Transcriptional Reprogramming Regulates Tumor Cell Survival in Response to Ionizing Radiation: a Role of p53.

Senexin B, a non-toxic selective inhibitor of cyclin-dependent protein kinases 8 and 19 (CDK8 and CDK19), in combination with γ-photon irradiation in doses of 2-10 Gy increased the death of colon adenocarcinoma cell line HCT116 (intact p53) in a logarithmically growing culture, which was accompanied by the prevention of cell cycle arrest and a decrease of "senescence" phenotype. The effect of senexin B in cells with intact p53 is similar to that of Tp53 gene knockout: irradiated HCT116p53KO cells passed through the interphase and died independently of senexin B. The inhibitor reduced the ability of cells to colony formation in response to irradiation; p53 status did not affect the effectiveness of the combination of radiation and senexin B. Thus, the CDK8/19 inhibitor senexin B increased cell sensitivity to radiotherapy by mechanisms dependent and independent of p53 status.

Suppression of the Antioxidant System and PI3K/Akt/mTOR Signaling Pathway in Cisplatin-Resistant Cancer Cells by Quercetin.

We studied the effect of quercetin on ovarian adenocarcinoma SKOV-3 cell line and isogenic subline SKOV-3/CDDP resistant to the anticancer drug cisplatin. It was found that in resistant cells, quercetin in a concentration of 100 µM that causes a decrease in the cell viability suppressed the expression of genes encoding the key antioxidant enzymes (SOD2, CAT, GPX1, and HO-1), transcription factor Nrf2, and kinases of the PI3K/Akt/mTOR signaling pathway. In parental cells, quercetin, on the contrary, increased the expression of these genes. The results confirm the redox-dependent regulation induced by quercetin and its opposite nature in cisplatin-sensitive and cisplatin-resistant cancer cells.

Suppression of PI3K/Akt/mTOR Signaling Pathway and Antioxidant System and Reversal of Cancer Cells Resistance to Cisplatin under the Effect of Curcumin.

The effect of curcumin on the resistance of SKOV-3 human ovarian adenocarcinoma cells to cisplatin was studied. It was found that curcumin induced "reversal" of cancer cells resistance, which was associated with suppression of the expression of genes encoding the key antioxidant enzymes (SOD1, SOD2, CAT, GPX1, and HO-1) and transcription factor Nrf2 and a decrease in the expression of genes encoding kinases of the PI3K/Akt/mTOR signaling pathway. The obtained results confirm the role of redox-dependent regulation in the "reversal" of cancer cells resistance to cisplatin.

Inhibition of the c-Myc Oncogene by the Aureolic Acid Group Antibiotics.

GC-rich stretches in the DNA minor groove are the established intracellular targets for the aureolic acid group of antibiotics such as olivomycin A and its semisynthetic analogue olivamide. We demonstrated here that both antibiotics at nanomolar concentrations inhibited transcription of the c-Myc oncogene in cultured human tumor cells. The mechanism of transcriptional inhibition did not require the full-length binding site for Sp1, a GC-dependent transcriptional factor. GC quartets with the nucleotide sequences optimal for drug binding are sufficient for c-Myc transcriptional block by the aureolic acid derivatives.

Recombinant Spidroin Films Attenuate Individual Markers of Glucose Induced Aging in NIH 3T3 Fibroblasts.

The effect of bioresorbable materials on aging in cultured mouse NIH 3T3 fibroblasts treated with elevated glucose concentration was investigated. The cells were grown on films produced from the silkworm fibroin and rS1/9, a recombinant analog of Nephila clavipes spidroin 1. Exposure to 50 mM glucose of the cells grown on uncoated glass support resulted in the cell growth retardation. The average areas of the cells and nuclei and the percentage of apoptotic cells increased, whereas the amount of soluble collagen decreased. In contrast, on the fibroin and spidroin films, the cell density and the percentage of 5-bromo-2'-deoxyuridine (BrdU)-positive cells were higher vs. the cells grown on the glass support. The films protected NIH 3T3 fibroblasts from the glucose-induced death. The most prominent effects on the cell density, BrdU incorporation, and apoptosis prevention were observed in the cells cultured on spidroin films. Unlike the cells grown on glass support (decrease in the soluble collagen production) or fibroin (no effect), production of soluble collagen by the cells grown on spidroin films increased after cell exposure to 50 mM glucose. Molecular analysis demonstrated that 50 mM glucose upregulated phosphorylation of the NFκB heterodimer p65 subunit in the cells grown on the glass support. The treatment of cells grown on fibroin films with 5.5 mM or 50 mM glucose had no effect on p65 phosphorylation. The same treatment decreased p65 phosphorylation in the cells on the spidroin films. These results demonstrate the anti-aging efficacy of biomaterials derived from the silk proteins and suggest that spidroin is more advantageous for tissue engineering and therapy than fibroin.

