[The nuclease activity of the cell nuclei in 2 lines of murine myeloma sp2/0 differing in their resistance to cytostatics in adriamycin-induced apoptosis]. / Nukleaznaia aktivnost' iader kletok dvukh linii myshinoi mielomy sp2/0, razlichaiushchikhsia po ustoichivosti k tsitostatikam, pri indutsirovannom adriamitsinom apoptoze.

The endonuclease activity of two drug-sensitive and drug-resistant mouse myeloma cell lines during cytotoxic drug-induced apoptosis was studied. It was shown that internucleosomal fragmentation of DNA in drug-sensitive line sp2/0, undergoing apoptosis in the presence of adriamycin and colchicine, was not dependent on intracellular calcium content and was associated with activation of both Ca(2+)-Mg(2+)-dependent and acidic cation-independent endonucleases. In contrast, in multidrug resistant spEBR-5 cells, treated with the same drugs, only Ca(2+)-Mg(2+)-dependent endonuclease activity was detected. These data suggest that the differences in the pattern of endonuclease activity revealed in these cells are linked to drug-resistant phenotype and do not depend on the apoptosis-inducing agent used.

[The adaptive response of B cells to the action of cytotoxic preparations in culture. II. Immunoglobulin interaction with adriamycin and ethidium bromide]. / Adaptivnyi otvet B-kletok na deistvie tsitotoksicheskikh preparatov v kul'ture. II. Vzaimodeistvie immunoglobulinov s adriamitsinom i bromistym étidiem.

The binding of adriamycin and ethidium bromide coupled to sepharose beads with intracellular and serum immunoglobulins is detected. These drugs do not bind with Fab and Fc fragments of immunoglobulin. The binding of ethidium bromide to immunoglobulins is competitive. Possible adaptive features of this phenomenon are discussed.

[The adaptive response of B cells to the action of cytotoxic preparations in culture. III. The possible mechanism of the action of adriamycin on immunoglobin synthesis by the cells of murine myeloma]. / Adaptivnyi otvet B-kletok na deistvie tsitotoksicheskikh preparatov v kul'ture III. Vozmozhnyi mekhanizm vliianiia adriamitsina na sintez immunoglobulinov kletkami myshinoi mielomy.

A dose-dependent stimulation of immunoglobulin synthesis by Spebr-5 cells in the presence of adriamycin is shown. This effect is significantly blocked in the presence of iron-chelating agent 2,2-bipyridine. Moreover, low doses of H2O2 and heat shock also caused enhancement of immunoglobulin synthesis. These data suggest the involvement of free radical processes in the adriamycin induced stimulation of immunoglobulin synthesis.

[The adaptive response of B cells in culture to the action of cytotoxic agents. I. The stimulation of immunoglobulin synthesis and secretion by myeloma cells, hybridomas and human lymphocytes under the influence of adriamycin and ethidium bromide]. / Adaptivnyi otvet B-kletok v kul'ture na deistvie tsitotoksicheskikh agentov. I. Stimuliatsiia sinteza i sekretsii immunoglobulinov kletkami mielom, gibridomy i limfotsitami cheloveka pod vliianiem adriamitsina i bromistogo étidiia.

Effects of cytotoxic drugs, doxorubicin (adriamycin) and ethidium bromide, on immunoglobulin production have been studied in B-cell hybridomas, myelomas and human lymphocytes. Doxorubicin, and in a lesser extent ethidium bromide, are shown to enhance immunoglobulin production both in drug-resistant and drug-sensitive cell lines. Enhancement of immunoglobulin production is accompanied with that of the number of antibody forming cells and with immunoglobulin synthesis in these cells.

[Mechanisms of drug resistance of two cell lines of human chronic promyelocytic leukemia K562, resistant to DNA topoisomerase II inhibitors adriamycin and etoposide]. / Issledovanie mekhanizmov lekarstvennoi ustoichivosti dvukh kletochnykh linii khronicheskogo promieloleikoza cheloveka linii K562, rezistentnykh k ingibitoram DNK-topoizomerazy II adriamitsinu i etopozidu.

Mechanisms of drug-resistance in two K562 cell lines selected for adriamycin and etoposide resistance (K562-ADR and K562-VP16, respectively) were studied. In K562-ADR cells, overexpression of mdr 1 gene and two-fold reduction of topoisomerase II alpha mRNA content were found, while topoisomerase II beta expression remained unchanged, compared to the parental cell line. Antiapoptotic bcl-2 mRNA level was four-fold decreased in K562-ADR cells, while the expression of other members of bcl-2 family was unaffected. In K562-VP16 cells five-fold reduction of topoisomerase II alpha expression was found with the absence of mdr 1 gene overexpression. The expression of antiapoptotic bcl-2 and proapoptotic bax genes was reduced in K562-VP16 cell line, while the content of bcl-2 mRNA was increased. Cytogenetic analysis of K562-VP16 cells revealed morphological changes in their cell karyotype and susceptibility of these cells to spontaneous polyploidization. Possible effects of etoposite on mitotic control in K562-VP16 cells are discussed.

