Biomedical subjects

A L Harris

Publications and source records attributed to A L Harris.

At least 217 records · Page 12Linked to original sources

PubMed1998

Expression and subcellular localization of human AP endonuclease 1 (HAP1/Ref-1) protein: a basis for its role in human disease.

AIMS: Human AP endonuclease 1 (HAP1) plays a major role in the repair of apurinic/apyrimidinic (AP) sites in cellular DNA by catalysing hydrolytic cleavage of the phosphodiester backbone 5' to the site. HAP1 is also known to be a potent reduction-oxidation (redox) factor, regulating the binding activity of a number of transcription factors. The purpose of the present study was to examine the expression of HAP-1 in a wide range of human tissues. METHODS AND RESULTS: Using a recently developed specific rabbit polyclonal antibody, we performed immunohistochemistry on paraffin-embedded tissue material. Nuclear staining was detected in crypt cells of the small and large intestine, epithelial cells of breast ducts, basal cells of the skin, alveolar cells of the lung, lymphocytes of the marginal zone of the spleen, in the surface epithelium and stromal cells of the ovary and the transitional epithelium of the bladder. Unexpectedly for a presumed nuclear protein, the staining pattern in some cell populations was mainly cytoplasmic (e.g. superficial cells of gastrointestinal tract, Langerhans cells, Leydig cells and spermatocytes, epithelium of the prostate glands), or both cytoplasmic and nuclear (e.g. epithelial cells of thymus, follicular thyroid cells, parietal cells of the stomach, glandular epithelial cells of the cervix, epithelial cells of exocrine pancreas). CONCLUSION: This differential expression in a wide spectrum of cells is indicative of a potential multifunctional action of HAP1, not necessarily restricted to a role in the nucleus.

Antibodies↗

PubMed1998

MUC1 (episialin) expression in non-small cell lung cancer is independent of EGFR and c-erbB-2 expression and correlates with poor survival in node positive patients.

AIM: To examine tumour samples immunohistochemically for MUC1 (episialin), epidermal growth factor receptor (EGFR), and c-erbB-2, since the disruption of the cell-cell adhesion system by MUC1 and the c-erbB oncoprotein family is known to be important in the development of metastasis in human cancers. METHODS: 93 tumour samples from patients with early stage non-small cell lung cancer treated with surgery alone were examined for episialin, EGFR, and c-erbB-2. RESULTS: Episialin depolarised expression did not correlate with any of the histopathological variables examined (T,N stage, grade, histology, Ki67 proliferation index). No correlation was observed between episialin and EGFR or c-erbB-2 expression. Survival analysis showed that episialin depolarised expression correlated with poor prognosis (p = 0.003), especially in squamous cell cases (p = 0.0003). Episialin expression defined a group of patients with poor prognosis in the node positive category (p = 0.003). In multivariate analysis episialin was the most significant independent prognostic factor (p = 0.007), followed by N stage (p = 0.04). CONCLUSIONS: Depolarised expression of episialin is associated with poor outcome in early stage non-small cell lung cancer. Despite the similar activity on the cadherin cell-cell adhesion system, the expression of episialin and c-erbB oncoproteins is likely to be activated within different pathogenic pathways.

Aged↗

PubMed1998

Anti-angiogenic therapies in cancer clinical trials.

Strategies involving vasculature have widely been acknowledged to have therapeutic potential in the management of cancer and other diseases. Based on a large body of evidence from preclinical studies and early clinical trials there is considerable optimism that anti-angiogenesis and vascular targeting will be a major clinical therapy. This review considers some 30 anti-angiogenic and vascular targeting agents that are currently in cancer clinical trials and highlights specific problems relating to the assessment of the activity of these agents in patients, trial design, potential toxicities and resistance mechanisms.

Journal Article↗

PubMed1998

Vascular endothelial growth factor, wild-type p53, and angiogenesis in early operable non-small cell lung cancer.

