Vascular Endothelial Growth Factor (VEGF) Expression in Prostate Cancer and Benign Prostatic Hyperplasia

Global analysis of differentially expressed genes in androgen-independent prostate cancer

Progression to androgen independent (AI) is the main cause of death in prostate cancer, and the mechanism is still unclear. By reviewing the expression profiles of 26 prostate cancer samples in a holistic view, we found a group of genes differentially expressed in AI compared with androgen-dependent groups (P-value<0.01, t-test). Focusing on apoptosis, proliferation, hormone and angiogenesis, we found a group of genes such as thioredoxin domain containing 5 , tumor necrosis factor receptor superfamily, member 10a , ribosomal protein S19 and Janus kinase 2 upregulated in AI prostate cancer, could play important roles in the transition from AD to AI and could be biomarkers of prognosis.

Angiotensin II type 1 receptor antagonist as an angiogenic inhibitor in prostate cancer

BACKGROUND

Angiotensin II (AII) type 1 receptor (AT1R) antagonists are used widely as antihypertensive agents, and long-term AT1R blockade may have a protective effect against cancer. We previously demonstrated that specific AT1R blockade with candesartan, an AT1R antagonist, inhibited vascular endothelial growth factor (VEGF) production and dramatically decreased lung metastasis of renal cancer by inhibiting tumor angiogenesis. This study was then undertaken to investigate the effects of AT1R blockade using candesartan in prostate cancer (PCa).

METHODS

We first determined whether hormone-independence is associated with tumor angiogenesis and AT1R expression. Accordingly, we postulated that AT1R blockade may affect angiogenesis in androgen-independent PCa rather than in androgen-dependent PCa, and investigated the effects of AII and candesartan on PCa cell lines and a tumor xenograft model.

RESULTS

A human hormone-refractory PCa (HRPC) and C4-2 androgen-independent PCa cell line showed significantly higher expression of VEGF, MVD, and AT1R than did human androgen-dependent PCa and an LNCaP androgen-dependent PCa cell line. In vitro, AII and candesartan did not directly affect the proliferation of LNCaP and C4-2 cells, but candesartan significantly suppressed VEGF production in C4-2 cells. In vivo, candesartan significantly suppressed VEGF expression, serum PSA concentration and tumor growth (1.1 +/- 0.2, 45.0 +/- 17.6 ng/ml, 235.8 +/- 37.4 mm(3)) in C4-2 xenografts in castrated mice, compared with the controls (2.4 +/- 0.6, 376.7 +/- 74.2 ng/ml, 830.8 +/- 147.6 mm(3)).

CONCLUSIONS

Candesartan exerted preventive effects on HRPC, rather than on androgen-sensitive PCa, through the inhibition of tumor angiogenesis.

Therapy of multidrug resistant human prostate tumors in the prostate of nude mice by simultaneous targeting of the epidermal growth factor receptor and vascular endothelial growth factor receptor on tumor-associated endothelial cells

BACKGROUND

Inhibiting epidermal growth factor receptor (EGF-R) and vascular endothelial growth factor receptor (VEGF-R) activation with AEE788 can decrease prostate cancer (CaP) growth/progression. We determined whether tumor cells or tumor-associated endothelial cells were the primary target by treating multidrug-resistant (MDR) CaP growing in the prostate of nude mice.

METHODS

MDR human CaP cells with 30-fold increased taxane-resistance were implanted into nude mouse prostates. After 2 weeks, mice were randomized to control, paclitaxel, AEE788, and AEE788/paclitaxel for 10 weeks. Mice were necropsied and tumors stained.

RESULTS

AEE788 or AEE788 plus paclitaxel significantly reduced tumor incidence and tumor weight, and eradicated lymph node metastasis. Inhibiting VEGF-R and EGF-R phosphorylation induced apoptosis of tumor-associated endothelial cells causing a second apoptotic wave of surrounding tumor cells.

CONCLUSION

Inhibiting VEGF-R and EGF-R activation on tumor-associated endothelial cells with AEE788 combined with paclitaxel can bypass CaP cell resistance and prevent lymph node metastasis.

Insulin-like growth factor-binding protein-3 inhibition of prostate cancer growth involves suppression of angiogenesis

Insulin-like growth factor-binding protein-3 (IGFBP-3) is a multifunctional protein that induces apoptosis utilizing both insulin-like growth factor receptor (IGF)-dependent and -independent mechanisms. We investigated the effects of IGFBP-3 on tumor growth and angiogenesis utilizing a human CaP xenograft model in severe-combined immunodeficiency mice. A 16-day course of IGFBP-3 injections reduced tumor size and increased apoptosis and also led to a reduction in the number of vessels stained with CD31. In vitro, IGFBP-3 inhibited both vascular endothelial growth factor- and IGF-stimulated human umbilical vein endothelial cells vascular network formation in a matrigel assay. This action is primarily IGF independent as shown by studies utilizing the non-IGFBP-binding IGF-1 analog Long-R3. Additionally, we used a fibroblast growth factor-enriched matrigel-plug assay and chick allantoic membrane assays to show that IGFBP-3 has potent antiangiogenic actions in vivo. Finally, overexpression of IGFBP-3 or the non-IGF-binding GGG-IGFBP-3 mutant in Zebrafish embryos confirmed that both IGFBP-3 and the non-IGF-binding mutant inhibited vessel formation in vivo, indicating that the antiangiogenic effect of IGFBP-3 is an IGF-independent phenomenon. Together, these studies provide the first evidence that IGFBP-3 has direct, IGF-independent inhibitory effects on angiogenesis providing an additional mechanism by which it exerts its tumor suppressive effects and further supporting its development for clinical use in the therapy of patients with prostate cancer.

The endocrine-gland-derived vascular endothelial growth factor (EG-VEGF)/prokineticin 1 and 2 and receptor expression in human prostate: Up-regulation of EG-VEGF/prokineticin 1 with malignancy

A new family of angiogenic factors named endocrine-gland-derived vascular endothelial growth factors (EG-VEGF)/prokineticins (PK) have been recently described as predominantly expressed in steroidogenic tissues. Whether the normal and malignant epithelial prostate cells and tissues express EG-VEGF/PK1 and PK2 and their receptors is still unknown. We studied the expression of EG-VEGF/PK1 and PK2 and their receptors (PK-R1 and PK-R2) in human prostate and their involvement in cancer. Using immunohistochemistry, Western blot, and RT-PCR, we determined the expression of EG-VEGF/PK1 in normal prostate (NP) and malignant prostate tissues (PCa), in epithelial cell primary cultures from normal prostate (NPEC) and malignant prostate (CPEC) and in a panel of prostate cell lines. In NPEC, CPEC, and in EPN, a nontransformed human prostate epithelial cell line, EG-VEGF/PK1, PK2, PK-R1, and PK-R2 mRNA levels were evaluated by quantitative RT-PCR. EG-VEGF/PK1 transcript was found in PCa, in CPEC, in EPN, and in LNCaP, whereas it was detected at low level in NP and in NPEC. EG-VEGF/PK1 was absent in androgen-independent PC3 and DU-145 cell lines. Immunochemistry confirmed that EG-VEGF/PK1 protein expression was restricted to hyperplastic and malignant prostate tissues, localized in the glandular epithelial cells, and progressively increased with the prostate cancer Gleason score advancement. EG-VEGF/PK1 and PK2 were weakly expressed in NPEC and EPN. On the other hand, their transcripts were highly detected in CPEC. PK-R1 and PK-R2 were found in NPEC, EPN, and CPEC. Interestingly, CPEC showed a significantly (P < 0.05) higher expression of EG-VEGF/PK1, PK2, PK-R1, and PK-R2 compared with NPEC and EPN. We demonstrated that PKs and their receptors are expressed in human prostate and that their levels increased with prostate malignancy. It may imply that EG-VEGF/PK1 could be involved in prostate carcinogenesis, probably regulating angiogenesis. Thus, the level of EG-VEGF/PK1 could be useful for prostate cancer outcome evaluation and as a target for prostate cancer treatment in the future.

