cancer cell behavior within different matrices. Hyaluronic acid (HA), a key component of the extracellular matrix (ECM) in tumor tissues, has been widely studied and employed in the development of multiple cancer models. This review first examines the role of HA in tumors, including its function as an ECM component and regulator of signaling pathways that affect tumor progression. It then explores HA-based models for various cancers, focusing on HA as a central component of the 3D matrix and its mobilization within the matrix for targeted studies of cell behavior and drug testing. The tumor models discussed included those for breast cancer, glioblastoma, fibrosarcoma, gastric cancer, hepatocellular carcinoma, and melanoma. The review concludes with a discussion of future prospects for developing more robust and high-throughput HA-based models to more accurately mimic the tumor microenvironment and improve drug testing. Impact Statement This review underscores the transformative potential of hyaluronic acid (HA)-based hydrogels in developing advanced tumor models. By exploring HA's dual role as a critical extracellular matrix component and a regulator of cancer cell dynamics, we highlight its unique contributions to replicating the tumor microenvironment. The recent advancements in HA-based models provide new opportunities for more accurate studies of cancer cell behavior and drug responses. Looking ahead, these innovations pave the way for high-throughput, biomimetic platforms that could revolutionize drug testing and accelerate the discovery of effective cancer therapies.

Assessment of prostate cancer progression using a translational needle photoacoustic sensing probe: Preliminary study with intact human prostates ex-vivo

In our previous studies, we demonstrated the ability of an interstitial all-optical needle photoacoustic (PA) sensing probe and PA spectral analysis (PASA) to assess the aggressiveness of prostate cancer. In this clinical translation investigation, we integrated the optical components of the needle PA sensing probe into a 18G steel needle. The translational needle PA sensing probe was evaluated using intact human prostates in a simulated ultrasound-guided transperineal prostate biopsy. PA signals were acquired at 1220 nm, 1370 nm, 800 nm and 266 nm at each interstitial measurement location and quantified by PASA within the frequency range of 8-28 MHz. The measurement locations were stained for establishing spatial correlations between the quantitative measurements and the histological diagnosing. Most of the quantitative PA assessments reveal statistically significant differences between the benign and cancerous regions. Multivariate analysis combining the PASA quantifications shows an accuracy close to 90% in differentiating the benign and cancerous regions in the prostates.

Clinical relevance of androgen receptor alterations in prostate cancer

Prostate cancer (PC) remains a leading cause of cancer-related deaths among men worldwide, despite continuously improved treatment strategies. Patients with metastatic disease are treated by androgen deprivation therapy (ADT) that with time results in the development of castration-resistant prostate cancer (CRPC) usually established as metastases within bone tissue. The androgen receptor (AR) transcription factor is the main driver of CRPC development and of acquired resistance to drugs given for treatment of CRPC, while a minority of patients have CRPC that is non-AR driven. Molecular mechanisms behind epithelial AR reactivation in CRPC include AR gene amplification and overexpression, AR mutations, expression of constitutively active AR variants, intra-tumoural and adrenal androgen synthesis and promiscuous AR activation by other factors. This review will summarize AR alterations of clinical relevance for patients with CRPC, with focus on constitutively active AR variants, their possible association with AR amplification and structural rearrangements as well as their ability to predict patient resistance to AR targeting drugs. The review will also discuss AR signalling in the tumour microenvironment and its possible relevance for metastatic growth and therapy.

Rat Prostate Tumor Cells Progress in the Bone Microenvironment to a Highly Aggressive Phenotype

Prostate cancer generally metastasizes to bone, and most patients have tumor cells in their bone marrow already at diagnosis. Tumor cells at the metastatic site may therefore progress in parallel with those in the primary tumor. Androgen deprivation therapy is often the first-line treatment for clinically detectable prostate cancer bone metastases. Although the treatment is effective, most metastases progress to a castration-resistant and lethal state. To examine metastatic progression in the bone microenvironment, we implanted androgen-sensitive, androgen receptor-positive, and relatively slow-growing Dunning G (G) rat prostate tumor cells into the tibial bone marrow of fully immune-competent Copenhagen rats. We show that tumor establishment in the bone marrow was reduced compared with the prostate, and whereas androgen deprivation did not affect tumor establishment or growth in the bone, this was markedly reduced in the prostate. Moreover, we found that, with time, G tumor cells in the bone microenvironment progress to a more aggressive phenotype with increased growth rate, reduced androgen sensitivity, and increased metastatic capacity. Tumor cells in the bone marrow encounter lower androgen levels and a higher degree of hypoxia than at the primary site, which may cause high selective pressures and eventually contribute to the development of a new and highly aggressive tumor cell phenotype. It is therefore important to specifically study progression in bone metastases. This tumor model could be used to increase our understanding of how tumor cells adapt in the bone microenvironment and may subsequently improve therapy strategies for prostate metastases in bone.

Purinergic signalling and cancer

Receptors for extracellular nucleotides are widely expressed by mammalian cells. They mediate a large array of responses ranging from growth stimulation to apoptosis, from chemotaxis to cell differentiation and from nociception to cytokine release, as well as neurotransmission. Pharma industry is involved in the development and clinical testing of drugs selectively targeting the different P1 nucleoside and P2 nucleotide receptor subtypes. As described in detail in the present review, P2 receptors are expressed by all tumours, in some cases to a very high level. Activation or inhibition of selected P2 receptor subtypes brings about cancer cell death or growth inhibition. The field has been largely neglected by current research in oncology, yet the evidence presented in this review, most of which is based on in vitro studies, although with a limited amount from in vivo experiments and human studies, warrants further efforts to explore the therapeutic potential of purinoceptor targeting in cancer.

Suppression of DHT-induced paracrine stimulation of endothelial cell growth by estrogens via prostate cancer cells

BACKGROUND

Androgen modulation of angiogenesis in prostate cancer may be not directly mediated by androgen receptor (AR) as AR is not detected in the prostatic endothelial cells.

METHODS

We examined the paracrine stimulation of cell proliferation by prostate tumor cells and its modulation by androgen and estrogens in a murine endothelial cell line (MEC) that does not express AR.

RESULTS

Tumor cell conditioned media (TCM) collected from LAPC-4 or LNCaP prostatic tumor cells produced a time- and concentration-dependent induction of cell growth in MECs, which was parallel to the VEGF concentration in the TCM. This TCM-induced cell growth in MECs was enhanced by the treatment of prostatic tumor cells with dihydrotestosterone (DHT). Both the TCM-stimulation and DHT-enhancement effects in MECs were completely blocked by SU5416, a specific VEGF receptor antagonist. Co-administration of 17α-estradiol or 17β-estradiol with DHT in prostatic tumor cells completely inhibited the DHT-enhancement effect while treatment with DHT, 17α-estradiol or 17β-estradiol did not produce any significant direct effect in MECs. Moreover, administration of 17α-estradiol or 17β-estradiol in xenograft animals with LAPC-4 or LNCaP prostate tumor significantly decreased the microvessel number in the tumor tissues.

