G-protein coupled receptor-associated sorting protein 1 (GASP-1), a ubiquitous tumor marker, promotes proliferation and invasion of triple negative breast cancer

We have identified the novel protein GASP-1 (G protein coupled receptor-associated sorting protein 1) that appears to be a universal cancer marker and the expression of which in tumor tissue and patient sera is predictive of cancer severity (Tuszynski et al. 2011; Zheng et al. 2012; Zheng 2013; Chang and Tuszynski, 2020). In preliminary results we discovered that a GASP-1 antibody inhibited the growth of the triple negative breast cancer cell line MDA-MB-231 and transient reduction of GASP-1 in these cells decreased their proliferation. To further substantiate these results, we over and under-expressed GASP-1 in stable clones of MDA-MB-231 cells and evaluated their growth and invasive activities. Cells under-expressing GASP-1 failed to grow after 4 days in culture and eventually died. In contrast GASP-1 expressing cells grew exponentially. Similarly, GASP-1 under-expressing cells formed 30% fewer colonies in soft agar as compared to controls and whereas GASP-1 over-expressing cells formed 2-fold more colonies than controls. In tumor cell invasion assays GASP-1 over-expressing cells were over 10-fold more invasive than controls whereas GASP-1 under-expressing cells were over 10-fold less invasive than controls. In IHC staining studies of breast cancer cells, we found that the overexpressed GASP-1 appear in granules of different sizes that are directly correlated with cancer invasiveness. Our results strongly indicate that GASP-1 promotes proliferation and invasion of the triple negative breast cancer cell line MDA-MB-231 and targeting GASP-1 for treatment of breast cancer is indicated.

Thrombospondin Levels in Patients with Malignancy

Thrombospondin (TSP), a large glycoprotein present in platelets, and various normal and tumor tissues, has recently been shown to promote cell adhesion and platelet aggregation. Most importantly because TSP has been shown to promote metastasis of melanoma tumor cells to the lung in a murine model (1) and since thromboembolic events commonly occur in patients afflicted with metastatic tumors, we explored the role of TSP in human cancer by measuring TSP blood levels in patients with various malignant neoplasms. Blood TSP levels were measured by indirect enzyme-linked immunoadsorbent assay (ELISA) from 20 control subjects, 22 patients with gastrointestinal (GI) cancer, 18 patients with breast cancer, and 17 patients with lung cancer. Control subjects consisted both of healthy subjects and acutely ill patients with no malignancies. TSP levels of both healthy and acutely ill controls were found to range between 245-440 μg/ml with a mean of 365 μg/ml. In contrast, elevated levels of TSP greater than the mean value of 400 μg/ml for controls ranging between 590-3,650 μg/ml were found in 20/22 (91%) patients with GI malignancies, 13/18 (72%) patients with breast cancer, and 15/17 (88%) with lung cancer. Mean TSP levels of GI, breast, and lung cancer patients were 3, 2, and 3 fold greater than controls, respectively. Increased blood TSP levels in patients were not due to increased levels of platelets since both control and patient groups had platelet counts within the normal range. These results suggest that TSP may play a role in tumor cell metastasis in man and could serve as a blood marker for metastasis.

Abstract 570: Long-term efficacy and downstream mechanism of anti-Annexin A2 monoclonal antibody in a pre-clinical model of aggressive human breast cancer

Abstract:

There are considerable direct evidences to support that calcium binding protein ANX A2 is a potential target for aggressive breast cancer. The most compelling evidence is based on the fact that ANX A2 overexpress specifically in aggressive triple negative human breast cancer (TNBC) cell lines as well as in human breast cancer tissues. Previously, we and others have demonstrated a unique role of ANX A2 in cancer invasion including breast cancer. Moreover we demonstrated that anti-ANX A2 monoclonal antibody (anti-ANX A2mAb)-mediated immunoneutralization of ANX A2 inhibited invasive human breast growth in a xenograft model. We further evaluated long-term effect of multiple treatments of anti-ANX A2mAb and its mechanism of inhibition of human breast tumor growth. We now show that three treatments of anti-ANX A2mAb showed significant inhibition of breast tumor growth in immunodeficient mice and anti-tumor response was started from day 94. After treatments, we followed tumor growth for 172 days and our results demonstrated 67% inhibition of tumor growth without detectable adverse effects. Biochemical analysis demonstrated anti-ANX A2mAb treatment caused significant inhibition of tissue plasminogen activator (tPA) synthesis in the tumor microenvironment. This led to disruption of plasmin generation that consequently inhibited activation of MMP-9 and MMP-2. These results suggest that ANX A2 plays an important role in aggressive breast tumor growth by regulating proteolytic pathway in the tumor microenvironment. ANX A2 may represent a new target for the development of therapeutics for the treatment of aggressive breast cancer.

Citation Format: Mahesh C. Sharma, George P. Tuszynski, Marc R. Blackman, Meena Sharma. Long-term efficacy and downstream mechanism of anti-Annexin A2 monoclonal antibody in a pre-clinical model of aggressive human breast cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 570.

Long-term efficacy and downstream mechanism of anti-annexinA2 monoclonal antibody (anti-ANX A2 mAb) in a pre-clinical model of aggressive human breast cancer

There is considerable direct evidence that calcium binding protein ANX A2 is a potential target for treating aggressive breast cancer. The most compelling data are based on the finding of ANX A2 overexpression in aggressive triple negative human breast cancer (TNBC) cell lines and in human breast cancer tissues. Previously, we and others reported a unique role of ANX A2 in cancer invasion, including breast cancer. Moreover, we demonstrated that anti-ANX A2 mAb-mediated immunoneutralization of ANX A2 inhibited invasive human breast cancer growth in a xenograft model. We further evaluated the long-term effects of multiple treatments with anti-ANX A2 mAb and its mechanism of inhibition on human breast tumor growth. We now demonstrate that three treatments with anti-ANX A2 mAb led to significant inhibition of breast tumor growth in immunodeficient mice, and that the anti-tumor response was demonstrable from day 94. After treatment, we followed tumor growth for 172 days and demonstrated 67% inhibition of tumor growth without detectable adverse effects. Biochemical analysis demonstrated that anti-ANX A2 mAb treatment caused significant inhibition of conversion of tissue plasminogen activator (tPA) in the tumor microenvironment. This led to disruption of plasmin generation that consequently inhibited activation of MMP-9 and MMP-2. These results suggest that ANX A2 plays an important role in aggressive breast tumor growth by regulating proteolytic pathways in the tumor microenvironment. ANX A2 may represent a new target for the development of therapeutics for treatment of aggressive breast cancer.

Angiocidin induces differentiation of acute myeloid leukemia cells

Acute myeloid leukemia (AML) is a malignant proliferative disorder in which leukemic cells fail to terminally differentiate and accumulate in the blood and bone marrow. Standard AML therapy requires intensive chemotherapy with a low rate of durable remission and is associated with significant treatment-related toxicity, especially in elderly patients. Therefore, new therapeutic options for the treatment of AML are urgently needed. We previously reported that the novel angiogenic inhibitor, angiocidin, induces differentiation of monocytes to macrophages. Here we investigate the effects of angiocidin on AML cells lines and primary AML cells. Differentiation was assessed by flow cytometry measuring the increase in expression of cell surface marker characteristic of normal macrophages. Four AML cell lines (THP-1, Mono-mac-1, HL-60 and MV4-11) and 5 of 10 primary human AML samples showed evidence of differentiation when cultured in vitro for 24 h with 10 μg/mL angiocidin. Additionally, we found that angiocidin promoted secretion of a number of cytokines from the cell lines as well as patient cells. We next evaluated the effect of angiocidin on a xenotransplanted primary human AML sample engrafted in NSG mice. We found angiocidin monotherapy reduced the human AML burden in bone marrow by 63% relative to untreated control. Interestingly, angiocidin+cytosine arabinoside (Ara-C) combination therapy reduced human AML in bone marrow by 79%. We believe the combination of in vitro data supporting the capacity of angiocidin to drive differentiation in multiple AML cell lines and primary human AML samples and its activity in a xenotransplantation model that reproduces the human disease is significant. These observations support the continued evaluation and development of angiocidin as a potential novel, non-toxic therapy for AML.

