Relationship between a novel human cytotoxin (factor 2) produced by a B cell line (Karpas 160) and phorbol-myristate-acetate-associated cytotoxicity

Isolation of a novel cytotoxic lymphokine (factor 2) from a human B-cell line (Karpas 160b) by preparative isoelectric focusing in the rotofor cell and chromatofocusing

Preparative isoelectric focusing (IEF) using a Rotofor cell was used for the isolation of a biologically active form of a novel cytotoxic lymphokine (Factor 2, F2) produced by a human B-cell line (Karpas 160b). We found that F2 either purified by DE52 or extracted from 160b cells using CHAPS, after adding octyl glucoside to 0.05%, could be electrofocused in the Rotofor cell without the addition of carrier ampholytes. Better recovery and separation were also achieved in the presence of 0.5% CHAPS, 3M urea. We compared the fractionation of F2 by chromatofocusing and IEF in Rotofor. Our results also showed that F2 was separable from tumor necrosis factor and phorbol myristate acetate-associated cytotoxicity by one step IEF in Rotofor. F2 purified by DE52, S-300 and Mono Q was further purified by IEF in Rotofor.

Multiparameter flow cytometric analysis of a novel cytotoxin (factor 2) induced tumor cell membrane permeability

An improved twin-probe multiparameter flow cytometric technique was applied to examine a novel cytotoxin, Factor (F2), induced tumor cell permeability. Ability to retain preloaded intracellular bis-carboxyethyl carboxyfluorescein (BCECF, green fluorescence) and to exclude extracellular propidium (red fluorescence) was measured simultaneously with forward and right-angle scatter. In addition to the two expected cell populations which were stained green negative, red positive ("membrane-damaged" and "non-viable", Region 2), and green positive, red negative ("membrane intact" and "viable", Region 3), a third population was seen which fluoresced neither green nor red and displayed intermediate light scatter characteristics (Region 1). K562 cells progressed from Region 3 to Region 1, and then from Region 1 to Region 2 after treatment with F2. These results suggest that sequential changes in membrane structure lead to increased permeability, first with respect to intracellular BCECF and then in turn to extracellular propidium. Flow cytometric changes caused by F2 were detectable 10 min after treatment with 2.5 U/ml of F2, and 5 min after 10 or 40 U/ml of F2. Flow cytometric analysis showed that F2-induced tumor cell lysis and growth inhibition were accompanied by rapid alternations in tumor cell membrane permeability. Flow cytometric analysis also distinguished F2 cytotoxicity from phorbol myristate acetate (PMA) associated cytotoxicity to K562 cells and determined that F2 produced spontaneously or induced by PMA and/or ciprofloxacin had a similar ability to induce tumor cell membrane permeability change.

Production and induction of a novel cytotoxin (factor 2) by a human B-cell line

The human B-cell line, Karpas 160, was found to produce Factor 1 and 2 (F1 and F2). F1 was found to be indistinguishable from tumor necrosis factor beta (TNF-beta), while F2 appears to be a new cytotoxin. We used several stimuli alone or in combination to trigger the 160b cells, a subclone of Karpas 160, to produce higher yield of F2. The optimal culture times, concentrations of cells and a range of stimuli were studied. We found that 20-25 ng/ml of phorbol myristate acetate (PMA) effectively induced the higher production of F2. Pretreatment of the cells with sodium butyrate enhanced F2 production. Production of TNF but not F2 was inhibited when the cells were cultured with tunicamycin and PDB. When ciprofloxacin or cycloheximide was added to the medium, F2 production in the presence of PMA was amplified. When 160b cells were cocultured with K562 cells, low levels of F2 induction were observed. We found that most types of human tumor cell lines were highly susceptible to F2, but less sensitive or even resistant to TNF. In contrast, normal human cell lines were not susceptible to F2. Therefore, it appears that F2 could be a new human cytotoxin.