INHIBITORS OF BOTH NUCLEAR FACTOR-KAPPA-BETA AND ACTIVATOR PROTEIN-1 ACTIVATION BLOCK THE NEOPLASTIC TRANSFORMATION RESPONSE

Cross-coupling of active protein-1 (AP-1) and nuclear factor (NF)-kapp a B has been reported. In the present study, we investigated the possi bility that both of these two transcription factors might contribute t o the process of tumor promoter-induced transformation. To establish a stable reporter cell system, two reporter genes were stably transfect ed into a JB6 mouse tumor promotion-sensitive (P+) cell line: a lucife rase reporter controlled by a collagenase AP-1 sequence and a chloramp henicol acetyltransferase reporter controlled by an interleukin 6 NF-k appa B sequence. This double-reporter cell line maintained the phenoty pe of tumor promotion sensitivity and was able to report basal or indu ced AP-1 and NF-kappa B transactivation. The cytokine tumor promoter t umor necrosis factor (TNF)-alpha transactivated NF-kappa B and AP-1 fo r both DNA binding and transcriptional activity, Pyrrolidine dithiocar bamate, an antioxidant that acts as an NF-kappa B inhibitor, efficient ly inhibited 12-O-tetradecanoylphorbol-13-acetate (TPA) or TNF-alpha i nduced NF-kappa B as well as AP-1 transactivation and cell transformat ion, suggesting dependency of transformation on both transcription fac tors, The AP-1 transrepressing-retinoid SR11302 transrepressed AP-1 an d cell transformation when these were TPA induced but not when TNF-alp ha induced, indicating different signaling pathways for TNF-alpha and TPA, Supershift electrophoresis mobility shift assay revealed that Jun B and c-Jun were absent from the AP-1/DNA complex following TNF-alpha but present following TPA treatment. Together, these results suggest that both AP-1 and NF-kappa B activation may be required for transform ation whether induced by TPA or by TNF, and the differential sensitivi ty of TPA and TNF-alpha-induced transformation to inhibition by a reti noid might be explained by differences in the composition of the DNA-b ound AP-1 complexes.