No abstract

The use of lymphokine-activated killer (LAK) cell therapy in delayed treatment requires the use of cryopreserved effector cells. The purpose of this study was to determine the optimal cryopreservation protocol for the maintenance of cytotoxic activity in mononuclear cells (MNCs). MNCs were cryopreserved with dimethyl sulfoxide or 1,2-propanediol before and after 3 days of culture with recombinant interleukin 2. The effects of cryopreservation on cell recovery, LAK cell and natural killer (NK) cell cytotoxic activities, and surface antigen markers were studied. Recovery of nonactivated MNCs was higher with 1,2-propanediol than with dimethyl sulfoxide (p < 0.05). Cytotoxic activities, measured with a 51Cr release assay, significantly decreased after thawing, on both activated cells (76.3%; range, 35.8-92.2%) and fresh cells (54.6%; range, 17.5-75.4%). A 6-day kinetic test was used to compare the cytotoxic activity of cryopreserved and fresh cells. The results showed different patterns for NK cells (cryopreserved cells had lower levels of activity than fresh cells) and LAK cells (cryopreserved cells had higher levels of activity than fresh cells). Phenotype changes of effector cells in culture, with and without cryopreservation, were monitored by flow cytometry using monoclonal antibodies. These results were compared with changes in the cytotoxicity of cells with and without cryopreservation. After thawing, there was a decrease in MNCs expressing CD14 and CD56. Recovery of the CD56 marker correlates with increased cytotoxic activity. Despite some loss of NK cell activity, it is concluded that MNCs may be successfully cryopreserved before their use in immunotherapeutic treatment.

The effect of incubations with anti‐sense phosphorothioate oligonucleotides directed toward sequences of dihydrofolate reductase (DHFR) RNA has been tested on Chinese hamster ovary cells. The selected targets were the 5'‐untranslated region, the translational start, the splice sites and branch point of intron 1 and polyadenylation regions 1 and 3 of the DHFR RNA. To introduce the oligonucleotides, the cationic liposome DOTAP was used. The oligonucleotides most effective at causing cytotoxicity were ATNL and DTNL, both directed toward the translation‐start site, at a range of concentrations between 1 and 4 μM. The minimum time for the oligonucleotide to exert its full cytotoxic effect was 3 days. Excess of oligonucleotide diminished the cytotoxic effect. Oligonucleotide uptake was monitored by the incorporation of [32P]‐ or fluorescein‐labeled oligonucleotide and was found to depend on liposome and oligonucleotide concentrations and duration of incubation. Formation of in vitro complexes between the oligonucleotide and the liposome was also studied. Cytotoxicity was observed when the oligonucleotide was incubated with cell lines containing either the endogenous gene or co‐transfected DHFR minigenes. Cell incubation with ATNL caused a time‐dependent decrease in the levels of DHFR mRNA and enzymatic activity. Moreover, a cell line bearing amplification at the dhfr locus was equally affected by the action of ATNL. Human hepatoma cells were also affected by treatment with the counterpart of ATNL in the human DHFR mRNA sequence. Our results set the basis for a possible cancer therapy with anti‐sense oligonucleotides using DHFR as the target. Int. J. Cancer 81:785–792, 1999. © 1999 Wiley‐Liss, Inc.