Vascular endothelial growth factor (VEGF) is a cytokine that is involved in tumor angiogenesis. Wild-type p53 (wt-p53) protein has been shown in cell lines to suppress angiogenesis through thrombospondin regulation. In this study, we immunohistochemically examined the expression of VEGF, nuclear and wild-type cytoplasmic p53, bcl-2, epidermal growth factor receptor, and c-erbB-2 oncoprotein; vascular grade; proliferation index; and extent of necrosis in non-small cell lung cancer (NSCLC). We analyzed 120 cases of early-stage NSCLCs (81 squamous cell carcinomas and 39 adenocarcinomas) treated with surgery alone (median follow-up, 63 months; range, 45-74 months). VEGF expression showed a positive association with high vascular grade (microvessel score of >75 per x250 field; P = 0.008), although about half of the LVG cases also expressed VEGF. None of the p53 antibodies examined correlated with angiogenesis. However, wt-p53 expression was inversely associated with VEGF expression, suggesting that wt-p53 is involved in the suppression of the VEGF gene. Combined analysis of VEGF, wt-p53, and microvessel counting showed that, although wt-p53 loss associates with VEGF switch-on, p53 protein may not be involved in the regulation of the angiogenic events downstream of VEGF expression. Moreover, no significant association of bcl-2 and c-erbB-2 oncoprotein expression with VEGF expression was observed. T/N stage, grade, Ki67 proliferation index, and extent of necrosis were not correlated with VEGF expression. Survival analysis showed that VEGF correlated with poor survival (P = 0.04) and was significant in node-negative cases (P = 0.03). We conclude that VEGF is an important angiogenic factor in NSCLC, its expression being dependent on wt-p53 loss.

Aged↗

PubMed1997

Potential role of bcl-2 as a suppressor of tumour angiogenesis in non-small-cell lung cancer.

It has been reported that genes regulating apoptosis may play a role in tumoral angiogenesis. This study examined the relationship between tumour vascularization, a measure of tumour angiogenesis, and bcl-2 and p53 expression in operable non-small-cell lung cancer (NSCLC). The relationship between bcl-2, p53 and tumour vascularization and epidermal-growth-factor-receptor(EGFR) and c-erbB-2 expression was also studied. Tissue sections from resected tumour specimens of 107 NSCLC patients were evaluated immunohistochemically for vascular grade and bcl-2, p53, EGFR and c-erbB-2 expression. bcl-2 expression was found in 20/107 (19%) cases and was associated with squamous-cell histology (p = 0.03). A strong inverse relationship was found between bcl-2 expression and vascular grade (p = 0.005). All c-erbB-2-positive cases were negative for bcl-2 expression (p = 0.01). Overall no association was found between c-erbB-2 expression and vascular grade. However, in bcl-2-negative cases positive c-erbB-2 expression correlated with low angiogenesis (p = 0.05). No relationship was found between p53 and EGFR expression and bcl-2, c-erbB-2 or vascular grade. The improved prognosis reported in bcl-2-positive NSCLC may be related to low tumour vascularization. The results suggest that the anti-apoptotic gene bcl-2 plays a role in regulating tumour angiogenesis. Since normal lung epithelium expresses bcl-2, a sequence of tumour progression involving loss of bcl-2, then activation of c-erbB-2 or increase in tumour vascularization is proposed.

Aged↗

PubMed1997

Endothelial cell-specific expression of tumor necrosis factor-alpha from the KDR or E-selectin promoters following retroviral delivery.

The tumor vasculature offers a target for anti-cancer gene therapy which has the advantages both of good accessibility to systemically delivered therapy and comparative homogeneity across solid tumor types. We aimed to develop retroviruses carrying endothelial-specific promoters for the delivery of genes to proliferating endothelial cells in vitro and to tumor endothelial cells in vivo. This paper reports the generation of such retroviral vectors and the level of expression of murine tumor necrosis factor-alpha (mTNF-alpha) cDNA following infection into endothelial cells and stromal fibroblasts. Retroviral vectors carrying mTNF-alpha have been generated whose expression is controlled either by the retroviral long terminal repeat or by 5' proximal promoter sequences from the endothelial-specific kinase insert domain receptor (KDR)/VEGF receptor and E-Selectin promoters within the context of a self-inactivating (SIN) vector backbone. Both KDR and E-Selectin have been shown to be upregulated on tumor endothelium. A putative polyadenylation sequence AAATAAA within the E-Selectin promoter was mutated to permit faithful transmission of retroviral vectors carrying this promoter. We demonstrate a 10- to 11-fold increase in mTNF-alpha expression from promoter elements within sEND endothelioma cells as compared to NIH-3T3 fibroblasts. Suggestions for further improvements in vector design are discussed.

3T3 Cells↗

PubMed1997

Vascular endothelial growth factor is a predictor of relapse and stage progression in superficial bladder cancer.

