Role of natural killer cells in controlling local tumor formation and metastatic manifestation of different 3LL Lewis lung carcinoma cell clones.

Using two cell clones derived from 3LL Lewis carcinoma; an NK-resistant (designated A6) and an NK-susceptible (designated F2) clone, we investigated the effect of the NK system on local tumor growth and metastasis. Both clones generated local tumors at the inoculation site somewhat faster in NK-deficient (bg/bg) than in normal mice. In addition, these tumors grew slightly faster in the bg/bg mice. However, the effect of the NK system on the metastatic spread of these clones was much more prominent. The F2 cells were profoundly less metastatic than the A6 cells when inoculated into normal mice, whereas in the NK-deficient mice, both clones were highly metastatic. Thus, the NK system appears to be effective primarily in controlling the metastatic spread of the 3LL cells and has a lesser effect on their local tumor formation.