Estrogen regulates vascular endothelial growth/permeability factor expression in 7,12-dimethylbenz(a)anthracene-induced rat mammary tumors

Phase II study of apatinib plus exemestane in estrogen receptor-positive, human epidermal growth factor receptor 2-negative metastatic breast cancer

PURPOSE

Apatinib is a tyrosine kinase inhibitor targeting vascular endothelial growth factor receptor (VEGFR)-2. This study was conducted to assess the efficacy and safety of apatinib combined with exemestane in patients with estrogen receptor-positive (ER+)/human epidermal growth factor receptor 2-negative (HER2-) metastatic breast cancer (MBC).

METHODS

This single-center, single-arm phase II study enrolled patients with ER+/HER2- MBC progressed on previous letrozole or anastrozole. Stratified analysis was performed according to the number of chemotherapy regimens for metastatic disease. The primary endpoint was progression free survival (PFS). Secondary endpoints included objective response rate (ORR), disease control rate (DCR), clinical benefit rate (CBR), overall survival (OS) and toxicity. Patients received apatinib at a starting dose of 500 mg/d and exemestane 25 mg/d on days 1-28 of each 4-week cycle.

RESULTS

Thirty patients were enrolled with median four prior anticancer therapies. Eighty percent of patients received chemotherapy for metastatic disease. The median PFS (mPFS) and OS were 5.6 (95%CI: 4.3-6.9) months and 15.7 (95% CI: 9.7-21.7) months, respectively. The ORR, DCR, and CBR were 21.4%, 71.4%, and 46.4%, respectively. Patients with 0-1 line chemotherapy for MBC showed a slightly longer mPFS compared to those with ≥2 lines chemotherapy (mPFS: 6.4 months vs 4.8 months, P = .090). Most of the AEs were grade 1/2. One patient (3.3%) who suffered bone marrow metastases experienced grade 4 thrombocytopenia, and 14 experienced grade 3 AEs. Fifty percent of patients were given reduced dose for apatinib.

CONCLUSIONS

Apatinib plus exemestane exhibited objective efficacy in patients with ER+/HER2- MBC who have failed multiple lines of treatment. The AEs of apatinib required close monitoring and most of patients were well tolerated.

Acute iodine deficiency induces a transient VEGF-dependent microvascular response in mammary glands involving HIF-1, ROS, and mTOR

Iodine deficiency (ID), which affects almost two billion people worldwide, is associated with breast pathologies such as fibrosis in human and induces breast atypia in animal models. Because ID induces vascular activation in the thyroid, another iodide-uptaking organ, and as breast is also sensitive to ID, we aimed to characterize ID-induced effects on the breast microvasculature in vivo and in two different breast cell lines in vitro. Virgin and lactating NMRI mice received an iodide-deficient diet and a Na⁺/I^- symporter inhibitor for 1 to 20 days. Some virgin mice were treated with vascular endothelial growth factor A (VEGF) or VEGF receptor inhibitors. In vitro, ID was induced in MCF7 and MCF12A cells by replacing the iodide-containing medium by an iodide-deficient medium. In vivo, VEGF expression was increased following ID in mammary tissues. Consequently, ID induced a transient increase in mammary gland blood flow, measured after anesthesia, in virgin and lactating mice, which was repressed by VEGF or VEGF receptor inhibitors. In MCF7 cells, ID induced a transient increase in reactive oxygen species, followed by an increase in hypoxia-inducible factor-1α (HIF-1α) protein and VEGF mRNA expression. Antioxidant N-acetylcysteine and mammalian target of rapamycin (mTOR) inhibitor blocked ID-induced HIF-1α protein increase and VEGF transcription. However, mTOR activity was not inhibited by N-acetylcysteine. Similar responses were observed in MCF12A cells. These data indicate that ID activates the canonical VEGF pathway and mTOR in breast tissues, which provides new insights to better understand the correlation between ID, vascular activation, and breast pathologies.

Estrogen decreases tight junction protein ZO-1 expression in human primary gut tissues

Females have a higher prevalence of most autoimmune diseases; however, the mechanism is unknown. In this study, we examined the expression of tight junction protein zonula occludens 1 (ZO-1) and estrogen receptor (ER)-α/β in human primary gut tissues by immunohistochemistry, immunofluorescence and qPCR. The expression of ZO-1 and ER-β but not ER-α was present in both male and female gut tissues. There was no sex difference in ER-β expression, but ZO-1 expression was decreased in females compared to males. In vitro, estrogen treatment decreased ZO-1 mRNA and protein expression, ZO-1 promoter activity, IL-6 production, and NF-κB activation in human primary gut tissues or the Caco-2 cells, but increased the ER-β expression in Caco-2 cells. Consistently, plasma IL-6 levels in females were reduced relative to males in vivo. Our finding indicates that estrogen may play a role in gut tight junction expression and permeability.

Phase III Trial Evaluating Letrozole As First-Line Endocrine Therapy With or Without Bevacizumab for the Treatment of Postmenopausal Women With Hormone Receptor-Positive Advanced-Stage Breast Cancer: CALGB 40503 (Alliance)

PURPOSE

To investigate whether anti-vascular endothelial growth factor therapy with bevacizumab prolongs progression-free survival (PFS) when added to first-line letrozole as treatment of hormone receptor-positive metastatic breast cancer (MBC).

PATIENTS AND METHODS

Women with hormone receptor-positive MBC were randomly assigned 1:1 in a multicenter, open-label, phase III trial of letrozole (2.5 mg orally per day) with or without bevacizumab (15 mg/kg intravenously once every 3 weeks) within strata defined by measurable disease and disease-free interval. This trial had 90% power to detect a 50% improvement in median PFS from 6 to 9 months. Using a one-sided α = .025, a target sample size of 352 patients was planned.

RESULTS

From May 2008 to November 2011, 350 women were recruited; 343 received treatment and were observed for efficacy and safety. Median age was 58 years (range, 25 to 87 years). Sixty-two percent had measurable disease, and 45% had de novo MBC. At a median follow-up of 39 months, the addition of bevacizumab resulted in a significant reduction in the hazard of progression (hazard ratio, 0.75; 95% CI, 0.59 to 0.96; P = .016) and a prolongation in median PFS from 15.6 months with letrozole to 20.2 months with letrozole plus bevacizumab. There was no significant difference in overall survival (hazard ratio, 0.87; 95% CI, 0.65 to 1.18; P = .188), with median overall survival of 43.9 months with letrozole versus 47.2 months with letrozole plus bevacizumab. The largest increases in incidence of grade 3 to 4 treatment-related toxicities with the addition of bevacizumab were hypertension (24% v 2%) and proteinuria (11% v 0%).

CONCLUSION

The addition of bevacizumab to letrozole improved PFS in hormone receptor-positive MBC, but this benefit was associated with a markedly increased risk of grade 3 to 4 toxicities. Research on predictive markers will be required to clarify the role of bevacizumab in this setting.

Phase III trial evaluating the addition of bevacizumab to endocrine therapy as first-line treatment for advanced breast cancer: the letrozole/fulvestrant and avastin (LEA) study

PURPOSE

To test whether combining bevacizumab, an anti-vascular endothelial growth factor treatment, with endocrine therapy (ET) could potentially delay the emergence of resistance to ET.

PATIENTS AND METHODS

A multicenter, randomized, open-label, phase III, binational (Spain and Germany) study added bevacizumab (15 mg/kg every 3 weeks) to ET (ET-B; letrozole or fulvestrant) as first-line therapy in postmenopausal patients with human epidermal growth factor receptor 2 (HER2) -negative and hormone receptor-positive advanced breast cancer. We compared progression-free survival (PFS), overall survival (OS), overall response rate (ORR), response duration (RD), time to treatment failure (TTF), clinical benefit rate (CBR), and safety.

