[Multiple medication resistance of apoptosis-resistant tumoral cells].

A4 clone cells, received by CD95-mediated selection from the parental line of Jurkat T-lymphoblast human leukosis, lost their ability of apoptosis as a result of programmed cell death mechanism breakdown. The complex of their acquired phenotypic properties meets tumor progression criteria: oxidative stress resistance, active immune suppression, and low requirement for growth factors. The loss of A4 cell ability of apoptosis is accompanied by acquisition of the phenotype of multiple medication resistance to a wide spectrum of antineoplastic chemotherapeutic drugs and cytotoxins.

[Synthesis and antitumor activity of cyclopropane derivatives of betulinic and betulonic acids].

New cyclopropane derivatives of betulin were synthesized by attachment of dichlorocarbenes or dibromocarbenes to the double bond of betulin diacetate, followed by the deprotection of hydroxyl groups. The betulin cyclopropane derivative was obtained from 20,29-dihydro-20,29-dichloromethylenebetulin by treatment with lithium in tert-butanol. These compounds were converted into the corresponding derivatives of betulonic acid by oxidation with chromium trioxide. The reduction of oxo group with sodium borohydride led to the corresponding derivatives of betulinic acid. 20,29-Dihydro-20,29-dichloromethylenebetulinic acid proved to be the most cytotoxic toward human melanoma of the Colo 38 and Bro lines and human ovarian carcinoma of the CaOv line (IC50 10 microM). 20,29-Dihydro-20,29-dibromomethylenebetulinic acid inhibited the growth of the Bro melanoma cell line and the CaOv carcinoma cell line practically by 50% at a concentration of 10 microM. The other derivatives of betulinic and betulonic acids were active toward all of the three cancer cell lines at concentrations higher than 10 microM. The English version of the paper: Russian Journal of Bioorganic Chemistry, 2005, vol. 31, no. 3; see also http://www.maik.ru.

[Epimerization of hydroxyl group in the lupan series of triterpenes]. / Epimerizatsiia gidroksil'noi gruppy v triterpenakh lupanovogo riada.

Two methods of obtaining of 3 alpha-betulinic acid and related compounds from their 3 beta-epimers were studied: the reaction of bimolecular substitution and the stereoselective reduction of 3-ketoderivatives. The substitution of acyloxy by formyloxy group in 3-O-tosyllupeol or of the betulin hydroxyl by benzoyloxy group resulted only in delta 2, 3-elimination products, with none of the expected products of bimolecular substitution being found. The catalytic hydrogenation of betulonic acid over Raney nickel resulted only in reduction of the isopropenyl double bond, whereas the use of 5% Ru/C gave a 60:40 mixture of epimers of dihydrobetulinic acid. Practically the same mixture of betulinic acid epimers was obtained when reducing betulonic acid with L-Selectride. The cytotoxic activity of 3 alpha-betulinic acid increased toward melanoma Bro cells and decreased toward melanoma MS cells.

[A novel immunoregulating hexapeptide with antineoplastic effect]. / Novyi immunoreguliatornyi geksapeptid s protivoopukholevym deistviem.

A synthesized analog of myelopeptide HP-2-->M[symbol: see text]-2 (Leu-Val-Val-Tyr-Pro-Trp) caused a significant (60-80%) and prolonged inhibition of s.c. grafted tumors P388, Ca-755, B-16 and sarcoma 180 in isogenic mice but did not affect the growth of tumor B-16 in nude mice. Nor did it influence proliferative activity or viability of cultured human tumor cells. The best results were obtained with s.c. injections of 0.5-2 mg/kg HP-2-->M[symbol: see text]-2, twice or trice a day, at 96 hr intervals. No symptoms of severe poisoning were registered at doses of HP-2-->M[symbol: see text]-2 100 times the therapeutic one. A pharmacokinetic study in mice revealed prolonged circulation of HP-2-->M[symbol: see text]-2 in blood and a high affinity for the bone marrow (t 1/2 (130.1 hr and 431.6 hr, respectively). HP-2-->M[symbol: see text]-2 restored in vitro the ascites P388-suppressed cytotoxicity of murine T-lymphocytes. HP-2-->M[symbol: see text]-2 is regarded as a candidate for clinical studies of its potential of immunocorrection in cancer patients suffering T-lymphocyte immunity disturbances.

Antiproliferative effect of complexes of platinum (II) with plasmanyl-(N-acyl)-ethanolamine, an inhibitor of protein kinase C.

