A high molecular weight cytotoxic lymphokine in supernatants of lymphokine-activated killer cells cross-reacts with transforming growth factor beta

Both neurotoxin II from venom of Naja naja oxiana and its endogenous analogue induce apoptosis in tumor cells

Both neurotoxin II (NT II from venom of Naja naja oxiana) and 20-30 kDa proteins partially purified from pig brain (NTlm) cross-reacting with antibodies to NT II were cytotoxic for L929 and K562 tumor cells at concentrations of 10(-6)-10(-8) M. Modification of Cys residues significantly reduced cytotoxicity of NT II. Both NT2 and NTlm induced apoptosis in L929 and K562 cells.

Time-dependent changes of LAK cell phenotypes correlate with the secretion of different cytotoxic proteins

Human lymphokine-activated killer (LAK) cells were generated from peripheral blood lymphocytes (PBL) of normal volunteers by interleukin-2 (IL-2) stimulation for 1-8 days. During the first 3 days the surface marker CD16 characteristic for natural killer (NK) cells was expressed and later the CD3 marker characteristic for cytotoxic T cells became predominant. The conditioned media of LAK cells collected after interaction of LAK cells with K562 target cells was chromatographically separated into two cytotoxic fractions: F1 and F2. It was demonstrated that fraction F1 contained cytotoxic proteins having molecular weights of 30 and 40 kDa, and fraction F2 contained cytotoxic proteins having molecular weights of 22, 38 and 75 kDa. The presence of the proteins in each of these two fractions correlated with the phenotype changes of LAK cells: the F2 cytotoxic proteins were characteristic for NK-like cells, and the F1 proteins for cytotoxic T-lymphocyte (CTL)-like phenotypes.

LAK cells release a novel form of directly acting TGF beta, tightly bound to a high molecular weight carrier(s)

We showed in previous work that LAK cell supernatants contain a large molecular weight factor with toxic activity for A375 melanoma and other cell lines. The factor, Fr1, was identified tentatively as TGF beta-related, since its activity was abolished by anti-TGF beta serum. This relatedness is further confirmed in the present work, which demonstrates that, like TGF beta, Fr1 stimulates the release and deposition of fibronectin and induces morphological changes indistinguishable from those induced by TGF beta. The TGF beta derived from LAK cells, although associated with a large carrier molecule, is directly acting and does not dissociate from its carrier following gel filtration in acetic acid. Its carrier is different from alpha-2 macroglobulin. SDS-PAGE and immunoblotting showed that FR1 contains TGF beta complexed with large molecules (150 and > 200 kDa), which dissociate in reduced gels to molecules of 60-67 kDa. We interpret these data as showing that TGF beta secreted by LAK cells is, presumably, covalently linked to monomeric carrier molecules of approximately 60 kDa, which, in turn, are S-S bonded to form multimeric molecules of 150 kDa and > 200 kDa.

Degenerative changes in the A375 melanoma line induced by transforming growth factor beta 1

A375 human melanoma cell cultures grown in the presence of TGF beta contained greatly reduced cell numbers and exhibited drastic alterations in cell morphology compared to the control cultures. Preincubation of the cells with the cytokine for only 18 h was sufficient to induce these changes irreversibly. Examination of TGF beta-treated cells in the electron microscope revealed large numbers of lipid-filled vacuoles in the cytoplasm, greatly contracted nuclei and some loss of the otherwise abundant microvilli. Thus TGF beta may have a direct toxic effect on the A375 melanoma cells.