Biological Activity of Agaricinic Acid Nanoparticles against Human Hepatoma HepG2 Cells.

A stable preparation of agaricinic acid nanoparticles was obtained. The mean hydrodynamic size of nanoparticles according to photon correlation spectroscopy was 200 nm and zeta potential was -57 mV. Cytotoxic activity of agaricinic acid nanoparticles against human HepG2 hepatoma cells was evaluated. Nanoparticles with a low concentration of agaricinic acid stimulated and with high concentration - suppressed metabolic activity and viability of hepatoma cells. The EC50 for the stimulating effect was 32.8 µg/ml, and the IC50=602.1 mg/ml. The preparation of agaricinic acid nanoparticles can be used in medicine as a potential antitumor agent.

ROS and RNS signalling: adaptive redox switches through oxidative/nitrosative protein modifications.

Over the last decade, a dual character of cell response to oxidative stress, eustress versus distress, has become increasingly recognized. A growing body of evidence indicates that under physiological conditions, low concentrations of reactive oxygen and nitrogen species (RONS) maintained by the activity of endogenous antioxidant system (AOS) allow reversible oxidative/nitrosative modifications of key redox-sensitive residues in regulatory proteins. The reversibility of redox modifications such as Cys S-sulphenylation/S-glutathionylation/S-nitrosylation/S-persulphidation and disulphide bond formation, or Tyr nitration, which occur through electrophilic attack of RONS to nucleophilic groups in amino acid residues provides redox switches in the activities of signalling proteins. Key requirement for the involvement of the redox modifications in RONS signalling including ROS-MAPK, ROS-PI3K/Akt, and RNS-TNF-α/NF-kB signalling is their specificity provided by a residue microenvironment and reaction kinetics. Glutathione, glutathione peroxidases, peroxiredoxins, thioredoxin, glutathione reductases, and glutaredoxins modulate RONS level and cell signalling, while some of the modulators (glutathione, glutathione peroxidases and peroxiredoxins) are themselves targets for redox modifications. Additionally, gene expression, activities of transcription factors, and epigenetic pathways are also under redox regulation. The present review focuses on RONS sources (NADPH-oxidases, mitochondrial electron-transportation chain (ETC), nitric oxide synthase (NOS), etc.), and their cross-talks, which influence reversible redox modifications of proteins as physiological phenomenon attained by living cells during the evolution to control cell signalling in the oxygen-enriched environment. We discussed recent advances in investigation of mechanisms of protein redox modifications and adaptive redox switches such as MAPK/PI3K/PTEN, Nrf2/Keap1, and NF-κB/IκB, powerful regulators of numerous physiological processes, also implicated in various diseases.

Endostatin: current concepts about its biological role and mechanisms of action.

Endogenous inhibitors of angiogenesis are proved to be a major factor preventing the emergence of clinically manifested stages of human cancer. The protein endostatin, a 20-kD proteolytic fragment of type XVIII collagen, is one of the most active natural inhibitors of angiogenesis. Endostatin specifically inhibits the in vitro and in vivo proliferation of endothelial cells, inducing their apoptosis through inhibition of cyclin D1. On the surface of endothelial cells, endostatin binds with the integrin alpha(5)beta(1) that activates the Src-kinase pathway. The binding of endostatin with integrins also down-regulates the activity of RhoA GTPase and inhibits signaling pathways mediated by small kinases of the Ras and Raf families. All these events promote disassembly of the actin cytoskeleton, disorders in cell-matrix interactions, and decrease in endotheliocyte mobility, i.e., promote the suppression of angiogenesis. Endostatin displays a high antitumor activity in vivo: it inhibits the progression of more than 60 types of tumors. This review summarizes results of numerous studies concerning the biological activity and action mechanism of endostatin.

Tumor angiogenesis inhibitors.

Formation of the blood supply system is a critical step in malignant transformation of neoplasms which results in the penetration of tumor cells into neighboring tissues and metastatic growth. Significant progress in the elucidation of mechanisms underlying tumor angiogenesis and the discovery of a great diversity of biomolecules involved in its regulation have culminated in the development of a radically new approach to antitumor therapy based on the search for efficient inhibitors of tumor angiogenesis. This review is devoted to the analysis of action mechanisms and expression of the major endogenous inhibitors involved in regulation of tumor and physiological angiogenesis. The antiangiogenic effects of the majority of currently known synthetic inhibitors are considered in the context of their roles in the main steps of tumor angiogenesis. Possible applications of antiangiogenic therapy in the chemotherapy of cancer diseases are discussed.

