IGF1 and nasopharyngeal carcinoma: However, increasing levels of IGF-1 have not been associated with EA or VCA-titre levels in NPC patients in our data, although the EBV-positive C666 cell lines were characterized by higher IGF-1 expression, which is in line with Iwakiri’s findings regarding EBV-positive NPC cell lines [15], suggesting that the circulating levels of IGF-1 are inconsistent with IGF-1 expression after EBV infection in vitro.