Fibrin as a component of the tumor stroma: origins and biological significance

Growth and Dissemination of Lewis Lung Carcinoma in Plasminogen-Deficient Mice

Plasminogen activation has been proposed to play a critical role in cancer invasion and metastasis. The effects of complete ablation of plasminogen activation in cancer was studied by inoculation of a metastatic Lewis lung carcinoma expressing high levels of plasminogen activator into plasminogen-deficient (Plg−/−) mice and matched control mice. Primary tumors developed in all mice with no difference in the rate of appearance between Plg−/− and control mice. However, the primary tumors in Plg−/− mice were smaller and less hemorrhagic and displayed reduced skin ulceration. In addition, dissemination of the tumor to regional lymph nodes was delayed in Plg−/− mice. Surprisingly, no quantitative differences were observed in lung metastasis between Plg−/− and control mice. In addition, Plg deficiency was compatible with metastasis of the primary tumor to a variety of other organs. Nevertheless, Plg−/− mice displayed a moderately increased survival after primary tumor resection. These findings suggest that plasmin-mediated proteolysis contributes to the morbidity and mortality of Lewis lung carcinoma in mice, but sufficient proteolytic activity is generated in Plg−/− mice for efficient tumor development and metastasis.

Vascular permeability factor/vascular endothelial growth factor: a multifunctional angiogenic cytokine

VPF/VEGF is a multifunctional cytokine that contributes to angiogenesis by both direct and indirect mechanisms. On the one hand, VPF/VEGF stimulates the endothelial cells lining nearby microvessels to proliferate, to migrate and to alter their pattern of gene expression. On the other hand, VPF/VEGF renders these same microvascular endothelial cells hyperpermeable so that they spill plasma proteins into the extravascular space, leading to profound alterations in the extracellular matrix that favor angiogenesis. These same principles apply in tumors, in several examples of non-neoplastic pathology, and in physiological processes that involve angiogenesis and new stroma generation. In all of these examples, microvascular hyperpermeability and the introduction of a provisional, plasma-derived matrix precede and accompany the onset of endothelial cell division and new blood vessel formation. It would seem, therefore, that tumors have made use of fundamental pathways that developed in multicellular organisms for purposes of tissue defense, renewal and repair. VPF/VEGF, therefore, has taught us something new about angiogenesis; namely, that vascular hyperpermeability and consequent plasma protein extravasation are important--perhaps essential--elements in its generation. However, this finding raises a paradox. While VPF/VEGF induces vascular hyperpermeability, other potent angiogenic factors apparently do not, at least in sub-toxic concentrations that are more than sufficient to induce angiogenesis (Connolly et al., 1989a). Nonetheless, wherever angiogenesis has been studied, the newly generated vessels have been found to be hyperpermeable. How, therefore, do angiogenic factors other than VPF/VEGF lead to the formation of new and leaky blood vessels? We do not as yet have a complete answer to this question. One possibility is that at least some angiogenic factors mediate their effect by inducing or stimulating VPF/VEGF expression. In fact, there are already clear example of this. A number of putative angiogenic factors including small molecules (e.g. prostaglandins, adenosine) as well as many cytokines (e.g. TGF-alpha, bFGF, TGF-beta, TNF-alpha, KGF, PDGF) have all been shown to upregulate VPF/VEGF expression. Further studies that elucidate the crosstalk among various angiogenic factors are likely to contribute significantly to a better understanding of the mechanisms by which new blood vessels are formed in health and in disease.

Determination of tumor cell procoagulant activity by Sonoclot analysis in whole blood

Coagulation activation in cancer may be due to expression of procoagulant activity (PCA) by tumor cells. Some PCA activate coagulation, while others influence platelet aggregation. Thus, clotting time assessments of PCA may not reflect the potential for hypercoagulability. We therefore studied the effect of various malignant and non-malignant cells on whole blood coagulation using the Sonoclot Analyzer. Five human (HT29 colon, J82 bladder, MCF-7 breast, BT-474 breast and A375 malignant melanoma) and three rodent (MC28, WEHI-164 and Neuro2a) cell lines were used. Rat thymocytes and peritoneal macrophages and human endotoxin-stimulated mononuclear cells and umbilical vein endothelial cells (HUVEC) were used as non-malignant controls. All tumor cells markedly shortened the recalcification time of citrated blood and the most potent (HT29 and J82) also increased clot rate (P < 0.01). The breast cancer cells MCF-7 and BT-474 expressed only weak PCA and did not affect clotting rate. None of the non-malignant cells significantly affected clotting time or rate in whole blood. J82 and HT29 cells grown in serum-rich media shortened the recalcification time of both normal and FVII-deficient plasmas. However, cells grown in serum-free conditions had significantly less PCA in FVII-deficient plasma. We conclude that the Sonoclot Analyzer is useful for determining cellular PCA; significant PCA is a feature of malignant cells and cells grown in medium containing serum supplements cannot be reliably evaluated for PCA.

The fibrinoids of the human placenta: origin, composition and functional relevance

Placental fibrinoids are extracellularly deposited materials which are histologically glossy and acid staining, and can be found in every normal and pathological placenta at all stages of pregnancy. The amount of fibrinoid is, in general, independent of pregnancy outcome and fetal wellbeing. According to new findings, the classical histological term "fibrinoid" covers two distinctive extracellular matrices which differ as regards structure, composition and function. Fibrin-type fibrinoid is mostly composed of fibrin together with other molecules derived from blood clotting or degenerative processes. It is mainly a maternal blood-clot product which is used (a) to adapt the intervillous space to optimized flow conditions and (b) to control growth of the villous trees by encasing new villous branches which caused intervillous stasis or turbulence of maternal blood. Moreover, fibrin-type fibrinoid replaces degenerative syncytiotrophoblast at the maternofetal exchange surfaces, thus acting as a kind of substitute barrier. Matrix-type fibrinoid is a secretory product of invasive extravillous trophoblast cells. It shares some similarities with basement membranes, however, it is secreted in an apolar fashion, embedding the secreting cells. Like basement membranes, it contains laminins, collagen IV, and heparan sulfate. In addition, oncofetal fibronectins, vitronectin, and i-glycosylated molecules but no collagens I, III, and VII can be found. Matrix-type fibrinoid is thought to regulate trophoblast invasion by specific interactions with cell surface integrins. As a kind of "glue", it anchors the placenta to the uterine wall and seems to play an important role in materno-fetal immune interactions at this particular site. Both types of fibrinoid are usually co-localized, thus indicating close morphogenetic and functional interrelations.

Regulation of VEGF/VPF expression in tumor cells: consequences for tumor growth and metastasis

Vascular endothelial growth factor (VEGF), also known as vascular permeability factor (VPF) is a multifunctional cytokine which potently stimulates angiogenesis in vivo. VEGF/VPF expression is elevated in pathological conditions including cancer, proliferative retinopathy, psoriasis and rheumatoid arthritis. The angiogenesis associated with human tumors is likely a central component in promoting tumor growth and metastatic potential. The regulation of VEGF/VPF expression during tumor progression may involve diverse mechanisms including activated oncogenes, mutant or deleted tumor suppressor genes, cytokine activation, hormonal modulators, and a particularly effective activator, hypoxia. Understanding the diverse mechanisms by which tumor cells overexpress VEGF/VPF, and which mechanisms are operating in specific tumor types is important for the design of effective anti-cancer therapies.

