Stimulation of vascular endothelial growth factor gene transcription by all trans retinoic acid through Sp1 and Sp3 sites in human bronchioloalveolar carcinoma cells

FLORID NEOVASCULARIZATION OF THE RETINA IN A DIABETIC PATIENT UNDERGOING INDUCTION AND CONSOLIDATION THERAPY FOR ACUTE PROMYELOCYTIC LEUKEMIA

PURPOSE

To report on a 39-year-old gentleman with a background of Type 2 diabetes mellitus who was diagnosed with acute promyelocytic leukemia (APL), which was treated by all-trans retinoic acid (ATRA), and subsequently developed bilateral neovascularization of the disk (NVD).

METHODS

Ophthalmic examination and investigation including fundus photography and fluorescein angiography.

RESULTS

Three months after commencement of ATRA therapy, the patient was found to have florid bilateral NVD with adjacent preretinal and intraretinal hemorrhages. Fundus fluorescein angiography was undertaken and NVD was confirmed in both eyes, which was significantly greater than expected for the extent of disease secondary to diabetic retinopathy. As a result of the fluorescein angiography findings, we believe ATRA-mediated upregulation of vascular endothelial growth factor may be the etiology of the NVD. Literature review shows some in vitro studies, which describe ATRA-induced upregulation of vascular endothelial growth factor in ocular tissues. The patient was managed successfully by cessation of ATRA and a single intravitreal injection of bevacizumab in each eye.

CONCLUSION

Acute promyelocytic leukemia treated with ATRA may result in upregulation of vascular endothelial growth factor in retinal tissues. Subsequent development of NVD may occur; however, this resolves well by cessation of ATRA and intravitreal injection of bevacizumab. We recommend that all patients undergoing treatment with ATRA for acute promyelocytic leukemia be monitored by an ophthalmologist.

Stemness marker ALDH1A1 promotes tumor angiogenesis via retinoic acid/HIF-1α/VEGF signalling in MCF-7 breast cancer cells

Background

Aldehyde dehydrogenase 1A1 (ALDH1A1), a member of aldehyde dehydrogenase family, is a marker of stemness in breast cancer. During tumor progression cancer stem cells (CSCs) have been reported to secrete angiogenic factors to orchestrate the formation of pathological angiogenesis. This vasculature can represent the source of self-renewal of CSCs and the route for further tumor spreading. The aim of the present study has been to assess whether ALDH1A1 controls the output of angiogenic factors in breast cancer cells and regulates tumor angiogenesis in a panel of in vitro and in vivo models.

Methods

Stemness status of breast cancer cells was evaluated by the ability to form turmorspheres in vitro. A transwell system was used to assess the angiogenic features of human umbilical vein endothelial cells (HUVEC) when co-cultured with breast cancer cells MCF-7 harboring different levels of ALDH1A1. Under these conditions, we survey endothelial proliferation, migration, tube formation and permeability. Moreover, in vivo, MCF-7 xenografts in immunodeficient mice allow to evaluate blood flow, expression of angiogenic factors and microvascular density (MVD).

Results

In MCF-7 we observed that ALDH1A1 activity conferred stemness property and its expression correlated with an activation of angiogenic factors. In particular we observed a significant upregulation of hypoxia inducible factor-1α (HIF-1α) and proangiogenic factors, such as vascular endothelial growth factor (VEGF). High levels of ALDH1A1, through the retinoic acid pathway, were significantly associated with VEGF-mediated angiogenesis in vitro. Co-culture of HUVEC with ALDH1A1 expressing tumor cells promoted endothelial proliferation, migration, tube formation and permeability. Conversely, downregulation of ALDH1A1 in MCF-7 resulted in reduction of proangiogenic factor release/expression and impaired HUVEC angiogenic functions. In vivo, when subcutaneously implanted in immunodeficient mice, ALDH1A1 overexpressing breast tumor cells displayed a higher expression of VEGF and MVD.

Conclusion

In breast tumors, ALDH1A1 expression primes a permissive microenvironment by promoting tumor angiogenesis via retinoic acid dependent mechanism. In conclusion, ALDH1A1 might be associated to progression and diffusion of breast cancer.

Electronic supplementary material

The online version of this article (10.1186/s13046-018-0975-0) contains supplementary material, which is available to authorized users.

Bones in human CYP26B1 deficiency and rats with hypervitaminosis A phenocopy Vegfa overexpression

Angulated femurs are present prenatally both in CYP26B1 deficient humans with a reduced capacity to degrade retinoic acid (RA, the active metabolite of vitamin A), and mice overexpressing vascular endothelial growth factor a (Vegfa). Since excessive ingestion of vitamin A is known to induce spontaneous fractures and as the Vegfa-induced femur angulation in mice appears to be caused by intrauterine fractures, we analyzed bones from a CYP26B1 deficient human and rats with hypervitaminosis A to further explore Vegfa as a mechanistic link for the effect of vitamin A on bone. We show that bone from a human with CYP26B1 mutations displayed periosteal osteoclasts in piles within deep resorption pits, a pathognomonic sign of hypervitaminosis A. Analysis of the human angulated fetal femur revealed excessive bone formation in the marrow cavity and abundant blood vessels. Normal human endothelial cells showed disturbed cell-cell junctions and increased CYP26B1 and VEGFA expression upon RA exposure. Studies in rats showed increased plasma and tissue Vegfa concentrations and signs of bone marrow microhemorrhage on the first day of excess dietary vitamin A intake. Subsequently hypervitaminosis A rats displayed excess bone formation, fibrosis and an increased number of megakaryocytes in the bone marrow, which are known characteristics of Vegfa overexpression. This study supports the notion that the skeletal phenotype in CYP26B1 deficient human bone is caused by excess RA. Our findings suggest that an initial part of the vitamin A mechanism causing bone alterations is mediated by excess Vegfa and disturbed bone marrow microvessel integrity.

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Human CYP26B1 deficit and rat hypervitaminosis A phenocopy Vegf bone overexpression

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Hypervitaminosis A cause rapid microhemorrhage in rat bone marrow.

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Retinoic acid treatment disrupt cell-cell junction integrity between endothelial cells.

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Hypervitaminosis A have a persistent negative effect on rat bone marrow perfusion.

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Hypervitaminosis A rat bones resemble bones of patients with myelofibrotic disorders.