Genome Editing As an Approach to the Study of in Vivo Transcription Reprogramming.

CDK8-mediated transcriptional reprogramming is essential for an extensive gene expression. Constitutive knockouts of the cdk8 gene are lethal at the morula stage. For modeling transcriptional reprogramming in an adult organism, we investigated the possibility to attenuate the CDK8 kinase activity with a F97G mutation in exon 3 of the cdk8 gene. According to preliminary experimental data, this mutation should lead to a decrease in CDK8 kinase activity. To edit the genome of laboratory mice, the CRISPR/Cas9 technology was used, in which the introduction of a double-stranded gap occurred at a distance of 128 nucleotide pairs from the planned site of the introduced mutation. To introduce the mutation, a matrix for homologous repair was used as part of plasmid DNA, with homologous arms 903 and 484 bp in the 5'-3' region from the point of double-stranded rupture, respectively. As a result, mice with site-specific target mutations in exon 3 of the cdk8 gene were obtained. We for the first time demonstrated a high efficacy of the mutation 128 bp apart from the site of double-strand break. Viable animals with the F97G mutation in the catalytic domain of CDK8 kinase were obtained for the first time. The resulting cdk8 mutant mice will be used in subsequent studies to simulate the processes involving transcription reprogramming.

Redox-Dependent Expression of Genes Encoding NADPH Oxidase 5 and the Key Antioxidant Enzymes during Formation of Drug Resistance of Tumor Cells to Cisplatin.

Expression of genes that plays a significant role in the control of cellular redox homeostasis was studied during the development of drug resistance of human ovarian adenocarcinoma SKOV-3 cells to cisplatin. It was found that the development of drug resistance was accompanied by enhanced expression of the genes encoding the key antioxidant enzymes (SOD2, CAT, GPX1, and HO-1) and transcription factor Nrf2, as well as reduced expression of the gene encoding NOX5 isoform of NADPH oxidase. The results testify to redox-dependent development of the adaptive antioxidant response as an important process in the mechanism of formation of resistance to cisplatin.

[Complexes of antiparallel telomeric G-quadruplex d(TTAGGG)4 with carboxymethyl tetracationic porphyrins].

Porphyrins comprise a chemical class widely used in drug design. Cationic porphyrins may bind to DNA guanine quadruplexes. We report the parameters of binding of 5,10,15,20-tetrakis(N-carboxymethyl-4-pyridinium)porphyrin (P1) and 5,10,15,20-tetrakis(N-etoxy-carbonylmethyl-4-pyridinium)porphyrin (P2) to antiparallel telomeric G-quadruplex formed by d(TTAGGG)4 sequence (TelQ). The binding constants (K(i)) and the number of binding sites (N(i)) were determined from absorption isotherms generated from absorption spectra of complexes of P1 and P2 with TelQ. Compound P1 demonstrated a high affinity to TelQ (K1 = (40 +/- 6) x 10(6) M(-1), N1 = 1; K2 = (5.4 +/- 0.4) x 10(6) M(-1), N = 2). In contrast, the binding constants of P2-TelQ complexes (K1 = (3.1 +/- 0.2) x 10(6) M(-1), N1 = 1; K2 = (1.2 +/- 0.2) x x 10(6) M(-1), N2 = 2) were one order of magnitude smaller than the respective values for P2-TelQ complexes. Measurements of quantum yield and fluorescence lifetime of drug-TelQ complexes revealed two types of binding sites for P1 and P2 on the quadruplex oligonucleotide. The 'strong' complexes can result from interaction of the porphyrinswith TTA loops whereas the weaker complexes are formed with G-quartets. The altered TelQ conformation detected by circular dichroism spectra of P1-TelQ complexes can be explained by a disruption of a G-quartet. We conclude that peripheral carboxy groups contribute tothe high affinity of P1 for the antiparallel telomeric G-quadruplex.

[The natural triterpenoid miliacin prevents methotrexate-induced oxidative stress and normalizes the expression of genes encoding the cytochrome P-450 2E1 isoform and glutathione reductase in the liver].

