Co-expression of vascular endothelial growth factor (VEGF) and its receptors (flk-1 and flt-1) in hormone-induced mammary cancer in the Noble rat

The role of MRI in predicting Ki-67 in breast cancer: preliminary results from a prospective study

Purpose:

In the last decade contrast-enhanced magnetic resonance imaging (MRI) has gained a growing role as a complementary tool for breast cancer diagnosis. Currently the relationship between the kinetic features of a breast lesion and pathologic prognostic factors has become a popular field of research. Our aim is to verify whether breast MRI could be considered a useful tool to predict Ki-67 score, thus resulting as a breast cancer prognosis indicator.

Methods:

From June to December 2014, we enrolled patients with breast cancer who underwent preoperative dynamic contrast-enhanced MRI at the local health agency. We analyzed the time-signal intensity curves calculating the mean values of the following parameters: the basal enhancement (Ebase), the enhancement ratio (ENHratio), the maximum enhancement (Emax), and the steepest slope of the contrast enhancement curve (Smax). Scatterplots and Pearson correlation test were used to investigate the eventual associations among these parameters.

Results:

A total of 27 patients underwent breast MRI during the study period. The mean ± SD Ki-67 percentage was 27.03 ± 16.8; the mean Emax, Smax, Ebase, and ENHratio were 433.9 ± 120.2, 267.3 ± 96.8, 165.5 ± 77.1, and 187.1 ± 94.8, respectively. Scatterplots suggest a positive correlation between Ki-67 and both Emax and Smax. The correlation tests between Ki-67 and Emax, Ki-67 and Smax showed statistical significance.

Conclusions:

Our preliminary data suggest that enhancement pattern is closely linked to breast cancer proliferation, thus proving the relationship between more proliferating tumors and more rapidly enhanced lesions. This is hypothesis-generating for further studies aimed at promoting breast MRI in the early estimation of cancer prognosis and tumor in vivo response to chemotherapy.

Vascular Endothelial Growth Factor expression in peripheral blood of patients with pregnancy induced hypertension syndrome and its clinical significance

Objective: This study was conducted was to detect vascular endothelial growth factor (VEGF) levels in peripheral blood of patients with pregnancy-induced hypertension (PIH) syndrome and to investigate VEGF correlation with PIH occurrence.

Methods: Double-antibody enzyme-linked immunosorbent assay and fluorescent quantitative polymerase chain reaction were used to detect VEGF levels in the peripheral blood of non-pregnant women (normal group, 30 cases), normal pregnant women (pregnancy group, 30 cases) and PIH patients (PIH group, 30 cases).

Results: VEGF level in the pregnancy group was significantly higher than in the normal group, and the difference between these two groups was significant (P < 0.001). In the pregnancy group, VEGF reached the maximum level at the metaphase stage of pregnancy and started to decrease at advanced pregnancy. VEGF level in the PIH group was significantly lower than in the pregnancy group at advanced pregnancy (P < 0.01), and VEGF level significantly and gradually decreased with PIH aggravation (P < 0.05).

Conclusions: The significant decrease of VEGF level after pregnancy was possibly an important factor of PIH pathogenesis.

GPER mediates activation of HIF1α/VEGF signaling by estrogens

Biological responses to estrogens in normal and malignant tissues are mainly mediated by the estrogen receptors ERα and ERβ, which function as ligand-activated transcription factors. In addition, the G protein-coupled receptor GPR30 (GPER) mediates estrogenic signaling in breast cancer cells and cancer-associated fibroblasts (CAF) that contribute to cancer progression. In this study, we evaluated the role elicited by GPER in the estrogen-regulated expression and function of vascular endothelial growth factor (VEGF) in ER-negative breast cancer cells and CAF. We demonstrated that 17β-estradiol (E2) and the GPER-selective ligand G-1 triggered a GPER/EGFR/ERK/c-fos signaling pathway that leads to increased VEGF via upregulation of HIF1α. In further extending the mechanisms involved in E2-supported angiogenesis, we also showed that conditioned medium from CAF treated with E2 and G-1 promoted human endothelial tube formation in a GPER-dependent manner. In vivo, ligand-activated GPER was sufficient to enhance tumor growth and the expression of HIF1α, VEGF, and the endothelial marker CD34 in a mouse xenograft model of breast cancer. Our findings offer important new insights into the ability of estrogenic GPER signaling to trigger HIF1α-dependent VEGF expression that supports angiogenesis and progression in breast cancer.

Cytotoxic Effect of Immunotoxin Containing The Truncated Form of Pseudomonas Exotoxin A and Anti-VEGFR2 on HUVEC and MCF-7 Cell Lines

OBJECTIVE

Immunotoxins (ITs) have been developed for the treatment of cancer, and comprise of antibodies linked to toxins. Also vascular endothelial growth factor (VEGF) plays a key role in tumor angiogenesis, and the blockade of VEGF receptor-2 (VEGFR2) inhibits angiogenesis and tumor growth. The aim of this study was to produce anti-VEGFR2/rPE (Pseudomonas exotoxin) 38 IT to test its cytotoxic activity and mechanism of action.

MATERIALS AND METHODS

In this basic research and experimental study, at first, DNA that encodes recombinant PE38 protein was inductively expressed in Escherichia coli (E.coli) and purified by nickel-sepharose chromatography and further analyzed by western blot. Then, for production of IT, rPE38 was chemically conjugated to anti- VEGFR2. The cytotoxicity response of IT treatment was evaluated by 3-(4,5-Dimethylthiazol-2-Yl)-2,5-Diphenyltetrazolium Bromide (MTT) test in Human Umbilical Vein Endothelial Cell (HUVEC) and Michigan Cancer Foundation-7 (MCF-7) (VEGFR2+) cell lines. The mechanism of IT cytotoxicity was observed by Annexin V staining and flow cytometry. Continuous variables were compared with the analysis of variance (ANOVA; for all groups). P values less than 0.05 were considered statistically significant.

RESULTS

SDS-PAGE showed 98% purity of rPE38 and IT. In vitro dose-dependent cytotoxicity assay demonstrated that anti-VEGFR2/PE38 is toxic to VEGFR2-positive cells. IT treatment significantly inhibited proliferation of HUVEC and MCF-7 in a VEGFR2-specific manner as compared with the control groups (p<0.05). Flow cytometry showed that the mechanism of IT induced cell death is mediated by apoptosis.

