Warfarin inhibits both procoagulant activity and metastatic capacity of Lewis Lung Carcinoma cells

George²

1989

Br J Cancer

Summary Coumarin anticoagulants inhibit metastasis in several animal models, but the mechanism of this effect is uncertain. In order to determine the role of cytotoxic and/or cytostatic actions of coumarins on the tumour cells, we have studied the effects of warfarin on tumour cell growth in a model in which tumour metastasis is inhibited by this drug. Clonogenic assay, growth curve analysis and thymidine labelling index revealed that warfarin had no effects on Mtln3 mammary carcinoma cell growth in vitro at concentrations below 1 mm. The growth rate of subcutaneously implanted Mtln3 tumour deposits in female F344 rats, assessed by weight and by stathmokinetic analysis of the tumour tissue, was identical in warfarin-treated and control animals. Spontaneous metastasis from such tumours to the lungs was, however, significantly reduced in warfarin-treated animals (median 0 pulmonary tumours per animal in warfarin treated, eight tumours per animal in control animals; P<0.05, Mann-Whitney). The mean plasma warfarin concentration in warfarin treated rats was 1.63 M. These results suggest that warfarin treatment of the host animal can inhibit tumour metastasis without having any direct or indirect effect on the growth rate of the tumour cells.Current theories (Hart, 1980;Poste & Fidler, 1980) view metastasis as a multistep process in which successive obstacles are overcome by a small subpopulation of tumour cells capable of doing so. Each step requires different properties, and each influences subsequent steps. This complex process cannot be studied as a single unit, but requires subdivision: one way in which this can be achieved is to study influences that increase or decrease metastasis, and to attempt to define the point at which they have their effect. The coumarin group of anticoagulant drugs, including warfarin, represent an example of such an influence. Coumarins inhibit metastasis in several animal models (Ryan et al., 1969;Brown, 1973;Hilgard et al., 1977;Williamson et al., 1980). There is an extensive literature documenting the existing of coagulation disturbances in human cancer (Davis et al., 1969;Sun et al., 1979;Rickles & Edwards, 1983; Mannucci et al., 1985), and suggestive evidence of a role for coagulation in the spread and growth of tumours (Dvorak et al., 1979; Goeting et al., 1985;McCulloch & George, 1987 (Colucci et al., 1983). The possibility that coumarins have cytotoxic properties has been investigated in several different models (Boulos, 1971;Higashi & Heidelberger, 1971;Brown, 1973;Chang & Hall, 1973;Dolfini et al., 1979;McNeil et al., 1984) with diverse results. The variety of models employed and the frequent use of in vitro measures of cytotoxicity without reference to the effects of the drugs in vivo make interpretation of these studies particularly difficult. Several studies have noted a possible suppressive effect of coumarin treatment on primary tumour growth (Ryan et al., 1968(Ryan et al., , 1969Hilgard et al., 1977), but have used only crude methods which are prone to random error. On...

Section: Discussioncontrasting

confidence: 54%

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confidence: 99%

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confidence: 99%

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confidence: 99%

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Warfarin inhibits metastasis of Mtln3 rat mammary carcinoma without affecting primary tumour growth

George²

1989

Br J Cancer

“…Certain tumour cells have been shown to produce a vitamin K dependent cysteine protease procoagulant (CP) which directly activates factor X (Gordon et al, 1975), and which may be implicated in the process of metastasis (Colucci et al, 1983). Such a molecule might be activated by injections containing factor X, and a modification of the method of Gordon was therefore used to measure the procoagulant capacity of cultured Mtln3 cells.…”

Section: Discussionmentioning

confidence: 99%

Promotion of metastasis by a specific complex of coagulation factors may be independent of fibrin formation

