Human bone marrow fibroblastic cells can inhibit clonogenic growth of K562 cells

The influence of human bone marrow fibroblastic cells (FC) on the proliferation of K562 leukemic colony-forming cells (LCF-C) was studied. FC derived from normal subjects and patients with acute leukemia were used. The growth of LCF-C was evaluated by colony-forming efficiency in soft agar. Inhibition of leukemic colony formation was produced by FC from normal subjects and patients with acute leukemia. While the degree of inhibition by FC from patients with acute lymphocytic leukemia was almost the same as that by those from the normal subjects, that by FC from patients with acute nonlymphocytic leukemia was lower than that by those from normal individuals. Both conditioned media obtained from FC and contact of their FC with LCF-C in dishes for four hr inhibited leukemic colony formation. These data show that leukemic stem cells are inhibited by bone marrow FC through cell-to-cell contact or humoral factors derived from FC.