RARα mediates all-trans-retinoic acid-induced VEGF-C, VEGF-D, and VEGFR3 expression in lung cancer cells

The regulation of vascular endothelial growth factors C (VEGF-C) and D (VEGF-D), and their receptor VEGFR3 gene and protein expression by all-trans-retinoic acid (atRA) in A549 lung cancer cells, was investigated. We showed that atRA treatment increased VEGF-C, VEGF-D, and VEGFR3 protein and mRNA contents in dose-dependent manner. atRA-mediated increase of both ligands and receptor expression correlated with the elevated level of retinoic acid receptor α (RARα) expression, while the level of another atRA receptor, peroxisome proliferator-activated receptor β/δ (PPARβ/δ), was decreased. We demonstrated that the classical counterpart of RARα, retinoid X receptor α (RXRα), was down-regulated in both cytoplasm and nucleus of A549 cells upon atRA addition. On the contrary, the nuclear quantity of another possible RARα counterpart, transcription factor Sp1, was increased after atRA treatment.

All-trans retinoic acid and genistein induce cell apoptosis in OVCAR-3 cells by increasing the P14 tumor suppressor gene

In this study, we evaluated the effects of all-trans retinoic acid (ATRA) alone or in combination with genistein (GEN) in p14 tumor suppressor gene and subsequent apoptosis of human ovarian carcinoma cells (OVCAR-3). The cells were treated with ATRA or GEN at concentrations of 50 and 25 μM respectively, either alone or in combination for 24 and 48 h. The cell viability was evaluated using 3-(4, 5-dimethylthiazolyl-2)-2, 5-diphenyltetrazolium bromide (MTT) assay. The percentage of cell apoptosis was determined using flow cytometry and p14 gene expression was measured using real time PCR. The MTT results showed that in both ATRA and GEN treated groups, the cell viabilityviability in group treated for 48 h was significantly lower than group treated for 24 h. The flow cytometry results showed that the percentage of apoptotic cells in groups that treated with ATRA and GEN in combination for 24 h and 48 h was significantly more than all other tested groups. The real time results showed that the mRNA level of p14 in cells treated with both drugs for 48 h was significantly higher than all other groups. In conclusion, we confirm that GEN in combination with ATRA is an effective strategy to up regulate the p14 tumor suppressor gene and induce cell apoptosis in OVCAR-3 cell line.

The Use of Chemical-Chemical Interaction and Chemical Structure to Identify New Candidate Chemicals Related to Lung Cancer

Lung cancer causes over one million deaths every year worldwide. However, prevention and treatment methods for this serious disease are limited. The identification of new chemicals related to lung cancer may aid in disease prevention and the design of more effective treatments. This study employed a weighted network, constructed using chemical-chemical interaction information, to identify new chemicals related to two types of lung cancer: non-small lung cancer and small-cell lung cancer. Then, a randomization test as well as chemical-chemical interaction and chemical structure information were utilized to make further selections. A final analysis of these new chemicals in the context of the current literature indicates that several chemicals are strongly linked to lung cancer.

Solution structure of the major G-quadruplex formed in the human VEGF promoter in K+: insights into loop interactions of the parallel G-quadruplexes

Vascular endothelial growth factor (VEGF) proximal promoter region contains a poly G/C-rich element that is essential for basal and inducible VEGF expression. The guanine-rich strand on this tract has been shown to form the DNA G-quadruplex structure, whose stabilization by small molecules can suppress VEGF expression. We report here the nuclear magnetic resonance structure of the major intramolecular G-quadruplex formed in this region in K(+) solution using the 22mer VEGF promoter sequence with G-to-T mutations of two loop residues. Our results have unambiguously demonstrated that the major G-quadruplex formed in the VEGF promoter in K(+) solution is a parallel-stranded structure with a 1:4:1 loop-size arrangement. A unique capping structure was shown to form in this 1:4:1 G-quadruplex. Parallel-stranded G-quadruplexes are commonly found in the human promoter sequences. The nuclear magnetic resonance structure of the major VEGF G-quadruplex shows that the 4-nt middle loop plays a central role for the specific capping structures and in stabilizing the most favored folding pattern. It is thus suggested that each parallel G-quadruplex likely adopts unique capping and loop structures by the specific middle loops and flanking segments, which together determine the overall structure and specific recognition sites of small molecules or proteins.

LAY SUMMARY

The human VEGF is a key regulator of angiogenesis and plays an important role in tumor survival, growth and metastasis. VEGF overexpression is frequently found in a wide range of human tumors; the VEGF pathway has become an attractive target for cancer therapeutics. DNA G-quadruplexes have been shown to form in the proximal promoter region of VEGF and are amenable to small molecule drug targeting for VEGF suppression. The detailed molecular structure of the major VEGF promoter G-quadruplex reported here will provide an important basis for structure-based rational development of small molecule drugs targeting the VEGF G-quadruplex for gene suppression.

STAT5 and prolactin participate in a positive autocrine feedback loop that promotes angiogenesis

We have shown previously that the murine prolactin/growth hormone family member proliferin plays a pivotal role in angiogenesis induced by the FGF2/STAT5 signaling cascade. To delineate the signaling pathway downstream of STAT5 in the human system, where proliferin does not exist, we expressed constitutively active (CA) or dominant-negative (DN) mutant STAT5A in hCMEC/D3 human brain endothelial cells. We found that conditioned medium from CA-STAT5A- but not from DN-STAT5A-overexpressing endothelial cells (EC) is sufficient to induce EC migration and tube formation but not proliferation, indicating that STAT5A regulates the secretion of autocrine proangiogenic factors. We identified prolactin (PRL) as a candidate autocrine factor. CA-STAT5A expression stimulates PRL production at the RNA and protein level, and STAT5A binds to the PRL promoter region, suggesting direct transcriptional regulation. Medium conditioned by CA-STAT5A-overexpressing EC induces phosphorylation of the PRL receptor and activates MAPK. Knockdown of PRL expression by shRNA or blocking of PRL activity with neutralizing antibodies removed the CA-STAT5A-dependent proangiogenic activity from the conditioned medium of EC. The addition of recombinant PRL restores this activity. STAT5A-induced PRL in the conditioned medium can activate STAT5, STAT1, and to a lesser extent STAT3 in hCMEC/D3 cells, suggesting the existence of a positive feedback loop between STAT5 and PRL that promotes angiogenesis. Furthermore, we find that VEGF, a potent proangiogenic factor, is induced by activation of STAT5A, and VEGF induction depends on PRL expression. These observations demonstrate a STAT5/PRL/VEGF signaling cascade in human brain EC and implicate PRL and VEGF as autocrine regulators of EC migration, invasion, and tube formation.

