Volume 42, Nº 6 (2016)

In spite of all the advances in cancer treatment made in recent years, one of the main problems in this field that remains extremely urgent is the development of drug resistance to the chemotherapeutic agents currently in use due to clonal microevolution of tumor tissue. Numerous publications devoted to the study of cationic antimicrobial peptides (AMPs) as molecular factors of the innate immune system suggest that these compounds possess significant therapeutic potential and can be considered as candidates for the role of not only antimicrobial, but also next-generation anticancer drugs. AMPs are characterized by a variety of mechanisms of cytotoxic action that can lead to either necrosis or apoptosis of the target cells. These effects are based on the selective interaction with the membranes of tumor cells, which have a number of similarities, in structural and physiological aspects, with the microbial membranes. AMPs were found to be able to inhibit tumor growth by interrupting the formation of its vascular network. The antitumor effect of AMPs may also be enhanced by the modulation of host immune system, as previously observed for their antimicrobial effects. The described properties of AMPs give hope for the development of new drugs that will be able to overcome the resistance of tumor cells.

Natural killer cells (NK cells) are traditionally attributed to the innate immune system. It is considered that previously received stimuli have little effect on the functioning of these immune cells. Indeed, NK cells even without prior sensitization provide a rapid effector response against tumor, virus-infected, or otherwise damaged cells. They have a limited repertoire of receptors, the expression of which does not require somatic recombination. However, recent data indicate that NK cells may acquire the properties specific to adaptive immune cells. In particular, NK cells have been shown to possess the features of immunological memory, namely, the ability to more quickly and effectively respond to a repeated stimulus. The mechanisms of memory acquisition in NK cells differ from those implemented in T and B lymphocytes and are still rather vague. Presumably, some of these mechanisms underlie the significant phenotypic and functional NK cell diversity emerging during their differentiation. The recent data accumulated in this area considerably change the existing immunology paradigm, which postulates a clear delineation of the adaptive and innate immune cells. The published data on phenotypic and functional characteristics of NK cells and particular changes in these characteristics during NK cell differentiation and generation of memory-like NK cells are reviewed.

Pancreatic cancer is one of the most aggressive tumor types characterized by chemotherapy resistance and high metastatic activity. Recent studies revealed new genes, which are likely to be actively involved in the regulation of the processes occurring in the pancreas, as well as in the development of cancer in this organ. This review is devoted to the description of one of the recently revealed genes, KLF5, which seems to be a promising target for therapeutic intervention in the most widespread type of pancreatic cancer, ductal adenocarcinoma.

WasCFP, a pH-dependent green fluorescent protein with a tryptophan-based chromophore (Thr65-Trp66-Gly67) in anionic state, was designed from a cyan precursor mCerulean. In this study, the three-dimensional structure of WasCFP has been determined by an X-ray method at pH 5.5, pH 8.0 and pH 10.0, with a resolution of 1.14, 1.25 and 1.5 Å, respectively. We show that changes in the acidity of the media are accompanied by a synchronous change of the side chain conformations of the residues in the near-chromophore environment. Subsequent changes in the local H-bond network interacting with the chromophore lead to considerable alterations in the protein spectral properties as a consequence of reversible processes of ionization-protonation of the Trp chromophore. These experimental results have been supported by quantum chemistry calculations.

A molecule of the major blood protein albumin contains 34 cysteine residues involved in disulfide bonds and one unpaired SH-group of residue Cys34. Normally, 20–30% of these SH-groups are oxidized and form disulfide bonds or the derivatives of sulfenic, sulfinic, and sulfonic acids. The goal of the present work was to study the influence of the degree of oxidation of sulfhydryl groups on the capacity of albumin for glycation. Commercially available human albumin containing 0.4 moles of sulfhydryl groups per 1 mole of the protein (nonmercaptalbumin) was used. Disulfide bonds in this preparation were reduced with dithiothreitol to 0.7 mole/mole to give mercaptalbumin. The preparations were incubated for three weeks with glucose at a concentration of 5 and 50 mM. The content of ketoamine, a glycation product, was determined by the colorimetric method, the content of pentosidine (glycation end product) was analyzed by fluorescence, and the content of SH-groups was determined using the Ellman’s reagent. Changes in the structure and properties of the protein during glycation were studied by fluorescence and HPLC. During the incubation of both albumin preparations with 5 mM glucose, no significant increase in the ketoamine content was observed, whereas the incubation with 50 mM glucose was accompanied by a considerable accumulation of ketoamine. It was found that the greatest amount of ketoamine under these conditions forms in nonmercaptalbumin; in this case, the intensity of tryptophan fluorescence decreases. The intensity of pentosidine fluorescence increases with increasing content of ketoamine. The results obtained enable the conclusion that the oxidation of free SH-groups of the protein changes its conformation; as a result, the glycation of earlier hidden sites becomes possible, and the degree of protein glycation increases.

Conjugates of recombinant human tumor necrosis factor alpha (TNFα) and alendronic acid linked through the protein sulfhydryl, carboxyl, and amino groups were obtained with crosslinking agents of different types. The conjugation reactions were conducted in solution and on a solid phase. Unlike the conjugation reactions in solution, the method involving immobilization of active components on a hydroxyapatite column was shown to result in the conjugates with a specified stoichiometry and a high degree of homogeneity. The TNFα conjugates retained the specific cytolytic activity and demonstrated the higher affinity to hydroxyapatite, an analogue of the bone mineral matrix, than TNFα.

We have developed a technology for the production of polymeric nanoparticles containing the incorporated phosphorescent label (europium ions–naphthoyltrifluoroacetone complexes) and streptavidin that is covalently bound on the surface. The aggregation-stable biospecific nanoparticles (40–60 nm in diameter) include up to 2000 molecular tags/particle and retain biological activity and stable phosphorescence for at least 20 months. They can be used in phosphorescence analysis (PHOSPHANTM)-based biochip technology as an effective detector system to record phosphorescence from microzones (microarrays) printed on the well bottoms of standard polystyrene microplates. The creation of a dense monolayer on the surface of a microzone requires up to 10⁸ particles/microarray, or 10⁹ particles/mm² of area; this is in good agreement with theoretical estimates. The detection limit is as low as 300–400 phosphorescent nanoparticles per a microzone with an area of ~0.1 mm². It has been demonstrated in the model of thyroid stimulating hormone (TSH) detection in filter paper dried blood that the newly developed detector system is five times more sensitive than the conventional methods of multiplex PHOSPHAN (with Pt-coproporphyrin phosphorescent label) and lanthanide immune fluoroassay (with fluorescent Eu³⁺ chelate complexes registered in the enhancement solution). The sensitivity of phosphorescent nanoparticle-based detector system is as low as 6.8 × 10⁵ molecules/1.5 μL sample, which corresponds to a TSH concentration of 1.5 × 10^–14 M.

Three-steps, one-pot synthesis of 2-amino-4-(hydroxyphosphinyl)butyric acid from dibutyl ester of vinylphosphinic acid was carried out with an overall yield of 66%. 3-Aminopropylphosphinic acid was prepared from allylamine in three steps with an overall yield of 56%. These improved protocols allowed to obtain these commercially unavailable phosphinic analogues of glutamic acid and GABA for testing on potential molecular targets.