1,721,216 research outputs found
In vivo or in vitro modulating effects of vincristine on the generation of allogeneic cytotoxic lymphocytes in vitro
No full textCytotoxic activity of Hypericum perforatum L. on K562 erythroleukemic cells: differential effects between methanolic extract and hypericin
No full textThe influence of a methanolic extract of Hypericum perforatum L. and of purified hypericin has been comparatively tested on the growth of a human erythroleukemic cell line (K562). After 1 h exposure to increasing concentrations (as hypericin content) of both agents in the dark, leukemic cells were grown for 24 h and 48 h. The effects on cell growth were determined by viable cell count, flow cytometry analysis and fluorescence microscopy. Our data show that purified hypericin has only a weak inhibitory effect on cell growth and no effect in inducing apoptotic cell death. In contrast, the Hypericum flower extract shows a significant concentration-dependent and long-lasting inhibition of cell growth, and induces apoptotic cell death. This work con fi rms the interesting role of Hypericum perforatum L. in cancer therapy and strongly supports the hypothesis that agents, other than hypericin, present in the total extract can impair tumor cell growth acting separately or in a combined manner
Modification of miR gene expression pattern in human colon cancer cells following exposure to 5-fluorouracil in vitro
No full textmicroRNAs (miRNAs) are small noncoding RNA molecules produced by miR genes which are able to control the expression of a large number of cellular proteins by targeting mRNAs of protein coding genes. It has been suggested that modification of miR gene expression could be an important factor in the development and maintenance of the neoplastic state. It is a] so reasonable to hypothesize that antineoplastic drugs could be able to alter miR gene expression pattern since most of them are able to interfere with nucleic acid metabolism and gene expression. here we show that 5-fluorouracil (5-FU), a classical antimetabolite largely used in the clinic, is able to change significantly the expression of several miR genes. In colon cancer cells, at a clinically relevant concentration, the drug up-regulates or down-regulates in vitro the expression of 19 and 3 miR genes, respectively, by a factor of not less than two-fold. In some instances, 5-FU up-regulates miR genes that are already over-expressed in neoplastic tissues, including, for example, miR-21 that is associated with anti-apoptotic functions characterizing malignant cells. In this case, it is possible that drug-induced miR gene dysregulation could be the expression of cellular response to the toxic effects of the agent. on the contrary, in other instances the drug influences the expression of miR genes in a direction that is opposite to that induced by neoplastic transformation. a typical example is provided by miR-200b, that is up-regulated in various tumors and down-regulated by treatment with the antimetabolite. Noteworthy, it is known that miR-200b suppresses a gene that codes for a protein tyrosine phosphatase (PTPN12) that inactivates products of oncogenes, such as c-Abl, Src or Ras. In conclusion, the present results support the hypothesis that 5-FU can alter profoundly miR gene expression pattern. This effect could be responsible, at least in part, of the multi-target pleiotropic influence manifested by the drug on malignant cells. (c) 2007 Elsevier Ltd. All rights reserved
Effect of human T lymphotropic retrovirus-I exposure on cultured human glioma cell lines
No full textFour different human tumor cell lines of glial origin have been exposed to a human T lymphotropic retrovirus (HTLV-I). All these cell lines were positive for the glial marker glial fibrillary acidic protein (GFAP). The presence of virus RNA was demonstrated by in situ hybridization using an HTLV-I, SStI-SStI viral insert as probe. Virus expression has been monitored through an indirect immunofluorescence assay using a monoclonal antibody against virus core protein p19. All the four glioma cell lines tested became positive for p19 after 2 weeks of co-cultivation and showed a clear alteration of GFAP expression
Apoptotic and clastogenic effects of methylating agents, alone or combined with poly(ADP-ribose) polymerase inhibitor, in peripheral blood lymphocytes
