PubMed Health⌕ Search

Biomedical subjects

Oliver Stoeltzing

Publications and source records attributed to Oliver Stoeltzing.

At least 19 recordsLinked to original sources
PubMed2007

Mammalian target of rapamycin is activated in human gastric cancer and serves as a target for therapy in an experimental model.

The mammalian target of rapamycin (mTOR) has become an interesting target for cancer therapy through its influence on oncogenic signals, which involve phosphatidylinositol-3-kinase and hypoxia-inducible factor-1alpha (HIF-1alpha). Since mTOR is an upstream regulator of HIF-1alpha, a key mediator of gastric cancer growth and angiogenesis, we investigated mTOR activation in human gastric adenocarcinoma specimens and determined whether rapamycin could inhibit gastric cancer growth in mice. Expression of phospho-mTOR was assessed by immunohistochemical analyses of human tissues. For in vitro studies, human gastric cancer cell lines were used to determine S6K1, 4E-BP-1 and HIF-1alpha activation and cancer cell motility upon rapamycin treatment. Effects of rapamycin on tumor growth and angiogenesis in vivo were assessed in both a subcutaneous tumor model and in an experimental model with orthotopically grown tumors. Mice received either rapamycin (0.5 mg/kg/day or 1.5 mg/kg/day) or diluent per intra-peritoneal injections. In addition, antiangiogenic effects were monitored in vivo using a dorsal-skin-fold chamber model. Immunohistochemical analyses showed strong expression of phospho-mTOR in 60% of intestinal- and 64% of diffuse-type human gastric adenocarcinomas. In vitro, rapamycin-treatment effectively blocked S6K1, 4E-BP-1 and HIF-1alpha activation, and significantly impaired tumor cell migration. In vivo, rapamycin-treatment led to significant inhibition of subcutaneous tumor growth, decreased CD31-positive vessel area and reduced tumor cell proliferation. Similar significant results were obtained in an orthotopic model of gastric cancer. In the dorsal-skin-fold chamber model, rapamycin-treatment significantly inhibited tumor vascularization in vivo. In conclusion, mTOR is frequently activated in human gastric cancer and represents a promising new molecular target for therapy.

Adenocarcinoma↗
PubMed2007

Sirolimus promotes tolerance for donor and recipient antigens after MHC class II disparate bone marrow transplantation in rats.

OBJECTIVE: Mixed chimerism after allogeneic bone marrow transplantation (BMT) promotes immunologic tolerance. Graft-vs-host disease (GvHD) can occur when immunosuppressive control of the graft fails. Here we evaluate the influence of concurrent immunosuppression after irradiation-based induction therapy on development of tolerance and GvHD. METHODS: Conditioning was performed by different doses of total body irradiation (TBI) in a major histocompatibility complex (MHC) class II disparate rat BMT model. Animals received subsequent immunosuppression with either cyclosporine A (CsA) or sirolimus. Nonresponsiveness toward donor and recipient antigens was demonstrated by development of mixed chimerism and/or GvHD. RESULTS: Administration of 10 Gy of TBI prior to BMT alone was associated with severe GvHD. Induction therapy with 8 Gy of TBI alone led to graft rejection in the long-term. Two weeks of immunosuppression with CsA after 8 Gy of TBI resulted in transient chimerism, but was finally associated with a combination of fatal GvHD and graft rejection. Six gray of TBI with CsA treatment for 14 or 28 days caused only mild GvHD, but did not lead to stable chimerism. In contrast, treatment with sirolimus was associated with stable chimerism after 8 Gy of TBI (14-day course) and 6 Gy of TBI (28-day course) accompanied by a low incidence of GvHD. CONCLUSIONS: In contrast to CsA, sirolimus facilitates development of tolerance after MHC class II disparate BMT and irradiation-based conditioning, with a low risk of GvHD. Therefore, sirolimus has promising characteristics for inclusion in immunosuppressive protocols.

Animals↗
PubMed2006

No contribution of multipotent mesenchymal stromal cells to liver regeneration in a rat model of prolonged hepatic injury.