Abstract 5392: Angiocidin induces differentiation of acute myeloid leukemia (AML) cells

Acute myeloid leukemia (AML) is a malignant proliferative disorder where blast stage cells fail to terminally differentiate and accumulate in the blood and bone marrow. AML represents a very significant health risk in the general population with rising incidence in aging adults. From 2004-2008 the median age at diagnosis was 67.8 years and it is estimated 12,950 adults will be diagnosed with 9,050 deaths from AML leukemia in 2011 (http://seer.cancer.gov/statfacts/html/amyl.html, accessed November 2011). Standard AML therapy requires intensive combination chemotherapy with a low rate of durable remissions often requiring stem cell transplantation and associated with significant treatment-related toxicity, especially in elderly patients. Due to this toxicity, the majority of elderly patients are not eligible for therapy. Therefore, new therapeutic options for the treatment of AML are urgently needed. In this study, we present evidence that the human protein angiocidin, discovered in our laboratory, has the potential to be used as a novel, non-toxic therapy for AML. We found that angiocidin can induce both AML cell lines and primary patient cells to increase expression of surface markers characteristic of a more normal differentiated phenotype. We evaluated expression of CD14, a major receptor for the innate immune system in macrophages, CD54 or ICAM-1, the major adhesion receptor used by macrophages for endothelial transmigration, and CD15, a neutrophil phagocytosis receptor. Expression of these receptors was measured by flow cytometry after cells were cultured for 24 hours in media alone or media containing 10 μg/ml angiocidin. Angiocidin up-regulated these receptors by more than 10 fold in 50% of the AML cells tested. The AML cells included the cell line THP-1 and 11 primary AML patient cells. Angiocidin up-regulated CD14 and CD54 in THP-1 cells and in 3 out of 5 M5 phenotype AML patient cells tested and 1 M4 AML phenotype out of 6 M4 samples tested. Angiocidin also up-regulated CD15 in 1 M4 AML patient phenotype out of 6 M4 patient cells tested. These results suggest that angiocidin can differentiate AML cells and therefore has the potential to be developed as differentiation therapy for AML.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 5392. doi:1538-7445.AM2012-5392

Angiocidin inhibits breast cancer proliferation through activation of epidermal growth factor receptor and nuclear factor kappa (NF-ĸB)

Angiocidin, a tumor-associated peptide, has been previously shown to inhibit tumor progression by blocking angiogenesis. We now show that angiocidin has a direct inhibitory effect on tumor cell proliferation. MDA-MB-231 breast cancer cells were inhibited from proliferating in the presence of epidermal growth factor (EGF) and angiocidin. Angiocidin transfected breast cancer cells also displayed growth inhibition in vitro and failed to develop significant tumors in mice as compared to vector controls. The anti-proliferative effect of angiocidin was reversed by treating the cells with the epidermal growth factor receptor (EGFR) inhibitor 4557W, a potent tyrosine kinase inhibitor. Consistent with these results, we found that treatment of breast cancer cells with angiocidin induced a 2.3 fold increase in EGFR tyrosine 845 phosphorylation while no change in phosphorylation was observed in the remaining 16 phosphorylation sites of EGFR and those of its family members as measured by a human EGFR phosphorylation array. Treatment of breast cancer cells with angiocidin also resulted in the activation of nuclear factor ĸB (Nf-ĸB) and the de novo up-regulation of many down-stream genes transcribed by Nf-ĸB, including cytokines, inflammatory mediators and the cell cycle inhibitor p21(waf1). Therefore, angiocidin is a peptide that not only inhibits tumor angiogenesis but also directly induces inhibition of tumor growth progression through the activation of EGFR and down-stream genes transcribed by Nf-ĸB.

Thrombospondin 1, Fibronectin, and Vitronectin are Differentially Dependent Upon RAS, ERK1/2, and p38 for Induction of Vascular Smooth Muscle Cell Chemotaxis

Background: Thrombospondin 1 (TSP-1), fibronectin (Fn), and vitronectin (Vn) promote vascular smooth muscle cell (VSMC) chemotaxis through a variety of second messenger systems, including Ras, ERK1/2, and p38. Hypothesis: Ras, ERK1/2, and p38 differentially affect TSP-1-, Fn-, and Vn-induced VSMC chemotaxis. Methods: Bovine VSMCs were transfected with Ras N17 or treated with the following inhibitors: a farnesyl protein transferase (FPT) inhibitor, PD098059 (ERK1/2 inhibitor), or SB202190 (p38 inhibitor). Thrombospondin 1, Fn, and Vn were used as chemoattractants. Results were analyzed by analysis of variance (ANOVA) with post hoc testing (P < .05). Results: Ras N17 transfection or FPT inhibitor treatment inhibited TSP-1-, Fn-, and Vn-induced chemotaxis. PD098059 or SB202190 resulted in more inhibition of VSMC migration to TSP-1 than to Fn or Vn. Conclusions: Ras appears equally relevant in the signal transduction pathways of TSP-1-, Fn-, and Vn-induced VSMC chemotaxis. Thrombospondin 1-induced migration is more dependent upon ERK1/2 and p38 than Fn- or Vn-included migration.

The immunomodulatory role of angiocidin, a novel angiogenesis inhibitor

The observation that many tumors exist in a microenvironment comprised of immune cells has led to the hypothesis that the immune system may play a significant role in the suppression of tumor growth. It is now clear that immune effector cells are capable of recognizing and destroying some cancer cells. However, tumors have developed numerous mechanisms by which they avoid immune recognition and death. Cancer immunotherapy attempts to harness the power of the immune system and direct it against tumor growth, while circumventing the immune-evasion strategies utilized by tumors. Many approaches are currently being investigated, including the re-infusion of autologous immune effector cells (i.e. cytotoxic T lymphocytes and macrophages) back into hosts after ex vivo expansion and activation. The therapeutic effects of specific cytokines are also being evaluated for their impact on tumor growth. Our lab has discovered a novel thrombospondin-1 (TSP-1) binding protein, termed "angiocidin", with potent anti-tumor and anti-angiogenic capabilities. To further investigate the anti-tumor activity of angiocidin, we examined whether angiocidin could play a role in immune system modulation. We have found that the monocytic leukemia cell line THP-1, as well as freshly isolated human peripheral blood monocytes, differentiate into macrophage-like cells when treated with angiocidin. These cells underwent dramatic morphological changes and became more phagocytic. Angiocidin-treated monocytes also activated T lymphocytes in co-culture conditions. Angiocidin-treated THP-1 cells upregulated cytokine mRNA expression and secretion via NF-kappaB, MAPK, and PI3-K. Based on these data, we hypothesize that angiocidin's ability to elicit tumor cell death may be mediated in part by it's pro-inflammatory effects on immune cells in the tumor microenvironment.

Effect of VP12 and viperistatin on inhibition of collagen-receptor-dependent melanoma metastasis

Viperistatin and VP12 isolated from Vipera paleastinae venom showed a potent inhibitory activity against collagen receptors, alpha1beta1 and alpha2beta1 integrins, respectively. Structurally, viperistatin belongs to the disintegrin family of proteins, whereas VP12 is composed of two subunits VP12A and VP12B displaying amino acid sequence homology with heterodimeric C-lectin type proteins. Viperistatin and VP12 used separately and simultaneously inhibited pro-metastatic activities of melanoma cells lines. The level of inhibition of MV3 and HS.939T human cell lines in cell adhesion and migration assays by both compounds was correlated with expression of alpha1beta1 and alpha2beta1 integrins on the cell surface. MV3 cells express collagen receptors to much higher extent than HS.939T and required the application of higher concentrations of inhibitors to block their adhesion to collagen types I and IV. A melanoma cell transmigration assay through a dHMVEC layer revealed that alpha1beta1 integrin plays a significant role in invasion of HS.939T cells, while alpha2beta1 integrin appears to be more important for MV3 cells. In an animal model of hematogenous metastasis of the mouse B16F10 cell line, the inhibitory effect of viperistatin and VP12 was only partial. These data suggest that collagen receptors may be an interesting target for development of new anti-metastatic therapies.

Regulatory effect of nerve growth factor in alpha9beta1 integrin-dependent progression of glioblastoma

In the present study we described the role of alpha9beta1 integrin in glioblastoma progression following its interaction with nerve growth factor (NGF). The level of expression of alpha9beta1 on astrocytomas is correlated with increased grade of this brain tumor and is highest on glioblastoma, whereas normal astrocytes do not express this integrin. Two glioblastoma cell lines, LN229 and LN18, that are alpha9beta1 integrin positive and negative, respectively, were used for alpha9beta1 integrin-dependent NGF-induced tumor progression. NGF was a significant promoter of promigratory and pro-proliferative activities of glioblastoma cells through direct interaction with alpha9beta1 integrin and activation of MAPK Erk1/2 pathway. The level of NGF increases approximately threefold in the most malignant glioma tissue when compared with normal brain. This increase is related to secretion of NGF by tumor cells. Specific inhibitors of alpha9beta1 integrin or gene silencing inhibited NGF-induced proliferation of LN229 cell line to the level shown by LN18 cells. VLO5 promoted alpha9beta1-dependent programmed cell death by induction of intrinsic apoptosis pathway in cancer cells. LN229 cells were rescued from proapoptotic effect of VLO5 by the presence of NGF. This disintegrin significantly inhibited tumor growth induced by implantation of LN229 cells to the chorioallantoic membrane (CAM) of quail embryonic model, and this inhibitory effect was significantly abolished by the presence of NGF. alpha9beta1 integrin appears to be an interesting target for blocking the progression of malignant gliomas, especially in light of the stimulatory effect of NGF on the development of these tumors and its ability to transfer proapoptotic signals in cancer cells.

