LMP1 promotes the interactions of heterodimeric NF-κB (p52/p65) and heterodimeric AP-1 (c-Jun/c-Fos) transcription factors with the human iEκ enhancer region are important for the upregulation of kappa light chain in LMP1-positive nasopharyngeal carcinoma cells. This evidence concerns the gene FOSB and nasopharyngeal carcinoma.