RESULTS

From 380 patients recruited (2007 to 2011), 374 were analyzed by intent to-treat (184 patients on ET and 190 patients on ET-B). Median age was 65 years, 270 patients (72%) had Eastern Cooperative Oncology Group performance status of 0, 178 patients (48%) had visceral metastases, and 171 patients (46%) and 195 patients (52%) had received prior chemotherapy or ET, respectively. Median PFS was 14.4 months in the ET arm and 19.3 months in the ET-B arm (hazard ratio, 0.83; 95% CI, 0.65 to 1.06; P = .126). ORR, CBR, and RD with ET versus ET-B were 22% versus 41% (P < .001), 67% versus 77% (P = .041), and 13.3 months versus 17.6 months (P = .434), respectively. TTF and OS were comparable in both arms. Grade 3 to 4 hypertension, aminotransferase elevation, and proteinuria were significantly higher in the ET-B arm. Eight patients (4.2%) receiving ET-B died during study or within 30 days of end of treatment.

CONCLUSION

The addition of bevacizumab to ET in first-line treatment failed to produce a statistically significant increase in PFS or OS in women with HER2-negative/hormone receptor-positive advanced breast cancer.

Inhibitory effects of aromatase inhibitor on estrogen receptor-alpha positive ovarian cancer in mice

Background

Estrogen causes proliferation of ovarian cancer cells. Although hormone therapy with an anti-estrogen agent is an optional therapy for recurrent epithelial ovarian cancers, both basic and clinical researches are insufficient. We here examine the efficacy of an aromatase inhibitor (AI) for peritonitis carcinomatosa, the late stage of ovarian cancer.

Methods

Estrogen receptor (ER)α was assayed in four ovarian cancer cell lines by the RT-PCR method. Using ovariectomized nude mice, peritonitis carcinomatosa consisting of OVCAR-3 cells with the strongest ERα expression or DISS cells with weaker ERα expression was prepared. The survival period was compared between the letrozole group (5 mg/kg/day orally; n = 10) and the control group (n = 10). In addition, the degree of angiogenesis and occurrence of apoptosis were compared using tumor tissue from the abdominal cavity. The expression of aromatase and the protein involving in ERα signaling were examined in tumors immunohistochemically.

Results

Survival period in OVCAR-3 tumors was significantly prolonged in the letrozole group, compared with the control group (P < 0.05), whereas that in DISS tumors was not different between the both groups. The microvessel density in tumors and expression of VEGF decreased significantly in the letrozole group compared to the control group. The incidence of apoptosis did not differ significantly between these groups. No adverse event was observed accompanying the administration of letrozole. The expressions of aromatase, ERα and FOXP1 that is associated with ERα signaling were reduced in tumors by letrozole administration.

Conclusions

Letrozole was effective for ovarian cancers with abundant expression of ERα. Inhibition of angiogenesis and of ascites production appeared to contribute to prolongation of the survival period.

Exposure to excess estradiol or leptin during pregnancy increases mammary cancer risk and prevents parity-induced protective genomic changes in rats

Using a preclinical model, we investigated whether excess estradiol (E2) or leptin during pregnancy affects maternal mammary tumorigenesis in rats initiated by administering carcinogen 7,12-dimethylbenz(a)anthracene (DMBA) on day 50. Two weeks later, rats were mated, and pregnant dams were treated daily with 10 μg of 17β-estradiol, 15 μg of leptin, or vehicle from gestation day 8 to 19. Tumor development was assessed separately during weeks 1 to 12 and 13 to 22 after DMBA administration, because pregnancy is known to induce a transient increase in breast cancer risk, followed by a persistent reduction. Parous rats developed less (32%) mammary tumors than nulliparous rats (59%, P < 0.001), and the majority (93%) of tumors in the parous rats appeared before week 13 (vs. 41% in nulliparous rats), indicating that pregnancy induced a transient increase in breast cancer risk. Parous rats exposed to leptin (final tumor incidence 65%) or E2 (45%) during pregnancy developed mammary tumors throughout the tumor-monitoring period, similar to nulliparous control rats, and the incidence was significantly higher in both the leptin- and E2-exposed dams after week 12 than in the vehicle-exposed parous dams (P < 0.001). The mammary glands of the exposed parous rats contained significantly more proliferating cells (P < 0.001). In addition, the E2- or leptin-treated parous rats did not exhibit the protective genomic signature induced by pregnancy and seen in the parous control rats. Specifically, these rats exhibited downregulation of genes involved in differentiation and immune functions and upregulation of genes involved in angiogenesis, growth, and epithelial-to-mesenchymal transition.

Immunohistochemical vascular factor expression in canine inflammatory mammary carcinoma

Human inflammatory breast carcinoma (IBC) and canine inflammatory mammary carcinoma (IMC) are considered the most malignant types of breast cancer. IMC has similar characteristics to IBC; hence, IMC has been suggested as a model to study the human disease. To compare the angiogenic and angioinvasive features of IMC with non-IMC, 3 canine mammary tumor xenograft models in female SCID mice were developed: IMC, comedocarcinoma, and osteosarcoma. Histopathological and immunohistochemical characterization of both primary canine tumors and xenografts using cellular markers pancytokeratin, cytokeratin 14, vimentin, and α-smooth muscle actin and vascular factors (VEGF-A, VEGF-D, VEGFR-3, and COX-2) was performed. Tumor cell proliferation index was measured by the Ki-67 marker. The xenograft models reproduced histological features found in the primary canine tumor and preserved the original immunophenotype. IMC xenografts showed a high invasive character with tumor emboli in the dermis, edema, and occasional observations of ulceration. In addition, compared with osteosarcoma and comedocarcinoma, the IMC model showed the highest vascular factor expression associated with a high proliferation index. Likewise, IMC xenografts showed higher COX-2 expression associated with VEGF-D and VEGFR-3, as well as a higher presence of dermal lymphatic tumor emboli, suggesting COX-2 participation in IMC lymphangiogenesis. These results provide additional evidence to consider vascular factors, their receptors, and COX-2 as therapeutic targets for IBC.

Estrogen inhibits colon polyp formation by reducing angiogenesis in a carcinogen-induced rat model

Objective. To study the effects of estrogen on colon polyp formation, proliferation, and angiogenesis on a rat model of colon cancer induced by dimethylhydrazine (DMH). Methods. Thirty-six female ovariectomized (OVX) rats were randomly divided into 3 groups: (I) control group (administrated with vehicles weekly), (II) DMH group (administrated with DMH weekly), and (III) DMH + E2 group (administrated with DMH and 17β-estradiol weekly). The incidence, volumes, and multiplicity of colon polyps in each group were evaluated. The microvessel density (MVD), the expressions of Proliferating Cell Nuclear Antigen (PCNA), and the expressions of HIF-1 α and VEGF in polyps were detected in each group. Results. Estrogen reduced the multiplicity, volumes, and the PCNA expressions of DMH-induced colon polyps. The MVD in DMH + E2 group was significantly lower than that in DMH group. Estrogen treatment decreased the HIF-1 α and VEGF expressions at both mRNA and protein level. Conclusion. Estrogen replacement was protective for ovariectomized rats from DMH-induced carcinogenesis, and one of the mechanisms for this was due to estrogen's inhibitive effects on blood vessel formation by downregulating VEGF and HIF-1 α expressions.

The organochlorine o,p'-DDT plays a role in coactivator-mediated MAPK crosstalk in MCF-7 breast cancer cells

BACKGROUND

The organochlorine dichlorodiphenyltrichloroethane (DDT), a known estrogen mimic and endocrine disruptor, has been linked to animal and human disorders. However, the detailed mechanism(s) by which DDT affects cellular physiology remains incompletely defined.

OBJECTIVES

We and others have shown that DDT activates cell-signaling cascades, culminating in the activation of estrogen receptor-dependent and -independent gene expression. Here, we identify a mechanism by which DDT alters cellular signaling and gene expression, independent of the estrogen receptor.

METHODS

We performed quantitative polymerase chain reaction array analysis of gene expression in MCF-7 breast cancer cells using either estradiol (E₂) or o,p´-DDT to identify distinct cellular gene expression responses. To elucidate the mechanisms by which DDT regulates cell signaling, we used molecular and pharmacological techniques.

RESULTS

E₂ and DDT treatment both altered the expression of many of the genes assayed, but up-regulation of vascular endothelial growth factor A (VEGFA) was observed only after DDT treatment, and this increase was not affected by the pure estrogen receptor α antagonist ICI 182780. Furthermore, DDT increased activation of the HIF-1 response element (HRE), a known enhancer of the VEGFA gene. This DDT-mediated increase in HRE activity was augmented by the coactivator CBP (CREB-binding protein) and was dependent on the p38 pathway.

