Invasive and metastatic capacity of revertants of LFA-1-deficient mutant T-cell hybridomas.

From the highly metastatic TAM2D2 T-cell hybridoma we have previously generated three independent mutants that were deficient in the surface expression of the adhesion molecule Leukocyte Function-associated Antigen 1 (LFA-1). Both the invasive capacity and the metastatic potential of these mutants were greatly reduced compared with TAM2D2 cells (F.F. Roossien et al., J. Cell Biol., 108: 1979-1985, 1989). We now show that, during in vivo transplantation, LFA-1 is reinduced in these mutants. From such revertant cell populations obtained after two to three i.p. passages, we isolated clones with different LFA-1 levels. Of each of the three mutant cell lines, the clone with the highest and the one with the lowest LFA-1 level were selected for further study. Invasiveness in fibroblast monolayers correlated strongly with LFA-1 level; i.e., the low-LFA-1 clones (mean LFA level, approximately 10% of TAM2D2) invaded as poorly as the original mutants, whereas the high-LFA-1 clones (greater than 25% of TAM2D2) were highly invasive. Metastatic potential was determined after tail vein injection of 10(6) cells in syngeneic AKR mice. A difference was observed between high- and low-LFA-1 clones, albeit less striking than previously found between LFA-1-negative mutants and parental TAM2D2 cells. The high-LFA-1 clones developed metastases in more mice (76 versus 43%) and earlier (mean survival, 30 versus 37 days). These results provide further evidence for an important role of LFA-1 in invasion and metastasis of mouse T-cell hybridomas.