Angiostatic activity of obtustatin as alpha1beta1 integrin inhibitor in experimental melanoma growth

The presented results show the effect of targeting of collagen receptor, alpha1beta1 integrin expressed on the endothelial cells on the development of experimental melanoma and pathological angiogenesis. Obtustatin, a snake venom KTS-disintegrin, was applied as a specific inhibitor of this integrin. This low molecular weight peptide revealed a potent therapeutic effect on melanoma progression in 2 animal systems, mouse and quail. Its oncostatic effect was related to the inhibition of angiogenesis. Obtustatin inhibited the neovascularization ratio on the CAM embryo of quail, which was pathologically induced by the developing tumor. The i.v. administration of obtustatin completely blocked cancer growth of MV3 human melanoma in nude mice. In B16F10 syngeneic mouse model treatment with the disintegrin revealed a lower effect, although the development of the tumor was significantly reduced for both dosages. The mechanism of obtustatin action is related to the blocking of microvascular endothelial cell proliferation, which undergoes apoptosis in caspase-dependent manner. Summarizing, we present studies of low molecular weight disintegrin, obtustatin as a potential therapeutic compound for treatment of melanoma that contain a high level of vascularization.

The novel angiogenic inhibitor, angiocidin, induces differentiation of monocytes to macrophages

We previously showed that angiocidin, a tumor and vascular associated protein, is a potent inhibitor of angiogenesis and tumor growth. Angiocidin is a multidomain protein that exerts its antiangiogenic activity through multiple mechanisms, including effects on cell matrix interaction. Here, we describe another activity of angiocidin that may contribute to its antitumor activity. We show that angiocidin activates monocytes to secrete a mixture of proinflammatory cytokines and induces them to differentiate into macrophage-like cells. Using the monocytic cell line THP-1, we show that angiocidin induces the cells to become adherent and phagocytic, express macrophage markers, and secrete matrix metalloproteinase-9. Microarray analysis of control and angiocidin-treated THP-1 cells revealed that angiocidin up-regulated p105/p50, p100/p52, and rel B, components of the nuclear factor-kappaB (NF-kappaB) pathway. We confirmed the microarray data and showed that angiocidin induced phosphorylation of I kappa beta, p50, and p65 and translocation of p50 and p65 to the nucleus. We also showed that angiocidin activated up-stream mediators of NF-kappaB, such as the mitogen-activated protein kinase (MAPK) pathway and phosphoinositide-3 kinase (PI3K). Blockage of NF-kappaB and MAPK activation with small molecule inhibitors completely prevented angiocidin-mediated secretion of cytokines from THP-1 cells, but did not inhibit their adhesive phenotype. Blocking PI3K inhibited both secretion of cytokines, as well as the adhesive phenotype. These data suggest that angiocidin activates monocytes to secrete cytokines and differentiates them to a macrophage-like phenotype through at least two pathways mediated by MAPK and NF-kappaB, as well as PI3K.

Integrin alpha9 beta1 is a receptor for nerve growth factor and other neurotrophins

The integrin alpha9beta1 is a multifunctional receptor that interacts with a variety of ligands including vascular cell adhesion molecule 1, tenascin C and osteopontin. We found that this integrin is a receptor for nerve growth factor (NGF) and two other neurotrophins, brain-derived neurotrophic factor and NT3, using a cell adhesion assay with the alpha9SW480 cell line. Interaction of alpha9beta1 with NGF was confirmed in an ELISA assay by direct binding to purified integrin. alpha9beta1 integrin binds to neurotrophins in a manner similar to another common neurotrophin receptor, p75(NTR) (NGFR), although alpha9beta1 activity is correlated with induction of pro-survival and pro-proliferative signaling cascades. This property of alpha9beta1 resembles the interaction of NGF with a high affinity receptor, TrkA, however, this integrin shows a low affinity for NGF. NGF induces chemotaxis of cells expressing alpha9beta1 and their proliferation. Moreover, alpha9beta1 integrin is a signaling receptor for NGF, which activates the MAPK (Erk1/2) pathway. The alpha9beta1-dependent chemotactic ability of NGF appears to result from the activation of paxillin.

Angiocidin inhibitory peptides decrease tumor burden in a murine colon cancer model

INTRODUCTION

We have recently developed two inhibitory peptides that target angiocidin, a key mediator of tumor progression and angiogenesis. In this study, we investigate the expression of angiocidin in human colon cancer specimens and evaluate the therapeutic efficacy of our angiocidin inhibitory peptides.

METHODS

We created a colon cancer tissue array containing primary tumor, normal colon, negative and positive lymph nodes, and liver metastases (when available) from 159 consecutive colon cancer specimens. Angiocidin expression was determined by immunohistochemistry. The efficacy of 6-mer and 25-mer angiocidin inhibitory peptides was determined in a murine model of human colon cancer. Treatment efficacy was based on primary tumor volume and measures of tumor burden, including internal disease score and health score. Western blots were used to determine angiocidin expression in xenografts.

RESULTS

Eighty-nine percent of primary tumors and 91% of positive lymph nodes expressed angiocidin. Normal colon was negative in 94% of specimens, and normal lymph nodes were negative or weakly positive in 79% of specimens. All liver metastases were positive for angiocidin. Animals in both peptide treatment groups showed improvement in health score and internal disease score compared with control animals (P = 0.001). Treatment with 6-mer and 25-mer peptide resulted in 3-fold and 16-fold reductions, respectively, in primary tumor volume (P = 0.001). Angiocidin expression in primary tumors of peptide-treated mice correlated with tumor burden (P < 0.05).

CONCLUSIONS

Angiocidin is overexpressed in human colon cancer specimens. Angiocidin-inhibitory peptides are well tolerated in vivo and effectively reduce primary tumor volume and tumor burden in human colon cancer xenografts.

Clinical significance of serum angiocidin levels in hepatocellular carcinoma

Angiocidin, a tumor-secreted protein, was measured in serum of 27 healthy volunteers and 33 hepatocellular carcinoma (HCC) patients. Healthy controls either hepatitis B surface antigen (HBsAg) positive or negative showed undetectable levels. Patients had levels of angiocidin ranging from 15.09 to 195.73 pg/ml. Patients with stages III-IV had higher levels of angiocidin (97+/-13 pg/ml, n=17) compared to those with stages I-II (63+/-37 pg/ml, n=16), p<0.043. Patients with microsatellite tumor nodules had higher average levels (98+/-55 pg/ml, n=17) compared to those without microsatellite nodules (51+/-27 pg/ml, n=20), p<0.032. Our studies suggest that angiocidin predicts advanced stage and intra-hepatic metastasis.

Interaction of alpha9beta1 integrin with thrombospondin-1 promotes angiogenesis

Thrombospondin-1 is a multifunctional protein interacting with several cell surface receptors including integrins. We found that it is a ligand for alpha9beta1 integrin, and has an integrin binding site within its N-terminal domain (NoC1). Interaction of thrombospondin-1 and its recombinant NoC1 domain with alpha9beta1 integrin was confirmed in ELISA and cell adhesion assays. Binding of NoC1 to cells expressing alpha9beta1 integrin activated signaling proteins such as Erk1/2 and paxillin. Blocking of this integrin by monoclonal antibody and the met-leu-asp-disintegrin inhibited dermal human microvascular endothelial cell proliferation and NoC1-induced migration of these cells. Immunohistochemical studies revealed that alpha9beta1 is expressed on microvascular endothelium in several organs including skin, lung, heart and brain. NoC1 induced neovascularization in an experimental quail chorioallantoic membrane system and Matrigel plug formation assay in mice. This proangiogenic activity of NoC1 in vivo was inhibited by alpha9beta1 inhibitors. In summary, our results revealed that alpha9beta1 integrin expressed on microvascular endothelial cells interacts with thrombospondin-1, and this interaction is involved in modulation of angiogenesis.

Antibody-directed targeting of angiostatin's receptor annexin II inhibits Lewis Lung Carcinoma tumor growth via blocking of plasminogen activation: Possible biochemical mechanism of angiostatin's action

Angiostatin, the N-terminal four kringles (K1-4) of parent molecule plasminogen, is reported to block Lewis Lung Carcinoma (LLC) tumor growth and metastasis. However, angiostatin's mechanism of action is unclear. We earlier reported that angiostatin binds to cell surface annexin II through the lysine-binding domain (kringles 1-4) [Tuszynski, G.P., Sharma, M., Rothman, V.L., Sharma, M.C., 2002. Angiostatin binds to tyrosine kinase substrate annexin II through the lysine-binding domain in endothelial cells. Microvasc. Res. 64:448-462.]). We now show that annexin II on the cell surface of LLC cells regulates conversion of plasminogen to plasmin. Activation of plasminogen to plasmin is time-dependent, with the linear activation lasting up to 120 min. Monoclonal antibodies to annexin II reduced plasminogen activation by 92.6%, suggesting a specific role of annexin II in plasmin generation. Angiostatin also reduced plasmin generation by 81.6%, suggesting that angiostatin may be competing with plasminogen through lysine-binding domain. epsilon-Aminocaproic acid, a lysine analogue, effectively blocked plasminogen activation indicating that, indeed, the lysine-binding site of the kringles domain is required for activation. These data suggest that annexin II may be a receptor target for angiostatin's action. Therefore, we tested the effect of high affinity monoclonal antibody to annexin II in mouse model of LLC. A single dose of antibody treatment inhibited LLC tumor growth almost 70% with concomitant inhibition of circulating plasmin generation and its proteolytic activity. Taken together, it is possible that inhibition of LLC tumor growth and metastasis reported by angiostatin therapy may be due to blocking of annexin-II-dependent plasmin generation. Plasmin is known to influence angiogenic, invasive and metastatic capability of tumors.

