Teleocidin-induced modulation of growth and cell interaction in microenvironment-dependent mouse leukemias

Teleocidin is a new tumor-promoting substance chemically unrelated to phorbol groups. Its biological effects on thymic microenvironment-dependent leukemias derived from AKR spontaneous leukemias were studied in vitro in comparison with 12-O-tetradecanoylphorbol 13-acetate (TPA), a representative tumor promoter of the phorbol group. Teleocidin stimulated the in vitro growth of 21 out of 31 symbiotic cell lines in the absence of growth-supporting stromal cells. All the responders to teleocidin were responsive also to TPA and the degree of growth stimulation in each cell line was comparable. Both promoters could inhibit the symbiotic complex formation with thymic epithelial cells probably by affecting the cytoskeleton. All symbiotically cultured AKR leukemia cells expressed Thy-1.1 antigen, but their expression of Lyt-1.2 and Lyt-2.1 was heterogenous. There was no direct correlation between teleocidin-responsiveness and Lyt-phenotypes of the leukemia cells.