Elevated levels of plasminogen activator inhibitor-1 may account for the altered fibrinolysis by keloid fibroblasts

Using a 3-dimensional fibrin gel model system simulating fibroplasia of wound repair, we investigated the interaction between keloid fibroblasts and fibrin matrix and compared it with that of normal fibroblasts. Normal skin fibroblasts caused fibrin gel degradation under serum-free conditions, whereas keloid fibroblasts did not cause microscopically detectable gel degradation. Fibrin gel degradation occurred through plasmin-mediated fibrinolysis, which was initiated by fibroblasts exhibited high uPA but low plasminogen activator inhibitor-1 (PAI-1) activities, and transforming growth factor-beta 1 prevented fibrinolysis of normal fibroblasts by upregulating PAI-1 while downregulating uPA activities. In contrast, keloid fibroblasts exhibited an intrinsically high level of PAI-1 and a low level of uPA. This change in the ratio of activator and inhibitor activities was attributed to altered fibrin degradation by keloid fibroblasts. The PAI-1 increase was also demonstrated at the RNA level by Northern analysis. In terms of the pivotal role of the plasmin/plasminogen activator system in matrix remodeling, the elevated PAI-1 level exhibited by keloid fibroblasts may have significant consequences not only in altered fibrin degradation, but also in subsequent repair steps that lead to keloids and fibrosis.

Determination of plasma soluble fibrin using a new ELISA method in patients with disseminated intravascular coagulation

We measured plasma levels of soluble fibrin (SF) in 98 patients suspected of having disseminated intravascular coagulation (DIC) using a newly developed enzyme-linked immunosorbent assay (ELISA) and investigated the correlations between SF determinations and measurements of other hemostatic molecular markers to determine the diagnostic usefulness of determinations of SF. Patients were classified into four groups according to their clinical and laboratory findings: overt DIC (n =33), subclinical DIC (n =23) hypercoagulability (n =22), and non-DIC (n =20). SF levels were significantly higher in patients with overt DIC compared with the other three groups and were significantly higher in the subclinical DIC and hypercoagulability groups compared with the non-DIC patients. SF levels increased significantly with each increase in the clinical stage. Although levels of thrombin-antithrombin III complex (TAT), prothrombin fragment 1 + 2 (PF 1+2), cross-linked fibrin degradation products (XDP), and plasmin-antiplasmin complex (PAP) were significantly increased in patients with overt DIC compared with non-DIC patients, the values of these hemostatic molecular markers did not consistently show an increase in association with advances in the disease stage. Plasma levels of SF in patients with overt DIC showed a positive correlation with levels of TAT, XDP,and FDP(E), but not with PF1+2 and PAP. Analysis of receiver-operating characteristic curves showed that the sensitivity and specificity of SF were similar to those of XDP for diagnosis of DIC. The sensitivity and specificity of SF for diagnosis of overt DIC were both above 90% when the cut-off value was set at 65 mu g/ml.plasma levels of SF were also increased in patients with extravascular fibrin formation without DIC. Our findings suggest that measurement of plasma levels of SF by this ELISA method is useful for the diagnosis of DIC and the evaluation of the patient's clinical status.

Novel aspects of blood coagulation factor XIII. I. Structure, distribution, activation, and function

Blood coagulation factor XIII (FXIII) is a protransglutaminase that becomes activated by the concerted action of thrombin and Ca2+ in the final stage of the clotting cascade. In addition to plasma, FXIII also occurs in platelets, monocytes, and monocyte-derived macrophages. While the plasma factor is a heterotetramer consisting of paired A and B subunits (A2B2), its cellular counterpart lacks the B subunits and is a homodimer of potentially active A subunits (A2). The gene coding for the A and B subunits has been localized to chromosomes 6p24-25 and 1q31-32.1, respectively. The genomic as well as the primary protein structure of both subunits has been established, and most recently the three-dimensional structure of recombinant cellular FXIII has also been revealed. Monocytes/macrophages synthesize their own FXIII, and very likely FXIII in platelets is synthesized by the megakaryocytes. Cells of bone marrow origin seem to be the primary site for the synthesis of subunit A in plasma FXIII, but hepatocytes might also contribute. The B subunit of plasma FXIII is synthesized in the liver. Plasma FXIII circulates in association with its substrate precursor, fibrinogen. Fibrin(ogen) has an important regulatory role in the activation of plasma FXIII. The most important steps of the activation of plasma FXIII are the proteolytic removal of activation peptide by thrombin, the dissociation of subunits A and B, and the exposure of the originally buried active site on the free A subunits. The end result of this process is the formation of an active transglutaminase, which cross-links peptide chains through epsilon(gamma-glutamyl)lysyl isopeptide bonds. Cellular FXIII in platelets becomes activated through a nonproteolytic process. When intracytoplasmic Ca2+ is raised during platelet activation, the zymogen--in the absence of subunit B--assumes an active configuration. The protein substrates of activated FXIII include components of the clotting-fibrinolytic system, adhesive and contractile proteins. The main physiological function of plasma FXIII is to cross-link fibrin and protect it from the fibrinolytic plasmin. The latter effect is achieved mainly by covalently linking alpha 2 antiplasmin, the most potent physiological inhibitor of plasmin, to fibrin. Plasma FXIII seems to be involved in wound healing and tissue repair, and it is essential to maintaining pregnancy. Cellular FXIII, if exposed to the surface of the cells, might support or perhaps take over the hemostatic functions of plasma FXIII; however, its intracellular role has remained mostly unexplored.

The fibrinolytic system in human ascites

BACKGROUND

We recently reported that the contact and kallikrein-kinin systems are activated in malignancy-related ascites. We have now studied the fibrinolytic system in ascites and plasma from patients with gastrointestinal cancer(n = 14) and non-malignant liver disease (n = 18).

METHODS AND RESULTS

Enzyme immunoassays (EIAs) showed that urokinase and tissue plasminogen activators (uPA, tPA) and PA inhibitors (PAI-1, PAI-2) were present in ascites from both patient groups and that tPA was the predominant PA. uPA, tPA, and PAI-1, were detected in plasma from patients and controls. These EIA findings were supported by zymography studies. Functional assays showed considerable generation of plasmin-like activity and low plasminogen and antiplasmin values in malignancy-related ascites. The plasmin/antiplasmin and tPA/PAI-1 ratios were particularly high in malignancy-related ascites as compared with non-malignant ascites. Plasma from the liver disease patients showed a higher tPA/PAI-1 ratio and, thus a higher potential for plasminogen activation than plasma from cancer patients and controls. Patient plasma showed low values of plasmin-like activity, antiplasmin, and plasminogen.

CONCLUSION

Our findings show that the fibrinolytic system is activated in malignancy-related ascites.