No full textWe recently demonstrated that mismatch repair deficient tumor cells, that are tolerant to O6-methyl guanine (O6meG) damage, are susceptible to MeOSO2(CH2)2-lexitropsin (Me-Lex) capable of inducing almost exclusively N3-methyl adenine (N3meA) adducts. Moreover, these cells can be rendered sensitive to O6methylating agents that generate low levels of N3meA (temozolomide, TZM), when used in combination with poly(ADP-ribose) polymerase (PARP) inhibitors. This is likely due to interruption of base excision repair (BER) process, that is involved in nucleotide replacement of N3meA. PARP inhibitors are also capable of enhancing the cytotoxic and clastogenic effects induced by Me-Lex. Purpose To evaluate the potential toxicity and clastogenicity in normal peripheral blood lymphocytes (PBL) of Me-Lex or TZM, as single agent or associated with PARP inhibitor. Methods and results PBL of healthy donors, untreated or activated with PHA for 3h, were exposed to graded concentrations of Me-Lex (1.5-25M) or TZM (62.5-250M), alone or combined with the PARP inhibitor 3-aminobenzamide (AB, 4mM). Cytotoxicity was evaluated at daily intervals during 72h of culture. Chromosome damage was assessed only in PHA-activated PBL at 72h. The results show that: a) when used alone, Me-Lex induced apoptosis in a dose-dependent fashion, either in non-stimulated or in PHA-activated PBL as early as 24h after treatment. Addition of AB significantly increased the percentage of apoptotic cells at all drug concentrations; b) in the case of TZM, at 24 h apoptosis was not observed either in resting or PHA-activated PBL. Only when the drug was combined with AB, a small percentage of apoptotic cells could be detected. In contrast, at 48 or 72h of culture, TZM induced apoptosis only in PHA activated PBL. This is likely the consequence of the toxicity derived from O6meG, that is known to occur after DNA replication. c) High concentrations of Me-Lex (12.5-25M) markedly reduced the mitotic index of PHA-activated cells and did not allow chromosome analysis. Me-Lex (1.5-3M) produced chromosome aberrations that were increased by addition of AB. TZM induced aberrations only at 250M and, when combined with AB, at all concentrations tested. d) MeLex (1-6M) induced sister chromatid exchanges (SCE) in a dose-dependent fashion and addition of AB significantly enhanced this effect. In the case of TZM, SCE were observed at all the concentrations tested. In the presence of AB, the number of SCE generated by TZM was significantly higher than that induced by the drug used alone or by Me-Lex ± AB. Conclusion High levels of N3meA or interruption of its repair through the use of PARP inhibitors might be toxic for effector cells of the immune system, including those mediating functions that do not require cell proliferation
Immune inhibition of allogeneic lymphoma cells in the peritoneal cavity of mice.
No full textMice were sensitized with cells of normal spleen, transplantable syngeneic lymphomas, or allogeneic lymphomas differing for alloantigens specified by the major histocompatibility complex. From three to eleven days later, the allograft reactivity of these sensitized and appropriate control mice was evaluated in the peritoneal cavity by the disappearance of injected lymphoma cells or the inhibition of DNA synthesis. For the disappearance test, target cells were labeled with [125I]-5-iodo-2'-deoxyuridine before transfer. For the inhibition test, unlabeled target cells were transferred, but these cells were subsequently exposed to the DNA precursor [125I]-5-iodo-2'-deoxyuridine. In both procedures, cells were recovered from the peritoneal cavity without killing the hosts to measure retained radioactivity. Both tests were immunogenetically specific in detecting secondary allograft reactions, but the disappearance test was less sensitive. By inhibition of DNA synthesis, it was possible to detect primary and secondary reactions, the latter three to eight days after sensitization. Alloantigens associated with the H-2K-Ir regions of Murine Linkage Group IX were more immunogenic than those associated with the Ss-H-2D-Tla regions in eliciting antilymphoma reactions, and female mice responded better than males. It was concluded that the peritoneal inhibition test is sensitive enough to monitor transplantation immunity in vivo and could be applied to animals bearing tumors in sites other than the peritoneum and undergoing chemotherap
Augmentation of natural killer activity by pyran copolymer in mice.
No full textTreatment of older mice with pyran copolymer, a known interferon-inducer, was found to result in a rapid boosting of cell-mediated cytolytic activity against YAC-1 tumor target cells. The effector cells were characterized as being non-adherent and were presumed to be natural killer (NK) cells. Augmentation occurred in various lymphoid organs and was detectable 2-3 days after drug treatment. Differences in the levels of boosted activity among the lymphoid organs resulted when the route of administration was varied. The degree of augmentation was largely independent of the dose of pyran, but did vary among different strains of mice. Augmentation, moreover, was followed by a rapid decline by 5-7 days
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