Androgen up-regulates vascular endothelial growth factor expression in prostate cancer cells via an Sp1 binding site

Background

Vascular Endothelial Growth Factor (VEGF) is regulated by a number of different factors, but the mechanism(s) behind androgen-mediated regulation of VEGF in prostate cancer are poorly understood.

Results

Three novel androgen receptor (AR) binding sites were discovered in the VEGF promoter and in vivo binding of AR to these sites was demonstrated by chromatin immunoprecipitation. Mutation of these sites attenuated activation of the VEGF promoter by the androgen analog, R1881 in prostate cancer cells. The transcription factors AR and Sp1 were shown to form a nuclear complex and both bound the VEGF core promoter in chromatin of hormone treated CWR22Rv1 prostate cancer cells. The importance of the Sp1 binding site in hormone mediated activation of VEGF expression was demonstrated by site directed mutagenesis. Mutation of a critical Sp1 binding site (Sp1.4) in the VEGF core promoter region prevented activation by androgen. Similarly, suppression of Sp1 binding by Mithramycin A treatment significantly reduced VEGF expression.

Conclusions

Our mechanistic study of androgen mediated induction of VEGF expression in prostate cancer cells revealed for the first time that this induction is mediated through the core promoter region and is dependent upon a critical Sp1 binding site. The importance of Sp1 binding suggests that therapy targeting the AR-Sp1 complex may dampen VEGF induced angiogenesis and, thereby, block prostate cancer progression, helping to maintain the indolent form of prostate cancer.

Prenatal retinoic acid improves lung vascularization and VEGF expression in CDH rat

OBJECTIVE

We sought to investigate the effects of antenatal retinoic acid on the pulmonary vasculature and vascular endothelial growth factor (VEGF) and VEGF receptors (VEGFR) expression in a nitrofen-induced congenital diaphragmatic hernia (CDH) model.

STUDY DESIGN

Rat fetuses were exposed to nitrofen at gestational day 9.5 and/or all-trans retinoic acid (ATRA) at gestational days 18.5-20.5. We assessed lung growth, airway, and vascular morphometry. VEGF, VEGFR1, and VEGFR2 expression was analyzed by Western blotting and immunohistochemistry. Continuous data were analyzed by analysis of variance and Kruskal-Wallis test.

RESULTS

CDH decreased lung to body weight ratio, increased mean linear intercept and mean transection length/airspace, and decreased mean airspace cord length. ATRA did not affect lung growth or morphometry. CDH increased proportional medial wall thickness of arterioles while ATRA reduced it. ATRA recovered expression of VEGF and receptors, which were reduced in CDH.

CONCLUSION

Retinoic acid and VEGF may provide pathways for preventing pulmonary hypertension in CDH.

Maternal smoking and the retinoid pathway in the developing lung

BACKGROUND

Maternal smoking is a risk factor for pediatric lung disease, including asthma. Animal models suggest that maternal smoking causes defective alveolarization in the offspring. Retinoic acid signaling modulates both lung development and postnatal immune function. Thus, abnormalities in this pathway could mediate maternal smoking effects. We tested whether maternal smoking disrupts retinoic acid pathway expression and functioning in a murine model.

METHODS

Female C57Bl/6 mice with/without mainstream cigarette smoke exposure (3 research cigarettes a day, 5 days a week) were mated to nonsmoking males. Cigarette smoke exposure continued throughout the pregnancy and after parturition. Lung tissue from the offspring was examined by mean linear intercept analysis and by quantitative PCR. Cell culture experiments using the type II cell-like cell line, A549, tested whether lipid-soluble cigarette smoke components affected binding and activation of retinoic acid response elements in vitro.

RESULTS

Compared to tobacco-naïve mice, juvenile mice with tobacco toxin exposure had significantly (P < 0.05) increased mean linear intercepts, consistent with an alveolarization defect. Tobacco toxin exposure significantly (P < 0.05) decreased mRNA and protein expression of retinoic acid signaling pathway elements, including retinoic acid receptor alpha and retinoic acid receptor beta, with the greatest number of changes observed between postnatal days 3-5. Lipid-soluble cigarette smoke components significantly (P < 0.05) decreased retinoic acid-induced binding and activation of the retinoic acid receptor response element in A549 cells.

CONCLUSIONS

A murine model of maternal cigarette smoking causes abnormal alveolarization in association with altered retinoic acid pathway element expression in the offspring. An in vitro cell culture model shows that lipid-soluble components of cigarette smoke decrease retinoic acid response element activation. It is feasible that disruption of retinoic acid signaling contributes to the pediatric lung dysfunction caused by maternal smoking.

Anti-tumor effects of all-trans retinoic acid are enhanced by genistein

The effects of all-trans retinoic acid (ATRA) on cancer are complex. ATRA has anti-cancer effects as it promotes cancer cell differentiation. However, ATRA also up-regulates expression of vascular endothelial growth factor (VEGF) in cancer cells, which leads to angiogenesis and can, thus, facilitate cancer growth. Genistein, a crucial non-nutrient component in soybean, exhibits anti-cancer effects by inhibiting protein tyrosine kinase that is involved in up-regulation of VEGF. We hypothesized that genistein, applied simultaneously with ATRA, would counter its undesired angiogenic effects and, thus, enhance the anti-cancer effects of ATRA. The purpose of this study was to document potential synergistic effects of genistein and ATRA in A549 lung adenocarcinoma cells. We further explored the role of genistein on countering the ATRA-induced VEGF expression. We demonstrate that genistein enhances the ATRA-induced growth inhibition of A549 cells by promoting apoptosis. Further, the combined use of ATRA and genistein leads to cancer cell arrest in G0/G1 and G2/M cell cycle phases. Finally, expression of VEGF (both mRNA and protein) was diminished in A549 cells exposed to both ATRA and genistein. In conclusion, our results demonstrate that genistein effectively enhances anti-cancer effects of ATRA, particularly, by countering the ATRA-induced up-regulation of VEGF. Our study provides an experimental basis for combined use of ATRA and genistein in the treatment of lung cancer.

