In an article published in Cancer ahead of print on June 30, 2011, Wong et al report the distinct presence of several viral microRNAs encoded by the Epstein-Barr virus (EBV) genome in the serum from patients bearing EBV-associated nasopharyngeal carcinomas (NPCs).1 These findings open exciting perspectives for use of viral microRNAs as new tools for early NPC diagnosis, prognosis assessment, and treatment monitoring. The report by Wong et al is in part convergent with our previously published data about the detection of the EBV microRNA BART7 in plasma samples from patients with NPC.2 However, there are differences.
In contrast to Wong et al, we have observed a low but significant level of BART7 amplification from non-NPC donor samples. The primers used for reverse transcription and polymerase chain reaction were identical in both studies, but 1 obvious difference in our protocol was that RNA was extracted from plasma instead of from serum samples. We are curious to know whether, according to the authors, RNA extraction from serum samples is a better option to increase specific detection of circulating microRNA-BARTs among patients with NPC. Another potential factor of inconsistency is the use of a preamplification step after retrotranscription of RNAs. Wong et al refer to a protocol described by Kroh et al that mentions this preamplification procedure as optional.3 In our own study, we have skipped this step; however, it would be interesting to know explicitly whether or not it has been performed by Wong et al.