IGF1 and nasopharyngeal carcinoma: The EBV‐infected gastric cancer cell line (NUGC‐3) and EBV‐positive NPC cell line showed increased IGF‐1 mRNA and secreted IGF‐1 levels compared to parental cell lines, which suggest that IGF‐1 mediates cell proliferation.17, 24 In our results, IGF‐1 mRNA levels did not increase, although secreted IGF‐1 levels increased in AGS‐EBV cells (Figure 1C).