Factor X-activating procoagulant in normal and malignant breast tissue.

Factor X-activating activity (FXAA) was determined by a chromogenic assay in normal and malignant breast tissue. FXAA was found in all tissue (n = 38) irrespective of pathology, and the activity of normal tissue was similar to that of tumours. FXAA correlated with tissue hemoglobin in normal breast (p less than 0.02) but not in tumours. FXAA was markedly reduced by aluminium hydroxide, barium citrate, anti-human factor VII, DFP, PMSF and phospholipase C, but was unaffected by iodoacetamide and mercuric chloride. It is concluded that FXAA is a serine protease with the properties of a tissue factor-factor VII complex. FXAA occurs in normal and malignant breast tissue, although the 'normal' activity may be an artefact of the homogenization process.