Qualitative functional deficiency of affinity-purified lactoferrin from neutrophils of patients with chronic myelogenous leukemia, and lactoferrin/H-ferritin-cell interactions in a patient with lactoferrin-deficiency with normal numbers of circulating leukocytes

Bcr-Abl kinase promotes cell cycle entry of primary myeloid CML cells in the absence of growth factors

Cell cycle control of both immature and differentiated primary myeloid normal and chronic-phase chronic myeloid leukaemia (CML) cells to growth factor deprivation was studied. CD34+ cells were cultured in liquid culture. After removal of growth factors for 48 h normal cells were very efficiently arrested with the fraction of cells in S phase reduced by 70.8 +/- 6.5% in CD34+ and 50.5 +/- 4.2% in CD34- cells. In contrast, a significantly higher proportion of leukaemic cells remained in S phase. The fraction of S-phase cells was reduced by only 29.3 +/- 5.7% in CD34+ CML cells and 21.2 +/- 3.8% in CD34- cells. This abnormal negative cell cycle control in leukaemic cells was specific for growth factor deprivation. Reaction to IFN-alpha and TNF-alpha treatment was identical both in normal and CML cells. Equal quantities of the cytokines TNF-alpha, IL-1alpha, IL-1RA and IL-6 were produced by CML and normal cells. However, production of GM-CSF, with a median of 11 +/- 5 pg/ml, was found only in the supernatants of CML cells. But antibodies to GM-CSF did not restore growth factor dependence of the leukaemic cells. The defect was completely corrected by the abl-specific tyrosine kinase inhibitor CGP 57148 without effecting cell cycle control of normal cells. Our results demonstrate a directly Bcr-Abl-dependent defective response of both immature and differentiated primary myeloid CML cells to growth factor deprivation.

Physical characteristics and polymerization during iron saturation of lactoferrin, a myelopoietic regulatory molecule with suppressor activity

Lactoferrin (LF) has been implicated in normal regulation of myeloid blood cell production in vitro and in vivo and abnormalities in LF-cell interactions have been associated with progression of leukemia and other hematopoietic disorders. LF may be clinically useful and for this reason we studied selected biochemical characteristics of LF. Purified human milk LF was saturated with iron from solution and analyzed by gel electrophoresis, ion-exchange and gel filtration chromatography. The metalloprotein was found to contain several molecular weight species on polyacrylamide gels. High resolution ion-exchange chromatography demonstrated the binding of LF to both anionic and cationic media under identical conditions indicating a bipolar charge distribution. Gel filtration studies revealed a tetramerized form of LF, the formation and stability of which was dependent on the ionic strength of the solution.