Vector-based RNA interference against vascular endothelial growth factor-A significantly limits vascularization and growth of prostate cancer in vivo

RNA interference technology is emerging as a very potent tool to obtain a cellular knockdown of a desired gene. In this work we used vector-based RNA interference to inhibit vascular endothelial growth factor (VEGF) expression in prostate cancer in vitro and in vivo. We demonstrated that transduction with a plasmid carrying a small interfering RNA targeting all isoforms of VEGF, dramatically impairs the expression of this growth factor in the human prostate cancer cell line PC3. As a consequence, PC3 cells loose their ability to induce one of the fundamental steps of angiogenesis, namely the formation of a tube-like network in vitro. Most importantly, our "therapeutic" vector is able to impair tumor growth rate and vascularization in vivo. We show that a single injection of naked plasmid in developing neoplastic mass significantly decreases microvessel density in an androgen-refractory prostate xenograft and is able to sustain a long-term slowing down of tumor growth. In conclusion, our results confirm the basic role of VEGF in the angiogenic development of prostate carcinoma, and suggest that the use of our vector-based RNA interference approach to inhibit angiogenesis could be an effective tool in view of future gene therapy applications for prostate cancer.

Different isoform patterns for vascular endothelial growth factor between clear cell and papillary renal cell carcinoma

OBJECTIVE

To investigate the protein expression of vascular endothelial growth factor (VEGF) isoforms in relation to the clinical course in patients with different renal cell carcinoma (RCC) types, as angiogenesis is essential for tumour growth and metastasis.

PATIENTS AND METHODS

Western blots were assayed of protein extracts from tumour and concomitant kidney cortex samples from 96 patients. The levels of VEGF189, VEGF165, and VEGF121 isoforms were correlated with clinicopathological characteristics and survival.

RESULTS

VEGF189 levels were significantly higher in kidney cortex and chromophobe RCC than in papillary and conventional RCC. In papillary RCCs, VEGF189 levels correlated inversely with tumour stage and tumour size. VEGF165 levels were higher in kidney cortex than in RCC, but there was no difference among the RCC types. VEGF121 expression was associated with less advanced tumour stage in conventional RCC. Using multivariate analysis, VEGF189 remained as an independent prognostic factor for patients with papillary RCC.

CONCLUSIONS

VEGF189 was associated with tumour progression; in papillary RCC, VEGF189 was a significant independent prognostic factor. VEGF protein isoform patterns differed among the specific RCC types. Additional knowledge is essential to design new anti-angiogenic therapies for all RCC types.

A prostate secretory protein94-derived synthetic peptide PCK3145 inhibits VEGF signalling in endothelial cells: implication in tumor angiogenesis

We have previously observed that the synthetic peptide corresponding to amino acids 31-45 (PCK3145) of PSP94 can reduce prostate tumor growth in vivo. Moreover, a recently concluded phase IIa clinical trial with patients with hormone refractory prostate cancer indicated that PCK3145 down-regulates the levels of plasma matrix metalloproteinase (MMP)-9, a MMP involved in metastasis and tumor angiogenesis. The purpose of our study was to investigate the molecular mechanisms of action of PCK3145 and whether this peptide could antagonize tumor neovascularization. We show that, in a syngeneic in vivo model of rat prostate cancer, the expression of endothelial cell (EC) specific CD31, a marker of tumor vessel density, was decreased by 43% in PCK3145-treated animals. In vitro, PCK3145 specifically antagonized in a dose-dependent manner the VEGF-induced ERK phosphorylation as well as the phosphorylation of the VEGFR-2 in cultured EC (HUVEC). These anti-VEGF effects were partly reproduced by pharmacological inhibitors such as PD98059 and PTK787, suggesting that PCK3145 inhibits the tyrosine kinase activity associated to VEGFR-2, which in turn prevents intracellular signalling through the MAPK cascade. Moreover, PCK3145 was also found to inhibit the PDGF-induced phosphorylation of PDGFR in smooth muscle cells. Finally, PCK3145 inhibited in vitro EC tubulogenesis and VEGF-induced MMP-2 secretion suggesting its potential implication as an antiangiogenic agent. Our study demonstrates that PCK3145 interferes with the tyrosine kinase activity associated with VEGF signalling axis in EC. The antiangiogenic properties of this peptide could be highly beneficial and exploited in novel antiangiogenic therapies, for patients with various cancers.

Angiogenesis imaging in the management of prostate cancer

Angiogenesis is an integral part of benign prostatic hyperplasia, is associated with prostatic intraepithelial neoplasia and is a key factor in the growth and metastasis of prostate cancer. This review focuses on ultrasound and dynamic MRI in the evaluation of prostate cancer angiogenesis, and compares these techniques to functional CT and hydrogen magnetic resonance spectroscopic imaging. Image-based evaluation of angiogenesis in the prostate has established clinical roles in lesion detection, tumor staging and the detection of suspected tumor recurrence. One limitation of all these imaging techniques, however, is inadequate lesion characterization, particularly in differentiating prostatitis from cancer in the peripheral zone of the prostate, and in distinguishing between benign prostatic hyperplasia and central-gland tumors. Ultimately, local availability, expertise and the need to minimize patients' radiation burden will influence which technique is used in prostatic evaluations.

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.

Dual inhibition of the epidermal growth factor and vascular endothelial growth factor phosphorylation for antivascular therapy of human prostate cancer in the prostate of nude mice

BACKGROUND

Androgen-independent prostate cancer (PCa) may be susceptible to modulation of the tumor microenvironment. We determined whether a dual tyrosine kinase inhibitor (AEE788) of the epidermal growth factor receptor (EGF-R) and vascular endothelial growth factor receptor (VEGF-R) combined with chemotherapy can produce therapy of human PCa in nude mice.

METHODS

PC-3MM2 human PCa cells were injected into the prostate of nude mice. Three days later, the mice were randomized into four groups: saline control, paclitaxel, AEE788, and AEE788 and paclitaxel. The mice were treated for 5 weeks and necropsied. Tumor incidence, weight, and incidence of lymph node metastasis were recorded. Tumor tissue was analyzed immunohistochemically.

RESULTS

Treatment of mice with AEE788 or AEE788 plus paclitaxel significantly decreased tumor incidence, total tumor weight, and incidence of lymph node metastasis. AEE788 treatment alone or in combination with paclitaxel inhibited the phosphorylation of EGF-R and VEGF-R on tumor cells and tumor-associated endothelial cells. Therapeutic efficacy correlated with an increase in apoptosis of tumor cells and tumor-associated endothelial cells.

