Factor X-activating activity in normal and malignant colorectal tissue.

The factor X-activating activity (FXAA) of homogenates from human colorectal tumours and corresponding normal colonic mucosa from the same patients was assessed with a specific chromogenic substrate technique. FXAA was detected in all normal and tumour tissue tested, but was significantly higher in tumour tissue. The procoagulant activity was inhibited by DFP, but was unaffected by iodoacetamide and mercuric chloride. FXAA was largely abolished by prior incubation of both normal and tumour tissue homogenates with a rabbit anti-human factor VII serum, but was greatly enhanced by the addition of purified factor VII. FXAA was partially adsorbed on to aluminium hydroxide and almost completely abolished by treatment with barium citrate. It is concluded that the FXAA of both normal and malignant colorectal tissue is the result of tissue factor-factor VII interaction.