Stuart G. Gordon

Analysis of serum cancer procoagulant activity and its possible use as a tumor marker

The two objectives of the study were to determine whether a procedure could be developed for measuring cancer procoagulant (CP) activity in human serum and if this procedure provided a method for distinguishing people with cancer from those without cancer. A procedure was developed for processing human serum such that the activity of other coagulation enzymes would be minimized and the activity of cancer procoagulant could be measured. In a blinded study, we collected serum from 61 individuals in serum separator tubes, removed the clot by centrifugation, extracted the serum with a simple, single step procedure and analyzed the extract for CP activity. The results indicate that this test could correctly identify about 92% of the cancer patient serum samples and about 75% of the non-cancer patients serum samples, for an overall accuracy of about 85%.

Comparison of properties of cancer procoagulant and human amnion-chorion procoagulant

Cysteine proteinases that initiate coagulation in the absence of factor VII have been isolated from rabbit V2 carcinoma and from human amnion-chorion. Many of their biochemical properties, including a molecular weight of 68 000 and inhibition by iodoacetamide and mercury, are the same. In the paper we compare the isoelectric point, the amino acid composition and the carbohydrate content of human amnion-chorion procoagulant and cancer procoagulant. With the exception of minor differences in the amino acid composition, attributable in part to differences in species, the two proteins are closely homologous.

Non-tissue factor procoagulants in cancer cells

The relationship between thromboembolic disorders and cancer would only stir an occasional glance from physicians who treat cancer patients. This lack of interest probably stems from the relatively low incidence of the clinical manifestation of thromboembolic problems associated with cancer. A heightened awareness however, is obvious when discussing the effects of chemotherapeutic treatment and the occurrences of thromboembolic complications. It is estimated that more than 90% of cancer patients exhibit abnormal levels of proteins involved in blood coagulation [1] suggesting ongoing disseminated intravascular coagulation (DIC). A more accurate measure of the problem may therefore be obtained from laboratory measurements of clotting proteins. In particular, fibrinopeptide A is a good indicator since its half life is only 4 min [2] and elevated levels of this peptide would be a strong indication of ongoing DIC. In general, cancer patients exhibit prolonged prothrombin times, elevated levels of fibrinogen-fibrin degradation products, hyperfibrinogemia, thrombocytosis and elevated levels of several coagulation factors [3--6]. These contradictory findings may be due to measurements of blood samples obtained at differing stages of the disease in different patients. Symptomatically then, patients are seen to present with laboratory evidence of prolonged clotting times, bleeding tendencies and DIC. In severe cases, these symptoms may be clinically manifested in the form of deep venous thrombosis (DVT) or severe bleeding episodes frequently caused by depletion of clotting factors [7, 8]. Chemotherapy has been used with good degree of success in the treatment of cancer patients as well as for immunosuppression in allograft recipients [7, 9-17]. In a number of patients though, the chemotherapeutic regimens have led to development of severe thromboembolic disorders. An exacerbation of thromboembolic phenomena is also seen in cancer patients following chemotherapeutic regimens. Tamoxifen is one compound known to be relatively successful in treatment of certain cancers. However, in one study [7], about 30% of the treated patients suffered severe DVT resulting in treatment termination. Collectively taken, a strong link is evident between coagulation disorders and cancer. Tumor cells may therefore be implicated as a causative agent for these problems. The advantage this property confers on tumor cells is unclear. Indirect evidence suggest that coagulation factors aid tumor cell metastasis and that fibrin and/platelets may have a hand in successful tumor cell dissemination and growth. This article will focus on procoagulant elements which may precipitate thromboembolic problems in cancer patients.

Inhibition of cancer procoagulant by peptidyl diazomethyl ketones and peptidyl sulfonium salts

Cancer procoagulant (CP) is a cysteine proteinase from cancer cells that initiates blood coagulation. Members of two classes of unique and highly specific cysteine proteinase inhibitors, peptidyl diazomethyl ketones (PDK) and peptidyl sulfonium salts (PSS), were studied to determine whether or not they inhibited CP. The inhibitors did not impair the activity of the coagulation system. There was a differential inhibitory effect of the 6 PDK and 2 PSS inhibitors, influenced by the amino acid composition or sequence of the peptide moiety, that suggests differences in structural features of the active site of CP and papain. CP was inhibited by both classes of inhibitors.

Chapter 828 – Cancer Procoagulant

Cancer procoagulant is a unique cysteine proteinase. The enzyme has been purified by several procedures and many of its characteristics and enzymatic properties have been determined. Several sensitive and reproducible assays are now available. Many proteinase inhibitors have been evaluated for their effect on CP; most low molecular weight inhibitors work well in a reduced environment. In the foreseeable future, protein and gene sequence information, expression vectors, molecular probes, and highly specific antibodies and inhibitors should provide the research tools to delineate a functional understanding of CP at the molecular and cellular level.