CONCLUSION

Blockade of EGF-R and VEGF-R signaling pathways coupled with chemotherapy suppressed the progressive growth and metastasis of human PCa cells growing orthotopically in nude mice.

HIF-1alpha, STAT3, CBP/p300 and Ref-1/APE are components of a transcriptional complex that regulates Src-dependent hypoxia-induced expression of VEGF in pancreatic and prostate carcinomas

Hypoxia stimulates a number of pathways critical to cancer cell survival, including the activation of vascular endothelial growth factor (VEGF) transcription. In normal fibroblasts, hypoxia-induced activation of the protein tyrosine kinase, Src, is required for VEGF expression. We show here in both pancreatic and prostate carcinoma cell lines cobalt chloride (used to mimic hypoxia) -induced VEGF expression requires Src activation and leads to increased steady-state levels of HIF-1alpha and increased phosphorylation of signal and transducer of transcription 3 (STAT3). STAT3 and hypoxia-inducible factor (HIF)-1alpha bind simultaneously to the VEGF promoter, where they form a molecular complex with the transcription coactivators CBP/p300 and Ref-1/APE. Expression of activated Src from an inducible promoter is sufficient to increase VEGF expression and form these STAT3/HIF-1alpha-containing promoter complexes. Inhibition of DNA binding by expression of either STAT3 or HIF-1alpha dominant negative mutants significantly reduces VEGF expression. These data suggest that the binding of both STAT3 and HIF-1alpha to the VEGF promoter is required for maximum transcription of VEGF mRNA following hypoxia.

Molecular markers of prostate cancer outcome

Molecular markers have the potential to serve not only as prognostic factors but may be targets for new therapeutic strategies and predictors of response in a range of cancers. Prostate cancer development and progression is predicated on a series of genetic and epigenetic events within the prostate cell and its milieu. Within this review, we identify candidate molecules involved in diverse processes such as cell proliferation, death and apoptosis, signal transduction, androgen receptor (AR) signalling, cellular adhesion and angiogenesis that are linked to outcome in prostate cancer. Current markers with potential prognostic value include p53, Bcl-2, p16INK4A, p27Kip1, c-Myc, AR, E-cadherin and vascular endothelial growth factor. Evolving technology permits the identification of an increasing number of molecular markers with prognosis and predictive potential. We also review the use of gene microarray analysis in gene discovery as a means of identifying and cosegregating novel markers of prostate cancer outcome. By integrating selected markers into prospective clinical trials, there is potential for us to provide specific targeted therapy tailored for an increasing number of patients.

Transition of an androgen-dependent human prostate cancer cell line into an androgen-independent subline is associated with increased angiogenesis

BACKGROUND

Androgen-independent prostate cancer is today an incurable disease, but increased understanding of the mechanisms for the transition into an androgen-independent state may increase the possibilities for more efficient strategies in the future.

METHODS

An androgen-independent subline, LNCaP-19, to the androgen-dependent prostate cancer cell line LNCaP was developed in vitro under standard culture conditions. The characteristics of LNCaP-19 regarding androgen responsiveness, PSA, and VEGF secretion was studied in vitro. The growth in vivo and the microvessel density (MVD) of the tumors were studied after inoculation in nude mice.

RESULTS

LNCaP-19 grows equally well in dextran-charcoal stripped FBS (DCC-FBS) as in normal FBS, and rapidly gives rise to tumors in both intact and castrated mice, indicating a true androgen-independent growth. The PSA secretion from LNCaP-19 cells was lower than from LNCaP cells, while the VEGF level was comparable to the secretion from LNCaP cells without androgen stimulation. The MVD was increased in the LNCaP-19 tumors, and the vessels also displayed a changed morphology with exclusively small microvessels without lumen.

CONCLUSIONS

LNCaP-19 shows characteristics resembling those of androgen-independent prostate cancer. An increased MVD and changed vessel morphology in the tumor, makes it an interesting model system for studies regarding angiogenesis in the context of the acquisition of androgen independence.

Angiogenesis-targeted therapies in prostate cancer

Most patients with metastatic prostate cancer will respond initially to ablation of gonadal androgen production. Eventually, all patients will develop progressive disease despite continued androgen suppression, a condition called androgen-independent or hormone-refractory prostate cancer. Hormone-refractory prostate cancer is characterized by virulent biologic and clinical behavior. Recently, docetaxel-based chemotherapy has been shown to improve survival and quality of life in this disease when compared with mitoxantrone-based therapy. However, results remain suboptimal. Recently, there have been remarkable advances in the delineation of the mechanisms of cancer growth, metastasis, and the intricate interactions between tumor cells and the surrounding normal tissues. The accumulated evidence has confirmed the importance of angiogenesis in these processes and validated the theory that inhibition of neovascularization is a promising therapeutic anticancer strategy. Currently, dozens of compounds that interfere with different steps of the angiogenic cascade are in preclinical and clinical development. Some of these agents have exhibited promising antitumor activity in hormone-refractory prostate cancer. This review summarizes the molecular mechanisms implicating angiogenesis in the development and progression of advanced-stage prostate cancer, as well as the drug development efforts that are targeting this process.

Expression of biomarkers modulating prostate cancer progression: implications in the treatment of the disease

OBJECTIVES

To determine whether COX-2, bcl-2 and neoangiogenesis are related to human prostate cancer relapse after definitive surgical treatment and progression toward androgen independence and to evaluate the association between the patterns of these tumoral biomarkers and other standard clinico-pathological parameters (such as Gleason score, PSA, TNM stage).

MATERIALS AND METHODS

We retrospectively analyzed the records on 126 prostate cancer samples from patients treated at our University Hospital from 1995 to 2002. The 72 patients with clinically localized disease (group 1) had undergone radical prostatectomy. Another 54 patients (group 2) had metastatic androgen-independent disease. Archived material relating to the subjects was then immunostained for bcl-2, COX-2 and CD-31, using an anti-bcl-2 monoclonal primary antibody, an anti-COX-2 polyclonal rabbit antibody and an anti-CD-31 monoclonal mouse antibody to evaluate neoangiogenesis (MVD, microvessel density).

RESULTS

We found that bcl-2, COX-2 and MVD expression increased from group 1 to group 2. The intergroup difference was significant only for high MVD (P < 0.05). On the other hand, high MVD, high bcl-2 and high COX-2 expression was correlated with a higher PSA level (P < 0.01), whereas only a high MVD was also related with Gleason score (P < 0.05). We used univariate analysis to evaluate the prognostic impact of biologic and clinico-pathologic parameters on the disease-free-survival of 72 patients treated by radical prostatectomy. A total of 30 patients (41.6%) experienced biochemical relapse; bcl-2, COX-2 and MVD significantly correlated with disease relapse in these patients. In fact, we observed disease relapse in 24/45 (53%) with high bcl-2 expression, in 15/21 (71%) with a high MVD count and finally, in 30/58 (52%) with high COX-2 expression. Finally, PSA value and Gleason score were the only two biologic markers significantly associated to disease relapse in a multivariate analysis.

CONCLUSIONS

Our results strongly support a role for bcl-2, COX-2 and angiogenesis in the development and progression of prostate cancer. Of course, we are aware of the small sample size considered in our study. Further investigations would better clarify the prognostic and therapeutic implications of these findings.