CONCLUSION

IT treatment also caused remarkable synergistic cytotoxicity characterized by decreased cell viability, and an increased apoptotic index by both anti-VEGFR2 and PE38. Thus these results raise the possibility of using anti-VEGFR2/PE38 IT for cancer therapy because nearly all tumors induce local angiogenesis with high VEGFR expression.

Expression of vascular endothelial growth factor and vascular endothelial growth factor receptors 1 and 2 in invasive breast carcinoma: prognostic significance and relationship with markers for aggressiveness

AIMS

Vascular endothelial growth factor (VEGF), VEGF receptor 1 (VEGFR-1) and VEGF receptor 2 (VEGFR-2) play a role in breast cancer growth and angiogenesis. We examined the expression and relationship with clinical outcome and other prognostic factors.

METHODS AND RESULTS

Tumour sections from 468 breast cancer patients were immunostained for VEGF, VEGFR-1, and VEGFR-2, and their relationships with tumour vascularity, disseminated tumour cells (DTCs) in bone marrow and other clinicopathological parameters were evaluated. VEGF, VEGFR-1 and VEGFR-2 immunoreactivities were observed in invasive breast carcinoma cells. VEGF expression was significantly associated with VEGFR-1 and VEGFR-2 expression (P < 0.001). High-level cytoplasmic expression of VEGFR-1 was associated with significantly reduced distant disease-free survival (DDFS) (P = 0.017, log-rank) and breast cancer-specific survival (BCSS) (P = 0.005, log-rank) for all patients, and for node-negative patients without systemic treatment (DDFS, P = 0.03, log-rank; BCSS, P = 0.009, log-rank). VEGFR-1 expression was significantly associated with histopathological markers of aggressiveness (P < 0.05). Significantly reduced survival was observed in DTC-positive patients as compared with DTC-negative patients in the combined moderate/high VEGFR-1 group (P < 0.001 for DDFS and BCSS), and the same was true for DDFS in the moderate VEGFR-2 group (P = 0.006).

CONCLUSIONS

High-level expression of VEGFR-1 indicates reduced survival. Higher-level expression of VEGFR-1 or VEGFR-2 in primary breast carcinomas combined with the presence of DTC selects a prognostically unfavourable patient group.

Selection of Clinically useful Angiogenesis-Related Biomarkers: An Update

Angiogenesis is a complex phenomenon that involves interaction between growth factors/cytokines and their receptors, and proteolytic enzymes and their inhibitors, which, in addition to and in accordance with their main roles, act together during this multistep process. cancer angiogenesis is specific, because the same factors that enable angiogenesis are involved in the process of carcinogenesis. the aim of this review was to analyze the current knowledge regarding the significance of selected biomarkers in cancer angiogenesis, with emphasis on their prognostic value in the circulation.

Synthetic progestins differentially promote or prevent 7,12-dimethylbenz(a)anthracene-induced mammary tumors in sprague-dawley rats

Recent clinical trials show that combined oral dosing with estrogen and progestin increases the incidence of breast cancer in postmenopausal women. Similarly, in a rat model system of mammary carcinogenesis, the synthetic progestin medroxyprogesterone acetate (MPA) decreases latency and increases incidence of 7,12-dimethylbenz(a)anthracene (DMBA)-induced mammary tumors. The goal of this study was to compare the effects of four clinically relevant progestins, MPA, norgestrel (N-EL), norethindrone (N-ONE), and megestrol acetate (MGA), on DMBA-induced mammary carcinogenesis in the rat. The experimental protocol involved implantation of 60-day release progestin pellets four weeks after rats were treated with DMBA. In contrast to the effect of MPA, N-ONE, and N-EL, but not MGA, blocked DMBA-dependent carcinogenesis and a dose-dependent effect on tumor growth was shown for N-EL; MGA did not alter tumor growth. Histopathologic studies showed extensive hyperplastic lesions in mammary tissue of progestin-treated animals. Furthermore, following treatment with N-EL or N-ONE, immunohistochemical staining for vascular endothelial growth factor in hyperplastic mammary tissue was lower than in animals treated with DMBA plus MPA or DMBA alone. Expression of vascular endothelial growth factor receptor-1, estrogen receptor alpha, and progesterone receptor was also lower in hyperplastic mammary tissue in N-EL-, N-ONE-, and MGA-treated animals. Interestingly, N-EL stimulated progression of existing mammary tumors in DMBA/MPA-treated rats, suggesting stage-specific effects of N-EL in this model. Because N-EL and N-ONE prevent tumor growth in the early stages of DMBA-induced mammary carcinogenesis in rats, these progestins may have potential as chemopreventive agents in women with no history of breast disease or family history of breast cancer.

Response to trastuzumab, erlotinib, and bevacizumab, alone and in combination, is correlated with the level of human epidermal growth factor receptor-2 expression in human breast cancer cell lines

Human epidermal growth factor receptor-2 (HER2) and epidermal growth factor receptor (EGFR) heterodimerize to activate mitogenic signaling pathways. We have shown previously, using MCF7 subcloned cell lines with graded levels of HER2 expression, that responsiveness to trastuzumab and AG1478 (an anti-EGFR agent), varied directly with levels of HER2 expression. HER2 and EGFR up-regulate vascular endothelial growth factor (VEGF), a growth factor that promotes angiogenesis and participates in autocrine growth-stimulatory pathways that might be active in vitro. Here, we show that trastuzumab, erlotinib, and bevacizumab, individually and in combination, inhibit cell proliferation in a panel of unrelated human breast cancer cell lines, in proportion to their levels of HER2 expression. The combination of all three drugs provided a greater suppression of growth than any single drug or two-drug combination in the high HER2-expressing cell lines (P < 0.001). Combination index analysis suggested that the effects of these drugs in combination were additive. The pretreatment net level of VEGF production in each cell line was correlated with the level of HER2 expression (r = 0.883, P = 0.016). Trastuzumab and erlotinib each reduced total net VEGF production in all cell lines. Multiparameter flow cytometry studies indicated that erlotinib alone and the triple drug combination produced a prolonged but reversible blockade of cells in G1, but did not increase apoptosis substantially. These studies suggest that the effects of two and three-drug combinations of trastuzumab, erlotinib, and bevacizumab might offer potential therapeutic advantages in HER2-overexpressing breast cancers, although these effects are of low magnitude, and are likely to be transient.