Multipotent mesenchymal stromal (MS) cells from adult bone marrow are a cell population that can be expanded to large numbers in culture. MS cells might be differentiated toward hepatocytes in vitro and thus are promising candidates for therapeutic applications in vivo. The efficacy of bone marrow-derived MS cells versus hepatocytes to contribute to liver regeneration was compared in a rat model of prolonged toxic hepatic injury. Liver damage was induced by injection of carbon tetrachloride (CCl(4)) or allyl alcohol (AA) with and without retrorsine (R) pretreatment. MS cells or hepatocytes of wild-type F344 rats were injected into dipeptidyl peptidase IV (DPPIV)-deficient syngeneic rats. Hepatocyte chimerism was higher after intraportal hepatocyte transplantation in the R/AA group (mean maximal cluster size [MCS] = 21 cells) compared with the R/CCl(4) treatment group (MCS = 18). No hepatocyte engraftment was outlined following post-transplant CCl(4) injection only, whereas mere AA injection resulted in small clusters of donor-derived hepatocytes (MCS = 2). Intraparenchymal injection of hepatocytes was associated with a MCS = 11 after R/AA treatment and a MCS = 6 after AA administration alone. Redistribution of MS cells to the liver was shown after intraportal and intraparenchymal injection. In contrast to hepatocyte transplantation, however, donor-derived DPPIV-positive cells could not be demonstrated in any recipient after MS cell transplantation. Data from the present study indicate that a well-defined population of MS cells obtained according to established standard protocols does not differentiate into hepatocytes in vivo when transplanted under regenerative conditions, in which the application of hepatocytes results in stable hepatic engraftment.

Animals↗
PubMed2006

Intracellular signaling in tumor and endothelial cells: The expected and, yet again, the unexpected.

In this issue of Cancer Cell, Phung and coworkers demonstrate that sustained endothelial activation of Akt by expression of constitutively activated Akt1 (myrAkt1) leads to blood vessels that essentially recapitulate the complex structural and functional abnormalities of tumor vessels. The authors provide evidence that rapamycin inhibition of PI3K/Akt/mTOR signaling in endothelial cells (ECs), by either reducing Akt activity or blocking mTOR, reverses the pathologic effects associated with excess VEGF signaling in the tumor vasculature. However, unexpected findings following mTOR inhibition in vivo highlight the seemingly paradoxical and complex effects of rapamycin on various cell types within the tumor microenvironment.

Antibiotics, Antineoplastic↗
PubMed2005

Upregulation of neuropilin-1 by basic fibroblast growth factor enhances vascular smooth muscle cell migration in response to VEGF.

Neuropilin-1 (NRP-1) is a co-receptor for vascular endothelial growth factor (VEGF). During neovascularization, vascular smooth muscle cells (VSMCs) and pericytes modulate the function of endothelial cells. Factors that mediate NRP-1 in human VSMCs (hVSMCs) remain to be elucidated. We studied various angiogenic cytokines to identify factors that increase NRP-1 expression in hVSMCs. Treatment of hVSMCs with basic fibroblast growth factor (b-FGF) induced expressions of NRP-1 mRNA and protein whereas epidermal growth factor, insulin-like growth factor-1, and interleukin-1beta did not. b-FGF induced phosphorylation of Erk-1/2 and JNK. MEK1/2 and nuclear factor kappa B (NF-kappaB) inhibitors (U0126 and TLCK, respectively) blocked the ability of b-FGF to induce NRP-1 mRNA expression, but inhibition of JNK (SP600125) or PI3-kinase activity (wortmannin) did not. Further, the increase in NRP-1 expression by b-FGF enhanced hVSMCs migration in response to VEGF(165). This effect was dependent on the binding of VEGF(165) to VEGFR-2, as blocking antibodies to VEGFR-2, but not VEGFR-1, inhibited VEGF(165)-induced migration. In conclusion, b-FGF increased NRP-1 expression in hVSMCs that in turn enhance the effect of VEGF(165) on cell migration. The enhanced migration of hVSMCs was mediated through binding of VEGF(165) to both NRP-1 and VEGFR-2, as inhibition of VEGFR-2 on these cells blocked the effect of VEGF-mediated cell migration.

