Volume 44, Nº 5 (2018)

Although understanding of the molecular biology of cancer has advanced and medicine has an impressive arsenal of chemotherapeutic drugs, the problem of tumor resistance to individual drugs and drug combinations has not yet been resolved. Known mechanisms of cancer chemoresistance do not explain the reason for such a phenomenon as “apoptosis-induced proliferation,” where cells dying under the effect of the therapy secrete some signaling molecules into the extracellular medium to promote proliferation, survival, and acquisition of a more aggressive phenotype of neighboring cancer cells. The nature of this unexpected phenomenon is only now beginning to be partially clarified, but the nature of such signaling between apoptotic cancer cells and their neighboring cells remains largely unknown. For this reason, in this review we discuss currently known types of intercellular communication of tumor cells, give specific examples of important secreted molecules involved in signaling between cancer cells, and describe possible cell interactions contributing to the progress of cancer outgrowth.

The possibility of mass spectrometric sequencing of peptides without the need for the conventional MS/MS analysis has been demonstrated experimentally. The peptide hydrolysate was fractionated by reversephase chromatography on a microbore column. The eluate fraction was injected into the mass spectrometer via an electrospray ion source that directly coupled a liquid chromatography instrument to a time-of-flight mass spectrometer (HPLC-MS). Fragmentation of the peptides eluted from the column was performed in the mass spectrometer interface by varying the voltage difference between the mass spectrometer nozzle and skimmer. A restricted set of intensive peaks of y-ions, which corresponded to sequential cleavage of all amino acids from the peptide, was obtained. The ratios of the y-ion peak intensities to the background were (5−100)/1. The presence of Lys and Arg in the peptides provided for a substantial increase of informative peak intensity in the mass spectra. The mass spectra of short peptides (up to 10 residues) were processed manually, whereas the Proteos hardware and software system was used to process the fragmentation results for a long N-terminal peptide of the human hemoglobin α-chain.

Adenine phosphoribosyltransferase (APRT) from a thermophilic bacterial strain Thermus thermophilus НВ27 (TthHB27APRT) belongs to the family of type I phosphoribosyltransferases and catalyzes the magnesium-dependent transfer of 5'-phosphoribosyl group from 5'-phosphoribosylpyrophosphate to N9 adenine nitrogen with formation of adenosine-5'-monophosphate and pyrophosphate. The crystals of the recombinant enzyme suitable for X-ray study were grown in a capillary using the counter-diffusion technique. Crystals with unit-cell parameters α = 69.860 Å, b = 82.160 Å, c = 91.390 Å, α = 90.00°, β = 102.58°, and γ = 90.00° belong to the space group Р2₁ and contain six enzyme monomers in the asymmetric unit. The set of X-ray data from grown crystals was collected on a Spring-8 synchrotron radiation facility (Japan) and three-dimensional structure of the enzyme was solved at 2.7-Å resolution by molecular replacement method using the BALBES software. The polypeptide fold in the enzyme monomer and the structure of biologically active dimer were described. Based on the comparison with structures of homologous APRTs from a thermophilic strain ThtHB8 and Homo sapiens, positions of active site and a number of functionally important amino acids were located.

The effect of the coiled-coil (CC) region of the α-helical inserted domain of Escherichia coli Lon protease (Ec-Lon) on the functional activity of the enzyme has been characterized. A recombinant form des-CC(G5)-Lon in which the deleted CC fragment is replaced by a pentaglycine peptide has been obtained and investigated. It has been shown that the CC region is involved in the recognition of the nucleotide nature by the enzyme and the interaction of the enzyme with the protein substrate. It has been also established that the CC region is necessary for the formation and functioning of the ATPase and peptidase active centers, the occurrence of allosteric interactions between them, and for the implementation of proteolysis by a unique processive mechanism.

The daunorubicin and doxorubicin anthracycline antibiotics were modified with the Inula helenium L. sesquiterpene lactones (alantolactone, isoalantolactone, and alloalantolactone) and with their epoxy derivatives. Antiproliferative properties of these conjugates were studied on tumor and normal cell lines. The daunorubicin conjugates with the sesquiterpene lactones (isoalantolactone, allantolactone, and alloalantolactone) and with their epoxy derivatives were found to exhibit the higher activity against human tumor cell lines than the corresponding doxorubicin conjugates. The daunorubicin conjugate with epoxyisoalantolactone proved to be the most effective compound, because it was more cytotoxic than daunorubicin towards a number of cell lines, including those daunorubicin-resistant, and did not affect normal human cells.

Reactions of natural epoxyalantolactone with primary and secondary amines, which lead to hydrated benzo[g]furo[4,3,2-cd]indolones and eudesmane-type amino derivatives, respectively, have been studied. Epoxyalantolactone conjugates have been synthesized with the involvement of pharmacophoric amines, and their cytotoxic activity toward some tumor cell lines has been tested. The involvement of the signaling pathway of protein p53 in the death of tumor cells, the contribution of oxidative stress, and the induction of apoptosis have been investigated in experiments in vitro.