IGF-1 mRNA and protein were detected in only 5 NPC cell lines, with the highest expression level of IGF-1 observed in C666 cells, which consistently harbours Epstein-Barr virus (EBV), and weaker expression of IGF-1 detected in three poorly differentiated NPC cell lines (CNE2, 5-F8, SUNE2) and well-differentiated cell lines CNE1. Here, IGF1 is linked to nasopharyngeal carcinoma.