Cell Movement↗
PubMed2004

Role of hypoxia-inducible factor 1alpha in gastric cancer cell growth, angiogenesis, and vessel maturation.

BACKGROUND: Hypoxia-inducible factor 1 (HIF-1), a heterodimer comprising the oxygen-regulated subunit, HIF-1alpha, and HIF-1beta, mediates transcription of the gene for vascular endothelial growth factor (VEGF). Overexpression of HIF-1alpha is associated with tumor angiogenesis and tumor cell proliferation and invasion. We examined the effects of inhibiting HIF-1alpha activity on angiogenesis and human gastric cancer growth in vivo. METHODS: Human gastric cancer TMK-1 cells were stably transfected with pHIF-1alphaDN, an expression plasmid encoding a dominant-negative form of HIF-1alpha that dimerizes with endogenous HIF-1beta to produce HIF-1 complexes that cannot activate transcription, or with the empty expression vector (pCEP4). Two clones of pHIF-1alphaDN-transfected cells, DN2 and DN3, were tested in all experiments. We used an enzyme-linked immunosorbent assay to measure VEGF secretion by transfected cells cultured in hypoxic (1% O2) or nonhypoxic (20% O2) conditions. We used subcutaneous and orthotopic mouse tumor models to examine the growth of tumors derived from injected pHIF-1alphaDN-or pCEP4-transfected cells. Tumor cell proliferation, vessel area (a measure of functional vascular volume), and tumor endothelial cell association with pericyte-like cells (a measure of vessel maturation) were analyzed by immunohistochemical or immunofluorescent staining. All statistical tests were two-sided. RESULTS: DN2 cells and DN3 cells secreted less VEGF than pCEP4-transfected TMK-1 cells when cultured in nonhypoxic or hypoxic conditions (e.g., DN2 versus pCEP4 in nonhypoxic conditions: 645 pg of VEGF/10(6) cells versus 1591 pg of VEGF/10(6) cells, difference = 946 pg of VEGF/10(6) cells [95% confidence interval [CI] = 640 to 1251 pg of VEGF/10(6) cells; P =.006]; DN2 versus pCEP4 in hypoxic conditions: 785 pg of VEGF/10(6) cells versus 2807 pg of VEGF/10(6) cells, difference = 2022 pg of VEGF/10(6) cells [95% CI = 1871 to 2152 pg of VEGF/10(6) cells; P<.001]). In the subcutaneous tumor model, tumors derived from DN2 or DN3 cells had lower final volumes, weights, and vessel areas, less tumor endothelial cell association with desmin-positive cells, and fewer proliferating tumor cells than tumors derived from pCEP4-transfected cells. In the orthotopic tumor model, tumors derived from DN2 cells had smaller volumes and less vessel area and maturation than tumors derived from pCEP4-transfected cells. CONCLUSIONS: Inhibition of HIF-1alpha activity impairs gastric tumor growth, angiogenesis, and vessel maturation.

Animals↗
PubMed2004

Interleukin-1beta regulates angiopoietin-1 expression in human endothelial cells.