Integrin α2β1 mediates the anti-angiogenic and anti-tumor activities of angiocidin, a novel tumor-associated protein

We recently characterized an anti-tumor protein termed angiocidin. Here, we report that angiocidin may inhibit angiogenesis by binding collagen and its receptors. Angiocidin bound purified type I collagen and alpha2beta1 with high affinity. K562 cells expressing alpha2beta1 bound and adhered to angiocidin while K562 cells which only expressed alpha5beta1 integrin showed no binding and adhesion. Binding was specific since a neutralizing antibody against alpha2beta1 inhibited binding but antibodies against alpha5beta1 had no effect. Additionally, angiocidin co-localized with alpha2beta1 on K562 alpha2beta1 transfected cells, pancreatic cancer colo 357 cells, breast cancer MB-231 cells and human umbilical endothelial vein (HUVE) cells. In an alpha2beta1-dependent collagen gel angiogenesis assay, angiocidin showed potent inhibitory activity. We identified a 20-amino-acid amino terminal peptide of angiocidin that bound both alpha2beta1 and type I collagen. This peptide promoted alpha2beta1-dependent cell adhesion and inhibited tumor growth and angiogenesis. Taken together, these results are consistent with the conclusion that the anti-tumor activity of angiocidin arises from its ability to ligate collagen and alpha2beta1 on endothelial cells and tumor cells. Our results provide support for the concept that targeting matrix-cell interactions is a viable strategy for the development of anti-cancer therapeutics.

Angiogenesis-associated protein annexin II in breast cancer: selective expression in invasive breast cancer and contribution to tumor invasion and progression

Many advanced human tumors including breast cancer overproduce plasmin that is known to promote angiogenesis and metastasis. The mechanism of this effect is poorly understood. Here we report that annexin II, an endothelial co-receptor for tPA (tissue-type plasminogen activator) and plasminogen, was undetectable in normal and hyperplastic ductal epithelial cells and ductal complexes. By contrast, it was consistently expressed in invasive breast cancer and ductal carcinoma in situ (DCIS) indicating its involvement in breast cancer. Using the well established invasive/metastatic MDA-MB231 cell line and the noninvasive/nonmetastatic MCF-7 human breast cancer cell line, we investigated the mechanism by which annexin II regulates breast cancer progression and metastasis. Western and Northern blot analyses demonstrate selective expression of annexin II in MDA-MB231 cells but not in poorly invasive MCF-7 cells suggesting its participation in invasive breast cancer. Since annexin II is a receptor for plasminogen, we tested whether MDA-MB231 cells are capable of producing plasmin in vitro. MDA-MB231 cell membranes induced plasmin generation in a time-dependent manner while those from MCF-7 cells failed to convert plasminogen to plasmin. The generated plasmin is capable of degrading ECM consequently facilitating cell invasion and migration, biological functions required for angiogenesis and metastasis. Plasmin generation and its dependent invasion and migration can be blocked by a monoclonal antibody to annexin II or angiostatin, potent inhibitors of angiogenesis, breast cancer, and metastasis. Our findings indicate that annexin II-dependent localized plasmin generation by human breast cancer cells could contribute to angiogenesis and metastasis. These results suggest that annexin II may be an attractive target for new anti-angiogenic and anti-breast cancer therapies.

Endothelial apoptotic activity of angiocidin is dependent on its polyubiquitin binding activity

We recently cloned the full-length cDNA of a tumour-associated protein. The recombinant protein expressed in bacteria and referred to as angiocidin has potent antitumour activity in vivo and in vitro. Angiocidin inhibits tumour growth and angiogenesis by inducing apoptosis in endothelial cells. Based on the sequence similarity of angiocidin to S5a, one of the major polyubiquitin recognition proteins in eukaryotic cells, we postulated that the antiendothelial activity of angiocidin could be due in part to its polyubiquitin binding activity. In support of this hypothesis, we show that angiocidin binds polyubiquitin in vivo with high affinity and colocalises with ubiquitinated proteins on the surface of endothelial cells. Binding is blocked with an antiubiquitin antibody. Angiocidin treatment of endothelial cells transfected with a proteasome fluorescent reporter protein showed a dose-dependent inhibition of proteasome activity and accumulation of polyubiquitinated proteins. Full-length angiocidin bound polyubiquitin while three angiocidin recombinant proteins whose putative polyubiquitin binding sites were mutated either failed to bind polyubiquitin or had significantly diminished binding activity. The in vitro apoptotic activity of these mutants correlated with their polyubiquitin binding activity. These data strongly argue that the apoptotic activity of angiocidin is dependent on its polyubiquitin binding activity.

Cloning and characterization of angiocidin, a tumor cell binding protein for thrombospondin-1

Thrombospondin-1 (TSP-1) is a matrix protein that has been implicated in mechanisms of tumor progression. Our laboratory previously showed that the CSVTCG (cys-ser-val-thr-cys-gly) sequence of TSP-1 functioned as a tumor cell adhesion domain and CSVTCG peptides as well as an anti-peptide antibody possessed anti-metastatic activity in a murine model of lung metastasis. In a subsequent study, a putative TSP-1 binding protein from lung carcinoma was isolated by CSVTCG-peptide affinity chromatography. In this study, we present the full-length cDNA of this binding protein isolated from a prostate cancer cell (PC3-NI) cDNA library. The purified recombinant protein, termed angiocidin, is a potent inhibitor of tumor growth of Lewis Lung carcinoma in vivo and tumor invasion and angiogenesis in vitro. In addition, the recombinant protein inhibits tumor and endothelial cell proliferation and induces apoptosis. The activity of angiocidin both in vivo and in vitro is partially dependent on its TSP-1 binding activity, since an angiocidin deletion mutant missing a high affinity-binding site for TSP-1 failed to inhibit tumor growth in vivo and was less active in its anti-tumor and anti-angiogenic activities in vitro. These results suggest that the anti-tumor activity of TSP-1 reported in many studies may be mediated in part by binding proteins such as angiocidin. Such proteins may function as tumor-suppressor proteins, which limit the growth of tumors by inhibiting angiogenesis and cell matrix interaction.

Mechanisms of thrombospondin-1-mediated metastasis and angiogenesis

The major route of tumor spread is through the bloodstream. Once in circulation, the tumor cells aggregate in clumps with platelets, which enhances the tumor cell survival. The tumor emboli will then adhere to the endothelium and by the release of proteases extravasation of the cells will occur. One of the platelet-secreted proteins is thrombospondin-1. In this article, thrombospondin-1 will be described as a modulator of angiogenesis through its role in regulating endothelial cell apoptosis, protease expression, and vascular endothelial growth factor expression. We hope to convey the idea that activity of thrombospondin-1 in tumor progression is dependent upon its interaction with several host- and tumor-associated proteins.

Angiostatin-induced inhibition of endothelial cell proliferation/apoptosis is associated with the down-regulation of cell cycle regulatory protein cdk5

Endothelial cells (ECs) are quiescent in normal blood vessels, but undergo rapid bursts of proliferation after vascular injury, hypoxia or induced by powerful angiogenic cytokines like fibroblast growth factor (bFGF) and vascular endothelial growth factor (VEGF). Deregulated proliferation of ECs facilitates angiogenic processes and promotes tumor growth. In dividing cells, cell cycle-associated protein kinases, which are referred as cyclin-dependent kinases (cdks), regulate proliferation, differentiation, senescence, and apoptosis. Cyclin-dependent kinase-5 (cdk5) is expressed in neuronal cells and plays an important role in neurite outgrowth, of neuronal migration and neurogenesis, its functions in non-neuronal cells are unclear. Here, we show for the first time that the cdk5 is expressed at high levels in proliferating bovine aortic endothelial (BAE) cells, by contrast insignificant low levels of cdk5 expression in quiescent BAE cells. In addition, bFGF up-regulates cdk5 expression in a dose-dependent fashion. Interestingly, temporal expression data suggests that cdk5 expression is very low between 24-48 h, but high level of cdk5 expression was detected during 60-72 h. This later time corresponds to the time of completion of one cell cycle (doubling of cell population) of BAE cell culture. Angiostatin (AS), a powerful inhibitor of angiogenesis inhibits ECs proliferation in dose-dependent manner with concomitant down-regulation of cdk5 expression. The role of cdk5 in ECs, proliferation and apoptosis was confirmed by selective inhibition of cdk5 expression by the purine derivative roscovitine, which inhibits bFGF-stimulated BAE cells proliferation and induces apoptosis in dose-specific manner. By contrast, the roscovitine analog olomoucine, which is a specific inhibitor of cdk4, but not of cdk5 failed to affect ECs proliferation and apoptosis. These data suggest for the first time that neuron specific protein cdk5 may have significant role in the regulation of ECs proliferation, apoptosis, and angiogenesis and extends beyond its role in neurogenesis.

Thrombospondin-1 up-regulates tumor cell invasion through the urokinase plasminogen activator receptor in head and neck cancer cells

BACKGROUND

We have previously demonstrated that thrombospondin-1 (TSP-1) is expressed in squamous cell carcinomas of the head and neck. We have also shown that TSP-1 promotes tumor cell invasion through up-regulation of the urokinase plasminogen activator receptor (uPAR), in adenocarcinoma models. We now determined the role of TSP-1 in the regulation of uPAR expression and tumor cell invasion in squamous cell carcinoma of the head and neck cells.