Tumor development is angiogenesis dependent, and vascular endothelial growth factor (VEGF) is a key growth factor in this process. We demonstrate that high expression of VEGF mRNA in 55 superficial bladder cancers was associated with earlier recurrence (P = 0.001; hazard ratio, 3.09) and progression to a more invasive phenotype (P = 0.02; hazard ratio, 5.33). VEGF mRNA expression correlated with protein levels in superficial tumors (r = 0.59, P = 0.003) and normal bladder (r = 0.65, P < 0.05), although the ratio of VEGF protein to mRNA was elevated in tumors compared to normal bladder (P = 0.004), suggesting posttranscriptional regulation. In this study, VEGF is implicated as a major downstream mediator of the effects of the p53 tumor suppressor gene by the association between high p53 protein (determined immunochemically) and high VEGF protein and mRNA expression (P < 0.02), although in cases without high p53 protein expression, high VEGF mRNA also predicts a poor prognosis. The relationship between VEGF and early tumor recurrence suggests that seeding via angiogenesis may be a major mechanism in the pathogenesis of recurrence. These studies indicate that VEGF can predict the behavior of superficial bladder tumors and is a therapeutic target for intravesical therapy.

Carcinoma, Transitional Cell↗

PubMed1997

Resistance to diverse drugs and ultraviolet light conferred by overexpression of a novel human 26 S proteasome subunit.

We have investigated the usefulness of the fission yeast Schizosaccharomyces pombe as a model organism for the discovery of novel modes of drug resistance in human cells. In fission yeast, overexpression of the essential pad1(+) gene confers pleiotropic drug resistance through a pathway involving an AP-1 transcription factor encoded by pap1(+). We have identified POH1, a human pad1 homologue that can substitute fully for pad1(+) and induce AP-1-dependent drug resistance in fission yeast. POH1 also confers P-glycoprotein-independent resistance to taxol (paclitaxel), doxorubicin, 7-hydroxystaurosporine, and ultraviolet light when transiently overexpressed in mammalian cells. Poh1 is a previously unidentified component of the human 26 S proteasome, a multiprotein complex that degrades proteins targeted for destruction by the ubiquitin pathway. Hence, Poh1 is part of a conserved mechanism that determines cellular susceptibility to cytotoxic agents, perhaps by influencing the ubiquitin-dependent proteolysis of transcription factors.

Amino Acid Sequence↗

PubMed1997

Expression of Wnt5a is downregulated by extracellular matrix and mutated c-Ha-ras in the human mammary epithelial cell line MCF-10A.

Wnt genes are involved in tumour growth and regulate cell adhesion. Some (Wnt5a and Wnt7b) are more highly expressed in human breast cancer compared to normal tissues. Wnt5a is involved in the regulation of cell movement in Xenopus and is upregulated in several human cancers. Factors regulating Wnt gene expression in human breast epithelium are poorly understood, but c-erbB2 is amplified in many breast cancers and associated with rapid growth and metastasis, as is high expression of c-Ha-ras. To further understand the regulation of Wnt gene expression, this study investigated the effect of proto-oncogenes c-Ha-ras and c-erbB2, and collagen on Wnt mRNA expression, in a normal spontaneously immortalised human mammary epithelial cell line MCF-10A. Out of nine human Wnt genes investigated, Wnt5a and Wnt7b were expressed in the parental cell line, and neomycin-, c-Ha-ras- and c-erbB2-transfected cell lines. The level of Wnt5a mRNA expression was decreased 40-fold and 3-fold when parental cells were grown on collagen and in collagen, respectively. This downregulation correlated with cell branching. However, Wnt7b was not regulated by collagen. In the presence of activated c-Ha-ras, the level of Wnt5a mRNA expression was markedly decreased (> 200-fold) and cell growth rate was elevated. When treated with p21ras inhibitor, BZA-5B, there was a moderate reversal of Wnt5a mRNA expression (2-fold) with a parallel decrease in cell growth. The data indicate that c-Ha-ras is an upstream inhibitory regulator of Wnt5a, and provide further evidence of an inverse relationship between Wnt5a mRNA expression and cell branching. This demonstrates selectivity of regulation of individual members of the Wnt gene family by the ras pathway. Overexpression of c-erbB2 had no effect on Wnt5a or Wnt7b mRNA expression. Thus, extracellular matrix and ras regulate Wnt5a, providing a mechanism for feedback of morphogenetic movements, which is relevant also to cancer biology.

