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Biomedical subjects

Roy Bicknell

Publications and source records attributed to Roy Bicknell.

28 records · Page 2Linked to original sources
PubMed2002

Peptide blockade of HIFalpha degradation modulates cellular metabolism and angiogenesis.

Hypoxia-inducible factor-1 (HIF) is a transcription factor central to oxygen homeostasis. It is regulated via its alpha isoforms. In normoxia they are ubiquitinated by the von Hippel-Lindau E3 ligase complex and destroyed by the proteasome, thereby preventing the formation of an active transcriptional complex. Oxygen-dependent enzymatic hydroxylation of either of two critical prolyl residues in each HIFalpha chain has recently been identified as the modification necessary for targeting by the von Hippel-Lindau E3 ligase complex. Here we demonstrate that polypeptides bearing either of these prolyl residues interfere with the degradative pathway, resulting in stabilization of endogenous HIFalpha chains and consequent up-regulation of HIF target genes. Similar peptides in which the prolyl residues are mutated are inactive. Induction of peptide expression in cell cultures affects physiologically important functions such as glucose transport and leads cocultured endothelial cells to form tubules. Coupling of these HIFalpha sequences to the HIV tat translocation domain allows delivery of recombinant peptide to cells with resultant induction of HIF-dependent genes. Injection of tat-HIF polypeptides in a murine sponge angiogenesis assay causes a markedly accelerated local angiogenic response and induction of glucose transporter-1 gene expression. These results demonstrate the feasibility of using these polypeptides to enhance HIF activity, opening additional therapeutic avenues for ischemic diseases.

Animals↗
PubMed2002

Adrenomedullin promotes formation of xenografted endometrial tumors by stimulation of autocrine growth and angiogenesis.

The angiogenic peptide adrenomedullin (ADM) has been implicated as a mediator of the increased risk of endometrial hyperplasia and cancer resulting from the use of tamoxifen for the treatment and prevention of breast cancer. ADM has been shown to be induced by tamoxifen in the endometrium and to be a growth factor for endometrial endothelial cells in vitro. We have now shown ADM to be strongly angiogenic in the mouse subcutaneous sponge angiogenesis assay. To examine the role of ADM in tumor growth, the ADM cDNA was transfected into endometrial carcinoma cells followed by xenografting into athymic mice. Two endometrial cancer cell lines were employed, those in which transfection and expression of ADM resulted in no effect on growthin vitro (Ishikawa cells) and those in which expressionof exogenous ADM stimulated in vitro growth (RL95.2 cells). A clear enhancement of tumor growth was seen with both cell lines but the effect was far greater with the RL95.2 cells. We conclude that ADM is pro-tumorigenic by stimulating either angiogenesis alone or by stimulating angiogenesis and carcinoma cell growth directly. The combined activities lead to a striking increase in tumor growth. These results provide the first direct evidence of tumorigenic activity of ADM and provide further support for ADMs involvement in tamoxifen induced endometrial neoplasia.

Adrenomedullin↗
PubMed2002

Relation of hypoxia-inducible factor-2 alpha (HIF-2 alpha) expression in tumor-infiltrative macrophages to tumor angiogenesis and the oxidative thymidine phosphorylase pathway in Human breast cancer.

Tumor-associated macrophages (TAMs) produce angiogenic factors and in breast cancer are associated with high vascular grade and poor survival. TAMs preferentially migrate to hypoxic areas within tumors and strongly express hypoxia-inducible factor (HIF)-2 alpha. This study examined whether HIF-2 alpha was involved in TAM angiogenic activation by correlating its expression with tumor microvessel density as a marker of angiogenesis, and other tumor variables, in a series of human primary invasive breast carcinomas. A correlation was found between high TAM HIF-2 alpha and high tumor vascularity (P < 0.0001), as well as high tumor grade (P = 0.007). The relation of HIF-2 alpha expression to a recently described oxygen-dependent pathway of angiogenesis was also studied, and an inverse relationship was found between TAM HIF-2 alpha and tumor thymidine phosphorylase expression (P = 0.02). These results suggest that TAM HIF-2 signaling may be a useful target for future antiangiogenic strategies but show that tumors use both oxygen-dependent and oxygen deficiency-regulated pathways for angiogenesis. Thus, combined blockade of pathways and careful assessment of these pathways in trials are necessary.

Adult↗
PubMed2002

Mediation of systemic vascular hyperpermeability in severe psoriasis by circulating vascular endothelial growth factor.