Angiopoietin (Ang)-1 is an important regulator of endothelial cell (EC) survival and stabilization. Ang-1 exerts its biological effects by binding to the EC-specific tyrosine kinase receptor Tie-2, and initiates intracellular signaling in ECs. However, regulatory mechanisms for endothelial Ang-1 expression have not been completely elucidated. In this study, we investigated the effects of angiogenic cytokines and growth factors on Ang-1 expression in human umbilical vein ECs (HUVECs). Northern blot analysis was performed after HUVECs were exposed to interleukin-1beta (IL-1beta), tumor necrosis factor-alpha, platelet-derived growth factor-BB, insulin-like growth factor-1, or vascular endothelial growth factor (VEGF). Both IL-1beta and tumor necrosis factor-alpha caused marked down-regulation of Ang-1 mRNA levels at 4 h with a further decrease observed at 24 h. Using signaling inhibitors, we identified the P38 pathway as the pathway that mediates IL-1beta down-regulation of Ang-1. Furthermore, treatment of cells with IL-1beta indirectly (via down-regulation of Ang-1) led to a decrease in Tie-2 autophosphorylation levels in HUVECs. We previously demonstrated that IL-1beta regulates VEGF expression in tumor cells. This observation was confirmed in ECs in the present study. Because pericytes play a role in regulating EC function, we also determined whether IL-1beta would also down-regulate Ang-1 in human vascular smooth muscle cells. Similar to our findings in HUVECs, we found that IL-1beta decreased Ang-1 expression in human vascular smooth muscle cells. Direct effects of IL-1beta on angiogenesis were investigated by use of an in vivo Gelfoam angiogenesis assay in which IL-1beta produced a significant increase in vessel counts (P = 0.0189). These results suggest that IL-1beta indirectly regulates angiogenesis by modulating the expression of Ang-1. IL-1beta may trigger a proangiogenic response by decreasing Ang-1 levels in ECs and pericytes and up-regulating VEGF in ECs and tumor cells.

Angiopoietin-1↗
PubMed2004

Activator protein 2alpha inhibits tumorigenicity and represses vascular endothelial growth factor transcription in prostate cancer cells.

Activator protein-2alpha (AP-2) is a transcription factor that regulates proliferation and differentiation in mammalian cells. We have shown previously that although AP-2 is expressed highly in normal prostatic epithelium, its expression is lost in high-grade prostatic intraepithelial neoplasia and prostate cancer, suggesting that loss of AP-2 plays a role in prostate cancer development. We demonstrate that forced AP-2 expression in the prostate cancer cell line LNCaP-LN3 (AP-2 negative) inhibited dramatically tumor incidence in nude mice. To identify the genes that might have been responsible for this effect, we used microchip expression array. We found several genes known to be involved in malignancy were deregulated, including the vascular endothelial growth factor (VEGF) gene. Because VEGF was down-regulated by 14.7-fold in the AP-2-transfected cells and because it is a major angiogenic factor in prostate cancer development and progression, we chose to examine the AP-2-VEGF interaction. Our evidence suggests that AP-2 repressed transcriptionally the VEGF promoter by competing with the transcriptional activator Sp3. Loss of AP-2 in prostate cancer cells reduced the AP-2:Sp3 ratio and activated VEGF expression. AP-2 acts as a tumor-suppressor gene in prostate cancer. Elucidating the molecular events resulting from loss of AP-2 in the prostate epithelium has implications for the understanding and prevention of the onset of prostate cancer.

Animals↗
PubMed2004

Neuropilin-1 in human colon cancer: expression, regulation, and role in induction of angiogenesis.

Neuropilin-1 (NRP-1), a recently identified co-receptor for vascular endothelial growth factor, is expressed by several nongastrointestinal tumor types and enhances prostate cancer angiogenesis and growth in preclinical models. We investigated the expression and regulation of NRP-1 and the effect of NRP-1 overexpression on angiogenesis and growth of human colon adenocarcinoma by immunohistochemistry and in situ hybridization. NRP-1 was expressed in 20 of 20 human colon adenocarcinoma specimens but not in the adjacent nonmalignant colonic mucosa. By reverse transcriptase-polymerase chain reaction analysis, NRP-1 mRNA was expressed in seven of seven colon adenocarcinoma cell lines. Subcutaneous xenografts of stably transfected KM12SM/LM2 human colon cancer cells overexpressing NRP-1 led to increased tumor growth and angiogenesis in nude mice. In in vitro assays, conditioned medium from NRP-1-transfected cell lines led to an increase in endothelial cell migration, but did not affect endothelial cell growth. Epidermal growth factor (EGF) led to induction of NRP-1 in human colon adenocarcinoma cells and selective blockade of the epidermal growth factor receptor (EGFR) decreased constitutive and EGF-induced NRP-1 expression. Blockade of the Erk 1/2 and P38 mitogen-activated protein kinase signaling pathways also led to a decrease in constitutive and EGF-induced NRP-1 expression. These findings demonstrate the ubiquitous expression of NRP-1 in human colon cancer and suggest that NRP-1 may contribute to colon cancer angiogenesis and growth. This study also suggests that EGF and mitogen-activated protein kinase signaling pathways play an important role in NRP-1 regulation in colon cancer cells.