Cissus quadrangularis augments IGF system components in human osteoblast like SaOS-2 cells

Osteoporosis is a public health problem which is associated with significant morbidity and mortality. Growth factors are produced locally in the bone and control cellular events such as induction of bone growth. Signaling through the Insulin-like growth factor (IGF)-I receptor (IGF-IR) by locally synthesized IGF - I or IGF-II in osteoblast is considered crucial for normal development and for bone remodeling. Traditional use of Cissus quadrangularis (C. quadrangularis) in the treatment of bone disorders have been documented, however its regulatory effects on IGF system components remain largely unknown. The present study is employed to delineate the effects of ethanolic extract of C. quadrangularis on the regulation of IGF system components in human osteoblast like SaOS-2 cells. RT-PCR analysis revealed an increase in the mRNA expression of IGF-I, IGF-II, IGF-IR in cells treated with C. quadrangularis when compared with control cells. The mRNA expression of IGF binding protein-3 (IGFBP-3) did not differ significantly between control and C. quadrangularis treated cells. Immunoradiometric analysis revealed increased levels of IGF-I, IGF-II and IGFBP-3 in the conditioned medium of C. quadrangularis treated cultures when compared with control. Western blotting analysis revealed increase in protein levels of IGF-IR in cells treated with C. quadrangularis. These results indicate positive regulation of C. quadrangularis on the IGF system components of human osteoblast like SaOS-2 cells.

Vitamin A and retinoid derivatives for lung cancer: a systematic review and meta analysis

BACKGROUND

Despite reported antiproliferative activity of vitamin A and its common use for cancer, there is no comprehensive synthesis of its safety and efficacy in lung cancers. To address this issue we conducted a systematic review of the safety and efficacy of vitamin A for the treatment and prevention of lung cancers.

METHODS AND FINDINGS

Two independent reviewers searched six electronic databases from inception to July 2009 for clinical, observational, and preclinical evidence pertaining to the safety and efficacy of vitamin A and related retinoids for lung cancers. 248 studies were included for full review and analysis. Five RCTs assessed treatment of lung cancers, three assessed primary prevention, and three looked at secondary prevention of lung cancers. Five surrogate studies, 26 phase I/II, 32 observational, and 67 preclinical studies were also included. 107 studies were included for interactions between vitamin A and chemo- or radiation-therapy. Although some studies demonstrated benefits, there was insufficient evidence overall to support the use of vitamin A or related retinoids for the treatment or prevention of lung cancers. Retinyl palmitate combined with beta carotene increased risk of lung cancer in smokers in the large CARET trial. Pooling of three studies pertaining to treatment and three studies on secondary prevention revealed no significant effects on response rate, second primary tumor, recurrence, 5-year survival, and mortality. There was a small improvement in event free survival associated with vitamin A compared to controls, RR 1.24 (95% CI 1.13-1.35). The synthetic rexinoid bexarotene increased survival significantly among a subset of patients in two RCTs (p<0.014, <0.087).

CONCLUSIONS

There is a lack of evidence to support the use of naturally occurring retinoids for the treatment and prevention of lung cancers. The rexinoid bexarotene may hold promise for use among a subset of patients, and deserves further study.

In vitro footprinting of promoter regions within supercoiled plasmid DNA

Polypurine/polypyrimidine (pPu/pPy) tracts, which exist in the promoter regions of many growth-related genes, have been proposed to be very dynamic in their conformation. In this chapter, we describe a detailed protocol for DNase I and S1 nuclease footprinting experiments with supercoiled plasmid DNA containing the promoter regions to probe whether there are conformational transitions to B-type DNA, melted DNA, and G-quadruplex structures within this tract. This is demonstrated with the proximal promoter region of the human vascular endothelial growth factor (VEGF) gene, which also contains multiple binding sites for Sp1 and Egr-1 transcription factors.

Retinoic acid is a cofactor for translational regulation of vascular endothelial growth factor in human endometrial stromal cells

Vascular endothelial growth factor (VEGF) and endometrial angiogenesis play a critical role in successful embryonic implantation. Despite many studies of the effects of estrogen and progesterone on VEGF expression, its focal regulation at the site of implantation is unknown. Retinoic acid (RA) has been reported to regulate VEGF in a variety of cell types. Because localized RA synthesis occurs within the periimplantation endometrium, we tested the possibility that RA regulates VEGF production in endometrial stromal cells. Using primary and telomerase-immortalized human endometrial stromal cells, we determined that RA alone did not alter constitutive levels of VEGF production, but markedly amplified secretion when the cells were cotreated with activators of VEGF gene transcription (12-O-tetradecanoyl phorbol-13-acetate, TPA; TGF-beta; and IL-1beta). Whereas TPA or TGF-beta alone stimulated VEGF promoter activity and up-regulated mRNA levels, significant protein secretion was detected only after RA was added to the culture systems. Analysis of retinoids in secretory phase endometrial biopsies indicated that endogenous RA accumulated at concentrations sufficient to induce VEGF secretion. Polyribosome profile analysis showed that the addition of RA to transcriptional activators of VEGF shifted the translational suppressed VEGF mRNA transcripts into larger polyribosome complexes engaged in active translation. Although the precise mechanism(s) of the RA effect remains to be defined, it appears to be mediated by reactive oxygen species; the antioxidant N-acetylcysteine inhibited RA+TPA-stimulated secretion of VEGF by more than 80%. Together, our results demonstrate that in human endometrial stromal cells, RA can combine with transcriptional activators of VEGF to augment VEGF secretion through a translational mechanism of action mediated by reactive oxygen species. These findings suggest a link between the spatiotemporal changes of retinoid synthesis in the periimplantation stroma and the capacity to quickly up-regulate focal VEGF secretion needed to induce early angiogenic events of pregnancy.

Genistein inhibition of topoisomerase IIalpha expression participated by Sp1 and Sp3 in HeLa cell

Genistein (4′, 5, 7-trihydroxyisoflavone) is an isoflavone compound obtained from plants that has potential applications in cancer therapy. However, the molecular mechanism of the action of genistein on cancer cell apoptosis is not well known. In this study, we investigated the effect of genistein on topoisomerase II-α (Topo IIα), an important protein involved in the processes of DNA replication and cell proliferation. The results revealed that inhibition of Topo IIα expression through the regulation of Specificity protein 1 and Specificity protein 3 may be one of the reasons for genistein’s induction of HeLa cell apoptosis.