Identification of a thrombin receptor with factor Xa receptor and tissue factor in human pancreatic carcinoma cells

Venous thromboembolism is a common feature of pancreatic cancer. The underlying mechanism is unclear, but is likely to involve thrombin generation on the cell surface. Human pancreatic carcinoma cell lines (n=8) have been studied immmunohistochemically for the expression of tissue factor, factor Xa receptor, and thrombin receptor. Each antigen had a distinct pattern of immunoreactivity in cell membrane and cytoplasm. Tissue factor was predominantly localised to the membrane, whereas thrombin and factor Xa receptor were largely cytoplasmic in distribution. The results support the hypothesis of a coagulation cascade that starts with tissue factor, leads to thrombin generation, and might confer a biological advantage on tumour cells.

Cytokine-stimulated chemotaxis of human neutrophils in a 3-D conjoined fibrin gel assay

The ability of neutrophils to migrate through three-dimensional (3-D) tissues in response to chemical stimuli is critical to their host defense function. However, studies characterizing stimulated migration in vitro have been largely limited to two-dimensional (2-D) surfaces. In this study, we have employed direct observation methods to quantify human neutrophil migration in 3-D fibrin gel using time-lapse video microscopy and automated cell tracking methods. A novel 3-D conjoined gel assay was developed to establish experimentally quantifiable and theoretically predictable diffusion gradients of chemotactic factors. This assay was used to measure objective migration parameters, namely the random motility and chemotaxis coefficients, in response to the cytokine, interleukin-8 (IL-8). The random motility coefficient, mu, showed a biphasic dependence on IL-8 concentration with a maximum of 1.1 x 10(-8) cm2/s at 5 x 10(-8) M IL-8; no significant motility was observed in the absence of IL-8. We further established the dependence of cell orientation bias, phi, on the concentration and gradient steepness (i.e., specific gradient, SG) of IL-8. Results indicate that phi increases with increasing SG, provided the concentration is maintained sufficiently low, which we conjecture to result from minimizing IL-8 receptor down-regulation. The chemotaxis coefficient, chi, was maximum at an intermediate SG for both IL-8 concentrations studied. We also examined the applicability of this assay to estimate mu and chi from indirect measurements of chemotaxis, namely the simpler measurement of cell redistribution after a prescribed incubation time, as opposed to direct cell tracking measurements. By virtue of measuring chi, this is the first quantitatively objective study of mammalian cell chemotaxis in a physiologically relevant 3-D gel and, in particular, of neutrophil chemotaxis on any substratum in response to the physiologically relevant chemotactic factor, IL-8.

Biology of human colon cancer metastasis

The process of metastasis is highly selective and favors the survival and growth of a few subpopulations of cells that preexist within a heterogeneous primary neoplasm. To produce metastases, tumor cells must succeed in invasion, embolization, survival in the circulation, arrest in a distant capillary bed, and extravasation into and multiplication in organ parenchyma. The outcome of this process depends on the interaction of metastatic cells with multiple host factors. To assess metastatic potential accurately, it is necessary to orthotopically implant human tumor cells recovered from surgical specimens into nude mice. This orthotopic implantation of tumor cells is invariably associated with trauma to the specific organ of implantation, which is followed by the processes of inflammation and repair. Tissue-specific growth factors may be responsible for stimulation of tumor cells that possess specific surface receptors. Understanding the factors that regulate cancer metastasis should allow for the design of rational therapy.

Angiogenin promotes invasiveness of cultured endothelial cells by stimulation of cell-associated proteolytic activities

Angiogenin, a potent inducer of neovascularization in the chicken chorioallantoic membrane and rabbit cornea, promotes endothelial cell invasion of Matrigel basement membrane. A transformed bovine aortic endothelial cell line, GM 7373, is 5 times more invasive when cultured in the presence of 1 microgram of bovine angiogenin per ml than in its absence. A polyclonal anti-angiogenin antibody and alpha 2-antiplasmin neutralize the effect of angiogenin, but an angiogenin-binding protein (actin) does not. Further, this concentration of angiogenin induces a 14-fold increase in the cell-associated proteolytic activity of cultured endothelial cells, determined with a tissue-type plasminogen activator-specific peptide as the substrate. In addition, cells cultured on a three-dimensional fibrin gel in the presence of angiogenin are 3 times more capable of dissolving the gel and forming focal defects in the underlying matrix. The results indicate that angiogenin can enhance the ability of endothelial cells to digest extracellular matrix components and degrade basement membrane, thereby facilitating cell invasion and migration. Binding of angiogenin to its cell-surface binding protein (actin) followed by dissociation of the angiogenin-actin complex from the cell surface and subsequent activation of tissue-type plasminogen activator/plasmin are likely steps involved in the processes of endothelial cell invasion and angiogenesis.

Immunohistochemical localization of serine-protease inhibitors in the human placenta

Proteases and their inhibitors play a pivotal role in developmental and differentiative processes. In the present report we investigated the immunohistochemical localization of alpha 1-antitrypsin, alpha 1-antichymotrypsin and inter-alpha-trypsin inhibitor in first trimester as well as in term human placentas. For this purpose polyclonal antibodies against these serine-protease inhibitors were used. All inhibitors were expressed in the villous syncytiotrophoblast of first and last trimester placentas. Placental fibrinoid was positively stained for alpha 1-antitrypsin and inter-alpha-trypsin inhibitor throughout gestation. alpha 1-Antitrypsin and alpha 1-antichymotrypsin showed a strong immunostaining in the Hofbauer cells (first trimester and full term placentas). Extravillous cytotrophoblast was negative for the three protease inhibitors throughout gestation. The presence of the three inhibitors in the syncytiotrophoblast suggests a role in coagulative, invasive and immunomodulatory processes. Fibrinoid, staining for alpha 1-antitrypsin and inter-alpha-trypsin inhibitor, could also have an important immunoprotective function. The presence of protease inhibitors in the Hofbauer cells suggests an involvement of these cells in villous remodelling and differentiative processes.

Plasma D-dimer and peritoneal CA-125 levels as predictors of disease status in ovarian carcinoma

Although serum CA-125 has improved our ability to monitor tumor response in ovarian carcinoma, approximately 50% of patients with normalization of CA-125 have persistent disease at second look laparotomy. Peritoneal CA-125 and plasma D-Dimer levels were studied to determine if their use could increase the sensitivity for persistent ovarian carcinoma in a population of patients with normal physical examinations, radiologic studies, and serum CA-125 values. Plasma D-Dimer levels were obtained prior to second look laparotomy. The results of peritoneal CA-125 and plasma D-Dimer studies were compared to second look laparotomy results. Differences were evaluated with a one-way analysis of variance. Twenty-seven patients were studied. Peritoneal CA-125 was evaluated in 23 patients and ranged from < 6.3-223 U/ml. There was no statistical difference in peritoneal CA-125 levels between patients whose second look laparotomies were negative, or microscopically or macroscopically positive. D-Dimer was elevated in three patients, all of whom had macroscopically positive second look findings. The sensitivity for positive second look findings was only 27%. Minimally elevated plasma D-Dimer levels were specific but not sensitive for persistent disease and peritoneal CA-125 was not predictive of disease status.