CONCLUSIONS

Our study indicated that prostate tumor cells regulate endothelial cell growth through a paracrine mechanism, which is mainly mediated by VEGF; and DHT is able to modulate endothelial cell growth via tumor cells, which is inhibited by 17α-estradiol and 17β-estradiol. Thus, both17α-estradiol and 17β-estradiol are potential agents for anti-angiogenesis therapy in androgen-responsive prostate cancer.

Gaussian process models of dynamic PET for functional volume definition in radiation oncology

In routine oncologic positron emission tomography (PET), dynamic information is discarded by time-averaging the signal to produce static images of the "standardised uptake value" (SUV). Defining functional volumes of interest (VOIs) in terms of SUV is flawed, as values are affected by confounding factors and the chosen time window, and SUV images are not sensitive to functional heterogeneity of pathological tissues. Also, SUV iso-contours are highly affected by the choice of threshold and no threshold, or other SUV-based segmentation method, is universally accepted for a given VOI type. Gaussian Process (GP) time series models describe macro-scale dynamic behavior arising from countless interacting micro-scale processes, as is the case for PET signals from heterogeneous tissue. We use GPs to model time-activity curves (TACs) from dynamic PET and to define functional volumes for PET oncology. Probabilistic methods of tissue discrimination are presented along with novel contouring methods for functional VOI segmentation. We demonstrate the value of GP models for voxel classification and VOI contouring of diseased and metastatic tissues with functional heterogeneity in prostate PET. Classification experiments reveal superior sensitivity and specificity over SUV calculation and a TAC-based method proposed in recent literature. Contouring experiments reveal differences in shape between gold-standard and GP VOIs and correlation with kinetic models shows that the novel VOIs contain extra clinically relevant information compared to SUVs alone. We conclude that the proposed models offer a principled data analysis technique that improves on SUVs for oncologic VOI definition. Continuing research will generalize GP models for different oncology tracers and imaging protocols with the ultimate goal of clinical use including treatment planning.

The stroma-a key regulator in prostate function and malignancy

Prostate cancer is a very common and highly unpredictable form of cancer. Whereas many prostate cancers are slow growing and could be left without treatment, others are very aggressive. Additionally, today there is no curative treatment for prostate cancer patients with local or distant metastasis. Identification of new, improved prognostic and diagnostic biomarkers for prostate cancer and the finding of better treatment strategies for metastatic prostate cancer is therefore highly warranted. Interactions between epithelium and stroma are known to be important already during prostate development and this interplay is critical also in development, progression of primary tumors and growth of metastases. It is therefore reasonable to expect that future biomarkers and therapeutic targets can be identified in the prostate tumor and metastasis stroma and this possibility should be further explored.

Primary xenografts of human prostate tissue as a model to study angiogenesis induced by reactive stroma

Characterization of the mechanism(s) of androgen-driven human angiogenesis could have significant implications for modeling new forms of anti-angiogenic therapies for CaP and for developing targeted adjuvant therapies to improve efficacy of androgen-deprivation therapy. However, models of angiogenesis by human endothelial cells localized within an intact human prostate tissue architecture are until now extremely limited. This report characterizes the burst of angiogenesis by endogenous human blood vessels in primary xenografts of fresh surgical specimens of benign prostate or prostate cancer (CaP) tissue that occurs between Days 6–14 after transplantation into SCID mice pre-implanted with testosterone pellets. The wave of human angiogenesis was preceded by androgen-mediated up-regulation of VEGF-A expression in the stromal compartment. The neo-vessel network anastomosed to the host mouse vascular system between Days 6–10 post-transplantation, the angiogenic response ceased by Day 15, and by Day 30 the vasculature had matured and stabilized, as indicated by a lack of leakage of serum components into the interstitial tissue space and by association of nascent endothelial cells with mural cells/pericytes. The angiogenic wave was concurrent with the appearance of a reactive stroma phenotype, as determined by staining for α-SMA, Vimentin, Tenascin, Calponin, Desmin and Masson's trichrome, but the reactive stroma phenotype appeared to be largely independent of androgen availability. Transplantation-induced angiogenesis by endogenous human endothelial cells present in primary xenografts of benign and malignant human prostate tissue was preceded by induction of androgen-driven expression of VEGF by the prostate stroma, and was concurrent with and the appearance of a reactive stroma phenotype. Androgen-modulated expression of VEGF-A appeared to be a causal regulator of angiogenesis, and possibly of stromal activation, in human prostate xenografts.

Regulation of soluble VEGFR-2 secreted by microvascular endothelial cells derived from human BPH

BACKGROUND

Recently, it was reported that the soluble vascular endothelial growth factor receptor-2 (sVEGFR-2) is secreted by microvascular endothelial cells from human BPH (HPECs). The purpose of this study was to investigate the modulation of sVEGFR-2 by common endothelial cell stimulators. In addition, the physiological role of sVEGFR-2 with regard to the VEGF-stimulated proliferation of HPEC was investigated.

METHODS

HPECs were isolated and cultured from fresh BPH tissue. After the incubation of HPECs either with adenosine triphosphate (ATP), interleukin (IL)-6, IL-8 or IL-12, the secretion of sVEGFR-2 was measured by enzyme-linked immunosorbent assay. For measurement of HPEC proliferation influenced by sVEGFR-2, VEGF-stimulated HPEC was cultured with/without sVEGFR-2. Cell proliferation was assessed with the Alamar Blue method.

RESULTS

The sVEGFR-2 secretion was increased by ATP and decreased by IL-12 and IL-8, respectively. IL-6 did not show any significant effect on sVEGFR-2 secretion of HPECs. HPEC proliferation was significantly inhibited by sVEGFR-2.

CONCLUSIONS

In this study, our data suggest that the secretion of sVEGFR-2 by microvascular endothelial cells from prostate origin is influenced by multiple endothelial cell stimulators. Furthermore, our data suggest that sVEGFR-2 acts as an antiangiogenic factor.

Prostate cancer increases hyaluronan in surrounding nonmalignant stroma, and this response is associated with tumor growth and an unfavorable outcome

Our objective was to investigate whether the presence of a tumor increases hyaluronan (HA) levels in surrounding prostate tissues and whether this extratumoral HA influences tumor growth and outcome. From a series of 287 men diagnosed with prostate cancer at transurethral resection and followed up with watchful waiting, tissue microarrays were constructed, stained, and scored for HA. A high HA staining score in the tumor stroma or in nonmalignant prostate tissue stroma were both associated positively with higher Gleason score and larger tumor volume, and was associated with a poor outcome. HA staining score was not an independent marker for outcome (multivariate Cox, with Gleason score, tumor volume, stage, and HA variables). In an orthotopic rat prostate cancer model, hyaluronic acid synthase-1 mRNA levels and HA staining were increased in normal prostate tissue surrounding prostate cancer. Orthotopic prostate cancer growth was increased by intraprostatic injection of HA. In conclusion, cancer in the prostate apparently stimulates HA synthesis both in tumor stroma and in the surrounding normal tissue. This promoted tumor growth and was associated with an unfavorable outcome.

