Biologic properties of factor-independent nonadherent hematopoietic and adherent preadipocyte cell lines derived from continuous bone marrow culture.

Cell lines dependent for growth upon an inducer T-cell synthesized glycoprotein factor interleukin-3 have been derived from continuous mouse bone marrow cultures. These factor-dependent (FD) lines have been shown to be multipotential (erythroid/basophil/neutrophil) or (eosinophil/basophil/neutrophil); or are unipotent basophil or neutrophil granulocyte cell lines. Both classes of cloned FD lines have maintained self-renewal in vitro for several years with absolute growth dependence on freshly added IL-3. In four instances, factor-independent (FI) variant cell lines were derived, one by subculture in medium containing hydrocortisone and 25% horse serum and three by evolution of variants from cloned FD lines. One class of (FI) lines demonstrated adherent fibroblast-like morphology with differentiation to differentiated adipocytes in medium containing 10(-5) hydrocortisone. A second class of cell lines evolved from cloned FD lines and each grew in suspension culture to a saturation density over 10-fold greater than that for the parent FD line (greater than 10(7)/ml) and each contained no detectable hematopoietic cellular differentiation markers by histochemistry or cell surface receptors. In contrast to IL-3 dependent cell lines, (FI) cell lines failed to differentiate to mature granulocyte morphology in diffusion chambers in vivo. The FI cell lines formed no detectable CFUs in vivo, did not reconstitute hematopoiesis in irradiated mice and did not form tumors in vivo. The failure of the (FI) lines to form tumors and lack of detectable hematopoietic differentiation capacity indicates that these lines may represent an intermediate state between normally regulated hematopoietic cellular self-renewal and malignant transformation.