Modulation of VEGF/Flk-1 receptor expression in the rat pituitary GH3 cell line by growth factors

Both vascular endothelial growth factor (VEGF) and its receptor Flk-1 are expressed in normal pituitary cells and in the prolactin- and growth hormone-producing GH3 cell line of the rat, thus suggesting autocrine/paracrine function. Regulation of the Flk-1 receptor system in pituitary cells is poorly understood, but evidence suggests that up-regulated growth factors play a role in its expression and activation. To study the role of growth factors in this process, we examined changes in VEGF and Flk-1 expression in GH3 cells following varied exposure to betaFGF, EGF, and TGFbeta1. Immunofluorescence labelling and laser scanning cytometry were used to measure changes in VEGF and Flk-1 expression. Results showed that betaFGF, EGF and TGFbeta up-regulated the VEGF/FLK-1 receptor system. Distinct patterns of activation were detected. At 2 hours, EGF and TGFbeta caused no significant changes in VEGF and Flk-1 expression; however, betaFGF up-regulated VEGF expression in 99% of cells but only induced modest changes in Flk-1 overexpression. A similar percentage of cells overexpressed VEGF after 24-hour incubation with betaFGF, but more prominent Flk-1 overexpression was detected. At 24 hours, EGF and TGFbeta1 induced a significant increase in both VEGF and Flk-1 expression. In summary, our findings show that VEGF/Flk-1 expression in pituitary cells may be altered by different growth factors. This may affect angiogenesis and the progression of pituitary tumors.

Effects of oestradiol and tamoxifen on VEGF, soluble VEGFR-1, and VEGFR-2 in breast cancer and endothelial cells

Angiogenesis is regulated by the balance between pro- and antiangiogenic factors. Vascular endothelial growth factor (VEGF), acting via the receptors VEGFR-1 and VEGFR-2, is a key mediator of tumour angiogenesis. The soluble form of the VEGF receptor-1 (sVEGFR-1) is an important negative regulator of VEGF-mediated angiogenesis. The majority of breast cancers are oestrogen dependent, but it is not fully understood how oestrogen and the antioestrogen, tamoxifen, affect the balance of angiogenic factors. Angiogenesis is a result of the interplay between cancer and endothelial cells, and sex steroids may exert effects on both cell types. In this study we show that oestradiol decreased secreted sVEGFR-1, increased secreted VEGF, and decreased the ratio of sVEGFR-1/VEGF in MCF-7 human breast cancer cells. The addition of tamoxifen opposed these effects. Moreover, human umbilical vein endothelial cells (HUVEC) incubated with supernatants from oestradiol-treated MCF-7 cells exhibited higher VEGFR-2 levels than controls. In vivo, MCF-7 tumours from oestradiol+tamoxifen-treated nude mice exhibited decreased tumour vasculature. Our results suggest that tamoxifen and oestradiol exert dual effects on the angiogenic environment in breast cancer by regulating cancer cell-secreted angiogenic ligands such as VEGF and sVEGFR-1 and by affecting VEGFR-2 expression of endothelial cells.

Sex steroid regulation of angiogenesis in breast tissue

Angiogenesis is essential for normal function in the female reproductive tract and a prerequisite for growth and metastasis of solid tumors. Several factors, both inducers and inhibitors, play essential roles in the regulation of the angiogenic process. Exposure to sex steroids increases the risk of breast cancer but the mechanisms are poorly understood and the importance of angiogenesis in breast carcinogenesis is undefined. In the female reproductive tract ovarian hormones tightly regulate angiogenesis. The breast is also a target organ for sex steroids but very little is known about sex steroid effects on angiogenesis in normal breast tissue and breast cancer. In this review several regulators of angiogenesis, and their relation to sex steroids, in breast tissue are discussed. Increased knowledge in this area is of utmost importance for future therapeutic treatment options and for breast cancer prevention.

Tumor-specific expression of vascular endothelial growth factor receptor 2 but not vascular endothelial growth factor or human epidermal growth factor receptor 2 is associated with impaired response to adjuvant tamoxifen in premenopausal breast cancer

PURPOSE

Vascular endothelial growth factor A (VEGF-A) and vascular endothelial growth factor receptor 2 (VEGFR2) are often coexpressed in breast cancer, and potentially affect cellular pathways and key proteins such as the estrogen receptor (ER) targeted by endocrine treatment. We therefore explored the association between adjuvant tamoxifen treatment in breast cancer and expression of VEGF-A and VEGFR2, as well as human epidermal growth factor receptor 2 (HER2), which represents a candidate gene product involved in tamoxifen resistance.

PATIENTS AND METHODS

Immunohistochemical expression of tumor-specific VEGF-A, VEGFR2, and HER2 was evaluated in tumor specimens from premenopausal breast cancer patients randomly assigned to 2 years of tamoxifen or no treatment (n = 564), with 14 years of follow-up. Hormone receptor status was determined in 96% of the tumors.

RESULTS

VEGF-A, VEGFR2, and HER2 were assessable in 460, 472, and 428 of the tumors, respectively. In patients with ER-positive and VEGFR2-low tumors, adjuvant tamoxifen significantly increased recurrence-free survival (RFS; [HR] hazard ratio for RFS, 0.53; P = .001). In contrast, tamoxifen treatment had no effect in patients with VEGFR2-high tumors (HR for RFS, 2.44; P = .2). When multivariate interaction analyses were used, this difference in treatment efficacy relative to VEGFR2 expression status was statistically significant for both ER-positive (P = .04) plus ER-positive and progesterone receptor-positive tumors. We found no significant difference in tamoxifen treatment effects in relation to VEGF-A or HER2 status.

CONCLUSION

Tumor-specific expression of VEGFR2 was associated with an impaired tamoxifen effect in hormone receptor-positive premenopausal breast cancer. Tamoxifen in combination with VEGFR2 inhibitors might be a novel treatment approach for VEGFR2-expressing breast cancer, and such a treatment might restore the tamoxifen response.

Prolactin-induced expression of vascular endothelial growth factor via Egr-1

Angiogenesis is a dynamic process regulated by both local and systemic factors. Among these is vascular endothelial growth factor (VEGF), a potent effector of angiogenesis and vascular permeability. Previously we showed that VEGF is temporally and spatially regulated in the mouse mammary gland during development and lactation. Given the functions of prolactin (PRL) during these stages and the supporting role of the vasculature, we investigated the regulation of VEGF by PRL. Treatment of HC11 mouse mammary epithelial and Nb2 rat lymphoma cells with PRL induced VEGF expression. Deletion and mutation analysis identified a GC-rich region in the proximal region of the VEGF promoter that constitutively bound Sp1 and PRL-induced Egr-1. These sites conferred PRL-responsiveness leading to increased VEGF transcription. The induction of VEGF by PRL was PRL receptor-, Jak2- and MAP kinase kinase-dependent. Our results indicate that PRL induces VEGF expression through Egr-1, and implicates VEGF as an intermediary of PRL-regulated angiogenesis.