Molecular mechanisms of tumor angiogenesis.

The maintenance of growth of malignant tumors is closely related with the development of the vascular network supplying the tumor with blood. The vascularization of tumor tissue is similar to physiological angiogenesis, but in tumors it has some specific features. During the last 25 years a vast number of biomolecules have been found and described which are involved in the regulation of tumor angiogenesis. This review considers the action mechanisms and specific features of expression of the main angiogenic growth factors, such as the vascular endothelium growth factor (VEGF), angiopoietins (Ang-1, Ang-2), and the basic fibroblast growth factor (bFGF). The roles of cytokines, growth factors, proteolytic enzymes, and cell adhesion molecules in the regulation of the key steps of blood vessel generation in the tumor are considered. The significance of angiogenesis in the treatment of oncological diseases and possible approaches for inhibition of the regulatory signals of angiogenic factors are discussed.

Cytotoxic and antitumor activities of doxorubicin conjugates with the epidermal growth factor and its receptor-binding fragment.

The epidermal growth factor (EGF) receptor is expressed at high levels on many types of tumor cells, such as squamous carcinoma, breast cancer and endothelial cells. We studied targeted delivery of the anticancer drug doxorubicin (DOX) using EGF and its receptor-binding fragment (EGFfr) to cells able to overexpress EGF receptors. EGF-DOX and EGFfr-DOX conjugates were synthesized via a glutaraldehyde bridge. The cytotoxic activities (CTA) of the conjugates were studied in vitro in different tumor cell lines (MCF-7Wt, MCF-7AdrR, B16) and endothelial cells using MTT-test. The antitumor effects of the conjugates were examined in vivo in mice with a subcutaneous B16 model. In the case of MCF-7Wt cells, CTA of EGF-DOX and EGFfr-DOX conjugates exceeded 7.7- and 68-fold that of free DOX. Besides, the conjugates effectively decreased the drug resistance of MCF-7AdrR cells. CTA of the conjugates against endothelial cell cultures markedly exceeded that of free DOX. It is of note that proliferating endothelial cells were much more sensitive to the effects of the conjugates than confluent endothelial cells. Administration of EGF-DOX and EGFfr-DOX conjugates significantly inhibited tumor growth and increased the mean life span of experimental animals by 46 and 48.5%, respectively.

Cytotoxic activity, accumulation, and intracellular distribution of anthracycline antibiotics and their conjugates with the epidermal growth factor in sensitive and resistant MCF-7 cells.

Cytotoxic activities, accumulation levels and dynamics, and intracellular distribution of the anthracycline antibiotics doxorubicin (DR) and carminomycin (CM) in the free forms or within conjugates with the epidermal growth factor (EGF) were for the first time compared in human breast carcinoma cell lines MCF-7Wt and MCF-7AdrR. The cytotoxic activities of DR and CM conjugates with EGF were higher than the cytotoxic activities of the free antibiotics in both cell lines. The accumulation levels of the free anthracyclines in both cell lines were lower than those of the conjugates and significantly depended on the cell sensitivities to the antibiotics. On receptor-mediated endocytosis of the anthracycline-EGF conjugates, the accumulation levels did not significantly depend on the cell sensitivities to the antibiotics. Both DR and CM, either free or conjugated with EGF, were mainly accumulated in nuclei. The free drugs were accumulated more rapidly, and the accumulation rates of both free and EGF-conjugated CM were higher than those of DR preparations. The intracellular distribution of the free antibiotics significantly depended on the cell sensitivities to the anthracyclines, whereas the cell sensitivities had no effect on the distribution of the conjugates between the nucleus and cytoplasm. The rate of intracellular degradation of DR and CM delivered to target cells within conjugates with EGF was twice lower than that of the free antibiotics. The difference in the accumulation levels and dynamics and in the intracellular distribution of the free and conjugated DR and CM is likely to underlie the higher cytotoxic activities of the anthracycline conjugates with EGF compared to the free drugs.

Antitumor activity of alpha fetoprotein and epidermal growth factor conjugates in vitro and in vivo.

Conjugates of carminomycin (Cm) with alpha-fetoprotein (AFP) and epidermal growth factor (EGF) were prepared and their cytotoxic activities were studied in vitro. Both conjugates showed cytotoxic activity which exceeded that of free Cm in tumor cell cultures of MCF-7, SKOV3, QOS, P388 and B16 cells. The antitumor effects of the conjugates were studied in vivo in mice with subcutaneous tumors of B16 and P388 cells. The Cm-AFP and Cm-EGF conjugates inhibited tumor growth and noticeably increased the mean life span in experimental animals. Our results suggest that the therapeutic activity of Cm can be significantly enhanced by conjugation to AFP or EGF.

