The difference in tumorigenicity between Epstein-Barr virus (EBV) genome-positive and genome-negative epithelial hybrid cell lines derived from the human nasopharynx.

An epithelial/hybrid cell line was previously established (A2L/AH) by the fusion of 8-azaguanine-resistant epithelial cells (Ad-AH) with Epstein-Barr virus (EBV)-transformed lymphoblastoid cells (A2L), as a nasopharyngeal carcinoma (NPC) model cell line in vitro. However, the A2L/AH cells were nontumorigenic in nude mice during early passage levels. In this study, an EBV genome-negative clone and two EBV genome-positive clones of the A2L/AH cells have been successfully cloned. We have continued to culture these three clones, as it is possible that EBV may disturb mechanisms that regulate tumorigenicity when cells are grown in vitro for long periods of time. Two EBV genome-positive A2L/AH clones have become tumorigenic in nude mice after long periods in culture, whereas EBV genome-negative A2L/AH cells were nontumorigenic after the same period of time. The data suggest that EBV may be associated with tumorigenicity in nude mice, at least in part.