Effect of nuclear factor kappaB inhibition on tumor cell sensitivity to natural killer-mediated cytolytic function.

Inhibition of the transcription factor NF-kappaB has been reported to increase cell sensitivity to TNF and some cytotoxic drugs. We investigated the effect of NK-kappaB inhibition on the susceptibility of tumor cells to freshly isolated, nonactivated, human NK cells and to a TCRgamma/delta T cell clone displaying an MHC-unrestricted "NK-like" lysis. Using electrophoretic mobility shift assay, we first demonstrated that NF-kappaB/DNA binding activity was induced in target cells following coculture with NK cells or TCRgamma/delta T cell clone. To investigate the effect of target cell NF-kappaB inhibition on NK-mediated lysis, we blocked NF-kappaB translocation by introducing a human cDNA coding for a mutated IkappaB-alpha. Interestingly, our results indicated that inhibition of NF-kappaB did not induce any increase in either granzyme-dependent non-MHC-restricted cytotoxicity mediated by fresh non-stimulated NK cells and by TCR gamma/delta T cell clone or in CD95-mediated lysis. These results emphasize that NF-kappaB expressed in target cells does not play a role in the molecular process related to the control of target cell susceptibility to NK-mediated lysis and suggest that the NF-kappaB pathway is not a general mechanism for controlling the cytotoxic response.