Promising New Inhibitors of Tyrosyl-DNA Phosphodiesterase I (Tdp 1) Combining 4-Arylcoumarin and Monoterpenoid Moieties as Components of Complex Antitumor Therapy.

Tyrosyl-DNA phosphodiesterase 1 (Tdp1) is an important DNA repair enzyme in humans, and a current and promising inhibition target for the development of new chemosensitizing agents due to its ability to remove DNA damage caused by topoisomerase 1 (Top1) poisons such as topotecan and irinotecan. Herein, we report our work on the synthesis and characterization of new Tdp1 inhibitors that combine the arylcoumarin (neoflavonoid) and monoterpenoid moieties. Our results showed that they are potent Tdp1 inhibitors with IC50 values in the submicromolar range. In vivo experiments with mice revealed that compound 3ba (IC50 0.62 µM) induced a significant increase in the antitumor effect of topotecan on the Krebs-2 ascites tumor model. Our results further strengthen the argument that Tdp1 is a druggable target with the potential to be developed into a clinically-potent adjunct therapy in conjunction with Top1 poisons.

[Novel Glycyrrhetinic Acid Derivative Soloxolone Methyl Inhibits the Inflammatory Response and Tumor Growth in vivo].

Due to wide spreading of inflammatory disease and imperfection of available anti-inflammatory drugs, mainly associated with their serious side effects, searching for new anti-inflammatory agents is a pressing problem. Natural triterpenoids and their synthetic analogs are a promising source of new drugs. In this study, we have investigated the anti-inflammatory and antitumor effects in vivo of the glycyrrhetinic acid derivative soloxolone methyl (SM), or methyl 2-cyano-3,12-dioxo-18ßH-olean-9(ll),l(2)-dien-30-oate. SM was shown to efficiently suppress the development of edema in a mouse model of carrageenan- or histamine-induced acute inflammation. SM also inhibited the tumor growth and reduced the tumor cell count in the ascitic fluid in mice bearing Krebs-2 carcinoma, the development of which is accompanied by an inflammatory process in the surrounding tissues.

Ligand-directed acid-sensitive amidophosphate 5-trifluoromethyl-2'-deoxyuridine conjugate as a potential theranostic agent.

Herein, we report a novel strategy to engineer an acid-sensitive anticancer theranostic agent using a vector-drug ensemble. The ensemble was synthesized by directly conjugating the linoleic acid (LA)-modified branched polyethyleneimine with a chemotherapeutic drug trifluorothymidine. Linoleic acid residues were grafted onto 25 kDa polyethyleneimine (PEI) by treating PEI with linoleic acid chloroanhydride. 5-Trifluoromethyl-2'-deoxyuridine (trifluorothymidine, TFT) was introduced into LA-PEI conjugate by phosphorylating the conjugate with amidophosphate of trifluorothymidine 5'-monophosphate (pTFT), which had been activated by its conversion into the N,N-dimethylaminopyridine derivative. The extent of mononucleotide analog incorporation in the polymer was regulated by the ratio of pTFT to the polymer during the synthesis. Samples containing 20-70 TFT residues per PEI molecule were obtained. The cytotoxicity of PEI-LA-pTFT conjugates decreased with increasing nucleotide content, as examined using the MTT method. Due to the presence of fluorine atoms, TFT-based conjugates could be detected directly in the animals by (19)F magnetic resonance imaging. In addition, the presence of the amidophosphate group in PEI-LA-pTFT conjugates allowed their detection by in vivo(31)P NMR spectroscopy. Indeed, the (31)P NMR signal of a phosphoramide (δ ~ 12 ppm) was observed in the mouse muscle tissue treated with PEI-LA-pTFT conjugate along with the signals from endogenous phosphorus-containing compounds. At the same time, the use of PEI-LA-pTFT conjugate for chemotherapeutic drug delivery is limited due to the low release of pTFT from the carrier. To enhance the release of the drug from the conjugate in the endosomes, PEI-LA polymer was coupled with urocanic acid (UA), which bears imidazole ring and thus can form an acid-labile P-N bond with pTFT. The PEI-LA-UA-pTFT conjugate containing 30 residues of UA and 40 residues of pTFT was tested against the murine Krebs-II ascites carcinoma, grown as an ascetic tumor. The intraperitoneal injection of the conjugates resulted in prolongation of the animals' life and to the complete disappearance of the tumor after three injections.