Local insulin-like growth factor-I of ventral prostate was upregulated during long-term castration and may function through the autocrine system

The insulin-like growth factor I (IGF-I) is one of the main mitogens and anti-apoptotic factors, which has an important role in cell proliferation, inhibiting cell death in prostate cancer (PCa), and may act as a replacement for androgen after castration. Characterizing the changes in local IGF-I levels in the prostate after castration, is therefore of great importance for doctors to guide and select therapy models after surgical castration in men with PCa. The present study was performed to detect IGF-I of local ventral prostate (VP) at intervals up to 24 weeks after castration by a combination of reverse transcriptase PCR, western-blot, immunohistochemistry and immunofluorescence. We found IGF-I to be decreased sharply after castration and that mRNA and protein levels reached their minimum at 2 days and 5 days, respectively. The level of IGF-I increased gradually and although mRNA levels remained high for longer than 2 weeks, protein levels remained high for longer than 4 weeks. The epithelium cells of VP express IGF-I and its receptor longer than 2 weeks after castration. These findings suggested that although IGF-I of local VP decreases sharply in short-stage castration, its levels increase gradually and remain at high levels at least until 24 weeks. IGF-I synthesized mainly from epithelial cells, which may function through the autocrine system longer than 2 weeks castration.

Androgen deprivation induces rapid involution and recovery of human prostate vasculature

The response of the prostate tissue microenvironment to androgen deprivation (AD) represents a critical component in the treatment of benign prostatic hyperplasia and prostate cancer (CaP). Primary xenografts of human benign and CaP tissue transplanted to immunocompromized SCID mice were used to characterize the response of the prostate vasculature during the initial 14 days of AD. Microvessel density and vascular lumen diameter in the prostate xenografts decreased rapidly after AD, reached a nadir on days 2-4, and recovered between days 4 and 14. The number of apoptotic endothelial cells peaked on day 2 after AD and decreased to precastration levels over days 4-7. Leakage of vascular contents in the interstitial space was apparent between days 1 and 3 after AD; however, the vascular permeability barrier reestablished between days 7 and 14. Expression of vascular endothelial growth factor (VEGF)-A, VEGF receptor-2, and basic fibroblast growth factor protein increased in endothelial cells between days 2 and 4 after AD, which preceded vascular recovery and appeared to be a direct and specific response of the endothelial cells to AD. Lack of comparable upregulation of these genes in primary cultures of human prostate endothelial cells in response to AD suggests a role for paracrine signaling mediated through stromal or epithelial cells. VEGF-A expression by prostate endothelial cells appears to represent a key facilitator of the vascular rebound in human prostate tissue induced by removal of circulating testicular androgens.

Tumor indicating normal tissue could be a new source of diagnostic and prognostic markers for prostate cancer

IMPORTANCE OF THE FIELD

Prostate cancer is a common and multifocal disease but the diagnostic methods available are unsatisfactory. Most tumors present are of low malignant potential, whereas others are highly aggressive. At present, imaging cannot be used to guide tissue biopsies safely towards the most aggressive tumor present. To handle this problem multiple needle biopsies are taken. The biopsies often contain only normal prostate tissue, and even if the tumor is sampled it is not known whether a more aggressive cancer is present elsewhere in the organ. If changes in the normal tissue indicate the presence and nature of tumors, this information could be used to improve diagnostics and prognostics of prostate cancer.

AREAS COVERED IN THIS REVIEW

Current evidence that the tumor-adjacent morphologically normal prostate tissue is not completely normal is reviewed, and that this tissue, named tumor indicating normal tissue (TINT) by the authors, can be used to diagnose prostate cancer.

WHAT THE READER WILL GAIN

The reader will understand that tumors need to affect their surroundings in order to grow and metastasize and that the normal prostate tissue is therefore tinted by the presence and nature of cancer and that this knowledge can be used to develop new diagnostic and prognostic markers.

TAKE HOME MESSAGE

TINT changes could probably, when more rigorously defined and validated, be used to diagnose and prognosticate prostate cancer.

Stromal PDGFRbeta expression in prostate tumors and non-malignant prostate tissue predicts prostate cancer survival

Background

The identification of new prognostic markers for prostate cancer is highly warranted, since it is difficult to identify patients requiring curative treatment. Data from both experimental models and clinical samples have identified important functions of PDGFRβ on pericytes and fibroblasts in the tumor stroma.

Methodology/Principal Findings

In this study the prognostic significance of PDGFRβ in prostate cancer stroma, and in matched non-malignant tissue, was evaluated with immunohistochemistry. PDGFRβ expression was analyzed in normal and tumor stroma from more than 300 prostate cancer patients. High PDGFRβ expression in tumor stroma was associated with large tumor size, advanced stage, high Gleason score and high vessel density. Perivascular PDGFRβ staining in tumors was also correlated with high Gleason score. Correlations were also observed between PDGFRβ status in tumor stroma and non-malignant stroma. Similarly, high PDGFRβ expression in adjacent non-malignant tissue stroma correlated with large tumor size, advanced stage, high Gleason score and proliferation in non-malignant epithelium. Interestingly, high levels of PDGFRβ in the stroma of tumor and non-malignant tissue were associated with shorter cancer specific survival in prostate cancer patients.

Conclusions/Significance

The study revealed a number of novel associations between stromal PDGFRβ expression in prostate tumors and several important clinical characteristics, including survival.

Characterization and functional role of the stroma compartment in prostate tumors

Evaluation of: Dakhova O, Ozen M, Creighton CJ et al.: Global gene expression analysis of reactive stroma in prostate cancer. Clin. Cancer Res. 15, 3979–3989 (2009). Prostate tumors are composed of many cell types, yet the biological significances of the different nonepithelial cells have been largely overlooked. According to recent studies, however, the stroma, which constitutes a substantial part of the tumor volume, plays an important role during the initiation, progression, metastasis and metastatic growth of prostate cancers. To explore this further, Dakhova and co-workers compared gene expression in laser microdissected normal peripheral zone stroma with stroma in peripheral zone cancers (only those with reactive stroma grade 3). A total of 544 genes were upregulated and 606 genes downregulated in tumor stroma. The cancer stroma showed signs of formation of nerves, increased number of stem cells, and responses to DNA damage. Further studies are needed to explore the functional consequences of this, particularly the role of nerves. If these stroma changes can be used as prognostic markers, as targets for therapy, and if similar changes occur in metastases also need to be explored.