CONCLUSIONS

DDT up-regulated the expression of several genes in MCF-7 breast cancer cells that were not altered by treatment with E₂, including VEGFA. We propose that this DDT-initiated, ER-independent stimulation of gene expression is due to DDT's ability to initiate crosstalk between MAPK (mitogen-activated protein kinase) signaling pathways and transcriptional coactivators.

Minireview: Putting physiology back into estrogens' mechanism of action

After decades of research, the mechanism by which estrogens stimulate the proliferation of epithelial cells in the endometrium and mammary gland, and in the carcinomas that arise in those tissues, is still not understood. Cells do not proliferate in response to 17β-estradiol (E2) alone, and although it is widely recognized that growth factors play a role in E2's proliferative effect, exactly how they are involved is unclear. It has long been known that the proliferation of endometrial epithelial cells is preceded by dramatic increases in blood flow and microvascular permeability, filling the subepithelial stroma with plasma and the proteins it contains, such as IGF-I, which is known to synergize with E2 in the induction of cell proliferation. The hyperpermeability is caused by vascular endothelial growth factor (VEGF), which is rapidly induced by E2, via the transcription factors hypoxia-inducible factor 1 and estrogen receptor α, in luminal epithelial cells in vivo. As we recently showed, VEGF is also strongly induced in endometrial cancer cells in vitro when excessive degradation of hypoxia-inducible factor 1α, caused by the abnormally high oxygen level to which cultured cells are exposed, is prevented. Putting these facts together, we now propose a new model of E2-induced proliferation in which VEGF-induced vascular hyperpermeability plays an essential role. E2 first induces the expression by endometrial epithelial cells of VEGF, which then acts in a paracrine manner to induce interendothelial cell gaps in subepithelial blood vessels, through which plasma and the proteins therein enter the adjacent stroma. Plasma carries even more E2, which circulates bound to proteins, and IGF-l, which together drive epithelial cells completely through the cell cycle.

Bevacizumab in metastatic breast cancer: when may it be used?

Tumor angiogenesis, which is necessary for breast cancer growth, invasion and metastases, is regulated by pro-angiogenic factors such as vascular endothelial growth factor (VEGF). Bevacizumab is a recombinant humanized monoclonal antibody that targets VEGF. The addition of bevacizumab to chemotherapy has improved progression-free survival in the first- and second-line treatment of patients with advanced-stage breast cancer. In this article we review the clinical trials testing the utility of bevacizumab for the treatment of metastatic disease.

Bevacizumab for advanced breast cancer

Tumor angiogenesis is an important step in breast cancer development, progression, invasion and metastasis. Pro-angiogenic factors such as VEGF regulate angiogenesis and are targets for drug development. Bevacizumab, an anti-VEGF antibody, has demonstrated significant clinical benefit in several solid tumors, including breast cancer. Its use in combination with either paclitaxel or docetaxel has prolonged progression-free survival and increased response rates in the first-line treatment of patients with metastatic breast cancer. This review article discusses the clinical trials establishing the use of bevacizumab for the treatment of advanced breast cancer.

RSK in tumorigenesis: connections to steroid signaling

The Ser/Thr kinase family, RSK, has been implicated in numerous types of hormone-dependent and -independent cancers. However, there has been little consideration of RSKs as downstream mediators of steroid hormone non-genomic effects or of their ability to facilitate steroid receptor-mediated gene expression. Steroid hormone signaling can directly stimulate the MEK/ERK/RSK pathway to regulate cellular proliferation and survival in transformed cells. To date, multiple mechanisms of RSK and steroid hormone receptor-mediated proliferation/survival have been elucidated. For example, RSK enhances proliferation of breast and prostate cancer cells via its ability to control the levels of the estrogen receptor co-activator, cyclin D1. While in lung and other tumors RSK may control apoptosis via estrogen-mediated regulation of mitochondrial integrity. Thus the RSKs could be important anti-cancer therapeutic targets in many different transformed tissues. The recent discovery of RSK-specific inhibitors will advance our current understanding of RSK in transformation and drive these studies into animal and clinical models. In this review we explore the mechanisms associated with RSK in tumorigenesis and their relationship to steroid hormone signaling.

Feasibility trial of letrozole in combination with bevacizumab in patients with metastatic breast cancer

PURPOSE

Preclinical models suggest that the use of anti-vascular endothelial growth factor (anti-VEGF) therapy with antiestrogens may prevent or delay the development of endocrine therapy resistance. We therefore performed a feasibility study to evaluate the safety of letrozole plus bevacizumab in patients with hormone receptor-positive metastatic breast cancer (MBC).

METHODS

Patients with locally advanced breast cancer or MBC were treated with the aromatase inhibitor (AI) letrozole (2.5 mg orally daily) and the anti-VEGF antibody bevacizumab (15 mg/kg intravenously every 3 weeks). The primary end point was safety, defined by grade 4 toxicity using the National Cancer Institute Common Toxicity Criteria, version 3.0. Secondary end points included response rate, clinical benefit rate, and progression-free survival (PFS). Prior nonsteroidal AIs (NSAIs) were permitted in the absence of progressive disease.

RESULTS

Forty-three patients were treated. After a median of 13 cycles (range, 1 to 71 cycles), select treatment-related toxicities included hypertension (58%; grades 2 and 3 in 19% and 26%), proteinuria (67%; grades 2 and 3 in 14% and 19%), headache (51%; grades 2 and 3 in 16% and 7%), fatigue (74%; grades 2 and 3 in 19% and 2%), and joint pain (63%; grades 2 and 3 in 19% and 0%). Eighty-four percent of patients had at least stable disease on an NSAI, confounding efficacy results. Partial responses were seen in 9% of patients and stable disease >or= 24 weeks was noted in 67%. Median PFS was 17.1 months.

CONCLUSION

Combination letrozole and bevacizumab was feasible with expected bevacizumab-related events of hypertension, headache, and proteinuria. Phase III proof-of-efficacy trials of endocrine therapy plus bevacizumab are in progress (Cancer and Leukemia Group B 40503).

Inhibition of oxygen-induced hypoxia-inducible factor-1alpha degradation unmasks estradiol induction of vascular endothelial growth factor expression in ECC-1 cancer cells in vitro

Estradiol (E(2)) rapidly and strongly induces vascular endothelial growth factor (VEGF) transcription in uterine endometrial epithelial cells in vivo. We have shown that this is mediated by both the estrogen receptor-alpha and hypoxia-inducible factor (HIF)-1alpha. By contrast, E(2) induces little or no VEGF expression in cultured breast or endometrial cancer cells, which lack HIF-1alpha due to the abnormally high concentration of oxygen ( approximately 20%) to which they are exposed. To test the hypothesis that restoring HIF-1alpha in cultured cells would restore the ability of E(2) to induce VEGF expression, we treated human endometrial cancer cells (ECC-1) with cobalt chloride (CoCl(2);100 microm), which prevents oxygen-induced HIF-1alpha degradation. HIF-1alpha was absent in untreated ECC-1 cells but detectable by 4 h after treatment with CoCl(2) alone, as was a significant increase in VEGF mRNA. E(2) plus CoCl(2) induced detectable HIF-1alpha expression at 2 h and an even higher level than that induced by CoCl(2) alone at 4 h; this HIF-1alpha was localized in the nuclei. This was accompanied by increasing VEGF expression, with the increase at 4 h severalfold higher than that induced by CoCl(2) alone and was concurrent with recruitment of both HIF-1alpha and estrogen receptor-alpha to the VEGF promoter. These results confirm that HIF-1alpha plays an essential role in E(2)-induced expression of VEGF. Through the induction of increased microvascular permeability and the consequent exudation of plasma growth factors, VEGF in turn may play an essential role in cancer cell proliferation in vivo.