MATERIALS AND METHODS

KB squamous cell carcinoma of the head and neck cells were used. The effect of TSP-1 on uPAR and its ligand, urokinase plasminogen activator (uPA), expression were determined by ELISA. The effect of TSP-1 on KB tumor cell invasion was determined in a modified Boyden chamber collagen invasion assay. To determine the role of uPAR on TSP-1-mediated KB tumor cell invasion, we used the three following different strategies: (a). blocking uPAR or its ligand, uPA, with neutralizing antibodies; (b). enzymatic cleavage of uPAR with glycosylphosphatidylinositol (GPI)-specific phospholipase C; and (c). inhibition of plasminogen binding by using epsilon-aminocaproic acid.

RESULTS

TSP-I up-regulated uPAR and uPA expression 3- and 4-fold, respectively. TSP-1 up-regulated KB tumor cell invasion 5-fold. Inhibition of uPAR blocked the TSP-1-mediated up-regulation of KB tumor cell invasion.

CONCLUSIONS

Our data support a central role for TSP-1 in the regulation of uPAR and tumor cell invasion in squamous cell carcinomas of the head and neck cells. Furthermore, uPAR seems to play a crucial role in TSP-1-mediated squamous cell carcinoma of the head and neck tumor cell invasion.

Clinical significance of thrombospondin 1 expression in hepatocellular carcinoma

PURPOSE

Thrombospondin 1 (THBS 1) is a matricellular protein capable of modulating angiogenesis. However, the actual role of THBS 1 in angiogenesis and tumor progression remains controversial. Hepatocellular carcinoma (HCC) is a hypervascular tumor characterized by neovascularization. The significance of THBS 1 in HCC remains unknown. In this study, the significance of THBS 1 in HCC was evaluated by correlating its expression with clinicopathological data. The possible role of THBS 1 in the angiogenesis of HCC was also studied by correlating its expression with vascular endothelial growth factor (VEGF) expression.

EXPERIMENTAL DESIGN

Sixty HCC patients were recruited in this study. THBS 1 and VEGF protein expression in tumorous livers were localized by immunohistochemical staining and quantified by ELISA. THBS 1 mRNA was quantified by quantitative reverse transcription-PCR.

RESULTS

Immunohistochemical staining of THBS 1 was positive in HCC cells in 51.7% of patients and in stromal cells in 65% of patients. Tumor THBS 1 protein level was significantly correlated with its mRNA expression (P = 0.001) and was significantly correlated with tumor VEGF protein levels (P = 0.001). Its expression was significantly associated with the presence of venous invasion (P = 0.008) and advanced tumor stage (P = 0.049). High THBS 1 expression was also a prognostic marker of poor survival in HCC patients.

CONCLUSIONS

This study shows that high expression of THBS 1 is associated with tumor invasiveness and progression in HCC. THBS 1 appears to be a proangiogenic factor that stimulates angiogenesis in HCC in view of its positive correlation with VEGF expression.

Antiangiogenic Therapy

Angiogenesis, the formation of blood vessels from preexisting ones, plays a crucial role in tumor progression. Activation of an "angiogenic switch" allows tumor cells to invade and metastasize. The growing interest in the use of antiangiogenic agents in the treatment and prevention of cancer lies in the theoretical advantages of this molecularly targeted modality of chemotherapy. Delivery of antiangiogenic agents are not complicated by having to penetrate large bulky masses but, instead, have easy access to tumoral endothelial cells. Antiangiogenic drugs may not cause cytopenias and thus will avoid many of the unwarranted toxicities of standard chemotherapeutic agents. Because they act directly on nascent endothelial cells, antiangiogenic agents may avoid tumor resistance mechanisms. If antiangiogenic agents are successful, they might be applicable to many tumor types and not be dependent on cell type or growth fraction of cells within a tumor. However, several important obstacles remain with regards to using antiangiogenic drugs in clinical trials with which we must contend in order to determine accurately the efficacy of these agents. In this article, we review the different classes of antiangiogenic agents available, ongoing clinical trials, as well as potential pitfalls and future directions in this exciting field.

Obtustatin: a potent selective inhibitor of alpha1beta1 integrin in vitro and angiogenesis in vivo

A novel disintegrin, obtustatin, was purified from the venom of the Vipera lebetina obtusa viper. Obtustatin is the shortest disintegrin yet described, containing only 41 amino acids. It contains a similar pattern of cysteines to the short disintegrins echistatin and eristostatin but contains the sequence KTS rather than RGD in its active site loop. Obtustatin is a potent and selective inhibitor of alpha1beta1 integrin. It does not inhibit the closely related integrin alpha2beta1, nor a panel of other integrins tested. It does not inhibit ligand binding to the recombinant alpha1 I-domain. Importantly, obtustatin potently inhibited angiogenesis in vivo in the chicken chorioallantoic membrane assay, and in the Lewis lung syngeneic mouse model, it reduced tumor development by half, confirming and extending previous results on the relevance of alpha1beta1 integrin to angiogenesis and suggesting novel approaches to the generation of angiogenesis inhibitors.

Angiostatin binds to tyrosine kinase substrate annexin II through the lysine-binding domain in endothelial cells

Angiostatin(AS), an internal fragment of plasminogen, is one of the most potent specific inhibitors of angiogenesis. Angiostatin treatment has resulted in the complete regression of human tumors implanted subcutaneously into nude mice and has great therapeutic value (O'Reilly et al., Nat. Med. 2, 689-692, 1996). Despite promising therapeutic value in the treatment of cancer, the mechanism of its action is still unknown. We found that angiostatin binds to a 35-kDa protein in bovine aortic endothelial (BAE) cells (Sharma et al., Proc. Am. Assoc. Cancer Res. 42, 568, A3050, 2002). In an attempt to begin to understand angiostatin's mechanism of action, we have purified and characterized this 35-kDa protein from BAE cells. Internal peptide sequence analysis of purified protein demonstrated (SLYYIQQDTK, SYSPYDMLESIK, and ALLYLXGGDD) 100% sequence identity with tyrosine kinase substrate annexin II. Solid phase binding analysis suggests that angiostatin specifically bound to purified annexin II immobilized on 96-well plastic plates. Hundred-fold molar excess of unlabeled AS and anti-annexin II antibody inhibited bindings 85 and 55%, respectively, suggesting specific interaction. Annexin II is a predominant receptor for angiostatin, since neutralizing the angiostatin by soluble receptor (annexin II) effectively blocks angiostatin's anti-EC activity. Similarly, saturating the annexin II receptor by plasminogen in endothelial cells also blocks angiostatin's activity. Both angiostatin and plasminogen bind to purified annexin II in BAE cells saturably with apparent K(d) values of 101 and 164 nM, respectively, for purified annexin II and K(d) values of 83 and 125 nM, respectively, for BAE cells. Anti-annexin II monoclonal antibody inhibited angiostatin and plasminogen binding to endothelial cells by 68 and 62%, respectively, supporting our in vitro studies that annexin II is a receptor for angiostatin. Angiostatin-binding protein/annexin II specifically expressed in endothelial cells but not in fibroblasts suggests its EC-specific function. Epsilon-aminocaproic acid, a lys analogue, effectively blocks angiostatin and annexin II interaction, indicating that the lysine-binding domain of AS is required for binding to annexin II. These results suggest that the antiangiogenic action of angiostatin may be mediated via interaction with annexin II. Identification of annexin II as a receptor for angiostatin provides further evidence that clotting and fibrinolytic pathways are directly involved in the angiogenic process.

Up-regulation of matrix metalloproteinase 9 by thrombospondin 1 in gastric cancer

BACKGROUND

Matrix metalloproteinase 9 (MMP-9) plays a key role in tumor cell invasion. It was recently reported that plasma levels of MMP-9 in patients with gastric cancer correlate with the tumors' metastatic potential. We previously demonstrated that thrombospondin 1 (TSP-1) up-regulates MMP-9 expression by endothelial cells and promotes tumor cell invasion. We hypothesized that TSP-1 plays a role in the up-regulation of MMP-9 in gastric cancer.

METHODS

MMP-9, TSP-1, and CSVTCG-specific TSP-1 receptor expression were measured by immunohistochemical staining in 31 consecutive gastric adenocarcinomas from patients who did not undergo neoadjuvant chemotherapy or radiation therapy. Additionally, we measured TSP-1, CSVTCG-specific TSP-1 receptor, and MMP-9 expression by Western blotting, zymography, and immunohistochemical staining in AGS gastric adenocarcinoma cells. We also investigated the effect of TSP-1 on MMP-9 expression by AGS cells.

RESULTS

TSP-1 localized to the tumor-associated extracellular matrix. CSVTCG-specific TSP-1 receptor and MMP-9 colocalized to tumor cells, fibroblasts, and tumor-associated microvessels. Intense staining for TSP-1, CSVTCG-specific TSP-1 receptor, and MMP-9 correlated with markers of aggressive tumor behavior. AGS gastric adenocarcinoma cells expressed high levels of CSVTCG-specific TSP-1 receptor but not TSP-1. TSP-1 up-regulated MMP-9 expression by AGS cells.

