| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
Tumor Biology |
EntreMed, Inc., Laboratory of Discovery Research, Rockville, Maryland 20850 [T. A. H., G. M. S., A. P., S. J. G., V. S. P.], and Corvas International, San Diego, California 92121 [G. P. V., W. E. R.]
| ABSTRACT |
|---|
|
|
|---|
| INTRODUCTION |
|---|
|
|
|---|
To determine whether the coagulation cascade supports tumor growth, we initially focused our studies on the TF/fVIIa2 complex, which has been identified as the major procoagulant activity in cancer. Several studies suggest that the TF/fVIIa complex may support tumor growth and angiogenesis (13 , 14) . We studied the activity of two inhibitors of the TF/fVIIa complex, human TFPI and recombinant NAPc2, a factor X-dependent inhibitor of TF/fVIIa, derived from the hookworm Ancylostoma caninum. We show that these specific inhibitors of the TF/fVIIa complex inhibit the growth of primary and metastatic tumors in mice. Interestingly, a second anticoagulant protein from A. caninum, rNAP5, which specifically inhibits fXa but not the TF/fVIIa complex, did not significantly inhibit primary or metastatic tumor growth, suggesting that the activity of the TF/fVIIa complex may be independent of its ability to initiate coagulation. This suggests that the TF/fVIIa complex may have a novel proangiogenic activity that is independent of its role of initiating coagulation and may function as a proangiogenic mechanism.
| MATERIALS AND METHODS |
|---|
|
|
|---|
Treatment of Primary B16 and LLC Tumor Growth.
Groups of five C57BL/6J mice were injected s.c. with 2.5 x 105 B16 melanoma cells or LLC cells. Treatments were initiated when tumors were 100 mm3 in volume and continued daily for 1012 days. Animals were treated peritumorally with 0.66 mg/kg human recombinant TFPI or i.p. with increasing amounts of rNAPc2 and rNAP5. Tumor growth was measured on alternate days, and tumor volume was calculated using the following formula: (length) x (width)2 x (
/6). Efficacy was calculated as the ratio of tumor size in the treated animals to the tumor size in control animals. Statistical analysis was performed using the Student t test.
Treatment of Experimental Pulmonary Tumor Metastasis.
B16 melanoma model. Groups of five C57BL/6J mice were inoculated with 5 x 104 B16 melanoma cells via the tail vein and subsequently treated i.p. with human TFPI, rNAPc2, rNAP5, or equal volumes of diluent control. Treatment was initiated on day 3, post-tumor cell inoculation. Animals were sacrificed and necropsied after 1014 days of treatment. The lungs were removed, and the number of pulmonary colonies was counted under a dissecting microscope (LLC spontaneous metastatic model). LLC cells (1 x 106) were injected into the hind footpad of 68-week-old males. Fourteen days later, the primary tumor was resected by amputation of the rear leg just below the head of the femur. Animals with resected tumors were treated with rNAPc2 daily after ligation. After sacrifice by CO2 asphyxiation, lungs were removed and weighed. Lung weight gain was calculated by subtracting the average lung weights of age-matched normal mice. Efficacy was calculated as above, and results were analyzed for statistical significance using the Student t test.
Matrigel Plug Assay.
Groups of 10 animals were injected s.c. at the ventral midline posterior to the xiphoid process with 0.5 ml of Matrigel (Collaborative Research) to which bFGF (final concentration of 2 µg/ml) was added. Control animals were injected with Matrigel lacking bFGF. Animals were treated daily with various amounts of rNAPc2 or buffer control. After 6 days, animals were euthanized with CO2. The Matrigel plug was removed, weighed, and frozen after the addition of 1 ml of water. Angiogenesis was quantified by homogenizing the plug and quantifying the amount of hemoglobin using the Sigma hemoglobin kit (527-A).
| RESULTS AND DISCUSSION |
|---|
|
|
|---|
|
Because TFPI inhibits coagulation by blocking the proteolytic activity of both TF/fVIIa complexes and fXa, we next sought to determine whether inhibition of either of these enzymes alone was sufficient to inhibit tumor growth. We hypothesized that if TFPIs antitumor activity was caused by inhibition of the coagulation cascade, then inhibitors of either TF/fVIIa or fXa should have identical antitumor activity. We tested this by using two small protein anticoagulants originally isolated from the hematophageous nematode A. caninum, rNAPc2, which is a specific inhibitor of TF/fVIIa (16) , and rNAP5, with specificity for fXa (17) .
rNAPc2 Inhibits Tumor Growth and Angiogenesis.