Estrogen regulation of thrombospondin-1 in human breast cancer cells

Expression of thrombospondin-1 (TSP-1), a large extracellular matrix protein, has been associated with modulation of angiogenesis and tumor growth. Both pro and antiangiogenic properties of TSP-1 have been described, and the role of TSP-1 expression in the growth and progression of human breast cancer is not clear. Because estrogens cause progression of many breast cancers, and estradiol (E2) downregulates a TSP-1 receptor, we examined whether TSP-1 is regulated by estrogen and involved in tumor progression. E2 induced TSP-1 expression in T47-D and MCF-7 breast cancer cells in vitro within 3 to 6 hr; the induction was blocked by the anti-estrogen ICI 182,780, indicating that estrogen receptors (ER) are necessary for this effect. Furthermore, E2 caused the production of TSP-1 protein from tumor cells in an ER-alpha-dependent manner. The E2-mediated TSP-1 RNA induction was dose-dependent and blocked by actinomycin D, indicating that the response to E2 was at least partly transcriptional. Transfection studies with deletion constructs of the TSP-1 promoter identified an estrogen-responsive region in the human TSP-1 promoter, located between -2,200 and -1,792 bp upstream of the transcription start site. An antibody against TSP-1 restricted the proliferation of E2-dependent MCF-7 cells in vitro and in vivo. A panel of breast cancer cells proliferated in the presence of low concentrations of exogenous TSP-1, whereas higher concentrations inhibited proliferation. A real-time PCR analysis showed that E2 also induced TSP-1 mRNA in the normal mammary glands of immature ovariectomized mice in an ER-dependent manner. In summary, we report the novel observation that TSP-1 production is directly controlled by estrogens in ER-positive breast cancer cells, and the released protein has pro-growth regulatory functions. Consequently, we propose that TSP-1 could be a therapeutic target for anti-tumor therapy in early-stage tumors. (c) 2009 UICC.

Antineoplastic effect of iodine in mammary cancer: participation of 6-iodolactone (6-IL) and peroxisome proliferator-activated receptors (PPAR)

Introduction

Studies in mammary cancer demonstrated that moderately high concentrations of molecular iodine (I₂) have a antiproliferative and apoptotic effect either in vivo as in vitro, however the cellular intermediated involved in these effects has not been elucidated.

Methods

Virgin Sprague-Dawley rats were treated with methyl-nitrosourea (MNU: single dose ip, 50 mg/Kg bw) and the participation of arachidonic acid (AA) and PPAR receptors in the antineoplasic effect of I₂ where analyzed.

Results

I₂-treated rats for four weeks exhibited a significant reduction in the incidence (62.5 vs. 100%) and size (0.87 ± 0.98 vs 1.96 ± 1.5 cm³) of mammary tumors. HPLC analysis showed that tumoral but not normal mammary tissue contained an elevated basal concentration of AA and significantly more AA-iodinated called 6-iodolactone (6-IL) after chronic I₂ treatment. Tumors from I₂-treated rats showed fewer cells positive to proliferating cell nuclear antigen, lower blood vessel density, as well as decreases in vascular endothelial growth factor, urokinase-type plasminogen activator, and PPAR type alpha (PPARα). These same tumors showed increases in the cell death markers, TUNEL-positive cells (p < 0.05) and the enzyme caspase-3 (trend), as well as significant induction of PPAR type gamma (PPARγ).

Conclusion

Together, these data demonstrate that the antineoplasic effect of iodine involves 6-IL formation and PPARγ induction.

Advances in adjuvant endocrine therapy for postmenopausal women

Hormone receptor-positive cancers are the most common tumor subtype among postmenopausal women with breast cancer. Despite substantial improvements in disease-free survival and overall survival with tamoxifen and chemotherapy, recurrences still occur, and may ultimately lead to death from breast cancer. Importantly, disease recurrence includes both early and late events, with over half of all recurrences detected more than 5 years from initial breast cancer diagnosis. In recent years, a number of large, randomized trials have evaluated the role of the aromatase inhibitors (AIs) in postmenopausal women with hormone receptor-positive breast cancer. These studies have tested one of three approaches: (1) an upfront AI, (2) a sequential approach after 2-3 years of tamoxifen, and (3) extended endocrine therapy beyond 5 years. Results of these studies have challenged the previous standard of a 5-year course of tamoxifen alone. While the AIs have become a standard component of treatment for most postmenopausal women, many questions remain as to how best tailor endocrine treatment to individual patients. In addition, despite the gains achieved with the AIs, many recurrences are not prevented, and novel strategies are urgently needed, particularly for those women at high risk of recurrence. In this article, we review the efficacy and toxicity data from the available trials of endocrine therapy in the postmenopausal setting. We outline controversies in choosing the optimal endocrine approach, and we discuss selected ongoing studies. Finally, we highlight future research directions, such as the need to understand host and tumor heterogeneity.

Aromatase expression in women's cancers

Estrogen has been positively linked to the pathogenesis and growth of three common women's cancers (breast, endometrium and ovary). A single gene encodes the key enzyme for estrogen biosynthesis named aromatase, inhibition of which effectively eliminates estrogen production in the entire body. Aromatase inhibitors successfully treat breast cancer, whereas their roles in endometrial and ovarian cancers are less dear. Ovary, testis, adipose tissue, skin, hypothalamus and placenta express aromatase normally, whereas breast, endometrial and ovarian cancers overexpress aromatase and produce local estrogen exerting paracrine and intracrine effects. Tissue specific promoters distributed over a 93 kilobase regulatory region upstream of a common coding region alternatively control aromatase expression. A distinct set of transcription factors regulates each promoter in a signaling pathway- and tissue-specific manner. In cancers ofbreast, endometrium and ovary, aromatase expression is primarly regulated by increased activity of the proximally located promoter 1.3/II region. Promoters I.3 and II lie 215 bp from each other and are coordinately stimulated by PGE2 via a cAMP-PKA-dependent pathway. In breast adipose fibroblasts exposed to PGE2 secreted by malignant epithelial cells, activation of PKC potentiates cAMP-PKA-dependent induction ofaromatase. Thus, inflammatory substances such as PGE2 may play important roles in inducing local production of estrogen that promotes tumor growth.

Mechanisms of disease: angiogenesis and the management of breast cancer

Demonstration of the clinically significant activity of bevacizumab in breast cancer has attracted a great deal of interest. Numerous other antiangiogenic treatments are in clinical development and some established therapies including tamoxifen and trastuzumab might function, in part, by suppressing angiogenesis. In this Review, we discuss the potential of various components of the angiogenic pathway as prognostic and predictive factors in breast cancer. In addition, we describe existing clinical trials of antiangiogenic agents and the challenges facing the clinical development and optimum use of these agents for the treatment of breast cancer.

Aromatase excess in cancers of breast, endometrium and ovary

Pathogenesis and growth of three common women's cancers (breast, endometrium and ovary) are linked to estrogen. A single gene encodes the key enzyme for estrogen biosynthesis named aromatase, inhibition of which effectively eliminates estrogen production in the entire body. Aromatase inhibitors successfully treat breast cancer, whereas their roles in endometrial and ovarian cancers are less clear. Ovary, testis, adipose tissue, skin, hypothalamus and placenta express aromatase normally, whereas breast, endometrial and ovarian cancers overexpress aromatase and produce local estrogen exerting paracrine and intracrine effects. Tissue-specific promoters distributed over a 93-kb regulatory region upstream of a common coding region alternatively control aromatase expression. A distinct set of transcription factors regulates each promoter in a signaling pathway- and tissue-specific manner. In cancers of breast, endometrium and ovary, aromatase expression is primarly regulated by increased activity of the proximally located promoter I.3/II region. Promoters I.3 and II lie 215 bp from each other and are coordinately stimulated by PGE(2) via a cAMP-PKA-dependent pathway. In breast adipose fibroblasts exposed to PGE(2) secreted by malignant epithelial cells, PKC is also activated, and this potentiates cAMP-PKA-dependent induction of aromatase. Thus, inflammatory substances such as PGE(2) may play important roles in inducing local production of estrogen that promotes tumor growth.

Estrogen Receptors α and β Mediate Contribution of Bone Marrow–Derived Endothelial Progenitor Cells to Functional Recovery After Myocardial Infarction

Background— Estradiol (E 2 ) modulates the kinetics of circulating endothelial progenitor cells (EPCs) and favorably affects neovascularization after ischemic injury. However, the roles of estrogen receptors α (ERα) and β (ERβ) in EPC biology are largely unknown.