Benzodiazepines↗

PubMed1997

cDNA cloning of a human dishevelled DVL-3 gene, mapping to 3q27, and expression in human breast and colon carcinomas.

dishevelled (Dsh) is a member of the segment polarity gene family in Drosophila which plays an important role in the early developmental patterning processes. A human homologue of Dsh (DVL-1) has recently been described. Here, we report the cloning of a second human homologue of Dsh (called DVL-3) by cDNA library screening. The human DVL-3 gene encodes a predicted 716 amino acid protein which exhibits 98% amino acid identity with mouse Dvl-3 and 49% with Drosophila Dsh. DVL-3 was mapped to 3q27. The expression of DVL-3 mRNA was detected in 30 human cell lines and 2 primary cell cultures. DVL-3 mRNA was detected in normal human breast tissues (n = 4) and tumours (n = 25). Statistically, there was no difference in DVL-3 mRNA level between normal breast tissues and tumours. In human colorectal samples, DVL-3 was expressed equally in matched normal tissues, polyps and tumours. The data indicates that DVL-3 is widely expressed in human cells and supports the notion of a new developmental gene family for dishevelled which may have a widespread role in signal transduction.

Adaptor Proteins, Signal Transducing↗

PubMed1997

Hypoxia-inducible factor-1 modulates gene expression in solid tumors and influences both angiogenesis and tumor growth.

Recent studies of tissue culture cells have defined a widespread system of oxygen-regulated gene expression based on the activation of a heterodimeric transcription factor termed hypoxia-inducible factor-1 (HIF-1). To determine whether the HIF-1 transcriptional response is activated within solid tumors and to define the consequences, we have studied tumor xenografts of a set of hepatoma (Hepa-1) cells that are wild type (wt), deficient (c4), and revertant (Rc4) for an obligatory component of the HIF-1 heterodimer, HIF-1beta. Because HIF-1beta is also essential for the xenobiotic response (in which it is termed the aryl hydrocarbon receptor nuclear translocator), we also studied c31 cells, which have a different defect in the xenobiotic response and form the HIF-1 complex normally. Two genes that show different degrees of HIF-1-dependent hypoxia-inducible expression in cell culture were selected for analysis-the glucose transporter, GLUT3, and vascular endothelial growth factor (VEGF). In situ hybridization showed intense focal induction of gene expression in tumors derived from wt, Rc4, and c31 cells, which was reduced (VEGF) or not seen (GLUT3) in those derived from c4 cells. In association with these changes, tumors of c4 cells had reduced vascularity and grew more slowly. These findings show that HIF-1 activation occurs in hypoxic regions of tumors and demonstrate a major influence on gene expression, tumor angiogenesis, and growth.

Animals↗

PubMed1997

Association of tumor angiogenesis with bone marrow micrometastases in breast cancer patients.

BACKGROUND AND PURPOSE: The microscopic detection of tumor cells (micrometastases) in bone marrow and the extent of blood vessel formation (angiogenesis) in primary tumor specimens are recognized as independent prognostic markers in patients with breast cancer. Since micrometastases occur as a consequence of interaction between the neoplastic cells and the tumor neovasculature, we have examined the relationship between these markers to determine whether the degree of angiogenesis is related to the presence of micrometastases. METHODS: Micrometastases were identified in bone marrow aspirates collected from multiple sites in 214 breast cancer patients prior to surgery (mastectomy or lumpectomy). Tumor cells were detected through an examination of epithelial membrane antigen expression and an analysis of cell morphology. Tumor vascularity was graded semiquantitatively or quantitatively (Chalkley point count) after immunohistochemical staining of the CD31 antigen expressed by the endothelial cells. The reproducibility and accuracy of the vascular grading were validated by use of kappa statistics. Associations between micrometastases and clinicopathologic characteristics, including angiogenesis, were examined using chi-squared and logistic regression techniques. All tests of statistical significance were two-sided. RESULTS: Of the 214 patients, 42 (20%) were positive for bone marrow micrometastases and 75 (35%) had tumors of high vascular grade. There was 86% agreement between vascular grades assessed twice for 35 tumors (kappa statistic = 0.66); for 22 evaluated tumors, there was absolute concordance between vascular grade and Chalkley point count. There were significant positive associations between tumor angiogenesis and micrometastasis (P = .01), tumor grade (P = .003), and estrogen receptor expression (P = .007); however, no significant associations were observed with tumor size (P = .9), lymph node status (P = .33), vascular invasion (peritumoral blood or lymph vessels) (P = .9), menopausal status (P = .17), or age (P = .12). Adjusting for confounding factors, multivariate analysis showed that only tumor angiogenesis (odds ratio = 2.7; P = .016) and vascular invasion (odds ratio = 2.7; P = .012) were significant determinants for the presence of micrometastases. CONCLUSIONS: This study suggests that an assessment of tumor angiogenesis and vascular invasion gives a reliable indication of the likelihood of the presence of bone marrow micrometastases in patients with breast cancer and that both processes contribute to metastases.