The antitumor activity of both rNAP5 and rNAPc2 was first assessed in the LLC primary tumor model. In initial experiments, mice were treated with 2.5 mg/kg/day either rNAPc2 or rNAP5 for 710 days. Under these conditions, the TF/fVIIa-specific inhibitor rNAPc2 dramatically inhibited the growth of tumors (Fig. 2A
; T/C = 0.17, P = 0.02), whereas the fXa inhibitor rNAP5 did not inhibit tumor growth (Fig. 2B
; T/C = 0.69, P = 0.22). The antitumor activity of rNAPc2 was dose dependent, with an IC50 of
0.75 mg/kg/day (data not shown). The absence of antitumor activity for rNAP5 was not attributable to inadequate or incomplete inhibition of fXa, although, since at the highest level of treatment (2.5 mg/kg/day), 40% of the animals died during the dosage period as a result of i.p. hemorrhage. Because of this high mortality, we were unable to test higher doses of rNAP5 for possible antitumor efficacy. The presence of hemorrhage confirms that rNAP5 was functional at the doses assessed and suggests that fXa activity is not necessary for the growth of primary LLC tumors.
|
|
Because TF/fVIIa complexes have been reported to regulate angiogenesis, we next assessed the activity of rNAPc2 in the Matrigel plug assay, an in vivo angiogenesis model. In this assay, rNAPc2 exhibits very potent inhibitory activity in the range of 40160 µg/kg (Fig. 4)
. At the lowest dose tested (4 µg/kg), angiogenesis was still inhibited by 57% (data not shown). At doses > 160 µg/kg, rNAPc2 caused significant hemorrhage in the Matrigel plug and adjacent tissue. The results in this model demonstrate that the TF/fVIIa activity plays an important role in stimulating angiogenesis, suggesting a possible mechanism of action for the in vivo antitumor activity of TF/fVIIa complex inhibitors.
|
In this study, we demonstrate that TF/fVIIa inhibitors have potent antitumor and antiangiogenic activity, suggesting that the proteolytic activity of the TF/fVIIa complex supports angiogenesis and tumor growth in vivo. Surprisingly, although TF/fVIIa activity is vital to these processes, we show that the proteolytic activity of fXa is not required. This suggests that the entire coagulation cascade is not necessary for tumor growth and angiogenesis. Instead, it appears that the TF/fVIIa complex is acting proteolytically through another mechanism, possibly through activation of a proteinase-activated receptor. Proteinase-activated receptors are a family of four G protein-coupled receptors that signal in response to their proteolytic cleavage by hemostatic enzymes (20) and play an important role in embryonic vascular development and hemostasis. Because these receptors signal in response to activation of coagulation, they provide a very promising target for the nonhemostatic activity of the TF/fVIIa complex (21 , 22) .
Clinical studies demonstrating potential antitumor effects of coagulation inhibitors have generated renewed interest in developing anticoagulants as antitumor agents. This goal needs to be reassessed in light of our findings, because the protumor activity of TF/fVIIa appears to be independent of its procoagulant activity. Treatment with anticoagulants may decrease TF/fVIIa activity and inhibit tumor growth; however, the level of treatment necessary to block clotting may not be adequate to block the protumor activity of the TF/fVIIa complex. In our studies, the antitumor activity of rNAPc2 was seen at doses significantly higher than necessary for anticoagulant activity in clinical trials (23) . Thus, identification of this nonhemostatic pathway of TF/fVIIa activity provides a way to completely separate the protumor and procoagulant activities of TF/fVIIa. Further characterization of this nonhemostatic pathway should allow the development of inhibitors that solely block the proangiogenic activity of TF/fVIIa, without altering its procoagulant activity.
| FOOTNOTES |
|---|
1 To whom requests for reprints should be addressed, at EntreMed, Inc., Laboratory of Discovery Research, 9640 Medical Center Drive, Rockville, MD 20850. Phone: (240) 864-2686; Fax: (204)864-2601; E-mail: toddh{at}entremed.com ![]()
2 The abbreviations used are: TF/fVIIa, tissue factor/factor VIIa; TFPI, tissue factor pathway inhibitor; T/C, treated versus control; LLC, Lewis lung carcinoma; VLDL, very low density lipoprotein; bFGF, basic fibroblast growth factor. ![]()
Received 11/15/02. Accepted 3/25/03.