[Effect of ectopic superexperssion of the anti-apoptotic gene bcl-2 on the level and character of karyotypic instability in the CHLL V-79 RJK Chinese hamster cell line]. / Vliianie éktopicheskoi sverkhékspressii antiapoptoticheskogo gena bcl-2 na uroven' i kharakter kariotipicheskoi nestabil'nosti v kletkakh kitaiskogo khomiachka linii CHL V-79 RJK

Karyotypic destabilization in cells of Chinese hamster fibroblasts CHL V-79 RJK with ectopically overexpressed antiapoptotical human bcl-2 gene from pSFFV-bcl-2 vector has been analysed. Analysis of G-banded metaphase chromosomes from 4 clones with different levels of bcl-2 expression revealed an increased level of chromosomal instability in bcl-2-transfected cells. Besides, an increased percentage of aneu- and polyploid cells and high level of cells with different chromosomal aberrations was observed. The degree of karyotypic instability positively correlated with the level of bcl-2 expression in bcl-2-transfected cells. Cells of a clone with the highest bcl-2 expression at the 13th passage of cultivation displayed an almost 100% polyploidization and the presence of specific aberrations and a tricentric marker chromosome. Selection of cells with non-random specific chromosome changes was observed in pSFFV-bcl-2-transfected CHL V-79 RJK cells in the process of their long-term cultivation. By contrast, cells of the parental cell line, as well as the control pSFFV-neo transfectants, displayed a stable karyotype throughout the long period of cultivation. It is important that the presence of morphological markers of gene amplifications--DOO, DM, MH--was observed in bcl-2-transfected cells. These findings suggest that the overexpression of antiapoptotic human bcl-2 gene may result in destabilization of the karyotype structure in cells of Chinese hamster fibroblasts CHL V-79 RJK. The character and level of destabilization correlate with the level of ectopic overexpression of this gene.

[Pleiotropic changes in karyotype structure of Chinese hamster fibroblast cell lint CHL V-79 RJK in relation to their acquisition of resistance to etoposide, an inducer of apoptosis]. / Pleiotropnye izmeneniia struktury kariotipa fibroblastov kitaiskogo khomiachka linii CHL V-79 RJK v sviazi s priobreteniem imi ustoichivosti k étopozidu-induktory apoptoza.

Chinese hamster fibroblasts CHL V-79 RJK were subjected to multistep selection in the presence of etoposide, known as an inhibitor of topoisomerase II and inductor of apoptosis. The karyotype of cells stably resistant to etoposide was analysed at progressive stages of selection using G-type staining of metaphase chromosomes. Multiple changes in the karyotype of resistant cells were observed at an early stage of selection (0.2 mg/ml of etoposide) and included: random chromosome breaks leading to formation of new chromosome markers, high frequency of aneuploid and polyploid cells, morphological instability and extracopy of q-shoulder of chromosome 1. On advanced stages of selection we observed an increased frequency of specific minute chromosome and the appearance of chromosomes with homogeneously or differentially stained regions (HSR and DSR). These data suggest that different mechanisms may be involved in developing cellular resistance to etoposide at progressive stages of selection.

Alterations in immunoglobulin synthesis during adriamycin-induced apoptosis in mouse hybridoma cells.

Changes in the immunoglobulin synthesis in mouse hybridoma 1F7 cell line following exposure to the anticancer drug adriamycin were studied. It was shown that adriamycin in concentrations up to 0.1 microgram/ml causes dose-dependent reversible enhancement of immunoglobulin heavy gamma 2b chain synthesis, and to a lesser extent, kappa light chain synthesis. Enhancement of gamma 2b heavy chain synthesis accompanies an increase in Ig gamma 2b mRNA levels. Enhancement of DNA-binding activity of another B-cell specific protein, octamer transcription factor Oct-2 was also observed. Cell cycle analysis revealed accumulation of the ADR-treated cells in G2/M phase of cell cycle. These changes in hybridoma cells preceded the onset of internucleosomal DNA fragmentation and appearance of morphological characteristics of apoptosis. These findings suggest, that differentiation-related processes occur during the latent phase of apoptosis induced by adriamycin in mouse hybridoma cells.

[The interaction of human natural killers with target cells of the K562 line and its sublines characterized by multiple drug resistance and thermoresistance]. / Vzaimodeistvie estestvennykh killerov cheloveka s kletkami-misheniami linii K562 i ee subliniiami, kharakterizuiushchimisia mnozhestvennoi lekarstvennoi ustoichivost'iu i teploustoichivost'iu.

Target cells, K562 strain and its sublines characterized by multiple drug resistance (MDR) do not differ in their susceptibility to human natural killer cells (NK) but MDR cells are more susceptible to cytotoxic action of lymphokine-activated cells (LAC) and to NK cells in the presence of a selective agent adriamycin. Target cells death is characterized by fragmentation of nuclear DNA. It has been established that K562 thermotolerant subclone is more resistant to NK and LAC than other clones. Heat shock protein synthesis may have a protective impact in target cells death during interaction with NK and LAC cells.