Inhibition of VEGF receptors significantly impairs mammary cancer growth in C3(1)/Tag transgenic mice through antiangiogenic and non-antiangiogenic mechanisms

Cancer growth and progression is often critically influenced by the production of vascular endothelial growth factor (VEGF), a key mediator of angiogenesis. VEGF produced by tumor cells stimulates endothelial cell growth through the binding and activation of the KDR/Flk-1 receptor (VEGFR-2) on endothelial cells. Recently, some human breast cancer epithelial cells have been shown to express VEGF receptors, suggesting a potential autocrine-mediated growth stimulation of a subset of cancers by VEGF. We demonstrate that mammary tumors in the C3(1)/Tag transgenic model express VEGF and VEGF receptors and tumor growth is stimulated by this autocrine mechanism. GW654652, an indazolylpyrimidine, is a VEGFRs tyrosine kinase inhibitor that dramatically reduces both angiogenesis and tumor cell growth in this model, as demonstrated using both in vitro and in vivo assays. GW654652 significantly decreased cell proliferation and induced apoptosis in human umbilical vein endothelial cells and M6 mammary tumor cells derived from C3(1)/Tag (Tag: simian virus 40 T-antigen) transgenic mice. A 75% reduction in VEGF-induced angiogenesis was observed with GW654652 using the chick chorioallantoic membrane assay, whereas GW654652 produced an approximately 85% reduction in angiogenesis as assessed by the Matrigel plug assay. A profound inhibitory effect on tumor growth in the C3(1)/Tag transgenic model of human breast cancer was observed with oral administration of GW654652 as measured by delayed tumor onset, decreased multiplicity, reduced tumor volume, and extended animal survival. The antitumor effects of GW654652 were associated with reduced tumor vascularization and no apparent toxicity. Tumor growth, however, rapidly advanced following cessation of treatment. This is the first demonstration that a VEGF receptor inhibitor, GW654652, has a strong inhibitory effect on angiogenesis and tumor progression in a transgenic model of mammary cancer, suggesting that this is a useful approach for preclinical testing of such agents.

Tumor-specific VEGF-A and VEGFR2 in postmenopausal breast cancer patients with long-term follow-up. Implication of a link between VEGF pathway and tamoxifen response

Vascular endothelial growth factor (VEGF-A) is considered a prognostic indicator for clinical outcome in breast cancer. Conflicting results nevertheless exist and there is a need for larger studies including untreated patients in order to clarify the importance of tumor-specific VEGF-A regarding prognosis as well as potential links to predictive treatment information. VEGF-A and its receptor, vascular endothelial growth receptor 2 (VEGFR2), were therefore analyzed by immunohistochemistry in postmenopausal breast cancers enrolled in a clinical trial where patients were randomized to adjuvant tamoxifen treatment (n = 124) for 2 years or no treatment (n = 127) with a median follow-up of 18 years. The tumors were arranged in a tumor tissue microarray system enabling parallel analysis of the angiogenic factors and hormone receptor status. Tumor-specific expression of VEGFR2 correlated strongly with expression of VEGF-A and progesterone receptor (PR) negativity, whereas VEGF-A was not associated with hormone receptor status. Among patients with estrogen receptor (ER) positive (fraction > 10%) tumors, there was a statistically significant tamoxifen response in VEGF-A negative tumors at both 10-year and 18-year disease-free survival (DFS), contrasting to VEGF-A positive tumors who had no beneficial effect of tamoxifen. A treatment-interaction variable indicated a marked difference in tamoxifen response depending on VEGFA-status in terms of DFS at 10 and 18 years of follow-up, p = 0.046 and p = 0.039, respectively. VEGFR2 status did not yield significant predicitve information for tamoxifen response in patients with ER fraction > 10%, whereas in patients with ER fraction > 90% both VEGF-A and VEGFR2 status were associated with tamoxifen treatment effect.

An angiogenic switch in breast cancer involves estrogen and soluble vascular endothelial growth factor receptor 1

Estrogen is involved in breast tumorigenesis, but the precise mechanisms for its oncogenic and angiogenic actions are poorly understood. Angiogenesis is regulated, in part, by these critical components: vascular endothelial growth factor (VEGF) and its two receptors (VEGFR-1 and VEGFR-2). VEGFR-2 is a positive angiogenic signal transducer, whereas VEGFR-1, especially its soluble form (soluble VEGFR-1), is a negative regulator of VEGF availability. We found that breast epithelial cells express soluble VEGFR-1 and hypothesized that because estrogen can regulate expression of members of the VEGF family, it might stimulate angiogenesis in breast cancer by decreasing expression of soluble VEGFR-1. Soluble VEGFR-1 expression decreased in estrogen receptor (ER)-positive but not in ER-negative breast cancer cell lines treated with estrogen. Pretreatment of the cells with the ER antagonist ICI 182,780 blocked the effect. The estrogen-mediated decrease in soluble VEGFR-1 expression was accompanied by a statistically significant increase in angiogenesis in vivo. Our data suggest that inhibition of soluble VEGFR-1 expression represents a novel mechanism--an estrogen-driven angiogenic switch--possibly responsible for breast carcinoma progression.

Novel sensitizing agents: Potential Contribution of COX-2 inhibitor for endocrine therapy of breast cancer

Enhancement of the therapeutic effect of conventional drugs is currently an active treatment strategy for breast cancer, as shown in the clinical application of trastuzumab with chemotherapeutic agents, which prolonged survival even for metastatic disease. Cyclo-oxygenase 2(COX-2)inhibitors, which are chemoprevention agents for familial polyposis coli, are now contributing to this strategy in combination with chemotherapeutic and endocrine drugs. As an endocrine application, overexpression of COX-2 contributes to increased expression of aromatase in the breast tumor. In addition, it is also known to promote rich micro-vessels within the tumor through up-regulation of prostaglandin E2(PGE2), which can induce vascular endothelial growth factor(VEGF)and basic fibroblast growth factor(bFGF)in cancer cells, and can directly modulate endothelial cell proliferation. Since both rich vasculature and accelerated estrogen synthesis are thought to contribute to unfavorable conditions for the response to endocrine therapy, inhibiting COX-2 with COX-2 inhibitors is a promising strategy to potentiate endocrine therapy.

