Augmentation of in vitro cytotoxicity and in vivo tumor-inhibition by combined use of lymphotoxin-containing supernatants and antitumor drugs

Augmentation of the radiation-induced antiproliferative effect in combined use of a derivative of nitrosourea, ACNU, with recombinant human tumor necrosis factor

The effect of combined use of a derivative of nitrosourea, ACNU, with recombinant human tumor necrosis factor (rhTNF) on the radiation-induced antiproliferative effect was examined using Meth A tumor cells. The radiation-induced antiproliferative effect was slightly augmented by the simultaneous addition of ACNU at 10 micrograms/ml in 5 Gy and 15 Gy irradiated groups. The antiproliferative effect was augmented in parallel with the radiation dose by the addition of rhTNF. Further augmentation of the proliferation inhibition was observed when both of ACNU (10 micrograms/ml) and 10 U/ml of rhTNF were added in combination with irradiation. Similar augmentation was observed when the target cells were treated with ACNU prior to irradiation and the addition of rhTNF.

Augmented anti-proliferative effect in combined use of human lymphotoxin with a nitrosourea derivative, ACNU, and the involvement of glutathione redox cycle

The cytotoxic or cytostatic effect of the combined use of human lymphotoxin (LT) with 1-(4-amino-2-methyl-5-pyrimidinyl)methyl-3-(2-chloroethyl)-3- nitrosourea hydrochloride (ACNU) on L cells or Meth A tumor cells was studied. Simultaneous addition of LT derived from a human lymphoid cell line with ACNU (200 or 500 micrograms/ml) significantly augmented the cytotoxic effect. Similar augmented inhibition was obtained when LT was added to ACNU-treated L cells. The pre-treatment of Meth A tumor cells with ACNU (25 or 50 micrograms/ml) augmented recombinant human LT-mediated cytostasis. However, the addition of glutathione (1.0 mg/ml) to ACNU-treated Meth A tumor cells significantly nullified the augmented anti-proliferative effect of LT (10 U/ml). These results suggest that augmentation of the anti-proliferative effect on tumor cells could be induced through the combined use of LT with ACNU by lowering the intracellular level of glutathione.

Induction, by adriamycin and mitomycin C, of modifications in lipid composition, size distribution, membrane fluidity and permeability of cultured RDM4 lymphoma cells

Adriamycin and mitomycin C were previously found to modulate the sensitivity of lymphoma cells to lysis by certain effectors of immunity and this modulation was dependent on drug concentration. In the present studies, RDM4 lymphoma cells were treated with different concentrations of the two drugs for 24 h in culture. These treatments resulted in changes in the lipid composition, membrane fluidity, cell size distribution, and permeability to 51CrO4, Trypan blue, Acridine orange and trimethylaminodiphenylhexatriene (TMA-DPH) of the cells. Changes in some of these parameters, as a function of drug concentration, resulted in dose-response curves which were bell-like shaped, hence paradoxical similarities between non-drug-treated cells and cells treated with higher drug concentrations were observed.

Drug-concentration dependent sensitivity to lysis by antibody and complement, of adriamycin- or mitomycin-treated murine lymphoma cells

Murine lymphoma cells (RDM4) were pretreated in culture, with Adriamycin (ADM) and with Mitomycin C (Mit C), at different concentrations, for 20 h and carefully washed. In a first series of experiments, they were labelled with 51Cr and used as target to the lytic action of alloantiserum and complement (Ab + c), as appraised by the specific 51Cr release test. It was found that exposures of the prospective target cells to high drug concentrations (e.g. 32 micrograms/ml of ADM or 20 micrograms/ml of Mit C) enhanced their susceptibility to Ab + c killing, whereas exposures to low concentrations (i.e. 0.1 microgram/ml of ADM, or 1 microgram/ml of Mit C) protected them from Ab + c mediated lysis. In a second experimental series, similarly treated RDM4 were pulsed with 3H-TdR after their exposure to Ab + c. In this case, the cytotoxic effect was appraised as "inhibition" of isotope incorporation. Using this second criterion, the protective action of pretreatment with low drug concentrations was confirmed, and was particularly clearcut in the case of ADM. The protective effect of pretreatment with low concentration of ADM (0.1 microgram) was also confirmed in vivo, with the "Winn assay".

Enhancement of murine lymphoma cell lysability by CTL and by LAK cells, after treatments with mitomycin C and with adriamycin

Murine lymphoma cells (RDM4) were treated, in culture, with adriamycin (ADM) and with mitomycin C (Mit C) at various concentrations for 20 h. They were then used as 51Cr-labelled target cells and tested for their sensitivity to the killing action both of specifically allosensitized cytotoxic T lymphocytes (CTL) and of lymphokine-activated killer (LAK) cells. They were also used as "cold target" inhibitors, in cytotoxicity assays involving CTL or LAK and 51Cr-labelled target cells. The results showed that treatments with different concentrations of Mit C enhanced the sensitivity of RDM4 cells to the killing actions of both CTL and LAK cells. ADM slightly enhanced sensitivity to the killing action by CTL, but to a much lesser extent than Mit C did. However, ADM proved to be almost as efficient as Mit C in its sensitizing action, in the case of lysis by LAK cells. Treatments with both drugs did not seem to modify the capacity of RDM4 cells to act as "cold target competitors" in cytotoxicity assays involving CTL killers, but did so in experiments involving the lytic action exerted by LAK cells.

Potential use of human interleukin 2 as an adjunct for the therapy of neoplasia, immunodeficiency and infectious disease

Experimental and clinical systems have been developed to analyze both the in vitro and in vivo effects of highly purified interleukin 2 (IL2) as a potential therapeutic adjunct for neoplasia, immunodeficiency and infectious disease. Animal models, clinical in vitro studies, as well as preliminary clinical trials of IL2 in vivo show that this lymphokine may provide a necessary signal for the activation of thymus-derived T cells in immunologically-compromised hosts.