BACKGROUND: Severe forms of psoriasis can be complicated by systemic microvascular hyperpermeability. Vascular endothelial growth factor (VEGF) possesses potent vascular permeability activity. We suggest that VEGF enters the systemic circulation and acts on microvessels to mediate hyperpermeability. OBJECTIVES: To quantify renal microvascular permeability and circulating VEGF concentration in severe psoriasis, and to investigate the relationship between plasma VEGF concentration and skin and joint involvement. DESIGN: Inception cohort studies of patients with generalized pustular psoriasis and plaque psoriasis. SETTING: St John's Institute of Dermatology, London, England. PATIENTS: Twenty-two patients (15 men and 7 women) with moderate and severe psoriasis were recruited (age range, 29-77 years; mean age, 47 years); 5 had generalized pustular psoriasis, 2 had erythrodermic psoriasis, and 15 had moderate-severe plaque psoriasis. An age- and sex-matched control group of 17 individuals (10 men and 7 women) was recruited (age range, 29-69 years; mean age, 42 years). RESULTS: There was pathological proteinuria in patients with relapsing generalized pustular psoriasis, (4-fold increase in urinary protein excretion rate in relapse compared with remission). In patients with moderate and severe psoriasis, mean plasma VEGF concentration during relapse was approximately 2.5 times greater than during remission (mean VEGF(relapse) = 257 pg/mL; mean VEGF(remission) = 103 pg/mL; P<.01). There was a correlation between extent of skin involvement and plasma VEGF level (mean VEGF(severe psoriasis) = 365 pg/mL; mean VEGF(moderate psoriasis) = 149 pg/mL; P =.03). There was a correlation between presence of psoriatic arthritis and plasma VEGF level (mean relapse VEGF(arthritis) = 277 pg/mL; mean relapse VEGF(nonarthritis) = 103.5 pg/mL; P =.03). CONCLUSIONS: Generalized pustular psoriasis is accompanied by pathological proteinuria and elevated plasma VEGF levels. Plasma VEGF concentration is significantly elevated in patients with extensive skin and joint involvement and may act on renal microvasculature to induce hyperpermeability.

Adult↗
PubMed2002

Angiogenic co-operation of VEGF and stromal cell TP in endometrial carcinomas.

Vascular endothelial growth factor (VEGF) and thymidine phosphorylase (TP) are important angiogenic enzymes, inducing new blood vessel formation in many human malignancies. In this study, the immunohistochemical expression of the two molecules was analysed in a series of 121 endometrial carcinomas. VEGF was expressed exclusively in cancer cells, while TP expression was shown in cancer cells (TPcc) and in stromal cells (TPsc) of both fibroblastic and myometrial origin. In all cases, enzymatic detection was particularly evident at the invading tumour front. At this site, TPsc, but not VEGF, expression was associated with non-endometrioid-type carcinomas, high tumour grade, deep myometrial invasion, and advanced stage. VEGF, but not TP, expression was related to increased angiogenesis (p=0.01). Double stratification of the two factors, however, marked VEGF/TPsc co-expression as the most potent angiogenic phenotype (p=0.008), suggesting a synergistic function. Survival analysis revealed that VEGF and TPsc, whether expressed alone or in combination, define poor prognosis. In multivariate analysis, however, stage of disease (p<0.0001, t-ratio 4.4) and VEGF expression (p=0.01, t-ratio 2.4) were the most important prognostic variables. Furthermore, VEGF expression emerged as the only independent prognostic variable in stage I endometrial carcinomas (p=0.04, t-ratio 1.9). This was not shown for TP, probably because of its close association with histopathological parameters. In conclusion, VEGF is a major angiogenic factor in endometrial carcinomas and an independent prognostic factor in stage I endometrial disease. TP is not an effective contributor to the angiogenic process, but is associated with aggressive histological features. The two factors, when co-expressed, play a co-operative role in the induction of angiogenesis.

Biomarkers, Tumor↗
PubMed2002

Magic roundabout is a new member of the roundabout receptor family that is endothelial specific and expressed at sites of active angiogenesis.

We have used bioinformatic data mining to identify a novel, endothelial-specific gene encoding a protein with homology to the axon guidance protein roundabout (ROBO1). The new gene has been called magic roundabout (ROBO4; GenBank acc. no. AF361473) and is smaller than other members of the roundabout gene family. Thus, in the extracellular region, magic roundabout has only two of the five immunoglobulin and two of the three fibronectin domains present in other roundabout genes. Expression of magic roundabout in vitro was detected in only endothelial cells and was greater in cells exposed to hypoxia. In situ hybridization and immunohistochemistry validated the bioinformatic prediction that magic roundabout expression would be endothelial specific in vivo. Magic roundabout expression in the adult was restricted exclusively to sites of active angiogenesis, notably tumor vessels. The identification of magic roundabout shows that the roundabout gene family extends beyond neuronal tissue and that roundabout/slit interactions are likely to have a role in angiogenesis.