Stage-Specific Characterization of the Vascular Endothelial Growth Factor Axis in Prostate Cancer: Expression of Lymphangiogenic Markers Is Associated with Advanced-Stage Disease

Purpose: The vascular endothelial growth factor (VEGF) family plays a critical role in tumor angiogenesis and lymphangiogenesis. We characterized, at the mRNA and protein levels, the expression of VEGF-A and VEGF-D and their cognate receptors, VEGFR-1, VEGFR-2, and VEGFR-3 in early- and advanced-stage prostate cancer specimens.

Experimental Design: The levels of VEGF-A and VEGF-D mRNA in early- and advanced-stage specimens were compared using an angiogenic gene array and were confirmed by quantitative real-time PCR. Receptor protein levels and activation status were determined by immunoblotting. Spatial expression of the proteins was evaluated using immunohistochemistry with fresh and archival tissues from benign prostatic hypertrophy specimens, early-stage prostate specimens, and advanced-stage metastatic specimens. Circulating plasma levels of these growth factors were measured using ELISAs.

Results: We observed that expression patterns of VEGF isotypes corresponded to the prostate cancer stage: high expression of angiogenic growth factor VEGF-A was observed in early-stage prostate specimens, whereas high expression of lymphangiogenic growth factor VEGF-D was associated with advanced-stage metastatic disease. All VEGF receptors were present at variable levels in all specimens, but their activation states varied in a stage-specific manner. VEGFR-1 and, to a limited extent, VEGFR-2 were activated in early-stage specimens, whereas VEGFR-2 and VEGFR-3 were activated in advanced-stage specimens.

Conclusions: Our results suggest that lymphangiogenic markers, such as VEGF-D and VEGFR-2 and VEGFR-3, may be better than angiogenic markers as targets of therapeutic intervention in advanced-stage prostate disease.

Can Power Doppler Enhanced Transrectal Ultrasound Guided Biopsy Improve Prostate Cancer Detection on First and Repeat Prostate Biopsy?

OBJECTIVE

To determine the utility of Power Doppler enhanced transrectal ultrasound (PD-TRUS) and its guided prostate biopsies in men with prostate specific antigen (PSA) levels between 2.5 and 10 ng/ml and to evaluate its impact on prostate cancer (PCa) detection in men undergoing first and repeat biopsies.

METHODS

A total of 136 consecutive referred men with serum total PSA (Abbott Laboratories, Abbott Park, IL, USA) levels between 2.5 and 10 ng/ml (mean age 64 +/- 9 years, range 45-82) and a normal digital rectal examination were included. 101 underwent a first biopsy whereas 35 had repeat biopsy. Gray-scale transrectal ultrasound (TRUS), and PD-TRUS (B&K Medical, Denmark) were performed in lithotomy position before and during the biopsy procedure. Vascularity accumulation and perfusion characteristics were recorded and graded as normal or abnormal in the peripheral zone of the prostate. A Vienna-nomogram based biopsy regime was performed in all patients on first biopsy and a special biopsy regime on repeat biopsy plus additional biopsies from abnormal sites on PD-TRUS.

RESULTS

Overall PCa detection rate was 34.7% and 25.7% and abnormal accumulation on PD-TRUS was identified in 42.3% and 48.6% on first and repeat biopsy, respectively. The PCa detection rate, on first and repeat biopsy in patients with and without PD-TRUS accumulation were 67.4% versus 10.3% (p < 0.001) and 47.05% versus 5.6% (p = 0.0049), respectively. PD-TRUS directed biopsies were positive in 5.7% and 11.1% on first and repeat biopsy whereas PCa detection using the routine prostate biopsy regime was 94.3% and 88.9% on first and repeat biopsy. The sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of PD-TRUS signal alone for PCa detection on first biopsy was 82.8%, 78.8%, 87.9% and 89.7%, respectively, and 88.8%, 68.0%, 47.0% and 94.4% on repeat biopsy, respectively. In comparison, the results PD-TRUS guided biopsies were 53.8%, 59.1%, 16.7%, and 89.5%, on first biopsy, respectively, and 20.0%, 13.3%, 23.5%, 11.1% on repeat biopsy, respectively.

CONCLUSION

Negative PD-TRUS signal is able to exclude most of the patients without PCa in the PSA range of 2.5-10 ng/ml. As an additional tool at TRUS biopsy PD-TRUS has a high negative predictive value and may help to reduce the number of unnecessary biopsies.

Direct regulation of prostate blood flow by vascular endothelial growth factor and its participation in the androgenic regulation of prostate blood flow in vivo

Previous studies on prostate blood flow regulation have indicated that androgen regulates prostate blood flow. However, the mechanism responsible for this regulation is unknown. In the present study, we focused on the effects of vascular endothelial growth factor (VEGF), a key factor responsible for angiogenesis and androgenic blood flow regulation. We examined in vivo the effect of VEGF on prostate blood flow and its participation in the androgenic regulation of this blood flow using a castrated rat model following subcapsular intraprostatic injection method. We found that VEGF is involved in blood flow regulation with an activity equal to that of dihydrotestosterone (DHT). The effect of VEGF on prostate blood flow was already seen at 30 min after the administration. The elevating effect of DHT on castrated rat prostate blood flow was abolished by coadministration of DHT with neutralizing anti-VEGF antibody. The change in VEGF-A mRNA expression in response to androgen stimulation was examined by double-fluorescent probe quantitative PCR (Taqman PCR). The results showed that androgenic regulation of VEGF gene expression occurred shortly after androgen stimulation. VEGF gene up-regulation was abolished or down-regulated by coadministration of neutralizing anti-VEGF antibody. This is the first report on the importance of VEGF in the androgenic regulation signaling pathway that affects prostate blood flow. Alternative treatment targeted toward anti-VEGF activity as a substitute for ordinary antiandrogenic therapy may be effective against prostate diseases, especially those with androgen-independent and hyperhemorrhagic status.

Epstein-Barr Virus (EBV) Latent Membrane Protein 1 Induces Interleukin-8 through the Nuclear Factor-??B Signaling Pathway in EBV-Infected Nasopharyngeal Carcinoma Cell Line

BACKGROUND/OBJECTIVES

Nasopharyngeal carcinoma (NPC) is a highly invasive and metastatic malignant tumor and is associated with Epstein-Barr virus (EBV) infection that exhibits type II latency. Angiogenesis is essential for tumor growth, invasion, and metastasis. Our previous studies have indicated that interleukin (IL)-8 was over-expressed in many NPC tissues and was found to be significantly correlated with angiogenesis by immunohistochemistry.

STUDY DESIGN

In vitro design.

METHODS

The influence of the EBV genome for IL-8 gene expression was studied using the EBV-genome-positive and -negative epithelial/NPC hybrid cell line NPC-KT. The EBV-positive and -negative clones were selected by polymerase chain reaction and in situ hybridization.

RESULTS

EBV-positive clones expressed abundant IL-8 mRNA compared with EBV-negative clones. This result indicated that over-expression of IL-8 depended on the presence of EBV genomes in NPC-KT cells. Two encoded genes, latent membrane protein (LMP)1 and EBV-encoded small RNAs (EBERs), expressed in NPC were transfected in EBV-negative NPC-KT cells. LMP1 transactivated the IL-8 promoter, whereas EBERs did not. Moreover, the nuclear factor (NF)-kappa B binding site in the IL-8 promoter was essential for the response to LMP1, and the activator protein (AP)-1 binding site played only a partial role.

