A bioassay is described for the quantitation of tumor cells in blood specimens in a syngeneic mouse tumor system (Sarcoma 1 in A/J mice). The procedure involved i.m. injection of blood containing tumor cells into each thigh of normal recipient mice and, 14 days later, examination of the sites of injection for evidence of tumor growth. For each specimen, a tumor index was calculated based on the number of tumor takes and the size of the tumors. The number of tumor cells was determined by comparison with tumor indices from standard specimens with known number of tumor cells. Optimal conditions for this assay were investigated. We have used this bioassay to quantitate tumor cells in the venous blood of tumor-bearing animals under various treatments and manipulations. At the same time, the incidence of regional node metastasis was obtained by direct histological examination. Surgical removal of a well-established primary tumor enhanced the dissemination of the tumor, as evidenced by an increased incidence in regional node metastasis and an increase in the number of tumor cells reaching the venous circulation. Similar results were obtained when the tumor-bearing feet were ligated to produce ischemia of the primary tumor. Repeated physical trauma to the primary tumor resulted in increased dissemination of tumor cells into the venous circulation, but it did not increase the incidence of regional node metastasis. Immunosuppression of the tumor-bearing animals increased the dissemination of tumor cells, whereas immunostimulation decreased the dissemination.


Supported in part by National Cancer Institute Grant CA 13916-02.

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