| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
Experimental Therapeutics |
Molecular Pharmacology Section, Cancer Therapeutics Branch, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, Maryland 20892 [S. S. W. N., E. A. K., W. D. F.]; Pharmaceutical Institute, Poppelsdorf, University of Bonn, Bonn, Germany [M. G.]; Institute of Pharmacy, Pharmaceutical Chemistry [M. W., U. T., T. K. H., K. E.] and Institute of Zoology, Department of Immunobiology [S. H.], University of Leipzig, Leipzig, Germany; and Department of Chemistry, University of Louisville, Louisville, Kentucky [F. A. L.]
| ABSTRACT |
|---|
|
|
|---|
| INTRODUCTION |
|---|
|
|
|---|
-(N-phthalimido)-glutarimide] was first released in Europe and Canada as a rapid-acting, hangover-free sedative in 1956. Reports on phocomelia in infants of women who had taken thalidomide during pregnancy started to surface a few years later (1
, 2)
, leading to its withdrawal from the market. Despite its teratogenicity, thalidomide was approved by the United States Food and Drug Administration in 1998 as a treatment for erythema nodosum leprosum. The clinical efficacy of thalidomide in inflammatory and autoimmune diseases was in part attributed to its ability to inhibit TNF-
2
production (3, 4, 5)
. Over 30 years ago, Folkman (6) pioneered the notion that solid tumors cannot grow beyond 23 mm3 without the formation of new blood vessels. Inhibition of angiogenesis has been thereafter perceived as a promising strategy to treat cancer. DAmato et al. (7) demonstrated that thalidomide inhibits basic fibroblast growth factor-induced angiogenesis in the rabbit cornea and tumor growth in rabbits. Subsequently, the antitumor activity of thalidomide was evaluated in numerous clinical trials. Partial response, stable disease, or tumor regression was reported in patients with multiple myeloma (8, 9, 10) , AIDS-related Kaposis sarcoma (11) , high-grade gliomas (12) , hepatocellular carcinoma (13 , 14) , renal cell carcinoma (15 , 16) , and advanced melanoma (15) . In androgen-independent prostate cancer, thalidomide caused a reduction in serum prostate-specific antigen and an improvement of clinical symptoms (17) .
Our laboratory showed previously that one of the products of cytochrome P450 2C19 isozyme biotransformation of thalidomide, 5'-OH-thalidomide, is responsible for the drugs antiangiogenic activity (18, 19, 20)
. On the basis of the structure of the metabolite, we synthesized 118 thalidomide analogues and studied their structureactivity relationship in multiple angiogenesis assays. All analogues were preliminarily screened at 100 µM in the rat aortic ring assay. Seven of the 118 analogues were chosen because they demonstrated the highest efficacy. To our knowledge, thalidomide analogues synthesized by various groups were mostly tested for their ability to inhibit TNF-
production in monocytes (21, 22, 23)
. The current study investigated the effects of 7 of the 118 analogues from the N-substituted and tetrafluorinated classes on rat aortic microvessel outgrowth, HUVECs, and prostate cancer cells. Representative analogues from each class were also tested for in vivo toxicity.
| MATERIALS AND METHODS |
|---|
|
|
|---|
|
Cell Lines.
HUVECs (Clonetics) were maintained in EGM-II at 37°C and 5% CO2. Human prostate cancer cell lines PC3 and LNCaP were obtained from the American Type Culture Collection (Manassas, VA). Cells were maintained at 37°C and 5% CO2 in RPMI 1640 supplemented with 10% fetal bovine serum and antibiotics (100 units/ml penicillin, 100 µg/ml streptomycin, and 0.25 µg/ml amphotericin B).
Cell Proliferation Assay.