CONCLUSIONS

LMP1 induces IL-8 mainly through the activation of NF-kappa B and partly through AP-1 in NPC model cell lines, NPC-KT, and this suggests that LMP1 plays an important role in the angiogenesis of NPC.

Activator protein 2alpha inhibits tumorigenicity and represses vascular endothelial growth factor transcription in prostate cancer cells

Activator protein-2alpha (AP-2) is a transcription factor that regulates proliferation and differentiation in mammalian cells. We have shown previously that although AP-2 is expressed highly in normal prostatic epithelium, its expression is lost in high-grade prostatic intraepithelial neoplasia and prostate cancer, suggesting that loss of AP-2 plays a role in prostate cancer development. We demonstrate that forced AP-2 expression in the prostate cancer cell line LNCaP-LN3 (AP-2 negative) inhibited dramatically tumor incidence in nude mice. To identify the genes that might have been responsible for this effect, we used microchip expression array. We found several genes known to be involved in malignancy were deregulated, including the vascular endothelial growth factor (VEGF) gene. Because VEGF was down-regulated by 14.7-fold in the AP-2-transfected cells and because it is a major angiogenic factor in prostate cancer development and progression, we chose to examine the AP-2-VEGF interaction. Our evidence suggests that AP-2 repressed transcriptionally the VEGF promoter by competing with the transcriptional activator Sp3. Loss of AP-2 in prostate cancer cells reduced the AP-2:Sp3 ratio and activated VEGF expression. AP-2 acts as a tumor-suppressor gene in prostate cancer. Elucidating the molecular events resulting from loss of AP-2 in the prostate epithelium has implications for the understanding and prevention of the onset of prostate cancer.

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.

Polarographic electrode study of tumor oxygenation in clinically localized prostate cancer

PURPOSE

To describe the oxygenation of clinically localized prostate cancer.

METHODS AND MATERIALS

Intraprostatic oxygen tension was measured using the Eppendorf electrode in 55 unanesthetized men with localized prostate cancer before radiotherapy. Measurements were made along two tracks through regions of suspected tumor in the prostate, and core needle biopsies were then obtained from the same regions.

RESULTS

The median pO(2) ranged from 0.2 to 57.3 mm Hg, and the grand median pO(2) was 4.5 mm Hg. The percentage of oxygen readings <5 mm Hg (HP(5)) ranged from 0% to 100% (median 60%). The track 1 oxygen readings were greater than those from track 2. Statistically significant heterogeneity was found in the individual oxygen readings: the between- and within-tumor components accounted for 32% and 68% of the total variability, respectively. However, the between-tumor variability in HP(5) significantly exceeded the within-tumor variability (61% vs. 39%). No association was found between oxygen values and clinical factors, including age, T stage, Gleason score, prostate-specific antigen level, hemoglobin concentration, or prior hormonal treatment. No difference was noted in the oxygenation between regions of tumor and normal prostate tissue, as determined from the core biopsies.

CONCLUSION

Localized prostate cancer is characterized by marked hypoxia and significant heterogeneity in oxygenation, similar to other human tumors. The normal prostate may contain regions of low oxygen concentration. HP(5), as determined in this study, should adequately discriminate among patients with prostate cancer and allow the independent prognostic significance of oxygenation to be evaluated once the study matures.

Elements regulating angiogenesis and correlative microvessel density in benign hyperplastic and malignant prostate tissue

PURPOSE

To quantify the ex vivo production of proangiogenic proteins (vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), urokinase-type plasminogen activator (u-PA), tissue-type plasminogen activator (tPA)) and angiogenesis inhibitors (plasminogen activator inhibitor type-1 (PAI-1) and angiostatin) from epithelial and stromal components of primary prostate cancer (CaP) and benign prostatic hyperplasia (BPH) cultures. To perform microvessel density (MVD) counts on sections of BPH and CaP from the same prostatectomy specimens.

SCOPE

Angiogenic cytokine expression was measured by immunoassays and in vitro angiostatin generating capacities assessed using immunoblotting. CaP and BPH tissue was immunostained using factor VIII antibody to determine MVD.

CONCLUSIONS

Elements regulating angiogenesis are present in both primary cultures of CaP and BPH, suggesting that angiogenic ability is well established in the absence of carcinoma.

Expression of vascular endothelial growth factor (VEGF) and its cognate receptors in human pheochromocytomas

Pheochromocytomas are well-vascularized tumors, suggesting that a potent angiogenic factor may be involved in the mechanism of their formation. As vascular endothelial growth factor (VEGF) is a potent mitogen for vascular endothelial cells, here we have investigated the mRNA and protein expression of VEGF and the mRNA expression of its two receptors (Flt-1 and Flk-1/KDR) in pheochromocytomas tissue. An increase in VEGF mRNA (mainly isoforms VEGF(121) and VEGF(165)) and in VEGF protein expression were observed by semi-quantitative RT-PCR and Western blot, respectively, compared to normal adrenomedullary tissue. Flk-1/KDR, and Flt-1 levels of mRNA were also increased markedly in tumors and correlated with levels of VEGF mRNA. Therefore, we speculate that upregulation of VEGF expression and its receptors might be important in the pathogenesis of pheochromocytomas.

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.

Vascular endothelial growth factor gene-460 C/T polymorphism is a biomarker for prostate cancer

OBJECTIVES

To use the Bst U I polymorphism as a genetic marker in the search for the association between patients with prostate cancer and normal control subjects. The formation or progression of prostate cancer is presumed to be associated with a polymorphism of the vascular endothelial growth factor (VEGF) gene. The most frequently seen polymorphism is Bst U I (C to T) located at the -460th nucleotide upstream of the VEGF gene.

METHODS

A normal control group of 119 healthy people and 96 patients with prostate cancer were examined. The polymorphism was seen after polymerase chain reaction-based restriction analysis.

RESULTS

The analysis revealed significant differences between normal individuals and patients with cancer (P <0.001). Also, the distribution of the "TT" homozygote in the patient group was greater than that in the control group. The odds ratio per copy of the "T" allele was 2.3 (95% confidence interval 1.4 to 3.8) and was 2.2 (95% CI 1.3 to 3.8) when adjusted for age. No statistically significant differences in clinical stage or grade were found. We also categorized the 54 patients who received hormonal therapy into response and nonresponse groups, but no statistically significant differences between these two groups were revealed (P = 0.110, Fisher's exact test).

CONCLUSIONS

The Bst U I polymorphism of the VEGF gene is a suitable genetic marker of prostate cancer but cannot be used in the prediction of the outcome of patients who have received hormonal therapy.

Transrectal colour Doppler ultrasonography for quantifying angiogenesis in prostate cancer

OBJECTIVE

To assess the correlation between angiogenesis and Doppler signal intensity using transrectal colour Doppler ultrasonography (CDUS) in patients with prostate cancer.

PATIENTS AND METHODS

The study comprised 56 patients who underwent radical prostatectomy and had untreated tumours with a volume of> 0.1 mL in the peripheral zone. CDUS images were recorded on videotape before surgery. The Doppler signal intensity in tumours was evaluated using the colour pixel intensity (PI). Microvessel density (MVD) and vascular endothelial growth factor (VEGF) immunoreactivity were determined in the prostatectomy specimens. Microvessels were identified by immunohistochemical staining of endothelial cells for CD31.

