REL and neoplasm: Nuclear factor κB (NF-κB) plays an important role in the regulation of gene transcription related to inflammation, cell proliferation, differentiation and apoptosis, immune response, and tumor formation; the human NF-κB family consists of five members: P50/P105, p52/P100, p65/RELA, RELB, and c-Rel, which are encoded by NF-κB1, NF-κB2, RELA, RELB, and REL genes [27].