The influence of host immunity on the arrest of circulating cancer cells, and its modification by neuraminidase

The patterns of initial tumour cell arrest of a methylcholanthrene‐induced fibrosarcoma and the Gardner lymphosarcoma were determined after injection of 125IudR‐labelled tumour cells into the systemic circulation of mice. Experiments were performed with normal mice, mice sensitized by bearing ascites or subcutaneous variants of these tumours and animals hyperimmunized with X‐irradiated tumour cells. Tumour‐bearing and hyperimmunized mice were shown to produce humoral and cell‐mediated tumour‐immune responses by membrane immunofluorescence tests and migration inhibition assays of peritoneal exudate cells. In normal mice more than 90% of injected fibrosarcoma cells became localized in the lungs whereas the lymphosarcoma cells were localized primarily in both liver and lungs. The fibrosarcoma cells showed a decreased localization in the lungs and a corresponding increase in the livers, lymphoid tissues and kidneys of sensitized mice. However, the lymphosarcoma cells showed greater localization in the lungs of tumour‐bearing and immunized mice compared with that in control animals. Prior treatment of both tumour types with Vibrio cholerae neuraminidase modified the pattern of cell arrest to some extent in both normal and tumour‐sensitized mice. The relevance of these expriements as a model of the haematogenous metastasis of cancer cells is discussed.