RESULTS

The PI in the tumour correlated with MVD (P < 0.001) and increased with higher levels of VEGF immunoreactivity (P = 0.004). There was no correlation between Gleason score and MVD or PI in the tumour.

CONCLUSION

Blood flow assessed by CDUS may reflect the state of angiogenesis in prostate cancer. CDUS may be a useful technique for predicting tumour progression or prognosis, and may be useful for monitoring the effects of anti-angiogenic agents in the future.

Prostate Development and Carcinogenesis

The process involved in the development and carcinogenesis of the prostate gland is complex. During early prostate development, the androgenic hormone from embryonic testicles is required for ductal formation, growth, and branching morphogenesis of the prostate gland. From this early stage, interactions between the epithelium and mesenchyme become firmly established through paracrine influence (i.e., growth factors) from mesenchyme (stroma), in response to testosterone, acting on epithelium to stimulate its proliferation, morphogenetic differentiation, and function. In return, the epithelium also exerts its paracrine effects on mesenchyme by regulating the differentiation and specific organizational pattern of its stromal smooth muscle. In a normal adult prostate, the maintenance of normal glandular structure and function is dependent not only on the constant presence of testosterone, but also on a normal intact and stable stroma. This chapter will concentrate first on factors involved in the normal development of the prostate gland and then on the aberrant changes in the homeostatic balance arising either from within (i.e., mutations) or outside (i.e., changes in hormonal balance) that result in derangements of the prostate gland. Finally, environmental and genetic factors that lead to prostate carcinogenesis including activation of oncogenes and mutations of tumor suppressor genes are also discussed.

Differential expression of angiogenic cytokines by cell lines and primary cultures of human prostate cancer

Studies on angiogenic cytokines usually are initially based upon their expression by available established cell lines. Our hypothesis is that established epithelial prostate cancer (CaP) cell lines do not accurately reflect angiogenic cytokine expression as compared to epithelial and stromal components of primary cultures generated from clinical CaP specimens. Serum free and growth factor free conditioned medium (CM) was collected from PC3, LNCaP, and their orthotopic selected prostate cancer sublines. Surgically acquired and pathologically confirmed neoplastic prostate tissue was selectively grown for selection of epithelial or stromal components, and CM was also collected. CM was assayed for urokinase (u-PA), basic fibroblast growth factor (bFGF), vascular endothelial growth factor (VEGF), and tumor necrosis factor alpha (TNF-alpha). u-PA was expressed only by androgen independent cell lines, but was detectable in the epithelial and stromal cultures of androgen sensitive primary cultures. bFGF was not secreted by cell lines nor epithelial primary cultures. VEGF was universally expressed, but TNF-alpha was not secreted by cells lines nor primary cultures. These data suggest that the expression of angiogenic cytokines by established epithelial CaP cell lines does not reflect epithelial and stromal primary cultures.Prostate Cancer and Prostatic Diseases (2001) 4, 106-111

The cryobiology of cryosurgical injury

Cryosurgery, or tissue destruction by controlled freezing, has been investigated as a possible alternative to surgical intervention in the treatment of many diseases. This technique, which is under the larger category of thermal therapy, has its origins in the 1800s when advanced carcinomas of the breast and uterine cervix were treated with iced saline solutions. Since those early times, this technique has been used routinely to treat malignancies on the surface of the body (ie, dermatologic tumors) and has gained some acceptance as a clinical tool for the management of internal malignancies, including carcinoma of the prostate and kidney. The main advantages of the technique are the potential for less invasiveness and lower morbidity compared with surgical excision. The study of the destructive process of freezing is the focus of this article and is divided into 2 main areas: (1) understanding the mechanism by which freezing destroys tissue, and (2) understanding the thermal history that causes tissue destruction. The term "thermal history," as used in this article, will mean the time-temperature history experienced by the tissue during a thermal insult.

Vascular endothelial growth factor and signaling in the prostate: more than angiogenesis

In cloning tyrosine kinase genes in dog prostate cells, a fragment of the vascular endothelial growth factor (VEGF) receptor 1 or Flt-1 was sequenced. To test for a functional protein, Flt-1 antibodies were used to probe immunoprecipitated tyrosine phosphorylated proteins. Western blotting revealed a major 170-180 kDa band and a few bands below 116 kDa in dog prostate and human prostatic carcinoma PC-3 cells, with higher levels in PC-3. Similar results were obtained with human placental membranes used as a source of Flt-1. That the major Flt-1 tyrosine phosphorylated protein was likely VEGF-R1 and part of VEGF signaling pathways was shown by enhanced level of only this protein when PC-3 cells were exposed to VEGF. Accordingly specific cell surface receptor complexes, displaced by VEGF but not EGF and compatible with Flt-1 in size, were revealed by chemical cross-linking after 125I-VEGF binding. Similarly to the prostatic neuroproduct, gastrin-releasing peptide/bombesin, VEGF directly triggered the tyrosine phosphorylation of focal adhesion kinase and stimulated PC-3 cell motility. The titration of prostate tissue sections with VEGF-A antibodies revealed a confined staining in chromogranin A and/or serotonin positive neuroendocrine (NE) cells, including in primary tumors and lymph node metastases. Given that NE differentiation is associated with advanced disease, that NE cells are a significant source of VEGF in prostatic tumors, and that VEGF directly act on prostate cancer cells in vitro, VEGF-A may be more than angiogenic in prostate cancer and hence favor progression by affecting tumor cells.

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

OBJECTIVE

To evaluate the expression of thrombospondin-1 (TSP-1, a potent inhibitor of angiogenesis) and vascular endothelial growth factor (VEGF, an important angiogenic factor in solid tumours) in prostate cancer, and their relationship with p53 status.

PATIENTS AND METHODS

Using immunohistochemistry, the expression of VEGF, TSP-1 and p53 was assessed in 82 archival tissue specimens from 23 patients with benign prostatic hyperplasia (BPH), 22 with localized prostate cancer and 37 with metastatic prostate cancer. Seven of the last group had received androgen deprivation therapy. The relationship between the expression of VEGF, TSP-1 and p53 status was also evaluated with tumour grade and stage in patients with prostate cancer.

RESULTS

The seven patients receiving hormonal treatment were excluded from the analysis because androgen deprivation significantly increased TSP-1 and decreased VEGF expression (both P < 0.01). Immunohistochemical analysis showed significantly higher VEGF and significantly lower TSP-1 expression (both P < 0.01) in prostate cancer than in BPH tissues. There was also significantly higher VEGF and significantly lower TSP-1 expression (both P < 0.05) in tissues from metastatic than localized prostate cancer. There was no significant correlation between VEGF or TSP-1 expression and Gleason score, but a significant inverse correlation between TSP-1 and VEGF expression. There was a significant association between VEGF expression and p53 status (P < 0.05), but TSP-1 expression was not associated with p53 status.

CONCLUSIONS

Angiogenic factors, including VEGF and TSP-1, might be important in the development and progression of prostate cancer. These changes seem to be influenced by p53 status. Identifying the angiogenic factors involved in prostate cancer might lead to the development of diagnostic or therapeutic strategies based on anti-angiogenesis.