Inhibition of proliferation of prostate cancer cell line, PC-3, in vitro and in vivo using (-)-gossypol

We investigated the antiproliferative activity of (-)-gossypol on the human prostate cancer cell line PC3 in vitro and in vivo to elucidate its potential molecular mechanisms. Cell growth and viability were evaluated using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, and cell apoptosis was detected by flow cytometry, terminal deoxynucleotidyl transferase dUTP nick end labelling (TUNEL) and electron microscopy. Expression of proliferating cell nuclear antigen (PCNA), Bcl-2, CD31, caspase-3 and caspase-8 in tumour tissue was determined by immunohistochemistry. The drug concentration that yielded 50% cell inhibition (IC(50) value) was 4.74 microg mL(-1). In the PC-3 tumour xenograft study, (-)-gossypol (> 5 mg kg(-1)) given once a day for 7 days significantly inhibited tumour growth in a dose-dependent manner. Immunohistochemical analysis revealed that (-)-gossypol enhanced caspase-3 and caspase-8 expression and decreased the expression of PCNA, Bcl-2 and CD31 in tumour tissues. It suggested that cell apoptosis and inhibition of angiogenesis might contribute to the anticancer action of (-)-gossypol.

Extratumoral macrophages promote tumor and vascular growth in an orthotopic rat prostate tumor model

Tumor-associated macrophages are involved in angiogenesis and tumor progression, but their role and specific site of action in prostate cancer remain unknown. To explore this, Dunning R-3327 AT-1 rat prostate tumor cells were injected into the prostate of syngenic and immunocompetent Copenhagen rats and analyzed at different time points for vascular proliferation and macrophage density. Endothelial proliferation increased with tumor size both in the tumor and importantly also in the extratumoral normal prostate tissue. Macrophages accumulated in the tumor and in the extratumoral normal prostate tissue and were most abundant in the invasive zone. Moreover, only extratumoral macrophages showed strong positive associations with tumor size and extratumoral vascular proliferation. Treatment with clodronate-encapsulated liposomes reduced the monocyte/macrophage infiltration and resulted in a significant inhibition of tumor growth. This was accompanied by a suppressed proliferation in microvessels and in the extratumoral prostate tissue also in arterioles and venules. The AT-1 tumors produced, as examined by RT(2) Profiler PCR arrays, numerous factors promoting monocyte recruitment, angiogenesis, and tissue remodeling. Several, namely, chemokine (C-C) ligand 2, fibroblast growth factor 2, matrix metalloproteinase 9, interleukin 1beta, interferon gamma, and transforming growth factor beta, were highly upregulated by the tumor in vivo compared with tumor cells in vitro, suggesting macrophages as a plausible source. In conclusion, we here show the importance of extratumoral monocytes/macrophages for prostate tumor growth, angiogenesis, and extratumoral arteriogenesis. Our findings identify tumor-associated macrophages and several chemotactic and angiogenic factors as potential targets for prostate cancer therapy.

Secretion of soluble VEGF receptor 2 by microvascular endothelial cells derived by human benign prostatic hyperplasia

Vascular endothelial growth factor (VEGF) is one of the most potent mitogenic factors stimulating both prostate endothelial and prostate epithelial cells. Recently, some studies reported on the endothelial secretion of a soluble VEGF receptor 2 (sVEGFR-2) that modifies the free VEGF concentration by binding VEGF. For the first time in this study, we report on the secretion and the regulation of the secretion of sVEGFR-2 by microvascular endothelial cells derived from the tissue of human benign prostatic hyperplasia (HPEC). HPEC were isolated and cultured from fresh prostate tissue. The prostate epithelial cell line BPH-1 was cultured with the supernatant of the HPEC cell culture (fractioned by fast protein liquid chromatography) and the VEGF concentration was subsequently measured. HPEC were incubated with VEGF or tumor necrosis factor alpha (TNF-alpha). Afterwards, the concentration of sVEGFR-2 in the supernatant of unstimulated and stimulated HPEC was measured by ELISA. HPEC showed a typical endothelial morphology. Under cell culture conditions sVEGFR-2 binds VEGF: The measured VEGF concentration in the supernatant of BPH-1 cells was reduced when the fractions of HPEC conditioned medium with the highest sVEGFR-2 concentration were incubated with the BPH-1 cells. The sVEGFR-2 secretion of HPEC was stimulated by VEGF and TNF-alpha. For the first time we report on the secretion of sVEGFR-2 by microvascular endothelial cells of prostate origin. The secretion of sVEGFR-2 by HPEC was stimulated by VEGF and TNF-alpha. Our data suggest that sVEGFR-2 secreted by prostate endothelial cells could modify the effect of VEGF on prostate endothelial and prostate epithelial cells.

Sensitivity to tumor microvasculature without contrast agents in high spectral and spatial resolution MR images

Contrast-enhanced (CE)-MRI is sensitive to cancers but can produce adverse reactions and suffers from insufficient specificity and morphological detail. This research investigated whether high spectral and spatial resolution (HiSS) MRI detects tumor vasculature without contrast agents, based on the sensitivity of the water resonance line shape to tumor blood vessels. HiSS data from AT6.1 tumors inoculated in the hind legs of rats (N = 8) were collected pre- and post-blood pool contrast agent (iron-oxide particles) injection. The waterline in small voxels was significantly more asymmetric at the tumor rim compared to the tumor center and normal muscle (P < 0.003). Composite images were synthesized, with the intensity in each voxel determined by the Fourier component (FC) of the water resonance having the greatest relative image contrast at that position. We tested whether regions with high contrast in FC images (FCIs) contain vasculature by comparing FCIs with CE-MRI as the "gold standard" of vascular density. The FCIs had 75% +/- 13% sensitivity, 74% +/- 10% specificity, and 91% +/- 4% positive predictive value (PPV) for vasculature detection at the tumor rim. These results suggest that tumor microvasculature can be detected using HiSS imaging without the use of contrast agents.

Preoperative plasma endoglin levels predict biochemical progression after radical prostatectomy

PURPOSE

Endoglin (CD105) is a transmembrane glycoprotein expressed by human vascular endothelial cells thought to play a pivotal role in endothelial cell proliferation. The aim of this study was to evaluate the association of preoperative plasma endoglin levels with established clinical and pathologic features of prostate cancer and disease progression after radical prostatectomy.

EXPERIMENTAL DESIGN

Preoperative plasma endoglin levels were measured in 425 patients who underwent radical prostatectomy for clinically localized prostate cancer using a commercially available ELISA assay. Multivariate logistic regression was used to test the association of plasma endoglin levels with biochemical progression after radical prostatectomy.

RESULTS

Median follow-up for patients alive at the time of analysis was 36.8 months (interquartile range, 44.1). Of 425 patients, 77 patients (18.1%) experienced biochemical progression after radical prostatectomy. Preoperative plasma endoglin levels were significantly elevated in patients with higher preoperative total serum prostate-specific antigen (P < 0.001) and adverse pathologic features. Preoperative plasma endoglin was an independent predictor of biochemical progression after surgery after adjusting for the effects of standard preoperative and postoperative features (P < 0.001 and P = 0.026, respectively).

CONCLUSIONS

Preoperative plasma endoglin levels are associated with established features of advanced prostate cancer. More importantly, higher preoperative plasma endoglin levels are independent predictors of an increased risk of biochemical progression in patients treated with radical prostatectomy and bilateral pelvic lymphadenectomy.

