| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
Experimental Therapeutics |
Departments of Biochemistry [R. P. M. D., K. H. M.] and Pharmacology [Y. Y., S. R.], University of Minnesota Health Sciences Center, Minneapolis, Minnesota 55455, and Tumor Angiogenesis Laboratory, Department of Internal Medicine, University Hospital Maastricht, 6202 AZ Maastricht, the Netherlands [R. P. M. D., A. W. G.]
| ABSTRACT |
|---|
|
|
|---|
| INTRODUCTION |
|---|
|
|
|---|
| MATERIALS AND METHODS |
|---|
|
|
|---|
Culture.
MA148, a human epithelial ovarian carcinoma cell line, was cultured on noncoated flasks using 10% fetal bovine serum, 1% penicillin/streptomycin in RPMI 1640. Cultures were split 1:3 every 3 days. Mouse angiostatin (kringle 1-4) was cloned and expressed in Pichia pastoris (10)
, with culturing, elution, and purification done as described previously (9
, 11)
.
Ovarian Carcinoma Mouse Model.
Female athymic nude mice (nu/nu, 56 weeks old) were purchased from the National Cancer Institute and allowed to acclimatize for 1 week. Human ovarian MA148 epithelial carcinoma cells were cultured, harvested, and inoculated s.c. into the right flank of the mouse as described previously (9)
. In the initial experiment, treatment was initiated after randomizing mice and implanting osmotic minipumps (Durect, Cupertino, CA) into the left flank. The pumps had a treatment span of 28 days, which started on the same day as the inoculation of the ovarian carcinoma cells. Subsequently, studies were carried out in a therapeutic intervention model with established tumors to test the capacity of anginex to inhibit tumor growth and to test it in conjunction with angiostatin. In this latter model, treatment was initiated 7 days postinoculation with the MA148 cells. To test the ability of anginex to enhance conventional chemotherapy, carboplatin was used in combination with anginex in the same intervention model.
Tumor volume was determined by measuring the size of the tumors on the flanks of the mice. The diameters of tumors were measured using calipers (Scienceware, Pequannock, NJ), and the volume was calculated using the equation to determine the volume of a spheroid: (a2 x b x
)/6, where a is the width of the tumor, and b is the length of the tumor.
Immunohistochemistry.
Tumor tissues were embedded in tissue freezing medium (Miles, Inc., Elkart, IN) and snap frozen in liquid nitrogen. Preparation and procedures were done as described previously (12)
. Samples were subsequently incubated in a 1:50 dilution with phycoerythrin-conjugated monoclonal antibody to mouse CD-31 (platelet/endothelial cell adhesion molecule 1; PharMingen, San Diego, CA) or a FITC-conjugated PCNA3
(Ab-1; Oncogene, San Diego, CA) to stain for MVD or proliferation, respectively. After a 1-h incubation at room temperature, slides were washed with PBS and immediately imaged in an Olympus BX-60 fluorescence microscope at x200 magnification. Sections were also stained for cell death using a TUNEL assay carried out according to the manufacturers instructions (in situ cell death detection kit, fluorescein; TUNEL; Roche). Although the TUNEL assay detects apoptosis, it cannot be ruled out that TUNEL will also stain for necrosis, where extensive DNA fragmentation may occur. Digital images were acquired and processed using Adobe Photoshop (Adobe Inc., Mountain View, CA). Vessel density was quantified as described previously (12)
. Statistical analysis was performed using Students t test.
Toxicity Assays.
As an indirect measurement of general toxicity, body weights of mice were monitored twice weekly using a digital balance (Ohaus Florham). To determine hematocrit and creatinine levels, blood samples were extracted by tail vein bleedings 1 day after terminating treatment, and blood was collected in heparinized microhematocrit capillary tubes (Fisher, Pittsburgh, PA). For hematocrit levels, samples were spun down for 10 min in a microhematocrit centrifuge (Clay-Adams), and the amount of hematocrit was determined using an international microcapillary reader (IEC, Needham, MA). To obtain creatinine levels, a kit was purchased from Sigma Diagnostics and used according to the manufacturers instructions.
| RESULTS |
|---|
|
|
|---|
|
|
Anginex and Angiostatin Act Synergistically to Inhibit Tumor Growth.
Using optimized treatment regimes for angiostatin (9)
and anginex, we found that both anginex and angiostatin, administered separately, inhibited tumor growth comparably by approximately 50% in the same ovarian tumor model. On the basis of those findings, the interaction between angiostatin and anginex was examined. Combination therapy of angiostatin with anginex resulted in enhanced tumor growth inhibition (80%; Fig. 2B
), which was deemed to be synergistic (Table 1)
.
|
Histological Analysis of MVD, Cell Death, and Proliferation.