Inhibition of vascular endothelial growth factor in the treatment of solid tumors

Vascular endothelial growth factor (VEGF) is the term used for a family of tumor-derived angiogenic factors that mediate endothelial proliferation and vascular permeability. Preclinical models have demonstrated the essential nature of VEGF in the angiogenesis of solid tumor growth and metastasis, whereas pathologic investigations have revealed strong correlations between VEGF production, microvessel density, and overall aggressiveness of many human solid tumors. Recent advances in the understanding of the molecular mechanisms of VEGF action have led to successful models for intervention in VEGF-mediated pathways in therapy for solid tumors. These include antibodies to block the binding of VEGF to its cellular receptors, small-molecule chemical inhibitors of the tyrosine kinase functions of the VEGF receptors, and antisense nucleic acids to interfere with cellular production of VEGF. Clinical investigations are ongoing to test the value of VEGF-based intervention alone or in combination with other anticancer agents.

Reactive stroma in prostate cancer progression

PURPOSE

The development of an altered stromal microenvironment in response to carcinoma is a common feature of many tumors. We reviewed the literature describing characteristics of reactive stroma, how reactive stroma affects cancer progression and how carcinoma regulates reactive stroma. Moreover, we present a hypothesis of reactive stroma in prostate cancer and discuss how the biology of reactive stroma may be used in novel diagnostic and therapeutic approaches.

MATERIALS AND METHODS

An extensive literature search was performed to review reports of the general features of wound repair stroma, general stromal responses to carcinoma, and stromal biology of normal and prostate cancer tissues. These studies were analyzed and a reactive stroma hypothesis in prostate cancer was developed.

RESULTS

Modifications to the stroma of breast, colon and prostate tumors parallel the generation of granulation tissue in wound repair. These changes include stromal cell phenotypic switching, extracellular matrix remodeling and angiogenesis induction. Therefore, it is predicted that a modified wound healing response induces the formation of reactive stroma in cancer to create a tumor promoting environment. Based on its role in wound repair and its over expression in prostate cancer, transforming growth factor-beta stands out as a potential regulator of reactive stroma.

CONCLUSIONS

Reactive stroma in prostate cancer and granulation tissue in wound repair show similar biological responses and processes that are predicted to promote cancer progression. Further identification of specific functional and regulatory mechanisms in prostate cancer reactive stroma may aid in the use of reactive stroma for novel diagnostic and therapeutic approaches.

Thrombospondin-1, vascular endothelial growth factor and fibroblast growth factor-2 are key functional regulators of angiogenesis in the prostate

BACKGROUND

Prostate cells secrete many molecules capable of regulating angiogenesis; however, which of these actually function as essential regulators of neovascularization is not yet clear.

METHODS

Functional angiogenic mediators secreted by normal and diseased prostate cells were identified using an in vitro angiogenesis assay. These factors were quantified by immunoblot or ELISA and localized in tissue by immunohistochemistry.

RESULTS

Normal prostate epithelial cell secretions were anti-angiogenic due to inhibitory thrombospondin-1 (TSP-1) whereas this inhibitor was decreased in the pro-angiogenic secretions derived from benign prostatic hyperplasia (BPH) and cancer cells. This pro-angiogenic activity depended primarily on fibroblast growth factor-2 (FGF-2) and/or vascular endothelial growth factor (VEGF) whose secretion was increased. Immunolocalization studies confirmed that the changes detected in vitro also occurred in vivo.

CONCLUSIONS

During disease progression in the prostate, production of TSP-1, the major inhibitor, is down-regulated while that of stimulatory FGF-2 and/or VEGF rise, leading to the induction of the new vessels necessary to support tumor growth.

BOLD MRI of human tumor oxygenation during carbogen breathing

An MRI method is described for demonstrating improved oxygenation of human tumors and normal tissues during carbogen inhalation (95% O2, 5% CO2). T2*-weighted gradient-echo imaging was performed before, during, and after carbogen breathing in 47 tumor patients and 13 male volunteers. Analysis of artifacts and signal intensity was performed. Thirty-six successful tumor examinations were obtained. Twenty showed significant whole-tumor signal increases (mean 21.0%, range 6.5-82.4%), and one decreased (-26.5 +/- 8.0%). Patterns of signal change were heterogeneous in responding tumors. Five of 13 normal prostate glands (four volunteers and nine patients with nonprostatic tumors) showed significant enhancement (mean 11.4%, range 8.4-14.0%). An increase in brain signal was seen in 11 of 13 assessable patients (mean 8.0 +/- 3.7%, range 5.0-11.7%). T2*-weighted tumor MRI during carbogen breathing is possible in humans. High failure rates occurred due to respiratory distress. Significant enhancement was seen in 56%, suggesting improved tissue oxygenation and blood flow, which could identify these patients as more likely to benefit from carbogen radiosensitization.

Angiogenic role for glycodelin in tumorigenesis

Angiogenesis plays an important role in neovascularization in tumors. Glycodelin, a hormone-responsive protein, has been detected in tumors of reproductive organs and is found in high levels in the plasma of subjects with gynecological malignancies. Glycodelin is also found in the endothelial cells of the umbilical cord and in the blood vessels of tumors. In this study, we tested whether glycodelin-rich amniotic fluid and a synthetic peptide derived from the sequence of glycodelin peptide (Gp) might promote angiogenic response by examining the migration and tube formation in human umbilical cord vein endothelial cells (HUVECs). Increased migration and tube formation of HUVECs were found in the presence of amniotic fluid and Gp, and this increase was blocked by antibody to Gp and by an anti-vascular endothelial growth factor (VEGF) antibody, suggesting that the angiogenic effects of glycodelin might be mediated by VEGF. The results also showed that Gp significantly increased the release of VEGF protein and mRNA expression in HUVECs, RL-95 (human endometrial carcinoma cells), OVCAR-3 (human ovarian adenocarcinoma cells), EM42 (human endometrial epithelial cells), THP-1 (human monocyte), and MCF-7 and MDA-MB-231 (human breast adenocarcinoma cells) cell lines. VEGF receptor Fit-1 mRNA expression in HUVECs was also increased in the presence of Gp. These findings, together with the suggestion from the literature that glycodelin may have immunosuppressive properties, suggest that glycodelin might play an important role in neovascularization during embryogenesis and tumor development.

Blockade of NF-kappaB activity in human prostate cancer cells is associated with suppression of angiogenesis, invasion, and metastasis

Since the NF-kappaB/relA transcription factor is constitutively activated in human prostate cancer cells, we determined whether blocking NF-kappaB/relA activity in human prostate cancer cells affected their angiogenesis, growth, and metastasis in an orthotopic nude mouse model. Highly metastatic PC-3M human prostate cancer cells were transfected with a mutated IkappaBalpha (IkappaBalphaM), which blocks NF-kappaB activity. Parental (PC-3M), control vector-transfected (PC-3M-Neo), and IkappaBalphaM-transfected (PC-3M-IkappaBalphaM) cells were injected into the prostate gland of nude mice. PC-3M and PC-3M-Neo cells produced rapidly growing tumors and regional lymph node metastasis, whereas PC-3M-IkappaBalphaM cells produced slow growing tumors with low metastatic potential. NF-kappaB signaling blockade significantly inhibited in vitro and in vivo expression of three major proangiogenic molecules, VEGF, IL-8, and MMP-9, and hence decreased neoplastic angiogenesis. Inhibition of NF-kappaB activity in PC-3M cells also resulted in the downregulation of MMP-9 mRNA and collagenase activity, resulting in decreased invasion through Matrigel. Collectively, these data suggest that blockade of NF-kappaB activity in PC-3M cells inhibits angiogenesis, invasion, and metastasis.