We studied the role of the natural triterpenoid miliacin (3-3-methoxy-Al8-oleanene) in the regulation of oxidative stress in the liver of (CBAxC57B1(6))F1 mice exposed to methotrexate. Miliacin attenuated methotrexate-induced lipid peroxidation as determined by an attenuation of thiobarbituric acid-reacting products in the liver. Furthermore, miliacin normalized the expression of genes encoding the 2e1 isoform of cytochrome P-450 and glutathione reductase that were dramatically dysregulated by methotrexate. These results established the role of miliacin in modulation of redox genes, thereby providing evidence for a new mechanism of organ protection by this triterpenoid.

Identification of phosphorylation sites in aminoglycoside phosphotransferase VIII from Streptomyces rimosus.

We demonstrate for the first time the role of phosphorylation in the regulation of activities of enzymes responsible for inactivation of aminoglycoside antibiotics. The aminoglycoside phosphotransferase VIII (APHVIII) from the actinobacterial strain Streptomyces rimosus ATCC 10970 is an enzyme regulated by protein kinases. Two serine residues in APHVIII are shown to be phosphorylated by protein kinases from extracts of the kanamycin-resistant strain S. rimosus 683 (a derivative of strain ATCC 10970). Using site-directed mutagenesis and molecular modeling, we have identified the Ser146 residue in the activation loop of the enzyme as the key site for Ca2+-dependent phosphorylation of APHVIII. Comparison of the kanamycin kinase activities of the unphosphorylated and phosphorylated forms of the initial and mutant APHVIII shows that the Ser146 modification leads to a 6-7-fold increase in the kanamycin kinase activity of APHVIII. Thus, Ser146 in the activation loop of APHVIII is crucial for the enzyme activity. The resistance of bacterial cells to kanamycin increases proportionally. From the practical viewpoint, our results increase prospects for creation of highly effective test systems for selecting inhibitors of human and bacterial serine/threonine protein kinases based on APHVIII constructs and corresponding human and bacterial serine/threonine protein kinases.

[Casein kinase 2, the versatile regulator of cell survival].

Casein kinase 2 (CK2), a highly conservative, multifunctional serine/threonine protein kinase, is critically important for the regulation of a plethora of processes in eukaryotes, such as cell proliferation, differentiation and death. CK2 is expressed in all tissues; in particular, its amount and activity are elevated in tumor cells. Unlike many regulatory proteins CK2 permanently adopts an active conformation. Of the utmost importance are the anti-apoptotic functions of CK2. This protein kinase is capable of regulating cell survival at multiple levels including DNA repair, NF-kappaB, Wnt, PI3K/Akt and JAK-STAT signaling cascades, chaperones, activation of anti-apoptotic proteins and down-regulation of pro-apoptotic counterparts, in particular, caspases. The versatility of CK2-mediated phosphorylation ensures the survival of tumor cells exposed to stimuli that differ in the origin and mechanisms of cytotoxicity. This manifold mode of CK2-dependent survival makes this enzyme an important target for antitumor therapy.

[Characteristics of complex formation between monomeric and dimeric bisbenzimidazoles and AT-containing polynucleotide].

Double-stranded DNA is a one of the most important intracellular anticancer agent targets. Disturbance of DNA functions as well as DNA structure lead to disorder of such processes as transcription and/or translation thus inducing tumor cells death. Complex formation between novel dimeric bisbenzimidazole DB(7) and poly(dA-dT) duplex in comparison with known monomeric bisbenzimidazole MB(Ac) was investigated in this study. DB(7)-poly(dA-dT) binding constant was determined by fluorescence spectroscopy using Scatchard plot and it values 1.18 x 10(8) M(-1) that is two orders of magnitude larger than MB(Ac) one (2.06 x 10(6) M(-1)). Thus, from findings mentioned above it could be concluded that the presence of two bisbenzimidazole moieties in the ligand structure significantly increases its affinity to the polynucleotide which motivates the synthesis of new potential anticancer drugs based on dimeric bisbenzimidazoles.

Expression of peroxiredoxin 1, 2, 3, and 6 genes in cancer cells during drug resistance formation.

We studied the expression of peroxiredoxin genes (PRDX1, PRDX2, PRDX3, and PRDX6) in human erythroleukemia K652, human breast carcinoma MCF-7, and human ovarian carcinoma SKOV-3 cells during cisplatin resistance development. It was found that drug resistance formation was accompanied by a significant increase in the expression of PRDX1, PRDX2, PRDX3, PRDX6 genes in all cancer cell strains, which confirms the important contribution of redox-dependent mechanisms into the development of cisplatin resistance of cancer cells.

Expression of genes of glutathione transferase isoforms GSTP1-1, GSTA4-4, and GSTK1-1 in tumor cells during the formation of drug resistance to cisplatin.

