Inhibition of nasopharyngeal carcinoma growth by RTA‐expressing baculovirus vectors containing oriP

Abstract Background Nasopharyngeal carcinoma (NPC) is closely associated with latent Epstein–Barr virus (EBV) infection. Activation of latent EBV into lytic replication by introducing viral lytic gene BRLF1 (RTA) has been shown to be a potential approach to suppress the growth of EBV‐associated NPC tumor. Methods The baculovirus vectors with RTA expression cassette (BV‐R), RTA and the EBV latent replication origin ( OriP , BV‐RO), or RTA, OriP and EBNA‐1 gene (BV‐ROE‐CMV), were constructed and examined for their ability to mediate RTA expression, initiate lytic replication and induce cell death in EBV‐positive cell lines Hone1‐EBV, HK1‐EBV and C666‐1 in vitro . Their effect to inhibit the growth of EBV‐positive NPC tumors was also evaluated in nude mice. Results The baculovirus vectors BV‐RO and BV‐ROE‐CMV mediated efficient expression of RTA in EBV‐positive NPC cells. Lytic EBV replication and cell death were observed in these infected cells. Both vectors also significantly inhibited the growth of EBV‐positive NPC tumor in nude mice. EBV early lytic gene expression and tumor cell death were observed in these treated tumors. Conclusions The presence of OriP improved the performance of the RTA‐expressing baculovirus vectors to induce EBV lytic replication and cell death in vitro , and suppress the growth of EBV positive NPC tumors in vivo . By confining RTA and EBNA‐1 expression to EBV‐positive cells, BV‐RO is expected to be a better candidate in application than BV‐ROE‐CMV in the long term. Copyright © 2008 John Wiley & Sons, Ltd.