Approbation of the Cancer Treatment Approach Based on the Eradication of TAMRA+ Cancer Stem Cells in a Model of Murine Cyclophosphamide Resistant Lymphosarcoma.

BACKGROUND/AIM: We previously have described the "3+1" tumors cure approach consisting of individual time schedule of cyclophosphamide and dsDNA preparation administrations. The aim of the study was to adapt the "3+1" approach based on eradication of cancer stem cells to the model of murine ascitic cyclophosphamide-resistant lymphosarcoma (RLS). MATERIALS AND METHODS: Adaptation of the "3+1" approach includes the identification of the timing to disrupt the tumorigenic potential of a certain tumor. RESULTS: The proposed therapeutic scheme allowed complete reduction of primary RLS ascites in experimental animals. However, reduction of primary ascites due to the complementary action of cyclophosphamide and dsDNA was inevitably followed by the development of a secondary one, most likely arising from a solid carcinomatous formation in the peritoneal wall. CONCLUSION: The "3+1" approach resulted in the elimination of cancer stem cells, and, as a consequence, in the complete reduction of RLS ascites.

Features of monocyte-derived dendritic cells encompassing a rare subpopulation of cells that are capable of natural internalization of extracellular dsDNA.

The present study demonstrates that monocyte-derived dendritic cells (moDCs) produced in vitro using a GM-CSF and IFN-α differentiation protocol encompass a rare (∼5%) subpopulation of cells showing classical dendritic cell morphology and capable of natural internalization of extracellular self-DNA. We established that DEFB, HMGB1, LL-37 and RAGE antigens, which mediate the process of DNA internalization, are expressed on the surface of moDCs similar to plasmacytoid dendritic cells. However, in constrast to the latter subpopulation, these cells do not produce interleukin (IL)-37. Nonetheless, the process of DNA internalization was not in direct relation to the presence of the above antigens on the surface of these cells. Dendritic cells were sorted into total and non-DNA-internalizing populations and cytokine production was analyzed at 24-48 hours post-DNA treatment. We show that massive secretion of cytokines by dendritic cells is associated with the dsDNA-internalizing subpopulation. A total pool of IFN-moDCs secrete pro-inflammatory "first-wave" cytokines (IL-2, IL-6, IL-8, TNF-α) at both 24 and 48 hours time points. The anti-inflammatory cytokines IL-4 and IL-10 were found to be modestly induced, whereas GM-CSF, G-CSF, and IFN-γ production was strongly induced. Treatment of moDCs with dsDNA results in the up-regulated transcription of IFN-α, IFN-ß, IFN-γ, IL-8, IL-10, and VEGF by 6 hours. Combined dsDNA + chloroquine treatment has a synergistic effect on transcription of only one of the genes tested, with the pro-inflammatory cytokine IFN-ß displaying the strongest fold induction by 24 hours.

Identification of the xenograft and its ascendant sphere-forming cell line as belonging to EBV-induced lymphoma, and characterization of the status of sphere-forming cells.

BACKGROUND: We have characterized the human cell line arised from the Epstein-Barr virus (EBV) positive multiple myeloma aspirate subjected to the long-term cultivation. This cell line has acquired the ability to form free-floating spheres and to produce a xenograft upon transplantation into NOD/SCID mice. METHODS: Cells from both in vitro culture and developed xenografts were investigated with a number of analytical approaches, including pathomorphological analysis, FISH analysis, and analysis of the surface antigens and of the VDJ locus rearrangement. RESULTS: The obtained results, as well as the confirmed presence of EBV, testify that both biological systems are derived from B-cells, which, in turn, is a progeny of the EBV-transformed B-cellular clone that supplanted the primordial multiple myeloma cells. Next we assessed whether cells that (i) were constantly present in vitro in the investigated cell line, (ii) were among the sphere-forming cells, and (iii) were capable of internalizing a fluorescent TAMRA-labeled DNA probe (TAMRA+ cells) belonged to one of the three types of undifferentiated bone marrow cells of a multiple myeloma patient: CD34+ hematopoietic stem cells, CD90+ mesenchymal stem cells, and clonotypic multiple myeloma cell. CONCLUSION: TAMRA+ cells were shown to constitute the fourth independent subpopulation of undifferentiated bone marrow cells of the multiple myeloma patient. We have demonstrated the formation of ectopic contacts between TAMRA+ cells and cells of other types in culture, in particular with CD90+ mesenchymal stem cells, followed by the transfer of some TAMRA+ cell material into the contacted cell.

Cancer Stem Cells: Emergent Nature of Tumor Emergency.

A functional analysis of 167 genes overexpressed in Krebs-2 tumor initiating cells was performed. In the first part of the study, the genes were analyzed for their belonging to one or more of the three groups, which represent the three major phenotypic manifestation of malignancy of cancer cells, namely (1) proliferative self-sufficiency, (2) invasive growth and metastasis, and (3) multiple drug resistance. 96 genes out of 167 were identified as possible contributors to at least one of these fundamental properties. It was also found that substantial part of these genes are also known as genes responsible for formation and/or maintenance of the stemness of normal pluri-/multipotent stem cells. These results suggest that the malignancy is simply the ability to maintain the stem cell specific genes expression profile, and, as a consequence, the stemness itself regardless of the controlling effect of stem niches. In the second part of the study, three stress factors combined into the single concept of "generalized cellular stress," which are assumed to activate the expression of these genes, were defined. In addition, possible mechanisms for such activation were identified. The data obtained suggest the existence of a mechanism for the de novo formation of a pluripotent/stem phenotype in the subpopulation of "committed" tumor cells.

Efficacy of a new cancer treatment strategy based on eradication of tumor-initiating stem cells in a mouse model of Krebs-2 solid adenocarcinoma.

Krebs-2 solid carcinoma was cured using a new "3+1" strategy for eradication of Krebs-2 tumor-initiating stem cells. This strategy was based on synchronization of these cells in a treatment-sensitive phase of the cell cycle. The synchronization mechanism, subsequent destruction of Krebs-2 tumor-initiating stem cells, and cure of mice from a solid graft were found to depend on the temporal profile of the interstrand cross-link repair cycle. Also, the temporal profile of the Krebs-2 interstrand repair cycle was found to have a pronounced seasonal cyclicity at the place of experiments (Novosibirsk, Russia). As a result, the therapeutic effect that is based on application of the described strategy, originally developed for the "winter repair cycle" (November-April), is completely eliminated in the summer period (June-September). We conclude that оne of the possible and the likeliest reasons for our failure to observe the therapeutic effects was the seasonal cyclicity in the duration of the interstrand repair cycle, the parameter that is central to our strategy.