Original ArticlesHemoglobin binds melanoma cell tissue factor and enhances its procoagulant activitySiddiqui, F. A.; Francis, J. L.Author Information The authors are with the Center for Hemostasis and Thrombosis, Clinical and Research Laboratories, Florida Hospital Cancer Institute, Orlando, Florida, USA. (Received 2 May 2001; revised 27 August 2001; accepted 30 August 2001) Sponsorship: This work was supported by the Florida Hospital Gala Endowed grant No. 071155580G for Oncologic Research. Address correspondence to Farooq A. Siddiqui, Ph.D., Hemostasis and Thrombosis Center, Florida Hospital Cancer Institute, 2501 North Orange Avenue, Suite 786, Orlando, FL 32804, USA. Tel: +1 407 303 3665; fax: +1 407 303 2441; e-mail: farooq.siddiqui@.flhosp.org Blood Coagulation & Fibrinolysis: April 2002 - Volume 13 - Issue 3 - p 173-180 Buy Abstract Tissue factor (TF), the membrane-bound glycoprotein that normally initiates the coagulation pathway, is expressed on the surface of various cells including endothelial cells, fibroblasts, monocytes and tumor cells. We recently reported that hemoglobin (Hb) enhances TF expression and procoagulant activity on TF-bearing human A375 malignant melanoma cells. To elucidate the mechanism of Hb-induced TF expression, we studied the interaction between purified TF from human A375 malignant melanoma cells and Hb. Selective binding of highly purified melanoma cell TF-apoprotein to Hb was demonstrated under native conditions using a dot-immunobinding assay and under denaturing conditions by Western blotting. The complex formation between purified melanoma cell TF-apoprotein and Hb was also demonstrated by the binding of fluid-phase Hb to immobilized TF-apoprotein (0–2.0 μg/ml) in an enzyme-linked immunosorbent assay. The binding was specific, concentration-dependent, saturable and inhibited significantly (60%) by Concanavalin-A. Hb enhanced the factor X-activating procoagulant activity of melanoma cell TF in a concentration-dependent manner, but had no effect on recombinant human TF. Concanavalin-A and wheat germ agglutinin significantly (60%) inhibited the Hb-induced procoagulant activity of malignant cell TF. We conclude that TF-apoprotein selectively binds Hb, most probably via the carbohydrate moieties (α-d-glucosyl; α-d-mannosyl and N-acetyl-β-d-glucosaminyl residues) of TF, and enhances its procoagulant activity. The physiological significance of this interaction remains to be established. © 2002 Lippincott Williams & Wilkins, Inc.