Enhanced antitumor effect of Bacillus Calmette-Guérin in combination with fibrinogen on urinary bladder tumor

Although intravesical instillation of Bacillus Calmette-Guérin (BCG) is an established and effective therapy for superficial urinary bladder tumor (UBT), the current major problems are BCG-resistant UBT and recurrence after BCG therapy. The injection of BCG and fibrinogen could be expected to induce the formation of a fibrin mesh, which would trap BCG and and prolong its antitumor action. The present study has been designed to investigate whether fibrinogen has the ability to augment antitumor activity of BCG against UBT. A single injection of BCG/fibrinogen solution into the subcutaneous tissue of C3H/He mice was performed. Histopathological examination revealed prolonged accumulation of BCG and marked infiltration of inflammatory cells at the injected site, as compared with the injection of BCG or fibrinogen alone. When BCG was used in combination with gelatin sponge, prolonged BCG accumulation was also observed, but not many inflammatory cells were induced, as compared with injection of BCG/fibrinogen combination. When BCG/fibrinogen solution was injected into MBT-2 murine UBT transplanted into C3H/He mice, the formation of fibrin fibers, which trap BCG, was induced, and many inflammatory cells around the tumor were seen. A pronounced inhibitory effect on tumor growth and prolonged survival of tumor-bearing mice were achieved, as compared with the injection of BCG alone. Dead BCG/fibrinogen solution had a modest inhibitory effect on the tumor growth. This study suggests that combination treatment with BCG and exogenous fibrinogen may prolong accumulation of BCG by BCG by trapping BCG in fibrin meshwork, and may induce marked infiltration of inflammatory cells into tumor stroma, causing marked regression of the tumor. The possible clinical implications of the combined use of BCG and fibrinogen are discussed.

Abdominal wall metastases following laparoscopy

Only 18 cases of recurrence at the sites of cannula insertion after laparoscopy have been reported in the literature, ten of them in the past year. The period between laparoscopic surgery and presentation of wound metastasis varies widely, from 7 days to 10 months; the lesions are typically hard, craggy and painful. The most likely mechanism is direct implantation of viable exfoliated tumour cells but three aspects specific to laparoscopy may also be important. First, there may be increased exfoliation of tumour cells following manipulation by laparoscopic instruments of an unsuspected malignancy. Second, there may be repeated close contact between tumour-laden instruments and the port. Third, the passage of resected tissue through a small incision may coat the wound with potentially malignant cells.

Procoagulant activity of the MC28 fibrosarcoma cell line in vitro and in vivo

Experimental evidence suggests that many tumours can activate blood coagulation and that such interaction is part of the pathology of metastatic tumour growth. This study aimed to study the procoagulant activity of the methylcholanthrene-induced (MC28) fibrosarcoma to determine whether coagulation activation by these cells could explain the previously reported effects of oral anticoagulants on lung seeding in this model. MC28 cells shortened the recalcification times of normal and factor VII-deficient plasma and directly activated factor X in a chromogenic assay, but did not aggregate platelets in vitro in either whole blood or platelet-rich plasma. Cellular coagulant activity was calcium-dependent, blocked by DFP and concanavalin A but not inhibited by iodoacetamide, E-64 or antibodies to human tissue factor or factor VII. Injection of viable MC28 cells into hooded Lister rats induced a decrease in platelet count (P < 0.001), plasma factor X (P < 0.001) and fibrinogen (P < 0.05) and a marked increase in plasma haemoglobin (P < 0.001). These effects were either not observed or were considerably less marked in heparinized or warfarinized animals. Injection of MC28 cells treated with concanavalin A in vitro completely abolished the clotting changes observed with untreated cells. In conclusion, MC28 cells possessed a potent factor X-activating serine proteinase procoagulant in vitro, which had some of the characteristics of a tissue factor/factor VIIa complex. In vivo, MC28 cells caused clotting activation and intravascular fibrin generation. Since thrombocytopenia was abolished by heparin and the cells lacked platelet aggregating activity in vitro, thrombocytopenia was probably secondary to intravascular coagulation and thrombin generation. The trigger for intravascular clotting activation appeared to be the cellular procoagulant activity since it was abolished by prior in vitro blockade of the latter with concanavalin A.

Vascular permeability factor (VPF, VEGF) in tumor biology

Vascular permeability factor (VPF), also known as vascular endothelial growth factor (VEGF), is a multifunctional cytokine expressed and secreted at high levels by many tumor cells of animal and human origin. As secreted by tumor cells, VPF/VEGF is a 34-42 kDa heparin-binding, dimeric, disulfide-bonded glycoprotein that acts directly on endothelial cells (EC) by way of specific receptors to activate phospholipase C and induce [Ca2+]i transients. Two high affinity VPF/VEGF receptors, both tyrosine kinases, have thus far been described. VPF/VEGF is likely to have a number of important roles in tumor biology related, but not limited to, the process of tumor angiogenesis. As a potent permeability factor, VPF/VEGF promotes extravasation of plasma fibrinogen, leading to fibrin deposition which alters the tumor extracellular matrix. This matrix promotes the ingrowth of macrophages, fibroblasts, and endothelial cells. Moreover, VPF/VEGF is a selective endothelial cell (EC) growth factor in vitro, and it presumably stimulates EC proliferation in vivo. Furthermore, VPF/VEGF has been found in animal and human tumor effusions by immunoassay and by functional assays and very likely accounts for the induction of malignant ascites. In addition to its role in tumors, VPF/VEGF has recently been found to have a role in wound healing and its expression by activated macrophages suggests that it probably also participates in certain types of chronic inflammation. VPF/VEGF is expressed in normal development and in certain normal adult organs, notably kidney, heart, adrenal gland and lung. Its functions in normal adult tissues are under investigation.

Myocardial fibrin deposition in experimental viral myocarditis that progresses to dilated cardiomyopathy

Myocardial fibrosis is a characteristic late feature in cases of viral myocarditis that progress to dilated cardiomyopathy. However, the pathogenesis of the myocardial fibrosis in such cases is unknown. Prior studies have shown that in healing wounds and tumor stroma generation, interstitial fibrin deposition precedes the development of fibrosis. Therefore, interstitial fibrin deposition in the myocardium was investigated in a murine model of myocarditis in which dilated cardiomyopathy develops. Inbred male C3H/He mice inoculated with coxsackievirus B3 were killed 0, 3, 7, 14, 21, 30, and 60 days after infection. Paraffin sections of hearts were stained with hematoxylin-eosin, Masson's trichrome stain, and antibodies to fibrinogen/fibrin by use of an immunoperoxidase technique. Pretreatment of all mice with anticoagulants and antifibrinolytics 5 minutes before death was used to prevent artifactual fibrin deposition and fibrinolysis during tissue manipulation. Tissue fixation in formalin supplemented with acetic acid served to extract non-cross-linked fibrin, fibrinogen, and fibrinogen and fibrin degradation products, thus ensuring that clotted and cross-linked fibrin was the major immunoreactant. Myocardial fibrin deposition and fibrosis were each quantitated by computer-assisted image analysis. Myocardial fibrin deposition first appeared on day 3, was maximal on day 14, and disappeared by day 30. Conversely, myocardial fibrosis was not detectable until day 14 and was maximal at day 60. Thus, as in healing wounds and developing tumor stroma, fibrin deposition preceded fibrosis in this murine model of myocarditis that progresses to dilated cardiomyopathy.