| REFERENCES |
|---|
|
|
|---|
This article has been cited by other articles:
![]() |
R. S. Kasthuri, M. B. Taubman, and N. Mackman Role of Tissue Factor in Cancer J. Clin. Oncol., October 10, 2009; 27(29): 4834 - 4838. [Abstract] [Full Text] [PDF] |
||||
![]() |
J. Zhao, G. Aguilar, S. Palencia, E. Newton, and A. Abo rNAPc2 Inhibits Colorectal Cancer in Mice through Tissue Factor Clin. Cancer Res., January 1, 2009; 15(1): 208 - 216. [Abstract] [Full Text] [PDF] |
||||
![]() |
J. Yu, L. May, C. Milsom, G. M. Anderson, J. I. Weitz, J. P. Luyendyk, G. Broze, N. Mackman, and J. Rak Contribution of Host-Derived Tissue Factor to Tumor Neovascularization Arterioscler Thromb Vasc Biol, November 1, 2008; 28(11): 1975 - 1981. [Abstract] [Full Text] [PDF] |
||||
![]() |
J. S. Palumbo, K. E. Talmage, J. V. Massari, C. M. La Jeunesse, M. J. Flick, K. W. Kombrinck, Z. Hu, K. A. Barney, and J. L. Degen Tumor cell-associated tissue factor and circulating hemostatic factors cooperate to increase metastatic potential through natural killer cell-dependent and-independent mechanisms Blood, July 1, 2007; 110(1): 133 - 141. [Abstract] [Full Text] [PDF] |
||||
![]() |
H. Uusitalo-Jarvinen, T. Kurokawa, B. M. Mueller, P. Andrade-Gordon, M. Friedlander, and W. Ruf Role of Protease Activated Receptor 1 and 2 Signaling in Hypoxia-Induced Angiogenesis Arterioscler Thromb Vasc Biol, June 1, 2007; 27(6): 1456 - 1462. [Abstract] [Full Text] [PDF] |
||||
![]() |
A. A. Khorana, S. A. Ahrendt, C. K. Ryan, C. W. Francis, R. H. Hruban, Y. C. Hu, G. Hostetter, J. Harvey, and M. B. Taubman Tissue Factor Expression, Angiogenesis, and Thrombosis in Pancreatic Cancer Clin. Cancer Res., May 15, 2007; 13(10): 2870 - 2875. [Abstract] [Full Text] [PDF] |
||||
![]() |
X. Li, E. Calvo, M. Cool, P. Chrobak, D. G. Kay, and P. Jolicoeur Overexpression of Notch1 Ectodomain in Myeloid Cells Induces Vascular Malformations through a Paracrine Pathway Am. J. Pathol., January 1, 2007; 170(1): 399 - 415. [Abstract] [Full Text] [PDF] |
||||
![]() |
S. Koizume, M.-S. Jin, E. Miyagi, F. Hirahara, Y. Nakamura, J.-H. Piao, A. Asai, A. Yoshida, E. Tsuchiya, W. Ruf, et al. Activation of Cancer Cell Migration and Invasion by Ectopic Synthesis of Coagulation Factor VII Cancer Res., October 1, 2006; 66(19): 9453 - 9460. [Abstract] [Full Text] [PDF] |
||||
![]() |
M. F. McCarty and K. I. Block Toward a Core Nutraceutical Program for Cancer Management Integr Cancer Ther, June 1, 2006; 5(2): 150 - 171. [Abstract] [PDF] |
||||
![]() |
L. Y. Han, C. N. Landen Jr, A. A. Kamat, A. Lopez, D. P. Bender, P. Mueller, R. Schmandt, D. M. Gershenson, and A. K. Sood Preoperative Serum Tissue Factor Levels Are an Independent Prognostic Factor in Patients With Ovarian Carcinoma J. Clin. Oncol., February 10, 2006; 24(5): 755 - 761. [Abstract] [Full Text] [PDF] |
||||
![]() |
M. Belting, J. Ahamed, and W. Ruf Signaling of the Tissue Factor Coagulation Pathway in Angiogenesis and Cancer Arterioscler Thromb Vasc Biol, August 1, 2005; 25(8): 1545 - 1550. [Abstract] [Full Text] [PDF] |
||||
![]() |
A. G. Olivero, C. Eigenbrot, R. Goldsmith, K. Robarge, D. R. Artis, J. Flygare, T. Rawson, D. P. Sutherlin, S. Kadkhodayan, M. Beresini, et al. A Selective, Slow Binding Inhibitor of Factor VIIa Binds to a Nonstandard Active Site Conformation and Attenuates Thrombus Formation in Vivo J. Biol. Chem., March 11, 2005; 280(10): 9160 - 9169. [Abstract] [Full Text] [PDF] |
||||
![]() |
C. Sass, C. Blanquart, P.-E. Morange, M. Pfister, and S. Visvikis-Siest Association Between Factor VII Polymorphisms and Blood Pressure: The Stanislas Cohort Hypertension, November 1, 2004; 44(5): 674 - 680. [Abstract] [Full Text] [PDF] |
||||
![]() |
A. Dorfleutner, E. Hintermann, T. Tarui, Y. Takada, and W. Ruf Cross-talk of Integrin {alpha}3{beta}1 and Tissue Factor in Cell Migration Mol. Biol. Cell, October 1, 2004; 15(10): 4416 - 4425. [Abstract] [Full Text] [PDF] |
||||
![]() |
T. A. Hembrough, J. F. Ruiz, B. M. Swerdlow, G. M. Swartz, H. J. Hammers, L. Zhang, S. M. Plum, M. S. Williams, D. K. Strickland, and V. S. Pribluda Identification and characterization of a very low density lipoprotein receptor-binding peptide from tissue factor pathway inhibitor that has antitumor and antiangiogenic activity Blood, May 1, 2004; 103(9): 3374 - 3380. [Abstract] [Full Text] [PDF] |
||||
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| Cancer Research | Clinical Cancer Research |
| Cancer Epidemiology Biomarkers & Prevention | Molecular Cancer Therapeutics |
| Molecular Cancer Research | Cancer Prevention Research |
| Cancer Prevention Journals Portal | Cancer Reviews Online |
| Annual Meeting Education Book | Meeting Abstracts Online |