Methods and Results— In response to E 2 , migration, tube formation, adhesion, and estrogen-responsive element–dependent gene transcription activities were severely impaired in EPCs obtained from ERα-knockout mice (ERαKO) and moderately impaired in ERβKO EPCs. The number of ERαΚΟ EPCs (42.4±1.5; P <0.001) and ERβKO EPCs (55.4±1.8; P =0.03) incorporated into the ischemic border zone was reduced as compared with wild-type (WT) EPCs (72.5±1.3). In bone marrow transplantation (BMT) models, the number of mobilized endogenous EPCs in E 2 -treated mice was significantly reduced in ERαKO BMT (WT mice transplanted with ERαKO bone marrow) (2.03±0.18%; P =0.004 versus WT BMT) and ERβKO BMT (2.62±0.07%; P =0.02 versus WT) compared with WT BMT (2.87±0.13%) (WT to WT BMT as control) mice. Capillary density at the border zone of ischemic myocardium also was significantly reduced in ERαKO BMT and ERβKO BMT compared with WT mice (WT BMT, 1718±75/mm 2 ; ERαKO BMT, 1107±48/mm 2 ; ERβKO BMT, 1567±50/mm 2 ). ERα mRNA was expressed more abundantly on EPCs compared with ERβ. Moreover, vascular endothelial growth factor was significantly downregulated on ERαKO EPCs compared with WT EPCs both in vitro and in vivo.

Conclusions— Both ERα and ERβ contribute to E 2 -mediated EPC activation and tissue incorporation and to preservation of cardiac function after myocardial infarction. ERα plays a more prominent role in this process. Moreover, ERα contributes to upregulation of vascular endothelial growth factor, revealing possible mechanisms of an effect of E 2 on EPC biology. Finally, these data provide additional evidence of the importance of bone marrow–derived EPC phenotype in ischemic tissue repair.

Randomized Phase II Trial of Letrozole and Letrozole Plus Low-Dose Metronomic Oral Cyclophosphamide As Primary Systemic Treatment in Elderly Breast Cancer Patients

Purpose

To investigate the activity of letrozole plus/minus oral metronomic cyclophophamide as primary systemic treatment (PST) in elderly breast cancer patients.

Methods

One hundred fourteen consecutive elderly women with T2-4 N0-1 and estrogen receptor–positive breast cancer were randomly assigned to primary letrozole therapy (2.5 mg daily for 6 months) or a combination of letrozole plus oral cyclophosphamide (50 mg/daily for 6 months) in an open-labeled, randomized phase II trial. Tumor response was assessed clinically, and tumor Ki67 index and vascular endothelial growth factor (VEGF) -A levels were measured before and after treatment.

Results

Overall response rate was 71.9% (95% CI, 60.0 to 83.8) in the 57 patients randomly assigned to receive primary letrozole and 87.7% (95% CI, 78.6 to 96.2) in the 57 patients randomly assigned to receive letrozole plus cyclophosphamide. The difference in activity between treatment arms was predominantly confined to patients with ductal histology. There was a significantly greater suppression of Ki67 and VEGF-A expression in the letrozole/cyclophosphamide-treated group than in the letrozole-treated group, leading to lower Ki67 and VEGF expression at post-treatment residual histology (P = .03 and P = .002, respectively).

Conclusion

Both letrozole and letrozole plus cyclophosphamide treatments appeared active as PST in elderly breast cancer patients. Metronomic scheduling of cyclophosphamide may have an antiangiogenetic effect and the combination of letrozole plus cyclophosphamide warrants testing in a randomized phase III trial.

Partial irradiation of the breast: Old challenges, new solutions

Breast-conserving treatment, characteristically consisting of surgical removal of the tumor and post-operative whole breast irradiation, is nowadays considered as the standard therapeutic approach for most women with stage I/II, invasive breast cancer. Recently, a number of institutions started investigating the feasibility and safety of novel approaches in radiotherapy, modulating concomitantly treatment time and irradiation volume. Whilst this strategy is still under investigation, recent clinical studies on accelerated partial breast irradiation with intra-operative radiotherapy or high conformality irradiation strongly suggest that the way patients with early breast cancer are irradiated should be revisited.

Vascular endothelial growth factor receptor-2 expression is induced by 17beta-estradiol in ZR-75 breast cancer cells by estrogen receptor alpha/Sp proteins

Vascular endothelial growth factor receptor-2 kinase insert domain receptor (VEGFR2/KDR) is critical for angiogenesis, and VEGFR2 mRNA and protein are expressed in ZR-75 breast cancer cells and induced by 17beta-estradiol (E2). Deletion analysis of the VEGFR2 promoter indicates that the proximal GC-rich region is required for both basal and hormone-induced transactivation, and mutation of one or both of the GC-rich motifs at -58 and -44 results in loss of transactivation. Electrophoretic mobility shift and chromatin immunoprecipitation assays show that Sp1, Sp3, and Sp4 proteins bind the GC-rich region of the VEGFR2 promoter. Results of the chromatin immunoprecipitation assay also demonstrate that ERalpha is constitutively bound to the VEGFR2 promoter and that these interactions are not enhanced after treatment with E2, whereas ERalpha binding to the region of the pS2 promoter containing an estrogen-responsive element is enhanced by E2. RNA interference studies show that hormone-induced activation of the VEGFR2 promoter constructs requires Sp3 and Sp4 but not Sp1, demonstrating that hormonal activation of VEGFR2 involves a nonclassical mechanism in which ERalpha/Sp3 and ERalpha/Sp4 complexes activate GC-rich sites where Sp proteins but not ERalpha bind DNA. These results show for the first time that Sp3 and Sp4 cooperatively interact with ERalpha to activate VEGFR2 and are in contrast to previous results showing that several hormone-responsive genes are activated by ERalpha/Sp1 in breast cancer cell lines.

Clinical relevance of amphiregulin and VEGF in primary breast cancers

The characterization of novel prognostic markers in breast cancer is necessary to improve the identification of high-risk populations. In our study, the prognostic significance of VEGF and amphiregulin (AR) was investigated and compared to conventional prognostic factors in primary breast cancers. The analysis was performed using enzyme-linked immuno-assay in a series of 193 patients, and univariate and multivariate analysis were performed in the overall population as well as in pre- and post-menopausal patients subdivided in node-negative (N-) and node-positive (N+) subsets. AR (median, 44.8 pg/mg protein) appeared strongly correlated with progesterone receptors (PgR) (p = 0.0018) in the premenopausal N+ population, and with uPA (p= 0.020) and VEGF (p= 0.0053) in the postmenopausal/N+ patients. Despite these attractive data, AR expression was not significant for recurrence or survival outcome. Data revealed strong correlation between VEGF and uPA, and PAI-1, in the N+ population. Moreover, patients with high VEGF levels displayed poor outcome, with an increased risk for N+ subset. These data were confirmed by multivariate analysis that presented histologic grade (HR, 10.55, p = 0.001) and VEGF (HR, 3.89, p = 0.03) as the prominent prognostic markers for overall survival for the N+ population. Furthermore, infiltrating ductal carcinomas (IDC) were shown to express higher levels of both uPA (p < 0.0001) and VEGF (p = 0.002) than intralobular carcinomas. This retrospective study reinforces the pejorative biological role of VEGF in the progression of breast tumors. Our data also suggest that VEGF and uPA might play particular role in the biology and progression of IDC.

Bevacizumab in the Treatment of Breast Cancer: Rationale and Current Data

Vascular endothelial growth factor (VEGF) has emerged as a key target for the treatment of cancer. As the ligand to the VEGF receptor, it plays a central role in promoting tumor angiogenesis. Overexpression of VEGF leads to poor outcomes in patients with breast cancer and other tumors. Preclinical studies have shown that the humanized monoclonal antibody to VEGF, bevacizumab (Avastin; Genentech, Inc., South San Francisco, CA), can reduce tumor angiogenesis and inhibit the growth of solid tumors, either alone or in combination with chemotherapy. As a single agent or added to vinorelbine, bevacizumab has produced encouraging results in phase II clinical trials in patients with refractory metastatic breast cancer. When added to capecitabine chemotherapy in a phase III trial, bevacizumab produced a greater response rate, but did not prolong progression-free survival. This may reflect the late disease stage and poor prognostic factors in the patient population. A large, ongoing, phase III, cooperative group trial is evaluating the effect of bevacizumab in combination with paclitaxel as first-line therapy for metastatic disease. The adverse effect profile of bevacizumab differs from that of cytotoxic chemotherapy and includes hypertension, proteinuria, thrombosis, and epistaxis.