Tumor rejection in experimental animals treated with radioprotective thiols.

In experimental animals, a systemic treatment with thiols of the mercaptoalkylamine type has affected all of five solid tumors so far investigated. (Three of the tumors were transplanted into the strain of origin.) There was either inhibition of growth or "oncodieresis," i.e., a necrosis and sloughing of tumors conducive to full recovery and repair. Mercaptoalkylamines and derivatives of the type used in our experiments are known to bind to cellular sites by a two-point attachment involving both thiol and amino groups. One of these compounds, cysteamine, was active in its native, unsubstituted form, but did not bring about oncodieresis when either the amino or thiol group, or both, were alkylated. Mercaptopropylamine, the 3-carbon homolog of cysteamine, was less active. Cystamine, a disulfide dimer of cysteamine that has no free reactive sulfhydryl, did not induce any reaction. Thioglycerol, lacking a terminal amino group, had only negligible activity. Rejection was much more striking when treatment was started on the day of inoculation than when started 7 days later. Male mice rejected better than females. Results were inferior when tow of the agents were given simultaneously or together with other radioprotectants, such as L-cysteine, glutathione, dimethyl sulfoxide, or reserpine. Tumor rejection was enhanced when the phosphorylated thioyls, S-2-(3-aminopropylamino)ethylphosphorothioic acid or S-(2-ethylguanidine)phosphorothioci acid, were given simultaneously with the radioprotective serotonin, but there was no synergy of serotonin with the nonphosphorylated compounds S-2-aminoethylisothiouronium bromide or cysteamine. Serotonin alone did not affect the tumors.

A strategy to eradicate well-developed Krebs-2 ascites in mice.

We describe the strategy, which allows curing experimental mice engrafted with Krebs-2 ascites. The strategy is based on the facts that i) Krebs-2 tumor-initiating stem cells (TISCs) are naturally capable of internalizing fragments of extracellular double-stranded DNA (dsDNA); ii) upon delivery into TISCs, these dsDNA fragments interfere with the on-going DNA repair process so that TISCs either die or lose their tumorigenic potential. The following 3-step regimen of therapeutic procedures leading to eradication of Krebs-2 ascites is considered. Firstly, three timed injections of cyclophosphamide (CP) exactly matching the interstrand cross-link (ICL) repair phases that lead to synchronization of ascites cells in late S/G2/M. Secondly, additional treatment of ascites 18 hours post each CP injection (at NER/HR transition timepoint) with a composite dsDNA-based preparation interfering with the NER and HR repair pathways, so that tumorigenic properties of ascites cells are compromised. Thirdly, final treatment of mice with a combination of CP and dsDNA injections as ascites cells undergo apoptotic destruction, and the surviving TAMRA+ TISCs arrested in late S/G2/M phases massively enter into G1/S, when they regain sensitivity to CP+dsDNA treatment. Thus, this regimen assures that no viable cells, particularly Krebs-2 TISCs, remain.

Monophosphoric acid diesters of 7 beta-hydroxycholesterol and of pyrimidine nucleosides as potential antitumor agents: synthesis and preliminary evaluation of antitumor activity.

