The development of human tumor-cell resistance to TNF-alpha does not confer resistance to cytokine-induced cellular cytotoxic mechanisms.
We have derived a TNF-alpha-resistant clone (RA-I) from the parental TNF-sensitive human breast-adenocarcinoma cell line (MCF-7). The acquisition of TNF-resistance was not associated with endogenous TNF production or with differential levels of TNF receptors since both MCF-7 and RA-I display comparable TNF-receptor expression. We have investigated the relationship between acquisition of resistance to TNF and susceptibility to lysis by cytokine-activated effectors. Experiments were performed using human peripheral-blood monocytes stimulated with IL-2, IFN or GM-CSF, and lymphokine-activated killer cells as effector cytotoxic cells. Our data indicate that both TNF-resistant (RA-I) and TNF-sensitive (MCF-7) cells were killed by IL-2-activated monocytes. Incubation of monocytes with IFN also resulted in the activation of their tumoricidal activity against MCF-7 and RA-I. When stimulated monocytes were pre-incubated in the presence of a TNF-specific neutralizing monoclonal antibody, prior to co-culture with target cells, no effect on their lytic capacity was observed. Thus, the monocyte killing does not appear to involve the membrane form of TNF. These observations suggest that, in our experimental system, IL-2 and IFN are able to induce non-TNF-mediated mechanisms of cytotoxicity by monocytes. Experiments performed using GM-CSF and LPS for monocyte stimulation indicate that, although both reagents were efficient in inducing the membrane form of TNF on monocytes, they did not enhance the cell-killing capacity towards MCF-7 and RA-I targets. Furthermore, using IL-2-stimulated LGL as effector cells, we show in this study that the TNF-resistant clone RA-I was as sensitive as MCF-7 to human LAK cells.
Zyad
A
A
Laboratoire d'Immunologie URA 1156 CNRS, Institut Gustave-Roussy, Villejuif, France.
Branellec
D
D
Mahé
Y
Y
Tursz
T
T
Chouaib
S
S
D000230:Adenocarcinoma / Q000276:immunology*; D015152:Blotting, Northern; D001943:Breast Neoplasms / Q000276:immunology*; D003602:Cytotoxicity, Immunologic; D005260:Female; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D006801:Humans; D007371:Interferon-gamma / Q000502:physiology; D007376:Interleukin-2 / Q000502:physiology; D009000:Monocytes / Q000502:physiology*; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000502:physiology*
D007376:Interleukin-2; D014409:Tumor Necrosis Factor-alpha; D007371:Interferon-gamma