Thromboplastic and fibrinolytic activities of V2 and V7 carcinomas of rabbit, with special reference to fibrin deposition and thrombus formation in the tumors

Thromboplastic and fibrinolytic activities of V2 and V7 carcinomas, the two transplantable rabbit tumors of the same viral origin, were studied in relation to fibrin deposition and thrombus formation in the tumors. Thromboplastic activity of V7 carcinoma was comparatively high, while that of V2 carcinoma was as low as that of muscle tissue. More fibrin deposits in the stroma and more thrombi in the small vessels were found at the advancing border of V7 carcinoma than that of V2 carcinoma. These differences might be associated with higher thromboplastic activity of V7 carcinoma than that of V2 carcinoma. Fibrinolytic activity of both tumors was high and it was confirmed to be localized in the tumor cells by Todd's method. Fibrin deposits in the stroma were found more abundantly somewhat apart from the advancing border of the tumor nests of both tumors. It was suggested that plasmin activated by plasminogen activator released locally from the tumor cells might digest fibrin deposited in the stroma just close to the tumor nests.