We studied the expression of genes encoding glutathione-S-transferase isoforms GSTP1-1, GSTA4-4, and GSTK1-1 during the development of the resistance of human erythroleukemia (K562), mammary adenocarcinoma (MCF-7) and ovary adenocarcinoma (SKOV-3) cells to cisplatin (CDDP). It was found that drug resistance development in all three strains of tumor cells is associated with significant increase in hGSTP1 and hGSTA4 gene expression, whereas increased hGSTK1 gene expression was detected only in resistant K562/CDDP and MCF-7/CDDP cells.

PROTAC: targeted drug strategy. Principles and limitations.

The PROTAC (PROteolysis TArgeting Chimera) technology is a method of targeting intracellular proteins previously considered undruggable. This technology utilizes the ubiquitin-proteasome system in cells to specifically degrade target proteins, thereby offering significant advantages over conventional small-molecule inhibitors of the enzymatic function. Preclinical and preliminary clinical trials of PROTAC-based compounds (degraders) are presented. The review considers the general principles of the design of degraders. Advances and challenges of the PROTAC technology are discussed.

[The Pim family of protein kinases: structure, functions and roles in hematopoietic malignancies].

Phosphorylation is the universal regulatory mechanism in key physiological processes such as development, cell differentiation, proliferation, survival and malignant transformation. In this review we analyze serine/threonine protein kinases of the Pim (proviral integration of Moloney virus) family that have been initially discovered in experimental lymphomas. We provide data on gene structure, evolution, functions and substrates of Pim protein kinases. Focusing on Pim-1 as the major isoform, we analyze its role in the biology of hematopoietic malignancies. Pim-1 is a pro-proliferative and pro-survival protein kinase. It is constitutively active due to autophosphorylation, and its downstream partners positively regulate the cell cycle. Pim-1 cooperates with c-Myc oncoprotein in leukemogenesis; furthermore, Pim-1, like the Akt protein kinase, prevents cell death. Thus, Pim kinases are regarded as new therapeutic targets. Finally, we present an original test system f or screening of Pim inhibitors. In this test system the growth of a genetically engineered Escherichia coli strain in the presence of kanamycin is dependent on the phosphorylation of aminoglycoside-3' phosphotransferase VIII by Pim-1: pharmacological inhibition of this phosphorylation increases the bacterial cell lysis.

[Role of the medium acidity in the complexes formation of pyropheophorbide a with albumin and lipoproteins].

The spectral characteristics of the photosensitizer pyropheophorbide a (PPP) complexes with its carriers, that is, serum albumin and low density lipoproteins, were investigated in aqueous solutions at pH 7.4 and 5.0. The acidic pH had no effect on the quantitative parameters of PPP binding to lipoproteins but reduces its affinity for albumin. Differential role of acidification in the binding of PPP to biomacromolecules should be considered in the design of PPP-based drugs given that pH is frequently lowered in the sites of the disease.

The p53 Protein Family in the Response of Tumor Cells to Ionizing Radiation: Problem Development.

Survival mechanisms are activated in tumor cells in response to therapeutic ionizing radiation. This reduces a treatment's effectiveness. The p53, p63, and p73 proteins belonging to the family of proteins that regulate the numerous pathways of intracellular signal transduction play a key role in the development of radioresistance. This review analyzes the p53-dependent and p53-independent mechanisms involved in overcoming the resistance of tumor cells to radiation exposure.

Super-Enhancers in the Regulation of Gene Transcription: General Aspects and Antitumor Targets.

Super-enhancers (genome elements that activate gene transcription) are DNA regions with an elevated concentration of transcriptional complexes. These multiprotein structures contain, among other components, the cyclin-dependent kinases 8 and 19. These and other transcriptional protein kinases are regarded as novel targets for pharmacological inhibition by antitumor drug candidates.

PHF10 subunit of PBAF complex mediates transcriptional activation by MYC.

The PBAF complex, a member of SWI/SNF family of chromatin remodelers, plays an essential role in transcriptional regulation. We revealed a disease progression associated elevation of PHF10 subunit of PBAF in clinical melanoma samples. In melanoma cell lines, PHF10 interacts with MYC and facilitates the recruitment of PBAF complex to target gene promoters, therefore, augmenting MYC transcriptional activation of genes involved in the cell cycle progression. Depletion of either PHF10 or MYC induced G1 accumulation and a senescence-like phenotype. Our data identify PHF10 as a pro-oncogenic mechanism and an essential novel link between chromatin remodeling and MYC-dependent gene transcription.