Adenocarcinoma↗
PubMed2004

ZD6474, a vascular endothelial growth factor receptor tyrosine kinase inhibitor with additional activity against epidermal growth factor receptor tyrosine kinase, inhibits orthotopic growth and angiogenesis of gastric cancer.

Vascular endothelial growth factor (VEGF) and epidermal growth factor (EGF) have been strongly implicated in the growth and metastasis of gastric cancer. The purpose of this study was to examine the effects of ZD6474, an inhibitor of inhibitor of VEGF receptor (VEGFR) tyrosine kinase with additional activity against EGF receptor (EGFR), on tumor growth and angiogenesis in an orthotopic model of gastric cancer. In vitro, ZD6474 inhibited human umbilical vascular endothelial cell and TMK-1 human gastric tumor cell proliferation in a dose-dependent fashion. EGF-mediated activation of EGFR and Erk-1/2 was decreased in tumor cells after ZD6474 treatment. In addition, VEGF-mediated activation of VEGFR2 and Erk-1/2 was decreased in human umbilical vascular endothelial cells. TMK-1 human gastric adenocarcinoma cells were injected into the gastric wall of nude mice. ZD6474 therapy was initiated on day 10. Mice (n = 14 per group) were treated p.o. with (a) 1% Tween 80 (control), (b) 50 mg/kg/d ZD6474, or (c) 100 mg/kg/d ZD6474. Mice were sacrificed on day 33. Tumors from each group were stained for markers of blood vessels, pericytes, proliferation, and apoptosis. ZD6474 at both 50 and 100 mg/kg/d led to marked inhibition of tumor growth (P < 0.05). ZD6474 reduced tumor cell proliferation by 48% in the 50 mg/kg/d group and 65% in the 100 mg/kg/d group (P < 0.03) and increased tumor cell apoptosis (P < 0.001) in vivo. ZD6474 led to a 69% decrease in microvessel density in the 50 mg/kg/d group (P < 0.001) and a 62% decrease in the 100 mg/kg/d group (P < 0.001). Although microvessel density was decreased by ZD6474, the remaining vessels showed a relatively higher percentage of pericyte coverage (3-fold increase; P < 0.001), perhaps reflecting selective loss of uncovered vessels in the ZD6474 group. In conclusion, therapies such as ZD6474 that target two distinct aspects of tumor growth, angiogenesis and tumor cell proliferation, warrant further investigation.

Angiogenesis Inhibitors↗
PubMed2004

Vascular endothelial growth factor receptors: expression and function in solid tumors.

Vascular endothelial growth factor (VEGF) and its family members are important mediators of tumor angiogenesis. The multiple functions of the VEGF are mediated through complex and selective interactions between the ligands, their high-affinity tyrosine kinase receptors, and co-receptors (neuropilins). While these receptors are historically described as being exclusively expressed on endothelial cells, emerging evidence has documented expression of these receptors on a number of nonendothelial cells, including tumor cells. The VEGF receptors (VEGFR) have also been shown to be functional in a number of nonendothelial systems, where they may be targets for anti-VEGF therapy. This article will review the basic effects and interactions of the VEGFRs on endothelial cells and the evidence for their expression and function on tumor cells. The novel expression of VEGFRs on tumor cells contributes to the understanding of the complex roles of VEGF within the tumor microenvironment, potentially affecting both endothelial cells and tumor cells expressing the VEGFRs. This elucidation of VEGF activity may further refine antineoplastic regimens for solid malignancies.

Angiogenesis Inhibitors↗
PubMed2003

Expression and regulation of the novel vascular endothelial growth factor receptor neuropilin-1 by epidermal growth factor in human pancreatic carcinoma.

