Use of young nude mice for selection of subpopulations of cells with increased metastatic potential from nonsyngeneic neoplasms.

The purpose of these studies was to investigate whether young (3-wk-old) nude mice, which lack functional T-lymphocytes and demonstrate low natural killer cell activity, could serve as in vivo models for the selection of metastatic subpopulations of cells from heterogeneous allogeneic melanomas. Three-week-old BALB/cAnN or N:NIH(S) nude mice received iv injections of single cells harvested from either the B16 or K-1735 melanoma. Individual pulmonary metastases were harvested 4 weeks later and implanted sc into nude mice to expand the population. Cells from each of these metastases colonized in the lungs of 3-week-old nude mice and 6-week-old normal syngeneic mice with significantly higher efficiency than did cells from the parent tumors. It was concluded that, in addition to being a useful in vivo model for ascertaining the metastatic potential of neoplasms, the healthy young nude mouse could be used for selecting and maintaining tumor cell variants of high metastatic potential room heterogeneous allogeneic tumors.