Hypoxia-inducible factor 1α/vascular endothelial growth factor axis in astrocytomas. Associations with microvessel morphometry, proliferation and prognosis

Hypoxia-inducible factor (HIF)-1alpha is a transcription factor that promotes ischaemia-driven angiogenesis. The aim of this study was to determine the relation of HIF-1alpha to vascular endothelial growth factor (VEGF; an important angiogenic molecule in brain tumours), p53 expression, angiogenesis, proliferative potential and clinical outcome in a large series of diffuse astrocytomas. Expression of HIF-1alpha, VEGF, Ki-67 (a proliferation-associated marker) and p53 was determined immunohistochemically in 83 adult patients with supratentorial diffuse astrocytomas. Microvessels, highlighted by means of anti-CD34 immunohistochemistry, were enumerated with computer-assisted image analysis. Although HIF-1alpha and VEGF were expressed in the majority of cases, their levels increased significantly with increasing grade and proliferative potential. HIF-1alpha positively correlated with microvessel counts and VEGF with total vascular area and the presence of rounder vessel sections. There was a positive correlation of VEGF with p53 expression in astrocytomas and anaplastic astrocytomas. In univariate analysis, both VEGF and HIF-1alpha were associated with shortened survival in the entire cohort, but lost significance when grades II/III and grade IV were analysed separately. Multivariate analysis revealed that the combination of HIF-1alpha with grade was a significant prognostic indicator. HIF-1alpha expression may be used to refine the prognostic information provided by grade in patients with diffuse astrocytomas. Its adverse prognostic effect is most likely mediated by hypoxia, the driving force for HIF-1alpha accumulation.

Clinical relevance of VEGF receptors 1 and 2 in patients with chronic myelogenous leukemia

Vascularity is increased in the bone marrow of patients with chronic myeloid leukemia (CML) and high vascular endothelial growth factor (VEGF) levels correlate with worse survival. We analyzed the significance of VEGF-receptor 1 (VEGF-R1) and VEGF-R2 levels in bone marrow samples from 170 CML patients (137 chronic, 24 accelerated, and 9 blastic phase). Median VEGF-R1 and VEGF-R2 levels were 4.66 and 2-fold, respectively, that in normal control samples. Receptor levels did not correlate with disease phase or other host and disease features examined. Chronic phase CML patients with increased VEGF-R2 levels had significantly inferior survival than patients without receptor up-regulation (P=0.009). Patients in accelerated/blastic phase CML with elevated VEGF-R2 expression had marginally worse survival (P=0.05). In contrast, high VEGF-R1 levels did not correlate with a specific CML phase, characteristic, or outcome. Our findings support VEGF-R2 over-expression as an independent prognostic indicator for shortened survival in patients with CML.

Inhibition of breast carcinoma and trophoblast cell invasiveness by vascular endothelial growth factor

Vascular endothelial growth factor (VEGF) is a potent endothelial cell mitogen and angiogenic growth factor that enhances endothelial cell invasion through the extracellular matrix (ECM). While various cell types express VEGF receptors, little is known about the biological actions of VEGF on nonendothelial cells. Therefore, the main objective of the present study was to determine the effect of VEGF on the in vitro invasiveness and proliferation of human MDA-MB-231 breast carcinoma cells and human HTR-8/SVneo trophoblast cells. Reverse-transcriptase polymerase chain reaction analysis demonstrated the presence of transcripts encoding VEGF receptors (VEGFR) -1, -2, and -3 as well as neuropilins-1 and -2 in the trophoblast cells, and the presence of transcripts encoding VEGFR-2 and neuropilins-1 and -2 in the breast carcinoma cells. Both cell lines also expressed transcripts for VEGF-A, -B, -C and -D, as well as for placenta growth factor (PlGF). Although incubation with exogenous VEGF-A(165) or VEGF-A(121) did not affect the rate of proliferation of either the trophoblast or the breast carcinoma cells, incubation with these molecules reduced their ability to invade through reconstituted ECM (Matrigel). The effect of VEGF-A(165) on the invasiveness of both cell lines was inhibited by the inclusion of a neutralizing antibody to VEGF. Exogenous VEGF-A(165) also decreased the cell surface expression of the urokinase-type plasminogen activator (a molecule required for invasion) by the breast carcinoma and trophoblast cells. These results indicate that the biological actions of VEGF on certain cell types may differ from the effects of this molecule on vascular endothelial cells, and therefore are relevant to angiogenesis-based therapies.

Expression and prognostic relevance of vascular endothelial growth factor (VEGF) and its receptor (FLT-1) in nephroblastoma

AIMS

To investigate the prognostic relevance of vascular endothelial growth factor (VEGF) and its receptor Flt-1 in nephroblastoma and whether tumour microvessel density (MVD) immunoreactivity, determined by the CD31 antigen, is related to the expression of VEGF and Flt-1.

METHODS

The expression of VEGF and Flt-1 and MVD were investigated by means of immunohistochemical analysis in 62 Wilms's tumours. Patients were treated preoperatively with chemotherapy and had a mean follow up of 5.7 years.

RESULTS

In general, VEGF and Flt-1 were expressed in normal kidney parenchyma and to a variable extent in the three main components of Wilms's tumour, namely: the blastemal, epithelial, and stromal cells. In tumour tissue, 52% and 47% of blastemal cells were positive for VEGF and Flt-1, respectively. A non-significant correlation was found between the expression of VEGF and Flt-1 in blastemal and epithelial cells and the clinicopathological stage. MVD was significantly higher in VEGF and Flt-1 positive tumours than in VEGF and Flt-1 negative tumours. Univariate analysis showed that the expression of VEGF and Flt-1 in blastemal cells was indicative of clinical progression and tumour specific survival. In addition, MVD expression was indicative of clinical progression. Epithelial staining was of no prognostic value. In a multivariate analysis, VEGF protein expression by blastemal cells was an independent prognostic marker for clinical progression.

CONCLUSIONS

These results indicate that VEGF and Flt-1 protein expression are closely related to MVD and seem to be an important predictor for poor prognosis in treated patients with Wilms's tumour. Therefore, the expression of these molecules in primary Wilms's tumour may be useful in identifying those patients at high risk of tumour recurrence and in guiding antiangiogenic treatment.