Location of plasminogen activator (PA) and PA inhibitor in human colorectal adenocarcinomas

Both the coagulation and fibrinolytic cascades generate proteolytic enzymes which appear to be essential for tumor invasion. In the present investigation adenocarcinomas and normal colon from 14 patients with colorectal cancer were studied by immunohistochemistry. The most striking observation was an enrichment of plasminogen activator inhibitor in the tumor tissue, whereas no such immunoreactivity was detected in the biopsies of normal colon. The tumor-host interface was characterized by a massive accumulation of inflammatory cells, macrophages and T lymphocytes. In this area fibrin(ogen) immunoreactivity as a sign of local activation of the coagulation cascade was also seen. The transition zone between the tumor and normal tissue was furthermore characterized by a marked enrichment of urokinase plasminogen activator immunoreactivity. The study strongly indicates that proteases and inhibitors of the fibrinolytic system may be of great importance in tumor invasion.

The role of fibrin in tumor metastasis

A volume of data that has accumulated for over a century has suggested that fibrin may facilitate the persistence and progression of malignancy. Techniques that have been developed recently have shown that fibrin is indeed a component of the connective tissue stroma in human malignancy but in only a few tumor types. However, therapeutic intervention studies with drugs that limit thrombin activity or enhance fibrinolysis have shown favorable clinical effects in at least one such tumor type. These favorable findings affirm the concept that cause-and-effect relationships do, in fact, exist between thrombin generation with fibrin formation and tumor progression, and suggest that a rational basis exists for the design of future drug intervention trials that target reactions relevant to specific tumor types. These findings also provide a basis for the design of experiments capable of defining further the role of fibrin in the integrity of these tumor types. Because fibrinogen is found much more commonly than fibrin in the connective tissue of a variety of human malignancies, attention might reassumably be directed to determining the possible contribution of this molecule as well as of fibrin to tumor progression.

Tissue factor as a tumor procoagulant

Tissue factor is a cell surface glycoprotein responsible for initiating the extrinsic pathway of coagulation. Many tumor cell homogenates and intact tumor cells have been shown to contain tissue factor activity. Immunohistochemical studies show that many tumors associated with Trousseau's syndrome express tissue factor on their cell surfaces. Tumor cells shed membrane fragments which carry tissue factor that can account for the activation of the clotting system. Tumor cells also produce soluble substances that can induce tissue factor expression on host cells, such as endothelium and monocytes, at sites distant from the tumor. Although, all the functional TF molecules are localized on the outer cell membrane in many tumor cells, the procoagulant activity on the intact cell surface is largely dormant and can be greatly enhanced upon cell injury or damage. Tissue factor procoagulant activity on the cell surface can be modulated by alterations in the plasma membrane without loss of cell viability. Tissue factor activity on cell surfaces is largely regulated by a plasma inhibitor, tissue factor pathway inhibitor. This inhibitor binds to both functional and non-functional tissue factor/VIIa complexes on the cell surface and prevents non-functional tissue factor/VIIa complexes from becoming functional after cell injury or lysis. Heparin, but not warfarin, therapy is effective in preventing the occurrence of devastating thrombotic events in patients with Trousseau's syndrome and the reason(s) for this are still unknown.

Mechanisms of metastasis

The role of dermatologists in the diagnosis and treatment of skin cancer continues to increase. Consequently, they will more frequently be involved in the diagnosis, treatment, and management of patients with metastatic or potentially metastatic tumors. Squamous cell carcinomas and malignant melanomas are frequently seen in dermatologic practices and have the capability to metastasize. Metastases are the result of a complex process that is characterized by a sequence of steps, each of which requires acquisition by the malignant cell of key biologic properties. The metastatic sequence can be conceptualized as detachment from the primary tumor followed by invasion, intravasation into a vessel, circulation, stasis within a vessel, extravasation, invasion of the recipient tissue bed, and ultimately proliferation. The basic steps of the metastatic sequence are described as well as how these steps and other tumor cell adaptations can affect the clinical patterns of metastasis. Finally, practical applications of the understanding of these principles of metastasis are discussed.

D-dimer and CA 125 levels in patients with ovarian cancer during antineoplastic therapy. Prognostic significance for the success of anti-cancer treatment

In patients with ovarian cancer before they receive chemotherapy, the level of fibrin degradation products (D-dimer), is correlated with the tumor load. In this study, the evolution of D-dimer was compared in patients receiving antineoplastic therapy with the evolution of the disease. The patients could be classified into three groups. In Group 1 (nine patients), both plasma CA 125 (a tumor-associated antigen) and D-dimer remained elevated; the prognosis was always poor. In Group 2 (eight patients), CA 125 and D-dimer decreased simultaneously, complete remission was observed in two patients, and significant residual tumor was observed in the others. In Group 3 (nine patients), despite an important decrease in CA 125, D-dimer remained elevated during therapy. In this group, complete remission was observed in six patients, and three others showed a large decrease in their tumor load. The combination of a decrease in CA 125 levels with a continuous enhanced level of D-dimer during chemotherapy identified a subgroup of patients with a favorable prognosis.

A desmoplastic granular cell tumour of the oral cavity: report of a case

A case of granular cell tumour of the buccal mucosa demonstrating marked desmoplasia is presented. The bulk of the tumour is composed of dense collagenous stroma, which surrounds isolated nests of tumour cells. Since the histomorphologic appearance of this variant is different from that usually seen in this lesion, the diagnosis is supported by immunohistochemical demonstration of S-100 and Vimentin in the tumour cells. The authors believe that this case represents the first report of a desmoplastic granular cell tumour of the oral tissues.

A fibrin matrix modulates the proliferation, hormone secretion and morphologic differentiation of cultured human placental trophoblast

Term placental trophoblast epithelialize fibrin deposits attached to villi in vitro and trophoblast cultured on a fibrin matrix form an epithelial bilayer typical of the trophoblast layer on term villi. We compared the morphology of cells grown on fibrin with cells grown on substrates of type IV collagen, laminin, type I collagen, or Matrigel. We also used autoradiography, hormone assays, electron microscopy, and immunofluorescence to determine what functional activities were influenced by trophoblast-fibrin interactions. Cultured cellular trophoblast from term placentae differentiated to form syncytial trophoblast and to secrete estrogen, progesterone, and hCG in the presence or absence of matrices. Trophoblast proliferation was lower in cells grown on matrices and was inversely related to cell height after 24 h in culture. Cells grown on fibrin remained the tallest and had the lowest labelling index. Cells grown for 72 h on fibrin had the most dilated rough endoplasmic reticulum but the lowest media hormone levels. Only cells grown on a fibrin matrix formed a basal lamina-like structure at the trophoblast-substrate interface, and only a fibrin matrix facilitated trophoblast to form an epithelial bilayer in culture. However, this histology was not accompanied by a change in the amount of syncytial trophoblast formed by the cells grown on fibrin. The results suggest that a fibrin matrix uniquely modulates the trophoblast phenotype, away from the secretion of placental specific products like hCG in favour of a repair-oriented phenotype that forms basement membrane and a trophoblast bilayer.