Antitumor activity of alpha-fetoprotein conjugate with doxorubicin in vitro and in vivo.

alpha-Fetoprotein (AFP) was conjugated with doxorubicin (DR) using glutaraldehyde as a cross-linking agent. The protein/DR molar ratio in the conjugate is 1 : 2. Cytotoxic activities (CTA) of the AFP-DR conjugate and of the free DR were compared using human mammary gland carcinoma cells, both DR-sensitive (MCF-7Wt) and DR-resistant (MCF-7AdrR). The CTA of the AFP-DR conjugate was fivefold higher than the CTA of the free DR for sensitive cells of the MCF-7Wt line and sevenfold higher for resistant cells of the MCF-7AdrR line. The CTA of the AFP-DR conjugate was also studied in vitro using the proliferating endothelium taken for a model of endothelial cell lining of blood vessels that supply the tumor. The AFP-DR conjugate was shown to have a high CTA for the endothelial cells (IC50 = 2.5 nM); thus, the conjugate is suggested to manifest an anti-angiogenic effect in vivo. The antitumor activity of the AFP-DR conjugate was studied using mice with inoculated melanoma B16 tumors. The treatment of animals significantly inhibited the tumor growth (>97%) and increased by 60% the mean life span of the animals compared to the control. The high antitumor efficiency of the AFP-DR conjugate and the possibility to significantly decrease the tumor cell resistance to DR make this conjugate a promising chemotherapeutic agent.

Cytotoxic action of conjugates of alpha-fetoprotein and epidermal growth factor with photoheme, chlorines, and phthalocyanines.

Covalently bound conjugates of alpha-fetoprotein (AFP) and epidermal growth factor (EGF) with photoheme (PH), 3-desvinyl-3-formylchlorine p6 (Chl p6), chlorine e6 (Chl e6), aluminum disulfochloride phthalocyanine (PC(Al)), and cobalt octa-4,5-carboxyphthalocyanine (teraphthal, TP(Co)) were synthesized. Their molar ratios were 1:4 for AFP-cytotoxin conjugates (cf. 1:10 for AFP-TP(Co)) and 1:2 for EGF conjugates (cf. 1:1 for EGF-PC(Al)). Dark toxicity of both protein conjugates with PH, chlorines, and PC(Al) was much lower than their phototoxicity. Studies on phototoxicity demonstrated that PC(Al) conjugates with AFP and EGF and also EGF-Chl p6 were the most effective. The cytotoxic activity (CTA) of AFP-PC(Al) and EGF-Chl p6 was 80% and of EGF-PC(Al) 64% higher than the CTA of the free drugs. Conjugates with TP(Co) were much more toxic on their activation with ascorbic acid (AA): in the presence of AA the CTA of AFP-TP(Co) and of EGF-TP(Co) was 19 and 61.1% higher, respectively, than the CTA of the free TP(Co).

Targeting phthalocyanines to tumor cells using epidermal growth factor conjugates.

Epidermal growth factor (EGF) was used as a vector for targeted delivery of phthalocyanines to tumor cells. The conjugates of EGF with disulfochloride aluminum phthalocyanine [Pc(Al)] and disulfochloride cobalt phthalocyanine [Pc(Co)] were synthesized. The cytotoxic activity of the conjugates against the human breast carcinoma cell line MCF-7 was determined. The cytotoxic activity of the EGF-Pc(Co) conjugate was 4.5 times higher than that of the EGF-Pc(Al) conjugate. The antitumor activity of the EGF-Pc(Co) conjugate was also studied in vivo in murine melanoma B16. Compared to free Pc(Co), intravenous injections of Pc(Co) conjugated with EGF inhibited tumor development and increased mean life span and mean survival time of experimental animals.

[Secretion of recombinant human epidermal growth factor into the periplasm in Escherichia coli cells]. / Sekretsiia v periplazmu rekombinantnogo épidermal'nogo faktora rosta cheloveka v kletkakh Escherichia coli.

Secretion vectors were constructed in which a synthetic gene of human epidermal growth factor (hEGF) joined with a gene coding for the leader peptide to one of the E. coli outer membrane major proteins (OmpF) is controlled by tac promoter. The increase of the hEGF yield was achieved by the multiplication of the gene copies. The hEGF in bacterial cells was secreted into periplasm. The recombinant protein was isolated by means of reverse phase chromatography as almost homogenous preparation (greater than 98%), the yield being 7 mg/l bacterial culture. The sequence of twenty-five N-terminal amino acid residues of the isolated hEGF coincided with that of the natural protein. The preparation proved to be biologically active.