Amino Acid Sequence↗
PubMed2002

Recent advances in angiogenesis, anti-angiogenesis and vascular targeting.

Angiogenesis, the development of new blood vessels, has become a major focus of research. This has been stimulated by the therapeutic opportunities offered by the ability to manipulate the vasculature in pathologies such as cancer. Here, we present an overview of recent advances in angiogenesis. Especially noteworthy is the large volume of information from developmental studies, particularly those that involve transgenic and gene knockout mice. We also discuss the increasing repertoire of drugs with which to manipulate angiogenesis and new endothelial-specific genes with which to target the vasculature.

Angiogenesis Inducing Agents↗
PubMed2002

Angiogenesis in the corpus luteum of early pregnancy in the marmoset and the effects of vascular endothelial growth factor immunoneutralization on establishment of pregnancy.

This study investigated vascular and molecular changes in the corpus luteum (CL) of early pregnancy in the marmoset. Ovaries were studied on Days 21 (n = 6) and 28 (n = 6) of pregnancy and compared with corpora lutea from Day 21 (late luteal) of the nonconception cycle (n = 8). Endothelial cell proliferation was measured by immunocytochemical detection of incorporated bromodeoxyuridine. Endothelial cell and pericyte area were assessed by quantitative immunocytochemistry for CD31 and alpha-smooth muscle actin, respectively. Vascular endothelial growth factor (VEGF) and its receptors, kinase insert domain-containing region (KDR) and fms-like tyrosine kinase (Flt) mRNA, were localized and quantified in in situ hybridization. In addition, the effects of immunoneutralization of VEGF on establishment and maintenance of pregnancy were investigated by administering a VEGF neutralizing antibody on Days 0-10 of the luteal phase during potentially fertile cycles (n = 10) and compared with fertile controls (n = 6). No differences in the cellular or morphological parameters were found between pregnant and structurally intact nonpregnant corpora lutea. No major differences were found in expression of VEGF, Flt, or KDR in these CL. VEGF immunoneutralization markedly suppressed plasma progesterone secretion during treatment, but pregnancy rate was not significantly reduced. Thus, a role for VEGF in early pregnancy in the marmoset remains to be established. These results show that, by the late luteal phase in the marmoset, the corpus luteum has established a mature vascular system and the molecular capacity to synthesize VEGF and its receptors. A pregnancy-induced spurt of angiogenesis or gene expression does not appear to take place; rather, maintenance of the existing vasculature is all that is required for the establishment of pregnancy.

Animals↗
PubMed2002

Role of thymidine phosphorylase in an in vitro model of human bladder cancer invasion.

PURPOSE: It has been previously demonstrated that the angiogenic factor thymidine phosphorylase is elevated significantly in invasive bladder cancer. We report that it is not merely an incidental finding. Thymidine phosphorylase has a functional role in bladder cancer invasion. MATERIALS AND METHODS: The superficial bladder cancer cell line RT112 was transfected by retroviral techniques to generate the RT112-TP clone that expressed significantly elevated levels of thymidine phosphorylase, comparable to those of invasive human bladder cancers. The empty vector control RT112-EV was generated for comparison. Growth of these transfectants was examined using a new in vitro model of bladder cancer invasion based on de-epithelialized rat bladder and by assessing growth as xenografts in nude mice. The effect of 5-deoxy-5-fluorouridine, a prodrug activated by TP to produce 5-fluorouracil, was also examined. RESULTS: RT112-TP high thymidine phosphorylase expressing cells invaded into the stroma of the in vitro model but wild-type RT112 and RT112-EV cells did not. This invasion was abolished by 5-deoxy-5-fluorouridine. Invasion correlated with thymidine phosphorylase expression on immunohistochemical testing. There was also a significantly greater xenograft growth rate for RT112-TP than for RT112-EV, confirming the malignant growth advantage conferred by thymidine phosphorylase. CONCLUSIONS: We demonstrated that thymidine phosphorylase may have a functional role in bladder cancer invasion and the apparent advantage of thymidine phosphorylase expression to tumor cells can be exploited by therapies that utilize prodrugs such as 5-deoxy-5-fluorouridine, which is activated by thymidine phosphorylase and inhibited invasion in our model.

Animals↗