Tumor-cell-platelet aggregation does not correlate with metastatic potential of rat 13762NF mammary adenocarcinoma tumor cell clones.

The ability of tumor cells to induce platelet aggregation has been correlated with their capacities to colonize the lungs of experimental animals. We tested this hypothesis by studying the ability of cloned, low-passage metastatic tumor cell lines derived from rat 13762NF mammary adenocarcinoma to aggregate rat platelets in vitro and in vivo, and we then compared this activity to metastatic potential by determining the incidence of lung metastasis after subcutaneous or intravenous inoculation of the tumor cell clones into syngeneic rats. Our results failed to show a correlation between in vitro platelet-aggregating activity and metastatic potential. In this system we could not detect platelet-aggregation activity with the most metastatic tumor clone, while least metastatic clone clearly possessed high platelet-aggregating activity. In addition, by measuring changes in blood platelet and fibrinogen concentrations at various intervals following intravenous injection of tumor cell clones, we were able to confirm in vivo the observed in vitro differences in their platelet-aggregating activities. Thus, platelet aggregating activity is heterogeneously expressed among 13762NF cell clones and appears unrelated to spontaneous or experimental metastasis in this tumor system.