However, we found normal expression levels of TRAF3 in N4bp1−/− cells and normal TNF and IL-6 responses by N4bp1−/− macrophages to LPS and poly(I:C), raising the possibility that N4BP1 may fulfill distinct functions in macrophages vs. transformed neural cells, or that the effect of N4BP1 deficiency on NF-κB signaling in neuroblastoma cells may be independent of TRAF3. This evidence concerns the gene NFKB1 and neuroblastoma.