Use of fibrinogen to enhance the antitumor effect of OK-432. A new approach to immunotherapy for colorectal carcinoma

OK-432 (5 KE), an immunomodulatory agent prepared from an attenuated strain of Streptococcus pyogenes, was dissolved in 1 ml of aprotinin (1000 KIE) and mixed with 80 mg of fibrinogen containing Factor XIII. A single intratumoral injection of the mixture was performed preoperatively under endoscopy in 20 patients with colorectal carcinoma. Postoperative histopathologic examinations revealed the formation of fibrin fibers at the site of injection and marked infiltration of inflammatory cells into the tumor stroma on the day after injection; the formation of granulomas containing many giant cells after 4 to 7 days; and extensive regression of tumor tissue after 14 days. This study suggests that the high concentration of exogenous fibrinogen gelatinized enough to trap OK-432 in tumor stroma and that OK-432 induced granulomatous hypersensitivity to degenerate tumor stroma, thereby causing regression of the tumors.

Blood coagulation changes in nude mice bearing human colon carcinomas

We studied several blood coagulation parameters and tumor tissue procoagulant activity (PCA) in nude mice bearing human colorectal carcinomas (HCC). In a control group of 51 tumor-free nude mice, platelet number was 1.2 +/- 0.03 x 10(6)/microliters, thrombotest activity 90% +/- 2.6 and fibrinogen 172 +/- 11 mg/dl. The same parameters were studied in nude mice (n = 71) bearing 7 different HCC lines subcutaneously (s.c.). The results did not significantly differ from those in control mice but there was broad variability among groups of mice injected with different HCC lines, ranging from 0.36 to 2.55 x 10(6)/microliters for platelets, from 100 to 28% for thrombotest activity and from 42 to 460 mg/dl for fibrinogen. The results were significantly (p less than 0.05) different from those in the tumor-free group when each group of HCC-bearing animals was analyzed individually. A malignant HCC line that grew in the liver of nude mice (n = 24) significantly (p less than 0.001) reduced thrombotest activity (58% +/- 5.9). The PCA of tissue extracts from tumors grown s.c. in nude mice was assayed. All the HCC xenografts expressed PCA which differed significantly for the various tumor lines (from 25.5 +/- 1.9 to 2.8 +/- 0.6 unit/mg in tumor tissue). Cancer procoagulant (CP), a cysteine proteinase with a direct factor-X-activating effect, was present in different amounts (84.7 +/- 4.3 to 59.5 +/- 9.0%) in the tumors. Our results indicates that the nude mouse is a suitable model for evaluating the hemostatic changes induced by human tumors and may represent a tool for investigating the underlying biochemical mechanisms.

Inhibition of tumor implantation at sites of trauma by Arg-Gly-Asp containing proteins and peptides

We report on the inhibition of wound implantation by TA3Ha mammary carcinoma cells by Arg-Gly-Asp containing proteins and peptides using a hepatic wedge resection model. Intravenously injected TA3Ha cells rarely form tumor in the liver of syngeneic mice, but after hepatic wedge resection, 45% (107/240) of the mice develop tumors in the hepatic wound. Hepatic wound implantation is significantly (P = 0.01) inhibited by pretreating the cells with whole mouse plasma, but not with fibrinogen-depleted plasma or serum. Tumor inhibition is also achieved by pretreatment of cells with fibrinogen (P = 0.05-0.0004), fibronectin (P = 0.007) and laminin, but not by albumin. The active domain appears to be the RGDS sequence since the deca- and tetrapeptides containing RGDS inhibit wound implantation (P less than 0.05). However, the tetrapeptide Arg-Gly-Glu-Ser has no such activity. None of these agents affects ascites tumor formation by the intraperitoneally injected cells, suggesting that anchorage independent growth of cells is not affected. We propose that proteins and peptides containing RGD occupy the binding sites and prevent the cells from interacting with cell adhesion proteins in healing wounds. Proteins and/or peptides containing RGD may be useful for preventing local recurrence in postsurgical cancer patients.

Inhibition of tumor implantation at sites of trauma by plasminogen activators

The authors report on the influence of plasminogen activators (PA) on implantation of TA3Ha mammary tumor cells in the healing hepatic wounds of syngeneic strain A mice. Intravenously injected TA3Ha cells, although they rarely metastasize to the liver, formed tumors in the hepatic wounds of a significant percent (42%, P less than 0.0001) of mice. The frequency of tumor formation declined as the interval between surgery and tumor cell inoculation was increased. Furthermore, preexposure of cells to fibrinogen, fibronectin, laminin, or peptides containing the arginine-glycine-aspartic acid-serine residues dramatically reduced the frequency of tumor formation in the hepatic wounds. These results indicate that TA3Ha cells interact with fibrinogen-related proteins in the wound to aid their attachment and growth. Because these proteins are susceptible to digestion by plasmin, PA were used in this study to examine whether administration of these drugs to the mice would modulate tumor formation in the liver wounds. Among the PA tested, human plasmin B-chain-streptokinase complex (B-SK) and recombinant tissue plasminogen activator (t-PA) inhibited tumor implantation in a dose-related manner. Administration of 900 units (U) of B-SK or 3300 U of t-PA per mouse reduced the frequency of tumor formation from 42% to 0% (P = 0.02) and 11% (P = 0.02), respectively. The B-SK was complexed with p-nitrophenyl-p-guanidinobenzoate; it did not activate the plasminogen or inhibit tumor formation in the hepatic wounds. Although urokinase activated the plasminogen, it did not inhibit tumor implantation in the hepatic wound. Heparin, an anticoagulant that prevents conversion of fibrinogen to fibrin without being fibrinolytic, had no influence on tumor formation in the hepatic wounds. The PA can generate plasmin that digests the cell attachment proteins in wounds and consequently inhibits tumor cell attachment.

The human placenta: a model for tenascin expression

Tenascin is a large glycoprotein of the extracellular matrix. Previous reports have demonstrated that it is associated with epithelial-mesenchymal interfaces and is expressed during embryonic and tumour development, wound healing, cell proliferation and it may be involved in immunomodulation. The human placenta shows numerous features related to these aspects. We have investigated the presence of tenascin in the human placenta throughout pregnancy by immunohistochemistry. We used monoclonal (mAb) and polyclonal (pAb) antibodies to tenascin, a mAb to fibrin, a pAb to fibrinogen, and the mAb Ki-67 as proliferation marker. Tenascin was highly expressed in the mesenchymal villi which are considered the basis of growth and differentiation of the villous trees. Moreover, fibrinoid deposits at the surfaces of the villous trees were always separated from the fetal stroma by tenascin. The stroma of villi encased in fibrinoid was also positive for tenascin. This glycoprotein was also expressed in the villous stroma directly apposed to cell islands and cell columns. In the proximal portions of both epithelial structures, cytotrophoblast was Ki-67 positive. These data show that tenascin is expressed during the development of the placenta, particularly in the mesenchymal villi, cell islands and cell columns. These structures are considered to be the proliferating units of the villous trees. Tenascin underlying fibrinoid deposits suggests that it also participates in repair mechanisms. Thus, in the human placenta tenascin expression can be correlated with villous growth, cell proliferation, and fibrinoid deposition. Its role in immunoprotection of fetal tissues in areas where syncytiotrophoblast as barrier is missing or damaged is discussed.