BACKGROUND: It was recently shown that neuropilin-1 (NRP-1), which was described originally as a receptor for the semaphorins/collapsins (ligands involved in neuronal guidance), is a coreceptor for vascular endothelial growth factor (VEGF) and increases the affinity of specific isoforms of VEGF to its receptor, VEGF-R2. METHODS: The authors investigated the expression and regulation of NRP-1 in human pancreatic adenocarcinoma specimens and cell lines. RESULTS: Immunohistochemical analysis revealed that NRP-1 was expressed in 12 of 12 human pancreatic adenocarcinoma specimens but was absent in nonmalignant pancreatic tissue. Northern blot analysis revealed NRP-1 mRNA expression in 8 of 11 human pancreatic adenocarcinoma cell lines. NRP-1 mRNA expression was increased by epidermal growth factor (EGF) but not by tumor necrosis factor alpha in several of the human pancreatic adenocarcinoma cell lines studied. Treating human Panc-48 adenocarcinoma cells with EGF activated Akt and Erk but not P-38. Blockade of the phosphatidylinositol-3 kinase (PI-3K)/Akt, mitogen-activated protein kinase (MAPK)/Erk, or P-38 pathways abrogated EGF-induced NRP-1 expression. Finally, EGF receptor blockade in vivo led to a decrease in NRP-1 expression in an orthotopic model of human pancreatic carcinoma. CONCLUSIONS: NRP-1 is expressed in most human pancreatic adenocarcinomas and cell lines but not in nonmalignant pancreatic tissue. EGF regulates NRP-1 expression through the PI-3K/Akt and MAPK/Erk signaling pathways, and blockade of the EGF receptor is associated with decreased expression of NRP-1 in vivo. NRP-1 may act as a coreceptor for VEGF in pancreatic carcinoma, as it does in other tumor systems, thereby enhancing angiogenesis and the effect of VEGF on the growth of pancreatic adenocarcinoma.

Adenocarcinoma↗
PubMed2003

Cyclooxygenase-2 is up-regulated by interleukin-1 beta in human colorectal cancer cells via multiple signaling pathways.

Overexpression of cyclooxygenase-2 (COX-2) has been observed in human colorectal cancer. COX-2 expression in human tumors can be induced by growth factors, cytokines, oncogenes, and other factors. The mechanisms regulating COX-2 expression in human colon cancer have not been completely elucidated. We hypothesized that the proinflammatory cytokine interleukin-1 beta (IL-1 beta) mediates COX-2 expression in HT-29 human colon cancer cells. Treatment of HT-29 cells with IL-1 beta induced expression of COX-2 mRNA and protein in a time- and dose-dependent manner. Inhibitors of the extracellular signal-regulated kinase 1/2, c-Jun NH(2)-terminal kinase, P38 mitogen-activated protein kinase, and nuclear factor-kappa B (NF-kappa B) signaling pathways blocked the ability of IL-1 beta to induce COX-2 mRNA. In contrast, Wortmannin, a phosphoinositide 3-kinase inhibitor upstream of protein kinase B/Akt, led to a slight increase in COX-2 mRNA expression after IL-1 beta treatment. Electrophoretic mobility shift assay on nuclear extracts demonstrated that IL-1 beta induced NF-kappa B DNA binding activity in HT-29 cells, and the activated NF-kappa B complex was eliminated after treatment with an inhibitor of NF-kappa B. Supershift assay indicated that the two NF-kappa B subunits, p65 and p50, were involved in activation of NF-kappa B complex by IL-1 beta stimulation. The stability of COX-2 mRNA was not altered by IL-1 beta treatment. These data demonstrate that IL-1 beta induces COX-2 expression in HT-29 cells through multiple signaling pathways and NF-kappa B.

Colonic Neoplasms↗
PubMed2003

Angiopoietin-1 inhibits vascular permeability, angiogenesis, and growth of hepatic colon cancer tumors.