Progestin-dependent induction of vascular endothelial growth factor in human breast cancer cells: preferential regulation by progesterone receptor B

The progesterone receptor (PR) is a ligand-dependent transcription factor that promotes progestin-stimulated expression of target genes. Two functional PR isoforms, PRA and PRB, are expressed in progestin-responsive cells. PRA and PRB have distinct roles in gene expression and in mammary gland development. One role of PRs in T47-D cells is regulating expression of vascular endothelial growth factor (VEGF), a potent angiogenic growth factor. This study explores the isoform specificity of this PR function using parental T47-Dco cells that express both PRA and PRB and clonal derivatives that express either PRA (YA cells) or PRB (YB cells) or lack PR (Y cells). Treatment with progesterone induces VEGF mRNA and protein approximately 2-fold in T47-Dco and YA cells and 3-7-fold in YB cells, suggesting that PRA inhibits PRB-dependent induction of VEGF. This is consistent with the observation that clinically relevant progestins induce a much higher level of VEGF in YB cells than in YA cells. Another novel finding in this report is that estradiol (10(-8) M) induces VEGF production from YB cells. However, this induction is not blocked by 100-fold excess tamoxifen or ICI-182,780. Moreover, both tamoxifen (10(-6) M) and ICI-182,780 (10(-6) M) function as agonists for VEGF in YB cells. Small interfering RNA against PR or estrogen receptor abrogated estradiol and tamoxifen induction, indicating that the agonist-like response of these compounds in YB cells is estrogen receptor and PR dependent. Estradiol, tamoxifen, and ICI-182780 also induce VEGF in BT-474 cells when their PRB levels were elevated by transfecting an expression plasmid for PRB, but not when the cells were transfected with vector alone. These results indicate that (a) PRB preferentially regulates VEGF expression in breast cancer cells and (b) PRB-enriched tumor cells may produce more VEGF, have a better developed vasculature, and potentially are more resistant to tamoxifen and ICI-182,780 than cells that express an equivalent or higher level of PRA than PRB. These results imply that PRB-enriched breast tumors may respond well to anticancer therapies that include inhibitors of angiogenesis.

Intraoperative radiotherapy for breast cancer

Postoperative radiotherapy, which forms part of breast-conserving therapy, may not need to encompass the whole breast. Apart from the consumption of huge resources and patients' time, postoperative radiotherapy deters many women from receiving the benefits of breast-conserving surgery, forcing them to choose a mastectomy instead. If radiotherapy could be given in the operating theatre immediately after surgery, many of these disadvantages could be overcome. One striking fact about local recurrence after breast-conserving surgery is that most occurs in the area of breast immediately next to the primary tumour; this is despite the finding that two-thirds of mastectomy samples have microscopic tumours distributed throughout the breast, even when radiotherapy is omitted. Thus, only the area adjacent to the tumour may need treatment with radiotherapy. On the basis of this premise, clinical scientists have used new technology to administer radiotherapy to the area at greatest risk of local recurrence, with the aim of completing the whole local treatment in one sitting. In this review, we have elaborated on the rationale and different methods of delivery of intraoperative radiotherapy. If this approach is validated by the results of current randomised trials, it could save time, money, and breasts.

Estrogen regulation of vascular endothelial growth factor gene expression in ZR-75 breast cancer cells through interaction of estrogen receptor alpha and SP proteins

Vascular endothelial growth factor (VEGF) is expressed in multiple hormone-dependent cancer cells/tumors. Treatment of ZR-75 breast cancer cells with 17beta-estradiol (E2) induced a greater than fourfold increase of VEGF mRNA levels. ZR-75 breast cancer cells were transfected with pVEGF1, a construct containing a -2018 to +50 VEGF promoter insert, and E2 induced reporter gene (luciferase) activity. Deletion and mutation analysis of the VEGF gene promoter identified a GC-rich region (-66 to -47) which was required for E2-induced transactivation of pVEGF5, a construct containing the minimal promoter (-66 to +54) that exhibited E2-responsiveness. Interactions of nuclear proteins from ZR-75 cells with the proximal GC-rich region of the VEGF gene promoter were investigated by electrophoretic mobility shift and chromatin immunoprecipitation assays. The results demonstrate that both Sp1 and Sp3 proteins bound the GC-rich motif (-66 to -47), and estrogen receptor alpha (ERalpha) interactions were confirmed by chromatin immunoprecipitation. Moreover, E2-dependent activation of constructs containing proximal and distal GC/GT-rich regions of the VEGF promoter was inhibited in ZR-75 cells transfected with small inhibitory RNAs for Sp1 and Sp3. These results were consistent with a mechanism of hormone activation of VEGF through ERalpha/Sp1 and ERalpha/Sp3 interactions with GC-rich motifs.

Effects of transcutaneous topical injection of oxygen on vascular endothelial growth factor gene into the healing ligament in rats

The effects of intermittent exposure to oxygen injection on an experimentally induced ligament tear were studied in the right hind limb of 17 male Sprague-Dawley rats. Two rats were used for monitoring the partial oxygen pressure (pO(2)) of subcutaneous tissue and 15 rats were divided into the following three groups of 5 after an experimentally induced ligament tear: Group A, control group; Group B, injection of 0.5 ml hyaluronan to the wound transcutaneously; Group C, injection of 0.5 ml hyaluronan mixed with haemoglobin and oxygen (n=5). At 7 days post-ligament injury, we compared the ligaments of the three treatment groups for gross appearance, histology and expression of vascular endothelial growth factor (VEGF) mRNA by RT-PCR. Our results indicate that the pO(2) was immediately elevated to 334.6 mmHg by topical oxygen injection and this method was effective in promoting vessel formation in comparison to the control group (p<0.01). However, the expression of VEGF mRNA in the topical oxygen injection group (Group C) was lower than that in control group (p<0.05). Our results suggest that oxygen is able to accelerate vessel formation in spite of its effect of decreasing VEGF mRNA. Our method of using topical injection proved to be useful in healing the ligament and the wound.

In vitro regulation of vascular endothelial growth factor by estrogens and antiestrogens in estrogen-receptor positive breast cancer

BACKGROUND

The effects of antiestrogens on angiogenesis in breast cancer are not fully defined. In this study we investigated the in vitro effects of antiestrogens at different concentrations on vascular endothelial growth factor (VEGF) production in estrogen receptor (ER)-positive breast cancer cells.

METHODS

The dose-dependent effects of 17beta-estradiol (E2), 4-hydroxytamoxifen (4OHT), and ICI182,780 were analyzed both with reference to growth rates and VEGF protein production using enzyme-linked immunosorbent assay (ELISA) in MCF-7 cells.

RESULTS

E2 stimulated both the growth rates and VEGF production of MCF-7 cells in the same manner. Although 4OHT stimulated the growth rates as an agonistic effect in an estrogen-free media at levels ranging from 1 nM to 1 micro M, it did not stimulate VEGF expression at the same levels except for at 1 micro M. Although 4OHT had a weak agonistic effect on VEGF production at 1 micro M in an estrogen-free media, it significantly inhibited E2-stimulated VEGF production at the same level. A cytotoxic effect was observed with 10 micro M 4OHT that paradoxically caused a prominent increase in VEGF production. ICI182,780 had no significant effects on the growth rates or VEGF production in this cell line.

CONCLUSIONS

These results support the hypothesis that tamoxifen could inhibit angiogenesis induced by estrogens in ER-positive breast cancer cells.

Differential gene expression of vascular endothelial growth factor isoforms and their receptors in the development of the rat masseter muscle

The capillary network in the masseter muscle develops dramatically with the differentiation of muscle fibres after birth, especially around weaning. Here, developmental changes in mRNA expression for four splicing variants of vascular endothelial growth factor (VEGF) and for two distinct VEGF receptors (Fms-like tyrosine kinase (Flt-1) and kinase insert domain-containing receptor/fetal liver kinase-1 (KDR/Flk-1)) were studied in rat masseter. The relative abundance of VEGF (120) mRNA was the highest, representing 35% of total VEGF mRNA on day 7 after birth and gradually decreased with age to become approximately 5% on day 37. In contrast, VEGF (188) mRNA was very low in the newborn rat, but increased sharply before weaning and reached 40-50% of the total on day 50. Neither VEGF (144) nor VEGF(164) mRNA showed any significant change in abundance after birth. The expression of KDR/Flk-1 mRNA was transiently high in the early postnatal stage and gradually decreased with age, Flt-1 mRNA was stably expressed at a constant level after birth. These findings suggest that different combinations of VEGF isoforms and their receptors regulate angiogenesis in the development of the masseter muscle.