Prostate stem cells and benign prostatic hyperplasia

Pharmacological approaches are available to medically-managed patients with symptomatic BPH before surgical intervention is required. These include daily treatment with alpha-blockers and 5-alpha-reductase inhibitors alone or in combination. These medical approaches have two major problems. First, treatments are chronic and must be taken daily. Second, there are significant financial costs and quality of life issues for such chronic treatments. Is it possible to develop effective acute therapy for symptomatic BPH without the long-term androgen deprivation-induced side effects? Two seminal but rarely cited studies of Walsh [Peters, Walsh: N Engl J Med 317:599-604, 1987] and Coffey et al. [Sufrin et al.: Invest Urol 13:418-423, 1976], combined with the growing understanding of the stem cell organization of the prostate stromal (S) and epithelial (E) compartments and their reciprocal paracrine and autocrine interactions provides the rationale for an acute approach.The Walsh study documents that: (1) androgen deprivation disrupts the reciprocal interaction between the prostate S and E thereby decreasing the weight of both compartments and (2) once BPH develops, androgen deprivation does not decrease the number of stem cell units in either the S or E compartments since subsequent androgen restoration fully restores the enlarged gland. The Coffey study documents that acute androgen deprivation sensitizes S-E interactions to radiation induced disruptions so that following radiation, androgen restoration does not induce full gland regrowth. Therefore, effective therapy for symptomatic BPH should be achievable by acute treatment with reversible androgen deprivation for a limited period followed by a single dose of conformal external beam radiation before allowing the man to recovery his normal serum testosterone.

Nuclear androgen receptors recur in the epithelial and stromal compartments of malignant and non-malignant human prostate tissue several months after castration therapy

BACKGROUND

As changed paracrine support from androgen receptor (AR)-positive cells in the prostate stroma contribute to castration-induced glandular involution, we examined if the subsequent relapse to androgen-independent epithelial cell growth could be related to reactivation of AR signaling in the stroma.

MATERIALS AND METHODS

Human prostate tissue taken before, within 14 days, and at suspected local tumor relapse after surgical castration therapy was immunostained for AR.

RESULTS

Castration initially decreased nuclear AR staining in epithelial and stroma cells, in both tumor and non-malignant tissue, but after some months, it reappeared.

CONCLUSIONS

Local tumor relapse was associated with reappearance of nuclear AR not only in tumor epithelial cells but also in the tumor stroma. Reappearance of nuclear AR in non-malignant prostate cells may be a physiological response to long-term systemic androgen ablation that could influence tumor growth.

Inhibition of the epidermal growth factor receptor enhances castration-induced prostate involution and reduces testosterone-stimulated prostate growth in adult rats

BACKGROUND

The epidermal growth factor receptor (EGFR) mediates regulatory signals in the normal prostate, but the functional importance of this is unclear.

METHODS

Adult male rats were castrated, or castrated + treated with gefitinib (Iressa, ZD1839), an EGFR tyrosine kinase inhibitor, for 3 days. Seven-day castrated rats were treated with testosterone, or testosterone + gefitinib, for 3 days.

RESULTS

Both castration alone and testosterone treatment in castrated animals increased the mRNA and protein levels of EGFR and phospho-EGFR in the ventral prostate. Inhibition of EGFR during castration and during testosterone-stimulated prostate growth resulted in a decrease in total epithelial weight, epithelial cell proliferation, endothelial cell proliferation, and increased epithelial cell apoptosis.

CONCLUSIONS

This study suggests that increased EGFR signaling during castration mediates stimulatory effects balancing castration-induced prostate regression, and that EGFR signaling is a necessary component in testosterone-stimulated prostate growth.

No association between polymorphism in the vascular endothelial growth factor gene at position -460 and sporadic prostate cancer in the Turkish population

The development and progression of prostate cancer (PCa) has biologically and genetically remained a mystery. A man's risk of developing PCa is influenced by both genetic and environmental factors. Angiogenic cytokines like vascular endothelial growth factor (VEGF) play a pivotal role in tumor angiogenesis. Single nucleotide polymorphisms in angiogenesis-dependent genes affect the sensibility of cancer development and progression. Therefore, we hypothesized a potential association between DNA sequence variations in VEGF -460 gene region and sporadic PCa patients in the Turkish population. 133 sporadic PCa patients and 157 healthy controls were studied. Genotypes were determined by polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) analysis. The distribution of genotype and allele frequencies of the polymorphism did not yield a statistically significant difference between patients and controls (P>0.05). Furthermore, classification of patients by tumor-lymph nodes-metastasis (TNM), Gleason Scores (GS) and serum prostate-specific antigen (PSA) levels did not show significant differences among the VEGF -460 C>T genotypes (P>0.05). This is the first demonstration showing that the VEGF -460 C>T polymorphism in men is not associated with sporadic PCa in the Turkish population.

Castration rapidly decreases local insulin-like growth factor-1 levels and inhibits its effects in the ventral prostate in mice

BACKGROUND

The mechanisms by which castration induces prostate involution are largely unknown.

METHODS

Early responses to castration in mouse ventral prostate (VP) were explored by quantitative microscopy, cDNA array expression, quantitative RT-PCR, and Western blot analysis. As several changes occurred in the insulin-like growth factor (IGF) system this was studied in more detail. Laser micro-dissection was used to localize sites of IGF-1 and IGF-1 receptor (IGF-R1) production. IGF-1 protein levels and IGF-R1 mediated signaling via insulin regulated substrate 1 and 2 (IRS-1 and 2) were examined. IGF-1 was injected into the VP in intact, and castrated mice and effects studied 1 day later.

RESULTS

IGF-1 and IGF binding protein 2 (IGFBP-2) mRNA were rapidly reduced whereas IGFBP-3 and IGF-R1 mRNA were increased after castration. IGF-1 was principally produced in the stromal compartment, while IGF-R1 was produced in both epithelial and stromal cells. IGF-1 and IRS-1 protein levels were decreased 1 and 3 days after castration, respectively, while IRS-2 was unchanged. Inactivating phosphorylation of IRS-1 at serine 307 was increased 1 day after castration, and activating phosphorylation at tyrosine 612 was decreased 2 days later. These changes were accompanied by decreased cell proliferation and increased cell death in the glandular and vascular compartment. Local injection of IGF-1 increased vascular density and epithelial cell proliferation in intact mice, but had no effect in castrated animals.

CONCLUSION

Decreased IGF-1 levels and action may mediate some of the key features of castration-induced prostate involution.

The use of thalidomide in androgen-independent prostate cancer

More than 200,000 men will be diagnosed with prostate cancer during the year 2006. Approximately 20% to 30% of these cases may develop advanced disease, for which there currently is no cure. Although therapy for this disease has improved significantly over the past few years, with docetaxel treatment showing improved survival times in metastatic disease, there remains the need for improved treatment options. Dr. Folkman put forth the idea of angiogenesis in 1971, and, since that time, researchers have been trying to determine the best possible way to inhibit blood vessel formation. This review summarizes the use of thalidomide in androgen-independent prostate cancer and the results of trials conducted at the National Cancer Institute.

