Lactoferrin binding by leukemia cell lines
Y Yamada, T Amagasaki, DW Jacobsen and R Green
Monocytes and macrophages have receptors for the iron-binding protein
lactoferrin. Lactoferrin acts as a potent inhibitor of granulocyte-
macrophage colony stimulating factor production when it binds to these
cells. Using a rosette assay and immunofluorescence, we have shown that
cultured leukemia cells, including the human erythroid leukemia cell line
K562, also have lactoferrin binding sites. The number of binding sites on
K562 cells was estimated using soluble 59Fe-lactoferrin. Inhibition studies
demonstrate that lactoferrin binding sites are distinct and unrelated to
receptors for transferrin or the Fc portion of IgG, which are present on
K562 cells. However, electrostatic forces may be important for lactoferrin
binding, since other polycationic proteins (eg, protamine) inhibit
lactoferrin binding. Prior treatment of K562 cells with trypsin nearly
abolishes lactoferrin binding. However, these cells recover their ability
to bind lactoferrin when trypsin is removed. Unlike transferrin receptors,
the expression of lactoferrin binding sites is not regulated by cellular
iron status. Cytosine arabinoside arrests the proliferation of K562 cells
and simultaneously leads to a reduction in lactoferrin surface binding,
suggesting that lactoferrin binding may be dependent on cell proliferation.
Volume 70,
Issue 1,
pp. 264-270,
07/01/1987
Copyright © 1987 by The American Society of Hematology