Sex hormone-induced mammary carcinogenesis in female Noble rats: detection of differentially expressed genes

Breast cancer is the most common cancer and the second most frequent cause of cancer death in women. Epidemiological data has recognized that an increased cumulative exposure to estrogen is the common tie linking most of the established risk factors for breast cancer. Sex hormone-induced mammary gland carcinogenesis of the Noble rat (using testosterone and 17beta-estradiol) resembles that of the human counterpart in its growth pattern as well as the histopathology of the tumors induced. This model may provide a paradigm for examination of genetic alterations and changes in gene expression between different histological groups and to make inferences about the role of known and putative oncogenes and tumor suppressor genes. We studied the gene expression profile during sex hormone-induced mammary carcinogenesis using a cDNA array technique; the results were further confirmed by RT-PCR, western blotting and immunohistochemical analyses. From the 10 differentially expressed genes identified, we have studied four highly overexpressed genes, two cell cycle/growth control regulators, the cyclins D1 and D2, a growth factor, IGF-2 and a cytokine TNF-alpha. Cyclins D1 and D2 were highly expressed in the nuclei of carcinoma cells but at low levels in the nuclei of the hyperplastic and normal mammary tissue. IGF-2 was found to expressed in the cytoplasm of the carcinoma cells but not in the stromal cells. Western blot showed expression of big IGF-2 consistent with the tumor derived truncated forms of pro-IGF-2. The matured circulating IGF-2 at 7.5 kDa identified in the serum was not expressed in any of the breast tissue samples. TNF-alpha expression was found not only in the macrophages but also in the mammary carcinoma cells. The result of the present study provides some information on the molecular basis of this sex hormone-induced mammary carcinogenesis and the role of these proteins in tumor progression.

Resistance to mammary carcinogenesis in Copenhagen rats: potential roles of vascular endothelial growth factor and mast cells

The Copenhagen (COP) rat is extremely resistant to mammary cancer induction by carcinogens. Multiple genetic loci have been linked to the resistant phenotype, but the mechanisms underlying the resistance still remain unknown. Evidence has shown that the acquisition of angiogenic capacity is critical for tumor development. We, therefore, decided to investigate whether administration of angiogenic factor would enhance mammary carcinogenesis in the COP rat. Vascular endothelial growth factor (VEGF) was administered in a sustained releasing formula to pubescent female COP rats 2 weeks after N-nitroso-N-methylurea (NMU) treatment. Six months after NMU exposure, we found no difference in mammary tumor incidence between VEGF treated animals and controls. Analysis of VEGF expression, however, revealed different expression patterns in mammary epithelial cells of various origins. Mammary epithelial cells from pubescent susceptible Buffalo (BUF) and COP rats expressed substantial levels of VEGF messages, whereas cells prepared from 230-day-old rats showed negligible levels of VEGF mRNA. We also demonstrated that mammary epithelial cells from tumors developed in susceptible BUF rats expressed VEGF, whereas VEGF messages were barely detectable in tumors induced in COP rats. Furthermore, enlargement of the intramammary lymph nodes with prominent mast cells was observed in NMU treated COP rats, but not in NMU treated BUF rats. These results suggest that down regulation of VEGF expression is insufficient for resistance to mammary carcinogenesis, and that enhanced immune response, as evidenced by intramammary lymph node enlargement with mast cell accumulation, may also play a role in conferring resistance in the COP rat.

No effect of a high-fat diet on promotion of sex hormone-induced prostate and mammary carcinogenesis in the Noble rat model

Results of international correlation and migrant studies suggest that dietary fat promotes carcinogenesis in hormone-sensitive sites, but this is disputed. In the present study, we used a Noble rat model of sex hormone-induced cancers to examine the effect of a high-fat diet on the incidence and latency of prostate and mammary cancer in male (n 139) and female (n 72) animals respectively. We also measured alpha-tocopherol levels in female breast tissue to determine whether a high intake of polyunsaturated fatty acids depletes antioxidant defence in target tissues, providing a possible potentiating mechanism for carcinogenesis. Results showed a very high incidence of hormone-induced adenocarcinomas of prostate and mammary gland, irrespective of diet. There was no difference in the pattern of carcinogenesis in different prostatic locations, weight of the prostate, or weight gain between male rats on the high-fat diet compared with the control (standard, low-fat) diet. In female rats, the incidence of mammary cancer and the body-weight gain were the same in both dietary groups, and breast alpha-tocopherol was also unaffected by dietary fat intake. Our present results are supportive of recent cohort studies that reported no significant association between intake of fat and the development of human prostate and breast cancer, and do not support a role for dietary fat in promoting sex hormone-induced prostate and mammary carcinogenesis.

Brn-3a, a neuronal transcription factor of the POU gene family: indications for its involvement in cancer and angiogenesis

Brn-3a, a member of the POU gene family (so-called because of the similarity with the group of transcription factors Pit, Oct, and Unc), was found in neuronal cells engaged in the transcription activity of the p1 and p2 promoters of the most powerful antiapoptotic gene, namely, Bcl-2. The alternative splicing of Brn-3a mRNA produces two molecular forms: a longer, Bcl-2 transactivating form, and a shorter inactive form, lacking 84 AA in the aminoterminus. In neuronal cells, following Brn-3a gene transfection and superexpression, an increase of 30 fold of the Bcl-2 protein occurs, leading to apoptosis protection. However, recent works demonstrate that Brn-3a expression is not restricted to neuronal cells, as its activity was detected also in cancer cells of non-neuronal nature. Looking for mechanisms linking Brn-3a to carcinogenesis, we discuss the role of this transcription factor in influencing Bcl-2/p53 antagonism and Bcl-2/VEGF induction of tumor angiogenesis, concluding this review with a proposal for the oncogenic nature of Brn-3a.

Inhibition of the mammary carcinoma angiogenic switch in C3(1)/SV40 transgenic mice by a mutated form of human endostatin

Cancer therapies based on the inhibition of angiogenesis by endostatin have recently been developed. We demonstrate that a mutated form of human endostatin (P125A) can inhibit the angiogenic switch in the C3(1)/Tag mammary cancer model. P125A has a stronger growth-inhibitory effect on endothelial cell proliferation than wild-type endostatin. We characterize the angiogenic switch, which occurs during the transition from preinvasive lesions to invasive carcinoma in this model, and which is accompanied by a significant increase in total protein levels of vascular endothelial growth factor (VEGF) and an invasion of blood vessels. Expression of the VEGF(188) mRNA isoform, however, is suppressed in invasive carcinomas. The VEGF receptors fetal liver kinase-1 (Flk-1) and Fms-like tyrosine kinase-1 (Flt-1) become highly expressed in epithelial tumor and endothelial cells in the mammary carcinomas, suggesting a potential autocrine effect for VEGF on tumor cell growth. Angiopoietin-2 mRNA levels are also increased during tumor progression. CD-31 (platelet-endothelial cell adhesion molecule [PECAM]) staining revealed that blood vessels developed in tumors larger than 1 mm The administration of P125A human endostatin in C3(1)/Tag females resulted in a significant delay in tumor onset, decreased tumor multiplicity and tumor burden and prolonged survival of the animals. Endostatin treatment did not reduce the number of preinvasive lesions, proliferation rates or apoptotic index, compared with controls. However, mRNA levels of a variety of proangiogenic factors (VEGF, VEGF receptors Flk-1 and Flt-1, angiopoietin-2, Tie-1, cadherin-5 and PECAM) were significantly decreased in the endostatin-treated group compared with controls. These results demonstrate that P125A endostatin inhibits the angiogenic switch during mammary gland adenocarcinoma tumor progression in the C3(1)/Tag transgenic model.

