KLF4 and nasopharyngeal carcinoma: Consistent with a previous report showing that KLF4 expression is decreased in NPC tumor specimens [53,54], we found that KLF4 expression in C666.1 cells (the only authentic EBV+ NPC tumor cell line in this panel) is relatively low compared to that in the EBV-superinfected epithelial cell lines (NOKs and HONE).