HUVECs, PC3, and LNCaP cells were seeded onto 12-well plates at a density of 30,000; 30,000; and 40,000 cells/well, respectively, and allowed to attach overnight at 37°C and 5% CO2. The culture medium was then aspirated, and fresh culture medium containing either the vehicle (0.5% DMSO), thalidomide, CPS11, CPS16, CPS20, CPS45, CPS48, CPS49 (12.5200 µM), or CPS13 (25400 µM) was added to each well every 24 h. After 48 h, cells were trypsinized and counted with a Coulter Z1 counter (Coulter Corp., Hialeah, FL). All experiments were done in duplicate and repeated three times.
Endothelial Cell Tube Formation Assay.
Eight-well slide chambers were coated with 150 µl of Matrigel and allowed to gel at 37°C and 5% CO2 for 30 min. HUVECs were then seeded at 30,000 cells/well in EGM-II containing either the vehicle (0.5% DMSO), thalidomide, CPS11, CPS16, CPS20, CPS45, CPS48, CPS49 (12.5200 µM), or CPS13 (25400 µM) and incubated at 37°C and 5% CO2 for 16 h. After incubation, slides were washed in PBS, fixed in 100% methanol for 10 s, and stained with DiffQuick solution II (Dade Behring, Inc., Newark, DE) for 2 min. To analyze tube formation, each well was digitally photographed using a x2.5 objective. A threshold level was set to mask the stained tubes. The corresponding area was measured as the number of pixels using the MetaMorph software (Universal Imaging, Downingtown, PA). Experiments were repeated three times.
Human Saphenous Vein Assay.
Specimens of human saphenous vein were harvested during the course of surgery on an institution-approved protocol. Veins were cut into 2-mm-long cross-sections; cultured under similar conditions as described for the rat aortic rings; treated daily with CPS11, CPS13, CPS16, CPS20, CPS45, and CPS49 at 100 µM for 13 days; and photographed on the 14th day using a x1.5 objective. Images were analyzed as described above.
In Vivo Toxicity Study.
Twelve-week-old male nude mice were given daily i.p. injections of either the vehicle (0.5% carboxymethylcellulose), CPS11, CPS45, or CPS49 at 12.5200 mg/kg for 2 weeks. Five animals were included in each dose group. Maximum tolerated dose of each analogue was determined. Necropsy was performed on the survivors from each dose group by veterinary pathologists.
Statistics.
All results were presented as mean ± SE. Comparisons were made with one-way ANOVA followed by Dunnetts test with P < 0.05 as the criterion for statistical significance.
| RESULTS |
|---|
|
|
|---|
90% inhibition of angiogenesis, comparable with CAI. Fig. 2B
|
|
|
|
|
|
In Vivo Toxicity of Thalidomide Analogues.
As shown in Fig. 8A
, all mice injected with CPS11 at 12.5100 mg/kg survived the 2-week daily treatment schedule. Mortality was 20% after four doses of the compound at 200 mg/kg. Fig. 8B
demonstrated the much higher toxicity of CPS49 relative to CPS11. All mice given CPS49 at 50200 mg/kg died within 4 days of treatment. CPS49 at 25 mg/kg caused 20% mortality. When given at 12.5 mg/kg, all mice survived the treatment regimen. The maximum tolerated doses of CPS11 and CPS49 were determined to be 100 and 12.5 mg/kg, respectively. For CPS49 at 25 and 12.5 mg/kg, the major histopathology included chronic inflammation of the pancreas, the epididymis, and some accessory male sex glands, increased extramedullary hematopoiesis in the spleen, as well as granulocytic hyperplasia in the bone marrow. CPS11 at 200 and 100 mg/kg was associated with granulocytic hyperplasia in the bone marrow and increased incidence of minimal to mild nephropathy. Surprisingly, all mice injected with the other tetrafluorinated analogue CPS45, which also showed high potency in vitro, at 12.5200 mg/kg survived the 2-week treatment regimen (data not shown). The administration of CPS45 was associated with histiocytosis in lymph nodes.