CONCLUSIONS

We conclude that TSP-1 plays a role in the up-regulation of MMP-9 expression in gastric cancer. Our data also suggest a correlation between expression of TSP-1, CSVTCG-specific TSP-1 receptor, and MMP-9 and the acquisition of an aggressive tumor phenotype.

Thrombospondin-1 promotes proliferative healing through stabilization of PDGF

PURPOSE

Thrombospondin-1 (TSP-1) mediates chemotaxis, cell proliferation, angiogenesis, and protease regulation in healing. TSP-1 also binds platelet-derived growth factor (PDGF) and transforming growth factor beta (TGF-beta). This study confirms the role of TSP-1 and defines the relationship between TSP-1 and PDGF in proliferative tissue repair.

METHODS

Purified TSP-1 was analyzed for bound PDGF. Cultured fibroblast growth response to TSP-1 and recombinant PDGF was studied and the effects of antibodies against TSP-1, PDGF, and TGF-beta on this response were evaluated. Levels of TSP-1 and PDGF and relative proteolytic activity in fluid collected from 10 skin graft donor sites were then assessed by ELISA and a protease assay kit. The effect of proteolysis on TSP-bound PDGF and free recombinant PDGF was studied by adding trypsin and measuring the remaining PDGF by ELISA.

RESULTS

TSP-1 promoted dose-dependent fibroblast growth. While antibody to TGF-beta had no effect on promotion, antibody to both TSP-1 and PDGF eliminated this. Since a strong correlation of TSP-1 with PDGF levels was found and strong proteolysis was seen in all samples, we proposed that TSP-1 protected PDGF from proteolysis. Consistent with this, we found PDGF bound to TSP-1 was 33% less degraded than free PDGF upon trypsinization.

CONCLUSIONS

These results suggest that TSP-1 stabilizes PDGF, enhancing the biological effects of PDGF in proliferative tissue repair. This effect of TSP-1 along with its matrix-modulating activities may have important clinical utility regarding topical growth factor therapy in wound healing, since high proteolytic activity is believed to be partially responsible for limiting the efficacy of this treatment.

Fibroblasts promote breast cancer cell invasion by upregulating tumor matrix metalloproteinase-9 production

BACKGROUND

Thrombospondin-1 (TSP-1) promotes breast cancer cell invasion of collagen by upregulating matrix metalloproteinase-9 (MMP-9) production. Stromal TSP-1 may play a role in regulating tumor cell invasion. We hypothesize that fibroblasts promote breast cancer cell invasion by upregulating the production of MMP-9 through TSP-1.

METHODS

MDA-MB-231 human breast carcinoma cells were grown alone or in coculture with human fibroblasts. Gelatin zymography and Western immunoblot analysis for MMP-9 were performed on the coculture cell media and the single cell media. Inhibition of fibroblast-mediated breast tumor cell invasion by an anti-TSP-1 or an anti-MMP-9 antibody was evaluated using a modified Boyden chamber.

RESULTS

Coculture experiments showed an increased production of MMP-9 when compared with breast cancer single cell culture or fibroblast single cell culture experiments as demonstrated by zymography and Western immunoblot analysis. Fibroblast-stimulated MMP-9 production was comparable with TSP-1-stimulated MMP-9 production. Anti-TSP-1 antibody and anti-MMP-9 antibody inhibited fibroblast-stimulated tumor cell invasion to 30% and 26% of controls, respectively (P <.05).

CONCLUSIONS

Fibroblasts may regulate breast cancer cell invasion by promoting tumor MMP-9 production through TSP-1. Inhibition of stromal TSP-1 stimulation of MMP-9 synthesis may prevent matrix degradation necessary for tumor invasion and metastasis.

Expression of thrombospondin-1 in human pancreatic adenocarcinomas: role in matrix metalloproteinase-9 production

Human pancreatic adenocarcinoma, an aggressive malignant disease, shows a strong desmoplastic reaction characterized by a remarkable proliferation of interstitial connective tissues. Thrombospondin-1 (TSP-1), a 450 kDa platelet and matrix glycoprotein, has been implicated in tumor invasion, angiogenesis and metastasis. TSP-1 and MMP-9 expression in pancreatic adenocarcinoma and control pancreas tissues was measured by immunohistochemistry. TSP-1 expression in pancreatic carcinoma cell lines, fibroblasts, and endothelial cells was measured by a competitive TSP-1 enzyme linked immunosorbent assay (ELISA). The effect of TSP-1 on MMP-9 production in pancreatic carcinoma cell lines was measured by zymography and Western blot analysis. Eighty five per cent (23/27) of cases of pancreatic adenocarcinoma showed increased TSP-1 staining in the desmoplastic stroma adjacent to tumor cells. No specific positive staining for TSP-1 was observed in the normal pancreatic tissues and the inflammatory areas. TSP-1 localized in tumor stroma surrounding the tumor cells expressing MMP-9. Using TSP-1 competitive ELISA, the secretion of TSP-1 by different pancreatic cancer cell lines into culture medium varied from 11.45 plus minus 14.08 to 275.82 plus minus 45.56 ng/10 6 cells/24 hours. The amounts of TSP-1 detected in both culture media and cell extracts from fibroblasts or endothelial cells were at least 2-3 fold higher than those from pancreatic cancer cells. TSP-1 augmented the production of matrix metalloproteinase-9, a matrix degrading enzyme, in pancreatic cancer cells in vitro. Stromally-derived TSP-1 up-regulates the production of MMP-9 by pancreatic adenocarcinoma. These data are consistent with the conclusion that TSP-1-rich stroma is involved in regulating matrix remodeling in tumor invasion.

The role of thrombospondin-1 in tumor progression

The role of thrombospondin-1 (TSP-1) in tumor progression is both complex and controversial. It is clear from the literature that the function of TSP-1 in malignancy depends on the presence of other factors and the level of TSP-1 expression in the tumor tissue. High levels of TSP-1 secreted by tumors, which were engineered to overexpress TSP-1, inhibit tumor growth, while anti-sense inhibition of TSP-1 production in certain tumors also inhibits growth. Clearly, the presence of other factors in these experimental systems must be important. The role of TSP-1 in angiogenesis also depends on the levels of TSP-1, the presence and level of angiogenic stimulators such as basic fibroblast growth factor (bFGF), and the localization of TSP-1 in the tissue. Matrix-bound TSP-1 promotes capillary tube formation in the rat aorta model of angiogenesis, while TSP-1 inhibits bFGF- induced angiogenesis in the rat cornea model. The inhibitory effect also depends on the proteolytic state of TSP-1 since the amino terminus promotes angiogenesis in the cornea model, while the remaining 140-kDa fragment inhibits bFGF-induced angiogenesis. Both the stimulatory and inhibitory effects of TSP-1 are likely due to upregulation of matrix-degrading enzymes and their inhibitors. These enzymes are critical for maintaining optimal matrix turnover during angiogenesis. These varied TSP-1-dependent mechanisms offer new targets for the development of anti-angiogenic therapeutics for the treatment of a variety of cancers, as well as other pathologies involving inappropriate angiogenesis such as diabetic retinopathy.

The localization of thrombospondin-1 (TSP-1), cysteine-serine-valine-threonine-cysteine-glycine (CSVTCG) TSP receptor, and matrix metalloproteinase-9 (MMP-9) in colorectal cancer

Thrombospondin-1 (TSP-1) is a 450 kDa matrix bound glycoprotein involved in tumor invasion, metastasis, and angiogenesis. One of the receptors involved in TSP-1 mediated tumor cell adhesion and metastasis is the cysteine-serine-valine-threonine-cysteine-glycine (CSVTCG) receptor. One mechanism of TSP-1 in promoting tumor cell metastasis involves the up-regulation of matrix metalloproteinase-9 (MMP-9) expression, specifically through the CSVTCG TSP-1 receptor. TSP-1 and its CSVTCG receptor has been implicated in tumor progression in a variety of cancers including breast adenocarcinomas, head and neck squamous cell carcinomas, and pancreatic carcinomas. In this study, we examined 99 cases of colorectal cancer by immunohistochemical analysis to investigate 1) the localization of TSP-1 and CSVTCG TSP-1 receptor, 2) the relationship with MMP-9, and 3) the correlation of expression with clinical staging. Strong expression of TSP-1 was observed in the submucosa or the serosa adjacent to the tumor. Positive staining for CSVTCG TSP-1 receptor was observed in tumor cells and microvessels. MMP-9 was also expressed in tumor cells. In addition, staining intensity of CSVTCG TSP-1 receptor was higher in poorly differentiated adenocarcinoma than well or moderately differentiated adenocarcinoma. Tumors in which inflammatory cells stained strongly for CSVTCG TSP-1 receptor correlated with decreased incidence of distant metastasis and angiogenesis. These data were consistent with our previous studies for breast, pancreatic, and head and neck carcinoma. They suggest an important role for TSP-1 and CSVTCG TSP-1 receptor in tumor progression in colorectal cancer.