Antiproliferative activities of combinations of semisynthetic plasmanyl-(N-acyl)-ethanolamine [PNAE(s)], an inhibitor of protein kinase C, with two antitumor complexes of platinum (II) [cisplatin and ammine(cyclopentylamine)-S-(-)-malatoplatinum (cycloplatam)] were investigated. The exposure of human melanoma BRO cells in culture simultaneously with cisplatin (1-10 microM) and PNAE(s) (100 microM-1 mM) in a molar ratio of 1/100 for 24 h induced a considerable decrease in the ability of these cells to incorporate [3H]thymidine into DNA. A considerable antiproliferative synergism of these agents was observed. The effect of cycloplatam/PNAE(s) combination in similar experiments was significantly different from cisplatin/PNAE(s), i.e. interaction of these agents was complex and synergism was not found.

Synergistic antiproliferative effect of cis-diammine-dichloroplatinum (II) and a new anticancer agent, plasmanyl-(N-acyl)-ethanolamine, an inhibitor of protein kinase C.

The action of a new anticancer agent, the semisynthetic alkyl-phospholipid plasmanyl-(N-acyl)-ethanolamine (sPNAE), namely 1-O-octadecyl-2-oleoyl-sn-glycero-3-phospho-(N-palmitoyl)-ethanolamine, on protein kinase C (PKC) was investigated, and it was found to inhibit in a dose-dependent manner PKC isolated from mouse brain. The inhibition was competitive with respect to phosphatidylserine (K(i) = 20 microM). Lyso-PNAE, a possible cell metabolite of sPNAE, also inhibited PKC. A two-site model was used to calculate the binding affinity and the number of binding sites for phorbol ester in a culture of human melanoma BRO cells. The values of Kd, the dissociation constant, were K'd = 0.5 nM and K"d = 72 nM, whereas the values of Bmax, the number of binding sites, were B'max = 4.6 x 10(4) sites cell-1, and B"max = 2.9 x 10(5) sites cell-1. sPNAE was able to reduce the affinity of BRO cells for phorbol ester with almost no changes in the number of binding sites: K'd = 1.6 nM, K"d = 557 nM, and B'max = 4 x 10(4), B"max = 1.9 x 10(5). These data suggest that sPNAE may inhibit PKC in intact cells. Since various inhibitors of PKC may enhance the antiproliferative activity of cis-diamminedichloroplatinum(II) (cis-DDP), we investigated the effect of the combination of sPNAE and cis-DDP on the proliferation of BRO cells. sPNAE synergistically enhanced the antiproliferative activity of cis-DDP.

Preferential replication of murine xenotropic type-C virus in human lymphosarcoma-derived cell lines.

Murine xenotropic virus, designated 698/X, was recovered by implantation of human lymphosarcoma-derived cells U-698M into nude mice of Giovanella's colony. The budded and extracellular particles revealed typical type-C morphology, the latter possessing reverse transcriptase (RT) activity and exhibiting a buoyant density 1.17 g/ml in sucrose gradient. In competitive radioimmunoassay using iodinated p30 of Rauscher MuLV, the 698X viral concentrate and cell extracts of both implanted lymphosarcoma cells (U-698M-N-1 and U-715M-N-1) were as effective as Gross MuLV, thus indicating the murine origin of the virus. The propagation of the 698/X virus in five human, four mouse (permissive for N- and B-tropic MuLV), two rat and one bovine cell lines was followed by RT, XC syncytia assays and EM investigations. The replication of the 698/X virus seems to be restricted mainly to both human lymphosarcoma-derived cell lines U-698M and U-715M. The new recovery of the virus from the nude mouse by implantation of U-175M cells has asserted its high tropism to human lymphosarcoma cells and its murine origin. The comparative response of mouse, rabbit and rat cells exposed to both NZB and 698/X xenotropic murine viruses exhibited host range differences between these viruses. The rabbit SIRC and rat embryonic cells REC were fully permissive for the murine xenotropic NZB virus, while low viral production was detected by RT assay only in 698/X virus infected SIRC cells.

Radioimmunoassay of type D oncovirus from continuous J-96 cells.

Radioimmunoassay of J-96 virus and an extract of J-96 cells in the homologous and heterologous systems aimed at detecting antigenic determinants of p25 of Mason-Pfizer virus, as well as group-specific and interspecies antigenic determinants p30 of Rauscher leukaemia virus demonstrated that (1) J-96 virus contains a major internal protein immunologically identical with p25 protein of Mason-Pfizer virus based on the antigenic determinants detectable by the radioimmunoassay used; and (2) no interspecies antigenic determinants characteristic of the major internal protein of mammalian type C viruses were detectable in the J-96 virus or the J-96 cell extract.