Antiangiogenic and proapoptotic activities of allyl isothiocyanate inhibit ascites tumor growth in vivo

The authors investigate the antiangiogenic and proapoptotic effects of mustard essential oil containing allyl isothiocyanate (AITC) and explore its mechanism of action on Ehrlich ascites tumor (EAT) cells. Swiss albino mice transplanted with EAT cells were used to study the effect of AITC. AITC was effective at a concentration of 10 mum as demonstrated by the inhibition of proliferation of EAT cells when compared with the normal HEK293 cells. It significantly reduced ascites secretion and tumor cell proliferation by about 80% and inhibited vascular endothelial growth factor expression in tumor-bearing mice in vivo. It also reduced vessel sprouting and exhibited potent antiangiogenic activity in the chorioallantoic membrane and cornea of the rat. AITC arrested the growth of EAT cells by inducing apoptosis and effectively arrested cell cycle progression at the G1 phase. The results clearly suggest that AITC inhibits tumor growth by both antiangiogenic and proapoptotic mechanisms.

The proximal promoter region of the human vascular endothelial growth factor gene has a G-quadruplex structure that can be targeted by G-quadruplex-interactive agents

Previous studies on the functional analysis of the human vascular endothelial growth factor (VEGF) promoter using the full-length VEGF promoter reporter revealed that the proximal 36-bp region (-85 to -50 relative to transcription initiation site) is essential for basal or inducible VEGF promoter activity in several human cancer cells. This region consists of a polypurine (guanine) tract that contains four runs of at least three contiguous guanines separated by one or more bases, thus conforming to a general motif capable of forming an intramolecular G-quadruplex. Here, we show that the G-rich strand in this region is able to form an intramolecular propeller-type parallel-stranded G-quadruplex structure in vitro by using the electrophoretic mobility shift assay, dimethyl sulfate footprinting technique, the DNA polymerase stop assay, circular dichroism spectroscopy, and computer-aided molecular modeling. Two well-known G-quadruplex-interactive agents, TMPyP4 and Se2SAP, stabilize G-quadruplex structures formed by this sequence in the presence of a potassium ion, although Se2SAP is at least 10-fold more effective in binding to the G-quadruplex than TMPyP4. Between these two agents, Se2SAP better suppresses VEGF transcription in different cancer cell lines, including HEC1A and MDA-MB-231. Collectively, our results provide evidence that specific G-quadruplex structures can be formed in the VEGF promoter region, and that the transcription of this gene can be controlled by ligand-mediated G-quadruplex stabilization. Our results also provide further support for the idea that G-quadruplex structures may play structural roles in vivo and therefore might provide insight into novel methodologies for rational drug design.

Retinoids increase lung elastin expression but fail to alter morphology or angiogenesis genes in premature ventilated baboons

Retinoids regulate elastin synthesis by alveolar myofibroblasts and affect angiogenesis pathways, both of which are processes critical for alveolar development. Retinoids accelerate alveolarization in rodents and are now used therapeutically in premature infants at risk of bronchopulmonary dysplasia (BPD). This study examined the effects of retinoid supplementation on alveolar elastin expression and deposition and angiogenesis-related signaling in a primate model of BPD. Premature baboons delivered at 125 d of gestation after maternal steroid treatment were given surfactant and ventilated with minimal supplemental oxygen for 14 d with (n = 5) and without (n = 5) supplemental vitamin A (5000 U/kg/d) and compared with 140-d unventilated controls. Ventilatory efficiency index (VEI) and oxygenation index (OI) were not statistically different between ventilated treatment groups. Expression of vascular endothelial growth factor A (VEGF-A), fms-related tyrosine kinase 1 (Flt-1), and tyrosine kinase with immunoglobulin-like and EGF-like domains 1 (TIE-1) was repressed by premature delivery and mechanical ventilation and was not altered by retinoid supplementation. Retinoid supplementation did not enhance alveolar angiogenesis. Elastin expression was repressed by premature delivery and extended ventilation, and retinoid supplementation increased elastin expression specifically in alveolar myofibroblasts within alveolar walls. These results suggest that the small decrease in mortality among premature infants receiving retinoid supplementation may not be mediated through enhanced alveolar development.

All-trans retinoic acid induces in vitro angiogenesis via retinoic acid receptor: possible involvement of paracrine effects of endogenous vascular endothelial growth factor signaling

A natural retinoid all-trans retinoic acid (ATRA) regulates a variety of important cellular functions via retinoic acid receptor (RAR). ATRA has therapeutically been used against various malignancies including acute promyelocytic leukemia. Recently ATRA has also been recognized to be beneficial against atherosclerotic vascular disorders. However, its effects on angiogenesis remain controversial. We therefore examined ATRA effects on in vitro angiogenesis in terms of capillary-like tube formation using human umbilical vein endothelial cells (HUVECs)/normal human dermal fibroblast (NHDF) coculture. ATRA as well as RAR agonist Am80 significantly induced capillary-like tube formation. The ATRA-induced tube formation was inhibited by coincubation with RAR antagonist LE540/LE135. HUVEC proliferation, but not its migration, was also induced by ATRA. The ATRA-induced tube formation was completely abolished by coincubation with vascular endothelial growth factor (VEGF) neutralizing antibody or with VEGF receptor (VEGFR)-2 (KDR) neutralizing antibody, but not VEGFR-1 (Flt-1) neutralizing antibody. ATRA and Am80 induced VEGF secretion in the coculture as well as VEGF secretion/mRNA expression in NHDFs. Transcription activity of human VEGF gene promoter in NHDFs was stimulated by ATRA, which was augmented by RAR overexpression. ATRA also induced VDGFR-2/KDR mRNA expression in HUVECs. Moreover, ATRA-induced secretion of hepatocyte growth factor as well as angiopoietin-2 in the coculture. Taken together, ATRA may have induced angiogenesis via RAR mainly by stimulation of HUVEC proliferation and enhancement of endogenous VEGF signaling and in part by induction of hepatocyte growth factor and angiopoietin-2 production. Retinoids may therefore be potential candidates for therapeutic angiogenesis against ischemic vascular disorders.