Tumour cell thrombospondin-1 regulates tumour cell adhesion and invasion through the urokinase plasminogen activator receptor

We have previously shown that platelet-produced thrombospondin-1 up-regulates the urokinase plasminogen activator and its receptor and promotes tumour cell invasion. Although tumour cells produce thrombospondin-1 in vivo, they produce only minimal amounts of thrombospondin-1 in vitro. To determine the effect of tumour cell-produced thrombospondin-1 in the regulation of the plasminogen/plasmin system and tumour cell invasion, we studied THBS-1-transfected MDA-MB-435 breast cancer cells that overexpress thrombospondin-1. The role of urokinase plasminogen receptor in thrombospondin-1-mediated adhesion and invasion was studied by antisense inhibition, enzymatic cleavage and antibody neutralization. Tumour cell adhesion to collagen and laminin was evaluated. Tumour cell invasion was studied in a modified Boyden chamber collagen invasion assay. Tumour cell thrombospondin-1 induced a 2-7 fold increase in urokinase plasminogen activator receptor and cell-associated urokinase plasminogen activator expression and a 50-65% increase in cell-associated urokinase plasminogen activator and plasmin activities. Furthermore, tumour cell thrombospondin-1 promoted tumour cell invasion and decreased tumour cell adhesion through up-regulation of urokinase plasminogen activator receptor-controlled urokinase plasminogen activator and plasmin activities. We conclude that tumour cell-produced thrombospondin-1 may play a critical role in the regulation of tumour cell adhesion and tumour cell invasion.

Inhibition of phosphatidylinositol 3-kinase and protein kinase C attenuates extracellular matrix protein-induced vascular smooth muscle cell chemotaxis

PURPOSE

Intimal hyperplasia (IH), a significant cause of vascular reconstructive failure, is characterized by abnormal vascular smooth muscle cell (VSMC) migration, proliferation, and extracellular matrix (ECM) deposition. The ECM proteins, thrombospondin-1 (TSP-1), fibronectin (Fn), and vitronectin (Vn) can induce VSMC migration; however, the cellular signaling pathways involved are not identical for each ECM protein. Phosphatidylinositol 3-kinase (PI3K) and protein kinase C (PKC) are two enzymes that have been associated with VSMC migration. We sought to elucidate the roles of these enzymes in TSP-1-, Fn-, and Vn-stimulated VSMC migration.

METHODS

Chemotaxis assays were performed by using a modified Boyden Chamber. TSP-1, Fn, or Vn (20 microg/mL) or serum-free media (SFM) was placed in the bottom wells of the chamber. Quiescent bovine aortic VSMC were preincubated with LY 294002 (100 micromol/L), a PI3K inhibitor, bisindolylmaleimide I (GF 109203X, 1 micromol/L), a PKC inhibitor, or in SFM alone for 30 minutes. VSMCs (50,000 cells per well) were then placed in the top wells of the chamber, and the assay was conducted for 4 hours at 37 degrees C. Results were recorded as the number of cells migrated per five fields (400x) and analyzed by means of the paired t test, with P value less than.05 considered to be significant (n = 3).

RESULTS

The VSMC migration was significantly increased by TSP-1, Fn, and Vn. LY 294002 inhibited TSP-1-, Fn-, and Vn-stimulated VSMC migration (85% to 89%, P <.05). GF 109203X inhibited only TSP-1-stimulated migration (65%, P <.05).

CONCLUSION

These results suggest that TSP-1-, Fn-, and Vn-stimulated migration is at least partially dependent on PI3K. However, only TSP-1 stimulated migration is at least partially dependent on PKC.

The role of adhesive proteins in the hematogenous spread of cancer

The understanding of the mechanisms that control metastasis and invasion are critical for the identification of new targets for drug development. In this review we focused on two major pathways that mediate hematogenous cancer spread: the hemostatic system and cell adhesive interactions that lead to tumor invasion and angiogenesis. We describe the contribution of platelets and a number of adhesive proteins as well as their receptors that have recently been shown to play a role in metastasis. In addition, enzymes and their inhibitors that modulate cellular adhesive interactions are described. We hope that this summary will stimulate researchers in this area to focus their efforts on molecules that have recently been discovered. These molecules will not only lead to the fuller understanding of the "soil and seed" hypothesis proposed more than 100 years ago but also provide new therapeutic approaches for the treatment of metastatic disease.

Thrombospondin-1 regulation of smooth muscle cell chemotaxis is extracellular signal-regulated protein kinases 1/2 dependent

BACKGROUND

Thrombospondin-1 (TSP-1), an extracellular matrix protein, induces vascular smooth muscle cell (VSMC) chemotaxis. We hypothesized that extracellular signal-regulated protein kinases 1/2 (ERK1/2), a pathway of the mitogen activated protein kinase (MAPK) family, is important in TSP-1-induced VSMC chemotaxis.

METHODS

A modified Boyden chamber was used to assess chemotaxis. First, a concentration curve was performed to determine the level for optimal TSP-1-induced chemotaxis. Then quiescent VSMCs were preincubated (30 minutes) in serum-free medium, dimethyl sulfoxide (the inhibitor vehicle), or PD98059 (10 mumol/L, an upstream inhibitor of ERK1/2). VSMCs (50,000 cells/well) with the appropriate preincubation were placed in the top chamber. The bottom chamber contained TSP-1 (20 micrograms/mL) or serum-free medium. Results were recorded as cells/5 fields (400x). Then quiescent VSMCs were exposed to TSP-1 (20 micrograms/mL) for 0, 1, 5, 10, 30, 120, or 300 minutes. Platelet-derived growth factor (10 ng/mL) was the positive control for ERK1/2 activation. Western blot analysis was performed for activated ERK1/2. All comparisons were made by a paired t test (n = 3).

RESULTS

TSP-1-induced chemotaxis peaks by a concentration of 20 micrograms/mL. PD98059 inhibited TSP-1-induced chemotaxis (P < .05). ERK1/2 was activated by TSP-1-stimulated VSMCs.

CONCLUSIONS

TSP-1-stimulated VSMCs activated ERK1/2. An ERK1/2 inhibitor abolished chemotaxis, suggesting the functional importance of MAPK in TSP-1-induced VSMC chemotaxis.

Thrombospondin-1 and transforming growth factor beta-1 upregulate plasminogen activator inhibitor type 1 in pancreatic cancer

Controlled degradation of the extracellular matrix by proteases is crucial in tumor cell invasion. We have shown that thrombospondin-1 (TSP-1), through activation of transforming growth factor beta-1 (TGF-beta1), regulates the plasminogen/plasmin protease system in breast cancer. To determine whether this occurred in other epithelial neoplasms, we studied the role of TSP-1 and TGF-beta1 in the regulation of the plasminogen/plasmin system in pancreatic cancer. ASPC-1 and COLO-357 pancreatic cancer cells were treated with TSP-1 or TGF-beta1 at varying concentrations. The TSP-1 and TGF-beta1-treated cells were also treated with either anti-TSP-1, anti-TSP-1 receptor, or anti-TGF-beta1 antibodies. Urokinase plasminogen activator (uPA) and plasminogen activator inhibitor-1 (PAI-1) expression was determined by enzyme-linked immunosorbent assay. TSP-1 and TGF-beta1 promoted a dose-dependent upregulation of ASPC-1 and COLO-357 PAI-1 expression. The TSP-1 effect could be blocked with anti-TSP-1 or anti-TGF-beta1 antibodies. The TGF-beta1 effect could be blocked only with anti-TGF-beta1 antibody. Anti-TSP-1 receptor antibody blocked the TSP-1 effect on PAI-1 expression but had no effect on TGF-beta1-mediated PAI-1 expression. Neither TSP-1 nor TGF-beta1 had an effect on uPA production. We conclude that TSP-1, in a receptor-mediated process that involves the activation of TGF-beta1, upregulates PAI-1 expression in pancreatic cancer without an effect on uPA production.

Thrombospondin-1 induces activation of focal adhesion kinase in vascular smooth muscle cells

PURPOSE

Vascular smooth muscle cell (VSMC) proliferation and migration are important events in the development of intimal hyperplasia. Thrombospondin-1 (TSP-1), an extracellular matrix protein present in intimal hyperplastic lesions, has been shown to stimulate VSMC proliferation and migration. We hypothesized that the focal adhesion plaque, specifically the focal adhesion kinase (FAK) protein, may be important in the signal transduction pathway for TSP-1-induced VSMC migration.

METHODS

Growth-arrested bovine aortic VSMCs were treated with TSP-1 (20 microg/mL) for set intervals (15, 30, and 120 minutes) and compared with VSMCs grown in serum-free medium (negative control) or in the presence of a known mitogen and chemotactic factor, platelet-derived growth factor (10 ng/mL; positive control). Crude cell lysates and anti-FAK immunoprecipitates were assayed for phosphotyrosine activity by means of antiphosphotyrosine immunoblotting. The blots were quantified by means of densitometric analysis.

RESULTS

TSP-1 increased tyrosine phosphorylation of three protein bands of molecular weights 68, 125 (consistent with FAK), and 180 kDa. Immunoprecipitation with FAK antibody, followed by antiphosphotyrosine immunoblotting, indicated that there was an increase in tyrosine phosphorylation of FAK at 15, 30, and 120 minutes in the TSP-1-treated groups (P <.05).

CONCLUSION

Tyrosine phosphorylation of FAK is induced by TSP-1 stimulated VSMCs. This suggests an outside-inside signaling pathway by which TSP-1 stimulates VSMC migration.