|
| DISCUSSION |
|---|
|
|
|---|
production in human monocytes. Parallel to our findings, CPS45 and CPS49 at 25 µM were shown to completely suppress TNF-
production, whereas CPS48 failed to do so. This suggests that tetrafluoro substitution at the phthalimido ring is crucial but not sufficient for potent angiogenesis and TNF-
inhibitory actions. Being a polar isostere of CPS49, the lack of biological activity of CPS48 might be attributed to its decreased lipophilicity. Niwayama et al. (21)
reported that the increase in potency of the tetrafluorothalidomides with regard to TNF-
inhibition is unique to fluorine substitution as other halogen atoms fail to produce similar effects. Replacement of the imido hydrogen in the glutarimide ring (N-substitution) with the current moieties also generated analogues with reasonable, albeit less potent, antiangiogenic activity. In general, fluorine-containing molecules are much more hydrophobic and, therefore, more bioactive compared with their hydrocarbon counterparts. It has also been suggested that fluorine substitution confers stereoelectronic changes to drug molecules and, in turn, stronger binding to biological targets (25)
. These in vitro data were reverberated in the much lower maximum tolerated dose of CPS49 (12.5 mg/kg) compared with CPS11 (100 mg/kg). The relative lack of in vivo lethal toxicity of CPS45 (200 mg/kg), which demonstrated similar potency to CPS49 in vitro, was unexpected and remains to be understood. Contrary to the analogues, thalidomide itself failed to suppress rat aortic angiogenesis and HUVEC proliferation, consistent with previous reports which showed that thalidomide metabolites are responsible for the pharmacological actions of the drug (18
, 19)
. It is unclear, however, why thalidomide exhibited activity in the tube formation assay. The differential sensitivity of rat aorta and human vein to the antiangiogenic effects of the thalidomide analogues demonstrates the importance of using multiple systems in the preclinical screening of new compounds.
The precise mechanisms of action of thalidomide and its analogues are not completely understood. Thalidomide has been shown to alleviate inflammatory processes by enhancing TNF-
mRNA degradation (4)
. Kenyon et al. (26)
reported that thalidomide, but not strong TNF-
inhibitors, blocks basic fibroblast growth factor-induced angiogenesis, suggesting that the antiangiogenic action of thalidomide may be mediated by TNF-
-independent pathways in the mouse cornea model. However, the tumor microenvironment, with infiltrating macrophages as the source of TNF-
, is much more complex. It remains to be determined whether TNF-
is involved in thalidomide-induced antiangiogenicity in solid malignancies.
COX-2, an inducible enzyme with a role in carcinogenesis and angiogenesis (27, 28, 29)
, has been recently described as another target of thalidomide and its analogues (30)
. Fujita et al. (31)
showed that thalidomide and its analogues reduce prostaglandin E2 production in the murine macrophage-like cell line RAW 264.7 by decreasing the stability of COX-2 mRNA. Subsequently, it has been demonstrated that introduction of different substituents at different positions of the phthalimido ring differentially changes the selectivity of the analogues for COX-1 and COX-2 (30)
. Taken together, future design of antiangiogenic thalidomide analogues should aim at generating or optimizing structures which possess both TNF-
and COX-2 inhibitory actions. It is important to note that thalidomide and its analogues may not necessarily share similar mechanisms of action. Indeed, Niwayama et al. provided evidence that nonfluorinated and fluorinated phthalimides inhibit cytokine production through interaction with distinct target proteins (25)
.
In summary, we have shown that thalidomide analogues inhibit rat aortic and human venous microvessel outgrowth as well as HUVEC proliferation and tube formation, further supporting the preclinical and clinical development of these compounds as angiogenesis inhibitors. The in vivo antiangiogenic and antitumor activities of our thalidomide analogues in prostate cancer are currently being investigated.
| ACKNOWLEDGMENTS |
|---|
| FOOTNOTES |
|---|
1 To whom requests for reprints should be addressed, at Molecular Pharmacology Section, National Cancer Institute, NIH, Building 10, Room 5A01, MSC 1910, 9000 Rockville Pike, Bethesda, MD 20892. Phone: (301) 402-3622; Fax: (301) 402-8606; E-mail: wdfigg{at}helix.nih.gov ![]()
2 The abbreviations used are: TNF, tumor necrosis factor; CAI, carboxyamidotriazole; COX, cyclooxygenase; HUVEC, human umbilical vein endothelial cell. ![]()
Received 11/15/02. Accepted 4/17/03.