Edema cerebral em meningiomas: aspectos radiológicos e histopatológicos

Diversos fatores têm sido associados ao desenvolvimento de edema peritumoral nos meningiomas. Foram estudados os aspectos radiológicos e anátomo-patológicos de 51 meningiomas intracranianos operados no Hospital Universitário Clementino Fraga Filho (HUCFF). Dois terços dos meningiomas apresentavam edema perilesional. O tamanho dos meningiomas correlacionou-se com a presença de edema, sendo mais frequente nos meningiomas grandes (>4cm). A localização parece, também, influenciar no desenvolvimento do edema peritumoral, sendo mais acentuado nos meningiomas da asa do esfenóide e incomum nos meningiomas do tubérculo selar. Os subtipos histológicos de meningioma não se correlacionaram com a intensidade do edema peritumoral. Dos diversos mediadores químicos descritos na literatura recente relacionados ao desenvolvimento de edema peritumoral em tumores intracranianos, destaca-se o fator de crescimento do endotélio vascular (VEGF). A expressão nos meningiomas do VEGF e de seu receptor flk-1 foi estudada com técnica imuno-histoquímica, demonstrando a sua expressão nas células tumorais.

Expression of the vascular endothelial growth factor receptor-2/Flk-1 in breast carcinomas: correlation with proliferation

Vascular endothelial growth factor (VEGF) and its receptor Flk-1/KDR play an important role in vascular permeability and tumor angiogenesis. Prompted by the hypothesis that VEGF/Flk-1 system may have regulatory roles in breast carcinogenesis, we investigated the expression of Flk-1 in 141 invasive breast carcinomas in correlation with clinical and immunohistochemical prognostic parameters, including proliferation indices like Ki-67 and Topoisomerase IIalpha (Topo-IIalpha). The immunohistochemical avidin-biotin-peroxidase method was performed on paraffin sections for the detection of Flk-1, p53, Bcl-2, c-erbB-2, Ki-67, Topo-IIalpha, ER, and PR. Flk-1 was detected in 91 of 141 (64.5%) of invasive breast carcinomas showing a widespread cytoplasmic expression in most of the neoplastic cells. Flk-1 expression was correlated with the menopausal status (P = 0.051) of the patient and the nuclear grade of the invasive breast carcinoma (P = 0.003), but demonstrated no correlation with histologic grade, stage, and patient survival. It is interesting that Flk-1 expression demonstrated a significant correlation with 2 well-established proliferation indices, Ki-67 (P = 0.037) and topo-IIalpha (P = 0.009), whereas there was no correlation with the expression of ER, PR, p53, Bcl-2, and c-erbB-2. Moreover, Flk-1 expression showed an inverse correlation with TIMP-1 mRNA localization in intratumoral stromal cells (P = 0.013). In conclusion, the significant correlation of Flk-1 expression in invasive breast carcinomas with proliferation indices like Ki-67 and topo-IIalpha suggests that VEGF may exert a growth factor activity on mammary cancer cells through its receptor Flk-1. On the other hand, the inverse correlation of Flk-1 with TIMP-1 mRNA in intratumoral stromal cells supports the notion that TIMP-1 may have an inhibitory role on angiogenesis.

Clinical relevance of vascular endothelial growth factor receptors 1 and 2 in acute myeloid leukaemia and myelodysplastic syndrome

We have previously reported that high levels of cellular vascular endothelial growth factor (VEGF) protein correlated with short survival of patients with acute myeloid leukaemia (AML). As VEGF exerts its effects via two receptors, VEGF receptor 1 (VEGFR-1) and VEGFR-2, we evaluated the significance of VEGFR-1 and VEGFR-2 protein levels in AML and myelodysplastic syndrome (MDS), and their relationship to VEGF protein levels. Western blot analysis and radioimmunoassay confirmed and quantified specific protein levels in bone marrow samples from 41 MDS and 66 AML previously untreated patients. VEGFR-1 levels were significantly higher in AML than in MDS (P = 0.0004), but no significant difference was found in the VEGFR-2 levels (P = 0.5). No significant correlation between VEGFRs levels and duration of survival was found. VEGF protein levels were significantly higher in MDS than in AML (P < 0.0001). A Cox proportional-hazard regression model showed increasing VEGF levels to significantly correlate with shorter survival of patients with MDS (P = 0.008), a finding similar to our previous report of the inverse relationship between VEGF levels and survival of AML patients. We found a significant correlation between VEGF and VEGFR-2 levels in both AML and MDS (P < 0.0000001 andP < 0.0002 respectively) but not between VEGF and VEGFR-1 levels. These data suggest that VEGF expression, rather than the expression of its receptors, is the determining factor in the biological behaviour of AML and MDS, and that VEGFRs are differentially expressed in AML and MDS.

Importance of vascular phenotype by basic fibroblast growth factor, and influence of the angiogenic factors basic fibroblast growth factor/fibroblast growth factor receptor-1 and ephrin-A1/EphA2 on melanoma progression

The expression of several angiogenic factors and receptors was examined in a series of vertical growth phase cutaneous melanomas using high-throughput tissue microarray technology and immunohistochemistry. The results were correlated with microvessel density, clinicopathological features, and patient survival. Expression of basic fibroblast growth factor (bFGF) was significantly associated with increased microvessel density. Also, we found an independent prognostic importance of vascular phenotype by endothelial cell expression of bFGF; cases with positive vessels had the best prognosis and these tumors revealed a low frequency of vascular invasion (14%) when compared with bFGF-negative vessels (47%). This bFGF-negative phenotype was significantly increased in metastatic lesions. Strong tumor cell expression of FLT-4, ephrin-A1, and EphA2 was associated with increased melanoma thickness, and ephrin-A1 staining was related to decreased survival (P = 0.039). Expression of EphA2 in tumor cells was associated with increased tumor cell proliferation (Ki-67 positivity), indicating possible autocrine growth stimulation. Thus, our findings indicate the presence of phenotypic diversity among tumor-associated vessels, and subgroups defined by bFGF expression may be of clinical importance. bFGF was associated with microvessel density, whereas the ephrin-A1/EphA2 pathway might also be important for tumor cell proliferation and patient survival.