Retinoic acid alters the mechanism of attachment of malignant astrocytoma and neuroblastoma cells to thrombospondin-1

Based on the hypothesis that the attachment of neuroectodermal cells to thrombospondin-1 (TSP-1) may affect tumor spread and play a role in the anti-tumor effects of retinoic acid, we investigated the expression of TSP-1 in these cells in situ and the effect of retinoic acid on the morphology of TSP-1-adherent neuroblastoma (SK-N-SH) and malignant astrocytoma (U-251MG) cells in vitro. TSP-1-adherent SK-N-SH cells demonstrated process outgrowth, with further neuronal differentiation after retinoic acid treatment, consistent with the in situ studies showing that TSP-1 expression occurs in a differentiation-specific manner in neuroblastic tumors. TSP-1-adherent U-251MG cells failed to spread; however, after retinoic acid treatment the cells demonstrated broad lamellipodia containing radial actin fibers and organization of integrins alpha3beta1 and alpha5beta1 in clusters in lamellipodia and filopodia. The attachment of both SK-N-SH and U-251MG cells to TSP-1 was found to be mediated by heparan sulfate proteoglycans, integrins, and the CLESH-1 adhesion domain first identified in CD36. Heparin and heparitinase treatment inhibited TSP-1 attachment. Integrins alpha3beta1 and alpha5beta1 mediated TSP-1 attachment of SK-N-SH cells, and integrins alpha3beta1, alpha5beta1, and alphavbeta3 mediated TSP-1 attachment of U-251MG cells. Attachment was dependent on the RGD sequence which is located in the carboxy-terminus of TSP-1. Treatment with a pharmacologic dosage of retinoic acid altered the TSP-1 cell adhesion mechanism in both cell lines in that neither heparin nor micromolar concentrations of the RGD peptide inhibited attachment; after treatment, attachment was inhibited by the CSVTCG peptide located in the type I repeat domain of TSP-1 and a recombinant adhesion domain (CLESH-1) from CD36. Expression of CD36 was found in the retinoic acid-treated U-251MG cells. These data indicate that neuroectodermally derived cells utilize several mechanisms to attach to TSP-1, and these are differentially modulated by treatment with retinoic acid. These data also suggest that the CSVTCG sequence of TSP-1 modulates or directs cytoskeletal organization in neuroblastoma and astrocytoma cells.

Thrombospondin 1 and its specific cysteine-serine-valine-threonine-cysteine-clycine receptor in fetal wounds

Thrombospondin 1 (TSP-1), an adhesive glycoprotein, plays an important role in platelet adhesion, inflammation, cell-cell interaction, and angiogenesis. TSP-1 is expressed by endothelial cells, fibroblasts, and macrophages. The unique cysteine-serinevaline-threonine-cysteine-glycine (CSVTCG) binding domain of TSP-1 also plays an important role in cell binding and modulation of cellular processes. The purpose of this study was to evaluate histologically and quantitatively TSP-1 and its CSVTCG receptor in fetal skin wounds over time. Pregnant ewes underwent laparotomy and hysterotomy. At 65 days gestation (term, 145 days), incisional and excisional wounds were created on the fetal back in a similar position on each animal. The uterus and laparotomy were closed. The wounds were harvested on days 1, 3, 7, 21, and 28. Expression of TSP-1 and its CSVTCG receptor was evaluated immunohistochemically and quantitated by computer image analysis in units of absorbance. Immunoglobulin G (negative) controls were performed and subtracted from the TSP-1 sample to eliminate background absorbance readings. Serum (negative) control was used for the CSVTCG receptor. Platelet concentrates were used as the positive control: TSP-1, 63.43; CSVTCG, 58.72. Results are expressed as absorbance+/-SEM. Results of TSP-1 are as follows: day 1, 33.02+/-0.26; day 3, 22.21+/-0.14; day 7, 20.56+/-1.07; day 21, 7.76+/-0.40; and day 28, 5.99+/-0.03. TSP-1 displays an early peak during fetal skin repair, followed by a steep decrease over the viewed time period. Results of CSVTCG receptor are as follows: day 1, 26.19+/-2.43; day 3, 30.20+/-0.64; day 7, 24.56+/-0.80; day 21, 24.70+/-0.40; and day 28, 21.65+/-1.39. Thus, CSVTCG receptor displays a slowed decrease in expression over time during fetal repair. No significant differences were noted between incisional and excisional samples. Temporal and histological differences exist in the localization and expression of TSP-1 and its CSVTCG receptor during fetal wound repair. TSP-1 is upregulated in tissues early. This corresponds with the known role of TSP-1 in cell-cell interaction, including potentiation of growth factor activity. TSP-1 also modulates matrix, allowing scar-free provisional matrix in the earlier stages of repair deposited by platelets. The potentiation of cell-associated protease activity by TSP-1 can support tissue and matrix turnover. This activity of TSP-1 may contribute to the formation of a scarless wound. TSP-1 destabilizes extracellular matrix contacts, and facilitates mitosis and migration. The action of TSP-1 as an adhesive protein allows numerous different cells to adhere to the extracellular membrane. CSVTCG receptor expression decreases during fetal repair as the cells migrate to the epithelial surface, suggesting a significant role of the CSVTCG receptor in keratinocytic maturation, differentiation, and epithelization.

Role of urokinase plasminogen activator receptor in thrombospondin 1-mediated tumor cell invasion

We previously showed that thrombospondin 1 (TSP-1) upregulates the plasminogen/plasmin system and promotes breast tumor cell invasion. Preliminary data from our laboratory using neutralizing antibodies suggested that the upregulation in breast tumor cell invasion seen in response to TSP-1 involved the urokinase plasminogen activator receptor (uPAR). To confirm these findings in MDA-MB-231 breast cancer cells, we developed three other strategies to study the role of uPAR in tumor cell adhesion and TSP-1-mediated tumor cell invasion: (a) enzymatic cleavage of uPAR with glycosylphosphatidylinositol-specific phospholipase C; (b) inhibition at the mRNA level with a uPAR antisense construct (cells named LKAS-MDA); (c) inhibition of plasminogen binding with the lysine analogue epsilon-aminocaproic acid. Adhesion to laminin and type I and type IV collagen with and without the addition of epsilon-aminocaproic acid was studied. Tumor cell invasion was studied in a modified Boyden chamber collagen invasion assay. Antisense uPAR inhibition decreased uPAR expression by 48-66% and cell-associated urokinase plasminogen activator (uPA) by 30-68%. Additionally, antisense uPAR inhibition induced a 68-70% reduction in uPA and plasmin activities. Antisense uPAR transfection increased tumor cell adhesion by 46-53%. A similar effect was observed in epsilon-aminocaproic acid-treated MDA-MB-231 cells. TSP-1-mediated tumor cell invasion was almost completely inhibited by either antisense uPAR inhibition or treatment with phospholipase C or epsilon-aminocaproic acid. We conclude that uPAR plays a crucial role in the regulation of tumor cell adhesion and TSP-1-mediated tumor cell invasion.

The 1998 Moyer Award. Characteristics of thrombospondin-1 and its cysteine-serine-valine-threonine-cysteine-glycine receptor in burn wounds

Thrombospondin-1 (TSP-1), an adhesive glycoprotein, plays an important role in platelet adhesion, inflammation, cell-to-cell interaction, and angiogenesis. TSP-1 is expressed by endothelial cells, fibroblasts, and macrophages. TSP-1's unique cysteine-serine-valine-threonine-cysteine-glycine (CSVTCG) specific receptor plays an important role in the binding and modulation of cellular adhesion and invasion. This article histologically and quantitatively evaluates TSP-1 and its CSVTCG receptor in adult burn wounds over time. Tissue was obtained from burn wounds on several days and samples that were 5 microns thick were placed on slides. Expression of TSP-1 and its CSVTCG receptor were evaluated immunohistochemically and quantitated by computer image analysis in units of absorbance. Immunoglobin G (IgG) (negative) controls were performed and subtracted from the TSP-1 sample to eliminate background absorbance readings. Serum (negative) control was used for the CSVTCG receptor. Platelet concentrates were used as the positive control. A quantitative examination of the results yielded the following information, expressed as absorbance +/- standard error of the mean: TSP-1: day 1, 62.0 +/- 10.13; day 3, 76.2 +/- 6.90; day 5, 36.0 +/- 3.96; day 7, 60.4 +/- 5.67; and day 9, 29.5 +/- 2.91. TSP-1 displays an early peak, followed by a steep decrease over the time period studied. The readings for the CSVTCG receptor are as follows: day 1, 33.8 +/- 1.87; day 3, 34.5 +/- 5.39; day 7, 39.1 +/- 1.93; day 21, 39.1 +/- 1.93; day 28, 34.8 +/- 3.67. In contrast, the CVSTCG receptor continues to be present in the wound over time. Histologic findings are reported, and photographs and a histopathologic analysis are included. The information presented in this article leads to the conclusion that temporal and histologic differences exist in the localization and expression of TSP-1 and its CSVTCG receptor. TSP-1 is up-regulated in injured tissues immediately after the injury; it is rapidly down-regulated as the tissue heals. In contrast, the levels of the CSVTCG receptor remain relatively constant during the healing process. These data are consistent with TSP-1's known role in cell-to-cell interaction, including the modulation of the growth factor and protease activity.