Acitretin induces capillary leak syndrome in a patient with pustular psoriasis

Capillary leak syndrome is a rare and potentially life-threatening condition caused by a shift of intravascular fluid and proteins to the interstitial space. We describe a patient with pustular psoriasis in whom capillary leak syndrome developed after the start of acitretin. Immediate withdrawal of retinoic acid is necessary and corticosteroid therapy should be considered.

All-trans-retinoic acid prevents radiation- or bleomycin-induced pulmonary fibrosis

RATIONALE

Although radiotherapy is effective in treating lung cancers, resultant pulmonary injury is the main obstacle. Pulmonary fibrosis is characterized by progressive worsening in pulmonary function leading to high incidence of death. Currently, however, there has been little progress in effective preventive and therapeutic strategies.

OBJECTIVES

Previously, we reported that all-trans-retinoic acid (ATRA) reduced both irradiation-induced interleukin (IL)-6 production in lung fibroblasts and IL-6-dependent cell growth, and also directly inhibited the proliferation of lung fibroblasts after irradiation. In this study, we examined the preventive effect of ATRA on the progression of lung fibrosis both in irradiated and bleomycin-treated mice.

MEASUREMENTS

We performed histologic examinations and quantitative measurements of IL-6, transforming growth factor (TGF)-beta(1), and collagen type Ialpha1 (COL1A1) in irradiated and bleomycin- treated mouse lung tissues with or without the administration of ATRA.

RESULTS

Lethal irradiation effect was reduced by intraperitoneal administration of ATRA, and the overall survival rate at 16 wk was 30.0% without ATRA (n = 11), whereas it was 81.8% (n = 10) in the treatment group (p = 0.04). In vitro studies disclosed that the administration of ATRA reduced (1) irradiation-induced production of IL-6, TGF-beta(1), and collagen from IMR90 cells, and (2) IL-6-dependent proliferation and TGF-beta(1)-dependent transdifferentiation of the cells, which could be the mechanism underlying the preventive effect of ATRA on lung fibrosis. Furthermore, ATRA ameliorated bleomycin-induced fibrosis in mouse lung tissues.

CONCLUSIONS

These data may provide a rationale to explore clinical use of ATRA for the prevention of radiation-induced lung fibrosis and other pathologic conditions involving pulmonary fibrosis.

Angiogenic and proliferative effects of the cytokine VEGF in Ehrlich ascites tumor cells is inhibited by Glycyrrhiza glabra

Blood vessel plays a crucial role in solid tumor development. It has been suggested that blocking of angiogenesis and the action of the cytokine VEGF could be possible in cancer therapy. In a screen for naturally occurring angiogenic inhibitors, we have identified an extract from the roots of Glycyrrhiza glabra, which has potent antiangiogenic and antitumor activity. The aqueous extract inhibits the in vivo and in vitro proliferation of Ehrlich ascites tumor cells. The angioinhibitory activity of G. glabra was confirmed by its inhibition of angiogenesis in in vivo assays, peritoneal and chorioallantoic membrane assay. Reduction in the levels of the cytokine VEGF and microvessel density count in the peritoneum of mice treated with G. glabra indicated that the plant extract decreased VEGF production and the cytokine induced neovascularization. Our results suggest that the extract from the roots of G. glabra may be a potential supplemental source for cancer therapy.

All-trans retinoic acid modulates radiation-induced proliferation of lung fibroblasts via IL-6/IL-6R system

Although high-dose thoracic radiotherapy is an effective strategy for some malignancies including lung cancers and malignant lymphomas, it often causes complications of radiation fibrosis. To study the mechanism initiating tissue fibrosis, we investigated irradiation-induced cytokine production from human lung fibroblastic cells and found that IL-6 production was stimulated by irradiation. IL-6 is an autocrine growth factor for human myeloma cells, and retinoic acid is reported to inhibit their growth. Thus we evaluated the effect of all-trans retinoic acid (ATRA) on cell proliferation of lung fibroblasts along with the cytokine/receptor system. Irradiation-dependent stimulation of IL-6 production was correlated with increased NF-kappaB activity, and ATRA reduced this effect. Irradiation also increased the levels of mRNA for IL-6R and gp130, which were blocked by coexisting ATRA. Furthermore, IL-6 stimulated cell proliferation in dose-dependent manner but was overcome by pharmacological concentration of ATRA. These effects of ATRA were inhibited by rottlerin, which suggests ATRA abolished irradiation-induced stimulation through a PKCdelta-dependent pathway. Finally, we demonstrated that IL-6 transcripts in the lung were upregulated at 2 mo after irradiation, and the effect was inhibited by the intraperitoneal administration of ATRA. ATRA is expected to have an advantage for radiotherapy in its antitumor effects, as reported previously, and to prevent radiotherapy-induced pulmonary injury.

Facilitation of a structural transition in the polypurine/polypyrimidine tract within the proximal promoter region of the human VEGF gene by the presence of potassium and G-quadruplex-interactive agents

The proximal promoter region of the human vascular endothelial growth factor (VEGF) gene contains a polypurine/polypyrimidine tract that serves as a multiple binding site for Sp1 and Egr-1 transcription factors. This tract contains a guanine-rich sequence consisting of four runs of three or more contiguous guanines separated by one or more bases, corresponding to a general motif for the formation of an intramolecular G-quadruplex. In this study, we observed the progressive unwinding of the oligomer duplex DNA containing this region into single-stranded forms in the presence of KCl and the G-quadruplex-interactive agents TMPyP4 and telomestatin, suggesting the dynamic nature of this tract under conditions which favor the formation of the G-quadruplex structures. Subsequent footprinting studies with DNase I and S1 nucleases using a supercoiled plasmid DNA containing the human VEGF promoter region also revealed a long protected region, including the guanine-rich sequences, in the presence of KCl and telomestatin. Significantly, a striking hypersensitivity to both nucleases was observed at the 3′-side residue of the predicted G-quadruplex-forming region in the presence of KCl and telomestatin, indicating altered conformation of the human VEGF proximal promoter region surrounding the guanine-rich sequence. In contrast, when specific point mutations were introduced into specific guanine residues within the G-quadruplex-forming region (Sp1 binding sites) to abolish G-quadruplex-forming ability, the reactivity of both nucleases toward the mutated human VEGF proximal promoter region was almost identical, even in the presence of telomestatin with KCl. This comparison of wild-type and mutant sequences strongly suggests that the formation of highly organized secondary structures such as G-quadruplexes within the G-rich region of the human VEGF promoter region is responsible for observed changes in the reactivity of both nucleases within the polypurine/polypyrimidine tract of the human VEGF gene. The formation of the G-quadruplex structures from this G-rich sequence in the human VEGF promoter is further confirmed by the CD experiments. Collectively, our results provide strong evidence that specific G-quadruplex structures can naturally be formed by the G-rich sequence within the polypurine/polypyrimidine tract of the human VEGF promoter region, raising the possibility that the transcriptional control of the VEGF gene can be modulated by G-quadruplex-interactive agents.