George²

1988

Br J Cancer

Summary Coumarins inhibit metastasis in a number of animal models, but the mechanism of this effect remains unclear. We have investigated the relationship between the coagulation system and metastasis using a new model system, involving i.v. injection of Mtln3 rat mammary carcinoma cells into Fischer 344 rats, and subsequent estimation of pulmonary seeding.Injection of factors II, VII, IX and X elevated the median number of surface pulmonary seedlings per animal to 182, and injection of factors II, IX and X to 181, compared with a median for control animals of 12 (P<0.001). Injection of factor VII alone, or of bovine serum albumin did not significantly affect pulmonary seeding. In a second experiment, arvin defibrination reduced the mean plasma fibrinogen concentration to 76.8mgdl-1 from a control value of 228mgdl-1. This degree of defibrination had no significant effects on pulmonary seeding, nor on the enhancing effects of factor complex injection (median numbers of seedlings per animal; control 15, arvin 21, arvin plus factors II, VII, IX and X 170, factors II, VII, IX and X only, 157). Factor complex injections did not detectably shorten thrombotest clotting times. In vitro testing suggested that Mtln3 cells contain little or no conventional factor X activating cancer procoagulant.The complex of coagulation factors II, IX and X appears to contain a component which greatly enhances metastasis in this model. This may explain the previously reported antimetastatic effect of coumarin anticoagulants, which suppress factors II, VII, IX and X. The enhancing effect of the factor complex does not appear to be altered by significant reductions in fibrin forming capacity, and defibrination itself has no effect on metastasis. These findings suggest the possibility that the effect of this factor complex on metastasis may be mediated via mechanisms other than the formation of a fibrin clot.There is extensive evidence from both clinical and experimental studies for an interaction between the coagulation system and the spread and growth of malignant disease (Wood, 1958;O'Meara, 1968;Hilgard et al., 1977;Zacharski et al., 1979; Dvorak et al., 1981). Patient studies have demonstrated the existence of marked subclinical disturbances of the coagulation system in nearly all cancer patients (Sun et al., 1979;Rickles & Edwards, 1983; Mannuci et al., 1985), whilst animal experiments have suggested that the coagulation system may play an important role in the pathogenesis of blood borne metastasis (Koike, 1964;Agostino et al., 1966;Brown, 1973;Wood, 1974;. The most striking and consistent finding in such animal experimentation has been the antimetastatic effect of the coumarin group of anticoagulant drugs in a variety of tumour/host combinations (Ryan et al., 1969;Hilgard & Maat, 1979;Williamson et al., 1980). The coumarins mediate their anticoagulant activity by antagonising the action of vitamin K, an essential cofactor in the hepatic synthesis of the coagulation factors II (prothrombin), VII, IX and X (Stenflo & Suttie, 1977). W...

Warfarin inhibition of metastasis: The role of anticoagulation

Journal of British Surgery

George

1987

Warfarin inhibits metastasis in animal models by mechanisms that remain unclear. A better understanding of this phenomenon may clarify processes underlying metastasis in human cancer. We have studied the effects of warfarin on metastasis in a rat model by intravenous injection of Mtln3 mammary carcinoma cells and subsequent counting of pulmonary seedlings. To determine whether warfarin acts principally on the tumour cells or the host, we pretreated either cells or animals with warfarin before intravenous injection of 10(4) Mtln3 cells. Pretreatment of tumour cells had no effect, whilst pretreatment of the host reduced median seedlings from 67 to 4.5 per animal (P less than 0.005). To determine whether warfarin was acting via its anticoagulant action, we reversed warfarin anticoagulation by intravenous injection of coagulation factors II, VII, IX and X. Restoration of coagulation for 12 h immediately after injection of cells completely reversed the warfarin effect (P less than 0.001), but if the injection of factors was delayed for 12 h it had no effect (P = 0.1753). We conclude that warfarin acts principally on the host, not the tumour cell, and that it acts via its effect on coagulation. The restriction of the effect to the first 12 h after tumour cell injection suggests a mechanism involving intravascular processes such as tumour cell survival or endothelial adhesion.