Clinical experience with angiogenesis signaling inhibitors: focus on vascular endothelial growth factor (VEGF) blockers

Angiogenesis is required for tumor growth and metastasis and, therefore, represents an exciting target for cancer treatment. Angiogenesis is a complex process that is tightly regulated by pro- and anti-angiogenic growth factors. Physiologic angiogenesis takes place during tissue growth and repair, during the female reproductive cycle, and during fetal development. Pathologic angiogenesis is characterized by either excessive (eg, cancer) or inadequate (eg, coronary artery disease) neovascularization. Angiogenesis occurs in a series of complex and interrelated steps that involve the release of pro-angiogenic growth factors, such as vascular endothelial growth factor (VEGF). VEGF regulates both vascular proliferation and permeability, and functions as an anti-apoptotic factor for newly formed blood vessels. The biological effects of VEGF are mediated by two receptors, VEGF-1 and VEGF-2, whose expression is largely limited to the vascular endothelium. VEGF is often expressed in tumors at substantially increased levels. It is expressed in response to hypoxia, oncogenes, and other cytokines, and its expression is associated with poor prognosis in several types of cancer. Several different strategies have been used to inhibit VEGF, including anti-VEGF monoclonal antibodies (eg, bevacizumab) and agents that inhibit the VEGF receptor (eg, SU5416). Both types of agents have tolerable side effects and have shown promise when evaluated in a wide range of tumor types. Angiogenesis, the role of VEGF in angiogenesis and malignancy, and strategies for cancer treatment with VEGF inhibitors are discussed.

Conditional gene targeting for cancer gene therapy

Current treatment of solid tumors is limited by severe adverse effects, resulting in a narrow therapeutic index. Therefore, cancer gene therapy has emerged as a targeted approach that would significantly reduce undesired side effects in normal tissues. This approach requires a clear understanding of the molecular biology of both the malignant clone and the biological vectors that serve as vehicles to target cancer cells. In this review we discuss novel approaches for conditional gene expression in cancer cells. Targeting transgene expression to malignant tissues requires the use of specific regulatory elements including promoters based on tumor biology, tissue-specific promoters and inducible regulatory elements. We also discuss the regulation of both replication and transgene expression by conditionally-replicative viruses. These approaches have the potential to restrict the expression of transgenes exclusively to tissues of interest and thereby to increase the therapeutic index of future vectors for cancer gene therapy.

Expresson of vascular endothelial growth factor, its receptors (FLT-1, KDR) and TSP-1 related to microvessel density and patient outcome in vertical growth phase melanomas

Microvessel density (MVD) was estimated in a series of 202 vertical growth phase (VPG) melanomas and 68 corresponding metastases, using a marker for angiogenic endothelial cells (CD105) and Factor-VIII. The expression pattern of vascular endothelial growth factor (VEGF), FLT-1, KDR and thrombospondin-1 (TSP-1) was studied by immunohistochemistry, in situ hybridization and reverse-transcriptase polymerase chain reaction. CD105 stained significantly less vessels, but gave only limited additional prognostic information compared with Factor-VIII, and MVD was an independent prognostic factor for both markers. Ninety-eight percent of all cases showed expression of VEGF, and higher expression was found significantly more frequent in thinner and less vascularized tumors. Possible autocrine loops were suggested by co-expression of VEGF and its two receptors in tumor cells, and by a significant correlation between KDR and tumor cell proliferation (Ki-67) in the subgroup of thicker tumors. Staining of VEGF receptors in endothelium was not correlated with MVD. Strong expression of TSP-1 in tumor stroma was found in 43% of the primary tumors, and was significantly correlated with increased thickness, proliferation and MVD, as well as decreased survival. These data suggest that MVD is associated with prognosis in cutaneous melanomas, and that the VEGF system and particularly TSP-1 seem to be involved in the regulation of angiogenesis and progression of these tumors.

The expression of vascular endothelial growth factor C and its receptors in non-small cell lung cancer

Expression of vascular endothelial growth factor (VEGF)-C and that of its receptors were assessed in non-small cell lung cancer. Immunohistochemistry revealed positive VEGF-C expression in 38.7% (24/62) of the patients studied. A significant positive correlation was found between VEGF-C in cancer cells and VEGF receptor-3 (VEGFR-3) in vascular endothelial cells, but not between VEGF-C in cancer cells and VEGFR-2 in endothelial cells. In this cohort of lung cancer patients, VEGF-C expression was significantly associated with lymph node metastasis, lymphatic vessel invasion, and worse outcomes after the operation. Although the independent prognostic impact of VEGF-C and VEGFR-3 was not clear, VEGFR-2 expression in endothelial cells retained the independency as the prognostic indicator. In light of these findings, we conclude that VEGF-C plays an important role in lymphatic invasion/metastasis and tumour progression in non-small cell lung cancer.

Effect of placenta growth factor-1 on proliferation and release of nitric oxide, cyclic AMP and cyclic GMP in human epithelial cells expressing the FLT-1 receptor

We investigated the effect of placenta growth factor-1 (P1GF-1) on cell growth and on the release of nitric oxide (NO), cyclic AMP (cAMP) and cyclic GMP (cGMP) in human malignant epithelial cells. A noteworthy increase in proliferation was induced in choriocarcinoma cells (BeWo) by P1GF-1 treatment, while breast cancer cells (CG-5) were minimally affected. Western blotting and immunocytochemistry demonstrated the expression of the P1GF-1 receptor fms-like tyrosine kinase-1 (Flt-1) in these models. NO was released in the BeWo culture medium as a result of P1GF-1 treatment, with maximal induction occurring after 6 h. Enhanced cAMP levels were observed after 80 min-6 h, while the amounts of cGMP produced were undetectable. In summary, PIGF-1 stimulates the proliferation of cell types that express Flt-1, other than endothelial cells. In BeWo cells, this effect is preceded by the induction of NO and cAMP as probable downstream effectors of Flt-1 activation.

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.