7 beta-Hydroxycholesterol, which has been shown to be selectively cytotoxic toward tumor cells cultured in vitro, was converted into the corresponding water-soluble phosphoric acid ester and linked to a pyrimidine nucleoside such as 5-fluoro-2'-deoxyuridine or 2'-deoxyuridine. 2-Chlorophenyl phosphorodichloridate (3), without activation, was used directly to phosphorylate the protected oxygenated sterol. The intermediate phosphorylated the 5'-OH group of nucleoside selectively, leading to compounds 1a and 1b after deprotection. These compounds were screened for their antiproliferative activity toward EL-4 murine leukemia cells in vitro and for their antitumor activity against the mice bearing Krebs II ascitic carcinoma in vivo.

The effects of orally administered L-arginine HCl on the development of myeloma tumors in BABL/C mice following the injection of single cell suspensions, cell aggregates or tumor fragments; and on the growth of two ascites tumour cell lines.

When arginine-HCl was added to the drinking water of Balb/c mice the formation of subcutaneous tumours following the injection of single cell suspensions of MPC-11 cells was prevented, however, tumours did develop after injecting tumour fragments or aggregates of suspension-cultured cells. Arginine-HCl had no inhibitory effect upon the production of Krebs II and 6C3HED lymphoma ascites tumours in Balb/c and C3H mice respectively.

A diet containing the lectin phytohaemagglutinin (PHA) slows down the proliferation of Krebs II cell tumours in mice.

Mice injected intraperitoneally with Krebs II cells and then fed on a diet containing the lectin phytohaemagglutinin (PHA) developed ascites tumours more slowly than mice fed on a control diet. After an 8-day period following injection the number of cells recovered from mice maintained on the PHA diet was half that from those fed the control diet. A switch of diet from control to PHA on day 4 after injection resulted in a large decrease in number of tumour cells recovered. Mice injected s.c. also developed tumours at later times when fed on the PHA diet. A quantitative of ribosomes in polysome-containing fractions showed no major differences in protein synthesis in control mice and those fed the PHA diet.

In vivo antitumor activity of 4-amino 4-methyl 2-pentyne 1-al, an inhibitor of aldehyde dehydrogenase.

4-amino-4-methyl-2-pentyne-1-al (AMPAL), a new irreversible inhibitor of aldehyde dehydrogenase (ALDH) has been assayed for its in vitro and in vivo antitumor activity. In vitro, AMPAL inhibits the proliferation and the ALDH activity of L1210 and RBL5 cell lines. In vivo, AMPAL significantly increases the mean survival time of mice i.p. grafted with leukemia (L1210, P815, MBL2, EL4, RBL5 cell lines) or carcinoma cells (Krebs cell line), without haematopoetic toxicity. No carcinostatic effect was observed against the P388 leukemia and the 3LL Lewis lung carcinoma. A possible relationship between the ALDH isoenzyme activity of the tumor and its sensitivity to AMPAL is discussed in the light of previous reports concerning the role of aldehydes in cell growth control.

[Stimulation of the inhibiting effect of interferon on the growth of ascitic carcinoma in relation to host responsiveness and cells]. / Stimuliruiushchee ili ingibiruiushchee vliianie interferona na razvitie astsitnoi kartsinomy v zavismosti ot reaktivnosti organizma i kletok

When Krebs-2 ascitic carcinoma is transplanted to mice, administration of interferon may produce either a stimulating or an inhibiting effect on replication of carcinoma cells in the peritoneal cavity depending on the responsiveness of mice (intact or vaccinated with Newcastle disease virus) and the state of the transplanted cells ("common" or "tolerant"). Parallelism was observed in changes of the intensity of cell multiplications and indices of their enzymatic activity under the influence of exogenic interferon.

[Effect of a number of antitumor preparations on RNA- and protein-synthesizing processes and viral interferon induction in Krebs 2 ascites carcinoma cells]. / Izuchenie vliianiia riada protivoopukholevykh preparatov na RNK- i beolksinteziruiushchie protsessy i virusnuiu induktsiiu interferona v kletkakh astsitnoi kartsinomy Krebs-II.