A comparison of serum and plasma levels of vascular endothelial growth factor during the menstrual cycle in healthy female volunteers

Angiogenesis is the formation of new blood vessels from the existing vasculature, and is essential for the growth and metastasis of most solid tumours. One of the most important growth factors involved in the angiogenesis process is vascular endothelial growth factor. Vascular endothelial growth factor expression has been shown to be regulated by female hormones in breast cancer cell lines, and two previous authors have reported on cyclical variations in serum vascular endothelial growth factor concentrations with conflicting results. No work has been performed on variations in plasma levels of vascular endothelial growth factor during the menstrual cycle. We therefore conducted the first prospective trial to compare serum and plasma levels of vascular endothelial growth factor in healthy pre-menopausal volunteers. Twenty healthy pre-menopausal women were recruited and had blood samples taken over one menstrual cycle with an average of eight samples taken per patient. Plasma and serum samples were then analysed for sex hormones and vascular endothelial growth factor 165. Serum vascular endothelial growth factor levels were found to be significantly higher than plasma vascular endothelial growth factor levels (P<0.005). We found no significant difference between serum and plasma vascular endothelial growth factor in the luteal and follicular phases of the cycle. The majority of the measurements for plasma levels of vascular endothelial growth factor at all phases of the cycle were under the limit of detection of the vascular endothelial growth factor ELISA kit. We found no significant correlation between plasma or serum levels of vascular endothelial growth factor and either FSH, LH, Oestradiol or Progesterone levels. This study has demonstrated no difference in serum concentrations of vascular endothelial growth factor during the different phases of the menstrual cycle in a group of healthy volunteers. We also demonstrated no obvious difference in plasma concentrations of vascular endothelial growth factor between the phases of the cycle, but most of the measurements were below the level of accuracy reported by the ELISA kit manufacturer. With the sensitivity of this ELISA test, therefore, we must still regard the question of whether there is a variation in plasma concentrations of vascular endothelial growth factor throughout the menstrual cycle as unanswered.

Cloning and characterization of a novel gene that is regulated by estrogen and is associated with mammary gland carcinogenesis

Estrogens play a role in mammary gland function and are implicated in mammary carcinogenesis. We report the cloning of a novel gene [steroid-sensitive gene 1 (SSG1)] that is regulated by E(2) in the rat uterus and mammary gland. The full-length SSG1 complementary DNA has an open reading frame of 1158 nucleotides encoding a putative protein of 385 amino acids. A SSG1-specific antibody recognizes a 40-kDa protein localized to myoepithelial cells of normal mammary tissue and to endothelial cells of 7,12-dimethylbenz(a)antracene-induced mammary tumors. Treatment of rats with E(2) at 1.2 or 2.4 microg/kg.day for 21 days increases SSG1 protein levels in mammary tissue by 16-fold compared with controls. Removal of E(2) after a 14-day treatment decreases SSG1 protein levels 6-fold and 3-fold at 120 and 144 h, respectively. Treatment of rats with the estrogen antagonists tamoxifen or ICI 182,780 did not affect SSG1 protein levels compared with controls. SSG1 protein levels in 7,12-dimethylbenz(a)antracene-induced rat mammary tumors were 23-fold greater than SSG1 levels in resting mammary tissue, and 8-fold higher than protein levels expressed in lactating mammary glands. We propose that SSG1 plays a role in estrogen functions, and its overexpression is correlated with mammary carcinogenesis.

Pharmacological and endogenous progestins induce vascular endothelial growth factor expression in human breast cancer cells

Tumor expansion is dependent on angiogenesis, which is regulated by peptide growth factors of which vascular endothelial growth factor (VEGF) is one of the most selective and potent. VEGF expression is regulated by steroid hormones in a number of systems, including T47-D human breast cancer cells in which VEGF protein levels are elevated by progestins. In the present study, we investigated the effect of progestins on VEGF mRNA levels in human breast cancer cells. For these experiments, T47-D cells were exposed to progestins, RNA was prepared for measurement of VEGF transcript levels by Northern blot analysis and VEGF protein in the cell culture media was measured by enzyme-linked immunosorbent assay. Basal expression of VEGF mRNA is low in these cells, and is rapidly induced following exposure to progestins, reaching a maximum induction of 2- to 5-fold between 3 and 6 hr after hormone addition. This induction was inhibited by the antiprogestin RU-486 indicating that it is progesterone receptor (PR) dependent. Transcripts for VEGF165 and VEGF121 were the two major spliced forms of VEGF mRNA that were detected by reverse transcription-polymerase chain reaction in basal and progestin-stimulated T47-D cells. Maximum induction of VEGF mRNA was achieved with 10(-8) M progesterone, and induction was hormone specific, as estrogens, glucocorticoids, and androgens were without effect. Actinomycin D completely abolished the induction of VEGF transcript levels by progestins, suggesting that this response involves de novo mRNA synthesis, but puromycin did not inhibit induction, suggesting that this effect does not require protein synthesis. This report demonstrates that progestins stimulate VEGF mRNA levels and raises the possibility that anti-progestins may be useful to inhibit proliferation and metastasis in some human breast cancers by blocking VEGF production.

Transcriptional regulation of vascular endothelial growth factor expression in epithelial and stromal cells during mouse mammary gland development

Accompanying changes in the development and function of the mammary gland is the establishment of a vascular network of critical importance for lactogenesis and tumorigenesis. A potent angiogenic and permeability factor that regulates vascular development in association with epithelial-stromal interactions is vascular endothelial growth factor (VEGF). Analysis of VEGF transcription by RT-PCR revealed mRNA for all three VEGF isoforms (VEGF120, 164, 188) within the mammary gland of nulliparous females. During pregnancy the level of VEGF188 declined and became undetectable during lactation in association with the increased abundance of VEGF120 and VEGF164 mRNAS: All three isoforms were expressed at consistent levels within the cleared mammary fat pad throughout development. Furthermore, the presence of VEGF188 mRNA in omental adipose tissue at various stages established that VEGF188 is expressed specifically in adipose tissue within the mammary gland. Using 3T3-L1 preadipocytes it was demonstrated that VEGF188 mRNA transcription occurs as a late event during lipogenesis distinct from earlier induction of VEGF120 and VEGF164 mRNA during differentiation. In contrast, HC11 mammary epithelial cells only expressed mRNA for VEGF120 and VEGF164. Localization of VEGF mRNA and protein revealed that VEGF is expressed in stromal cells of the mammary gland in nulliparous females and then undergoes a transition to epithelial expression during lactation. By contrast, mRNA for the VEGF receptors, Flk-1 and Flt-1, localized to stromal cells within the mammary fat pad during virgin and gestational development and was expressed in the interstitial tissue basal to epithelial cells during lactation. Taken together, these results support the conclusion that VEGF is differentially transcribed by specific cell types within the mammary gland, and that under hormonal regulation it functions in an autocrine/paracrine manner.

Low pO2 and beta-estradiol induce VEGF in MCF-7 and MCF-7-5C cells: relationship to in vivo hypoxia

Previous work from this laboratory demonstrated that MCF-7 breast carcinoma cells grown in nude mice contained minimal hypoxia but that tamoxifen treatment of these tumors resulted in increased hypoxia (Evans S. et al., Cancer Research, 1997). These findings led to studies exploring the link between estrogen signaling and tumor oxygenation and determining the role of VEGF in this process. The stimulation of estrogen-dependent MCF-7 breast carcinoma cells in vitro with beta-estradiol resulted in a two-fold induction of VEGF mRNA and 1.3-2-fold increase in protein, similar to what was observed when these cells were exposed to 0. 1% oxygen. Furthermore, the two stimuli given together had an additive effect on (increasing) VEGF expression, suggesting that the combination of hypoxia and estrogen may be important in upregulating VEGF in some breast cancers. Estrogen-independent MCF-7-5C cells, developed by growing MCF-7 cells in long-term culture in estrogen-free media, were also studied. Using EF5, a fluorinated 2-nitroimidazole which localizes to hypoxic cells, MCF-7-5C tumors grown in nude mice were found to contain lower pO2 levels and more hypoxic regions than similarly grown MCF-7 tumors. We tested the hypothesis that this might be the result of defective expression of VEGF in MCF-7-5C cells in response to beta-estradiol and/or hypoxia. However, MCF-7-5C and MCF-7 cells showed a similar induction of VEGF in vitro in response to either beta-estradiol or hypoxia. Therefore, although these two cell lines grown as tumors have substantial differences in the presence and patterns of hypoxia, this could not be explained by a difference in VEGF induction.