Anginex treatment resulted in a decrease of tumor MVD, suggesting that the antitumor activity of anginex is the result of angiogenesis inhibition. Angiostatin demonstrated a similar result. Although anginex and angiostatin acted synergistically on tumor growth inhibition, this was not reflected in the MVD assessment (Fig. 3B)
. Aside from vessel density (including number, size, and length; see Ref. 12
), the digital approach discriminates branch points, end points, and vessel lengths. Some of these architectural parameters did change in combination treatment relative to single-agent treatment. For example, combination treatment revealed a synergistic reduction in the number of branch points (data not shown). Tumors from anginex-treated animals showed a convincing MVD reduction (P < 0.01), whereas tumors from carboplatin-treated animals showed a smaller, albeit significant, MVD reduction (P < 0.05; Fig. 3A
). Tumors treated with the combination of anginex and carboplatin could not be stained because all tumors disappeared 3 weeks after initiation of treatment.
|
| DISCUSSION |
|---|
|
|
|---|
Because antiangiogenic agents can potentiate cytotoxic cancer therapies (7) , anginex was tested in combination with the chemotherapeutic carboplatin. Platinum agents are the most widely used drugs in the first line of defense against ovarian cancer (14 , 15) . In a recent study, single-agent carboplatin proved to be just as effective as carboplatin plus paclitaxel in women requiring chemotherapy for ovarian cancer. The favorable toxicity profile of carboplatin alone suggested that this is a reasonable option as a single-agent chemotherapeutic (16) . An additional advantage of carboplatin is that, in contrast to other agents such as taxanes cyclophosphamide and vincristine, it is not an antiangiogenic by itself. Because carboplatin has been shown to be a very powerful anticancer drug in the model used here, a suboptimal dose was used. Both anginex and carboplatin inhibited tumor growth, but the combination of the two blocked tumor growth completely, and palpable tumors regressed to undetectable sizes in all animals. Moreover, tumors remained undetectable until at least 1 week after termination of the treatment, after which tumors reestablished themselves, indicating the continued presence of microscopic disease, which was unresponsive to carboplatin and apparently independent of angiogenesis.
Whereas numerous investigators have focused on the anticancer effects from endostatin in their tumor model studies, we chose to use angiostatin because in the same MA148 tumor mouse model, Yokoyama et al. (9) found that angiostatin was considerably more effective at inhibiting tumor growth than endostatin. Here, we found that although treatment with angiostatin or anginex showed essentially the same capacity to inhibit tumor growth, combination of the two produced a dramatically enhanced inhibitory effect. This synergy between angiostatin and anginex suggests that their mechanisms of action are different and that they can augment each other as antiangiogenic agents. These data, therefore, provide a validation for combination therapy, if not for mixtures of angiogenesis inhibitors, to improve the treatment of cancer.
Immunohistochemical assessment of MVD indicated that tumor growth inhibition by anginex is explained by its antiangiogenic activity. Angiostatin showed the same trend. Combination therapy, however, did not yield an increased MVD reduction. This may be explained by the fact that differences in architecture are not represented in the MVD value assessed either digitally or manually. The digital approach discriminates for architectural parameters, some of which did change in combination treatment relative to single-agent treatment. For example, combination treatment revealed a synergistic reduction in the number of branch points (data not shown).
This study adds credence to the proposal that cancer treatment using antiangiogenesis agents is more effective when performed in combination with other agents. However, it might be that only mixtures of antiangiogenic compounds would provide sufficient potency to be evaluated properly in early clinical trials. Currently, clinical evaluation of antiangiogenic compounds is in its infancy, and although a stand-alone approach using an antiangiogenic agent shows promise, combination therapy may provide for the best evaluation of these agents and, in the end, may be more beneficial. The present results suggest that combination of antiangiogenic agents with chemotherapeutic agents will produce a greater effect than combinations of antiangiogenic agents alone. At the very least, this study indicates that combining the antiangiogenic compound anginex with conventional chemotherapy allows the dosage of the chemotherapeutic to be reduced while maintaining the ability to effect tumor growth reduction.
| ACKNOWLEDGMENTS |
|---|
| FOOTNOTES |
|---|
1 Supported by Department of Defense Grant DA/DAMD 17-99-1-9564 (to K. H. M. and S. R.) and NIH Grant CA-96090 (to K. H. M.). ![]()
2 To whom requests for reprints should be addressed, at Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota Health Sciences Center, 312 Church Street, Minneapolis, MN 55455. Phone: (612) 625-9968; Fax: (612) 624-5121; E-mail: mayox001{at}tc.umn.edu ![]()
3 The abbreviations used are: PCNA, proliferating cell nuclear antigen; MVD, microvessel density; TUNEL, terminal deoxynucleotidyl transferase-mediated nick end labeling. ![]()
Received 9/11/02. Accepted 11/14/02.