Targeting of pericytes diminishes neovascularization and lymphangiogenesis in prostate cancer

BACKGROUND

The walls of capillaries in prostate cancer are composed of endothelial cells, and pericytes. NG2 is a transmembrane proteoglycan on nascent pericytes with a functional role in neovascularization.

METHODS

The anti-angiogenic effect of hydron pellets containing NG2 neutralizing antibody was quantified in intracorneal PC-3 and LNCaP xenografts. TRAMP and TRAMP-C1 tumors grafted in NG2 knockout mice represented intrinsic pericyte targeting. TRAMP and TRAMP-C1 grafts were analyzed with confocal microscope for microvascular density (MVD) and lymphatic vascular density (LVD).

RESULTS

NG2 neutralizing antibody decreased corneal neovascularization in PC3 (P<0.0001), and LNCaP (P=0.0079) xenografts. Mean MVD in TRAMP and TRAMP-C1 tumors in NG2 knockout mice were 71% (P=0.0006) and 63% (P=0.0011) lower than wild type controls, respectively. Mean LVD in TRAMP and TRAMP-C1 tumors in NG2 knockout mice were 73% (P=0.0003) and 84% (P<0.0001) lower than wild type controls, respectively.

CONCLUSIONS

Targeting of pericyte-NG2 decreases neovascularization and lymphangiogenesis in prostate cancer significantly.

Cyclooxygenase-2 expression correlates with local chronic inflammation and tumor neovascularization in human prostate cancer

PURPOSE

Chronic inflammation is linked to the development of cancer in several organs, including the prostate. Up-regulated cyclooxygenase-2 (COX-2) may play a role in influencing cell proliferation, differentiation, apoptosis, or angiogenesis. This study aimed to derive data from human prostate cancer to investigate whether chronic inflammation and angiogenesis were correlated with the expression of COX-2.

EXPERIMENTAL DESIGN

In this study, we did double-immunohistochemical analysis of a set of 43 human prostate cancer for COX-2 expression and the correlation with T-lymphocyte and macrophage densities and CD31-marked microvessel density (MVD) in situ.

RESULTS

COX-2 positive staining was detected in 40/43 cancer samples with the very heterogeneous expression. Elevated COX-2 expression was associated with high Gleason score (P = 0.002). Foci of chronic inflammation were found in all 43 samples. COX-2-positive areas were noted with high T-lymphocyte and macrophage densities than COX-2-negative tumor areas (P < 0.0001 and P = 0.001, respectively). MVD were also found higher in COX-2-positive areas than in COX-2-negative tumor areas (P = 0.001).

CONCLUSIONS

This study shows a novel relationship between COX-2 expression and the local chronic inflammation within prostate cancer and the increased angiogenesis. It is likely that the proinflammatory cytokines, released by T-lymphocytes and macrophages, up-regulate COX-2 in adjacent tumor cells and stimulate the angiogenesis in stromal tissues. These findings suggest that COX-2 may be an effective therapeutic target in prostate cancer treatment.

Cotargeting tumor and tumor endothelium effectively inhibits the growth of human prostate cancer in adenovirus-mediated antiangiogenesis and oncolysis combination therapy

Tumor-endothelial interaction contributes to local prostate tumor growth and distant metastasis. In this communication, we designed a novel approach to target both cancer cells and their "crosstalk" with surrounding microvascular endothelium in an experimental hormone refractory human prostate cancer model. We evaluated the in vitro and in vivo synergistic and/or additive effects of a combination of conditional oncolytic adenovirus plus an adenoviral-mediated antiangiogenic therapy. In the in vitro study, we demonstrated that human umbilical vein endothelial cells (HUVEC) and human C4-2 androgen-independent (AI) prostate cancer cells, when infected with an antiangiogenic adenoviral (Ad)-Flk1-Fc vector secreting a soluble form of Flk1, showed dramatically inhibited proliferation, migration and tubular formation of HUVEC endothelial cells. C4-2 cells showed maximal growth inhibition when coinfected with Ad-Flk1-Fc and Ad-hOC-E1, a conditional replication-competent Ad vector with viral replication driven by a human osteocalcin (hOC) promoter targeting both prostate cancer epithelial and stromal cells. Using a three-dimensional (3D) coculture model, we found that targeting C4-2 cells with Ad-hOC-E1 markedly decreased tubular formation in HUVEC, as visualized by confocal microscopy. In a subcutaneous C4-2 tumor xenograft model, tumor volume was decreased by 40-60% in animals treated with Ad-Flk1-Fc or Ad-hOC-E1 plus vitamin D3 alone and by 90% in a combined treatment group, compared to untreated animals in an 8-week treatment period. Moreover, three of 10 (30%) pre-established tumors completely regressed when animals received combination therapy. Cotargeting tumor and tumor endothelium could be a promising gene therapy strategy for the treatment of both localized and metastatic human prostate cancer.

Angiopoietin 2 expression is related to histological grade, vascular density, metastases, and outcome in prostate cancer

BACKGROUND

In several malignant tissues, the angiopoietins are principal regulators of vascular growth and regression, but in normal prostate and prostate tumors the role of the angiopoietins is unknown.

METHODS

Angiopoietin (ang) 1 and 2 were immunolocalized in TUR-diagnosed prostate tumors with long follow-up and the expression was related to vascular density and clinicopathological variables.

RESULTS

Ang 1 was strongly expressed in the basal epithelial cell layer in non-malignant tissue, whereas tumors had lower levels localized to the epithelial cells. A weak ang 2 immunoreaction was observed in non-malignant tissue and in low to intermediate Gleason score (GS) tumors, with a similar expression pattern. However, most high GS tumors showed an intense ang 2 staining. Ang 2 was significantly correlated to GS, density of endoglin stained blood vessels, metastases, and to cancer specific survival.

CONCLUSIONS

We conclude that ang 2 probably is an important regulator of angiogenesis in prostate cancer.

Serial tumour blood-flow measurements in androgen-dependent and -independent Shionogi tumour models

OBJECTIVE

To investigate the relationship between blood supply and hormonal status of hormone-dependent and -independent tumours in mice.

MATERIALS AND METHODS

Contrast-enhanced dynamic magnetic resonance imaging (MRI) was used to measure tumour blood flow (TBF) in Shionogi tumours implanted subcutaneously in mice. Serial measurements were taken throughout the initial tumour growth period, and during regression and subsequent androgen-independent (AI) relapse of the tumours in male mice, and throughout the growth of AI tumours in female mice. Average TBF values and coefficients of variation were calculated from tumour tissue perfusion maps reconstructed from MRI data. The Tukey-Kramer test was used to identify differences between androgen-dependent (AD), male AI and female AI tumours.

