JUNB and nasopharyngeal carcinoma: To further investigate whether there was any correlation between our reporter expression and transcription factor binding activities of the DNA fragments covering the NF-κB and AP-1 motifs from the iEκ-containing Jκ-Cκ region of human kappa gene, we performed electrophoresis mobility shift assays to examine the protein complexes formed with κNF-κB and κAP-1 motifs at NPC cell lines.