| REFERENCES |
|---|
|
|
|---|
This article has been cited by other articles:
![]() |
Y. Chen, N. Guggisberg, M. Jorda, A. Gonzalez-Angulo, B. Hennessy, G. B. Mills, C.-K. Tan, and J. M. Slingerland Combined Src and Aromatase Inhibition Impairs Human Breast Cancer Growth In vivo and Bypass Pathways Are Activated in AZD0530-Resistant Tumors Clin. Cancer Res., May 15, 2009; 15(10): 3396 - 3405. [Abstract] [Full Text] [PDF] |
||||
![]() |
R. P.M. Dings, M. Loren, H. Heun, E. McNiel, A. W. Griffioen, K. H. Mayo, and R. J. Griffin Scheduling of Radiation with Angiogenesis Inhibitors Anginex and Avastin Improves Therapeutic Outcome via Vessel Normalization Clin. Cancer Res., June 1, 2007; 13(11): 3395 - 3402. [Abstract] [Full Text] [PDF] |
||||
![]() |
M. R. Horsman and D. W. Siemann Pathophysiologic Effects of Vascular-Targeting Agents and the Implications for Combination with Conventional Therapies Cancer Res., December 15, 2006; 66(24): 11520 - 11539. [Abstract] [Full Text] [PDF] |
||||
![]() |
V. L. J. L. Thijssen, R. Postel, R. J. M. G. E. Brandwijk, R. P. M. Dings, I. Nesmelova, S. Satijn, N. Verhofstad, Y. Nakabeppu, L. G. Baum, J. Bakkers, et al. Galectin-1 is essential in tumor angiogenesis and is a target for antiangiogenesis therapy PNAS, October 24, 2006; 103(43): 15975 - 15980. [Abstract] [Full Text] [PDF] |
||||
![]() |
J. R. van Beijnum, R. P. Dings, E. van der Linden, B. M. M. Zwaans, F. C. S. Ramaekers, K. H. Mayo, and A. W. Griffioen Gene expression of tumor angiogenesis dissected: specific targeting of colon cancer angiogenic vasculature Blood, October 1, 2006; 108(7): 2339 - 2348. [Abstract] [Full Text] [PDF] |
||||
![]() |
R. P. M. Dings, X. Chen, D. M. E. I. Hellebrekers, L. I. van Eijk, Y. Zhang, T. R. Hoye, A. W. Griffioen, and K. H. Mayo Design of Nonpeptidic Topomimetics of Antiangiogenic Proteins With Antitumor Activities. J Natl Cancer Inst, July 5, 2006; 98(13): 932 - 936. [Abstract] [Full Text] [PDF] |
||||
![]() |
N. Papo, D. Seger, A. Makovitzki, V. Kalchenko, Z. Eshhar, H. Degani, and Y. Shai Inhibition of tumor growth and elimination of multiple metastases in human prostate and breast xenografts by systemic inoculation of a host defense-like lytic Peptide. Cancer Res., May 15, 2006; 66(10): 5371 - 5378. [Abstract] [Full Text] [PDF] |
||||
![]() |
A. E. M. Dirkx, M. G. A. oude Egbrink, K. Castermans, D. W. J. van der Schaft, V. L. J. L. Thijssen, R. P. M. Dings, L. Kwee, K. H. Mayo, J. Wagstaff, J. C. A. B. ter Steege, et al. Anti-angiogenesis therapy can overcome endothelial cell anergy and promote leukocyte-endothelium interactions and infiltration in tumors FASEB J, April 1, 2006; 20(6): 621 - 630. [Abstract] [Full Text] [PDF] |
||||
![]() |
H.-Y. Lee, S.-H. Oh, Y.-A. Suh, J. H. Baek, V. Papadimitrakopoulou, S. Huang, and W. K. Hong Response of Non-Small Cell Lung Cancer Cells to the Inhibitors of Phosphatidylinositol 3-Kinase/Akt- and MAPK Kinase 4/c-Jun NH2-Terminal Kinase Pathways: An Effective Therapeutic Strategy for Lung Cancer Clin. Cancer Res., August 15, 2005; 11(16): 6065 - 6074. [Abstract] [Full Text] [PDF] |
||||
![]() |
K. H. Mayo, R. P. M. Dings, C. Flader, I. Nesmelova, B. Hargittai, D. W. J. van der Schaft, L. I. van Eijk, D. Walek, J. Haseman, T. R. Hoye, et al. Design of a Partial Peptide Mimetic of Anginex with Antiangiogenic and Anticancer Activity J. Biol. Chem., November 14, 2003; 278(46): 45746 - 45752. [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 |