Retinoic acid activates human secretin gene expression by Sp proteins and nuclear factor I in neuronal SH-SY5Y cells

Secretin is a neuropeptide that is expressed in distinct central neurones. As there is no information on how the secretin gene is regulated in neuronal cells, a well established neuronal differentiation cell model, SH-SY5Y, was used to study transcriptional regulation of the human secretin gene. High secretin transcript and peptide levels were found in this cell, and secretin gene expression and promoter activity were up-regulated upon all-trans retinoic acid (RA) treatment. Within the promoter, a functional GC-box 1 (-131 from ATG, relative to the ATG initiation codon) was found to be regulated by a brain-specific Sp protein, Sp4, and ubiquitous factors Sp1 and Sp3. The human secretin gene in SH-SY5Y cells is controlled by the (Sp1 + Sp4)/Sp3 ratio and the RA-induced activation is a partial result of a decrease in Sp3 levels. In addition to the GC-box 1, an N1 motif in close proximity was also responsible for RA-induced secretin gene activation. Competitive gel mobility shift and southwestern blot studies revealed binding of Nuclear Factor I (NFI) with the N1 motif. Overexpression of NFI-C increased promoter activity upon RA treatment. Consistent with this observation, NFI-C transcript levels were augmented after RA treatment. We conclude that RA induction of the secretin gene in neuronal cells is regulated by the combined actions of reducing Sp3 and increasing NFI-C expression.

Possible involvement of p44/p42 MAP kinase in retinoic acid-stimulated vascular endothelial growth factor release in aortic smooth muscle cells

Retinoic acid modulates cell growth and differentiation of the vascular system. Vascular endothelial growth factor (VEGF) is known as a vascular permeability factor and a potent mitogen for vascular endothelial cells. In the present study, we investigated whether retinoic acid induces VEGF release in aortic smooth muscle A10 cells and if so, the mechanism of VEGF release. Retinoic acid stimulated VEGF release dose-dependently over the range 0.1 nM-0.1 microM. The retinoic acid-stimulated VEGF release was significantly reduced by actinomycin D. Retinoic acid induced the phosphorylation of p44/p42 mitogen-activated protein (MAP) kinase but not p38 MAP kinase or stress-activated protein kinase/c-Jun N-terminal kinase among the MAP kinase superfamily. This effect of retinoic acid was dose-dependent (30 nM-5 microM) and the maximum effect was observed at 0.3 microM. The retinoic acid-stimulated release of VEGF was significantly reduced by PD98059 and U0126, specific MEK inhibitors, which attenuated the retinoic acid-induced phosphorylation of p44/p42 MAP kinase. These results strongly suggest that retinoic acid stimulates the release of VEGF in a p44/p42 MAP kinase-dependent manner in aortic smooth muscle cells.

Critical role for retinol in the generation/differentiation of angioblasts required for embryonic blood vessel formation

Numerous studies demonstrate that vitamin A (retinol) deficiency causes abnormal cardiovascular morphogenesis. We evaluated the impact of retinol deficiency on the regulation of the numbers of endothelial cells and angioblasts (endothelial progenitors) produced during embryonic quail development. At the one-somite stage, there were no discernible differences in the mean number of endothelial cells or angioblasts in normal and retinol-deficient embryos. However, retinol-deficient embryos at the three-somite stage had an increase in the mean number of endothelial cells but no difference in the mean number of angioblasts. By contrast, retinol-deficient embryos at the five-somite stage have 61% of the normal number of endothelial cells and 12% of the normal number of angioblasts. Similarly, retinol-deficient embryos at the 10-somite stage had 71% and 60% of normal numbers of endothelial cells in capillary-like networks and the sinuses venosus, respectively. Furthermore, we show that retinol deficiency did not elicit a global reduction in mesodermal cell numbers but was specific to cells of the endothelial lineage. Taken together, our findings suggest that vascular abnormalities observed under conditions of retinol deficiency are due to reduction in the number of angioblasts and consequently an insufficiency in the number of endothelial cells required to build complex vascular networks.

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.

Retinoic acid-induced alveolar cellular growth does not improve function after right pneumonectomy

To determine whether all- trans retinoic acid (RA) treatment enhances lung function during compensatory lung growth in fully mature animals, adult male dogs ( n = 4) received 2 mg·kg-1·day-1po RA 4 days/wk beginning the day after right pneumonectomy (R-PNX, 55-58% resection). Litter-matched male R-PNX controls ( n = 4) received placebo. After 3 mo, transpulmonary pressure (TPP)-lung volume relationship, diffusing capacities for carbon monoxide and nitric oxide, cardiac output, and septal volume (Vtiss-RB) were measured under anesthesia by a rebreathing technique at two lung volumes. Lung air and tissue volumes (Vair-CTand Vtiss-CT) were also measured from high-resolution computerized tomographic (CT) scans at a constant TPP. In RA-treated dogs compared with controls, TPP-lung volume relationships were similar. Diffusing capacities for carbon monoxide and nitric oxide were significantly impaired at a lower lung volume but similar at a high lung volume. Whereas Vtiss-RBwas significantly lower at both lung volumes in RA-treated animals, Vair-CTand Vtiss-CTwere not different between groups; results suggest uneven distribution of ventilation consistent with distortion of alveolar geometry and/or altered small airway function induced by RA. We conclude that RA does not improve resting pulmonary function during the early months after R-PNX despite histological evidence of its action in enhancing alveolar cellular growth in the remaining lung.

