Effect of cell aggregation on intravenous tumor transplantation.

We have studied how the presence of cell aggregates affects the pattern of intravenously induced “experimental metastases” from two syngeneic murine tumors. Aggregates were produced mechanically by centrifugation, or chemically by a lectin (wheat–germ agglutinin). Compared to well-dissociated suspensions, aggregated suspensions tended to give a greater total metastasis volume in the lungs of recipient mice. Disaggregated suspensions, on the other hand, gave rise to more extrapulmonary metastases. Presumably, aggregates are preferentially retained in lung vessels, while single cells are let through to other sites. In addition, our results show that tumor aggregates are not necessary to induce metastases. Nor are aggregates superior to single cells in producing tumor growth when the total metastasis yield is considered.