The skeletal framework of human kidney and renal cell carcinoma. A scanning electron microscopic study

The three dimensional architecture of the connective tissue framework of normal human kidney and three renal cell carcinomas was studied. A sodium hydroxide maceration technique was used to remove the cellular elements thus exposing the underlying connective tissue structures. The collagen fibrillar network was visualized using the scanning electron microscope. In normal kidney the fibres were fine, and smooth, and corresponded to the shapes of the original parenchymal constituents. The fibres of the kidney tumours were coarse in nature and irregularly distributed. The technique provides a rapid method for studying connective tissue fibres in normal and diseased tissue. The three dimensional architecture thus exposed enhances our knowledge of tumour stroma.

Antimetastatic effect of defibrinogenation with batroxobin depends on the natural killer activity of host in mice

Using batroxobin, a thrombin-like enzyme found in snake venom, the effects of defibrinogenation on artificial lung metastasis in mice were studied. The role of natural killer (NK) cells in the inhibitory effects of defibrinogenation on metastasis was also investigated. Artificial lung metastasis experiments were performed by inoculating either B16-F10 cells or B16-BL/6 cells, highly metastatic strains of B16 melanoma cells, into C57BL/6 mice via the tail vein. The administration of batroxobin significantly inhibited lung metastasis, as did NK activity augmented by poly (I).poly (C) were administered, lung metastasis was more markedly inhibited. When NK activity was suppressed by administration of anti-(asialo GM1) antibody, lung metastasis was markedly increased. When batroxobin was administered with anti-(asialo GM1) antibody, no inhibitory effects on lung metastasis, such as those seen with batroxobin alone, were observed. The administration of batroxobin had no effect at all on spleen lymphocyte NK activity. These results indicated that defibrinogenation due to batroxobin inhibits lung metastasis, and these effects depend on NK activity of the host.

Measuring plasma fibrinogen to predict stroke and myocardial infarction

Epidemiological observations indicate that high plasma fibrinogen levels are strongly correlated with the frequency of two major thrombotic complications of atherosclerosis, stroke and myocardial infarction. Thrombosis is increasingly recognized as a central mechanism in stroke and myocardial infarction, and fibrinogen is involved in events thought to play a major role in thrombosis. Therefore, elucidation of the relationship between fibrinogen and thrombosis may strengthen the predictive value of this protein and suggest new treatment to prevent stroke and myocardial infarction. The current data relating fibrinogen to thrombosis are not easy to reconcile with the available epidemiological observations. In addition, advances in understanding the atherogenic potential of several risk factors for coronary heart disease have used information on the measurement of the risk factors in population-based studies. Thus, measuring plasma fibrinogen to predict stroke and myocardial infarction may be important in gaining insight into the thrombogenic potential of this protein and in inspiring new strategies against the thrombotic complications of atherosclerosis.

The influence of surgical trauma on experimental metastasis

Influence of surgical trauma on experimental metastasis in healing wounds is investigated using a transplantable murine mammary carcinoma cell line, TA3Ha. Intravenous injection of 10(5), 10(6), and 2 x 10(6) TA3Ha cells into syngeneic Strain A mice led to liver or kidney tumor development in none of the 96, ten, and ten mice tested, respectively. In contrast, injection of 10(5) cells into mice immediately after hepatic wedge resection performed using milliwatt carbon dioxide laser and electrocautery resulted in tumor formation at the site of trauma in 21/37 (57%) and 25/52 (48%) mice, (P less than 0.001) respectively. Similar results were obtained in mice subjected to partial nephrectomy using the laser (nine of 18) and electrocautery (eight of 13). These results clearly demonstrate that surgical trauma renders a nonprivileged organ susceptible to experimental metastasis formation, and that at least in this model both laser and electrocautery have similar effects. Tumor cell injection 1, 7, and 10 days posthepatic surgery resulted in 36%, 20%, and 0% tumor formation, respectively, indicating that the earlier events in wound healing support tumor implantation and/or growth better than those later on. Frequency of tumor formation at sites of trauma in the peritoneum induced by scalpel blade, laser, and electrocautery were 28%, 50% and 82%, respectively. Peritoneal tumors were seen in 33% of the nonsurgical mice. Skin incisions induced with the three above probes had little influence on experimental metastasis formation. Thus the influence of trauma on tumor formation is not uniform in every organ.

Fibronectin and fibrinolysis are not required for fibrin gel contraction by human skin fibroblasts

Human skin fibroblasts contracted fibrin gels in a time- and cell-dependent manner. Under optimal conditions, gel contraction amounted to more than 50% in 2 hr. Fibronectin did not promote contraction, and fibrinolysis was not required for contraction, although gels contracted without serum or aprotinin were lysed. Before contraction, fibrin was present in loosely packed, randomly organized fibrils. After contraction, the fibrils were more densely packed and aligned in the plane of cell spreading. Cycloheximide treatment of fibroblasts inhibited gel contraction in serum-free medium but not in serum-containing medium. Fibronectin could not substitute for serum in overcoming the cycloheximide effect. Binding sites for fibrin were distributed randomly over the cells' surfaces based on electron microscopic observations. Often small groups of fibrils were localized in indentations at the cell surface. Finally, peptides containing the arg-gly-asp-ser sequence inhibited gel contraction.

Urokinase-type plasminogen activator biosynthesis is induced by the EJ-Ha-ras oncogene in CL26 mouse colon carcinoma cells

CL26 murine colon carcinoma cells express urokinase-type plasminogen activator (u-PA) mRNA and activity after transfection with the activated c-Ha-ras-I (EJ-ras) oncogene cloned from the EJ bladder carcinoma. PA activity and mRNA in control cells transfected with the non-mutated c-Ha-ras-I (CO-ras) gene remained negative. Ras mRNA was detected in EJ-ras- and CO-ras-transfected cells, but not in untransfected or pSV2-neo-transfected cells. These results indicate that u-PA biosynthesis can be modulated by EJ-Ha-ras-dependent pathways of signal transduction.