Angiopoietin (Ang)-1 and -2 are critical regulators of embryonic and postnatal neovascularization. Ang-1 activates the endothelial cell-specific tyrosine kinase receptor Tie-2, which in turn leads to enhanced endothelial cell survival and stabilization. The effects of Ang-1 on tumor angiogenesis remain controversial; although we have previously demonstrated that Ang-1 overexpression in colon cancer cells leads to a decrease in s.c. tumor growth, others have shown that Ang-1 may be proangiogenic. Few studies have addressed the role of the Angs in tumors growing in the organ of metastatic growth. We hypothesized that overexpression of Ang-1 may inhibit the growth of colon cancers growing in the liver by inhibition of angiogenesis. We also wanted to investigate the mechanisms by which Ang-1 affects angiogenesis in vivo. Human colon cancer cells (HT29) were stably transfected with an Ang-1 construct or an empty vector (pcDNA) and injected directly into the livers of nude mice. After 37 days, livers were harvested and weighed, and tumor sizes were measured. In an additional experiment, to validate the paracrine effect of Ang-1, various mixtures of control cells and Ang-1-transfected cells were injected into livers, and tumor growth was assessed. Direct effects of recombinant Ang-1 on angiogenesis were studied with an in vivo Gelfoam angiogenesis assay. The impact of Ang-1 on vascular permeability was investigated using an intradermal Miles assay with conditioned media from transfected cells. Liver weights (P < 0.05), tumor volumes (P < 0.05), vessel counts (P < 0.01), and tumor cell proliferation (P < 0.01) in the Ang-1 group were significantly lower than those in the control (pcDNA) group. Tumor vessels in the Ang-1 group developed a significantly higher degree of pericyte coverage (P < 0.02) than vessels in pcDNA tumors. In the cell mixture experiment, even as few as a 1:10 mixture of Ang-1-transfected cells/control cells resulted in a significant reduction of hepatic tumor volumes (P < 0.04). In the angiogenesis assay, vessel counts in Gelfoam implants were significantly decreased by the addition of Ang-1 (P < 0.01). Finally, conditioned medium from Ang-1-transfected cells decreased vascular permeability more than that from control cells (P < 0.05). Our results suggest that Ang-1 is an important regulator of angiogenesis and vascular permeability and that this effect may be secondary to increasing periendothelial support and vessel stabilization. Thus, Ang-1 could potentially serve as an antineoplastic or anti-permeability agent for patients with metastatic colorectal cancer.

Angiogenesis Inducing Agents↗
PubMed2003

Down-regulation of c-Met inhibits growth in the liver of human colorectal carcinoma cells.

Overexpression of c-Met, the protein tyrosine kinase receptor for the hepatocyte growth factor/scatter factor, has been implicated in the progression and metastasis of human colorectal carcinoma. To examine the role of c-Met on in vitro and in vivo growth of human colon tumor cell lines, stable subclones of the high metastatic human colorectal carcinoma cell line, KM20, isolated from a Dukes' D patient, with reduced c-Met expression were obtained after transfection with a c-Met-specific targeting ribozyme. The subclones were only modestly reduced in c-Met expression because of c-Met playing an important role in cellular survival. However, a 60-90% reduction in basal c-Met autophosphorylation and kinase activity were observed. Correlating with the reduction in c-Met kinase activity, subclones with reduced c-Met expression had significantly reduced in vitro growth rates and soft-agar colony-forming abilities. The in vivo growth of these cells was examined at both the ectopic SQ site and the orthotopic site of metastatic growth, the liver. SQ growth was delayed significantly in the c-Met down-regulated clones compared with controls, with tumors growing on loss of the ribozyme construct. In contrast, tumor incidence was significantly reduced when the c-Met down-regulated cells were grown in the orthotopic liver site. Thus, c-Met activation may be important in metastatic growth of colon tumor cells in the liver. Collectively these data demonstrate that a small reduction in c-Met protein levels leads to profound biological effects, and potential c-Met inhibitors may be of therapeutic value in treatment of colon cancer.

Adenoviridae↗
PubMed2003

Alphavbeta3 integrin antagonist S247 decreases colon cancer metastasis and angiogenesis and improves survival in mice.