RESULTS

The mean TBF strongly depended on tumour size in all three stages of the tumour growth cycle. AI tumours had a significantly higher TBF than AD tumours, with mean (sd) values of 0.8 (0.3) (male AI) and 0.27 (0.1) mL/g/min (AD), (P < 0.001), and 0.61 (0.31) (female AI) and 0.27 (0.1) mL/g/min (AD) (P < 0.01), respectively. Tumour tissue perfusion was more homogenous in AI than in AD tumours, with a coefficient of variation of 0.91 (0.31) in male AI and 1.89 (0.48) in AD tumours (P < 0.001), and 1.47 (0.38) in female AI and 1.89 (0.48) in AD tumours (P < 0.05).

CONCLUSIONS

AI Shionogi tumours have a higher TBF than AD tumours; this could have implications in the diagnosis, prognosis, therapy and monitoring of hormone-sensitive tumours.

Decreased stromal expression and increased epithelial expression of WFDC1/ps20 in prostate cancer is associated with reduced recurrence-free survival

BACKGROUND

WAP-type four disulfide core (WFDC1)/ps20 is a member of the whey acidic protein family, which includes several serine protease inhibitors. Expression of WFDC1/ps20 was previously demonstrated in the normal human prostate stromal compartment. To further current understanding of the role of WFDC1/ps20 in prostate cancer, altered expression of WFDC1/ps20 protein in prostate cancer was evaluated.

METHODS

Immunohistochemical staining for WFDC1/ps20 was performed using tissue microarrays. Quantitation was based on the percentage of positive-staining stromal or epithelial cells and staining intensity. Resulting data was analyzed relative to the recurrence-free survival data and additional information for this patient set.

RESULTS

Decreased stromal expression of WFDC1/ps20 predicted shorter recurrence-free survival time by univariate analysis. Decreased stromal WFDC1/ps20 expression correlated with higher radical prostatectomy Gleason scores, positive surgical margins, extracapsular extension, higher clinical stage, and higher preoperative prostate specific antigen levels. Increased epithelial expression of WFDC1/ps20 also predicted shorter recurrence-free survival times by univariate analysis. Increased epithelial expression of WFDC1/ps20 correlated with higher biopsy and radical prostatectomy Gleason scores, and higher clinical stage.

CONCLUSIONS

Decreased stromal WFDC1/ps20 expression reflects the evolution of a prostate cancer reactive stroma, while increased epithelial WFDC1/ps20 expression may indicate progression to a more aggressive epithelial phenotype and may indicate an epithelial mesenchymal transition (EMT) process. Further evaluation of WFDC1/ps20 biologic functions will aid in the understanding of this interesting expression profile.

Randomized phase II trial of docetaxel plus thalidomide in androgen-independent prostate cancer

PURPOSE

Both docetaxel and thalidomide have demonstrated activity in androgen-independent prostate cancer (AIPC). We compared the efficacy of docetaxel to docetaxel plus thalidomide in patients with AIPC.

METHODS

Seventy-five patients with chemotherapy-naïve metastatic AIPC were randomly assigned to receive either docetaxel 30 mg/m(2) intravenously every week for 3 consecutive weeks, followed by a 1-week rest period (n = 25); or docetaxel at the same dose and schedule, plus thalidomide 200 mg orally each day (n = 50). Prostate-specific antigen (PSA) consensus criteria and radiographic scans were used to determine the proportion of patients with a PSA decline, and time to progression.

RESULTS

After a median potential follow-up time of 26.4 months, the proportion of patients with a greater than 50% decline in PSA was higher in the docetaxel/thalidomide group (53% in the combined group, 37% in docetaxel-alone arm). The median progression-free survival in the docetaxel group was 3.7 months and 5.9 months in the combined group (P =.32). At 18 months, overall survival in the docetaxel group was 42.9% and 68.2% in the combined group. Toxicities in both groups were manageable after administration of prophylactic low-molecular-weight heparin in the combination group.

CONCLUSION

In this randomized phase II trial, the addition of thalidomide to docetaxel resulted in an encouraging PSA decline rate and overall median survival rate in patients with metastatic AIPC. After the prophylactic low-molecular-weight heparin was instituted to prevent venous thromboses, the combination regimen was well tolerated. Larger randomized trials are warranted to assess the impact of this combination.

Decreased Pigment Epithelium-Derived Factor Is Associated with Metastatic Phenotype in Human and Rat Prostate Tumors

Pigment epithelium-derived factor, a potent angiogenesis inhibitor in the eye, is also expressed in the prostate. Prostate size and angiogenesis is increased in pigment epithelium-derived factor knockout mice, and pigment epithelium-derived factor is down-regulated in some prostate cancers. To investigate whether pigment epithelium-derived factor expression correlates with tumor progression, we examined 5 Dunning rat prostate sublines with different growth rates, differentiation, androgen dependence, vascular density, and metastatic ability and 26 human prostate cancers of Gleason score 8-10 obtained from patients at transurethral resection selected to represent two groups, with and without metastases at diagnosis. By Western blot, real-time quantitative reverse transcription-PCR, and immunostaining, pigment epithelium-derived factor was detected in highly differentiated, nonmetastatic, androgen-sensitive Dunning tumors and in the anaplastic, androgen insensitive but nonmetastatic Dunning tumors. In contrast, the metastatic Dunning tumor sublines showed very low pigment epithelium-derived factor expression levels. In human cancer tissues, by immunohistochemistry and real-time quantitative reverse transcription-PCR, patients without metastases at diagnosis had higher tumor pigment epithelium-derived factor levels than tumors from patients with metastases at diagnosis. In both the rat model and in the human tumors, the proliferation index and vascular count, as determined by Ki-67 staining and endoglin and/or factor VIII-related antigen staining, inversely correlated with pigment epithelium-derived factor mRNA levels. These observations indicate that loss of pigment epithelium-derived factor expression could be associated with the progression toward a metastatic phenotype in prostate cancer.

Potential pathologic markers for prostate chemoprevention studies

The field of exploring potential biomarkers for prostate cancer prevention continues to expand rapidly. In addition to a limited scope of histologic alterations, mainly PIN, a growing array of promising technologies (eg, computer-assisted analysis), and molecules involved in cell-cycle regulations, angiogenesis, and structural and numerical chromosomal alterations are potential candidates for surrogate endpoint biomarkers for prevention trials. Before any these potential candidates are adopted, however, the technical, interpretational, and validation requirements must be satisfied. More important, it is crucial to demonstrate that modulation of the frequency of the biomarker decreases the rate of cancer development.