Effects of androgen deprivation on prostatic morphology and vascular permeability evaluated with mr imaging

PURPOSE

To assess magnetic resonance (MR) measures of vascular permeability of prostate cancer treated with androgen deprivation and to correlate these with morphologic appearances and serum prostate-specific antigen (PSA) levels.

MATERIALS AND METHODS

MR examinations in 56 consecutive patients with prostate cancer were performed before and after luteinizing hormone-releasing hormone analog treatment. T2-weighted and contrast medium-enhanced T1-weighted MR images were obtained. Pre- and posttreatment comparisons of morphologic features, glandular volume, and enhancement-related parameters (capillary permeability, leakage space, gadolinium accumulation) were made.

RESULTS

Fifty-five tumors were seen before treatment; 42, after treatment. Signal intensity in the peripheral zone and seminal vesicles decreased on T2-weighted images in 42 (75%) and 25 (45%) patients, respectively. Median volume in tumor decreased by 65% (95% CI: 55%, 76%); in central gland, by 30% (95% CI: 25%, 35%). Reductions in tumor permeability (P <.001) and changes in washout patterns were observed (P <.001). Tumor permeability reductions coincided with a decrease in serum PSA levels in 91% of patients. A weak correlation between tumor permeability and volume change was seen (r = 0.55, P =.04). Reductions in peripheral zone (P <.001) and central gland (P =.009) permeability were noted.

CONCLUSION

Androgen deprivation decreases tumor volume and vascular permeability and impairs detection of prostate cancers. Use of MR estimates of permeability may be an additional way of assessing prostatic tumor response to antiandrogen treatment.

Vascular endothelial growth factor and its correlation with angiogenesis and p53 expression in prostate cancer

BACKGROUND

Previously it was demonstrated that in prostate tumors, angiogenesis measured as microvessel density (MVD) is associated with tumor stage as well as WHO grade and is an independent predictor of clinical outcome. Vascular endothelial growth factor (VEGF) is a major inducer of angiogenesis. There is some evidence that P53 mutations cause overexpression of VEGF. We studied VEGF expression, p53 overexpression, and P53 mutations in prostate cancer (PCA) to investigate the role of VEGF as an angiogenic marker and the possible deregulation of VEGF as a result of P53 mutations in PCA.

METHODS

Immunohistochemical staining with a polyclonal VEGF antibody was performed in 55 paraffin-embedded PCA, in which MVD had previously been determined, as well as in 5 prostatic adenomas (PA) and 20 adjacent normal prostate tissues. In addition, 37 PCA and 5 PAs were examined for p53 expression by immunohistochemistry. Temperature gradient gel electrophoresis (TGGE) was performed in 13 of these PCA to screen for P53 mutations. VEGF expression, p53 expression, and mutations were then correlated with tumor stage, grade, MVD, and clinical outcome.

RESULTS

While PA and normal prostate tissue generally showed no or only low VEGF expression, there was a significant increase in VEGF expression with tumor stage, grade, and MVD in PCA. During clinical follow-up (mean, 31.9 months), 9 of 55 patients had tumor progression. Significant differences in VEGF expression were found between patients with tumor progression and those without (P = 0.0004). Of the 37 PCA evaluated for p53 expression, 12 exhibited p53 overexpression. TGGE revealed P53 mutations in 3 of 13 PCA. However, there was no correlation between VEGF expression, p53 overexpression, and P53 mutation, respectively.

CONCLUSIONS

VEGF seems to be an important, clinically relevant inducer of angiogenesis in PCA. VEGF expression was shown to correlate positively with tumor stage, grade, MVD, and clinical outcome. However, regulation of VEGF in PCA appears to be independent of p53 expression.

Growth factors and epithelial-stromal interactions in prostate cancer development

Epithelial-stromal interactions are important not only in growth, development, and functional cytodifferentiation of the prostate but also in derangements of prostate gland such as BPH and prostate carcinoma. This chapter explores the roles of epithelium and stroma during this delicate process and highlights the role and mutual influence of each on the other. It also examines the importance of ECM in mediating the effects of androgens and drawn attention to estrogen and genetic factors in the process. During this process of epithelial-stromal interaction, growth factors play a central role in mediating the interactions. This chapter focuses on the role of several growth factors including epidermal growth factor, fibroblast growth factor, transforming growth factor alpha, transforming growth factor beta, insulin-like growth factor-1, vascular endothelial growth factor, nerve growth factor, platelet-derived growth factor, and hepatocyte growth factor. This chapter emphasizes the importance of epithelial-stromal interactions in tumorigenesis and highlights the switch of paracrine to autocrine mode during the process of carcinogenesis.

Vascular endothelial growth factor expression and capillary architecture in high-grade PIN and prostate cancer in untreated and androgen-ablated patients

BACKGROUND

Recent studies have demonstrated that angiogenesis is a potent prognostic indicator for patients with prostate cancer (PCa) and have pointed out that the evaluation of vascular endothelial growth factor (VEGF) is useful in assessing the angiogenic phenotype in PCa. The aim of the study was to investigate immunohistochemically the expression of VEGF and its correlation with the pattern of capillary architecture in prostate cancer and high-grade prostatic intraepithelial neoplasia (PIN), in untreated and androgen-ablated patients.

METHODS

Forty-five patients who underwent radical prostatectomy (RP) for localized prostate carcinoma were recruited for this study. The study population included two groups: 35 patients who did not receive chemo-, hormone, or radiation therapy before surgery, and 10 patients who were under complete androgen blockade (CAB) for 3 months at time of surgery. VEGF was examined by immunohistochemistry, and its tissue expression was compared with the pattern of capillary architecture evaluated by immunostaining the endothelial antigen CD34. The relationship of VEGF expression to chromogranin A-positive (e.g., neuroendocrine) cells was investigated.

RESULTS

In normal tissue, the intensity of the VEGF immunoreactivity in the cytoplasm of secretory cells ranged from negative to low. Very few basal cells stained for VEGF. All prostate cancer specimens stained positively, the intensity of the immunoreaction ranging from low to strong and being correlated with the Gleason score. Strongly positive VEGF immunoreactivity was detected in vascular endothelial cells and in stromal cells surrounding blood vessels. Two discrete immunostaining patterns were observed in high-grade PIN. VEGF expression of low-to-moderate intensity was defined as pattern A. The other, characterized by a strong cytoplasmic immunoreaction similar to that of poorly differentiated tumors, was defined as pattern B. The capillary architecture in high-grade PIN with pattern A was similar to the orderly vascular network seen in normal prostates, whereas in the pattern B it had the characteristics of microvessels usually seen in PCa. The degree of vascularization in the stroma adjacent to intensely VEGF-stained cells (neuroendocrine phenotype) was higher than that noted in association with secretory cells. CAB before surgery downregulated the expression of VEGF and decreased the degree of vascularization, except in the cell areas with neuroendocrine (NE) features.

CONCLUSIONS

Our immunohistochemical results indicate that significant levels of VEGF are present in prostate cancer and in a population of PIN lesions, expression being highest in association with NE cells. VEGF expression is downregulated by hormonal manipulation, except in the population of NE cells.