Vascular remodelling during the normal and malignant life cycle of the mammary gland

The mammary gland life cycle is exemplified by massive, physiologically dictated changes in cell number and composition, architecture, and functionality. These drastic upheavals, by necessity, also involve the mammary endothelium, which undergoes angiogenic expansion during pregnancy and lactation followed by ordered regression during involution. In this review, we summarise data obtained using the Mercox methyl methacrylate corrosion cast technique to analyse the mammary gland vasculature during normal development and carcinogenesis. Concomitant with epithelial cell expansion, the mammary vasculature grows during the first half of pregnancy by sprouting angiogenesis whereas the last half of pregnancy and lactation are characterised by the non-proliferative intussusceptive angiogenesis. The vasculature of the lactating gland is composed of a well-developed capillary meshwork enveloping the secretory alveoli with basket-like honeycomb structures. During involution, regression of the vasculature is achieved by regional collapse of the honeycomb structures, capillary retraction, and endothelial attenuation. This process appears partly to involve apoptosis. However, an additional mechanism involving remodelling without cell death, which we have termed angiomeiosis, must exist to explain the morphological observations. Interestingly, in mammary tumours of neuT transgenic mice, both sprouting and intussusceptive angiogenesis was observed simultaneously in the same nodules, a finding with potential implications for cancer therapy. The underlying molecular mechanisms controlling angiogenic modulation in the mammary gland, particularly angiogenic regression and the endothelial:parenchymal interplay, are poorly understood. However, the data summarised in this review indicate that precisely these molecular mechanisms offer novel alternatives for specific and effective treatment of breast cancer.

Inhibition of vascular endothelial growth factor expression in HEC1A endometrial cancer cells through interactions of estrogen receptor alpha and Sp3 proteins

Treatment of HEC1A endometrial cancer cells with 10 nm 17beta-estradiol (E2) resulted in decreased vascular endothelial growth factor (VEGF) mRNA expression, and a similar response was observed using a construct, pVEGF1, containing a VEGF gene promoter insert from -2018 to +50. In HEC1A cells transiently transfected with pVEGF1 and a series of deletion plasmids, it was shown that E2-dependent down-regulation was dependent on wild-type estrogen receptor alpha (ERalpha) and reversed by the anti-estrogen ICI 182, 780, and this response was not affected by progestins. Deletion analysis of the VEGF gene promoter identified an overlapping G/GC-rich site between -66 to -47 that was required for decreased transactivation by E2. Protein-DNA binding studies using electrophoretic mobility shift and DNA footprinting assays showed that both Sp1 and Sp3 proteins bound this region of the VEGF promoter. Coimmunoprecipitation and pull-down assays demonstrated that Sp3 and ERalpha proteins physically interact, and the interacting domains of both proteins are different from those previously observed for interactions between Sp1 and ERalpha proteins. Using a dominant negative form of Sp3 and transcriptional activation assays in Schneider SL-2 insect cells, it was confirmed that ERalpha-Sp3 interactions define a pathway for E2-mediated inhibition of gene expression, and this represents a new mechanism for decreased gene expression by E2.

DMBA-induced mammary pathologies are angiogenic in vivo and in vitro

We have previously shown that human pre-invasive diseases of the breast are angiogenic. In addition, normal epithelium from women with coincident or subsequent invasive breast cancer is more vascular than normal epithelium from women with no breast cancer. To develop a model in which to study the regulation of angiogenesis in pre-invasive mammary pathologies, we examined 7,12-dimethylbenz[a]anthracene (DMBA)-induced rat mammary tissues for the presence of neovascularization in pre-invasive histopathologies. These studies included morphometric analysis of tissue vascularity in pre-invasive lesions. In addition, we isolated fresh tumors and histologically normal epithelium (organoids) from DMBA or vehicle-treated control rats to test their ability to induce endothelial cell tubule formation in vitro. Finally, we examined tumors for their ability to produce vascular endothelial cell growth factor. The morphometric studies documented that with epithelial progression, the ability of individual cells to elicit angiogenesis increases. The in vitro studies showed that isolated tumors from these animals stimulate angiogenesis. Furthermore, normal epithelium from DMBA-treated rats is more angiogenic than epithelium from control animals. Finally, DMBA-induced tumors produce vascular endothelial growth factor (VEGF) mRNA, therefore, DMBA-induced mammary tumorigenesis is one model in which to test the dependency of progression on angiogenesis.

Selenium-induced inhibition of angiogenesis in mammary cancer at chemopreventive levels of intake

The trace element nutrient selenium (Se) has been shown to possess cancer-preventive activity in both animal models and humans, but the mechanisms by which this occurs remain to be elucidated. Because angiogenesis is obligatory for the genesis and growth of solid cancers, we investigated, in the study presented here, the hypothesis that Se may exert its cancer-preventive activity, at least in part, by inhibiting cancer-associated angiogenesis. The effects of chemopreventive levels of Se on the intra-tumoral microvessel density and the expression of vascular endothelial growth factor in 1-methyl-1-nitrosourea-induced rat mammary carcinomas and on the proliferation and survival and matrix metalloproteinase activity of human umbilical vein endothelial cells in vitro were examined. Increased Se intake as Se-enriched garlic, sodium selenite, or Se-methylselenocysteine led to a significant reduction of intra-tumoral microvessel density in mammary carcinomas, irrespective of the manner by which Se was provided: continuous exposure (7-wk feeding) with a chemoprevention protocol or acute bolus exposure (3 d) after carcinomas had established. Compared with the untreated controls, significantly lower levels of vascular endothelial growth factor expression were observed in a sizeable proportion of the Se-treated carcinomas. In contrast to the mammary carcinomas, the microvessel density of the uninvolved mammary glands was not altered by Se treatment. In cell culture, direct exposure of human umbilical vein endothelial cells to Se induced cell death predominantly through apoptosis, decreased the gelatinolytic activities of matrix metalloproteinase-2, or both. These results indicate a potential for Se metabolites to inhibit key attributes (proliferation, survival, and matrix degradation) of endothelial cells critical for angiogenic sprouting. Therefore, inhibition of angiogenesis associated with cancer may be a novel mechanism for the anticancer activity of Se in vivo, and multiple mechanisms are probably involved in mediating the anti-angiogenic activity.

Changes in vascularization of human breast cancer xenografts responding to antiestrogen therapy

To elucidate the previously suggested vascular effect(s) of antiestrogen therapy, we studied the effect of estrogen withdrawal and tamoxifen on 1) vascular resistance, 2) glucose and oxygen consumption, and 3) vascular density in a perfused breast cancer line (ZR75-1). Furthermore, we examined ZR75-1 tumors by functional CT-scanning (fCT) to determine changes in parameters related to tumor capillary transfer constants and vascular volume fraction in response to antiestrogenic manipulations. The vascular resistance decreased significantly from 42.7 to 20.8 mmHg x min x g x ml(-1) (P< .03) on day 9 after estrogen withdrawal, but not after 9 days of tamoxifen treatment. The estrogen-depleted tumors were significantly smaller than controls on day 9. There was no difference in nutrient consumption or vascular density in any of the experimental groups compared to controls. fCT showed an increase (P < .03) in vascular volume fraction during tumor growth, and this parameter was significantly lower after estrogen withdrawal when compared to controls (P < .05). Vascular resistance correlated with tumor size (R = 0.7, P < .0001), indicating that vascular resistance increases during tumor growth. The changes in vascular parameters after estrogen withdrawal indicate a vascular remodeling effect. This inhibition of vascular development by hormone deprivation may have important implications for future planning of multimodal treatment regimens.