Retinoic acid induces nonuniform alveolar septal growth after right pneumonectomy

To determine whether all- trans retinoic acid (RA) enhances compensatory lung growth in fully mature animals, adult male dogs ( n = 4) received 2 mg·kg-1·day-1 po RA 4 days/wk beginning the day after right pneumonectomy (R-PNX, 55-58% resection). Litter-matched male R-PNX controls ( n = 4) received placebo. After 4 mo, the remaining lung was fixed by tracheal instillation of fixatives at a constant airway pressure for detailed morphometric analysis. After RA treatment compared with placebo, lung volume was slightly but not significantly lower. Volume density of septum to lung was 37% higher because of a 50 and 25% higher volume density of capillary and septal tissue, respectively. Mean septal thickness was 27% higher. Absolute volumes of endothelial cells and capillary blood were 31-37% higher, whereas epithelial and interstitial volumes were not different between groups. Absolute alveolar-capillary surface areas did not differ between groups, and alveolar septal surface-to-volume ratio was 20% lower in RA-treated animals. RA treatment exaggerated interlobar differences in morphometric indexes and caused alveolar capillary morphology to revert to a more immature state. Thus RA treatment during early post-R-PNX adaptation preferentially enhanced alveolar capillary and endothelial cell volumes consistent with formation of new capillaries, but the associated septal distortion precluded a corresponding increase in gas-exchange surface or morphometric estimates of lung diffusing capacity.

Anticancer therapeutic potential of soy isoflavone, genistein

Genistein (4'5, 7-trihydroxyisoflavone) occurs as a glycoside (genistin) in the plant family Leguminosae, which includes the soybean (Glycine max). A significant correlation between the serum/plasma level of genistein and the incidence of gender-based cancers in Asian, European and American populations suggests that genistein may reduce the risk of tumor formation. Other evidence includes the mechanism of action of genistein in normal and cancer cells. Genistein inhibits protein tyrosine kinase (PTK), which is involved in phosphorylation of tyrosyl residues of membrane-bound receptors leading to signal transduction, and it inhibits topoisomerase II, which participates in DNA replication, transcription and repair. By blocking the activities of PTK, topoisomerase II and matrix metalloprotein (MMP9) and by down-regulating the expression of about 11 genes, including that of vascular endothelial growth factor (VEGF), genistein can arrest cell growth and proliferation, cell cycle at G2/M, invasion and angiogenesis. Furthermore, genistein can alter the expression of gangliosides and other carbohydrate antigens to facilitate their immune recognition. Genistein acts synergistically with drugs such as tamoxifen, cisplatin, 1,3-bis 2-chloroethyl-1-nitrosourea (BCNU), dexamethasone, daunorubicin and tiazofurin, and with bioflavonoid food supplements such as quercetin, green-tea catechins and black-tea thearubigins. Genistein can augment the efficacy of radiation for breast and prostate carcinomas. Because it increases melanin production and tyrosinase activity, genistein can protect melanocytes of the skin of Caucasians from UV-B radiation-induced melanoma. Genistein-induced antigenic alteration has the potential for improving active specific immunotherapy of melanoma and carcinomas. When conjugated to B43 monoclonal antibody, genistein becomes a tool for passive immunotherapy to target B-lineage leukemias that overexpress the target antigen CD19. Genistein is also conjugated to recombinant EGF to target cancers overexpressing the EGF receptor. Although genistein has many potentially therapeutic actions against cancer, its biphasic bioactivity (inhibitory at high concentrations and activating at low concentrations) requires caution in determining therapeutic doses of genistein alone or in combination with chemotherapy, radiation therapy, and/or immunotherapies. Of the more than 4500 genistein studies in peer-reviewed primary publications, almost one fifth pertain to its antitumor capabilities and more than 400 describe its mechanism of action in normal and malignant human and animal cells, animal models, in vitro experiments, or phase I/II clinical trials. Several biotechnological firms in Japan, Australia and in the United States (e.g., Nutrilite) manufacture genistein as a natural supplement under quality controlled and assured conditions.

The transcription factor Net regulates the angiogenic switch

Angiogenesis is fundamental to physiological and pathological processes. Despite intensive efforts, little is known about the intracellular circuits that regulate angiogenesis. The transcription factor Net is activated by phosphorylation induced by Ras, an indirect regulator of angiogenesis. Net is expressed at sites of vasculogenesis and angiogenesis during early mouse development, suggesting that it could have a role in blood vessel formation. We show here that down-regulation of Net inhibits angiogenesis and vascular endothelial growth factor (VEGF) expression in vivo, ex vivo, and in vitro. Ras-activated phosphorylated Net (P-Net) stimulates the mouse VEGF promoter through the -80 to -53 region that principally binds Sp1. P-Net and VEGF are coexpressed in angiogenic processes in wild-type mouse tissues and in human tumors. We conclude that Net is a regulator of angiogenesis that can switch to an activator following induction by pro-angiogenic molecules.

Regulation of vascular endothelial growth factor gene expression in murine macrophages by nitric oxide and hypoxia

Vascular endothelial growth factor (VEGF) expression in murine peritoneal macrophages is strongly upregulated by hypoxia via transcriptional and posttranscriptional mechanisms. Interferon-gamma (IFN-gamma) with Escherichia coli lipopolysaccharide (LPS) also upregulates expression of VEGF, as well as of the inducible nitric oxide synthase (iNOS). Hypoxia (1% O(2)) upregulates VEGF expression in macrophages from both wild-type and iNOS knockout mice, indicating that hypoxic upregulation of VEGF is independent of iNOS. However, the iNOS inhibitor aminoguanidine (AG) decreases the VEGF expression induced by LPS/IFN-gamma, indicating an important role for NO. NO-dependent induction of VEGF is strongly dependent on cell density. LPS/IFN-gamma treatment induces minimal VEGF protein expression in macrophages cultured at low cell densities (<0.25 x 10(6) cells/cm(2)); at higher cell densities (>0.25 x 10(6) cells/cm(2)) that lead to conditions of pericellular hypoxia, however, induction of VEGF expression was strong. Transient transfection of RAW 264.7 cells with luciferase reporter constructs of the murine VEGF promoter indicates that both hypoxia and LPS/IFN-gamma independently induce VEGF promoter activity, irrespective of cell density. Although LPS/IFN-gamma treatment induces transcriptional activation of the VEGF promoter, significant levels of VEGF protein are only expressed by cells at high density under conditions of pericellular hypoxia. This suggests an important regulatory role for hypoxia at the posttranscriptional level. Deletion analysis of the VEGF promoter shows that the hypoxia response element region and its immediate flanking sequences are essential for both hypoxia and LPS/IFN-gamma-induced VEGF promoter activation.