Aged↗

PubMed1997

Human apurinic endonuclease 1 expression in a colorectal adenoma-carcinoma sequence.

Human apurinic endonuclease 1 (HAP1) plays a key role in the repair of baseless sites in DNA. HAP1 is also known to be a potent regulator of the binding activity of a number of transcription factors. We have examined the immunohistochemical expression of the HAP1 protein in normal colorectal mucosa, hyperplastic polyps, tubulovillous adenomas, and carcinomas. In normal colonic mucosa, the predominant staining was nuclear in the less differentiated cells located at the lower part of the crypt, but it was cytoplasmic in the more differentiated superficial colonic epithelium. HAP1 expression was nuclear in 3 of 30 adenomas (10%) and 5 of 44 carcinomas (11%), but it was cytoplasmic in 11 of 30 adenomas (37%) and 22 of 44 carcinomas (50%) and both nuclear and cytoplasmic in 16 of 30 adenomas (53%) and 17 of 44 carcinomas (39%). The observed staining in stromal fibroblasts and endothelial cells was nuclear, whereas that in macrophages was cytoplasmic. Our data indicate that HAP1 is expressed in different subcellular compartments during normal differentiation and that this pattern is disrupted in adenomas and carcinomas. The differential localization may be relevant to the two different proposed functions of HAP1.

Adenocarcinoma↗

PubMed1997

Isolation of a full-length human WNT7A gene implicated in limb development and cell transformation, and mapping to chromosome 3p25.

The Wnt gene family has a role in development as well as tumourigenesis. One mouse member, Wnt7a, is vital for limb development in vivo and also possesses transforming ability in vitro. This study reports the isolation of a full length of human homologue of mouse Wnt7a gene by library screening. Yeast artificial chromosome-fluorescence in situ hybridisation (YAC-FISH) mapped the WNT7A gene to chromosome 3p25. Human WNT7A had an ORF encoding a deduced protein of 349 aa that exhibited 97% and 92% identity to mouse Wnt7a at the aa and nucleic acid levels, respectively. It possessed the 22 conserved cysteine residues and 3 more at the amino terminus, and a putative poly A tail. This is the fifth human WNT gene in which a complete cDNA sequence had been determined.

Amino Acid Sequence↗

PubMed1997

A reliable external control for ribonuclease protection assays.

A method is described for generating an external spiked human RNA control to enhance the reliability of assessment of gene expression in tumour extracts. Spiking with an external standard RNA controls for all subsequent steps of analysis on a lane by lane basis and allows for uniform comparison of the gene of interest as a fraction of total RNA, particularly when multiple samples are not available. The antisense probe that is being used to detect endogenous gene expression is also used as an external control. A sense riboprobe is made from the same vector. Because of the flanking RNA polymerase sites incorporated in both probes, hybridization with the sense riboprobe at a much lower concentration than the antisense probe generates a larger product that can be readily separated from the endogenous protected fragment. This method is generally applicable to any riboprobe that has a T3 and T7 RNA polymerase site and allows any externally added riboprobe use for assessing endogenous gene expression to be used as the external spike control.

DNA-Directed RNA Polymerases↗

PubMed1997

A novel human Wnt gene, WNT10B, maps to 12q13 and is expressed in human breast carcinomas.