Antitumor drugs: adenosine cyclophosphane, adenosine thiophosphamide, colchamine thiophosphamide, and tribetamide inhibited RNA biosynthesis in Krebs-II ascitic carcinoma cells and in similar concentrations they were much less inhibiting for protein-synthesizing processes (in cells and cell-free protein-synthesizing system). The drugs could inhibit interferon synthesis, possibly after virus induction, in Krebs-II ascitic carcinoma cells only in concentrations significantly inhibiting the synthesis of cellular macromolecules.

[Differences in the antiviral and antioncogenic action of interferons produced in murine peritoneal cells and in Krebs-2 ascitic carcinoma cells]. / Razlichiia v protivovirusnom i antionkogennom deistvii interferonov, poluchennykh v peritoneal'nykh kletkakh myshei i v kletkakh astsitnoi kartsinomy Krebs-2.

Comparisons of native preparation of mouse interferons, "macrophage" and "Krebs" revealed some differences, Thus, the minimal time necessary for the development of resistance to vesicular stomatitis virus (VSV) in L cells treated with "macrophage" and "Krebs" interferon was 5 and 2 hours, respectively. The activity of the lysosomal enzyme of acid phosphatase was considerably higher in the cells treated with "Krebs" interferon and infected with VSV than with "macrophage" interferon. Differences in the antiviral and antioncogenic properties of fractions No. 1 and No. 5 of these interferons obtained in fractionation of native interferon preparations by the cryomethod were demonstrated. In particular, fraction No. 5 of "Krebs" interferon, in contrast to that of "macrophage" interferon, had no antioncogenic properties but did have antiviral properties. It is suggested that these differences are due to the presence in native preparations of different substances capable of exerting an effect on interferon.

[Effect of BCG on the growth of Krebs-2 carcinoma]. / O vliianii BTsZh na rost kartsinomy Krebs-2.

BCG vaccine inhibits the growth of intramuscular transplants of Krebs-2 carcinoma, when given in mixture with the tumor cells, and stimulates it in contralateral administration. When BCG and the tumor cells are injected separately in the region, drained by one and the same lymph node, no antitumor effect of the vaccine is observed. It is suggested that BCG effect on experimental tumor growth is mainly based not on the immunological mechanisms, but is the result of redistribution of cells participating in nonspecific antitumor resistance.

[Antitumor effectiveness and nephrotoxicity of oxoplatinum]. / Protivoopukholevaia éffektivnost' i nefrotoksichnost' oksoplatiny.

Studies on such transplantable murine tumors as MOPC-21 plasmacytoma and Krebs-2 carcinoma showed oxoplatinum course administration to produce necrosis in solid tumors and pronounced alterations in surviving tumor cells. Single applications of 15 or 20 mg/kg were followed by an increase in the mean survival of Krebs-2 ascites carcinoma--bearing mice by one half. Oxoplatinum--induced changes in the renal tissue ranged from moderate under continuous administration to acute renal failure after high--dose treatment. Such diuretics as diacarb, furosemide and, particularly, mannitol did not interfere with oxoplatinum activity against solid and ascites tumors but assured less pronounced structural disorders in the kidney as compared to oxoplatinum alone.

Pharmacokinetics and efficacy of i.v. and i.p. VM26 chemotherapy in mice bearing Krebs II ascitic tumors.

The pharmacokinetics and the efficacy of VM26 are studied following i.p. or i.v. administration in mice bearing Krebs II ascitic tumors. The i.p. inoculation of 30.10(6) Krebs II cells in Swiss mice leads to the formation of ascites. The effects of VM26 were dependent upon the route of administration. A 2 mg/kg i.p. single dose induces an equivalent per cent increase of median survival time than a 20 mg/kg i.v. single dose. The survival advantage of i.p. VM26 was found to be related to the pharmacologic benefit of i.p. administration. If local toxicity does not prove to be a major problem, i.p. VM26 may constitute a safe and practical mode of therapy in patients with intraabdominal tumors.