Search

Previously, we found a significant increase in TRAIL (TNFα-related apoptosis-inducing ligand) resistance of acute myeloid leukemia (AML) cells in multicellular aggregates in vitro that simulate the location of leukemia cells in the bone marrow. In this study, we tried to assess whether the increased resistance of the AML cells to the cytotoxic effect of TRAIL in multicellular aggregates in vitro can be associated with the launch of mechanisms mediated by cell differentiation or the acquisition of a pro-inflammatory phenotype. The phenotype of THP-1 cells in aggregated and disaggregated cultures was studied in comparison with the phenotype of a disaggregated THP-1 cell culture exposed to factors that induce monocyte-like differentiation or pro-inflammatory phenotype. It was found that an increase in the TRAIL resistance of the THP-1 cells in the aggregated culture was accompanied by the appearance of signs characteristic of monocyte-like differentiation and a pro-inflammatory phenotype. The results are of interest for developing approaches for suppressing TRAIL resistance of AML cells in human bone marrow.

Creation of implants for the restoration of ligaments and tendons in their complete/massive injury is an urgent task. The efficacy of the restoration of completely resected Achilles tendons after implantation of a new material consisting of absorbable pledged threads Dar-Vin USP 5/0 and conductive nonofibrous scaffolds of polyhydroxybutyrate placed around the threads into the zone of defect was studied in Wistar rats. Either nanofibrous implant (experiment) or pledged threads (control 1) were placed into the zone of completely resected Achilles tendon (control 1), or the postresection wound was sutured without placement of any material (control 2). It was stated that from 2nd to 13th week after implantation of nanofibrous implant the animals from the experimental group used their hind paws in full volume. In control groups 1 and 2 the animals moved with difficulties. In the experimental group of animals in 6 and 13 weeks after implantation a soft tissue regenerate connecting the calcanean tuber and gastrocnemius muscle was present with the absence of gastrocnemius muscle contracture as compared with the control groups. Histologic examination showed the similarity of the regenerate on nanofibrous implant with the native Achilles tendon. Thus, the suggested implant ensured functional and morphologic restoration of totally resected Achilles tendon in rats and can be considered as a perspective prototype of new materials initiating effective regeneration of ligaments and tendons in their massive injuries.

Background: Therapeutic efficiency in treatment of acute myeloid leukemia (AML) ranges from 20 to 45%. One of the causes of the latter is a drug resistance acquired by leukemic cells under the influence of treatment with antitumor medicines. More important cause is a development of the primary resistance of myeloid leukemic cells to induction of cellular death associated with elemental microenvironment within the bone marrow. Studying primary resistance is very important, and first of all, to prevent development of drug resistance of leukemic cells and, correspondingly, to increase the efficiency of medicamental therapy. Aim: To study the mechanisms of primary resistance of AML cells to induction of cellular death. Materials and methods: Human AML cells of THP-1 line and mononuclear cells of the bone marrow were used in the study of patients with diagnosed AML. Multicellular aggregates were formed during cell cultivating on the 1.5% agarose. To cut off intercellular adhesion, the cells were cultivated in the medium with methylcellulose (0.9%). The viability of the cells was assessed by reduction of Alamar Blue indicator. Results: Within multicellular aggregates, about 75±5% of THP-1 cells were resistant to the activity of recombinant protein izTRAIL, 70±5% – to etoposide, and 40±7% – to sorafenib. Cutting off intercellular contacts decreased the resistance to them. Within multicellular aggregates of primary mononuclear cells, 45±5% of cells were resistant to sorafenib, 57±4% – to etoposide, and all cells were resistant to izTRAIL. Cutting off intracellular adhesion reduced the resistance to sorafenib and etoposide but not to izTRAIL. Conclusion: In multicellular aggregates, AML cells of THP-1 line and mononuclear cells of the bone marrow showed increased resistance to activity of recombinant protein izTRAIL, etoposide, and sorafenib. Diminishing intracellular adhesion in the medium including methylcellulose decreases cellular resistance to cytotoxic agents.

Suppression of resistance in acute myeloid leukemia cells to TRAIL-induced apoptosis in multicellular aggregates, was studied using small molecule inhibitors of the activation of the transcription factor NF-kB - NF-k9 Activation Inhibitor IV and JSH-23 at non-toxic concentrations. NF-kB Activation Inhibitor IV and JSH-23 reduced resistance in the acute myeloid leukemia cells in multicellular aggregates to cytotoxic action of recombinant protein izTRAIL. It is shown that the use of these inhibitors decreased the phosphorylation of the RelA (p65) as a main marker activation of the transcription factor NF-kB. We discuss a possible reason for increasing resistance in acute myeloid leukemia cells to TRAIL-induced apoptosis in multicellular aggregates.

One of the major causes of low efficiency of the therapy for acute myeloid leukemia is drug resistance of leukemic cells. Microenvironment plays a key role in formation of the phenotype of leukemic cell drug resistance. Investigation of the mechanisms of microenvironment-mediated drug resistance is important to identify novel pharmacological targets for the acute myeloid leukemia therapy. We studied the role of cell aggregation in the drug resistance of leukemic cells. We showed the increased resistance of acute myeloid leukemia cells THP-1 to bortezomib, doxorubicin and fludarabine in multicellular aggregates. In the multicellular aggregates of THP-1 with the higher drug resistance, cell proliferation activity did not change, while the intracellular level of anti-apoptotic protein Bcl-2 increased. Inhibition of the aggregation of THP-1 cells prevented drug resistance. This work demonstrates the involvement of cell aggregation in the formation of drug resistance phenotype in leukemic cells.