| REFERENCES |
|---|
|
|
|---|
production in vitro. Bioorg. Med. Chem., 9: 1059-1065, 2001.[Medline]
This article has been cited by other articles:
![]() |
C. Therapontos, L. Erskine, E. R. Gardner, W. D. Figg, and N. Vargesson Thalidomide induces limb defects by preventing angiogenic outgrowth during early limb formation PNAS, May 26, 2009; 106(21): 8573 - 8578. [Abstract] [Full Text] [PDF] |
||||
![]() |
Y. Ge, J. S. Byun, P. De Luca, G. Gueron, I. M. Yabe, S. G. Sadiq-Ali, W. D. Figg, J. Quintero, C. M. Haggerty, Q. Q. Li, et al. Combinatorial Antileukemic Disruption of Oxidative Homeostasis and Mitochondrial Stability by the Redox Reactive Thalidomide 2-(2,4-Difluoro-phenyl)-4,5,6,7-tetrafluoro-1H-isoindole-1,3(2H)-dione (CPS49) and Flavopiridol Mol. Pharmacol., September 1, 2008; 74(3): 872 - 883. [Abstract] [Full Text] [PDF] |
||||
![]() |
S. H. Hwang, A. Rait, K. F. Pirollo, Q. Zhou, V. M. Yenugonda, G. M. Chinigo, M. L. Brown, and E. H. Chang Tumor-targeting nanodelivery enhances the anticancer activity of a novel quinazolinone analogue Mol. Cancer Ther., March 1, 2008; 7(3): 559 - 568. [Abstract] [Full Text] [PDF] |
||||
![]() |
Y. Ge, I. Montano, G. Rustici, W. J. Freebern, C. M. Haggerty, W. Cui, D. Ponciano-Jackson, G. V. R. Chandramouli, E. R. Gardner, W. D. Figg, et al. Selective leukemic-cell killing by a novel functional class of thalidomide analogs Blood, December 15, 2006; 108(13): 4126 - 4135. [Abstract] [Full Text] [PDF] |
||||
![]() |
A. B. Moy, K. Blackwell, M. H. Wu, and H. J. Granger Growth factor- and heparin-dependent regulation of constitutive and agonist-mediated human endothelial barrier function Am J Physiol Heart Circ Physiol, November 1, 2006; 291(5): H2126 - H2135. [Abstract] [Full Text] [PDF] |
||||
![]() |
N. A. Warfel, E. R. Lepper, C. Zhang, W. D. Figg, and P. A. Dennis Importance of the Stress Kinase p38{alpha} in Mediating the Direct Cytotoxic Effects of the Thalidomide Analogue, CPS49, in Cancer Cells and Endothelial Cells. Clin. Cancer Res., June 1, 2006; 12(11): 3502 - 3509. [Abstract] [Full Text] [PDF] |
||||
![]() |
T. Yabu, H. Tomimoto, Y. Taguchi, S. Yamaoka, Y. Igarashi, and T. Okazaki Thalidomide-induced antiangiogenic action is mediated by ceramide through depletion of VEGF receptors, and is antagonized by sphingosine-1-phosphate Blood, July 1, 2005; 106(1): 125 - 134. [Abstract] [Full Text] [PDF] |
||||
![]() |
S. S. W. Ng, G. R. MacPherson, M. Gutschow, K. Eger, and W. D. Figg Antitumor Effects of Thalidomide Analogs in Human Prostate Cancer Xenografts Implanted in Immunodeficient Mice Clin. Cancer Res., June 15, 2004; 10(12): 4192 - 4197. [Abstract] [Full Text] [PDF] |
||||
![]() |
J. M. Rogers and B. D. Abbott Screening for Developmental Toxicity of Tobacco Smoke Constituents Toxicol. Sci., October 1, 2003; 75(2): 227 - 228. [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 |