Production of human lactoferrin in transgenic tobacco plants

Production and characterization of human lactoferrin (hLf) in transgenic tobacco is reported. We have engineered two constructs containing either the native signal peptide from human lactoferrin or the signal peptide from sweet potato sporamin fused to human lactoferrin encoding cDNA. N-terminal sequences of rhLf purified from tobacco were identical to Lf from human milk for both constructs. The tobacco rhLf presents a molecular mass closely identical to native protein. Overall sugar composition shows the presence of plant specific xylose while sialic acid is absent. Binding parameters of the recombinant molecule to both Jurkat lymphoblastic T-cells or HT29-18-C1 enterocytes are similar to those of human lactoferrin isolated from milk.

Effects of human lactoferrin on NK cell cytotoxicity against haematopoietic and epithelial tumour cells

Lactoferrin is an iron-binding glycoprotein implicated in particular in the control of immune functions and cell proliferation. We have investigated its involvement, at inflammatory concentrations, in cancer progression. We report that lactoferrin has a significant effect on natural killer (NK) cell cytotoxicity against haematopoietic and breast epithelial cell lines. Lactoferrin increases cytolysis at a low concentration (10 micrograms/ml) while at a high concentration (100 micrograms/ml) it modulates cytolysis depending on the target cell phenotype. By pre-treatment of either NK cells or target cells with lactoferrin, we have demonstrated that the lactoferrin effect is due both to a modulation of NK cell cytotoxicity and the target cell sensitivity to lysis. Lactoferrin binds to 91% of the naturally heterogeneous CD56dim/bright NK cell population and increases the NK cell cytotoxic activity at low concentrations. High concentrations of lactoferrin seem to be toxic for the CD56bright NK cells and decrease NK cell cytotoxicity. Lactoferrin also exerts an effect on target cells depending on the cell phenotype. It does not modify the susceptibility to lysis of haematopoietic cells such as Jurkat and K-562 cells, but does significantly increase that of the breast and colon epithelial cells. We have also demonstrated that lactoferrin inhibits epithelial cell proliferation by blocking the cell cycle progression.

Production of acidic and basic fibroblast growth factor by the hormone-independent breast cancer cell line MDA-MB-231

Normal, as well as the majority of malignant, mammary epithelial cells will proliferate upon stimulation by FGFs. However estrogen-independent MDA-MB-231 cells (which are able to grow in vitro in serum-free medium) are not significantly stimulated by exogenous FGFs even though they possess high and low affinity receptors for these growth factors. Biological assays, measuring CCL39 fibroblast proliferation or PC12 pheochromocytoma cell neurite outgrowth, demonstrated the presence of FGF activity in MDA-MB-231 cell extracts and also in the culture medium conditioned by these cells. This biological activity decreased in the presence of neutralizing anti-FGF antibodies. Using immunohistochemical methods FGF1 and FGF2 immunoreactivity was detected in MDA-MB-231 cells. After purification by heparin-Sepharose chromatography and Western blot analysis, M(r) 18000 molecules showed the same physicochemical characteristics as FGFI and FGF2. These results demonstrate the production and release of FGF related molecules by MDA-MB-231 cells and suggest an autocrine stimulation of these cells.