Short-term human prostate primary xenografts: an in vivo model of human prostate cancer vasculature and angiogenesis

Transgenic spontaneously occurring and transplantable xenograft models of adenocarcinoma of the prostate (CaP) are established tools for the study of CaP progression and metastasis. However, no animal model of CaP has been characterized that recapitulates the response of the human prostate vascular compartment to the evolving tumor microenvironment during CaP progression. We report that primary xenografts of human CaP and of noninvolved areas of the human prostate peripheral zone transplanted to athymic nude mice provide a unique model of human angiogenesis occurring in an intact human prostate tissue microenvironment. Angiogenesis in human kidney primary xenografts established from human renal cell carcinoma and noninvolved kidney tissue, a highly vascular organ and cancer, was compared with angiogenesis in xenografts from the relatively less vascularized prostate. Immunohistochemical identification of the human versus mouse host origin of the endothelial cells and of human endothelial cell proliferation in the human prostate and human kidney xenografts demonstrated that: (a) the majority of the vessels in primary xenografts of benign and malignant tissue of both organs were lined with human endothelial cells through the 30-day study period; (b) the mean vessel density was increased in both the CaP and benign prostate xenografts relative to the initial tissue, whereas there was no significant difference in mean vessel density in the renal cell carcinoma and benign kidney xenografts compared with the initial tissue; and (c) the number of vessels with proliferating endothelial cells in primary xenografts of CaP and benign prostate increased compared with their respective initial tissue specimens, whereas the number of vessels with proliferating endothelial cells decreased in the benign kidney xenografts. Short-term primary human prostate xenografts, therefore, represent a valuable in vivo model for the study of human angiogenesis within a human tissue microenvironment and for comparison of angiogenesis in CaP versus benign prostate.

Androgen-dependent blood flow control and morphological changes of the capillaries in rat prostate

To clarify the effect of androgens on the microcirculation of the prostate, organ blood flow and ultrastructural features of the capillaries were investigated. In the ventral prostate (VP) of adult Wistar rats, organ blood flow was measured using a laser Doppler flowmetry, and the morphological features of the subepithelial capillaries were investigated and their luminal area was measured using transmission electron microscopy and a computed image analyzer at 1, 2, 3, and 7 days after castration, and 2 days after castration and gradational testosterone supplementation. The capillaries of the VP were classified into three types; oval opened (type 1), intermediate (type 2) and collapsed (type 3). Organ blood flow reduced from 40.5 to 27.7 mL/min/100 g (p < 0.0001) and the luminal area of the capillaries reduced from 13.5 to 4.5 microm2 (p < 0.0001) 2 days after castration. These reductions of the blood flow and the luminal area were gradationally prevented by testosterone supplementation. In the morphological features of the capillary, type 1 had rapidly shifted to types 2 and 3 after castration, and the shift of the capillary type was significantly prevented by the testosterone supplementation. These results clearly demonstrated that the androgen-dependent ultrastructural and morphological features in subepithelial capillaries revealed local microcirculatory conditions correlating the organ blood flow changes in VP.

Neutralizing VEGF bioactivity with a soluble chimeric VEGF-receptor protein flt(1-3)IgG inhibits testosterone-stimulated prostate growth in castrated mice

BACKGROUND

Recent studies show that testosterone-stimulated growth of the glandular tissue in the ventral prostate in adult castrated rats is preceded by increased epithelial VEGF synthesis, endothelial cell proliferation, vascular growth, and increased blood flow. These observations suggest that testosterone-stimulated prostate growth could be angiogenesis dependent, and that VEGF could play a central role in this process.

METHODS

Adult male mice were castrated and after 1 week treated with testosterone and vehicle, or with testosterone and a soluble chimeric VEGF-receptor flt(1-3)IgG protein.

RESULTS

Treatment with testosterone markedly increased endothelial cell proliferation, vascular volume, and organ weight in the ventral prostate lobe in the vehicle groups, but these responses were inhibited but not fully prevented by anti-VEGF treatment. The testosterone-stimulated increase in epithelial cell proliferation was unaffected by flt(1-3)IgG, but endothelial and epithelial cell apoptosis were increased in the anti-VEGF compared to the vehicle-treated groups.

CONCLUSIONS

This study suggests that testosterone stimulates vascular growth in the ventral prostate lobe indirectly by increasing epithelial VEGF synthesis and that this is a necessary component in testosterone-stimulated prostate growth.

The Combination of Antiangiogenic and Cytotoxic Agents in the Treatment of Prostate Cancer

Metastatic prostate cancer is one of the leading causes of cancer death in men. Although initially responsive to hormone therapy, it eventually progresses in almost all patients. For this reason, there has been a search for novel agents to use in the fight against androgen-independent prostate cancer. Antiangiogenesis is a relatively new antitumor strategy that has been employed in the treatments of many malignancies. As prostate cancer is likely dependent on angiogenesis for its growth and progression, it would logically serve as a good target for this modality. Initially met with great enthusiasm, antiangiogenic drugs have seen only limited success when used as single agents. This has been attributed to many possible etiologies including lack of cytotoxicity and use in situations of large tumor burden. In order to overcome these problems, many investigators are combining antiangiogenic agents with more traditional cytotoxic chemotherapy regimens in hope of augmenting the effects of either drug alone. This article will review the background of angiogenesis inhibition and the use of such combinations in metastatic prostate cancer.

Experimental therapy of human prostate cancer by inhibiting MDM2 expression with novel mixed-backbone antisense oligonucleotides: in vitro and in vivo activities and mechanisms

BACKGROUND

MDM2 oncogene is overexpressed in many human cancers including prostate cancer and MDM2 levels are associated with poor prognosis. This study was undertaken to investigate the functions of MDM2 oncogene in prostate cancer growth and the value of MDM2 as a drug target for prostate cancer therapy by inhibiting MDM2 expression.

METHODS

Antisense anti-human-MDM2 mixed-backbone oligonucleotide and its mismatch control were tested in in vitro and in vivo human prostate cancer models (LNCaP, DU 145, and PC-3) for anti-tumor activity. Targeted gene products and related proteins were analyzed and the anti-tumor activity was determined when the oligonucleotides were used alone or in combination with cancer therapeutics.

RESULTS

The antisense oligonucleotide specifically inhibited MDM2 expression in a dose- and time-dependent manner, resulting in significant anti-tumor activity in vitro and in vivo. In LNCaP cells, p53 and p21 levels were elevated. The antisense oligonucleotide also potentiated the effects of p53 activation and p21 induction by chemotherapeutic agents 10-hydroxycamptothecin, adriamycin, 5-fluorouracil, and paclitaxel. In DU145 cells, following inhibition of MDM2 expression, p21 levels were elevated although p53 levels remained unchanged. In both cell lines, the antisense oligonucleotide inhibited tumor cell growth and induced apoptosis in vitro. In a dose-dependent manner, the antisense oligonucleotide showed anti-tumor activity in nude mice bearing DU145 or PC-3 xenografts. It significantly increased therapeutic effectiveness of the chemotherapeutic agent irinotecan and slightly improved the effects of paclitaxel and Rituxan.

CONCLUSIONS

These results indicate that MDM2 has a role in prostate tumor growth through both p53-dependent and p53-independent mechanisms, indicating that MDM2 inhibitors have a broad spectrum of anti-tumor activities in human prostate cancers regardless of p53 status.