Cancer metastasis and intercellular communication

: Three highly metastatic and two weakly metastatic clones were obtained from a spontaneously arising mammary adenocarcinoma in an SHR rat. The difference in their capacity to generate metastatic activity was recognized only when the cancer cells were inoculated s.c. but not when they were inoculated i.v. This evidence possibly indicates that the difference in the metastatic capacity of these clones is caused by different potential for detachment from the primary site and for intravasation during the various steps of metastasis. The motility of cancer cells, which is one of the most important factors in these steps of metastasis, showed no difference between the highly and weakly metastatic clones. However, the motility of cancer cells was decreased after coculture with fibroblasts, and the motility of weakly metastatic clones was more strongly decreased than that of highly metastatic clones. On the other hand, using a dye transfer method to examine the relationship between the metastatic capacity of cancer cells and the capacity of cancer cells to form junctional communications with normal fibroblasts, it was demonstrated that the communication between highly metastatic clone cells and fibroblasts was poorer in comparison to that between weakly metastatic clone cells and fibroblasts. These results suggest that the motility of cancer cells is inhibited by interaction with normal fibroblasts, and that one of these forms of interaction may be mediated by intercellular communication.