Relationship between invasion and metastasis of tumor cells

This work was done to examine the relationship between invasion and metastasis of different types of tumor cells. Three kinds of tumor cells were studied: a mouse uterine cervix carcinoma (U14) with high metastatic potential; a human nasopharyngeal carcinoma (CNE-2Z) with high metastatic potential; and a human uterine cervix carcinoma (CC801) with low metastatic potential. CNE-2Z and CC801 were implanted subcutaneously in the footpads and subcapsularly in the testes of nude mice, respectively. U14 was implanted both in the footpads and subcapsularly in the testes of inbred 615-strain mice. With each of these animal models, the extent of tumor invasion could be divided into grades I-IV. The metastasis of tumor cells was found to depend upon: 1) the malignant characteristics of the tumor cells; 2) the degree of local invasion; 3) the presence of tumor cells in the lymphatic ducts and blood vessels; and 4) the organ specificity of metastatic development. Metastasis was most often found when invasion reached a high degree (grades III to IV).