lactoferrin and Leukemia--Erythroblastic--Acute

In this study, we sought to identify factors responsible for the positive modulation of lactoferrin (LF), a neutrophil-specific, secondary-granule protein gene. Initial reporter gene transfection assays indicated that the first 89 base pairs of the LF promoter are capable of directing myeloid-specific LF gene expression. The presence of a C/EBP site flanked by 2 Sp1 sites within this segment of the LF promoter prompted us to investigate the possible role of these sites in LF expression. Cotransfection studies of LF-89luc plasmid with increasing concentrations of a C/EBPalpha expression vector in myeloid cells resulted in a linear transactivation of luciferase reporter activity. Electrophoretic mobility shift assays found that the C/EBP site is recognized by C/EBPalpha and that both LF Sp1 binding sites bind the Sp1 transcription factor specifically in myeloid cells. Mutation of either Sp1 site markedly reduced activity of the LF-89luc plasmid in myeloid cells, and neither Sp1 mutant plasmid was transactivated by a C/EBPalpha expression plasmid to the same extent as wild-type LF-89luc. We also transfected LF-89luc into Drosophila Schneider cells, which do not express endogenous Sp1, and demonstrated up-regulation of luciferase activity in response to a cotransfected Sp1 expression plasmid, as well as to a C/EBPalpha expression plasmid. Furthermore, cotransfection of LF-89luc plasmid simultaneously with C/EBPalpha and Sp1 expression plasmids resulted in an increase in luciferase activity greater than that induced by either factor alone. Taken together, these observations indicate a functional interaction between C/EBP and Sp1 in mediating LF expression. (Blood. 2000;95:3734-3741)

Topics: Animals; Base Sequence; Binding Sites; CCAAT-Enhancer-Binding Proteins; Cell Nucleus; DNA-Binding Proteins; Gene Expression Regulation, Neoplastic; Humans; Lactoferrin; Leukemia, Erythroblastic, Acute; Luciferases; Mice; Molecular Sequence Data; Nuclear Proteins; Promoter Regions, Genetic; Recombinant Fusion Proteins; Sp1 Transcription Factor; Transcription Factors; Transfection; Tumor Cells, Cultured

The ability of malleobactin to mobilize iron from transferrin and lactoferrin was examined in an equilibrium dialysis assay in the absence of bacteria. Malleobactin was capable of removing iron from both transferrin and lactoferrin at pH values of 7.4, 6.0, and 5.0. However, the levels of iron mobilization were greater for transferrin than for lactoferrin at all the pH values used in the assay. The ability of Pseudomonas pseudomallei to acquire iron from 30% iron-saturated transferrin and K562 human erythroleukemic cells was compared in parallel cultures as described previously (J. H. Brock, P. H. Williams, J. Liceaga, and K. G. Woldridge, Infect. Immun. 59:3185-3190, 1991). P. pseudomallei U7 tended to acquire iron from transferrin. In contrast, P. aeruginosa PAO and P. cepacia Pc275C acquired iron from both sources. P. cepacia H1721, which does not produce detectable siderophores, but can utilize malleobactin, pyochelin, and azurechelin as iron sources, was used in a similar experiment. Addition of malleobactin resulted in iron uptake only from transferrin, whereas pyochelin and azurechelin promoted iron uptake from both sources. When the siderophores were incubated with K562 cells alone, malleobactin was less efficient at removing iron from cells than pyochelin and azurechelin. It was also determined that malleobactin was less effective in binding to or entering cells than pyochelin and azurechelin. These results suggest that malleobactin can acquire iron more effectively from host proteins than from cellular sources. Pyochelin and azurechelin can acquire cell-derived iron in addition to iron bound to host proteins.

Topics: Burkholderia pseudomallei; Humans; Hydrogen-Ion Concentration; Iron; Lactoferrin; Leukemia, Erythroblastic, Acute; Siderophores; Transferrin; Tumor Cells, Cultured

The present report describes effects of lactoferrin treatment on the development of erythroleukemia in the spleen of mice infected with Friend virus complex (FVC). Lactoferrin (LF) treatment was carried out in mice for up to 2 weeks at a total dose of 200 micrograms per mouse. The treatment was started at Days 7 and 14 prior to viral infection and Days 0, 1, 3, 7, and 11 after viral infection. Spleens were analyzed 14 days after viral infection. In mice whose treatment was initiated at Days 0 and 1, few leukemic cells were present in the spleen. Most of them appeared in clumps in the red pulp. No leukemic cells were seen in the white pulp. The white pulp was greatly enlarged. In mice whose treatment was initiated at Day 3, leukemic cells began to spread out in the red pulp and encroached upon the white pulp. The white pulp was enlarged and clearly visible. In mice whose treatment was initiated at Days 7 and 11, many leukemic cells were present in the red pulp. The white pulp was infiltrated by leukemic cells and became less discernible. The morphologic features of the spleen in mice whose treatment was initiated at Day 7 or 14 prior to viral infection were similar to those of untreated groups. Leukemic cells not only filled most of the cordal space in the red pulp but also invaded the white pulp. Many leukemic cells were seen in venous sinuses. When infected mice responded to LF treatment, the general architecture of the red pulp remained intact and the white pulp was enlarged but not infiltrated by leukemic cells.

Topics: Animals; Female; Friend murine leukemia virus; Lactoferrin; Lactoglobulins; Leukemia, Erythroblastic, Acute; Leukemia, Experimental; Mice; Organ Size; Spleen; Time Factors