Several members of the Wnt gene family have been shown to cause mammary tumors in mouse. Using degenerate primer polymerase chain reaction (PCR) on human genomic DNA, and specific PCR of cDNA libraries, we have isolated a WNT gene which has not previously been described in human. The gene is the human homologue of mouse Wnt10b, recently shown to be one of the oncogenes cooperating with FGF3 in the development of mouse mammary tumour virus (MMTV) induced mouse mammary carcinomas. The human WNT10B sequence was 88% and 95% identical to the murine gene at nucleotide and amino acid levels, respectively. YAC FISH mapping localises the gene to 12q13, a chromosomal region frequently rearranged in human tumours and also containing the WNT1 gene. In normal and benign proliferations of human breast tissue, WNT10B expression was not detected by ribonuclease protection assays but was found at low levels in RT-PCR experiments. In contrast, using both methods, WNT10B expression was found to be elevated in 3 of 50 primary breast carcinomas. Southern blot analysis of the carcinoma expressing the highest levels of WNT10B showed no amplification or rearrangement of the gene. The WNT10B gene was also expressed in some cancer and non cancerous breast cell lines. These findings suggest that the WNT10B gene may be involved in human breast cancer, and show that there is differential expression of the WNT10B gene in benign and malignant disease.

Amino Acid Sequence↗

PubMed1997

Expression of the angiogenic factors vascular endothelial cell growth factor, acidic and basic fibroblast growth factor, tumor growth factor beta-1, platelet-derived endothelial cell growth factor, placenta growth factor, and pleiotrophin in human primary breast cancer and its relation to angiogenesis.

Angiogenesis is a significant prognostic factor in breast cancer, but the factors that control angiogenesis in vivo are not well defined. Multiple angiogenic polypeptides are known, and we have determined the expression of seven of these in primary human breast cancers; the relationship of expression to estrogen receptor and vascular density was also examined. Vascular endothelial growth factor (VEGF) and its four isoforms (121, 165, 189, and 206 amino acids), transforming growth factor (TGF)-beta1, pleiotrophin, acidic and basic fibroblast growth factor (FGF), placental growth factor, and thymidine phosphorylase (platelet-derived endothelial cell growth factor) were quantitated by RNase protection analysis. beta-FGF was also measured by ELISA. The estrogen receptor (ER), epidermal growth factor receptor, and vascular density were analyzed in 64 primary breast cancers. All tumors expressed at least six different vascular growth factors. VEGF was most abundant, and the transcript for the 121-amino acid form predominated. Other angiogenic factors expressed at high levels were thymidine phosphorylase and TGF-beta1. Expression of most of the angiogenic factors did not correlate with that of ER or vascular density. However, thymidine phosphorylase did, with a correlation coefficient of 0.3 (P = 0.03). There were significant associations of pleiotrophin with acidic FGF expression (P = 0.001) and TGF-beta with platelet-derived endothelial cell growth factor expression (P = 0.001). Thus, angiogenesis may involve a coordinate regulation of some vascular growth factors. High VEGF expression correlated with poor prognosis in univariate analysis (P = 0.03), as did ER and epidermal growth factor receptor expression. Basic FGF was also assessed by ELISA and was more highly expressed in tumors than normal breast tissues (median, 346 microg/ml cytosol; range, 54-1323 versus median, 149; range, 32-509; P = 0.01). Implications for therapy are that broad spectrum agents that block features common to these factors may be useful (e.g., antagonism of heparin-binding activity agents), because so many angiogenic factors are expressed. Inhibiting endothelial migration or agents directly toxic to endothelium would be of value in a combined approach to therapy.

Breast Neoplasms↗

PubMed1997

The influence of oxygen tension and pH on the expression of platelet-derived endothelial cell growth factor/thymidine phosphorylase in human breast tumor cells grown in vitro and in vivo.

We report that hypoxia regulates and influences the level of the angiogenic enzyme platelet-derived endothelial cell growth factor (PD-ECGF), also called thymidine phosphorylase, in vitro and in vivo. Levels of PD-ECGF protein increased 6-fold in the breast cancer cell line MDA 231 after 16 h of growth in 0.3% oxygen. A simultaneous increase in enzyme activity was observed. Immunohistochemical staining of MDA 231 tumors grown in nu/nu mice showed increased expression of PD-ECGF in those parts of the tumor that are proximal to the areas of necrosis. In addition, increased and widespread staining for PD-ECGF protein was obtained when the tumor vascular supply was occluded for 2 h by clamping. Lowering the media pH to 6.3-6.7 in vitro also resulted in an increase in PD-ECGF protein levels. This study demonstrates that tumor microenvironmental factors can result in the specific up-regulation of an angiogenic enzyme that can also activate 5-fluorouracil prodrugs and hence is exploitable therapeutically.

Animals↗