REL and cancer: Filtering for cancer-associated transcription factors,27 we identified 18 genes (Figure 1b); 5 of which encoded Rel-like domain-containing proteins forming homo- or heterodimeric NF-κB complexes and inducing NF-κB regulator genes through negative feedback regulation.28, 29 Another seven transcription factors were co-expressed with all the four NF-κB-negative regulators (Figure 1b), suggesting a role in their transcriptional regulation.