[SUPPRESSION OF TUMOR GROWTH AFTER XENOGRAFTING OF HUMAN COLORECTAL CARCINOMA CELLS].

Previously we've described the obtainment of a subpopulation of cancer stem cells from a human colorec- tal carcinoma cell line MIP101. These cells possess elevated clonogenic and tumorigenic capacities. According to our data, depletion of stem compartment in a cancer cell population blocks its tumorigenicity. The current work is dedicated to the comparison of tumorigenic potential between cell populations with enriched or depleted stem compartment. We show that tumor growth following xenografting of enriched stem cell population can be suppressed by intramuscular injections of ganciclovir. Thus, we report a method to obtain a cell population with high Oct4 promoter expression within the MIP101 colorectal carcinoma cell line and to eliminate these cells from the population in vitro as well as in vivo.

[Model in vivo to study the transdifferentiation of the somatic cell into urothelium].

Development of reconstructive therapy of the urinary tract using pluripotent and somatic stem cells, for example mesenchymal stem cell (MSCs), recently goes through the stage of experimental studies. These studies include investigation of the main functions of MSCs and urothelium lining from inside the organs of the urinary tract. An important role in the regulation of proliferation and differentiation of urothelium belongs to EGF and Wnt-beta-catenin signaling pathways which activity may be accessed by the level of Her-4 and Tcf3,4, accordingly. We found here that MSCs labeled by transgenic green fluorescence protein (GFP) did not produce in vitro Her-4 and Tcf3,4 but activated their production after transfer into cryoinjured bladder of the syngenic mouse. After MSCs transplantation, GFP was detected in the bladder by RT-PCR and was colocalized with Her-4 or Tcf3,4 in a few urothelium cells detected by immunohistichemical staining with specific antibodies. These results suggest that MSCs labeled by GFP may be used as a good model to study transdifferentiation of somatic cells into urothelium.

[Monoclonal antibodies to human spleen ferritin. II. Localization of epitopes and quantitative parameters of antigen binding]. / Monkonal'nye antitela k ferritinu selezenki chekoveka. II. Lokalizatsiia épitopov i kolichestvennye parametry sviazyvaniia antigena.

The interaction of three monoclonal antibodies with human spleen ferritin has been studied. Using titration of various monoclonal antibody-containing media with the immobilized antigen, the specific content of active antibodies capable of binding to ferritin was determined, which was 22-27% for ascitic fluids, 35-50% for total mouse IgG and 88% for affinity-purified HSF102 antibody. Using [125I]ferritin and a novel computer-aided technique for determining the antigen-antibody binding, the affinity constants were obtained which ranged from 6.10(8) to 3.10(9) M-1. The monoclonal antibodies inhibited by 77-95% the binding of rabbit polyclonal antibodies to ferritin. This result is suggestive of a compact distribution on the ferritin surface of immunodominant epitopes forming clusters of closely related antigenic sites recognized by monoclonal and rabbit polyclonal antibodies. Competitive binding and additivity assays revealed that the epitope for the HSF102 antibody was sterically remote from the epitopes recognized by HSF101 and HSF103 antibodies to allow for noncompetitive binding of two different monoclonal antibodies. The competition between HSF101 and HSF103 antibodies pointed to the overlapping of their epitopes. It was found that no more than four [125I]IgG molecules could simultaneously be bound to one ferritin molecule which reflected the maximal valency of this antigen during its interaction with IgG antibodies.

[Monoclonal antibodies to human spleen ferritin. I. Preparation and study of the interaction with isoferritin and apoferritin]. / Monoklonal'nye antitela k ferritinu selezenki cheloveka. I. Poluchenie i issledovanie vzaimodeistviia s izoferritinami i apoferritinom.

Three monoclonal antibodies to human spleen ferritin were produced and their interaction with soluble and immobilized ferritins studied. An immunoassay was developed to monitor the interaction of soluble biotinylated ferritin and the antibody with subsequent separation of the soluble complexes on streptavidin-cellulose. Analysis of immunoreactivities of a series of isoferritins (human liver, spleen, heart and equine spleen ferritins) revealed that all the three monoclonal antibodies bound to only human L-type ferritins (spleen and liver ferritins), suggesting a high species- and tissue specificity of these antibodies. The monoclonal antibodies were specifically directed against conformation-dependent antigenic determinants as could be evidenced from the lack of their binding to the subunits of the dissociated ferritin. The affinity of the monoclonal antibody for the ferritin deprived of iron (apoferritin) was higher than that for native ferritin due to the greater conformational flexibility of the apoferritin molecule. The latter property may underly a complete loss of immunoreactivity by the apoprotein adsorbed on the polystyrene surface as a result of conformational changes induced in the apoferritin molecule by adsorption. These findings provide additional support for recognition by all of the three antibodies of conformational antigenic epitopes in the ferritin molecule.