Members of the integrin family influence several aspects of tumor progression and metastasis, including cell survival, proliferation, and angiogenesis. Specific integrins such as alpha(v)beta(3) and alpha(v)beta(5) are involved in regulating endothelial cell function, and thus angiogenesis. We evaluated the effect of the alpha(v)beta(3)/alpha(v)beta(5) integrin antagonist S247 on the growth and angiogenesis of colon cancer liver metastases in an orthotopic murine model. Murine colon cancer cells were injected into the spleens of BALB/c mice to produce liver metastases. On day 7, miniature osmotic pumps were implanted into the subcutis to continuously infuse either saline or 70 mg/kg/day S247. All mice were sacrificed when control mice became moribund. Mice that received S247 developed significantly fewer liver metastases than did controls (P < 0.05). Using the same model, a subsequent survival study was performed. Mice were sacrificed when moribund as determined by an observer blinded to the treatment given. Treatment with S247 significantly prolonged overall survival (P < 0.05). Interestingly, primary tumors in the spleen were the cause of death in the S247-treated group as S247 appeared to have little effect on these tumors. Immunohistochemical staining demonstrated a significant reduction of vessels in liver metastases of S247-treated mice (P < 0.001), a significant increase in endothelial cell apoptosis (P < 0.05), and a significant decrease in pericyte coverage (P < 0.0001). To determine the role of S247 on angiogenesis, we examined the effect of S247 in vitro on human umbilical vein endothelial cells (HUVECs) and human vascular smooth muscle cells (hVSMCs). The addition of S247 to HUVECs and hVSMCs growing on vitronectin-coated flasks and in Matrigel significantly impaired cell growth and colony formation, respectively (P < 0.05). Furthermore, S247 completely inhibited the attachment of HUVECs and hVSMCs and increased apoptosis by six- to 9fold compared with controls. In in vitro invasion assays, S247-treated cells demonstrated decreased migration (P < 0.05). In conclusion, S247 demonstrated significant antimetastatic and antiangiogenic activity and impaired both endothelial and hVSMC/pericyte function in vitro and in vivo. The use of agents such as integrin antagonists that target multiple cell types involved in angiogenesis may be a more effective method of inhibiting angiogenesis than agents targeting only the endothelial cells.

Angiogenesis Inhibitors↗
PubMed2003

Inhibition of integrin alpha5beta1 function with a small peptide (ATN-161) plus continuous 5-FU infusion reduces colorectal liver metastases and improves survival in mice.

Integrin alpha(5)beta(1) is expressed on activated endothelial cells and plays a critical role in tumor angiogenesis. We hypothesized that a novel integrin alpha(5)beta(1) antagonist, ATN-161, would inhibit angiogenesis and growth of liver metastases in a murine model. We further hypothesized that combining ATN-161 with 5-fluorouracil (5-FU) chemotherapy would enhance the antineoplastic effect. Murine colon cancer cells (CT26) were injected into spleens of BALB/c mice to produce liver metastases. Four days thereafter, mice were given either ATN-161 (100 mg/kg, every 3rd day) or saline by intraperitoneal injection, with or without combination of continuous-infusion 5-FU (100 mg/kg/2 weeks), which was started on day 7. On day 20 after tumor cell inoculation, mice were killed and liver weights and number of liver metastases were determined. A follow-up study on survival was also conducted in which mice were randomized to receive ATN-161, 5-FU or ATN-161+5-FU. Combination therapy with ATN-161+5-FU significantly reduced tumor burden (liver weight) and number of liver metastases (p<0.02). Liver tumors in the ATN-161 and ATN-161+5-FU groups had significantly fewer microvessels (p<0.05) than tumors in the control or 5-FU-treated groups. Unlike treatment with either agent alone, ATN-161+5-FU significantly increased tumor cell apoptosis and decreased tumor cell proliferation (p<0.03) and improved overall survival (p<0.03, log-rank test). Targeting integrin alpha(5)beta(1) in combination with 5-FU infusion reduced liver metastases formation and improved survival in this colon cancer model. The enhancement of antineoplastic activity from the combination of anti-angiogenic therapy and chemotherapy may be a promising approach for treating metastatic colorectal cancer.

Angiogenesis Inhibitors↗