[Expression of a synthetic gene for human interleukin-4 in E. coli cells. Preparation of a biologically active protein]. / Ekspressiia sinteticheskogo gena interleikina-4 cheloveka v kletkakh E. coli. Poluchenie biologicheski aktivnogo belka.

Expression E. coli plasmid were constructed in which the human interleukin-4 (hIL4) synthetic gene is controlled by tac promoter. The expression level of the gene depends on the distance between RBS and the initial codon ATG, with the maximal production in case of the nine base pair distance. The recombinant protein, accumulated in the inclusion bodies, was solubilized, renaturated, and purified to homogeneous, biologically active preparation, the yield being 2 mg/g wet cells.

[Recombinant interleukin-3 expression system in E. coli]. / Sistemy ékspressii v E. coli rekombinantnogo interleikina-3.

Plasmid pTOTE2IL3 (III) has been constructed, expressing an artificial human interleukin-3 (hIL3) gene under conditions of the induced protein biosynthesis. Levels of the recombinant protein synthesis have been compared in several E. coli strains containing expression plasmids pTE2IL3 (I) (constitutive biosynthesis) and (III) (induced biosynthesis). Optimal combinations of the expression plasmids and the bacterial strains are of importance. A simple and effective method has been elaborated for isolation, purification and renaturation of the recombinant protein accumulated in inclusion bodies.

[Isolation of recombinant interleukin-3 produced by E. coli]. / Vydelenie rekombinantnogo interleikina-3, produtsiruemogo E. coli.

A synthetic gene coding for human interleukin-3 (hIL3) was cloned in the plasmid pTE2IL3, the gene expression being controlled by the phage fd PVIII promotor and the phage T7 gene 10 translational enhancer. Under constitutive biosynthesis conditions in E. coli, the accumulation of recombinant hIL3 (in the inclusion bodies) was up to 30-40% of the total cell protein. An effective procedure of the hIL3 isolation is suggested. The hIL3 was solubilized in 5 M guanidinium chloride, renaturated and purified to homogeneity by a single chromatographic step. The protein's yield was 34 mg/g wet cells. The isolated hIL3 showed a specific biological activity.

[Chemical-enzymatic synthesis of the amplifier of the T7 phage gene 10 and function of its structural elements]. / Khimiko-fermentativnyi sintez usilitelia transliatsii gena 10 faga T7 i funktsiia élementov ego struktury.

The translational enhancer (TREN) sequence of the phage T7 gene 10 (in full and also its proximal or distal parts) have been obtained by chemical-enzymatic synthesis and cloned into the plasmids immediately before the human interleukin 3 (hIL3) artificial gene. Expression levels of the hIL3 gene in E. coli in these constructions show that the region controlling the specific activity is placed in distal part of TREN more than 40 nucleotides upstream from the initiation codon.

Dialdehyde ATP derivative as an affinity modifier of the Na+,K(+)-ATPase active site.

Interaction of Na+,K(+)-ATPase from pig kidney in various conformational states with the dialdehyde analogue of ATP, alpha,alpha-(9-adenyl)-alpha'-D-(hydroxymethyl)diglycolaldehyde triphosphate ester (oATP), has been studied. This interaction leads to an enzyme modification which was shown to be of the affinity type according to the following criteria. 1. oATP can be hydrolyzed by Na+,K(+)-ATPase and prevent inhibition of ATPase activity by gamma-[4-(N-2-chloroethyl-N-methylamino)]benzylamide ATP, indicating that it interacts with Na+,K(+)-ATPase in the enzyme active site. 2. oATP irreversibly inhibits ATP-hydrolyzing activity of Na+,K(+)-ATPase; the extent of inactivation is decreased in the presence of 20 mM ATP and depends on the ion composition of the modification medium. The inhibition and ATP protection are maximal in Na+,Mg2(+)-containing buffer. 3. The value of [14C]oATP incorporation into the alpha subunit is proportional to the degree of enzyme inactivation at low (less than 0.1 mM) concentration of oATP and, on extrapolation to complete inhibition, corresponds to incorporation of 1.05 mol reagent/mol alpha subunit. 4. Tryptic hydrolysis of the isolated oATP-modified alpha subunit and subsequent separation of the peptides revealed only one labelled fragment with a molecular mass of about 10 kDa. Localization of the modified fragment in the alpha-subunit polypeptide chain is discussed. A morpholine-like structure was shown to be formed as a result of the modification.