Pathogenesis of tumor stroma generation: a critical role for leaky blood vessels and fibrin deposition

Tumor stroma formation results from the interaction of tumor cells and their products with the host and certain of its normal defense mechanisms, particularly the clotting and fibrinolytic systems. It is a process in which tumor cells render local venules and veins hyperpermeable with the result that fibrinogen and other proteins extravasate and clot, forming an extravascular crosslinked fibrin gel. Coagulation is mediated by an interaction between extravasated plasma clotting factors and tumor-associated and perhaps other tissue procoagulants. Parallel activation of the fibrinolytic system leads to substantial fibrin turnover, but fibrin nonetheless accumulates in amounts, variable from tumor to tumor, that are sufficient to provide a provisional stroma. This provisional stroma imposes on tumor cells a structure that persists even as tumor cells multiply and as the fibrin provisional stroma is replaced by mature connective tissue. The provisional fibrin stroma also serves to regulate the influx of macrophages, and perhaps other inflammatory cells, but at the same time, and in ways that are not fully understood, facilitates the inward migration of new blood vessels and fibroblasts, integral components of mature tumor stroma. Ascites tumors differ from solid tumors in that fibrin gel is not ordinarily deposited in body cavities and, as a result, there is no provisional stroma to impose an initial structure. Tumor stroma generation resembles the process of wound healing in many respects. However, it differs in the mechanism of its initiation, and in the apparent lack of a role for platelets. It also differs fundamentally in that invading tumor cells continually render new vessels hyperpermeable to plasma, thus perpetuating the cycle of extravascular fibrin deposition. In this sense, tumors behave as wounds that do not heal. Largely neglected in this review has been discussion of the numerous cytokines, mitogens, and growth factors that are widely believed to play important roles in tumor angiogenesis and wound healing; i.e., PDGF, FGF, EGF, TGF alpha, TGF beta, TNF, interferons, etc. This omission has been intentional, and for two reasons. First, these cytokines have already received considerable attention [100,123-128]. Second, it is not yet clear how closely the actions of these molecules, as described in vitro, relate to their functions in vivo. At present we are deluged with a surfeit of factors that have the capacity to induce new blood vessel formation in angiogenesis assays; these factors include not only peptides but lipids and even ions [126,129-131].(ABSTRACT TRUNCATED AT 400 WORDS)

Procoagulant activity of mouse transformed cells: different expression in freshly isolated or cultured cells

This study was originally designed to investigate whether there is any correlation between the type of procoagulant activity (PCA) and the tumorigenicity of transformed cells. The data obtained are relevant to this question and to defining the differences in the expression of cellular activities depending on the in vitro system used. PCA was measured and characterized in normal, immortalized, and tumorigenic mouse fibroblasts. In all the cell lines studied the activity was of tissue factor type, as established with functional, enzymatic, and immunochemical criteria. However, the PCA of cells freshly isolated from the tumors induced by tumorigenic cell lines was of cancer procoagulant type, i.e. a cysteine protease with direct factor X activator activity. The same cells, when cultured in vitro, expressed again PCA of tissue-factor type. These results suggest that either a tumor-host interaction is required for the expression of cancer procoagulant or the latter activity, produced by tumor cells under in vitro conditions, is destroyed or inactivated during the culture period. Our findings caution against defining the procoagulant activity of tumors based on experiments on cultured cells.

Evaluation of phenylthiourea derivatives as inhibitors of transglutaminase-catalyzed reaction in Chinese hamster ovary cells

1-(5-Aminopentyl)-3-phenylthiourea (PPTU), a recently developed inhibitor of the transglutaminase-catalyzed reaction (K.N. Lee, L. Fesus, S.T. Yancey, J.E. Girard, and S.I. Chung, (1985) J. Biol. Chem. 260, 14689-14694) was evaluated as a possible probe to examine the physiological role of transglutaminase (EC 2.3.2.13) in Chinese hamster ovary (CHO) cells. The [14C]PPTU in cell culture was readily taken up by CHO cells and was found to be covalently attached to high-molecular-weight proteins which are associated with the particulate fractions. Incubating cell homogenates, in the presence of Ca2+, incorporated the labeled PPTU exclusively into high-molecular-weight proteins that were also undergoing polymerization. PPTU at 0.1 mM, a concentration close to the Ki value reported for inhibition of tissue transglutaminase-catalyzed amine incorporation into the B chain of oxidized insulin, decreased high-molecular-weight protein polymerization, whereas PPTU at the same concentrations showed no effect on CHO cell proliferation or on in vitro calmodulin activation of cyclic nucleotide phosphodiesterase. These results suggest that transglutaminase may not be a constitutive enzyme in cell proliferation.

What's new in the ultrastructure of tumor invasion in vivo?

An important point emerging from the literature on tumor invasion in vivo is the great variability of nearly all aspects studied. It seems that there is neither one particular morphologic change which renders a cell invasive, nor one particular mechanism by which a cell crosses the boundaries of its original tissue compartment to occupy another. Nevertheless, some general trends are demonstrable. The majority of invasive tumor cells appear to be characterized by prominent surface protrusions, decreased junctional contacts and, in the case of epithelium-derived tumor cells, an incomplete basement membrane. The fact that some tumors can invade foreign tissues without loosing their basement membrane is emphasized. Invasive cells frequently form organized associations with preexistent non-neoplastic cells without damaging them. Apparently, the eventual disappearance of the preexistent cells in most invaded tissues is not necessarily due to a direct action on the part of the tumor cells. It rather seems a secondary phenomenon caused by, e.g., the insertion of invasive tumor cells between the preexistent cells and their original stroma. Very often, this seems to be due to the affinity of malignant cells for basement membranes. In addition, the adhesion of tumor cells to basement membranes frequently seems to determine their pattern of spread through a tissue. A process which may turn out to be a key factor in tumor invasion is desmoplasia, the series of host reactions which creates a new environment for the tumor cells which may favor their survival, proliferation, and locomotion. With the rapid development of new techniques, electron microscopy will probably contribute to the elucidation of the exact nature, the degree of similarity to granulation tissue, and the influence on invasion of desmoplastic tumor stroma.

Procoagulant activity of gastric, colorectal, and renal cancer is factor VII-dependent

The PA of GC, CC, and RC extracts was assayed by the recalcification of human normal or F VII-DP, and the PA of normal tissue was also determined. The PA of normal tissue was higher than that of the cancer tissues in all groups of specimens. Substitution of normal plasma by F VII-DP resulted in significant depression of the PA and the differences in the PA between the normal and cancer tissue samples disappeared. Preincubation of normal and cancer tissue extracts with the cysteine proteinase inhibitors, mercuric chloride and iodoacetamide, did not affect the PA of these extracts. We conclude that the PA of the investigated cancer extracts is factor VII-dependent and can be related to the presence of tissue factor within cancer tissue.

DMSO-induced changes in the procoagulant and fibrinolytic activity of B16 melanoma cells: influence on lung colony formation

In this study DMSO (dimethylsulphoxide) was used as a tool to test the significance of in vitro modifications of procoagulant and fibrinolytic activity of tumor cells for their in vivo metastatic ability. B16 melanoma cells were chosen as the experimental model. After four days' treatment DMSO increased both the procoagulant and fibrinolytic (plasminogen activator) activity of B16 melanoma cells in a dose-related manner. DMSO treated cells showed significantly greater lung colonizing ability than untreated cells. Our results indicate that DMSO treatment in vitro can modulate procoagulant and fibrinolytic activity and the metastatic ability of B16 melanoma cells; however a direct causal relationship between these in vitro and in vivo effects remains to be established.