Epstein‐Barr Virus‐encoded Latent Membrane Protein 1 Co‐expresses with Epidermal Growth Factor Receptor in Nasopharyngeal Carcinoma

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Abstract
Latent membrane protein 1 (LMP‐1) is the only Epstein‐Barr virus (EBV)‐encoded oncogenic protein that has been detected in nasopharyngeal carcinoma (NPC), a cancer that is closely associated with EBV. Previous in‐vitro studies have demonstrated that LMP‐1 can upregulate epidermal growth factor receptor (EGFR) in epithelial cells. It was not established whether this cellular effect exists in NPC. To assess the association between LMP‐1 and EGFR in NPC tissues, 60 NPC specimens were examined by immunohistochemistry using anti‐LMP‐1 antibody (CS 1–4) and anti‐EGFR antibodies (EGFR 1, EGFR 1005). The results revealed that 41 (68.3%) specimens were immunopositive for LMP‐1 and 44 (73.3%) specimens over‐expressed EGFR. Morphologically, the expressions of LMP‐1 and EGFR were homogeneously distributed in the tumor nests. In addition, the correlation between LMP‐1 and EGFR was statistically significant (P<0.001, χ2 test, d.f.=1). To elucidate further the correlation between LMP‐1 and EGFR in vivo and in situ, an indirect dual immunofluorescence assay was conducted, using secondary antibodies conjugated with fluorescein isothiocyanate (FITC) or indocarbocyanine (Cy3). The results disclosed an intimate co‐expression of LMP‐1 and EGFR. In summary, the data indicate that over‐expression of EGFR is a common phenomenon in NPC, and that EGFR is co‐expressed with LMP‐1 in NPC. Thus, EBV may play a role in the tumorigenesis of NPC through the effects of LMP‐1 and EGFR.